@article{simba_wilder_2024,
	title = {Wilder rangelands as a natural climate opportunity: {Linking} climate action to biodiversity conservation and social transformation},
	volume = {1},
	issn = {1654-7209},
	shorttitle = {Wilder rangelands as a natural climate opportunity},
	url = {https://doi.org/10.1007/s13280-023-01976-4},
	doi = {10.1007/s13280-023-01976-4},
	abstract = {Rangelands face threats from climate and land-use change, including inappropriate climate change mitigation initiatives such as tree planting in grassy ecosystems. The marginalization and impoverishment of rangeland communities and their indigenous knowledge systems, and the loss of biodiversity and ecosystem services, are additional major challenges. To address these issues, we propose the wilder rangelands integrated framework, co-developed by South African and European scientists from diverse disciplines, as an opportunity to address the climate, livelihood, and biodiversity challenges in the world’s rangelands. More specifically, we present a Theory of Change to guide the design, monitoring, and evaluation of wilder rangelands. Through this, we aim to promote rangeland restoration, where local communities collaborate with regional and international actors to co-create new rangeland use models that simultaneously mitigate the impacts of climate change, restore biodiversity, and improve both ecosystem functioning and livelihoods.},
	language = {en},
	urldate = {2024-03-27},
	journal = {Ambio},
	author = {Simba, Lavhelesani D. and te Beest, Mariska and Hawkins, Heidi-Jayne and Larson, Keith W. and Palmer, Anthony R. and Sandström, Camilla and Smart, Kathleen G. and Kerley, Graham I. H. and Cromsigt, Joris P. G. M.},
	month = jan,
	year = {2024},
	keywords = {Albedo, Biodiversity, Carbon sequestration, Methane, Natural disturbance, Nature-based solutions},
	pages = {s13280--023--01976--4},
}

Rangelands face threats from climate and land-use change, including inappropriate climate change mitigation initiatives such as tree planting in grassy ecosystems. The marginalization and impoverishment of rangeland communities and their indigenous knowledge systems, and the loss of biodiversity and ecosystem services, are additional major challenges. To address these issues, we propose the wilder rangelands integrated framework, co-developed by South African and European scientists from diverse disciplines, as an opportunity to address the climate, livelihood, and biodiversity challenges in the world’s rangelands. More specifically, we present a Theory of Change to guide the design, monitoring, and evaluation of wilder rangelands. Through this, we aim to promote rangeland restoration, where local communities collaborate with regional and international actors to co-create new rangeland use models that simultaneously mitigate the impacts of climate change, restore biodiversity, and improve both ecosystem functioning and livelihoods.

@article{van_zuijlen_frost_2024,
	title = {Frost damage measured by electrolyte leakage in subarctic bryophytes increases with climate warming},
	volume = {112},
	copyright = {© 2023 The Authors. Journal of Ecology published by John Wiley \& Sons Ltd on behalf of British Ecological Society.},
	issn = {1365-2745},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.14236},
	doi = {10.1111/1365-2745.14236},
	abstract = {Observed climate change in northern high latitudes is strongest in winter, but still relatively little is known about the effects of winter climate change on tundra ecosystems. Ongoing changes in winter climate and snow cover will change the intensity, duration and frequency of frost events. Bryophytes form a major component of northern ecosystems but their responses to winter climate changes are largely unknown. Here, we studied how changes in overall winter climate and snow regime affect frost damage in three common bryophyte taxa that differ in desiccation tolerance in a subarctic tundra ecosystem. We used a snow manipulation experiment where bryophyte cores were transplanted from just above the tree line to similar elevation (i.e. current cold climate) and lower elevation (i.e. near-future warmer climate scenario) in Abisko, Sweden. Here, we measured frost damage in shoots of Ptilidium ciliare, Hylocomium splendens and Sphagnum fuscum with the relative electrolyte leakage (REL) method, during late winter and spring in two consecutive years. We hypothesized that frost damage would be lower in a milder climate (low site) and higher under reduced snow cover and that taxa from moister habitats with assumed low desiccation tolerance would be more sensitive to lower temperature and thinner snow cover than those from drier and more exposed habitats. Contrary to our expectations, frost damage was highest at low elevation, while the effect of snow treatment differed across sites and taxa. At the high site, frost damage was reduced under snow addition in the taxon with the assumed lowest desiccation tolerance, S. fuscum. Surprisingly, frost damage increased with mean temperature in the bryophyte core of the preceding 14 days leading up to REL measurements and decreased with higher frost degree sums, that is, was highest in the milder climate at the low site. Synthesis Our results imply that climate warming in late winter and spring increases frost damage in bryophytes. Given the high abundance of bryophytes in tundra ecosystems, higher frost damage could alter the appearance and functioning of the tundra landscape, although the short and long-term effects on bryophyte fitness remain to be studied.},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {Journal of Ecology},
	author = {van Zuijlen, Kristel and Kassel, Marlene and Dorrepaal, Ellen and Lett, Signe},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2745.14236},
	keywords = {desiccation tolerance, frost sensitivity, mosses, relative electrolyte leakage (REL), snow manipulation experiment, tundra, winter ecology, ❓ Multiple DOI},
	pages = {220--232},
}

Observed climate change in northern high latitudes is strongest in winter, but still relatively little is known about the effects of winter climate change on tundra ecosystems. Ongoing changes in winter climate and snow cover will change the intensity, duration and frequency of frost events. Bryophytes form a major component of northern ecosystems but their responses to winter climate changes are largely unknown. Here, we studied how changes in overall winter climate and snow regime affect frost damage in three common bryophyte taxa that differ in desiccation tolerance in a subarctic tundra ecosystem. We used a snow manipulation experiment where bryophyte cores were transplanted from just above the tree line to similar elevation (i.e. current cold climate) and lower elevation (i.e. near-future warmer climate scenario) in Abisko, Sweden. Here, we measured frost damage in shoots of Ptilidium ciliare, Hylocomium splendens and Sphagnum fuscum with the relative electrolyte leakage (REL) method, during late winter and spring in two consecutive years. We hypothesized that frost damage would be lower in a milder climate (low site) and higher under reduced snow cover and that taxa from moister habitats with assumed low desiccation tolerance would be more sensitive to lower temperature and thinner snow cover than those from drier and more exposed habitats. Contrary to our expectations, frost damage was highest at low elevation, while the effect of snow treatment differed across sites and taxa. At the high site, frost damage was reduced under snow addition in the taxon with the assumed lowest desiccation tolerance, S. fuscum. Surprisingly, frost damage increased with mean temperature in the bryophyte core of the preceding 14 days leading up to REL measurements and decreased with higher frost degree sums, that is, was highest in the milder climate at the low site. Synthesis Our results imply that climate warming in late winter and spring increases frost damage in bryophytes. Given the high abundance of bryophytes in tundra ecosystems, higher frost damage could alter the appearance and functioning of the tundra landscape, although the short and long-term effects on bryophyte fitness remain to be studied.

@article{myrsky_higher_2024,
	title = {Higher vascular plant abundance associated with decreased ecosystem respiration after 20 years of warming in the forest–tundra ecotone},
	volume = {38},
	copyright = {© 2023 The Authors. Functional Ecology published by John Wiley \& Sons Ltd on behalf of British Ecological Society.},
	issn = {1365-2435},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.14466},
	doi = {10.1111/1365-2435.14466},
	abstract = {The on-going climate warming is promoting shrub abundance in high latitudes, but the effect of this phenomenon on ecosystem functioning is expected to depend on whether deciduous or evergreen species increase in response to warming. To explore effects of long-term warming on shrubs and further on ecosystem functioning, we analysed vegetation and ecosystem CO2 exchange after 20 years of warming in the forest–tundra ecotone in subarctic Sweden. A previous study conducted 9 years earlier had found increased evergreen Empetrum nigrum ssp. hermaphroditum in the forest and increased deciduous Betula nana in the tundra. Following current understanding, we expected continued increase in shrub abundance that would be stronger in tundra than in forest. We expected warming to increase ecosystem respiration (Re) and gross primary productivity (GPP), with a greater increase in Re in tundra due to increased deciduous shrub abundance, leading to a less negative net ecosystem exchange and reduced ecosystem C sink strength. As predicted, vascular plant abundances were higher in the warmed plots with a stronger response in tundra than in forest. However, whereas B. nana had increased in abundance since the last survey, E. hermaphroditum abundance had declined due to several moth and rodent outbreaks during the past decade. In contrast to predictions, Re was significantly lower in the warmed plots irrespective of habitat, and GPP increased marginally only in the forest. The lower Re and a higher GPP under warming in the forest together led to increased net C sink. Re was negatively associated with the total vascular plant abundance. Our results highlight the importance of disturbance regimes for vegetation responses to warming. Climate warming may promote species with both a high capacity to grow under warmer conditions and a resilience towards herbivore outbreaks. Negative correlation between Re and total vascular plant abundance further indicate that the indirect impacts of increased plants on soil microclimate may become increasingly important for ecosystem CO2 exchange in the long run, which adds to the different mechanisms that link warming and CO2 fluxes in northern ecosystems. Read the free Plain Language Summary for this article on the Journal blog.},
	language = {en},
	number = {1},
	urldate = {2024-03-26},
	journal = {Functional Ecology},
	author = {Myrsky, Eero and Mikola, Juha and Kaarlejärvi, Elina and Olofsson, Johan and Sjögersten, Sofie and Tupek, Boris and Männistö, Minna K. and Stark, Sari},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.14466},
	keywords = {CO2 exchange, arctic greening, climate change, deciduous dwarf shrubs, evergreen dwarf shrubs, moth outbreaks, ⛔ No DOI found},
	pages = {219--232},
}

The on-going climate warming is promoting shrub abundance in high latitudes, but the effect of this phenomenon on ecosystem functioning is expected to depend on whether deciduous or evergreen species increase in response to warming. To explore effects of long-term warming on shrubs and further on ecosystem functioning, we analysed vegetation and ecosystem CO2 exchange after 20 years of warming in the forest–tundra ecotone in subarctic Sweden. A previous study conducted 9 years earlier had found increased evergreen Empetrum nigrum ssp. hermaphroditum in the forest and increased deciduous Betula nana in the tundra. Following current understanding, we expected continued increase in shrub abundance that would be stronger in tundra than in forest. We expected warming to increase ecosystem respiration (Re) and gross primary productivity (GPP), with a greater increase in Re in tundra due to increased deciduous shrub abundance, leading to a less negative net ecosystem exchange and reduced ecosystem C sink strength. As predicted, vascular plant abundances were higher in the warmed plots with a stronger response in tundra than in forest. However, whereas B. nana had increased in abundance since the last survey, E. hermaphroditum abundance had declined due to several moth and rodent outbreaks during the past decade. In contrast to predictions, Re was significantly lower in the warmed plots irrespective of habitat, and GPP increased marginally only in the forest. The lower Re and a higher GPP under warming in the forest together led to increased net C sink. Re was negatively associated with the total vascular plant abundance. Our results highlight the importance of disturbance regimes for vegetation responses to warming. Climate warming may promote species with both a high capacity to grow under warmer conditions and a resilience towards herbivore outbreaks. Negative correlation between Re and total vascular plant abundance further indicate that the indirect impacts of increased plants on soil microclimate may become increasingly important for ecosystem CO2 exchange in the long run, which adds to the different mechanisms that link warming and CO2 fluxes in northern ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

@article{larsbo_quantifying_2024,
	title = {Quantifying earthworm soil ingestion from changes in vertical bulk density profiles},
	volume = {120},
	issn = {1164-5563},
	url = {https://www.sciencedirect.com/science/article/pii/S1164556323001103},
	doi = {10.1016/j.ejsobi.2023.103574},
	abstract = {Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were Aporrectodea trapezoides, Aporrectodea tuberculata, Aporrectodea rosea, Lumbricus rubellus and Lumbricus Terrestris (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.},
	urldate = {2024-03-26},
	journal = {European Journal of Soil Biology},
	author = {Larsbo, M. and Koestel, J. and Krab, E. J. and Klaminder, J.},
	month = mar,
	year = {2024},
	pages = {103574},
}

Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were Aporrectodea trapezoides, Aporrectodea tuberculata, Aporrectodea rosea, Lumbricus rubellus and Lumbricus Terrestris (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

@article{jonsson_cascading_2024,
	title = {Cascading effects of earthworm invasion increase graminoid density and rodent grazing intensities},
	volume = {105},
	copyright = {© 2023 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.},
	issn = {1939-9170},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ecy.4212},
	doi = {10.1002/ecy.4212},
	abstract = {Human-mediated dispersal of non-native earthworms can cause substantial changes to the functioning and composition of ecosystems previously earthworm-free. Some of these earthworm species have the potential to “geoengineer” soils and increase plant nitrogen (N) uptake. Yet the possible consequences of increased plant N concentrations on rodent grazing remains poorly understood. In this study, we present findings from a common garden experiment with two tundra communities, meadow (forb dominated) and heath (shrub dominated), half of them subjected to 4 years of earthworm presence (Lumbricus spp. and Aporrectodea spp.). Within four summers, our earthworm treatment changed plant community composition by increasing graminoid density by, on average, 94\% in the heath vegetation and by 49\% in the meadow. Rodent winter grazing was more intense on plants growing in soils with earthworms, an effect that coincided with higher N concentrations in plants, indicating a higher palatability. Even though earthworms reduced soil moisture, plant community productivity, as indicated by vegetation greenness (normalized difference vegetation index), was not negatively impacted. We conclude that earthworm-induced changes in plant composition and trophic interactions may fundamentally alter the functioning of tundra ecosystems.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Ecology},
	author = {Jonsson, Hanna and Olofsson, Johan and Blume-Werry, Gesche and Klaminder, Jonatan},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ecy.4212},
	keywords = {Lumbricidae, earthworms, grazing, non-native, plant community, soil moisture, tundra, ⛔ No DOI found},
	pages = {e4212},
}

Human-mediated dispersal of non-native earthworms can cause substantial changes to the functioning and composition of ecosystems previously earthworm-free. Some of these earthworm species have the potential to “geoengineer” soils and increase plant nitrogen (N) uptake. Yet the possible consequences of increased plant N concentrations on rodent grazing remains poorly understood. In this study, we present findings from a common garden experiment with two tundra communities, meadow (forb dominated) and heath (shrub dominated), half of them subjected to 4 years of earthworm presence (Lumbricus spp. and Aporrectodea spp.). Within four summers, our earthworm treatment changed plant community composition by increasing graminoid density by, on average, 94% in the heath vegetation and by 49% in the meadow. Rodent winter grazing was more intense on plants growing in soils with earthworms, an effect that coincided with higher N concentrations in plants, indicating a higher palatability. Even though earthworms reduced soil moisture, plant community productivity, as indicated by vegetation greenness (normalized difference vegetation index), was not negatively impacted. We conclude that earthworm-induced changes in plant composition and trophic interactions may fundamentally alter the functioning of tundra ecosystems.

@article{ehnvall_topography_2024,
	title = {Topography and {Time} {Shape} {Mire} {Morphometry} and {Large}-{Scale} {Mire} {Distribution} {Patterns} in the {Northern} {Boreal} {Landscape}},
	volume = {129},
	copyright = {© 2024. The Authors.},
	issn = {2169-9011},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JF007324},
	doi = {10.1029/2023JF007324},
	abstract = {Peatlands are major terrestrial soil carbon stores, and open mires in boreal landscapes hold a considerable fraction of the global peat carbon. Despite decades of study, large-scale spatiotemporal analyses of mire arrangement have been scarce, which has limited our ability to scale-up mire properties, such as carbon accumulation to the landscape level. Here, we use a land-uplift mire chronosequence in northern Sweden spanning 9,000 years to quantify controls on mire distribution patterns. Our objectives include assessing changes in the spatial arrangement of mires with land surface age, and understanding modifications by upland hydrotopography. Characterizing over 3,000 mires along a 30 km transect, we found that the time since land emergence from the sea was the dominant control over mire coverage, especially for the establishment of large mire complexes. Mires at the youngest end of the chronosequence were small with heterogenous morphometry (shape, slope, and catchment-to-mire areal ratios), while mires on the oldest surfaces were variable in size, but included larger mires with more complex shapes and smaller catchment-to-mire ratios. In general, complex topography fragmented mires by constraining the lateral expansion, resulting in a greater number of mires, but reduced total mire area regardless of landscape age. Mires in this study area occurred on slopes up to 4\%, indicating a hydrological boundary to peatland expansion under local climatic conditions. The consistency in mire responses to spatiotemporal controls illustrates how temporal limitation in peat initiation and accumulation, and topographic constraints to mire expansion together have shaped present day mire distribution patterns.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Journal of Geophysical Research: Earth Surface},
	author = {Ehnvall, B. and Ratcliffe, J. L. and Nilsson, M. B. and Öquist, M. G. and Sponseller, R. A. and Grabs, T.},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JF007324},
	keywords = {Holocene, boreal, catchment, long-term development, mire morphometry, spatiotemporal drivers},
	pages = {e2023JF007324},
}

Peatlands are major terrestrial soil carbon stores, and open mires in boreal landscapes hold a considerable fraction of the global peat carbon. Despite decades of study, large-scale spatiotemporal analyses of mire arrangement have been scarce, which has limited our ability to scale-up mire properties, such as carbon accumulation to the landscape level. Here, we use a land-uplift mire chronosequence in northern Sweden spanning 9,000 years to quantify controls on mire distribution patterns. Our objectives include assessing changes in the spatial arrangement of mires with land surface age, and understanding modifications by upland hydrotopography. Characterizing over 3,000 mires along a 30 km transect, we found that the time since land emergence from the sea was the dominant control over mire coverage, especially for the establishment of large mire complexes. Mires at the youngest end of the chronosequence were small with heterogenous morphometry (shape, slope, and catchment-to-mire areal ratios), while mires on the oldest surfaces were variable in size, but included larger mires with more complex shapes and smaller catchment-to-mire ratios. In general, complex topography fragmented mires by constraining the lateral expansion, resulting in a greater number of mires, but reduced total mire area regardless of landscape age. Mires in this study area occurred on slopes up to 4%, indicating a hydrological boundary to peatland expansion under local climatic conditions. The consistency in mire responses to spatiotemporal controls illustrates how temporal limitation in peat initiation and accumulation, and topographic constraints to mire expansion together have shaped present day mire distribution patterns.

@article{cantwell-jones_using_2024,
	title = {Using individual-based trait frequency distributions to forecast plant-pollinator network responses to environmental change},
	volume = {27},
	copyright = {Ecology Letters© 2024 The Authors. Ecology Letters published by John Wiley \& Sons Ltd.},
	issn = {1461-0248},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.14368},
	doi = {10.1111/ele.14368},
	abstract = {Determining how and why organisms interact is fundamental to understanding ecosystem responses to future environmental change. To assess the impact on plant-pollinator interactions, recent studies have examined how the effects of environmental change on individual interactions accumulate to generate species-level responses. Here, we review recent developments in using plant-pollinator networks of interacting individuals along with their functional traits, where individuals are nested within species nodes. We highlight how these individual-level, trait-based networks connect intraspecific trait variation (as frequency distributions of multiple traits) with dynamic responses within plant-pollinator communities. This approach can better explain interaction plasticity, and changes to interaction probabilities and network structure over spatiotemporal or other environmental gradients. We argue that only through appreciating such trait-based interaction plasticity can we accurately forecast the potential vulnerability of interactions to future environmental change. We follow this with general guidance on how future studies can collect and analyse high-resolution interaction and trait data, with the hope of improving predictions of future plant-pollinator network responses for targeted and effective conservation.},
	language = {en},
	number = {1},
	urldate = {2024-03-26},
	journal = {Ecology Letters},
	author = {Cantwell-Jones, Aoife and Tylianakis, Jason M. and Larson, Keith and Gill, Richard J.},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/ele.14368},
	keywords = {environmental filtering, functional traits, global change, interactions, intraspecific variation, plasticity},
	pages = {e14368},
}

Determining how and why organisms interact is fundamental to understanding ecosystem responses to future environmental change. To assess the impact on plant-pollinator interactions, recent studies have examined how the effects of environmental change on individual interactions accumulate to generate species-level responses. Here, we review recent developments in using plant-pollinator networks of interacting individuals along with their functional traits, where individuals are nested within species nodes. We highlight how these individual-level, trait-based networks connect intraspecific trait variation (as frequency distributions of multiple traits) with dynamic responses within plant-pollinator communities. This approach can better explain interaction plasticity, and changes to interaction probabilities and network structure over spatiotemporal or other environmental gradients. We argue that only through appreciating such trait-based interaction plasticity can we accurately forecast the potential vulnerability of interactions to future environmental change. We follow this with general guidance on how future studies can collect and analyse high-resolution interaction and trait data, with the hope of improving predictions of future plant-pollinator network responses for targeted and effective conservation.

@article{blume-werry_situ_2024,
	title = {In situ seasonal patterns of root auxin concentrations and meristem length in an arctic sedge},
	volume = {n/a},
	issn = {0028-646X},
	url = {https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19616},
	doi = {10.1111/nph.19616},
	abstract = {Summary Seasonal dynamics of root growth play an important role in large-scale ecosystem processes; they are largely governed by growth regulatory compounds and influenced by environmental conditions. Yet, our knowledge about physiological drivers of root growth is mostly limited to laboratory-based studies on model plant species. We sampled root tips of Eriophorum vaginatum and analyzed their auxin concentrations and meristem lengths biweekly over a growing season in situ in a subarctic peatland, both in surface soil and at the permafrost thawfront. Auxin concentrations were almost five times higher in surface than in thawfront soils and increased over the season, especially at the thawfront. Surprisingly, meristem length showed an opposite pattern and was almost double in thawfront compared with surface soils. Meristem length increased from peak to late season in the surface soils but decreased at the thawfront. Our study of in situ seasonal dynamics in root physiological parameters illustrates the potential for physiological methods to be applied in ecological studies and emphasizes the importance of in situ measurements. The strong effect of root location and the unexpected opposite patterns of meristem length and auxin concentrations likely show that auxin actively governs root growth to ensure a high potential for nutrient uptake at the thawfront.},
	number = {n/a},
	urldate = {2024-03-26},
	journal = {New Phytologist},
	author = {Blume-Werry, Gesche and Semenchuk, Philipp and Ljung, Karin and Milbau, Ann and Novak, Ondrej and Olofsson, Johan and Brunoni, Federica},
	month = feb,
	year = {2024},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Eriophorum vaginatum, auxin, meristem length, permafrost, root growth, root phenology},
	pages = {19616},
}

Summary Seasonal dynamics of root growth play an important role in large-scale ecosystem processes; they are largely governed by growth regulatory compounds and influenced by environmental conditions. Yet, our knowledge about physiological drivers of root growth is mostly limited to laboratory-based studies on model plant species. We sampled root tips of Eriophorum vaginatum and analyzed their auxin concentrations and meristem lengths biweekly over a growing season in situ in a subarctic peatland, both in surface soil and at the permafrost thawfront. Auxin concentrations were almost five times higher in surface than in thawfront soils and increased over the season, especially at the thawfront. Surprisingly, meristem length showed an opposite pattern and was almost double in thawfront compared with surface soils. Meristem length increased from peak to late season in the surface soils but decreased at the thawfront. Our study of in situ seasonal dynamics in root physiological parameters illustrates the potential for physiological methods to be applied in ecological studies and emphasizes the importance of in situ measurements. The strong effect of root location and the unexpected opposite patterns of meristem length and auxin concentrations likely show that auxin actively governs root growth to ensure a high potential for nutrient uptake at the thawfront.

@article{bergstrom_declining_2024,
	title = {Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes},
	volume = {30},
	copyright = {© 2024 The Authors. Global Change Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.17220},
	doi = {10.1111/gcb.17220},
	abstract = {Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Bergström, Ann-Kristin and Creed, Irena F. and Paltsev, Aleksey and de Wit, Heleen A. and Lau, Danny C. P. and Drakare, Stina and Vrede, Tobias and Isles, Peter D. F. and Jonsson, Anders and Geibrink, Erik and Kortelainen, Pirkko and Vuorenmaa, Jussi and Vuorio, Kristiina and Kahilainen, Kimmo K. and Hessen, Dag Olav},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.17220},
	keywords = {Daphnia, Holopedium, calanoids, calcium, cladocerans, cyclopoids, lakes, phosphorus, temperature, zooplankton community composition},
	pages = {e17220},
}

Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.

@article{leander_guiding_2024,
	title = {Guiding downstream migrating {Atlantic} salmon ({Salmo} salar) and brown trout ({Salmo} trutta) of different life stages in a large river using bubbles},
	volume = {40},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-186819},
	doi = {10.1002/rra.4209},
	abstract = {Salmonid repeat spawners are precious individuals for wild populations due to their high fecundity and previous spawning experience, making them important in environmental policy. However, repeat s ...},
	language = {eng},
	number = {1},
	urldate = {2024-03-26},
	journal = {Rivers Research and Applications: an international journal devoted to river research and management},
	author = {Leander, Johan and Hellström, Gustav and Nordin, Jonathan and Jonsson, Micael and Klaminder, Jonatan},
	year = {2024},
	note = {Publisher: John Wiley \& Sons},
	keywords = {⛔ No DOI found},
	pages = {107--115},
}

Salmonid repeat spawners are precious individuals for wild populations due to their high fecundity and previous spawning experience, making them important in environmental policy. However, repeat s ...

@article{karlsson_ice-melt_2024,
	title = {Ice-melt period dominates annual carbon dioxide evasion from clear-water {Arctic} lakes},
	volume = {9},
	copyright = {© 2023 The Authors. Limnology and Oceanography Letters published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10369},
	doi = {10.1002/lol2.10369},
	abstract = {Current estimates of carbon dioxide (CO2) evasion from Arctic lakes are highly uncertain because few studies integrate seasonal variability, specifically evasion during spring ice-melt. We quantified annual CO2 evasion for 14 clear-water Arctic lakes in Northern Sweden through mass balance (ice-melt period) and high-frequency loggers (open-water period). On average, 80\% (SD: ± 18) of annual CO2 evasion occurred within 10 d following ice-melt. The contribution of the ice-melt period to annual CO2 evasion was high compared to earlier studies of Arctic lakes (47\% ± 32\%). Across all lakes, the proportion of ice-melt : annual CO2 evasion was negatively related to the dissolved organic carbon concentration and positively related to the mean depth of the lakes. The results emphasize the need for measurements of CO2 exchange at ice-melt to accurately quantify CO2 evasion from Arctic lakes.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography Letters},
	author = {Karlsson, J. and Verheijen, H. A. and Seekell, D. A. and Vachon, D. and Klaus, M.},
	year = {2024},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10369},
	keywords = {⛔ No DOI found},
	pages = {112--118},
}

Current estimates of carbon dioxide (CO2) evasion from Arctic lakes are highly uncertain because few studies integrate seasonal variability, specifically evasion during spring ice-melt. We quantified annual CO2 evasion for 14 clear-water Arctic lakes in Northern Sweden through mass balance (ice-melt period) and high-frequency loggers (open-water period). On average, 80% (SD: ± 18) of annual CO2 evasion occurred within 10 d following ice-melt. The contribution of the ice-melt period to annual CO2 evasion was high compared to earlier studies of Arctic lakes (47% ± 32%). Across all lakes, the proportion of ice-melt : annual CO2 evasion was negatively related to the dissolved organic carbon concentration and positively related to the mean depth of the lakes. The results emphasize the need for measurements of CO2 exchange at ice-melt to accurately quantify CO2 evasion from Arctic lakes.

@article{gauthier_taking_2024,
	title = {Taking the beat of the {Arctic}: are lemming population cycles changing due to winter climate?},
	volume = {291},
	shorttitle = {Taking the beat of the {Arctic}},
	url = {https://royalsocietypublishing.org/doi/10.1098/rspb.2023.2361},
	doi = {10.1098/rspb.2023.2361},
	abstract = {Reports of fading vole and lemming population cycles and persisting low populations in some parts of the Arctic have raised concerns about the spread of these fundamental changes to tundra food web dynamics. By compiling 24 unique time series of lemming population fluctuations across the circumpolar region, we show that virtually all populations displayed alternating periods of cyclic/non-cyclic fluctuations over the past four decades. Cyclic patterns were detected 55\% of the time (n = 649 years pooled across sites) with a median periodicity of 3.7 years, and non-cyclic periods were not more frequent in recent years. Overall, there was an indication for a negative effect of warm spells occurring during the snow onset period of the preceding year on lemming abundance. However, winter duration or early winter climatic conditions did not differ on average between cyclic and non-cyclic periods. Analysis of the time series shows that there is presently no Arctic-wide collapse of lemming cycles, even though cycles have been sporadic at most sites during the last decades. Although non-stationary dynamics appears a common feature of lemming populations also in the past, continued warming in early winter may decrease the frequency of periodic irruptions with negative consequences for tundra ecosystems.},
	number = {2016},
	urldate = {2024-03-26},
	journal = {Proceedings of the Royal Society B: Biological Sciences},
	author = {Gauthier, Gilles and Ehrich, Dorothée and Belke-Brea, Maria and Domine, Florent and Alisauskas, Ray and Clark, Karin and Ecke, Frauke and Eide, Nina E. and Framstad, Erik and Frandsen, Jay and Gilg, Olivier and Henttonen, Heikki and Hörnfeldt, Birger and Kataev, Gennadiy D. and Menyushina, Irina E. and Oksanen, Lauri and Oksanen, Tarja and Olofsson, Johan and Samelius, Gustaf and Sittler, Benoit and Smith, Paul A. and Sokolov, Aleksandr A. and Sokolova, Natalia A. and Schmidt, Niels M.},
	month = feb,
	year = {2024},
	note = {Publisher: Royal Society},
	keywords = {Arctic tundra, climate warming, melt–freeze events, population dynamics, small mammals, transient dynamics},
	pages = {20232361},
}

Reports of fading vole and lemming population cycles and persisting low populations in some parts of the Arctic have raised concerns about the spread of these fundamental changes to tundra food web dynamics. By compiling 24 unique time series of lemming population fluctuations across the circumpolar region, we show that virtually all populations displayed alternating periods of cyclic/non-cyclic fluctuations over the past four decades. Cyclic patterns were detected 55% of the time (n = 649 years pooled across sites) with a median periodicity of 3.7 years, and non-cyclic periods were not more frequent in recent years. Overall, there was an indication for a negative effect of warm spells occurring during the snow onset period of the preceding year on lemming abundance. However, winter duration or early winter climatic conditions did not differ on average between cyclic and non-cyclic periods. Analysis of the time series shows that there is presently no Arctic-wide collapse of lemming cycles, even though cycles have been sporadic at most sites during the last decades. Although non-stationary dynamics appears a common feature of lemming populations also in the past, continued warming in early winter may decrease the frequency of periodic irruptions with negative consequences for tundra ecosystems.

@article{barthelemy_short-_2024,
	title = {Short- and long-term plant and microbial uptake of {15N}-labelled urea in a mesic tundra heath, {West} {Greenland}},
	volume = {47},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-216900},
	doi = {10.1007/s00300-023-03209-6},
	abstract = {Terrestrial animals are key elements in the cycling of elements in the Arctic where nutrient availability is low. Waste production by herbivores, in particular urine deposition, has a crucial role  ...},
	language = {eng},
	number = {1},
	urldate = {2024-03-26},
	journal = {Polar Biology},
	author = {Barthelemy, Hélène and Nobel, Liv Alexa and Stark, Sari and Väisänen, Maria and Olofsson, Johan and Michelsen, Anders},
	year = {2024},
	note = {Publisher: Springer Nature},
	pages = {1--15},
}

Terrestrial animals are key elements in the cycling of elements in the Arctic where nutrient availability is low. Waste production by herbivores, in particular urine deposition, has a crucial role ...

@article{smith_extreme_2024,
	title = {Extreme drought impacts have been underestimated in grasslands and shrublands globally},
	volume = {121},
	url = {https://www.pnas.org/doi/abs/10.1073/pnas.2309881120},
	doi = {10.1073/pnas.2309881120},
	number = {4},
	urldate = {2024-03-26},
	journal = {Proceedings of the National Academy of Sciences},
	author = {Smith, Melinda D. and Wilkins, Kate D. and Holdrege, Martin C. and Wilfahrt, Peter and Collins, Scott L. and Knapp, Alan K. and Sala, Osvaldo E. and Dukes, Jeffrey S. and Phillips, Richard P. and Yahdjian, Laura},
	year = {2024},
	note = {Publisher: National Acad Sciences},
	pages = {e2309881120},
}

@article{stark_ecosystem_2023,
	title = {The ecosystem effects of reindeer ({Rangifer} tarandus) in northern {Fennoscandia}: {Past}, present and future},
	volume = {58},
	issn = {1433-8319},
	shorttitle = {The ecosystem effects of reindeer (\textit{{Rangifer} tarandus}) in northern {Fennoscandia}},
	url = {https://www.sciencedirect.com/science/article/pii/S1433831922000580},
	doi = {10.1016/j.ppees.2022.125716},
	abstract = {The semi-domesticated nature of the reindeer (Rangifer tarandus L.) makes it a distinct case among the world’s herbivores. Here, we review the literature on how reindeer shape vegetation and soil carbon and nitrogen cycles in northernmost Fennoscandia. We first describe main historical events that shaped the present-day grazing patterns in the different countries, then discuss the methodological considerations needed for interpreting evidence from grazer exclosures in ecological and environmental contexts. We argue that it is critical to be aware that these experiments do not measure the effect of grazing per se, but rather, they measure the responses of existing ecosystem structure and function to the sudden cessation of grazing in an environment, which was to a large degree shaped by it. Studies show that the direction and the magnitude of the effects of reindeer on vegetation and soil processes vary across habitats and depend on both the current land-uses and the historically formed grazing regimes; knowledge of the history is thus a key prerequisite for understanding the role of reindeer in ecosystems. As a general trend, reindeer affect soil nutrient cycles to a stronger extent in subarctic than in boreal ecosystems. In sites where reindeer have changed soil nutrient availability, they indirectly modify vegetation and productivity even after the cessation of grazing. We reason that the concepts of cultural and natural landscapes are not mutually exclusive in the case of reindeer ranges. Understanding how the intensity and seasonal timing of both past and present grazing direct ecosystem changes under climate warming is crucial for predicting future ecosystem structures and functioning in northern Fennoscandia as well as ecosystems in general.},
	urldate = {2024-03-27},
	journal = {Perspectives in Plant Ecology, Evolution and Systematics},
	author = {Stark, Sari and Horstkotte, Tim and Kumpula, Jouko and Olofsson, Johan and Tømmervik, Hans and Turunen, Minna},
	month = mar,
	year = {2023},
	keywords = {Boreal forests, Grazing, Mountain birch, Soil Nutrient Cycling, Tundra heath, Ungulate},
	pages = {125716},
}

The semi-domesticated nature of the reindeer (Rangifer tarandus L.) makes it a distinct case among the world’s herbivores. Here, we review the literature on how reindeer shape vegetation and soil carbon and nitrogen cycles in northernmost Fennoscandia. We first describe main historical events that shaped the present-day grazing patterns in the different countries, then discuss the methodological considerations needed for interpreting evidence from grazer exclosures in ecological and environmental contexts. We argue that it is critical to be aware that these experiments do not measure the effect of grazing per se, but rather, they measure the responses of existing ecosystem structure and function to the sudden cessation of grazing in an environment, which was to a large degree shaped by it. Studies show that the direction and the magnitude of the effects of reindeer on vegetation and soil processes vary across habitats and depend on both the current land-uses and the historically formed grazing regimes; knowledge of the history is thus a key prerequisite for understanding the role of reindeer in ecosystems. As a general trend, reindeer affect soil nutrient cycles to a stronger extent in subarctic than in boreal ecosystems. In sites where reindeer have changed soil nutrient availability, they indirectly modify vegetation and productivity even after the cessation of grazing. We reason that the concepts of cultural and natural landscapes are not mutually exclusive in the case of reindeer ranges. Understanding how the intensity and seasonal timing of both past and present grazing direct ecosystem changes under climate warming is crucial for predicting future ecosystem structures and functioning in northern Fennoscandia as well as ecosystems in general.

@article{wu_investigating_2023,
	title = {Investigating the diet source influence on freshwater fish mercury bioaccumulation and fatty acids—{Experiences} from {Swedish} lakes and {Chinese} reservoirs},
	issn = {1573-3017},
	url = {https://doi.org/10.1007/s10646-023-02712-0},
	doi = {10.1007/s10646-023-02712-0},
	abstract = {Dietary uptake is key for transferring potentially toxic contaminants, such as mercury (Hg) and essential dietary nutrients, such as polyunsaturated fatty acids (PUFA), to consumers at higher trophic levels of aquatic food webs. We evaluated the role of diet sources for Hg bioaccumulation and PUFA retention in fish across lake food webs in seven Swedish lakes and two Chinese reservoirs. Fish total Hg (THg) and methyl-Hg (MeHg) differed greatly between the two countries: the Chinese fish contained less than 300 ng g−1 dry weight (d.w.) THg with less than 50\% as MeHg, versus the Swedish fishes which contained approximately 2000 ng g−1 d.w. THg and nearly 100\% as MeHg. Fatty acids enrichment of linoleic acids (LIN) were more prevalent in the Chinese fishes regardless of size (p {\textless} 0.05). Here we examined food web length, fish growth rates, and fatty acids patterns in relation to the quality of fish as a food source for both Hg and FA. Contrary to the expectation that biodilution of Hg throughout the food chain would explain these differences, a more complex picture emerged with high levels of Hg at the base of the food web in the Chinese reservoirs, a decoupling of fatty acid and Hg bioaccumulation, and a major role for both fish stocking and fish feed. It is hoped that this work will provide a nuanced picture of fish quality as a food source in different ecosystems.},
	language = {en},
	urldate = {2024-03-27},
	journal = {Ecotoxicology},
	author = {Wu, Pianpian and Yan, Haiyu and Kainz, Martin J. and Branfireun, Brian and Bergström, Ann-Kristin and Jing, Min and Bishop, Kevin},
	month = nov,
	year = {2023},
}

Dietary uptake is key for transferring potentially toxic contaminants, such as mercury (Hg) and essential dietary nutrients, such as polyunsaturated fatty acids (PUFA), to consumers at higher trophic levels of aquatic food webs. We evaluated the role of diet sources for Hg bioaccumulation and PUFA retention in fish across lake food webs in seven Swedish lakes and two Chinese reservoirs. Fish total Hg (THg) and methyl-Hg (MeHg) differed greatly between the two countries: the Chinese fish contained less than 300 ng g−1 dry weight (d.w.) THg with less than 50% as MeHg, versus the Swedish fishes which contained approximately 2000 ng g−1 d.w. THg and nearly 100% as MeHg. Fatty acids enrichment of linoleic acids (LIN) were more prevalent in the Chinese fishes regardless of size (p \textless 0.05). Here we examined food web length, fish growth rates, and fatty acids patterns in relation to the quality of fish as a food source for both Hg and FA. Contrary to the expectation that biodilution of Hg throughout the food chain would explain these differences, a more complex picture emerged with high levels of Hg at the base of the food web in the Chinese reservoirs, a decoupling of fatty acid and Hg bioaccumulation, and a major role for both fish stocking and fish feed. It is hoped that this work will provide a nuanced picture of fish quality as a food source in different ecosystems.

@article{stark_decreased_2023,
	title = {Decreased {Soil} {Microbial} {Nitrogen} {Under} {Vegetation} ‘{Shrubification}’ in the {Subarctic} {Forest}–{Tundra} {Ecotone}: {The} {Potential} {Role} of {Increasing} {Nutrient} {Competition} {Between} {Plants} and {Soil} {Microorganisms}},
	volume = {26},
	issn = {1435-0629},
	shorttitle = {Decreased {Soil} {Microbial} {Nitrogen} {Under} {Vegetation} ‘{Shrubification}’ in the {Subarctic} {Forest}–{Tundra} {Ecotone}},
	url = {https://doi.org/10.1007/s10021-023-00847-z},
	doi = {10.1007/s10021-023-00847-z},
	abstract = {The consequences of warming-induced ‘shrubification’ on Arctic soil carbon storage are receiving increased attention, as the majority of ecosystem carbon in these systems is stored in soils. Soil carbon cycles in these ecosystems are usually tightly coupled with nitrogen availability. Soil microbial responses to ‘shrubification’ may depend on the traits of the shrub species that increase in response to warming. Increase in deciduous shrubs such as Betula nana likely promotes a loss of soil carbon, whereas the opposite may be true if evergreen shrubs such as Empetrum hermaphroditum increase. We analyzed soil organic matter stocks and 13C NMR fractions, microbial CO2 respiration, biomass, extracellular enzyme activities (EEAs), and their association with shrub density in northern Sweden after 20 years of experimental warming using open top chambers (OTCs). Our study sites were located in a tundra heath that stores high soil carbon quantities and where the OTCs had increased deciduous shrubs, and in a mountain birch forest that stores lower soil carbon quantities and where the OTCs had increased evergreen shrubs. We predicted that organic matter stocks should be lower and respiration and EEAs higher inside the OTCs than untreated plots in the tundra, whereas no effect should be detected in the forest. Soil organic matter stocks and 13C NMR fractions remained unaffected at both sites. When expressed as per gram microbial biomass, respiration and EEAs for carbohydrate and chitin degradation were higher inside the OTCs, and contrasting our prediction, this effect was stronger in the forest. Unexpectedly, the OTCs also led to a substantially lower microbial biomass carbon and nitrogen irrespective of habitat. The decline in the microbial biomass counteracted increased activities resulting in no effect of the OTCs on respiration and a lower phenol oxidase activity per gram soil. Microbial biomass nitrogen correlated negatively with evergreen shrub density at both sites, indicating that ‘shrubification’ may have intensified nutrient competition between plants and soil microorganisms. Nutrient limitation could also underlie increased respiration per gram microbial biomass through limiting C assimilation into biomass. We hypothesize that increasing nutrient immobilization into long-lived evergreen shrubs could over time induce microbial nutrient limitation that contributes to a stability of accumulated soil organic matter stocks under climate warming.},
	language = {en},
	number = {7},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Stark, Sari and Kumar, Manoj and Myrsky, Eero and Vuorinen, Jere and Kantola, Anu M. and Telkki, Ville-Veikko and Sjögersten, Sofie and Olofsson, Johan and Männistö, Minna K.},
	month = nov,
	year = {2023},
	keywords = {\#nosource, CO2 release, Empetrum hermaphroditum, climate warming, extracellular enzymes, mountain birch forest, soil organic matter, tundra heath},
	pages = {1504--1523},
}

The consequences of warming-induced ‘shrubification’ on Arctic soil carbon storage are receiving increased attention, as the majority of ecosystem carbon in these systems is stored in soils. Soil carbon cycles in these ecosystems are usually tightly coupled with nitrogen availability. Soil microbial responses to ‘shrubification’ may depend on the traits of the shrub species that increase in response to warming. Increase in deciduous shrubs such as Betula nana likely promotes a loss of soil carbon, whereas the opposite may be true if evergreen shrubs such as Empetrum hermaphroditum increase. We analyzed soil organic matter stocks and 13C NMR fractions, microbial CO2 respiration, biomass, extracellular enzyme activities (EEAs), and their association with shrub density in northern Sweden after 20 years of experimental warming using open top chambers (OTCs). Our study sites were located in a tundra heath that stores high soil carbon quantities and where the OTCs had increased deciduous shrubs, and in a mountain birch forest that stores lower soil carbon quantities and where the OTCs had increased evergreen shrubs. We predicted that organic matter stocks should be lower and respiration and EEAs higher inside the OTCs than untreated plots in the tundra, whereas no effect should be detected in the forest. Soil organic matter stocks and 13C NMR fractions remained unaffected at both sites. When expressed as per gram microbial biomass, respiration and EEAs for carbohydrate and chitin degradation were higher inside the OTCs, and contrasting our prediction, this effect was stronger in the forest. Unexpectedly, the OTCs also led to a substantially lower microbial biomass carbon and nitrogen irrespective of habitat. The decline in the microbial biomass counteracted increased activities resulting in no effect of the OTCs on respiration and a lower phenol oxidase activity per gram soil. Microbial biomass nitrogen correlated negatively with evergreen shrub density at both sites, indicating that ‘shrubification’ may have intensified nutrient competition between plants and soil microorganisms. Nutrient limitation could also underlie increased respiration per gram microbial biomass through limiting C assimilation into biomass. We hypothesize that increasing nutrient immobilization into long-lived evergreen shrubs could over time induce microbial nutrient limitation that contributes to a stability of accumulated soil organic matter stocks under climate warming.

@article{morlock_erosion_2023,
	title = {Erosion regime controls sediment environmental {DNA}-based community reconstruction},
	volume = {5},
	copyright = {© 2023 The Authors. Environmental DNA published by John Wiley \& Sons Ltd.},
	issn = {2637-4943},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/edn3.458},
	doi = {10.1002/edn3.458},
	abstract = {Analysis of environmental DNA detected in lake sediments shows promise to become a great paleoecological technique that can provide detailed information about organism communities living in past environments. However, when interpreting sedimentary environmental DNA records, it is of crucial importance to separate ecosystem responses to large-scale environmental change from “noise” caused by changes in sediment provenance or potential post-depositional DNA mobility. In this study, we show that plant and mammalian communities reconstructed from sediments are strongly affected by sediment provenance, but unaffected by vertical mobility of DNA after sediment deposition. We observe that DNA from aquatic plants was abundant in background sediment, while embedded detrital event layers (sediment deposited under erosion events) primarily contained terrestrial plants; hence, vertical mobility of aquatic plant DNA across sediment layers was negligible within our studied lakes. About 33\% of the identified terrestrial plant genera were only found in detrital sediment, suggesting that sediment origin had a strong impact on the reconstructed plant community. Similarly, DNA of some mammalian taxa (Capra hircus, Ursus arctos, Lepus, and Felis) were only or preferentially found in detrital event layers. Temporal changes across the Holocene were the main drivers of change for reconstructed plant communities, but sediment type was the second most important factor of variance. Our results highlight that erosion and sediment provenance need to be considered when reconstructing past mammalian and plant communities using environmental DNA from lake sediments.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Environmental DNA},
	author = {Morlock, Marina A. and Rodriguez-Martinez, Saúl and Huang, Doreen Yu-Tuan and Klaminder, Jonatan},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/edn3.458},
	keywords = {DNA taphonomy, Lake Grosssee, Switzerland, erosion, lake sediment, paleoecology, sedaDNA},
	pages = {1393--1404},
}

Analysis of environmental DNA detected in lake sediments shows promise to become a great paleoecological technique that can provide detailed information about organism communities living in past environments. However, when interpreting sedimentary environmental DNA records, it is of crucial importance to separate ecosystem responses to large-scale environmental change from “noise” caused by changes in sediment provenance or potential post-depositional DNA mobility. In this study, we show that plant and mammalian communities reconstructed from sediments are strongly affected by sediment provenance, but unaffected by vertical mobility of DNA after sediment deposition. We observe that DNA from aquatic plants was abundant in background sediment, while embedded detrital event layers (sediment deposited under erosion events) primarily contained terrestrial plants; hence, vertical mobility of aquatic plant DNA across sediment layers was negligible within our studied lakes. About 33% of the identified terrestrial plant genera were only found in detrital sediment, suggesting that sediment origin had a strong impact on the reconstructed plant community. Similarly, DNA of some mammalian taxa (Capra hircus, Ursus arctos, Lepus, and Felis) were only or preferentially found in detrital event layers. Temporal changes across the Holocene were the main drivers of change for reconstructed plant communities, but sediment type was the second most important factor of variance. Our results highlight that erosion and sediment provenance need to be considered when reconstructing past mammalian and plant communities using environmental DNA from lake sediments.

@article{klaminder_landscape_2023,
	title = {Landscape of ice and fire – uniquely well-preserved {Scots} pine trunks reveal forest fires near the retreating {Weichselian} ice margin},
	volume = {1},
	issn = {1617-6278},
	url = {https://doi.org/10.1007/s00334-023-00974-6},
	doi = {10.1007/s00334-023-00974-6},
	abstract = {Environmental conditions for trees that established in central Fennoscandia shortly after the final retreat of the Weichselian ice sheet remain poorly understood. In this study we examine tree rings of five well-preserved Pinus sylvestris (Scots pines) that grew in the area in front of the retreating ice sheet in northern Sweden. They became buried in flood sediments deposited by a glacial outburst flood (jökulhlaup) about 9.5–9.9 kyr cal bp and the aim of our study was to search for information regarding damage from fires and bioclimatic conditions in their ancient tree ring records. Our analysis, providing a glimpse into the local early Holocene environment in north-central Sweden, suggests that: 1, there were repeated fires (four fire events detected) during the early Holocene; and 2, bioclimatic conditions when the ancient pines were growing resembled those of modern sub-alpine pine woods. The latter is indicated by their patterns of tree ring growth (growth rate and variation), which were statistically similar to those of pines growing in sub-alpine woods with an open canopy, but different from pines in protected and managed boreal forests. Lower δ13C for the ancient latewood in comparison to pine wood from trees growing near the Scandinavian mountains before the 1850s were probably caused both by stomata fractionation due to lower atmospheric CO2 during the early Holocene and by the moist local environment created by the nearby ancient Ancylus lake, which preceded the Baltic Sea. Periods with cloudy and cold summers were also indicated by the occurrence of ‘false rings’. Finds of charred fragments of Calluna vulgaris (heather, ling), an understory shrub that can burn even with a relatively high moisture content, suggest that heath vegetation was crucial to make fire a reoccurring ecological factor in the area during the early Holocene.},
	language = {en},
	urldate = {2024-03-27},
	journal = {Vegetation History and Archaeobotany},
	author = {Klaminder, Jonatan and Fassl, Magdalena and Baudet, Marlène and Östlund, Lars and Linderholm, Johan and Zale, Rolf},
	month = dec,
	year = {2023},
	keywords = {Climate, Early Holocene, Forest fires, Forest history, Lycksele, Pinus sylvestris},
}

Environmental conditions for trees that established in central Fennoscandia shortly after the final retreat of the Weichselian ice sheet remain poorly understood. In this study we examine tree rings of five well-preserved Pinus sylvestris (Scots pines) that grew in the area in front of the retreating ice sheet in northern Sweden. They became buried in flood sediments deposited by a glacial outburst flood (jökulhlaup) about 9.5–9.9 kyr cal bp and the aim of our study was to search for information regarding damage from fires and bioclimatic conditions in their ancient tree ring records. Our analysis, providing a glimpse into the local early Holocene environment in north-central Sweden, suggests that: 1, there were repeated fires (four fire events detected) during the early Holocene; and 2, bioclimatic conditions when the ancient pines were growing resembled those of modern sub-alpine pine woods. The latter is indicated by their patterns of tree ring growth (growth rate and variation), which were statistically similar to those of pines growing in sub-alpine woods with an open canopy, but different from pines in protected and managed boreal forests. Lower δ13C for the ancient latewood in comparison to pine wood from trees growing near the Scandinavian mountains before the 1850s were probably caused both by stomata fractionation due to lower atmospheric CO2 during the early Holocene and by the moist local environment created by the nearby ancient Ancylus lake, which preceded the Baltic Sea. Periods with cloudy and cold summers were also indicated by the occurrence of ‘false rings’. Finds of charred fragments of Calluna vulgaris (heather, ling), an understory shrub that can burn even with a relatively high moisture content, suggest that heath vegetation was crucial to make fire a reoccurring ecological factor in the area during the early Holocene.

@article{vaisanen_tundra_2023,
	title = {Tundra cryogenic land surface processes and {CO2}–{C} balance in sub-{Arctic} alpine environment withstand winter and spring warming},
	volume = {2},
	issn = {2752-5295},
	url = {https://dx.doi.org/10.1088/2752-5295/acc08b},
	doi = {10.1088/2752-5295/acc08b},
	abstract = {Cryogenic land surface processes (CLSPs), such as cryoturbation, are currently active in landscapes covering 25\% of our planet where they dictate key functions, such as carbon (C) cycling, and maintain patterned landscape features. While CLSPs are expected to diminish in the near future due to milder winters especially in the southern parts of the Arctic, the shifts in C cycling in these landscapes may be more complex, since climate change can affect C cycling directly but also indirectly via CLSPs. Here, we study the effects of changing winter and spring climate on CLSPs and C cycling in non-sorted circles consisting of barren frost boils and their vegetated rims. We do this by measuring cryoturbation and ecosystem CO2 fluxes repeatedly in alpine subarctic tundra where temperatures during naturally snow covered period have been experimentally increased with snow-trapping fences and temperatures during winter and spring period after snowmelt have been increased with insulating fleeces. Opposite to our hypothesis, warming treatments did not decrease cryoturbation. However, winter warming via deeper snow increased ecosystem C sink during summer by decreasing ecosystem CO2 release in the frost boils and by counterbalancing the negative effects of cryoturbation on plant CO2 uptake in the vegetated rims. Our results suggest that short-term changes in winter and spring climate may not alter cryoturbation and jeopardize the tundra C sink.},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {Environmental Research: Climate},
	author = {Väisänen, Maria and Klaminder, Jonatan and Ylänne, Henni and Teuber, Laurenz and Dorrepaal, Ellen and Krab, Eveline J.},
	month = mar,
	year = {2023},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {021001},
}

Cryogenic land surface processes (CLSPs), such as cryoturbation, are currently active in landscapes covering 25% of our planet where they dictate key functions, such as carbon (C) cycling, and maintain patterned landscape features. While CLSPs are expected to diminish in the near future due to milder winters especially in the southern parts of the Arctic, the shifts in C cycling in these landscapes may be more complex, since climate change can affect C cycling directly but also indirectly via CLSPs. Here, we study the effects of changing winter and spring climate on CLSPs and C cycling in non-sorted circles consisting of barren frost boils and their vegetated rims. We do this by measuring cryoturbation and ecosystem CO2 fluxes repeatedly in alpine subarctic tundra where temperatures during naturally snow covered period have been experimentally increased with snow-trapping fences and temperatures during winter and spring period after snowmelt have been increased with insulating fleeces. Opposite to our hypothesis, warming treatments did not decrease cryoturbation. However, winter warming via deeper snow increased ecosystem C sink during summer by decreasing ecosystem CO2 release in the frost boils and by counterbalancing the negative effects of cryoturbation on plant CO2 uptake in the vegetated rims. Our results suggest that short-term changes in winter and spring climate may not alter cryoturbation and jeopardize the tundra C sink.

@article{sofo_earthworm-driven_2023,
	title = {Earthworm-{Driven} {Changes} in {Soil} {Chemico}-{Physical} {Properties}, {Soil} {Bacterial} {Microbiota}, {Tree}/{Tea} {Litter} {Decomposition}, and {Plant} {Growth} in a {Mesocosm} {Experiment} with {Two} {Plant} {Species}},
	volume = {12},
	copyright = {http://creativecommons.org/licenses/by/3.0/},
	issn = {2223-7747},
	url = {https://www.mdpi.com/2223-7747/12/6/1216},
	doi = {10.3390/plants12061216},
	abstract = {Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89\% in broccoli and +223\% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (kTBI) and a lower stabilization factor (STBI), whereas decomposition in the litter bags (dlitter) increased by about 6\% in broccoli and 5\% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Plants},
	author = {Sofo, Adriano and Khanghahi, Mohammad Yaghoubi and Curci, Maddalena and Reyes, Francesco and Briones, Maria J. I. and Sarneel, Judith M. and Cardinale, Domenico and Crecchio, Carmine},
	month = jan,
	year = {2023},
	note = {Number: 6
Publisher: Multidisciplinary Digital Publishing Institute},
	keywords = {\textit{Eisenia} sp., Tea Bag Index, carbon/nitrogen ratio, olive litter, soil bacteria, soil chemico-physical properties, soil sustainable management},
	pages = {1216},
}

Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89% in broccoli and +223% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (kTBI) and a lower stabilization factor (STBI), whereas decomposition in the litter bags (dlitter) increased by about 6% in broccoli and 5% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems.

@article{skerlep_differential_2023,
	title = {Differential {Trends} in {Iron} {Concentrations} of {Boreal} {Streams} {Linked} to {Catchment} {Characteristics}},
	volume = {37},
	copyright = {© 2023. The Authors.},
	issn = {1944-9224},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GB007484},
	doi = {10.1029/2022GB007484},
	abstract = {Increasing iron (Fe) concentrations have been reported for freshwaters across northern Europe over the last decades. This increase, together with elevated concentrations of dissolved organic carbon (DOC), leads to browning of freshwaters, which affects aquatic organisms, ecosystem functioning, biogeochemical cycles, and brings challenges to drinking water production. However, how such increasing trends in stream Fe concentrations reflect the contribution of different catchment sources remains poorly resolved. Here, we explored how catchment characteristics, that is, mires and coniferous soils, regulate spatial and temporal patterns of Fe in a boreal stream network. For this, we determined Fe speciation in riparian and mire soils, and studied temporal Fe dynamics in soil-water and stream-water over a span of 18 years. Positive Fe trends were found in the solution of the riparian soil, while no long-term trend was observed in the mire. These differences were reflected in stream-water, where three headwater streams dominated by coniferous cover also displayed positive Fe trends, whereas the mire dominated stream showed no trend. Surprisingly, the majority of higher order streams showed declining Fe trends, despite long-term increases in DOC. In addition, we found that an extreme drought event led to a prolonged release of Fe and DOC from the riparian soils, that could have long-term effects on stream Fe concentrations. Our results show that riparian forest soils can be major contributors to ongoing increases in freshwater Fe concentrations and that drought can further promote the release of Fe from organic soils.},
	language = {en},
	number = {3},
	urldate = {2024-03-27},
	journal = {Global Biogeochemical Cycles},
	author = {Škerlep, M. and Nehzati, S. and Sponseller, R. A. and Persson, P. and Laudon, H. and Kritzberg, E. S.},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GB007484},
	keywords = {browning, catchment, iron, mire, riparian zone, stream},
	pages = {e2022GB007484},
}

Increasing iron (Fe) concentrations have been reported for freshwaters across northern Europe over the last decades. This increase, together with elevated concentrations of dissolved organic carbon (DOC), leads to browning of freshwaters, which affects aquatic organisms, ecosystem functioning, biogeochemical cycles, and brings challenges to drinking water production. However, how such increasing trends in stream Fe concentrations reflect the contribution of different catchment sources remains poorly resolved. Here, we explored how catchment characteristics, that is, mires and coniferous soils, regulate spatial and temporal patterns of Fe in a boreal stream network. For this, we determined Fe speciation in riparian and mire soils, and studied temporal Fe dynamics in soil-water and stream-water over a span of 18 years. Positive Fe trends were found in the solution of the riparian soil, while no long-term trend was observed in the mire. These differences were reflected in stream-water, where three headwater streams dominated by coniferous cover also displayed positive Fe trends, whereas the mire dominated stream showed no trend. Surprisingly, the majority of higher order streams showed declining Fe trends, despite long-term increases in DOC. In addition, we found that an extreme drought event led to a prolonged release of Fe and DOC from the riparian soils, that could have long-term effects on stream Fe concentrations. Our results show that riparian forest soils can be major contributors to ongoing increases in freshwater Fe concentrations and that drought can further promote the release of Fe from organic soils.

@article{peters_as_2023,
	title = {As good as human experts in detecting plant roots in minirhizotron images but efficient and reproducible: the convolutional neural network “{RootDetector}”},
	volume = {13},
	copyright = {2023 The Author(s)},
	issn = {2045-2322},
	shorttitle = {As good as human experts in detecting plant roots in minirhizotron images but efficient and reproducible},
	url = {https://www.nature.com/articles/s41598-023-28400-x},
	doi = {10.1038/s41598-023-28400-x},
	abstract = {Plant roots influence many ecological and biogeochemical processes, such as carbon, water and nutrient cycling. Because of difficult accessibility, knowledge on plant root growth dynamics in field conditions, however, is fragmentary at best. Minirhizotrons, i.e. transparent tubes placed in the substrate into which specialized cameras or circular scanners are inserted, facilitate the capture of high-resolution images of root dynamics at the soil-tube interface with little to no disturbance after the initial installation. Their use, especially in field studies with multiple species and heterogeneous substrates, though, is limited by the amount of work that subsequent manual tracing of roots in the images requires. Furthermore, the reproducibility and objectivity of manual root detection is questionable. Here, we use a Convolutional Neural Network (CNN) for the automatic detection of roots in minirhizotron images and compare the performance of our RootDetector with human analysts with different levels of expertise. Our minirhizotron data come from various wetlands on organic soils, i.e. highly heterogeneous substrates consisting of dead plant material, often times mainly roots, in various degrees of decomposition. This may be seen as one of the most challenging soil types for root segmentation in minirhizotron images. RootDetector showed a high capability to correctly segment root pixels in minirhizotron images from field observations (F1 = 0.6044; r2 compared to a human expert = 0.99). Reproducibility among humans, however, depended strongly on expertise level, with novices showing drastic variation among individual analysts and annotating on average more than 13-times higher root length/cm2 per image compared to expert analysts. CNNs such as RootDetector provide a reliable and efficient method for the detection of roots and root length in minirhizotron images even from challenging field conditions. Analyses with RootDetector thus save resources, are reproducible and objective, and are as accurate as manual analyses performed by human experts.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Scientific Reports},
	author = {Peters, Bo and Blume-Werry, Gesche and Gillert, Alexander and Schwieger, Sarah and von Lukas, Uwe Freiherr and Kreyling, Juergen},
	month = jan,
	year = {2023},
	note = {Publisher: Nature Publishing Group},
	keywords = {Ecosystem ecology, Imaging},
	pages = {1399},
}

Plant roots influence many ecological and biogeochemical processes, such as carbon, water and nutrient cycling. Because of difficult accessibility, knowledge on plant root growth dynamics in field conditions, however, is fragmentary at best. Minirhizotrons, i.e. transparent tubes placed in the substrate into which specialized cameras or circular scanners are inserted, facilitate the capture of high-resolution images of root dynamics at the soil-tube interface with little to no disturbance after the initial installation. Their use, especially in field studies with multiple species and heterogeneous substrates, though, is limited by the amount of work that subsequent manual tracing of roots in the images requires. Furthermore, the reproducibility and objectivity of manual root detection is questionable. Here, we use a Convolutional Neural Network (CNN) for the automatic detection of roots in minirhizotron images and compare the performance of our RootDetector with human analysts with different levels of expertise. Our minirhizotron data come from various wetlands on organic soils, i.e. highly heterogeneous substrates consisting of dead plant material, often times mainly roots, in various degrees of decomposition. This may be seen as one of the most challenging soil types for root segmentation in minirhizotron images. RootDetector showed a high capability to correctly segment root pixels in minirhizotron images from field observations (F1 = 0.6044; r2 compared to a human expert = 0.99). Reproducibility among humans, however, depended strongly on expertise level, with novices showing drastic variation among individual analysts and annotating on average more than 13-times higher root length/cm2 per image compared to expert analysts. CNNs such as RootDetector provide a reliable and efficient method for the detection of roots and root length in minirhizotron images even from challenging field conditions. Analyses with RootDetector thus save resources, are reproducible and objective, and are as accurate as manual analyses performed by human experts.

@article{pajala_effects_2023,
	title = {The {Effects} of {Water} {Column} {Dissolved} {Oxygen} {Concentrations} on {Lake} {Methane} {Emissions}—{Results} {From} a {Whole}-{Lake} {Oxygenation} {Experiment}},
	volume = {128},
	copyright = {© 2023. The Authors.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007185},
	doi = {10.1029/2022JG007185},
	abstract = {Lakes contribute 9\%–19\% of global methane (CH4) emissions to the atmosphere. Dissolved molecular oxygen (DO) in lakes can inhibit the production of CH4 and promote CH4 oxidation. DO is therefore often considered an important regulator of CH4 emissions from lakes. Presence or absence of DO in the water above the sediments can affect CH4 production and emissions by (a) influencing if methane production can be fueled by the most reactive organic matter in the top sediment layer or rely on deeper and less degradable organic matter, and (b) enabling CH4 accumulation in deep waters and potentially large emissions upon water column turnover. However, the relative importance of these two DO effects on CH4 fluxes is still unclear. We assessed CH4 fluxes from two connected lake basins in northern boreal Sweden where one was experimentally oxygenated. Results showed no clear difference in summer CH4 emissions attributable to water column DO concentrations. Large amounts of CH4 accumulated in the anoxic hypolimnion of the reference basin but little of this may have been emitted because of incomplete mixing, and effective methane oxidation of stored CH4 reaching oxic water layers. Accordingly, ≤24\% of the stored CH4 was likely emitted in the experimental lake. Overall, our results suggest that hypolimnetic DO and water column CH4 storage might have a smaller impact on CH4 emissions in boreal forest lakes than previous estimates, yet potential fluxes associated with water column turnover events remain a significant uncertainty in lake CH4 emission estimates.},
	language = {en},
	number = {11},
	urldate = {2024-03-27},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Pajala, Gustav and Sawakuchi, Henrique O. and Rudberg, David and Schenk, Jonathan and Sieczko, Anna and Gålfalk, Magnus and Seekell, David and Sundgren, Ingrid and Thanh Duc, Nguyen and Karlsson, Jan and Bastviken, David},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007185},
	keywords = {dissolved oxygen, emissions, methane, methane oxidation, storage},
	pages = {e2022JG007185},
}

Lakes contribute 9%–19% of global methane (CH4) emissions to the atmosphere. Dissolved molecular oxygen (DO) in lakes can inhibit the production of CH4 and promote CH4 oxidation. DO is therefore often considered an important regulator of CH4 emissions from lakes. Presence or absence of DO in the water above the sediments can affect CH4 production and emissions by (a) influencing if methane production can be fueled by the most reactive organic matter in the top sediment layer or rely on deeper and less degradable organic matter, and (b) enabling CH4 accumulation in deep waters and potentially large emissions upon water column turnover. However, the relative importance of these two DO effects on CH4 fluxes is still unclear. We assessed CH4 fluxes from two connected lake basins in northern boreal Sweden where one was experimentally oxygenated. Results showed no clear difference in summer CH4 emissions attributable to water column DO concentrations. Large amounts of CH4 accumulated in the anoxic hypolimnion of the reference basin but little of this may have been emitted because of incomplete mixing, and effective methane oxidation of stored CH4 reaching oxic water layers. Accordingly, ≤24% of the stored CH4 was likely emitted in the experimental lake. Overall, our results suggest that hypolimnetic DO and water column CH4 storage might have a smaller impact on CH4 emissions in boreal forest lakes than previous estimates, yet potential fluxes associated with water column turnover events remain a significant uncertainty in lake CH4 emission estimates.

@article{mosquera_concentration-discharge_2023,
	title = {Concentration-{Discharge} {Patterns} {Reveal} {Catchment} {Controls} {Over} the {Stoichiometry} of {Carbon} and {Nutrient} {Supply} to {Boreal} {Streams}},
	volume = {128},
	copyright = {© 2023. The Authors.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007179},
	doi = {10.1029/2022JG007179},
	abstract = {Carbon (C), nitrogen (N), and phosphorus (P) export from catchments is strongly regulated by interactions between hydrological flowpaths and their terrestrial use/storage. While concentration-discharge (c-Q) relationships have been widely used to understand this interplay for C, N, and P individually, how flow regulates the relative supply of these resources across spatial and temporal scales is not well documented. Here, we analyze c-Q relationships from 12 years of data to test how seasonal flow regulates the concentrations of inorganic N (Dissolved inorganic nitrogen [DIN]) and P (Dissolved inorganic phosphorus [DIP]), dissolved organic N (DON) and C (dissolved organic carbon [DOC]) and their respective ratios across 12 streams in a boreal landscape. We observed opposing c-Q relationships between organic and inorganic solutes. DOC and DON tended toward transport limitation with little year-to-year change, whereas ammonium (NH4) and DIP were increasingly source limited over time. These different c-Q relationships translated into large (up to three-fold) shifts in resource ratios (e.g., DOC:DIN) in response to changes in flow. Our results also highlight strong influences of catchment structure on c-Q patterns, regardless of solute, season, and longer-term directional changes. Here, the organic solute c-Q responses became less transport limited over time; while inorganic solute responses became less source limited with increasing mire/decreasing forest cover. Overall, differences in timing of catchment exports for C, N, and P, create dynamic variation in solute concentrations in streams with subsequent impacts on resource stoichiometry that is central to aquatic ecological processes.},
	language = {en},
	number = {8},
	urldate = {2024-03-26},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Mosquera, Virginia and Laudon, Hjalmar and Blackburn, Meredith and Hasselquist, Eliza Maher and Sponseller, Ryan A.},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007179},
	keywords = {boreal catchments, concentration-discharge relationships, dissolved organic carbon, nitrogen, nutrient stoichiometry, phosphorus},
	pages = {e2022JG007179},
}

Carbon (C), nitrogen (N), and phosphorus (P) export from catchments is strongly regulated by interactions between hydrological flowpaths and their terrestrial use/storage. While concentration-discharge (c-Q) relationships have been widely used to understand this interplay for C, N, and P individually, how flow regulates the relative supply of these resources across spatial and temporal scales is not well documented. Here, we analyze c-Q relationships from 12 years of data to test how seasonal flow regulates the concentrations of inorganic N (Dissolved inorganic nitrogen [DIN]) and P (Dissolved inorganic phosphorus [DIP]), dissolved organic N (DON) and C (dissolved organic carbon [DOC]) and their respective ratios across 12 streams in a boreal landscape. We observed opposing c-Q relationships between organic and inorganic solutes. DOC and DON tended toward transport limitation with little year-to-year change, whereas ammonium (NH4) and DIP were increasingly source limited over time. These different c-Q relationships translated into large (up to three-fold) shifts in resource ratios (e.g., DOC:DIN) in response to changes in flow. Our results also highlight strong influences of catchment structure on c-Q patterns, regardless of solute, season, and longer-term directional changes. Here, the organic solute c-Q responses became less transport limited over time; while inorganic solute responses became less source limited with increasing mire/decreasing forest cover. Overall, differences in timing of catchment exports for C, N, and P, create dynamic variation in solute concentrations in streams with subsequent impacts on resource stoichiometry that is central to aquatic ecological processes.

@article{milarska_complete_2023,
	title = {Complete chloroplast genomes of {Cerastium} alpinum, {C}. arcticum and {C}. nigrescens: genome structures, comparative and phylogenetic analysis},
	volume = {13},
	copyright = {2023 The Author(s)},
	issn = {2045-2322},
	shorttitle = {Complete chloroplast genomes of {Cerastium} alpinum, {C}. arcticum and {C}. nigrescens},
	url = {https://www.nature.com/articles/s41598-023-46017-y},
	doi = {10.1038/s41598-023-46017-y},
	abstract = {The genus Cerastium includes about 200 species that are mostly found in the temperate climates of the Northern Hemisphere. Here we report the complete chloroplast genomes of Cerastium alpinum, C. arcticum and C. nigrescens. The length of cp genomes ranged from 147,940 to 148,722 bp. Their quadripartite circular structure had the same gene organization and content, containing 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Repeat sequences varied from 16 to 23 per species, with palindromic repeats being the most frequent. The number of identified SSRs ranged from 20 to 23 per species and they were mainly composed of mononucleotide repeats containing A/T units. Based on Ka/Ks ratio values, most genes were subjected to purifying selection. The newly sequenced chloroplast genomes were characterized by a high frequency of RNA editing, including both C to U and U to C conversion. The phylogenetic relationships within the genus Cerastium and family Caryophyllaceae were reconstructed based on the sequences of 71 protein-coding genes. The topology of the phylogenetic tree was consistent with the systematic position of the studied species. All representatives of the genus Cerastium were gathered in a single clade with C. glomeratum sharing the least similarity with the others.},
	language = {en},
	number = {1},
	urldate = {2024-03-26},
	journal = {Scientific Reports},
	author = {Milarska, Sylwia E. and Androsiuk, Piotr and Paukszto, Łukasz and Jastrzębski, Jan P. and Maździarz, Mateusz and Larson, Keith W. and Giełwanowska, Irena},
	month = oct,
	year = {2023},
	note = {Publisher: Nature Publishing Group},
	keywords = {Genetics, Plant sciences},
	pages = {18774},
}

The genus Cerastium includes about 200 species that are mostly found in the temperate climates of the Northern Hemisphere. Here we report the complete chloroplast genomes of Cerastium alpinum, C. arcticum and C. nigrescens. The length of cp genomes ranged from 147,940 to 148,722 bp. Their quadripartite circular structure had the same gene organization and content, containing 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Repeat sequences varied from 16 to 23 per species, with palindromic repeats being the most frequent. The number of identified SSRs ranged from 20 to 23 per species and they were mainly composed of mononucleotide repeats containing A/T units. Based on Ka/Ks ratio values, most genes were subjected to purifying selection. The newly sequenced chloroplast genomes were characterized by a high frequency of RNA editing, including both C to U and U to C conversion. The phylogenetic relationships within the genus Cerastium and family Caryophyllaceae were reconstructed based on the sequences of 71 protein-coding genes. The topology of the phylogenetic tree was consistent with the systematic position of the studied species. All representatives of the genus Cerastium were gathered in a single clade with C. glomeratum sharing the least similarity with the others.

@article{kashi_nutrients_2023,
	title = {Nutrients {Alter} {Methane} {Production} and {Oxidation} in a {Thawing} {Permafrost} {Mire}},
	volume = {26},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-022-00758-5},
	doi = {10.1007/s10021-022-00758-5},
	abstract = {Permafrost thaw releases nutrients and metals from previously frozen soils and these nutrients may affect important biogeochemical processes including methane (CH4) production and oxidation. Here we assessed how concentrations of nutrients, solutes, and metals varied across four plant communities undergoing permafrost thaw and if these geochemical characteristics affected rates of CH4 production and oxidation. We tested nutrient limitation in CH4 production and oxidation by experimentally adding nitrogen (N), phosphorus (P) and a permafrost leachate to peat across these four plant communities. The upper 20 cm of permafrost contained 715 ± 298 mg m−2 of extractable inorganic N and 20 ± 6 mg m−2 of resin-extractable phosphorus (Presin), for a N:P ratio of 36:1. These low amounts of Presin coincide with high acid-digestible aluminum (Al), iron (Fe), and P concentrations in the permafrost soil and suggest that P may accumulate via sorption and constrain easily available forms of P for plants and microbes. Permafrost leachate additions decreased potential CH4 production rates up to 80\% and decreased CH4 oxidation rates by 66\%, likely due to inhibitory effects of N in the permafrost. In contrast, organic and inorganic P additions increased CH4 oxidation rates up to 36\% in the tall graminoid fen, a community where phosphate availability was low and CH4 production was high. Our results suggest that (1) inorganic N is available immediately from permafrost thaw, while (2) P availability is controlled by sorption properties, and (3) plant community, nutrient stoichiometry, and metal availability modulate how permafrost thaw affects CH4 production and oxidation.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Ecosystems},
	author = {Kashi, N. Niloufar and Hobbie, Erik A. and Varner, Ruth K. and Wymore, Adam S. and Ernakovich, Jessica G. and Giesler, Reiner},
	month = mar,
	year = {2023},
	keywords = {\#nosource, iron, methane oxidation, methane production, nutrients, peatlands, permafrost, phosphorus sorption, resource stoichiometry},
	pages = {302--317},
}

Permafrost thaw releases nutrients and metals from previously frozen soils and these nutrients may affect important biogeochemical processes including methane (CH4) production and oxidation. Here we assessed how concentrations of nutrients, solutes, and metals varied across four plant communities undergoing permafrost thaw and if these geochemical characteristics affected rates of CH4 production and oxidation. We tested nutrient limitation in CH4 production and oxidation by experimentally adding nitrogen (N), phosphorus (P) and a permafrost leachate to peat across these four plant communities. The upper 20 cm of permafrost contained 715 ± 298 mg m−2 of extractable inorganic N and 20 ± 6 mg m−2 of resin-extractable phosphorus (Presin), for a N:P ratio of 36:1. These low amounts of Presin coincide with high acid-digestible aluminum (Al), iron (Fe), and P concentrations in the permafrost soil and suggest that P may accumulate via sorption and constrain easily available forms of P for plants and microbes. Permafrost leachate additions decreased potential CH4 production rates up to 80% and decreased CH4 oxidation rates by 66%, likely due to inhibitory effects of N in the permafrost. In contrast, organic and inorganic P additions increased CH4 oxidation rates up to 36% in the tall graminoid fen, a community where phosphate availability was low and CH4 production was high. Our results suggest that (1) inorganic N is available immediately from permafrost thaw, while (2) P availability is controlled by sorption properties, and (3) plant community, nutrient stoichiometry, and metal availability modulate how permafrost thaw affects CH4 production and oxidation.

@article{jessen_understory_2023,
	title = {Understory functional groups and fire history but not experimental warming drive tree seedling performance in unmanaged boreal forests},
	volume = {6},
	issn = {2624-893X},
	url = {https://www.frontiersin.org/articles/10.3389/ffgc.2023.1130532},
	doi = {10.3389/ffgc.2023.1130532},
	abstract = {Survival and growth of tree seedlings are key processes of regeneration in forest ecosystems. However, little is known about how climate warming modulates seedling performance either directly or in interaction with understory vegetation and post-fire successional stages. We measured survival (over three years) and growth of seedlings of three tree species (Betula pubescens, Pinus sylvestris and Picea abies) in a full-factorial field experiment with passive warming and removal of two plant functional groups (feather moss and/or ericaceous shrubs) along a post-fire chronosequence in an unmanaged boreal forest. Warming had no effect on seedling survival over time or on relative biomass growth. Meanwhile, moss removal greatly increased seedling survival overall, while shrub removal cancelled this effect for B. pubescens seedlings. In addition, B. pubescens and P. sylvestris survival benefitted most from moss removal in old forests ({\textgreater}260 years since last fire disturbance). In contrast to survival, seedling growth was promoted by shrub removal for two out of three species, i.e., P. sylvestris and P. abies, meaning that seedling survival and growth are governed by different understory functional groups affecting seedling performance through different mechanism and modes of action. Our findings highlight that understory vegetation and to a lesser extent post-fire successional stage are important drivers of seedling performance while the direct effect of climate warming is not. This suggests that tree regeneration in future forests may be more responsive to changes in understory vegetation or fire regime, e.g. indirectly caused by warming, than to direct or interactive effects of rising temperatures.},
	language = {English},
	urldate = {2024-03-26},
	journal = {Frontiers in Forests and Global Change},
	author = {Jessen, Maria-Theresa and Krab, Eveline J. and Lett, Signe and Nilsson, Marie-Charlotte and Teuber, Laurenz and Wardle, David A. and Dorrepaal, Ellen},
	month = may,
	year = {2023},
	note = {Publisher: Frontiers},
	keywords = {Climate Change, Forest regneration, Shrubs, Survival, forest fire, moss, plant functional group removal},
	pages = {1130532},
}

Survival and growth of tree seedlings are key processes of regeneration in forest ecosystems. However, little is known about how climate warming modulates seedling performance either directly or in interaction with understory vegetation and post-fire successional stages. We measured survival (over three years) and growth of seedlings of three tree species (Betula pubescens, Pinus sylvestris and Picea abies) in a full-factorial field experiment with passive warming and removal of two plant functional groups (feather moss and/or ericaceous shrubs) along a post-fire chronosequence in an unmanaged boreal forest. Warming had no effect on seedling survival over time or on relative biomass growth. Meanwhile, moss removal greatly increased seedling survival overall, while shrub removal cancelled this effect for B. pubescens seedlings. In addition, B. pubescens and P. sylvestris survival benefitted most from moss removal in old forests (\textgreater260 years since last fire disturbance). In contrast to survival, seedling growth was promoted by shrub removal for two out of three species, i.e., P. sylvestris and P. abies, meaning that seedling survival and growth are governed by different understory functional groups affecting seedling performance through different mechanism and modes of action. Our findings highlight that understory vegetation and to a lesser extent post-fire successional stage are important drivers of seedling performance while the direct effect of climate warming is not. This suggests that tree regeneration in future forests may be more responsive to changes in understory vegetation or fire regime, e.g. indirectly caused by warming, than to direct or interactive effects of rising temperatures.

@article{jerand_legacy_2023,
	title = {The legacy of ecological imperialism in the {Scandes}: {Earthworms} and their implications for {Arctic} research},
	volume = {55},
	issn = {1523-0430},
	shorttitle = {The legacy of ecological imperialism in the {Scandes}},
	url = {https://doi.org/10.1080/15230430.2023.2274650},
	doi = {10.1080/15230430.2023.2274650},
	abstract = {In the nineteenth century, numerous settlements were established in the alpine region of Fennoscandia (the Scandes), an area that later became a major international scene for Arctic research. Here we raise awareness of this era and show that earthworm-driven bioturbation in “pristine” soils around contemporary Arctic research infrastructure is caused by soil fauna left behind during early land use. We use soil preserved under an alpine settlement to highlight that soils were not bioturbated when the first house was built at a site where bioturbation is now widespread. A review of archived material with unique site-specific chronology constrained the onset of bioturbation to the post-1871 era. Our results suggest that small-scale land use introduced earthworms that now thrive far beyond the realms of former cultivated fields. The legacy of soil fauna from this example of “ecological imperialism” still lingers and should be considered when studying soils of the Scandes.},
	number = {1},
	urldate = {2024-03-26},
	journal = {Arctic, Antarctic, and Alpine Research},
	author = {Jerand, Philip and Klaminder, Jonatan and Linderholm, Johan},
	month = dec,
	year = {2023},
	note = {Publisher: Taylor \& Francis
\_eprint: https://doi.org/10.1080/15230430.2023.2274650},
	keywords = {Archaeology, bioturbation, historical sources, phosphate analysis, soil classification},
	pages = {2274650},
}

In the nineteenth century, numerous settlements were established in the alpine region of Fennoscandia (the Scandes), an area that later became a major international scene for Arctic research. Here we raise awareness of this era and show that earthworm-driven bioturbation in “pristine” soils around contemporary Arctic research infrastructure is caused by soil fauna left behind during early land use. We use soil preserved under an alpine settlement to highlight that soils were not bioturbated when the first house was built at a site where bioturbation is now widespread. A review of archived material with unique site-specific chronology constrained the onset of bioturbation to the post-1871 era. Our results suggest that small-scale land use introduced earthworms that now thrive far beyond the realms of former cultivated fields. The legacy of soil fauna from this example of “ecological imperialism” still lingers and should be considered when studying soils of the Scandes.

@article{hostens_drivers_2023,
	title = {The drivers of dark diversity in the {Scandinavian} mountains are metric-dependent},
	volume = {34},
	copyright = {© 2023 International Association for Vegetation Science.},
	issn = {1654-1103},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.13212},
	doi = {10.1111/jvs.13212},
	abstract = {Question Dark diversity refers to the set of species that are not observed in an area but could potentially occur based on suitable local environmental conditions. In this paper, we applied both niche-based and co-occurrence-based methods to estimate the dark diversity of vascular plant species in the subarctic mountains. We then aimed to unravel the drivers explaining (a) why some locations were missing relatively more suitable species than others, and (b) why certain plant species were more often absent from suitable locations than others. Location The Scandinavian mountains around Abisko, northern Sweden. Methods We calculated the dark diversity in 107 plots spread out across four mountain trails using four different methods: two co-occurrence-based (Beals’ index and the hypergeometric method) and two niche-based (the climatic niche model and climatic niche model followed by species-specific threshold). We then applied multiple Generalized Linear Mixed-Effects Models and General Linear Models to determine which habitat characteristics and species traits contributed the most to dark diversity. Results The study showed a notable divergence in the predicted drivers of dark diversity depending on the method used. Nevertheless, we can conclude that plot-level dark diversity was generally 17\% higher in areas at low elevations and 31\% higher in areas with a low species richness. Conclusion Our findings call for caution when interpreting statistical findings of dark-diversity estimates. Even so, all analyses point toward an important role for natural processes such as competitive dominance as the main driver of the spatial patterns found in dark diversity in the northern Scandes.},
	language = {en},
	number = {6},
	urldate = {2024-03-26},
	journal = {Journal of Vegetation Science},
	author = {Hostens, Lore and Van Meerbeek, Koenraad and Wiegmans, Dymphna and Larson, Keith and Lenoir, Jonathan and Clavel, Jan and Wedegärtner, Ronja and Pirée, Amber and Nijs, Ivan and Lembrechts, Jonas J.},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvs.13212},
	keywords = {Beals’ index, co-occurrence model, habitat characteristics, method comparison, niche model, plant diversity, plant ecology, plant traits, regional species pool},
	pages = {e13212},
}

Question Dark diversity refers to the set of species that are not observed in an area but could potentially occur based on suitable local environmental conditions. In this paper, we applied both niche-based and co-occurrence-based methods to estimate the dark diversity of vascular plant species in the subarctic mountains. We then aimed to unravel the drivers explaining (a) why some locations were missing relatively more suitable species than others, and (b) why certain plant species were more often absent from suitable locations than others. Location The Scandinavian mountains around Abisko, northern Sweden. Methods We calculated the dark diversity in 107 plots spread out across four mountain trails using four different methods: two co-occurrence-based (Beals’ index and the hypergeometric method) and two niche-based (the climatic niche model and climatic niche model followed by species-specific threshold). We then applied multiple Generalized Linear Mixed-Effects Models and General Linear Models to determine which habitat characteristics and species traits contributed the most to dark diversity. Results The study showed a notable divergence in the predicted drivers of dark diversity depending on the method used. Nevertheless, we can conclude that plot-level dark diversity was generally 17% higher in areas at low elevations and 31% higher in areas with a low species richness. Conclusion Our findings call for caution when interpreting statistical findings of dark-diversity estimates. Even so, all analyses point toward an important role for natural processes such as competitive dominance as the main driver of the spatial patterns found in dark diversity in the northern Scandes.

@article{ehnvall_landscape_2023,
	title = {Landscape constraints on mire lateral expansion},
	volume = {302},
	issn = {0277-3791},
	url = {https://www.sciencedirect.com/science/article/pii/S0277379123000094},
	doi = {10.1016/j.quascirev.2023.107961},
	abstract = {Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape.},
	urldate = {2024-03-26},
	journal = {Quaternary Science Reviews},
	author = {Ehnvall, Betty and Ratcliffe, Joshua L. and Bohlin, Elisabet and Nilsson, Mats B. and Öquist, Mats G. and Sponseller, Ryan A. and Grabs, Thomas},
	month = feb,
	year = {2023},
	keywords = {Boreal zone, Chronosequence, Holocene, Landscape ecology, Landscape wetness, Mire available areas, Mire lateral expansion, Non-linear, Peat accumulation},
	pages = {107961},
}

Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape.

@article{blume-werry_arctic_2023,
	title = {Arctic rooting depth distribution influences modelled carbon emissions but cannot be inferred from aboveground vegetation type},
	volume = {240},
	copyright = {© 2023 The Authors New Phytologist © 2023 New Phytologist Foundation},
	issn = {1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.18998},
	doi = {10.1111/nph.18998},
	abstract = {The distribution of roots throughout the soil drives depth-dependent plant–soil interactions and ecosystem processes, particularly in arctic tundra where plant biomass, is predominantly belowground. Vegetation is usually classified from aboveground, but it is unclear whether such classifications are suitable to estimate belowground attributes and their consequences, such as rooting depth distribution and its influence on carbon cycling. We performed a meta-analysis of 55 published arctic rooting depth profiles, testing for differences both between distributions based on aboveground vegetation types (Graminoid, Wetland, Erect-shrub, and Prostrate-shrub tundra) and between ‘Root Profile Types’ for which we defined three representative and contrasting clusters. We further analyzed potential impacts of these different rooting depth distributions on rhizosphere priming-induced carbon losses from tundra soils. Rooting depth distribution hardly differed between aboveground vegetation types but varied between Root Profile Types. Accordingly, modelled priming-induced carbon emissions were similar between aboveground vegetation types when they were applied to the entire tundra, but ranged from 7.2 to 17.6 Pg C cumulative emissions until 2100 between individual Root Profile Types. Variations in rooting depth distribution are important for the circumpolar tundra carbon-climate feedback but can currently not be inferred adequately from aboveground vegetation type classifications.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {New Phytologist},
	author = {Blume-Werry, Gesche and Dorrepaal, Ellen and Keuper, Frida and Kummu, Matti and Wild, Birgit and Weedon, James T.},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.18998},
	keywords = {\#nosource, arctic tundra, permafrost, plant–soil interactions, rhizosphere priming effect, root biomass, root vertical distribution strategies, rooting depth},
	pages = {502--514},
}

The distribution of roots throughout the soil drives depth-dependent plant–soil interactions and ecosystem processes, particularly in arctic tundra where plant biomass, is predominantly belowground. Vegetation is usually classified from aboveground, but it is unclear whether such classifications are suitable to estimate belowground attributes and their consequences, such as rooting depth distribution and its influence on carbon cycling. We performed a meta-analysis of 55 published arctic rooting depth profiles, testing for differences both between distributions based on aboveground vegetation types (Graminoid, Wetland, Erect-shrub, and Prostrate-shrub tundra) and between ‘Root Profile Types’ for which we defined three representative and contrasting clusters. We further analyzed potential impacts of these different rooting depth distributions on rhizosphere priming-induced carbon losses from tundra soils. Rooting depth distribution hardly differed between aboveground vegetation types but varied between Root Profile Types. Accordingly, modelled priming-induced carbon emissions were similar between aboveground vegetation types when they were applied to the entire tundra, but ranged from 7.2 to 17.6 Pg C cumulative emissions until 2100 between individual Root Profile Types. Variations in rooting depth distribution are important for the circumpolar tundra carbon-climate feedback but can currently not be inferred adequately from aboveground vegetation type classifications.

@article{sjogersten_optical_2023,
	title = {Optical and radar {Earth} observation data for upscaling methane emissions linked to permafrost degradation in sub-{Arctic} peatlands in northern {Sweden}},
	volume = {20},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-218475},
	doi = {10.5194/bg-20-4221-2023},
	abstract = {Permafrost thaw in Arctic regions is increasing methane (CH4) emissions into the atmosphere, but quantification of such emissions is difficult given the large and remote areas impacted. Hence, Eart ...},
	language = {eng},
	number = {20},
	urldate = {2024-03-26},
	journal = {Biogeosciences},
	author = {Sjögersten, Sofie and Ledger, Martha and Siewert, Matthias B. and De La Barreda-Bautista, Betsabé and Sowter, Andrew and Gee, David and Foody, Giles and Boyd, Doreen S.},
	year = {2023},
	note = {Publisher: Copernicus Publications},
	pages = {4221--4239},
}

Permafrost thaw in Arctic regions is increasing methane (CH4) emissions into the atmosphere, but quantification of such emissions is difficult given the large and remote areas impacted. Hence, Eart ...

@article{spitzer_as_2023,
	title = {As a permafrost ecosystem warms, plant community traits become more acquisitive},
	volume = {240},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-215375},
	doi = {10.1111/nph.19286},
	abstract = {As a permafrost ecosystem warms, plant community traits become more acquisitive},
	language = {eng},
	number = {5},
	urldate = {2024-03-26},
	journal = {New Phytologist},
	author = {Spitzer, Clydecia M. and Blume-Werry, Gesche},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {1712--1713},
}

As a permafrost ecosystem warms, plant community traits become more acquisitive

@article{malyshev_warming_2023,
	title = {Warming nondormant tree roots advances aboveground spring phenology in temperate trees},
	volume = {240},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-216213},
	doi = {10.1111/nph.19304},
	abstract = {Climate warming advances the onset of tree growth in spring, but above- and belowground phenology are not always synchronized. These differences in growth responses may result from differences in r ...},
	language = {eng},
	number = {6},
	urldate = {2024-03-26},
	journal = {New Phytologist},
	author = {Malyshev, Andrey V. and Blume-Werry, Gesche and Spiller, Ophelia and Smiljanić, Marko and Weigel, Robert and Kolb, Alexander and Nze, Byron Ye and Märker, Frederik and Sommer, Freymuth Carl-Fried Johannes and Kinley, Kinley and Ziegler, Jan and Pasang, Pasang and Mahara, Robert and Joshi, Silviya and Heinsohn, Vincent and Kreyling, Juergen},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {2276--2287},
}

Climate warming advances the onset of tree growth in spring, but above- and belowground phenology are not always synchronized. These differences in growth responses may result from differences in r ...

@article{makoto_how_2023,
	title = {How do leaf functional traits and age influence the maximum rooting depth of trees?},
	volume = {142},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-210225},
	doi = {10.1007/s10342-023-01585-6},
	abstract = {Maximum rooting depth is a key functional trait to increase the fitness of trees and also influences terrestrial ecosystem processes. Despite its importance, the drivers of the interspecific variat ...},
	language = {eng},
	number = {5},
	urldate = {2024-03-26},
	journal = {European Journal of Forest Research},
	author = {Makoto, Kobayashi and Kitagawa, Ryo and Blume-Werry, Gesche},
	year = {2023},
	note = {Publisher: Springer Science+Business Media B.V.},
	pages = {1197--1206},
}

Maximum rooting depth is a key functional trait to increase the fitness of trees and also influences terrestrial ecosystem processes. Despite its importance, the drivers of the interspecific variat ...

@article{hollister_review_2023,
	title = {A review of open top chamber ({OTC}) performance across the {ITEX} {Network}},
	volume = {9},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-212056},
	doi = {10.1139/as-2022-0030},
	abstract = {Open top chambers (OTCs) were adopted as the recommended warmingmechanism by the International Tundra Experiment network in the early 1990s. Since then, OTCs have been deployed across the globe. Hu ...},
	language = {eng},
	number = {2},
	urldate = {2024-03-26},
	journal = {Arctic Science},
	author = {Hollister, Robert D. and Elphinstone, Cassandra and Henry, Greg H. R. and Bjorkman, Anne D. and Klanderud, Kari and Björk, Robert G. and Björkman, Mats P. and Bokhorst, Stef and Carbognani, Michele and Cooper, Elisabeth J. and Dorrepaal, Ellen and Elmendorf, Sarah C. and Fetcher, Ned and Gallois, Elise C. and Guoðmundsson, Jón and Healey, Nathan C. and Jónsdóttir, Ingibjörg Svala and Klarenberg, Ingeborg J. and Oberbauer, Steven F. and Macek, Petr and May, Jeremy L. and Mereghetti, Alessandro and Molau, Ulf and Petraglia, Alessandro and Rinnan, Riikka and Rixen, Christian and Wookey, Philip A.},
	year = {2023},
	note = {Publisher: Canadian Science Publishing},
	pages = {331--344},
}

Open top chambers (OTCs) were adopted as the recommended warmingmechanism by the International Tundra Experiment network in the early 1990s. Since then, OTCs have been deployed across the globe. Hu ...

@article{windirsch_impacts_2023,
	title = {Impacts of reindeer on soil carbon storage in the seasonally frozen ground of northern {Finland} : a pilot study},
	volume = {28},
	shorttitle = {Impacts of reindeer on soil carbon storage in the seasonally frozen ground of northern {Finland}},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-215354},
	abstract = {To test the effect of reindeer husbandry on soil carbon storage of seasonally frozen ground, we analysed soil and vegetation properties in peatlands and mixed pine and mountain birch forests. We an ...},
	language = {eng},
	number = {1-6},
	urldate = {2024-03-26},
	journal = {Boreal environment research},
	author = {Windirsch, Torben and Forbes, Bruce C. and Grosse, Guido and Wolter, Juliane and Stark, Sari and Treat, Claire and Ulrich, Mathias and Fuchs, Matthias and Olofsson, Johan and Kumpula, Timo and Macias-Fauria, Marc and Strauss, Jens},
	year = {2023},
	note = {Publisher: Finish Environment Institute},
	keywords = {⛔ No DOI found},
	pages = {207--226},
}

To test the effect of reindeer husbandry on soil carbon storage of seasonally frozen ground, we analysed soil and vegetation properties in peatlands and mixed pine and mountain birch forests. We an ...

@article{stanley_grimedb_2023,
	title = {{GRiMeDB} : the global river methane database of concentrations and fluxes},
	volume = {15},
	shorttitle = {{GRiMeDB}},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-215374},
	doi = {10.5194/essd-15-2879-2023},
	abstract = {Despite their small spatial extent, fluvial ecosystems play a significant role in processing and transporting carbon in aquatic networks, which results in substantial emission of methane (CH4) into ...},
	language = {eng},
	number = {7},
	urldate = {2024-03-26},
	journal = {Earth System Science Data},
	author = {Stanley, Emily H. and Loken, Luke C. and Casson, Nora J. and Oliver, Samantha K. and Sponseller, Ryan A. and Wallin, Marcus B. and Zhang, Liwei and Rocher-Ros, Gerard},
	year = {2023},
	note = {Publisher: Copernicus Publications},
	pages = {2879--2926},
}

Despite their small spatial extent, fluvial ecosystems play a significant role in processing and transporting carbon in aquatic networks, which results in substantial emission of methane (CH4) into ...

@article{rocher-ros_global_2023,
	title = {Global methane emissions from rivers and streams},
	volume = {621},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-213705},
	doi = {10.1038/s41586-023-06344-6},
	abstract = {Methane (CH4) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH4 emissions fro ...},
	language = {eng},
	number = {7979},
	urldate = {2024-03-26},
	journal = {Nature},
	author = {Rocher-Ros, Gerard and Stanley, Emily H. and Loken, Luke C. and Casson, Nora J. and Raymond, Peter A. and Liu, Shaoda and Amatulli, Giuseppe and Sponseller, Ryan A.},
	year = {2023},
	note = {Publisher: Springer Nature},
	pages = {530--535},
}

Methane (CH4) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH4 emissions fro ...

@article{rehn_long-term_2023,
	title = {Long-term changes in dissolved inorganic carbon across boreal streams caused by altered hydrology},
	volume = {68},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-201749},
	doi = {10.1002/lno.12282},
	abstract = {A major challenge for predicting future landscape carbon (C) balances is to understand how environmental changes affect the transfer of C from soils to surface waters. Here, we evaluated 14 yr (200 ...},
	language = {eng},
	number = {2},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Rehn, Lukas and Sponseller, Ryan A. and Laudon, Hjalmar and Wallin, Marcus B.},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {409--423},
}

A major challenge for predicting future landscape carbon (C) balances is to understand how environmental changes affect the transfer of C from soils to surface waters. Here, we evaluated 14 yr (200 ...

@article{menden-deuer_cascading_2023,
	title = {Cascading, interactive, and indirect effects of climate change on aquatic communities, habitats, and ecosystems},
	volume = {68},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-212501},
	doi = {10.1002/lno.12384},
	abstract = {Climate-change is rapidly and intensively altering aquatic communities and habitats. While previous work has focused on direct effects of potential drivers, indirect and interactive effects on orga ...},
	language = {eng},
	number = {S1},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Menden-Deuer, Susanne and Mullarney, Julia C. and Boersma, Maarten and Grossart, Hans-Peter and Sponseller, Ryan A. and Woodin, Sarah Ann},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {S1--S7},
}

Climate-change is rapidly and intensively altering aquatic communities and habitats. While previous work has focused on direct effects of potential drivers, indirect and interactive effects on orga ...

@article{mckie_long-established_2023,
	title = {A long-established invasive species alters the functioning of benthic biofilms in lakes},
	volume = {68},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-214759},
	doi = {10.1111/fwb.14175},
	abstract = {Invasive species often transform environmental conditions, exclude native species and alter ecosystem functioning, including key ecosystem processes underpinning nutrient and energy cycles. However ...},
	language = {eng},
	number = {12},
	urldate = {2024-03-26},
	journal = {Freshwater Biology},
	author = {McKie, Brendan G. and Tattersdill, Kristina and Ecke, Frauke and Frainer, André and Sponseller, Ryan A.},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {2068--2083},
}

Invasive species often transform environmental conditions, exclude native species and alter ecosystem functioning, including key ecosystem processes underpinning nutrient and energy cycles. However ...

@article{lupon_groundwater-stream_2023,
	title = {Groundwater-stream connections shape the spatial pattern and rates of aquatic metabolism},
	volume = {8},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-204765},
	doi = {10.1002/lol2.10305},
	abstract = {A longstanding challenge in stream ecology is to understand how landscape configuration organizes spatial patterns of ecosystem function via lateral groundwater connections. We combined laboratory  ...},
	language = {eng},
	number = {2},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography Letters},
	author = {Lupon, Anna and Gómez-Gener, Lluís and Fork, Megan L. and Laudon, Hjalmar and Martí, Eugènia and Lidberg, William and Sponseller, Ryan A.},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {350--358},
}

A longstanding challenge in stream ecology is to understand how landscape configuration organizes spatial patterns of ecosystem function via lateral groundwater connections. We combined laboratory ...

@article{isles_widespread_2023,
	title = {Widespread synchrony in phosphorus concentrations in northern lakes linked to winter temperature and summer precipitation},
	volume = {8},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-205739},
	doi = {10.1002/lol2.10318},
	abstract = {In recent years, unexplained declines in lake total phosphorus (TP) concentrations have been observed at northern latitudes (\> 42°N latitude) where most of the world's lakes are found. We compil ...},
	language = {eng},
	number = {4},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography Letters},
	author = {Isles, Peter D. F. and Creed, Irena F. and Hessen, Dag O. and Kortelainen, Pirkko and Paterson, Michael and Pomati, Francesco and Rusak, James A. and Vuorenmaa, Jussi and Bergström, Ann-Kristin},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {639--648},
}

In recent years, unexplained declines in lake total phosphorus (TP) concentrations have been observed at northern latitudes (> 42°N latitude) where most of the world's lakes are found. We compil ...

@article{callisto_puts_contrasting_2023,
	title = {Contrasting impacts of warming and browning on periphyton},
	volume = {8},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-205740},
	doi = {10.1002/lol2.10317},
	abstract = {We tested interactive effects of warming (+2°C) and browning on periphyton accrual and pigment composition when grown on a synthetic substrate (plastic strips) in the euphotic zone of 16 experiment ...},
	language = {eng},
	number = {4},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography Letters},
	author = {Callisto Puts, Isolde and Ask, Jenny and Myrstener, Maria and Bergström, Ann-Kristin},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {628--638},
}

We tested interactive effects of warming (+2°C) and browning on periphyton accrual and pigment composition when grown on a synthetic substrate (plastic strips) in the euphotic zone of 16 experiment ...

@article{corman_response_2023,
	title = {Response of lake metabolism to catchment inputs inferred using high-frequency lake and stream data from across the northern hemisphere},
	volume = {68},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-216880},
	doi = {10.1002/lno.12449},
	abstract = {In lakes, the rates of gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are often controlled by resource availability. Herein, we explore how catchment  ...},
	language = {eng},
	number = {12},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Corman, Jessica R. and Zwart, Jacob A. and Klug, Jennifer and Bruesewitz, Denise A. and de Eyto, Elvira and Klaus, Marcus and Knoll, Lesley B. and Rusak, James A. and Vanni, Michael J. and Alfonso, María Belén and Fernandez, Rocio Luz and Yao, Huaxia and Austnes, Kari and Couture, Raoul-Marie and de Wit, Heleen A. and Karlsson, Jan and Laas, Alo},
	year = {2023},
	note = {Publisher: John Wiley \& Sons},
	pages = {2617--2631},
}

In lakes, the rates of gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are often controlled by resource availability. Herein, we explore how catchment ...

@phdthesis{norman_lake_2023,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Lake bathymetry as driver of salmonid population size structure and biomass},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203635},
	abstract = {Most fish species undergo ontogenetic niche shifts from feeding on pelagic zooplankton, to larger benthic invertebrates and in some cases also to fish. These ontogenetic niche shifts have strong im ...},
	language = {eng},
	urldate = {2023-07-25},
	school = {Umeå University},
	author = {Norman, Sven},
	collaborator = {Byström, Pär and Nilsson, Karin A. and Karlsson, Jan},
	year = {2023},
	note = {Publisher: Umeå universitet},
	keywords = {⛔ No DOI found},
}

Most fish species undergo ontogenetic niche shifts from feeding on pelagic zooplankton, to larger benthic invertebrates and in some cases also to fish. These ontogenetic niche shifts have strong im ...

@article{cantwell-jones_mapping_2023,
	title = {Mapping trait versus species turnover reveals spatiotemporal variation in functional redundancy and network robustness in a plant-pollinator community},
	volume = {37},
	issn = {0269-8463},
	url = {https://doi.org/10.1111/1365-2435.14253},
	doi = {10.1111/1365-2435.14253},
	abstract = {Abstract Functional overlap among species (redundancy) is considered important in shaping competitive and mutualistic interactions that determine how communities respond to environmental change. Most studies view functional redundancy as static, yet traits within species?which ultimately shape functional redundancy?can vary over seasonal or spatial gradients. We therefore have limited understanding of how trait turnover within and between species could lead to changes in functional redundancy or how loss of traits could differentially impact mutualistic interactions depending on where and when the interactions occur in space and time. Using an Arctic bumblebee community as a case study, and 1277 individual measures from 14 species over three annual seasons, we quantified how inter- and intraspecific body-size turnover compared to species turnover with elevation and over the season. Coupling every individual and their trait with a plant visitation, we investigated how grouping individuals by a morphological trait or by species identity altered our assessment of network structure and how this differed in space and time. Finally, we tested how the sensitivity of the network in space and time differed when simulating extinction of nodes representing either morphological trait similarity or traditional species groups. This allowed us to explore the degree to which trait-based groups increase or decrease interaction redundancy relative to species-based nodes. We found that (i) groups of taxonomically and morphologically similar bees turn over in space and time independently from each other, with trait turnover being larger over the season; (ii) networks composed of nodes representing species versus morphologically similar bees were structured differently; and (iii) simulated loss of bee trait groups caused faster coextinction of bumblebee species and flowering plants than when bee taxonomic groups were lost. Crucially, the magnitude of these effects varied in space and time, highlighting the importance of considering spatiotemporal context when studying the relative importance of taxonomic and trait contributions to interaction network architecture. Our finding that functional redundancy varies spatiotemporally demonstrates how considering the traits of individuals within networks is needed to understand the impacts of environmental variation and extinction on ecosystem functioning and resilience. Read the free Plain Language Summary for this article on the Journal blog.},
	number = {3},
	urldate = {2023-07-22},
	journal = {Functional Ecology},
	author = {Cantwell-Jones, Aoife and Larson, Keith and Ward, Alan and Bates, Olivia K. and Cox, Tara and Gibbons, Charlotte and Richardson, Ryan and Al-Hayali, Abdullah M. R. and Svedin, Johan and Aronsson, Max and Brannlund, Frida and Tylianakis, Jason M. and Johansson, Jacob and Gill, Richard J.},
	month = mar,
	year = {2023},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Arctic, Bombus community, altitudinal gradient, beta diversity, bumblebees, connectance, ecological network, modularity, pollination, sequential extinction, thermal cline},
	pages = {748--762},
}

Abstract Functional overlap among species (redundancy) is considered important in shaping competitive and mutualistic interactions that determine how communities respond to environmental change. Most studies view functional redundancy as static, yet traits within species?which ultimately shape functional redundancy?can vary over seasonal or spatial gradients. We therefore have limited understanding of how trait turnover within and between species could lead to changes in functional redundancy or how loss of traits could differentially impact mutualistic interactions depending on where and when the interactions occur in space and time. Using an Arctic bumblebee community as a case study, and 1277 individual measures from 14 species over three annual seasons, we quantified how inter- and intraspecific body-size turnover compared to species turnover with elevation and over the season. Coupling every individual and their trait with a plant visitation, we investigated how grouping individuals by a morphological trait or by species identity altered our assessment of network structure and how this differed in space and time. Finally, we tested how the sensitivity of the network in space and time differed when simulating extinction of nodes representing either morphological trait similarity or traditional species groups. This allowed us to explore the degree to which trait-based groups increase or decrease interaction redundancy relative to species-based nodes. We found that (i) groups of taxonomically and morphologically similar bees turn over in space and time independently from each other, with trait turnover being larger over the season; (ii) networks composed of nodes representing species versus morphologically similar bees were structured differently; and (iii) simulated loss of bee trait groups caused faster coextinction of bumblebee species and flowering plants than when bee taxonomic groups were lost. Crucially, the magnitude of these effects varied in space and time, highlighting the importance of considering spatiotemporal context when studying the relative importance of taxonomic and trait contributions to interaction network architecture. Our finding that functional redundancy varies spatiotemporally demonstrates how considering the traits of individuals within networks is needed to understand the impacts of environmental variation and extinction on ecosystem functioning and resilience. Read the free Plain Language Summary for this article on the Journal blog.

@article{fischer_wide-spread_2023,
	title = {Wide-spread microbial sulfate reduction ({MSR}) in northern {European} freshwater systems: {Drivers}, magnitudes and seasonality},
	volume = {889},
	issn = {0048-9697},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969723023859},
	doi = {10.1016/j.scitotenv.2023.163764},
	abstract = {Microbial sulfate reduction (MSR), which transforms sulfate into sulfide through the consumption of organic matter, is an integral part of sulfur and carbon cycling. Yet, the knowledge on MSR magnitudes is limited and mostly restricted to snap-shot conditions in specific surface water bodies. Potential impacts of MSR have consequently been unaccounted for, e.g., in regional or global weathering budgets. Here, we synthesize results from previous studies on sulfur isotope dynamics in stream water samples and apply a sulfur isotopic fractionation and mixing scheme combined with Monte Carlo simulations to derive MSR in entire hydrological catchments. This allowed comparison of magnitudes both within and between five study areas located between southern Sweden and the Kola Peninsula, Russia. Our results showed that the freshwater MSR ranged from 0 to 79 \% (interquartile range of 19 percentage units) locally within the catchments, with average values from 2 to 28 \% between the catchments, displaying a non-negligible catchment-average value of 13 \%. The combined abundance or deficiency of several landscape elements (e.g., the areal percentage of forest and lakes/wetlands) were found to indicate relatively well whether or not catchment-scale MSR would be high. A regression analysis showed specifically that average slope was the individual element that best reflected the MSR magnitude, both at sub-catchment scale and between the different study areas. However, the regression results of individual parameters were generally weak. The MSR-values additionally showed differences between seasons, in particular in wetland/lake dominated catchments. Here MSR was high during the spring flood, which is consistent with the mobilization of water that under low-flow winter periods have developed the needed anoxic conditions for sulfate-reducing microorganisms. This study presents for the first time compelling evidence from multiple catchments of wide-spread MSR at levels slightly above 10 \%, implying that the terrestrial pyrite oxidation may be underestimated in global weathering budgets.},
	journal = {Science of The Total Environment},
	author = {Fischer, Sandra and Mörth, Carl-Magnus and Rosqvist, Gunhild and Giesler, Reiner and Jarsjö, Jerker},
	month = sep,
	year = {2023},
	keywords = {Bacterial sulfate reduction, Global weathering budget, Indicators, Sulfur isotopes},
	pages = {163764},
}

Microbial sulfate reduction (MSR), which transforms sulfate into sulfide through the consumption of organic matter, is an integral part of sulfur and carbon cycling. Yet, the knowledge on MSR magnitudes is limited and mostly restricted to snap-shot conditions in specific surface water bodies. Potential impacts of MSR have consequently been unaccounted for, e.g., in regional or global weathering budgets. Here, we synthesize results from previous studies on sulfur isotope dynamics in stream water samples and apply a sulfur isotopic fractionation and mixing scheme combined with Monte Carlo simulations to derive MSR in entire hydrological catchments. This allowed comparison of magnitudes both within and between five study areas located between southern Sweden and the Kola Peninsula, Russia. Our results showed that the freshwater MSR ranged from 0 to 79 % (interquartile range of 19 percentage units) locally within the catchments, with average values from 2 to 28 % between the catchments, displaying a non-negligible catchment-average value of 13 %. The combined abundance or deficiency of several landscape elements (e.g., the areal percentage of forest and lakes/wetlands) were found to indicate relatively well whether or not catchment-scale MSR would be high. A regression analysis showed specifically that average slope was the individual element that best reflected the MSR magnitude, both at sub-catchment scale and between the different study areas. However, the regression results of individual parameters were generally weak. The MSR-values additionally showed differences between seasons, in particular in wetland/lake dominated catchments. Here MSR was high during the spring flood, which is consistent with the mobilization of water that under low-flow winter periods have developed the needed anoxic conditions for sulfate-reducing microorganisms. This study presents for the first time compelling evidence from multiple catchments of wide-spread MSR at levels slightly above 10 %, implying that the terrestrial pyrite oxidation may be underestimated in global weathering budgets.

@article{blume-werry_ideas_2023,
	title = {Ideas and perspectives: {Alleviation} of functional limitations by soil organisms is key to climate feedbacks from arctic soils},
	volume = {20},
	url = {https://bg.copernicus.org/articles/20/1979/2023/},
	doi = {10.5194/bg-20-1979-2023},
	number = {10},
	journal = {Biogeosciences},
	author = {Blume-Werry, G. and Klaminder, J. and Krab, E. J. and Monteux, S.},
	year = {2023},
	pages = {1979--1990},
}

@article{rodriguez-martinez_topological_2023,
	title = {The topological nature of tag jumping in environmental {DNA} metabarcoding studies},
	volume = {23},
	issn = {1755-098X},
	url = {https://doi.org/10.1111/1755-0998.13745},
	doi = {10.1111/1755-0998.13745},
	abstract = {Abstract Metabarcoding of environmental DNA constitutes a state-of-the-art tool for environmental studies. One fundamental principle implicit in most metabarcoding studies is that individual sample amplicons can still be identified after being pooled with others?based on their unique combinations of tags?during the so-called demultiplexing step that follows sequencing. Nevertheless, it has been recognized that tags can sometimes be changed (i.e., tag jumping), which ultimately leads to sample crosstalk. Here, using four DNA metabarcoding data sets derived from the analysis of soils and sediments, we show that tag jumping follows very specific and systematic patterns. Specifically, we find a strong correlation between the number of reads in blank samples and their topological position in the tag matrix (described by vertical and horizontal vectors). This observed spatial pattern of artefactual sequences could be explained by polymerase activity, which leads to the exchange of the 3? tag of single stranded tagged sequences through the formation of heteroduplexes with mixed barcodes. Importantly, tag jumping substantially distorted our data sets?despite our use of methods suggested to minimize this error. We developed a topological model to estimate the noise based on the counts in our blanks, which suggested that 40\%?80\% of the taxa in our soil and sedimentary samples were likely false positives introduced through tag jumping. We highlight that the amount of false positive detections caused by tag jumping strongly biased our community analyses.},
	number = {3},
	urldate = {2023-07-22},
	journal = {Molecular Ecology Resources},
	author = {Rodriguez-Martinez, Saul and Klaminder, Jonatan and Morlock, Marina A. and Dalén, Love and Huang, Doreen Yu-Tuan},
	month = apr,
	year = {2023},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {a-DNA, detection limits, e-DNA, false positive, index hopping, sample crosstalk},
	pages = {621--631},
}

Abstract Metabarcoding of environmental DNA constitutes a state-of-the-art tool for environmental studies. One fundamental principle implicit in most metabarcoding studies is that individual sample amplicons can still be identified after being pooled with others?based on their unique combinations of tags?during the so-called demultiplexing step that follows sequencing. Nevertheless, it has been recognized that tags can sometimes be changed (i.e., tag jumping), which ultimately leads to sample crosstalk. Here, using four DNA metabarcoding data sets derived from the analysis of soils and sediments, we show that tag jumping follows very specific and systematic patterns. Specifically, we find a strong correlation between the number of reads in blank samples and their topological position in the tag matrix (described by vertical and horizontal vectors). This observed spatial pattern of artefactual sequences could be explained by polymerase activity, which leads to the exchange of the 3? tag of single stranded tagged sequences through the formation of heteroduplexes with mixed barcodes. Importantly, tag jumping substantially distorted our data sets?despite our use of methods suggested to minimize this error. We developed a topological model to estimate the noise based on the counts in our blanks, which suggested that 40%?80% of the taxa in our soil and sedimentary samples were likely false positives introduced through tag jumping. We highlight that the amount of false positive detections caused by tag jumping strongly biased our community analyses.

@article{klaminder_holes_2023,
	title = {Holes in the tundra: {Invasive} earthworms alter soil structure and moisture in tundra soils},
	volume = {859},
	issn = {0048-9697},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969722072254},
	doi = {10.1016/j.scitotenv.2022.160125},
	abstract = {Human introductions have resulted in earthworms establishing in the Arctic, species known to cause cascading ecosystem change. However, few quantitative outdoor experiments have been performed that describe how these soil modifying earthworms are reshaping structures in tundra soils. In this study, we used three-dimensional (3-D) X-ray images of soil cores (approximately 10 cm diameter, 20 cm height, N = 48) to assess how earthworms (Aporrectodea sp. and Lumbricus sp.) affect soil structure and macropore networks in an outdoor mesocosm experiment that lasted four summers. Effects were assessed in both shrub-dominated (heath) and herb-dominated (meadow) tundra. Earthworms almost doubled the macroporosity in meadow soils and tripled macroporosity in heath. Interestingly, the fractal dimension of macropores decreased in response to earthworm burrowing in both systems, indicating that the presence of earthworms reduced the geometric complexity in comparison to other pore-generating processes active in the tundra. Observed effects on soil structure occurred along with a dramatically reduced soil moisture content, which was observed the first winter after earthworm introduction in the meadow. Our findings suggest that predictions of future changes in vegetation and soil carbon pools in the Arctic should include major impacts on soil properties that earthworms induce.},
	journal = {Science of The Total Environment},
	author = {Klaminder, J. and Krab, E.J. and Larsbo, M. and Jonsson, H. and Fransson, J. and Koestel, J.},
	month = feb,
	year = {2023},
	keywords = {3D, Abisko, Bioturbation, Heath, Long-term, Meadow, Soil-mixing},
	pages = {160125},
}

Human introductions have resulted in earthworms establishing in the Arctic, species known to cause cascading ecosystem change. However, few quantitative outdoor experiments have been performed that describe how these soil modifying earthworms are reshaping structures in tundra soils. In this study, we used three-dimensional (3-D) X-ray images of soil cores (approximately 10 cm diameter, 20 cm height, N = 48) to assess how earthworms (Aporrectodea sp. and Lumbricus sp.) affect soil structure and macropore networks in an outdoor mesocosm experiment that lasted four summers. Effects were assessed in both shrub-dominated (heath) and herb-dominated (meadow) tundra. Earthworms almost doubled the macroporosity in meadow soils and tripled macroporosity in heath. Interestingly, the fractal dimension of macropores decreased in response to earthworm burrowing in both systems, indicating that the presence of earthworms reduced the geometric complexity in comparison to other pore-generating processes active in the tundra. Observed effects on soil structure occurred along with a dramatically reduced soil moisture content, which was observed the first winter after earthworm introduction in the meadow. Our findings suggest that predictions of future changes in vegetation and soil carbon pools in the Arctic should include major impacts on soil properties that earthworms induce.

@article{ehnvall_catchment_2023,
	title = {Catchment characteristics control boreal mire nutrient regime and vegetation patterns over {\textasciitilde}5000 years of landscape development},
	volume = {895},
	issn = {0048-9697},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969723037555},
	doi = {10.1016/j.scitotenv.2023.165132},
	abstract = {Vegetation holds the key to many properties that make natural mires unique, such as surface microtopography, high biodiversity values, effective carbon sequestration and regulation of water and nutrient fluxes across the landscape. Despite this, landscape controls behind mire vegetation patterns have previously been poorly described at large spatial scales, which limits the understanding of basic drivers underpinning mire ecosystem services. We studied catchment controls on mire nutrient regimes and vegetation patterns using a geographically constrained natural mire chronosequence along the isostatically rising coastline in Northern Sweden. By comparing mires of different ages, we can partition vegetation patterns caused by long-term mire succession ({\textless}5000 years) and present-day vegetation responses to catchment eco-hydrological settings. We used the remote sensing based normalized difference vegetation index (NDVI) to describe mire vegetation and combined peat physicochemical measures with catchment properties to identify the most important factors that determine mire NDVI. We found strong evidence that mire NDVI depends on nutrient inputs from the catchment area or underlying mineral soil, especially concerning phosphorus and potassium concentrations. Steep mire and catchment slopes, dry conditions and large catchment areas relative to mire areas were associated with higher NDVI. We also found long-term successional patterns, with lower NDVI in older mires. Importantly, the NDVI should be used to describe mire vegetation patterns in open mires if the focus is on surface vegetation, since the canopy cover in tree-covered mires completely dominated the NDVI signal. With our study approach, we can quantitatively describe the connection between landscape properties and mire nutrient regime. Our results confirm that mire vegetation responds to the upslope catchment area, but importantly, also suggest that mire and catchment aging can override the role of catchment influence. This effect was clear across mires of all ages, but was strongest in younger mires.},
	journal = {Science of The Total Environment},
	author = {Ehnvall, Betty and Ågren, Anneli M. and Nilsson, Mats B. and Ratcliffe, Joshua L. and Noumonvi, Koffi Dodji and Peichl, Matthias and Lidberg, William and Giesler, Reiner and Mörth, Carl-Magnus and Öquist, Mats G.},
	month = oct,
	year = {2023},
	keywords = {\#nosource, Catchment support, Chronosequence, Holocene, Landscape ecology, NDVI},
	pages = {165132},
}

Vegetation holds the key to many properties that make natural mires unique, such as surface microtopography, high biodiversity values, effective carbon sequestration and regulation of water and nutrient fluxes across the landscape. Despite this, landscape controls behind mire vegetation patterns have previously been poorly described at large spatial scales, which limits the understanding of basic drivers underpinning mire ecosystem services. We studied catchment controls on mire nutrient regimes and vegetation patterns using a geographically constrained natural mire chronosequence along the isostatically rising coastline in Northern Sweden. By comparing mires of different ages, we can partition vegetation patterns caused by long-term mire succession (\textless5000 years) and present-day vegetation responses to catchment eco-hydrological settings. We used the remote sensing based normalized difference vegetation index (NDVI) to describe mire vegetation and combined peat physicochemical measures with catchment properties to identify the most important factors that determine mire NDVI. We found strong evidence that mire NDVI depends on nutrient inputs from the catchment area or underlying mineral soil, especially concerning phosphorus and potassium concentrations. Steep mire and catchment slopes, dry conditions and large catchment areas relative to mire areas were associated with higher NDVI. We also found long-term successional patterns, with lower NDVI in older mires. Importantly, the NDVI should be used to describe mire vegetation patterns in open mires if the focus is on surface vegetation, since the canopy cover in tree-covered mires completely dominated the NDVI signal. With our study approach, we can quantitatively describe the connection between landscape properties and mire nutrient regime. Our results confirm that mire vegetation responds to the upslope catchment area, but importantly, also suggest that mire and catchment aging can override the role of catchment influence. This effect was clear across mires of all ages, but was strongest in younger mires.

@article{reihill_synthesis_2023,
	title = {Synthesis of a {B}-{Antigen} {Hexasaccharide}, a {B}-{Lewis} b {Heptasaccharide} and {Glycoconjugates} {Thereof} to {Investigate} {Binding} {Properties} of {Helicobacter} pylori},
	volume = {29},
	url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202203672},
	doi = {10.1002/chem.202203672},
	abstract = {Abstract Infecting the stomach of almost 50 \% of people, Helicobacter pylori is a causative agent of gastritis, peptic ulcers and stomach cancers. Interactions between bacterial membrane-bound lectin, Blood group Antigen Binding Adhesin (BabA), and human blood group antigens are key in the initiation of infection. Herein, the synthesis of a B-antigen hexasaccharide (B6) and a B-Lewis b heptasaccharide (BLeb7) and Bovine Serum Albumin glycoconjugates thereof is reported to assess the binding properties and preferences of BabA from different strains. From a previously reported trisaccharide acceptor a versatile key Lacto-N-tetraose tetrasaccharide intermediate was synthesized, which allowed us to explore various routes to the final targets, either via initial introduction of fucosyl residues followed by introduction of the B-determinant or vice versa. The first approach proved unsuccessful, whereas the second afforded the target structures in good yields. Protein conjugation using isothiocyanate methodology allowed us to reach high glycan loadings (up to 23 per protein) to mimic multivalent displays encountered in Nature. Protein glycoconjugate inhibition binding studies were performed with H. pylori strains displaying high or low affinity for Lewis b hexasaccharide structures showing that the binding to the high affinity strain was reduced due to the presence of the B-determinant in the Bleb7-conjugates and further reduced by the absence of the Lewis fucose residue in the B6-conjugate.},
	number = {16},
	journal = {Chemistry – A European Journal},
	author = {Reihill, Mark and Fournière, Viviane and Cheallaigh, Aisling Ní and Edlund, Johan Olofsson and Miller, Gavin John and Borén, Thomas and Lahmann, Martina and Oscarson, Stefan},
	year = {2023},
	note = {\_eprint: https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.1002/chem.202203672},
	keywords = {\#nosource, B antigen, B-Lewis b, glycoconjugate, synthesis, thioglycoside},
	pages = {e202203672},
}

Abstract Infecting the stomach of almost 50 % of people, Helicobacter pylori is a causative agent of gastritis, peptic ulcers and stomach cancers. Interactions between bacterial membrane-bound lectin, Blood group Antigen Binding Adhesin (BabA), and human blood group antigens are key in the initiation of infection. Herein, the synthesis of a B-antigen hexasaccharide (B6) and a B-Lewis b heptasaccharide (BLeb7) and Bovine Serum Albumin glycoconjugates thereof is reported to assess the binding properties and preferences of BabA from different strains. From a previously reported trisaccharide acceptor a versatile key Lacto-N-tetraose tetrasaccharide intermediate was synthesized, which allowed us to explore various routes to the final targets, either via initial introduction of fucosyl residues followed by introduction of the B-determinant or vice versa. The first approach proved unsuccessful, whereas the second afforded the target structures in good yields. Protein conjugation using isothiocyanate methodology allowed us to reach high glycan loadings (up to 23 per protein) to mimic multivalent displays encountered in Nature. Protein glycoconjugate inhibition binding studies were performed with H. pylori strains displaying high or low affinity for Lewis b hexasaccharide structures showing that the binding to the high affinity strain was reduced due to the presence of the B-determinant in the Bleb7-conjugates and further reduced by the absence of the Lewis fucose residue in the B6-conjugate.

@article{ramirez_top-down_2023,
	title = {Top-down and bottom-up forces explain patch utilization by two deer species and forest recruitment},
	volume = {201},
	issn = {1432-1939},
	url = {https://doi.org/10.1007/s00442-022-05292-8},
	doi = {10.1007/s00442-022-05292-8},
	abstract = {Ungulates play an important role in temperate systems. Through their feeding behaviour, they can respond to vegetation by selecting patches or modify vegetation composition by herbivory. The degree in which they interact with vegetation can either reinforce landscape heterogeneity by creating disturbance or reduce heterogeneity in case of overbrowsing. This study evaluates how bottom-up (patch quality, structure), top-down forces (hunting, distance to village, forest edge) and deer features (feeding type, abundance) mediate patch utilization in a temperate forest and assess the implications of patch utilization and light on forest recruitment. Theory predicts that animals seek to maximize their energetic gains by food intake while minimizing the costs associated to foraging, such as the energy required for avoiding predators and exploiting resources. We focused on two deer species with contrasting feeding type: a browser (C. capreolus) and a mixed feeder (C. elaphus). We paired camera traps to vegetation sub-plots in ten forest sites in the Netherlands that widely ranged in deer abundance and landscape heterogeneity. Results showed that patch utilization is simultaneously explained by bottom-up, top-down forces and by deer abundance, as predicted by the safety-in-numbers hypothesis. Yet, forces best explaining patch utilization differed between deer species. Overall, higher patch utilization came with higher browsing, lower tree diversity and a large difference in forest composition: from a mix of broadleaves and conifers towards only conifers. We conclude that these two deer species, although living in the same area and belonging to the same guild, differentially perceive, interact with and shape their surrounding landscape.},
	number = {1},
	journal = {Oecologia},
	author = {Ramirez, J. Ignacio and Poorter, Lourens and Jansen, Patrick A. and den Ouden, Jan and Siewert, Matthias and Olofsson, Johan},
	month = jan,
	year = {2023},
	keywords = {\#nosource},
	pages = {229--240},
}

Ungulates play an important role in temperate systems. Through their feeding behaviour, they can respond to vegetation by selecting patches or modify vegetation composition by herbivory. The degree in which they interact with vegetation can either reinforce landscape heterogeneity by creating disturbance or reduce heterogeneity in case of overbrowsing. This study evaluates how bottom-up (patch quality, structure), top-down forces (hunting, distance to village, forest edge) and deer features (feeding type, abundance) mediate patch utilization in a temperate forest and assess the implications of patch utilization and light on forest recruitment. Theory predicts that animals seek to maximize their energetic gains by food intake while minimizing the costs associated to foraging, such as the energy required for avoiding predators and exploiting resources. We focused on two deer species with contrasting feeding type: a browser (C. capreolus) and a mixed feeder (C. elaphus). We paired camera traps to vegetation sub-plots in ten forest sites in the Netherlands that widely ranged in deer abundance and landscape heterogeneity. Results showed that patch utilization is simultaneously explained by bottom-up, top-down forces and by deer abundance, as predicted by the safety-in-numbers hypothesis. Yet, forces best explaining patch utilization differed between deer species. Overall, higher patch utilization came with higher browsing, lower tree diversity and a large difference in forest composition: from a mix of broadleaves and conifers towards only conifers. We conclude that these two deer species, although living in the same area and belonging to the same guild, differentially perceive, interact with and shape their surrounding landscape.

@article{castano_contrasting_2023,
	title = {Contrasting plant–soil–microbial feedbacks stabilize vegetation types and uncouple topsoil {C} and {N} stocks across a subarctic–alpine landscape},
	volume = {238},
	url = {https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.18679},
	doi = {10.1111/nph.18679},
	abstract = {Summary Global vegetation regimes vary in belowground carbon (C) and nitrogen (N) dynamics. However, disentangling large-scale climatic controls from the effects of intrinsic plant–soil–microbial feedbacks on belowground processes is challenging. In local gradients with similar pedo-climatic conditions, effects of plant–microbial feedbacks may be isolated from large-scale drivers. Across a subarctic–alpine mosaic of historic grazing fields and surrounding heath and birch forest, we evaluated whether vegetation-specific plant–microbial feedbacks involved contrasting N cycling characteristics and C and N stocks in the organic topsoil. We sequenced soil fungi, quantified functional genes within the inorganic N cycle, and measured 15N natural abundance. In grassland soils, large N stocks and low C : N ratios associated with fungal saprotrophs, archaeal ammonia oxidizers, and bacteria capable of respiratory ammonification, indicating maintained inorganic N cycling a century after abandoned reindeer grazing. Toward forest and heath, increasing abundance of mycorrhizal fungi co-occurred with transition to organic N cycling. However, ectomycorrhizal fungal decomposers correlated with small soil N and C stocks in forest, while root-associated ascomycetes associated with small N but large C stocks in heath, uncoupling C and N storage across vegetation types. We propose that contrasting, positive plant–microbial feedbacks stabilize vegetation trajectories, resulting in diverging soil C : N ratios at the landscape scale.},
	number = {6},
	journal = {New Phytologist},
	author = {Castaño, Carles and Hallin, Sara and Egelkraut, Dagmar and Lindahl, Björn D. and Olofsson, Johan and Clemmensen, Karina Engelbrecht},
	year = {2023},
	note = {\_eprint: https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.18679},
	keywords = {\#nosource, N cycling, forest, fungal saprotrophs, grassland, heathland, mycorrhiza, vegetation gradients},
	pages = {2621--2633},
}

Summary Global vegetation regimes vary in belowground carbon (C) and nitrogen (N) dynamics. However, disentangling large-scale climatic controls from the effects of intrinsic plant–soil–microbial feedbacks on belowground processes is challenging. In local gradients with similar pedo-climatic conditions, effects of plant–microbial feedbacks may be isolated from large-scale drivers. Across a subarctic–alpine mosaic of historic grazing fields and surrounding heath and birch forest, we evaluated whether vegetation-specific plant–microbial feedbacks involved contrasting N cycling characteristics and C and N stocks in the organic topsoil. We sequenced soil fungi, quantified functional genes within the inorganic N cycle, and measured 15N natural abundance. In grassland soils, large N stocks and low C : N ratios associated with fungal saprotrophs, archaeal ammonia oxidizers, and bacteria capable of respiratory ammonification, indicating maintained inorganic N cycling a century after abandoned reindeer grazing. Toward forest and heath, increasing abundance of mycorrhizal fungi co-occurred with transition to organic N cycling. However, ectomycorrhizal fungal decomposers correlated with small soil N and C stocks in forest, while root-associated ascomycetes associated with small N but large C stocks in heath, uncoupling C and N storage across vegetation types. We propose that contrasting, positive plant–microbial feedbacks stabilize vegetation trajectories, resulting in diverging soil C : N ratios at the landscape scale.

@article{sytiuk_linkages_2023,
	title = {Linkages between {Sphagnum} metabolites and peatland {CO2} uptake are sensitive to seasonality in warming trends},
	volume = {237},
	url = {https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.18601},
	doi = {10.1111/nph.18601},
	abstract = {Summary Plants produce a wide diversity of metabolites. Yet, our understanding of how shifts in plant metabolites as a response to climate change feedback on ecosystem processes remains scarce. Here, we test to what extent climate warming shifts the seasonality of metabolites produced by Sphagnum mosses, and what are the consequences of these shifts for peatland C uptake. We used a reciprocal transplant experiment along a climate gradient in Europe to simulate climate change. We evaluated the responses of primary and secondary metabolites in five Sphagnum species and related their responses to gross ecosystem productivity (GEP). When transplanted to a warmer climate, Sphagnum species showed consistent responses to warming, with an upregulation of either their primary or secondary metabolite according to seasons. Moreover, these shifts were correlated to changes in GEP, especially in spring and autumn. Our results indicate that the Sphagnum metabolome is very plastic and sensitive to warming. We also show that warming-induced changes in the seasonality of Sphagnum metabolites have consequences on peatland GEP. Our findings demonstrate the capacity for plant metabolic plasticity to impact ecosystem C processes and reveal a further mechanism through which Sphagnum could shape peatland responses to climate change.},
	number = {4},
	journal = {New Phytologist},
	author = {Sytiuk, Anna and Hamard, Samuel and Céréghino, Régis and Dorrepaal, Ellen and Geissel, Honorine and Küttim, Martin and Lamentowicz, Mariusz and Tuittila, Eeva Stiina and Jassey, Vincent E. J.},
	year = {2023},
	note = {\_eprint: https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.18601},
	keywords = {\#nosource, Sphagnum, carbon cycle, climate change, climate feedback, intraspecific variability, phenotypic plasticity, plant metabolism, seasonality},
	pages = {1164--1178},
}

Summary Plants produce a wide diversity of metabolites. Yet, our understanding of how shifts in plant metabolites as a response to climate change feedback on ecosystem processes remains scarce. Here, we test to what extent climate warming shifts the seasonality of metabolites produced by Sphagnum mosses, and what are the consequences of these shifts for peatland C uptake. We used a reciprocal transplant experiment along a climate gradient in Europe to simulate climate change. We evaluated the responses of primary and secondary metabolites in five Sphagnum species and related their responses to gross ecosystem productivity (GEP). When transplanted to a warmer climate, Sphagnum species showed consistent responses to warming, with an upregulation of either their primary or secondary metabolite according to seasons. Moreover, these shifts were correlated to changes in GEP, especially in spring and autumn. Our results indicate that the Sphagnum metabolome is very plastic and sensitive to warming. We also show that warming-induced changes in the seasonality of Sphagnum metabolites have consequences on peatland GEP. Our findings demonstrate the capacity for plant metabolic plasticity to impact ecosystem C processes and reveal a further mechanism through which Sphagnum could shape peatland responses to climate change.

@article{puts_browning_2023,
	title = {Browning affects pelagic productivity in northern lakes by surface water warming and carbon fertilization},
	volume = {29},
	copyright = {© 2022 The Authors. Global Change Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.16469},
	doi = {10.1111/gcb.16469},
	abstract = {Global change impacts important environmental drivers for pelagic gross primary production (GPP) in northern lakes, such as temperature, light, nutrient, and inorganic carbon availability. Separate and/or synergistic impacts of these environmental drivers on pelagic GPP remain largely unresolved. Here, we assess key drivers of pelagic GPP by combining detailed depth profiles of summer pelagic GPP with environmental and climatic data across 45 small and shallow lakes across northern Sweden (20 boreal, 6 subarctic, and 19 arctic lakes). We found that across lakes summer pelagic GPP was strongest associated with lake water temperatures, lake carbon dioxide (CO2) concentrations impacted by lake water pH, and further moderated by dissolved organic carbon (DOC) concentrations influencing light and nutrient conditions. We further used this dataset to assess the extent of additional DOC-induced warming of epilimnia (here named internal warming), which was especially pronounced in shallow lakes (decreasing 0.96°C for every decreasing m in average lake depth) and increased with higher concentrations of DOC. Additionally, the total pools and relative proportion of dissolved inorganic carbon and DOC, further influenced pelagic GPP with drivers differing slightly among the boreal, subarctic and Arctic biomes. Our study provides novel insights in that global change affects pelagic GPP in northern lakes not only by modifying the organic carbon cycle and light and nutrient conditions, but also through modifications of inorganic carbon supply and temperature. Considering the large-scale impacts and similarities of global warming, browning and recovery from acidification of lakes at higher latitudes throughout the northern hemisphere, these changes are likely to operate on a global scale.},
	language = {en},
	number = {2},
	urldate = {2023-07-20},
	journal = {Global Change Biology},
	author = {Puts, Isolde C. and Ask, Jenny and Deininger, Anne and Jonsson, Anders and Karlsson, Jan and Bergström, Ann-Kristin},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.16469},
	keywords = {\#nosource, DOC, acidification, bicarbonate system, inorganic carbon, primary production, stoichiometry, supersaturation, temperature},
	pages = {375--390},
}

Global change impacts important environmental drivers for pelagic gross primary production (GPP) in northern lakes, such as temperature, light, nutrient, and inorganic carbon availability. Separate and/or synergistic impacts of these environmental drivers on pelagic GPP remain largely unresolved. Here, we assess key drivers of pelagic GPP by combining detailed depth profiles of summer pelagic GPP with environmental and climatic data across 45 small and shallow lakes across northern Sweden (20 boreal, 6 subarctic, and 19 arctic lakes). We found that across lakes summer pelagic GPP was strongest associated with lake water temperatures, lake carbon dioxide (CO2) concentrations impacted by lake water pH, and further moderated by dissolved organic carbon (DOC) concentrations influencing light and nutrient conditions. We further used this dataset to assess the extent of additional DOC-induced warming of epilimnia (here named internal warming), which was especially pronounced in shallow lakes (decreasing 0.96°C for every decreasing m in average lake depth) and increased with higher concentrations of DOC. Additionally, the total pools and relative proportion of dissolved inorganic carbon and DOC, further influenced pelagic GPP with drivers differing slightly among the boreal, subarctic and Arctic biomes. Our study provides novel insights in that global change affects pelagic GPP in northern lakes not only by modifying the organic carbon cycle and light and nutrient conditions, but also through modifications of inorganic carbon supply and temperature. Considering the large-scale impacts and similarities of global warming, browning and recovery from acidification of lakes at higher latitudes throughout the northern hemisphere, these changes are likely to operate on a global scale.

@article{pajala_higher_2023,
	title = {Higher {Apparent} {Gas} {Transfer} {Velocities} for {CO2} {Compared} to {CH4} in {Small} {Lakes}},
	volume = {57},
	issn = {0013-936X},
	url = {https://doi.org/10.1021/acs.est.2c09230},
	doi = {10.1021/acs.est.2c09230},
	abstract = {Large greenhouse gas emissions occur via the release of carbon dioxide (CO2) and methane (CH4) from the surface layer of lakes. Such emissions are modeled from the air–water gas concentration gradient and the gas transfer velocity (k). The links between k and the physical properties of the gas and water have led to the development of methods to convert k between gases through Schmidt number normalization. However, recent observations have found that such normalization of apparent k estimates from field measurements can yield different results for CH4 and CO2. We estimated k for CO2 and CH4 from measurements of concentration gradients and fluxes in four contrasting lakes and found consistently higher (on an average 1.7 times) normalized apparent k values for CO2 than CH4. From these results, we infer that several gas-specific factors, including chemical and biological processes within the water surface microlayer, can influence apparent k estimates. We highlight the importance of accurately measuring relevant air–water gas concentration gradients and considering gas-specific processes when estimating k.},
	number = {23},
	urldate = {2023-07-20},
	journal = {Environmental Science \& Technology},
	author = {Pajala, Gustav and Rudberg, David and Gålfalk, Magnus and Melack, John Michael and Macintyre, Sally and Karlsson, Jan and Sawakuchi, Henrique Oliveira and Schenk, Jonathan and Sieczko, Anna and Sundgren, Ingrid and Duc, Nguyen Thanh and Bastviken, David},
	month = jun,
	year = {2023},
	note = {Publisher: American Chemical Society},
	keywords = {\#nosource},
	pages = {8578--8587},
}

Large greenhouse gas emissions occur via the release of carbon dioxide (CO2) and methane (CH4) from the surface layer of lakes. Such emissions are modeled from the air–water gas concentration gradient and the gas transfer velocity (k). The links between k and the physical properties of the gas and water have led to the development of methods to convert k between gases through Schmidt number normalization. However, recent observations have found that such normalization of apparent k estimates from field measurements can yield different results for CH4 and CO2. We estimated k for CO2 and CH4 from measurements of concentration gradients and fluxes in four contrasting lakes and found consistently higher (on an average 1.7 times) normalized apparent k values for CO2 than CH4. From these results, we infer that several gas-specific factors, including chemical and biological processes within the water surface microlayer, can influence apparent k estimates. We highlight the importance of accurately measuring relevant air–water gas concentration gradients and considering gas-specific processes when estimating k.

@article{koizumi_experimental_2023,
	title = {Experimental warming and browning influence autumnal pelagic and benthic invertebrate biomass and community structure},
	volume = {68},
	copyright = {© 2023 The Authors. Freshwater Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2427},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.14099},
	doi = {10.1111/fwb.14099},
	abstract = {Globally, lakes are warming and browning with ongoing climate change. These changes significantly impact a lake's biogeochemical properties and all organisms, including invertebrate consumers. The effects of these changes are essential to understand, especially during critical periods after and before the growing season, that is, autumn and spring, which can determine the composition of the invertebrate consumer community. In this study, we used a large-scale experimental pond system to test the combined effect of warming (+3°C) and increased input of terrestrial and coloured dissolved organic carbon (gradient of 1.6–8.8 mg/L in the ambient and 1.6–9.3 mg/L in the warm)—which causes browning—on zooplankton and benthic macroinvertebrate biomass and composition during the autumn and the following spring. Total zooplankton biomass decreased with warming and increased with browning, while total zoobenthos did not respond to either treatment. Warming and browning throughout the autumn had no overall interactive effects on zooplankton or zoobenthos. Autumnal warming decreased total pelagic consumer biomass, caused by a decrease in both Rotifera and Copepoda. In contrast, there was no effect on overall benthic consumer biomass, with only Asellus sp. biomass showing a negative response to warming. An autumnal increase in dissolved organic carbon led to increased total pelagic consumer biomass, which was related to increases in Daphnia sp. biomass but did not affect zoobenthos biomass. While we expected zooplankton and zoobenthos biomass to follow responses in primary and bacterial production to treatments, we did not find any relationship between consumer groups and these estimates of resource production. Our results suggest that consumer responses to warming and browning during autumn may lead to less overarching general changes in consumer biomass, and responses are mostly taxon-specific. This study gives novel insights into the effects of warming and browning on consumer biomass during autumn and spring and increases the understanding of the effects of climate change on invertebrate community biomass in the different habitats.},
	language = {en},
	number = {7},
	urldate = {2023-07-20},
	journal = {Freshwater Biology},
	author = {Koizumi, Shuntaro and Hamdan, Mohammed and Puts, Isolde Callisto and Bergström, Ann-Kristin and Karlsson, Jan and Byström, Pär},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.14099},
	keywords = {\#nosource, climate change, dissolved organic carbon, habitat-specific primary production, zoobenthos, zooplankton},
	pages = {1224--1237},
}

Globally, lakes are warming and browning with ongoing climate change. These changes significantly impact a lake's biogeochemical properties and all organisms, including invertebrate consumers. The effects of these changes are essential to understand, especially during critical periods after and before the growing season, that is, autumn and spring, which can determine the composition of the invertebrate consumer community. In this study, we used a large-scale experimental pond system to test the combined effect of warming (+3°C) and increased input of terrestrial and coloured dissolved organic carbon (gradient of 1.6–8.8 mg/L in the ambient and 1.6–9.3 mg/L in the warm)—which causes browning—on zooplankton and benthic macroinvertebrate biomass and composition during the autumn and the following spring. Total zooplankton biomass decreased with warming and increased with browning, while total zoobenthos did not respond to either treatment. Warming and browning throughout the autumn had no overall interactive effects on zooplankton or zoobenthos. Autumnal warming decreased total pelagic consumer biomass, caused by a decrease in both Rotifera and Copepoda. In contrast, there was no effect on overall benthic consumer biomass, with only Asellus sp. biomass showing a negative response to warming. An autumnal increase in dissolved organic carbon led to increased total pelagic consumer biomass, which was related to increases in Daphnia sp. biomass but did not affect zoobenthos biomass. While we expected zooplankton and zoobenthos biomass to follow responses in primary and bacterial production to treatments, we did not find any relationship between consumer groups and these estimates of resource production. Our results suggest that consumer responses to warming and browning during autumn may lead to less overarching general changes in consumer biomass, and responses are mostly taxon-specific. This study gives novel insights into the effects of warming and browning on consumer biomass during autumn and spring and increases the understanding of the effects of climate change on invertebrate community biomass in the different habitats.

@article{golub_diel_2023,
	title = {Diel, seasonal, and inter-annual variation in carbon dioxide effluxes from lakes and reservoirs},
	volume = {18},
	issn = {1748-9326},
	url = {https://dx.doi.org/10.1088/1748-9326/acb834},
	doi = {10.1088/1748-9326/acb834},
	abstract = {Accounting for temporal changes in carbon dioxide (CO2) effluxes from freshwaters remains a challenge for global and regional carbon budgets. Here, we synthesize 171 site-months of flux measurements of CO2 based on the eddy covariance method from 13 lakes and reservoirs in the Northern Hemisphere, and quantify dynamics at multiple temporal scales. We found pronounced sub-annual variability in CO2 flux at all sites. By accounting for diel variation, only 11\% of site-months were net daily sinks of CO2. Annual CO2 emissions had an average of 25\% (range 3\%–58\%) interannual variation. Similar to studies on streams, nighttime emissions regularly exceeded daytime emissions. Biophysical regulations of CO2 flux variability were delineated through mutual information analysis. Sample analysis of CO2 fluxes indicate the importance of continuous measurements. Better characterization of short- and long-term variability is necessary to understand and improve detection of temporal changes of CO2 fluxes in response to natural and anthropogenic drivers. Our results indicate that existing global lake carbon budgets relying primarily on daytime measurements yield underestimates of net emissions.},
	language = {en},
	number = {3},
	urldate = {2023-07-20},
	journal = {Environmental Research Letters},
	author = {Golub, Malgorzata and Koupaei-Abyazani, Nikaan and Vesala, Timo and Mammarella, Ivan and Ojala, Anne and Bohrer, Gil and Weyhenmeyer, Gesa A. and Blanken, Peter D. and Eugster, Werner and Koebsch, Franziska and Chen, Jiquan and Czajkowski, Kevin and Deshmukh, Chandrashekhar and Guérin, Frederic and Heiskanen, Jouni and Humphreys, Elyn and Jonsson, Anders and Karlsson, Jan and Kling, George and Lee, Xuhui and Liu, Heping and Lohila, Annalea and Lundin, Erik and Morin, Tim and Podgrajsek, Eva and Provenzale, Maria and Rutgersson, Anna and Sachs, Torsten and Sahlée, Erik and Serça, Dominique and Shao, Changliang and Spence, Christopher and Strachan, Ian B. and Xiao, Wei and Desai, Ankur R.},
	month = mar,
	year = {2023},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {034046},
}

Accounting for temporal changes in carbon dioxide (CO2) effluxes from freshwaters remains a challenge for global and regional carbon budgets. Here, we synthesize 171 site-months of flux measurements of CO2 based on the eddy covariance method from 13 lakes and reservoirs in the Northern Hemisphere, and quantify dynamics at multiple temporal scales. We found pronounced sub-annual variability in CO2 flux at all sites. By accounting for diel variation, only 11% of site-months were net daily sinks of CO2. Annual CO2 emissions had an average of 25% (range 3%–58%) interannual variation. Similar to studies on streams, nighttime emissions regularly exceeded daytime emissions. Biophysical regulations of CO2 flux variability were delineated through mutual information analysis. Sample analysis of CO2 fluxes indicate the importance of continuous measurements. Better characterization of short- and long-term variability is necessary to understand and improve detection of temporal changes of CO2 fluxes in response to natural and anthropogenic drivers. Our results indicate that existing global lake carbon budgets relying primarily on daytime measurements yield underestimates of net emissions.

@article{vachon_controls_2023,
	title = {Controls on {Terrestrial} {Carbon} {Fluxes} in {Simulated} {Networks} of {Connected} {Streams} and {Lakes}},
	volume = {37},
	copyright = {© 2023. The Authors.},
	issn = {1944-9224},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GB007597},
	doi = {10.1029/2022GB007597},
	abstract = {Inland waters play a critical role in the carbon cycle by emitting significant amounts of land-exported carbon to the atmosphere. While carbon gas emissions from individual aquatic systems have been extensively studied, how networks of connected streams and lakes regulate integrated fluxes of organic and inorganic forms remain poorly understood. Here, we develop a process-based model to simulate the fate of terrestrial dissolved organic carbon (DOC) and carbon dioxide (CO2) in artificial inland water networks with variable topology, hydrology, and DOC reactivity. While the role of lakes is highly dependent on DOC reactivity, we find that the mineralization of terrestrial DOC is more efficient in lake-rich networks. Regardless of typology and hydrology, terrestrial CO2 is emitted almost entirely within the network boundary. Consequently, the proportion of exported terrestrial carbon emitted from inland water networks increases with the CO2 versus DOC export ratio. Overall, our results suggest that CO2 emissions from inland waters are governed by interactions between the relative amount and reactivity of terrestrial DOC and CO2 inputs and the network configuration of recipient lakes and streams.},
	language = {en},
	number = {3},
	urldate = {2023-07-20},
	journal = {Global Biogeochemical Cycles},
	author = {Vachon, Dominic and Sponseller, Ryan A. and Rosvall, Martin and Karlsson, Jan},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GB007597},
	keywords = {\#nosource, CO2 emission, DOC mineralization, aquatic network, carbon cycle, modeling},
	pages = {e2022GB007597},
}

Inland waters play a critical role in the carbon cycle by emitting significant amounts of land-exported carbon to the atmosphere. While carbon gas emissions from individual aquatic systems have been extensively studied, how networks of connected streams and lakes regulate integrated fluxes of organic and inorganic forms remain poorly understood. Here, we develop a process-based model to simulate the fate of terrestrial dissolved organic carbon (DOC) and carbon dioxide (CO2) in artificial inland water networks with variable topology, hydrology, and DOC reactivity. While the role of lakes is highly dependent on DOC reactivity, we find that the mineralization of terrestrial DOC is more efficient in lake-rich networks. Regardless of typology and hydrology, terrestrial CO2 is emitted almost entirely within the network boundary. Consequently, the proportion of exported terrestrial carbon emitted from inland water networks increases with the CO2 versus DOC export ratio. Overall, our results suggest that CO2 emissions from inland waters are governed by interactions between the relative amount and reactivity of terrestrial DOC and CO2 inputs and the network configuration of recipient lakes and streams.

@article{casas-ruiz_integrating_2023,
	title = {Integrating terrestrial and aquatic ecosystems to constrain estimates of land-atmosphere carbon exchange},
	volume = {14},
	copyright = {2023 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-023-37232-2},
	doi = {10.1038/s41467-023-37232-2},
	abstract = {In this Perspective, we put forward an integrative framework to improve estimates of land-atmosphere carbon exchange based on the accumulation of carbon in the landscape as constrained by its lateral export through rivers. The framework uses the watershed as the fundamental spatial unit and integrates all terrestrial and aquatic ecosystems as well as their hydrologic carbon exchanges. Application of the framework should help bridge the existing gap between land and atmosphere-based approaches and offers a platform to increase communication and synergy among the terrestrial, aquatic, and atmospheric research communities that is paramount to advance landscape carbon budget assessments.},
	language = {en},
	number = {1},
	urldate = {2023-07-20},
	journal = {Nature Communications},
	author = {Casas-Ruiz, Joan P. and Bodmer, Pascal and Bona, Kelly Ann and Butman, David and Couturier, Mathilde and Emilson, Erik J. S. and Finlay, Kerri and Genet, Hélène and Hayes, Daniel and Karlsson, Jan and Paré, David and Peng, Changhui and Striegl, Rob and Webb, Jackie and Wei, Xinyuan and Ziegler, Susan E. and del Giorgio, Paul A.},
	month = mar,
	year = {2023},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource, Carbon cycle, Environmental sciences},
	pages = {1571},
}

In this Perspective, we put forward an integrative framework to improve estimates of land-atmosphere carbon exchange based on the accumulation of carbon in the landscape as constrained by its lateral export through rivers. The framework uses the watershed as the fundamental spatial unit and integrates all terrestrial and aquatic ecosystems as well as their hydrologic carbon exchanges. Application of the framework should help bridge the existing gap between land and atmosphere-based approaches and offers a platform to increase communication and synergy among the terrestrial, aquatic, and atmospheric research communities that is paramount to advance landscape carbon budget assessments.

@article{berggren_nutrient_2023,
	title = {Nutrient limitation masks the dissolved organic matter composition effects on bacterial metabolism in unproductive freshwaters},
	volume = {n/a},
	copyright = {© 2023 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.12406},
	doi = {10.1002/lno.12406},
	abstract = {Aquatic microbial responses to changes in the amount and composition of dissolved organic carbon (DOC) are of fundamental ecological and biogeochemical importance. Parallel factor (PARAFAC) analysis of excitation–emission fluorescence spectra is a common tool to characterize DOC, yet its ability to predict bacterial production (BP), bacterial respiration (BR), and bacterial growth efficiency (BGE) vary widely, potentially because inorganic nutrient limitation decouples microbial processes from their dependence on DOC composition. We used 28-d bioassays with water from 19 lakes, streams, and rivers in northern Sweden to test how much the links between bacterial metabolism and fluorescence PARAFAC components depend on experimental additions of inorganic nutrients. We found a significant interaction effect between nutrient addition and fluorescence on carbon-specific BP, and weak evidence for influence on BGE by the same interaction (p = 0.1), but no corresponding interaction effect on BR. A practical implication of this interaction was that fluorescence components could explain more than twice as much of the variability in carbon-specific BP (R2 = 0.90) and BGE (R2 = 0.70) after nitrogen and phosphorus addition, compared with control incubations. Our results suggest that an increased supply of labile DOC relative to ambient phosphorus and nitrogen induces gradually larger degrees of nutrient limitation of BP, which in turn decouple BP and BGE from fluorescence signals. Thus, while fluorescence does contain precise information about the degree to which DOC can support microbial processes, this information may be hidden in field studies due to nutrient limitation of bacterial metabolism.},
	language = {en},
	number = {n/a},
	urldate = {2023-07-20},
	journal = {Limnology and Oceanography},
	author = {Berggren, Martin and Ye, Linlin and Sponseller, Ryan A. and Bergström, Ann-Kristin and Karlsson, Jan and Verheijen, Hendricus and Hensgens, Geert},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.12406},
	keywords = {\#nosource, ⛔ No INSPIRE recid found},
	pages = {1--11},
}

Aquatic microbial responses to changes in the amount and composition of dissolved organic carbon (DOC) are of fundamental ecological and biogeochemical importance. Parallel factor (PARAFAC) analysis of excitation–emission fluorescence spectra is a common tool to characterize DOC, yet its ability to predict bacterial production (BP), bacterial respiration (BR), and bacterial growth efficiency (BGE) vary widely, potentially because inorganic nutrient limitation decouples microbial processes from their dependence on DOC composition. We used 28-d bioassays with water from 19 lakes, streams, and rivers in northern Sweden to test how much the links between bacterial metabolism and fluorescence PARAFAC components depend on experimental additions of inorganic nutrients. We found a significant interaction effect between nutrient addition and fluorescence on carbon-specific BP, and weak evidence for influence on BGE by the same interaction (p = 0.1), but no corresponding interaction effect on BR. A practical implication of this interaction was that fluorescence components could explain more than twice as much of the variability in carbon-specific BP (R2 = 0.90) and BGE (R2 = 0.70) after nitrogen and phosphorus addition, compared with control incubations. Our results suggest that an increased supply of labile DOC relative to ambient phosphorus and nitrogen induces gradually larger degrees of nutrient limitation of BP, which in turn decouple BP and BGE from fluorescence signals. Thus, while fluorescence does contain precise information about the degree to which DOC can support microbial processes, this information may be hidden in field studies due to nutrient limitation of bacterial metabolism.

@article{krickov_environmental_2023,
	title = {Environmental controllers for carbon emission and concentration patterns in {Siberian} rivers during different seasons},
	volume = {859},
	issn = {0048-9697},
	doi = {10.1016/J.SCITOTENV.2022.160202},
	abstract = {Despite the importance of small and medium size rivers of Siberian boreal zone in greenhouse gases (GHG) emission, major knowledge gaps exist regarding its temporal variability and controlling mechanisms. Here we sampled 11 pristine rivers of the southern taiga biome (western Siberia Lowland, WSL), ranging in watershed area from 0.8 to 119,000 km2, to reveal temporal pattern and examine main environmental controllers of GHG emissions from the river water surfaces. Floating chamber measurements demonstrated that CO2 emissions from water surface decreased by 2 to 4-folds from spring to summer and autumn, were independent of the size of the watershed and stream order and did not exhibit sizable ({\textgreater}30 \%, regardless of season) variations between day and night. The CH4 concentrations and fluxes increased in the order “spring ≤ summer {\textless} autumn” and ranged from 1 to 15 μmol L−1 and 5 to 100 mmol m−2 d−1, respectively. The CO2 concentrations and fluxes (range from 100 to 400 μmol L−1 and 1 to 4 g C m−2 d−1, respectively) were positively correlated with dissolved and particulate organic carbon, total nitrogen and bacterial number of the water column. The CH4 concentrations and fluxes were positively correlated with phosphate and ammonia concentrations. Of the landscape parameters, positive correlations were detected between riparian vegetation biomass and CO2 and CH4 concentrations. Over the six-month open-water period, areal emissions of C ({\textgreater}99.5 \% CO2; {\textless}0.5 \% CH4) from the watersheds of 11 rivers were equal to the total downstream C export in this part of the WSL. Based on correlations between environmental controllers (watershed land cover and the water column parameters), we hypothesize that the fluxes are largely driven by riverine mineralization of terrestrial dissolved and particulate OC, coupled with respiration at the river bottom and riparian sediments. It follows that, under climate warming scenario, most significant changes in GHG regimes of western Siberian rivers located in permafrost-free zone may occur due to changes in the riparian zone vegetation and water coverage of the floodplains.},
	urldate = {2023-07-20},
	journal = {Science of The Total Environment},
	author = {Krickov, Ivan V. and Lim, Artem G. and Shirokova, Liudmila S. and Korets, Mikhail and Karlsson, Jan and Pokrovsky, Oleg S.},
	month = feb,
	year = {2023},
	pmid = {36395838},
	note = {Publisher: Elsevier},
	keywords = {\#nosource, Boreal, CH4, CO2, Emission, Landscape, Organic carbon, River},
	pages = {160202},
}

Despite the importance of small and medium size rivers of Siberian boreal zone in greenhouse gases (GHG) emission, major knowledge gaps exist regarding its temporal variability and controlling mechanisms. Here we sampled 11 pristine rivers of the southern taiga biome (western Siberia Lowland, WSL), ranging in watershed area from 0.8 to 119,000 km2, to reveal temporal pattern and examine main environmental controllers of GHG emissions from the river water surfaces. Floating chamber measurements demonstrated that CO2 emissions from water surface decreased by 2 to 4-folds from spring to summer and autumn, were independent of the size of the watershed and stream order and did not exhibit sizable (\textgreater30 %, regardless of season) variations between day and night. The CH4 concentrations and fluxes increased in the order “spring ≤ summer \textless autumn” and ranged from 1 to 15 μmol L−1 and 5 to 100 mmol m−2 d−1, respectively. The CO2 concentrations and fluxes (range from 100 to 400 μmol L−1 and 1 to 4 g C m−2 d−1, respectively) were positively correlated with dissolved and particulate organic carbon, total nitrogen and bacterial number of the water column. The CH4 concentrations and fluxes were positively correlated with phosphate and ammonia concentrations. Of the landscape parameters, positive correlations were detected between riparian vegetation biomass and CO2 and CH4 concentrations. Over the six-month open-water period, areal emissions of C (\textgreater99.5 % CO2; \textless0.5 % CH4) from the watersheds of 11 rivers were equal to the total downstream C export in this part of the WSL. Based on correlations between environmental controllers (watershed land cover and the water column parameters), we hypothesize that the fluxes are largely driven by riverine mineralization of terrestrial dissolved and particulate OC, coupled with respiration at the river bottom and riparian sediments. It follows that, under climate warming scenario, most significant changes in GHG regimes of western Siberian rivers located in permafrost-free zone may occur due to changes in the riparian zone vegetation and water coverage of the floodplains.

@article{lett_can_2022,
	title = {Can bryophyte groups increase functional resolution in tundra ecosystems?},
	volume = {8},
	url = {https://cdnsciencepub.com/doi/full/10.1139/as-2020-0057},
	doi = {10.1139/as-2020-0057},
	abstract = {The relative contribution of bryophytes to plant diversity, primary productivity, and ecosystem functioning increases towards colder climates. Bryophytes respond to environmental changes at the species level, but because bryophyte species are relatively difficult to identify, they are often lumped into one functional group. Consequently, bryophyte function remains poorly resolved. Here, we explore how higher resolution of bryophyte functional diversity can be encouraged and implemented in tundra ecological studies. We briefly review previous bryophyte functional classifications and the roles of bryophytes in tundra ecosystems and their susceptibility to environmental change. Based on shoot morphology and colony organization, we then propose twelve easily distinguishable bryophyte functional groups. To illustrate how bryophyte functional groups can help elucidate variation in bryophyte effects and responses, we compiled existing data on water holding capacity, a key bryophyte trait. Although plant functional groups can mask potentially high interspecific and intraspecific variability, we found better separation of bryophyte functional group means compared with previous grouping systems regarding water holding capacity. This suggests that our bryophyte functional groups truly represent variation in the functional roles of bryophytes in tundra ecosystems. Lastly, we provide recommendations to improve the monitoring of bryophyte community changes in tundra study sites.},
	number = {3},
	urldate = {2024-03-27},
	journal = {Arctic Science},
	author = {Lett, Signe and Jónsdóttir, Ingibjörg S. and Becker-Scarpitta, Antoine and Christiansen, Casper T. and During, Heinjo and Ekelund, Flemming and Henry, Gregory H.R. and Lang, Simone I. and Michelsen, Anders and Rousk, Kathrin and Alatalo, Juha M. and Betway, Katlyn R. and Rui, Sara B. and Callaghan, Terry and Carbognani, Michele and Cooper, Elisabeth J. and Cornelissen, J. Hans C. and Dorrepaal, Ellen and Egelkraut, Dagmar and Elumeeva, Tatiana G. and Haugum, Siri V. and Hollister, Robert D. and Jägerbrand, Annika K. and Keuper, Frida and Klanderud, Kari and Lévesque, Esther and Liu, Xin and May, Jeremy and Michel, Pascale and Mörsdorf, Martin and Petraglia, Alessandro and Rixen, Christian and Robroek, Bjorn J.M. and Rzepczynska, Agnieszka M. and Soudzilovskaia, Nadejda A. and Tolvanen, Anne and Vandvik, Vigdis and Volkov, Igor and Volkova, Irina and Zuijlen, Kristel van},
	month = sep,
	year = {2022},
	note = {Publisher: NRC Research Press},
	keywords = {\#nosource},
	pages = {609--637},
}

The relative contribution of bryophytes to plant diversity, primary productivity, and ecosystem functioning increases towards colder climates. Bryophytes respond to environmental changes at the species level, but because bryophyte species are relatively difficult to identify, they are often lumped into one functional group. Consequently, bryophyte function remains poorly resolved. Here, we explore how higher resolution of bryophyte functional diversity can be encouraged and implemented in tundra ecological studies. We briefly review previous bryophyte functional classifications and the roles of bryophytes in tundra ecosystems and their susceptibility to environmental change. Based on shoot morphology and colony organization, we then propose twelve easily distinguishable bryophyte functional groups. To illustrate how bryophyte functional groups can help elucidate variation in bryophyte effects and responses, we compiled existing data on water holding capacity, a key bryophyte trait. Although plant functional groups can mask potentially high interspecific and intraspecific variability, we found better separation of bryophyte functional group means compared with previous grouping systems regarding water holding capacity. This suggests that our bryophyte functional groups truly represent variation in the functional roles of bryophytes in tundra ecosystems. Lastly, we provide recommendations to improve the monitoring of bryophyte community changes in tundra study sites.

@article{windirsch_large_2022,
	title = {Large herbivores on permafrost— a pilot study of grazing impacts on permafrost soil carbon storage in northeastern {Siberia}},
	volume = {10},
	issn = {2296-665X},
	url = {https://www.frontiersin.org/articles/10.3389/fenvs.2022.893478},
	doi = {10.3389/fenvs.2022.893478},
	abstract = {The risk of carbon emissions from permafrost is linked to an increase in ground temperature and thus in particular to thermal insulation by vegetation, soil layers and snow cover. Ground insulation can be influenced by the presence of large herbivores browsing for food in both winter and summer. In this study, we examine the potential impact of large herbivore presence on the soil carbon storage in a thermokarst landscape in northeastern Siberia. Our aim in this pilot study is to conduct a first analysis on whether intensive large herbivore grazing may slow or even reverse permafrost thaw by affecting thermal insulation through modifying ground cover properties. As permafrost soil temperatures are important for organic matter decomposition, we hypothesize that herbivory disturbances lead to different ground carbon storages. Therefore, we analyzed five sites with a total of three different herbivore grazing intensities on two landscape forms (drained thermokarst basin, Yedoma upland) in Pleistocene Park near Chersky. We measured maximum thaw depth, total organic carbon content,δ13C isotopes , carbon-nitrogen ratios, and sediment grain-size composition as well as ice and water content for each site. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. First data show that intensive grazing leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies including investigations of the hydrology and general ground conditions existing prior to grazing introduction. We explain our findings by intensive animal trampling in winter and vegetation changes, which overcompensate summer ground warming. We conclude that grazing intensity – along with soil substrate and hydrologic conditions – might have a measurable influence on the carbon storage in permafrost soils. Hence the grazing effect should be further investigated for its potential as an actively manageable instrument to reduce net carbon emission from permafrost.},
	language = {English},
	urldate = {2024-03-27},
	journal = {Frontiers in Environmental Science},
	author = {Windirsch, Torben and Grosse, Guido and Ulrich, Mathias and Forbes, Bruce C. and Göckede, Mathias and Wolter, Juliane and Macias-Fauria, Marc and Olofsson, Johan and Zimov, Nikita and Strauss, Jens},
	month = aug,
	year = {2022},
	note = {Publisher: Frontiers},
	keywords = {Animal Husbandry, Climate Change, bio-geo interactions, organic material inventory, rewilding},
	pages = {893478},
}

The risk of carbon emissions from permafrost is linked to an increase in ground temperature and thus in particular to thermal insulation by vegetation, soil layers and snow cover. Ground insulation can be influenced by the presence of large herbivores browsing for food in both winter and summer. In this study, we examine the potential impact of large herbivore presence on the soil carbon storage in a thermokarst landscape in northeastern Siberia. Our aim in this pilot study is to conduct a first analysis on whether intensive large herbivore grazing may slow or even reverse permafrost thaw by affecting thermal insulation through modifying ground cover properties. As permafrost soil temperatures are important for organic matter decomposition, we hypothesize that herbivory disturbances lead to different ground carbon storages. Therefore, we analyzed five sites with a total of three different herbivore grazing intensities on two landscape forms (drained thermokarst basin, Yedoma upland) in Pleistocene Park near Chersky. We measured maximum thaw depth, total organic carbon content,δ13C isotopes , carbon-nitrogen ratios, and sediment grain-size composition as well as ice and water content for each site. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. First data show that intensive grazing leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies including investigations of the hydrology and general ground conditions existing prior to grazing introduction. We explain our findings by intensive animal trampling in winter and vegetation changes, which overcompensate summer ground warming. We conclude that grazing intensity – along with soil substrate and hydrologic conditions – might have a measurable influence on the carbon storage in permafrost soils. Hence the grazing effect should be further investigated for its potential as an actively manageable instrument to reduce net carbon emission from permafrost.

@article{truchy_responses_2022,
	title = {Responses of multiple structural and functional indicators along three contrasting disturbance gradients},
	volume = {135},
	issn = {1470-160X},
	url = {https://www.sciencedirect.com/science/article/pii/S1470160X21011791},
	doi = {10.1016/j.ecolind.2021.108514},
	abstract = {Ecosystem functioning and community structure are recognized as key components of ecosystem integrity, but comprehensive, standardized studies of the responses of both structural and functional indicators to different types of anthropogenic pressures remain rare. Consequently, we lack an empirical basis for (i) identifying when monitoring ecosystem structure alone misses important changes in ecosystem functioning, (ii) recommending sets of structural and functional metrics best suited for detecting ecological change driven by different anthropogenic pressures, and (iii) understanding the cumulative effects of multiple, co-occurring stressors on structure and function. We investigated variation in community structure and ecosystem functioning of stream ecosystems along three gradients (10–16 independent stream sites each) of increasing impact arising from agriculture, forestry and river regulation for hydropower, respectively. For each stream, we quantified variation in (i) the abiotic environment, (ii) community composition of four organism groups and (iii) three basal ecosystem processes underpinning carbon and nutrient cycling in streams. We assessed the responsiveness of multiple biodiversity, community structure and ecosystem functioning indicators based on variance explained and effect size metrics. Along a gradient of increasing agricultural impact, diatoms and fish were the most responsive groups overall, but significant variation was detected in at least one aspect of community composition, abundance and/or biodiversity of every organism group . In contrast, most of our functional metrics did not vary significantly along the agricultural gradient, possibly due to contrasting, antagonistic effects of increasing nutrient concentrations and turbidity on ecosystem process rates. The exception was detritivore-mediated litter decomposition which increased up to moderate levels of nutrient. Impacts of river regulation were most marked for diatoms, which were responsive to both increasingly frequent hydropeaking and to increasing seasonal river regulation. Among functional indicators, both litter decomposition and algal biomass accrual declined significantly with increasing hydropeaking. Few structural or functional metrics varied with forest management, with macroinvertebrate diversity increasing along the forestry gradient, as did algal and fungal biomass accrual. Together, these findings highlight the challenges of making inferences about the impacts of anthropogenic disturbances at the ecosystem level based on community data alone, and pinpoint the need to identify optimal sets of functional and structural indicators best suited for detecting ecological changes associated with different human activities.},
	urldate = {2024-03-27},
	journal = {Ecological Indicators},
	author = {Truchy, Amélie and Sponseller, Ryan A. and Ecke, Frauke and Angeler, David G. and Kahlert, Maria and Bundschuh, Mirco and Johnson, Richard K. and McKie, Brendan G.},
	month = feb,
	year = {2022},
	keywords = {Agriculture, Community structure, Ecosystem functioning, Forestry, Multiple stressors, River regulation},
	pages = {108514},
}

Ecosystem functioning and community structure are recognized as key components of ecosystem integrity, but comprehensive, standardized studies of the responses of both structural and functional indicators to different types of anthropogenic pressures remain rare. Consequently, we lack an empirical basis for (i) identifying when monitoring ecosystem structure alone misses important changes in ecosystem functioning, (ii) recommending sets of structural and functional metrics best suited for detecting ecological change driven by different anthropogenic pressures, and (iii) understanding the cumulative effects of multiple, co-occurring stressors on structure and function. We investigated variation in community structure and ecosystem functioning of stream ecosystems along three gradients (10–16 independent stream sites each) of increasing impact arising from agriculture, forestry and river regulation for hydropower, respectively. For each stream, we quantified variation in (i) the abiotic environment, (ii) community composition of four organism groups and (iii) three basal ecosystem processes underpinning carbon and nutrient cycling in streams. We assessed the responsiveness of multiple biodiversity, community structure and ecosystem functioning indicators based on variance explained and effect size metrics. Along a gradient of increasing agricultural impact, diatoms and fish were the most responsive groups overall, but significant variation was detected in at least one aspect of community composition, abundance and/or biodiversity of every organism group . In contrast, most of our functional metrics did not vary significantly along the agricultural gradient, possibly due to contrasting, antagonistic effects of increasing nutrient concentrations and turbidity on ecosystem process rates. The exception was detritivore-mediated litter decomposition which increased up to moderate levels of nutrient. Impacts of river regulation were most marked for diatoms, which were responsive to both increasingly frequent hydropeaking and to increasing seasonal river regulation. Among functional indicators, both litter decomposition and algal biomass accrual declined significantly with increasing hydropeaking. Few structural or functional metrics varied with forest management, with macroinvertebrate diversity increasing along the forestry gradient, as did algal and fungal biomass accrual. Together, these findings highlight the challenges of making inferences about the impacts of anthropogenic disturbances at the ecosystem level based on community data alone, and pinpoint the need to identify optimal sets of functional and structural indicators best suited for detecting ecological changes associated with different human activities.

@article{tiwari_emerging_2022,
	title = {The emerging role of drought as a regulator of dissolved organic carbon in boreal landscapes},
	volume = {13},
	copyright = {2022 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-022-32839-3},
	doi = {10.1038/s41467-022-32839-3},
	abstract = {One likely consequence of global climate change is an increased frequency and intensity of droughts at high latitudes. Here we use a 17-year record from 13 nested boreal streams to examine direct and lagged effects of summer drought on the quantity and quality of dissolved organic carbon (DOC) inputs from catchment soils. Protracted periods of drought reduced DOC concentrations in all catchments but also led to large stream DOC pulses upon rewetting. Concurrent changes in DOC optical properties and chemical character suggest that seasonal drying and rewetting trigger soil processes that alter the forms of carbon supplied to streams. Contrary to expectations, clearest drought effects were observed in larger watersheds, whereas responses were most muted in smaller, peatland-dominated catchments. Collectively, our results indicate that summer drought causes a fundamental shift in the seasonal distribution of DOC concentrations and character, which together operate as primary controls over the ecological and biogeochemical functioning of northern aquatic ecosystems.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Nature Communications},
	author = {Tiwari, Tejshree and Sponseller, Ryan A. and Laudon, Hjalmar},
	month = aug,
	year = {2022},
	note = {Publisher: Nature Publishing Group},
	keywords = {Carbon cycle, Environmental impact, Hydrology},
	pages = {5125},
}

One likely consequence of global climate change is an increased frequency and intensity of droughts at high latitudes. Here we use a 17-year record from 13 nested boreal streams to examine direct and lagged effects of summer drought on the quantity and quality of dissolved organic carbon (DOC) inputs from catchment soils. Protracted periods of drought reduced DOC concentrations in all catchments but also led to large stream DOC pulses upon rewetting. Concurrent changes in DOC optical properties and chemical character suggest that seasonal drying and rewetting trigger soil processes that alter the forms of carbon supplied to streams. Contrary to expectations, clearest drought effects were observed in larger watersheds, whereas responses were most muted in smaller, peatland-dominated catchments. Collectively, our results indicate that summer drought causes a fundamental shift in the seasonal distribution of DOC concentrations and character, which together operate as primary controls over the ecological and biogeochemical functioning of northern aquatic ecosystems.

@article{sytiuk_predicting_2022,
	title = {Predicting the structure and functions of peatland microbial communities from {Sphagnum} phylogeny, anatomical and morphological traits and metabolites},
	volume = {110},
	copyright = {© 2021 British Ecological Society},
	issn = {1365-2745},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.13728},
	doi = {10.1111/1365-2745.13728},
	abstract = {Sphagnum mosses are keystone species in northern peatlands. Notably, they play an important role in peatland carbon (C) cycling by regulating the composition and activity of microbial communities. However, it remains unclear whether information on Sphagnum phylogeny and/or traits-based composition (i.e. anatomical and morphological traits and metabolites) can be used to predict the structure of microbial communities and their functioning. Here we evaluated whether Sphagnum phylogeny and traits predict additional variation in peatland microbial community composition and functioning beyond what would be predicted from environmental characteristics (i.e. climatic and edaphic conditions). We collected Sphagnum and microbial data from five European peatlands distributed along a latitudinal gradient from northern Sweden to southern France. These data allowed us to assess Sphagnum anatomical and morphological traits and metabolites at different sites along changing environmental conditions. Using structural equation modelling (SEM) and phylogenetic distance analyses, we investigated the role of Sphagnum traits in shaping microbial community composition and functioning along with environmental conditions. We show that microbial community composition and traits varied independently from both Sphagnum phylogeny and the latitudinal gradient. Specifically, the addition of Sphagnum traits to climatic and edaphic variables to the SEM allowed it to explain a larger proportion of the explained variance (R2). This observation was most apparent for the biomass of decomposers (+42\%) and phototrophs (+19\%), as well as for growth yield microbial traits (+10\%). As such, that Sphagnum metabolites were important drivers for microbial community structure and traits, while Sphagnum anatomical and morphological traits were poor predictors. Synthesis. Our results highlight that Sphagnum metabolites are more likely to influence peatland microbial food web structure and functioning than Sphagnum anatomical and morphological traits. We provide further evidence that measurements of the plant metabolome, when combined with classical functional traits, improve our understanding of how the plants interact with their associated microbiomes.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Journal of Ecology},
	author = {Sytiuk, Anna and Céréghino, Régis and Hamard, Samuel and Delarue, Frédéric and Guittet, Amélie and Barel, Janna M. and Dorrepaal, Ellen and Küttim, Martin and Lamentowicz, Mariusz and Pourrut, Bertrand and Robroek, Bjorn J. M. and Tuittila, Eeva-Stiina and Jassey, Vincent E. J.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2745.13728},
	keywords = {\#nosource, Sphagnum, functional traits, latitudinal gradient, metabolomics, microbial traits, peatlands, plant and microbial communities, plant–soil (below-ground) interactions},
	pages = {80--96},
}

Sphagnum mosses are keystone species in northern peatlands. Notably, they play an important role in peatland carbon (C) cycling by regulating the composition and activity of microbial communities. However, it remains unclear whether information on Sphagnum phylogeny and/or traits-based composition (i.e. anatomical and morphological traits and metabolites) can be used to predict the structure of microbial communities and their functioning. Here we evaluated whether Sphagnum phylogeny and traits predict additional variation in peatland microbial community composition and functioning beyond what would be predicted from environmental characteristics (i.e. climatic and edaphic conditions). We collected Sphagnum and microbial data from five European peatlands distributed along a latitudinal gradient from northern Sweden to southern France. These data allowed us to assess Sphagnum anatomical and morphological traits and metabolites at different sites along changing environmental conditions. Using structural equation modelling (SEM) and phylogenetic distance analyses, we investigated the role of Sphagnum traits in shaping microbial community composition and functioning along with environmental conditions. We show that microbial community composition and traits varied independently from both Sphagnum phylogeny and the latitudinal gradient. Specifically, the addition of Sphagnum traits to climatic and edaphic variables to the SEM allowed it to explain a larger proportion of the explained variance (R2). This observation was most apparent for the biomass of decomposers (+42%) and phototrophs (+19%), as well as for growth yield microbial traits (+10%). As such, that Sphagnum metabolites were important drivers for microbial community structure and traits, while Sphagnum anatomical and morphological traits were poor predictors. Synthesis. Our results highlight that Sphagnum metabolites are more likely to influence peatland microbial food web structure and functioning than Sphagnum anatomical and morphological traits. We provide further evidence that measurements of the plant metabolome, when combined with classical functional traits, improve our understanding of how the plants interact with their associated microbiomes.

@article{seekell_problems_2022,
	title = {Problems {With} the {Shoreline} {Development} {Index}—{A} {Widely} {Used} {Metric} of {Lake} {Shape}},
	volume = {49},
	copyright = {© 2022. The Authors.},
	issn = {1944-8007},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GL098499},
	doi = {10.1029/2022GL098499},
	abstract = {The shoreline development index—The ratio of a lake’s shore length to the circumference of a circle with the lake’s area—Is a core metric of lake morphometry used in Earth and planetary sciences. In this paper, we demonstrate that the shoreline development index is scale-dependent and cannot be used to compare lakes with different areas. We show that large lakes will have higher shoreline development index measurements than smaller lakes of the same characteristic shape, even when mapped at the same scale. Specifically, the shoreline development index increases by about 14\% for each doubling of lake area. These results call into question previously reported patterns of lake shape. We provide several suggestions to improve the application of this index, including a bias-corrected formulation for comparing lakes with different surface areas.},
	language = {en},
	number = {10},
	urldate = {2024-03-27},
	journal = {Geophysical Research Letters},
	author = {Seekell, D. and Cael, B. B. and Byström, P.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GL098499},
	keywords = {lake morphometry, scale-dependence, shoreline development index},
	pages = {e2022GL098499},
}

The shoreline development index—The ratio of a lake’s shore length to the circumference of a circle with the lake’s area—Is a core metric of lake morphometry used in Earth and planetary sciences. In this paper, we demonstrate that the shoreline development index is scale-dependent and cannot be used to compare lakes with different areas. We show that large lakes will have higher shoreline development index measurements than smaller lakes of the same characteristic shape, even when mapped at the same scale. Specifically, the shoreline development index increases by about 14% for each doubling of lake area. These results call into question previously reported patterns of lake shape. We provide several suggestions to improve the application of this index, including a bias-corrected formulation for comparing lakes with different surface areas.

@article{sarneel_species_2022,
	title = {Species traits interact with stress level to determine intraspecific facilitation and competition},
	volume = {33},
	copyright = {© 2022 The Authors. Journal of Vegetation Science published by John Wiley \& Sons Ltd on behalf of International Association for Vegetation Science.},
	issn = {1654-1103},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.13145},
	doi = {10.1111/jvs.13145},
	abstract = {Questions Flooding and drought stress are expected to increase significantly across the world and plant responses to these abiotic changes may be mediated by plant–plant interactions. Stress tolerance and recovery often require a biomass investment that may have consequences for these plant–plant interactions. Therefore, we questioned whether phenotypic plasticity in response to flooding and drought affected the balance between competition and facilitation for species with specific adaptations to drought or flooding. Location Utrecht University. Methods Stem elongation, root porosity, root:shoot ratio and biomass production were measured for six species during drought, well-drained and submerged conditions when grown alone or together with conspecifics. We quantified competition and facilitation as the ‘neighbour intensity effect’ directly after the 10-day treatment and again after a seven-day recovery period in well-drained conditions. Results Water stress, planting density and species identity interactively affected standardized stem elongation in a way that could lead to facilitation during submergence for species that preferably grow in wet soils. Root porosity was affected by the interaction between neighbour presence and time-step. Plant traits were only slightly affected during drought. The calculated neighbour interaction effect indicated facilitation for wetland species during submerged conditions and, after a period to recover from flooding, for species that prefer dry habitats. Conclusions Our results imply that changing plant–plant interactions in response to submergence and to a lesser extent to drought should be considered when predicting vegetation dynamics due to changing hydroclimatic regimes. Moreover, facilitation during a recovery period may enable species maladapted to flooding to persist.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Journal of Vegetation Science},
	author = {Sarneel, Judith M. and Hefting, Mariet M. and Visser, Eric J. W. and Díaz-Sierra, Rubén and Voesenek, Laurentius A. C. J. and Kowalchuk, George A.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvs.13145},
	keywords = {neighbour intensity effect, plant–plant interactions, recovery period, riparian vegetation, stress gradient hypothesis, water stress},
	pages = {e13145},
}

Questions Flooding and drought stress are expected to increase significantly across the world and plant responses to these abiotic changes may be mediated by plant–plant interactions. Stress tolerance and recovery often require a biomass investment that may have consequences for these plant–plant interactions. Therefore, we questioned whether phenotypic plasticity in response to flooding and drought affected the balance between competition and facilitation for species with specific adaptations to drought or flooding. Location Utrecht University. Methods Stem elongation, root porosity, root:shoot ratio and biomass production were measured for six species during drought, well-drained and submerged conditions when grown alone or together with conspecifics. We quantified competition and facilitation as the ‘neighbour intensity effect’ directly after the 10-day treatment and again after a seven-day recovery period in well-drained conditions. Results Water stress, planting density and species identity interactively affected standardized stem elongation in a way that could lead to facilitation during submergence for species that preferably grow in wet soils. Root porosity was affected by the interaction between neighbour presence and time-step. Plant traits were only slightly affected during drought. The calculated neighbour interaction effect indicated facilitation for wetland species during submerged conditions and, after a period to recover from flooding, for species that prefer dry habitats. Conclusions Our results imply that changing plant–plant interactions in response to submergence and to a lesser extent to drought should be considered when predicting vegetation dynamics due to changing hydroclimatic regimes. Moreover, facilitation during a recovery period may enable species maladapted to flooding to persist.

@article{rulli_seasonal_2022,
	title = {Seasonal patterns in nutrient bioavailability in boreal headwater streams},
	volume = {67},
	copyright = {© 2022 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.12064},
	doi = {10.1002/lno.12064},
	abstract = {Changes in nutrient bioavailability due to increased loading of dissolved organic matter (DOM) may impact boreal freshwaters. Yet, the relative bioavailability of carbon (C), nitrogen (N), and phosphorus (P) associated with terrestrial DOM remains poorly understood. We applied short-term bioassays with natural bacterial inocula to determine seasonal variation in bioavailable organic nutrient pools from four boreal headwater streams in northern Sweden. Experiments were designed to exhaust bioavailable nutrients associated with DOM by inducing limiting conditions when all required resources except for the targeted nutrient (C, N, or P) are provided in excess. We hypothesized that the supply of different bioavailable nutrients to streams would reflect seasonal variations in terrestrial demand, hydrology, and temperature. The delivery of bioavailable DOM-associated resources from the four streams were, on average, 2\%, 11\%, and 38\% of the total dissolved organic C, N, and P, respectively, emphasizing the relatively low C bioavailability in these DOM-rich waters. Bioavailable N : P ratios peaked in autumn for all sites, with lower values in winter and spring. Both in terms of relative (\% of total) and absolute bioavailable organic nutrient concentrations, the seasonal pattern was characterized by systematically high values for the autumn period. Furthermore, links between bioavailable resources and temperature and hydrology varied across sites, time periods, and the different elements. Thus, elevated concentrations of bioavailable organic resources in autumn suggest the potential for leaf fall, as well as late season storms that rewet dry soils, to serve as considerable sources of C, N, and P to boreal aquatic ecosystems.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography},
	author = {Rulli, Mayra P. D. and Bergström, Ann-Kristin and Sponseller, Ryan A. and Berggren, Martin},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.12064},
	keywords = {\#nosource},
	pages = {1169--1183},
}

Changes in nutrient bioavailability due to increased loading of dissolved organic matter (DOM) may impact boreal freshwaters. Yet, the relative bioavailability of carbon (C), nitrogen (N), and phosphorus (P) associated with terrestrial DOM remains poorly understood. We applied short-term bioassays with natural bacterial inocula to determine seasonal variation in bioavailable organic nutrient pools from four boreal headwater streams in northern Sweden. Experiments were designed to exhaust bioavailable nutrients associated with DOM by inducing limiting conditions when all required resources except for the targeted nutrient (C, N, or P) are provided in excess. We hypothesized that the supply of different bioavailable nutrients to streams would reflect seasonal variations in terrestrial demand, hydrology, and temperature. The delivery of bioavailable DOM-associated resources from the four streams were, on average, 2%, 11%, and 38% of the total dissolved organic C, N, and P, respectively, emphasizing the relatively low C bioavailability in these DOM-rich waters. Bioavailable N : P ratios peaked in autumn for all sites, with lower values in winter and spring. Both in terms of relative (% of total) and absolute bioavailable organic nutrient concentrations, the seasonal pattern was characterized by systematically high values for the autumn period. Furthermore, links between bioavailable resources and temperature and hydrology varied across sites, time periods, and the different elements. Thus, elevated concentrations of bioavailable organic resources in autumn suggest the potential for leaf fall, as well as late season storms that rewet dry soils, to serve as considerable sources of C, N, and P to boreal aquatic ecosystems.

@article{nota_norway_2022,
	title = {Norway spruce postglacial recolonization of {Fennoscandia}},
	volume = {13},
	copyright = {2022 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-022-28976-4},
	doi = {10.1038/s41467-022-28976-4},
	abstract = {Contrasting theories exist regarding how Norway spruce (Picea abies) recolonized Fennoscandia after the last glaciation and both early Holocene establishments from western microrefugia and late Holocene colonization from the east have been postulated. Here, we show that Norway spruce was present in southern Fennoscandia as early as 14.7 ± 0.1 cal. kyr BP and that the millennia-old clonal spruce trees present today in central Sweden likely arrived with an early Holocene migration from the east. Our findings are based on ancient sedimentary DNA from multiple European sites (N = 15) combined with nuclear and mitochondrial DNA analysis of ancient clonal (N = 135) and contemporary spruce forest trees (N = 129) from central Sweden. Our other findings imply that Norway spruce was present shortly after deglaciation at the margins of the Scandinavian Ice Sheet, and support previously disputed finds of pollen in southern Sweden claiming spruce establishment during the Lateglacial.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Nature Communications},
	author = {Nota, Kevin and Klaminder, Jonatan and Milesi, Pascal and Bindler, Richard and Nobile, Alessandro and van Steijn, Tamara and Bertilsson, Stefan and Svensson, Brita and Hirota, Shun K. and Matsuo, Ayumi and Gunnarsson, Urban and Seppä, Heikki and Väliranta, Minna M. and Wohlfarth, Barbara and Suyama, Yoshihisa and Parducci, Laura},
	month = mar,
	year = {2022},
	note = {Publisher: Nature Publishing Group},
	keywords = {Ecological genetics, Plant evolution},
	pages = {1333},
}

Contrasting theories exist regarding how Norway spruce (Picea abies) recolonized Fennoscandia after the last glaciation and both early Holocene establishments from western microrefugia and late Holocene colonization from the east have been postulated. Here, we show that Norway spruce was present in southern Fennoscandia as early as 14.7 ± 0.1 cal. kyr BP and that the millennia-old clonal spruce trees present today in central Sweden likely arrived with an early Holocene migration from the east. Our findings are based on ancient sedimentary DNA from multiple European sites (N = 15) combined with nuclear and mitochondrial DNA analysis of ancient clonal (N = 135) and contemporary spruce forest trees (N = 129) from central Sweden. Our other findings imply that Norway spruce was present shortly after deglaciation at the margins of the Scandinavian Ice Sheet, and support previously disputed finds of pollen in southern Sweden claiming spruce establishment during the Lateglacial.

@article{norman_effects_2022,
	title = {Effects of {Habitat}-{Specific} {Primary} {Production} on {Fish} {Size}, {Biomass}, and {Production} in {Northern} {Oligotrophic} {Lakes}},
	volume = {25},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-021-00733-6},
	doi = {10.1007/s10021-021-00733-6},
	abstract = {Ecological theory predicts that the relative distribution of primary production across habitats influence fish size structure and biomass production. In this study, we assessed individual, population, and community-level consequences for brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) of variation in estimated habitat specific (benthic and pelagic) and total whole lake (GPPwhole) gross primary production in 27 northern oligotrophic lakes. We found that higher contribution of benthic primary production to GPPwhole was associated with higher community biomass and larger maximum and mean sizes of fish. At the population level, species-specific responses differed. Increased benthic primary production (GPPBenthic) correlated to higher population biomass of brown trout regardless of being alone or in sympatry, while Arctic char responded positively to pelagic primary production (GPPPelagic) in sympatric populations. In sympatric lakes, the maximum size of both species was positively related to both GPPBenthic and the benthic contribution to GPPWhole. In allopatric lakes, brown trout mean and maximum size and Arctic char mean size were positively related to the benthic proportion of GPPWhole. Our results highlight the importance of light-controlled benthic primary production for fish biomass production in oligotrophic northern lakes. Our results further suggest that consequences of ontogenetic asymmetry and niche shifts may cause the distribution of primary production across habitats to be more important than the total ecosystem primary production for fish size, population biomass, and production. Awareness of the relationships between light availability and asymmetric resource production favoring large fish and fish production may allow for cost-efficient and more informed management actions in northern oligotrophic lakes.},
	language = {en},
	number = {7},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Norman, Sven and Nilsson, Karin A. and Klaus, Marcus and Seekell, David and Karlsson, Jan and Byström, Pär},
	month = nov,
	year = {2022},
	keywords = {\#nosource, Arctic char, Benthic primary production, Brown trout, Keywords, Lake productivity, Ontogenetic asymmetry, Pelagic primary production},
	pages = {1555--1570},
}

Ecological theory predicts that the relative distribution of primary production across habitats influence fish size structure and biomass production. In this study, we assessed individual, population, and community-level consequences for brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) of variation in estimated habitat specific (benthic and pelagic) and total whole lake (GPPwhole) gross primary production in 27 northern oligotrophic lakes. We found that higher contribution of benthic primary production to GPPwhole was associated with higher community biomass and larger maximum and mean sizes of fish. At the population level, species-specific responses differed. Increased benthic primary production (GPPBenthic) correlated to higher population biomass of brown trout regardless of being alone or in sympatry, while Arctic char responded positively to pelagic primary production (GPPPelagic) in sympatric populations. In sympatric lakes, the maximum size of both species was positively related to both GPPBenthic and the benthic contribution to GPPWhole. In allopatric lakes, brown trout mean and maximum size and Arctic char mean size were positively related to the benthic proportion of GPPWhole. Our results highlight the importance of light-controlled benthic primary production for fish biomass production in oligotrophic northern lakes. Our results further suggest that consequences of ontogenetic asymmetry and niche shifts may cause the distribution of primary production across habitats to be more important than the total ecosystem primary production for fish size, population biomass, and production. Awareness of the relationships between light availability and asymmetric resource production favoring large fish and fish production may allow for cost-efficient and more informed management actions in northern oligotrophic lakes.

@article{lento_temperature_2022,
	title = {Temperature and spatial connectivity drive patterns in freshwater macroinvertebrate diversity across the {Arctic}},
	volume = {67},
	copyright = {© 2021 The Authors. Freshwater Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2427},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.13805},
	doi = {10.1111/fwb.13805},
	abstract = {Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. We examined benthic macroinvertebrate diversity using a circumpolar dataset of {\textgreater}1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region-scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships. Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions. High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates. The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long-term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science-based management.},
	language = {en},
	number = {1},
	urldate = {2024-03-26},
	journal = {Freshwater Biology},
	author = {Lento, Jennifer and Culp, Joseph M. and Levenstein, Brianna and Aroviita, Jukka and Baturina, Maria A. and Bogan, Daniel and Brittain, John E. and Chin, Krista and Christoffersen, Kirsten S. and Docherty, Catherine and Friberg, Nikolai and Ingimarsson, Finnur and Jacobsen, Dean and Lau, Danny Chun Pong and Loskutova, Olga A. and Milner, Alexander and Mykrä, Heikki and Novichkova, Anna A. and Ólafsson, Jón S. and Schartau, Ann Kristin and Shaftel, Rebecca and Goedkoop, Willem},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.13805},
	keywords = {\#nosource, benthic invertebrates, dispersal, diversity, high latitude, lake, river},
	pages = {159--175},
}

Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. We examined benthic macroinvertebrate diversity using a circumpolar dataset of \textgreater1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region-scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships. Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions. High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates. The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long-term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science-based management.

@article{keen_non-native_2022,
	title = {Non-native species change the tune of tundra soils: {Novel} access to soundscapes of the {Arctic} earthworm invasion},
	volume = {838},
	issn = {0048-9697},
	shorttitle = {Non-native species change the tune of tundra soils},
	url = {https://www.sciencedirect.com/science/article/pii/S004896972203073X},
	doi = {10.1016/j.scitotenv.2022.155976},
	abstract = {Over the last decade, an increasing number of studies have used soundscapes to address diverse ecological questions. Sound represents one of the few sources of information capable of providing in situ insights into processes occurring within opaque soil matrices. To date, the use of soundscapes for soil macrofauna monitoring has been experimentally tested only in controlled laboratory environments. Here we assess the validity of laboratory predictions and explore the use of soil soundscape proxies for monitoring soil macrofauna (i.e., earthworm) activities in an outdoor context. In a common garden experiment in northern Sweden, we constructed outdoor mesocosm plots (N = 36) containing two different Arctic vegetation types (meadow and heath) and introduced earthworms to half of these plots. Earthworms substantially altered the ambient soil soundscape under both vegetation types, as measured by both traditional soundscape indices and frequency band power levels, although their acoustic impacts were expressed differently in heath versus meadow soils. While these findings support the as-of-yet untapped promise of using belowground soundscape analyses to monitor soil ecosystem health, direct acoustic emissions from earthworm activities appear to be an unlikely proxy for tracking worm activities at daily timescales. Instead, earthworms indirectly altered the soil soundscape by ‘re-engineering’ the soil matrix: an effect that was dependent on vegetation type. Our findings suggest that long-term (i.e., seasonal) earthworm activities in natural soil settings can likely be monitored indirectly via their impacts on soundscape measures and acoustic indices. Analyzing soil soundscapes may enable larger-scale monitoring of high-latitude soils and is directly applicable to the specific case of earthworm invasions within Arctic soils, which has recently been identified as a potential threat to the resilience of high-latitude ecosystems. Soil soundscapes could also offer a novel means to monitor soils and soil-plant-faunal interactions in situ across diverse pedogenic, agronomic, and ecological systems.},
	urldate = {2024-03-26},
	journal = {Science of The Total Environment},
	author = {Keen, Sara C. and Wackett, Adrian A. and Willenbring, Jane K. and Yoo, Kyungsoo and Jonsson, Hanna and Clow, Travis and Klaminder, Jonatan},
	month = sep,
	year = {2022},
	keywords = {\#nosource, Acoustic monitoring, Arctic, Earthworm invasion, Ecosystem disturbance, Ecosystem engineer, Soil fauna, Soil organic carbon, Soil structure, Soundscapes},
	pages = {155976},
}

Over the last decade, an increasing number of studies have used soundscapes to address diverse ecological questions. Sound represents one of the few sources of information capable of providing in situ insights into processes occurring within opaque soil matrices. To date, the use of soundscapes for soil macrofauna monitoring has been experimentally tested only in controlled laboratory environments. Here we assess the validity of laboratory predictions and explore the use of soil soundscape proxies for monitoring soil macrofauna (i.e., earthworm) activities in an outdoor context. In a common garden experiment in northern Sweden, we constructed outdoor mesocosm plots (N = 36) containing two different Arctic vegetation types (meadow and heath) and introduced earthworms to half of these plots. Earthworms substantially altered the ambient soil soundscape under both vegetation types, as measured by both traditional soundscape indices and frequency band power levels, although their acoustic impacts were expressed differently in heath versus meadow soils. While these findings support the as-of-yet untapped promise of using belowground soundscape analyses to monitor soil ecosystem health, direct acoustic emissions from earthworm activities appear to be an unlikely proxy for tracking worm activities at daily timescales. Instead, earthworms indirectly altered the soil soundscape by ‘re-engineering’ the soil matrix: an effect that was dependent on vegetation type. Our findings suggest that long-term (i.e., seasonal) earthworm activities in natural soil settings can likely be monitored indirectly via their impacts on soundscape measures and acoustic indices. Analyzing soil soundscapes may enable larger-scale monitoring of high-latitude soils and is directly applicable to the specific case of earthworm invasions within Arctic soils, which has recently been identified as a potential threat to the resilience of high-latitude ecosystems. Soil soundscapes could also offer a novel means to monitor soils and soil-plant-faunal interactions in situ across diverse pedogenic, agronomic, and ecological systems.

@article{baladron_trapped_2022,
	title = {Trapped between drowning and desiccation: {Riverine} plants under hydropeaking},
	volume = {829},
	issn = {0048-9697},
	shorttitle = {Trapped between drowning and desiccation},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969722015443},
	doi = {10.1016/j.scitotenv.2022.154451},
	abstract = {Hydropeaking is part of hydropower production. The discontinuous release of turbined water during hydropeaking generates sudden rise and falls of the water levels, as well as extended droughts. These artificial flow fluctuations impose challenging growing conditions for riverine vegetation. In order to identify vulnerable/resistant plant species to hydropeaking and to evaluate the impact of contrasting hydropeaking scenarios (simplified (i.e., sudden deep floods, frequent soil saturation and drought) and real-life, power plant-induced scenarios), we measured germination, survival, and morphological and physiological attributes of a selection of 14 plant species commonly found along riparian areas. Species were subject to different hydropeaking scenarios during three months (vegetative period) in the field and in a greenhouse. Half of the species performed worse under hydropeaking in comparison to the control (e.g., less germination and biomass, lower growth rates, reduced stem and root length, physiological stress) but none of the tested hydropeaking scenarios was clearly more disruptive than others. Betula pubescens, Alnus incana and Filipendula ulmifolia showed the largest vulnerability to hydropeaking, while other species (e.g., Carex acuta) were resistant to it. Both in the field and in the greenhouse, plants in perturbed scenarios accumulated more 13C than in the control scenario indicating limited capacity to perform 13C isotope discrimination and evidencing plant physiological stress. The highest 13C abundances were found under drought or flooding conditions in the greenhouse, and under the highest hydropeaking intensities in the field (e.g., Betula pubescens). Our results suggest that any hydropeaking scheme can be equally detrimental in terms of plant performance. Hydropeaking schemes that combine periods of severe drought with long and frequent flooding episodes may create a hostile environment for riverine species. Further research on “hydropeaking-tolerant” plant traits is key to draw the boundaries beyond which riverine species can germinate, grow and complete their life cycle under hydropeaking.},
	urldate = {2024-03-26},
	journal = {Science of The Total Environment},
	author = {Baladrón, Alejandro and Bejarano, María Dolores and Sarneel, Judith M. and Boavida, Isabel},
	month = jul,
	year = {2022},
	keywords = {Drought, Flooding, Hydropeaking, Plant morphology, Riverine vegetation, Stoichiometry},
	pages = {154451},
}

Hydropeaking is part of hydropower production. The discontinuous release of turbined water during hydropeaking generates sudden rise and falls of the water levels, as well as extended droughts. These artificial flow fluctuations impose challenging growing conditions for riverine vegetation. In order to identify vulnerable/resistant plant species to hydropeaking and to evaluate the impact of contrasting hydropeaking scenarios (simplified (i.e., sudden deep floods, frequent soil saturation and drought) and real-life, power plant-induced scenarios), we measured germination, survival, and morphological and physiological attributes of a selection of 14 plant species commonly found along riparian areas. Species were subject to different hydropeaking scenarios during three months (vegetative period) in the field and in a greenhouse. Half of the species performed worse under hydropeaking in comparison to the control (e.g., less germination and biomass, lower growth rates, reduced stem and root length, physiological stress) but none of the tested hydropeaking scenarios was clearly more disruptive than others. Betula pubescens, Alnus incana and Filipendula ulmifolia showed the largest vulnerability to hydropeaking, while other species (e.g., Carex acuta) were resistant to it. Both in the field and in the greenhouse, plants in perturbed scenarios accumulated more 13C than in the control scenario indicating limited capacity to perform 13C isotope discrimination and evidencing plant physiological stress. The highest 13C abundances were found under drought or flooding conditions in the greenhouse, and under the highest hydropeaking intensities in the field (e.g., Betula pubescens). Our results suggest that any hydropeaking scheme can be equally detrimental in terms of plant performance. Hydropeaking schemes that combine periods of severe drought with long and frequent flooding episodes may create a hostile environment for riverine species. Further research on “hydropeaking-tolerant” plant traits is key to draw the boundaries beyond which riverine species can germinate, grow and complete their life cycle under hydropeaking.

@article{palmtag_high_2022,
	title = {A high spatial resolution soil carbon and nitrogen dataset for the northern permafrost region based on circumpolar land cover upscaling},
	volume = {14},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203690},
	doi = {10.5194/essd-14-4095-2022},
	abstract = {Soils in the northern high latitudes are a key component in the global carbon cycle; the northern permafrost region covers 22\% of the Northern Hemisphere land surface area and holds almost twice as ...},
	language = {eng},
	number = {9},
	urldate = {2024-03-26},
	journal = {Earth System Science Data},
	author = {Palmtag, Juri and Obu, Jaroslav and Kuhry, Peter and Richter, Andreas and Siewert, Matthias B. and Weiss, Niels and Westermann, Sebastian and Hugelius, Gustaf},
	year = {2022},
	note = {Publisher: Copernicus Publications},
	pages = {4095--4110},
}

Soils in the northern high latitudes are a key component in the global carbon cycle; the northern permafrost region covers 22% of the Northern Hemisphere land surface area and holds almost twice as ...

@article{rixen_winters_2022,
	title = {Winters are changing : snow effects on {Arctic} and alpine tundra ecosystems},
	volume = {8},
	shorttitle = {Winters are changing},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-218120},
	doi = {10.1139/as-2020-0058},
	abstract = {Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the gr ...},
	language = {eng},
	number = {3},
	urldate = {2024-03-26},
	journal = {Arctic Science},
	author = {Rixen, Christian and Hoye, Toke Thomas and Macek, Petr and Aerts, Rien and Alatalo, Juha M. and Anderson, Jill T. and Arnold, Pieter A. and Barrio, Isabel C. and Bjerke, Jarle W. and Bjorkman, Mats P. and Blok, Daan and Blume-Werry, Gesche and Boike, Julia and Bokhorst, Stef and Carbognani, Michele and Christiansen, Casper T. and Convey, Peter and Cooper, Elisabeth J. and Cornelissen, J. Hans C. and Coulson, Stephen J. and Dorrepaal, Ellen and Elberling, Bo and Elmendorf, Sarah C. and Elphinstone, Cassandra and Forte, T'ai G. W. and Frei, Esther R. and Geange, Sonya R. and Gehrmann, Friederike and Gibson, Casey and Grogan, Paul and Halbritter, Aud Helen and Harte, John and Henry, Gregory H. R. and Inouye, David W. and Irwin, Rebecca E. and Jespersen, Gus and Jonsdottir, Ingibjorg Svala and Jung, Ji Young and Klinges, David H. and Kudo, Gaku and Lamsa, Juho and Lee, Hanna and Lembrechts, Jonas J. and Lett, Signe and Lynn, Joshua Scott and Mann, Hjalte M. R. and Mastepanov, Mikhail and Morse, Jennifer and Myers-Smith, Isla H. and Olofsson, Johan and Paavola, Riku and Petraglia, Alessandro and Phoenix, Gareth K. and Semenchuk, Philipp and Siewert, Matthias B. and Slatyer, Rachel and Spasojevic, Marko J. and Suding, Katharine and Sullivan, Patrick and Thompson, Kimberly L. and Vaisanen, Maria and Vandvik, Vigdis and Venn, Susanna and Walz, Josefine and Way, Robert and Welker, Jeffrey M. and Wipf, Sonja and Zong, Shengwei},
	year = {2022},
	note = {Publisher: Canadian Science Publishing},
	keywords = {\#nosource},
	pages = {572--608},
}

Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the gr ...

@article{mosquera_co-occurrence_2022,
	title = {Co-occurrence of browning and oligotrophication in a boreal stream network},
	volume = {67},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-199209},
	doi = {10.1002/lno.12205},
	abstract = {The relative supply of carbon (C), nitrogen (N), and phosphorus (P) to freshwater ecosystems is of fundamental importance to aquatic productivity, nutrient cycling, and food web dynamics. In northe ...},
	language = {eng},
	number = {10},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Mosquera, Virginia and Maher Hasselquist, Eliza and Sponseller, Ryan A. and Laudon, Hjalmar},
	year = {2022},
	note = {Publisher: John Wiley \& Sons},
	pages = {2325--2339},
}

The relative supply of carbon (C), nitrogen (N), and phosphorus (P) to freshwater ecosystems is of fundamental importance to aquatic productivity, nutrient cycling, and food web dynamics. In northe ...

@article{puts_landscape_2022,
	title = {Landscape determinants of pelagic and benthic primary production in northern lakes},
	volume = {28},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-194518},
	doi = {10.1111/gcb.16409},
	abstract = {Global change affects gross primary production (GPP) in benthic and pelagic habitats of northern lakes by influencing catchment characteristics and lake water biogeochemistry. However, how changes  ...},
	language = {eng},
	number = {23},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Puts, Isolde C. and Ask, Jenny and Siewert, Matthias B. and Sponseller, Ryan A. and Hessen, Dag O. and Bergström, Ann-Kristin},
	year = {2022},
	note = {Publisher: John Wiley \& Sons},
	pages = {7063--7077},
}

Global change affects gross primary production (GPP) in benthic and pelagic habitats of northern lakes by influencing catchment characteristics and lake water biogeochemistry. However, how changes ...

@article{myrstener_resolving_2022,
	title = {Resolving the {Drivers} of {Algal} {Nutrient} {Limitation} from {Boreal} to {Arctic} {Lakes} and {Streams}},
	volume = {25},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-194276},
	doi = {10.1007/s10021-022-00759-4},
	abstract = {Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while primary producer growth is sensitive to nut ...},
	language = {eng},
	urldate = {2024-03-26},
	journal = {Ecosystems (New York. Print)},
	author = {Myrstener, Maria and Fork, Megan L. and Bergström, Ann-Kristin and Puts, Isolde and Hauptmann, Demian and Isles, Peter D. F. and Burrows, Ryan M. and Sponseller, Ryan A.},
	year = {2022},
	note = {Publisher: Springer-Verlag New York},
	pages = {1682--1699},
}

Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while primary producer growth is sensitive to nut ...

@article{lim_carbon_2022,
	title = {Carbon emission and export from the {Ket} {River}, western {Siberia}},
	volume = {19},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-202587},
	doi = {10.5194/bg-19-5859-2022},
	abstract = {Despite recent progress in the understanding of the carbon (C) cycle of Siberian permafrost-affected rivers, spatial and seasonal dynamics of C export and emission from medium-sized rivers (50 000- ...},
	language = {eng},
	number = {24},
	urldate = {2024-03-26},
	journal = {Biogeosciences},
	author = {Lim, Artem G. and Krickov, Ivan V. and Vorobyev, Sergey N. and Korets, Mikhail A. and Kopysov, Sergey and Shirokova, Liudmila S. and Karlsson, Jan and Pokrovsky, Oleg S.},
	year = {2022},
	note = {Publisher: Copernicus Publications},
	pages = {5859--5877},
}

Despite recent progress in the understanding of the carbon (C) cycle of Siberian permafrost-affected rivers, spatial and seasonal dynamics of C export and emission from medium-sized rivers (50 000- ...

@article{lau_multitrophic_2022,
	title = {Multitrophic biodiversity patterns and environmental descriptors of sub‐{Arctic} lakes in northern {Europe}},
	volume = {67},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-177612},
	doi = {10.1111/fwb.13477},
	abstract = {1. Arctic and sub‐Arctic lakes in northern Europe are increasingly threatened by climate change, which can affect their biodiversity directly by shifting thermal and hydrological regimes, and indir ...},
	language = {eng},
	number = {1},
	urldate = {2024-03-26},
	journal = {Freshwater Biology},
	author = {Lau, Danny C. P. and Christoffersen, Kirsten S. and Erkinaro, Jaakko and Hayden, Brian and Heino, Jani and Hellsten, Seppo and Holmgren, Kerstin and Kahilainen, Kimmo K. and Kahlert, Maria and Satu Maaria, Karjalainen and Karlsson, Jan and Forsström, Laura and Lento, Jennifer and Mjelde, Marit and Ruuhijärvi, Jukka and Sandøy, Steinar and Schartau, Ann Kristin and Svenning, Martin-A. and Vrede, Tobias and Goedkoop, Willem},
	year = {2022},
	note = {Publisher: John Wiley \& Sons},
	pages = {30--48},
}

1. Arctic and sub‐Arctic lakes in northern Europe are increasingly threatened by climate change, which can affect their biodiversity directly by shifting thermal and hydrological regimes, and indir ...

@article{huser_spatial_2022,
	title = {Spatial and temporal variation in {Arctic} freshwater chemistry : {Reflecting} climate-induced landscape alterations and a changing template for biodiversity},
	volume = {67},
	shorttitle = {Spatial and temporal variation in {Arctic} freshwater chemistry},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-177313},
	doi = {10.1111/fwb.13645},
	abstract = {1. Freshwater chemistry across the circumpolar region was characterised using a pan-Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970-1985), Mid ...},
	language = {eng},
	number = {1},
	urldate = {2024-03-26},
	journal = {Freshwater Biology},
	author = {Huser, Brian J. and Futter, Martyn N. and Bogan, Daniel and Brittain, John E. and Culp, Joseph M. and Goedkoop, Willem and Gribovskaya, Iliada and Karlsson, Jan and Lau, Danny C. P. and Ruhland, Kathleen M. and Schartau, Ann Kristin and Shaftel, Rebecca and Smol, John P. and Vrede, Tobias and Lento, Jennifer},
	year = {2022},
	note = {Publisher: John Wiley \& Sons},
	keywords = {\#nosource, biogeochemistry, eutrophication, lakes, oligotrophication, rivers},
	pages = {14--29},
}

1. Freshwater chemistry across the circumpolar region was characterised using a pan-Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970-1985), Mid ...

@phdthesis{linden_circumpolar_2022,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Circumpolar impacts of herbivores on {Arctic} tundra vegetation},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-194189},
	abstract = {Arctic tundra vegetation provides many ecological services that have implications for the global climate. However, the tundra biome is currently changing in response to increasing temperatures. Her ...},
	language = {eng},
	urldate = {2023-07-25},
	school = {Umeå University},
	author = {Lindén, Elin},
	collaborator = {Olofsson, Johan and Sundqvist, Maja K. and te Beest, Mariska},
	year = {2022},
	note = {Publisher: Umeå Universitet},
	keywords = {⛔ No DOI found},
}

Arctic tundra vegetation provides many ecological services that have implications for the global climate. However, the tundra biome is currently changing in response to increasing temperatures. Her ...

@article{walker_lowland_2022,
	title = {Lowland plant arrival in alpine ecosystems facilitates a decrease in soil carbon content under experimental climate warming},
	volume = {11},
	issn = {2050-084X},
	url = {https://doi.org/10.7554/eLife.78555},
	doi = {10.7554/eLife.78555},
	abstract = {Climate warming is releasing carbon from soils around the world, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown. Here, we used two whole-community transplant experiments and a follow-up glasshouse experiment to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences soil carbon content under warming. We found that warming (transplantation to low elevation) led to a negligible decrease in alpine soil carbon content, but its effects became significant and 52\% ± 31\% (mean ± 95\% confidence intervals) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that decreases in soil carbon content likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration, and CO2 release under warming. Our findings suggest that warming-induced range expansions of herbaceous plants have the potential to alter climate feedbacks from this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.},
	journal = {eLife},
	author = {Walker, Tom WN and Gavazov, Konstantin and Guillaume, Thomas and Lambert, Thibault and Mariotte, Pierre and Routh, Devin and Signarbieux, Constant and Block, Sebastián and Münkemüller, Tamara and Nomoto, Hanna and Crowther, Thomas W and Richter, Andreas and Buttler, Alexandre and Alexander, Jake M},
	editor = {Schmid, Bernhard and Schuman, Meredith C and Schmid, Bernhard and Jing, Xin and Zhu, Biao},
	month = may,
	year = {2022},
	note = {Publisher: eLife Sciences Publications, Ltd},
	keywords = {carbon cycling, climate change, plant ecophysiology, plant redistributions, plant–soil interactions, soil microbes},
	pages = {e78555},
}

Climate warming is releasing carbon from soils around the world, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown. Here, we used two whole-community transplant experiments and a follow-up glasshouse experiment to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences soil carbon content under warming. We found that warming (transplantation to low elevation) led to a negligible decrease in alpine soil carbon content, but its effects became significant and 52% ± 31% (mean ± 95% confidence intervals) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that decreases in soil carbon content likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration, and CO2 release under warming. Our findings suggest that warming-induced range expansions of herbaceous plants have the potential to alter climate feedbacks from this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.

@article{hagenberg_vegetation_2022,
	title = {Vegetation change on mountaintops in northern {Sweden}: {Stable} vascular-plant but reordering of lichen and bryophyte communities},
	volume = {37},
	issn = {0912-3814},
	url = {https://doi.org/10.1111/1440-1703.12359},
	doi = {10.1111/1440-1703.12359},
	abstract = {Abstract Alpine ecosystems harbor remarkably diverse and distinct plant communities that are characteristically limited to harsh, and cold climatic conditions. As a result of thermal limitation to species occurrence, mountainous ecosystems are considered to be particularly sensitive to climate change. Our understanding of the impact of climate change is mainly based on vascular plants however, whereas cryptogams (i.e., lichens and bryophytes) are generally neglected or simply considered as one functional group. Here we aimed to improve our understanding of the drivers underlying temporal changes in vegetation of alpine ecosystems. To this end, we repeatedly surveyed the vegetation on four mountain summits along an elevational gradient in northern Sweden spanning a 19-year period. Our results show that the vascular plant communities remained relatively stable throughout the study period, despite fluctuations in terms of ground cover and species richness of shrubs and graminoids. In contrast, both lichens and bryophytes substantially decreased in cover and diversity, leading to alterations in community composition that were unrelated to vascular plant cover. Thermophilization of the vascular plant community was found only on the two intermediate summits. Our findings are only partially consistent with (long-term) climate-change impacts, and we argue that local non-climatic drivers such as herbivory might offset vegetation responses to warming. Hence, we underline the importance of considering local non-climatic drivers when evaluating temporal vegetation change in biologically complex systems.},
	number = {6},
	urldate = {2023-07-22},
	journal = {Ecological Research},
	author = {Hagenberg, Liyenne Wu Chen and Vanneste, Thomas and Opedal, Øystein H. and Petlund, Hanne Torsdatter and Björkman, Mats P. and Björk, Robert G. and Holien, Håkon and Limpens, Juul and Molau, Ulf and Graae, Bente Jessen and De Frenne, Pieter},
	month = nov,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {alpine vegetation, climate change impact, ecosystem change, lichens and bryophytes, non-climatic drivers},
	pages = {722--737},
}

Abstract Alpine ecosystems harbor remarkably diverse and distinct plant communities that are characteristically limited to harsh, and cold climatic conditions. As a result of thermal limitation to species occurrence, mountainous ecosystems are considered to be particularly sensitive to climate change. Our understanding of the impact of climate change is mainly based on vascular plants however, whereas cryptogams (i.e., lichens and bryophytes) are generally neglected or simply considered as one functional group. Here we aimed to improve our understanding of the drivers underlying temporal changes in vegetation of alpine ecosystems. To this end, we repeatedly surveyed the vegetation on four mountain summits along an elevational gradient in northern Sweden spanning a 19-year period. Our results show that the vascular plant communities remained relatively stable throughout the study period, despite fluctuations in terms of ground cover and species richness of shrubs and graminoids. In contrast, both lichens and bryophytes substantially decreased in cover and diversity, leading to alterations in community composition that were unrelated to vascular plant cover. Thermophilization of the vascular plant community was found only on the two intermediate summits. Our findings are only partially consistent with (long-term) climate-change impacts, and we argue that local non-climatic drivers such as herbivory might offset vegetation responses to warming. Hence, we underline the importance of considering local non-climatic drivers when evaluating temporal vegetation change in biologically complex systems.

@article{andresen_patterns_2022,
	title = {Patterns of free amino acids in tundra soils reflect mycorrhizal type, shrubification, and warming},
	volume = {32},
	issn = {1432-1890},
	url = {https://doi.org/10.1007/s00572-022-01075-4},
	doi = {10.1007/s00572-022-01075-4},
	abstract = {The soil nitrogen (N) cycle in cold terrestrial ecosystems is slow and organically bound N is an important source of N for plants in these ecosystems. Many plant species can take up free amino acids from these infertile soils, either directly or indirectly via their mycorrhizal fungi. We hypothesized that plant community changes and local plant community differences will alter the soil free amino acid pool and composition; and that long-term warming could enhance this effect. To test this, we studied the composition of extractable free amino acids at five separate heath, meadow, and bog locations in subarctic and alpine Scandinavia, with long-term (13 to 24 years) warming manipulations. The plant communities all included a mixture of ecto-, ericoid-, and arbuscular mycorrhizal plant species. Vegetation dominated by grasses and forbs with arbuscular and non-mycorrhizal associations showed highest soil free amino acid content, distinguishing them from the sites dominated by shrubs with ecto- and ericoid-mycorrhizal associations. Warming increased shrub and decreased moss cover at two sites, and by using redundancy analysis, we found that altered soil free amino acid composition was related to this plant cover change. From this, we conclude that the mycorrhizal type is important in controlling soil N cycling and that expansion of shrubs with ectomycorrhiza (and to some extent ericoid mycorrhiza)  can help retain N within the ecosystems by tightening the N cycle.},
	number = {3},
	journal = {Mycorrhiza},
	author = {Andresen, Louise C. and Bodé, Samuel and Björk, Robert G. and Michelsen, Anders and Aerts, Rien and Boeckx, Pascal and Cornelissen, J. Hans C. and Klanderud, Kari and van Logtestijn, Richard S. P. and Rütting, Tobias},
	month = jul,
	year = {2022},
	pages = {305--313},
}

The soil nitrogen (N) cycle in cold terrestrial ecosystems is slow and organically bound N is an important source of N for plants in these ecosystems. Many plant species can take up free amino acids from these infertile soils, either directly or indirectly via their mycorrhizal fungi. We hypothesized that plant community changes and local plant community differences will alter the soil free amino acid pool and composition; and that long-term warming could enhance this effect. To test this, we studied the composition of extractable free amino acids at five separate heath, meadow, and bog locations in subarctic and alpine Scandinavia, with long-term (13 to 24 years) warming manipulations. The plant communities all included a mixture of ecto-, ericoid-, and arbuscular mycorrhizal plant species. Vegetation dominated by grasses and forbs with arbuscular and non-mycorrhizal associations showed highest soil free amino acid content, distinguishing them from the sites dominated by shrubs with ecto- and ericoid-mycorrhizal associations. Warming increased shrub and decreased moss cover at two sites, and by using redundancy analysis, we found that altered soil free amino acid composition was related to this plant cover change. From this, we conclude that the mycorrhizal type is important in controlling soil N cycling and that expansion of shrubs with ectomycorrhiza (and to some extent ericoid mycorrhiza) can help retain N within the ecosystems by tightening the N cycle.

@article{cael_size-distribution_2022,
	title = {The size-distribution of earth’s lakes and ponds: {Limits} to power-law behavior},
	volume = {10},
	doi = {10.3389/fenvs.2022.888735},
	journal = {Frontiers in Environmental Science},
	author = {Cael, B. and Biggs, Jeremy and Seekell, D.},
	month = aug,
	year = {2022},
	pages = {888735},
}

@article{spitzer_root_2022,
	title = {Root traits and soil micro-organisms as drivers of plant–soil feedbacks within the sub-arctic tundra meadow},
	volume = {110},
	issn = {0022-0477},
	url = {https://doi.org/10.1111/1365-2745.13814},
	doi = {10.1111/1365-2745.13814},
	abstract = {Abstract Plant?soil feedback (PSF) results from the influence of plants on the composition and abundance of various taxa and functional groups of soil micro-organisms, and their reciprocal effects on the plants. However, little is understood about the importance of fine root traits and root economic strategies in moderating microbial-driven PSF. We examined the relationships between PSF and 11 chemical and morphological root traits from 18 sub-arctic meadow plant species, as well as the soil microbial community composition which we characterized using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We also investigated the importance of the root economics spectrum in influencing PSF, because it indicates plant below-ground economic strategies via trade-offs between resource acquisition and conservation. When we considered the entire root economics spectrum, we found that PSFs were more negative when root trait values were more acquisitive across the 18 species. In addition, PSF was more negative when values of root nitrogen content and root forks per root length were higher, and more positive when root dry matter content was higher. We additionally identified two fungal orders that were negatively related to PSF. However, we found no evidence that root traits influenced PSF through its relationship with these fungal orders. Synthesis. Our results provide evidence that for some fine root traits, the root economics spectrum and some fungal orders have an important role in influencing PSF. By investigating the roles of soil micro-organisms and fine root traits in driving PSF, this study enables us to better understand root trait?microbial linkages across species and therefore offers new insights about the mechanisms that underpin PSFs and ultimately plant community assembly.},
	number = {2},
	urldate = {2023-07-22},
	journal = {Journal of Ecology},
	author = {Spitzer, Clydecia M. and Wardle, David A. and Lindahl, Björn D. and Sundqvist, Maja K. and Gundale, Michael J. and Fanin, Nicolas and Kardol, Paul},
	month = feb,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {arctic, fine root traits, functional ecology, fungi, plant–soil feedback, root economics spectrum, tundra ecosystems},
	pages = {466--478},
}

Abstract Plant?soil feedback (PSF) results from the influence of plants on the composition and abundance of various taxa and functional groups of soil micro-organisms, and their reciprocal effects on the plants. However, little is understood about the importance of fine root traits and root economic strategies in moderating microbial-driven PSF. We examined the relationships between PSF and 11 chemical and morphological root traits from 18 sub-arctic meadow plant species, as well as the soil microbial community composition which we characterized using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We also investigated the importance of the root economics spectrum in influencing PSF, because it indicates plant below-ground economic strategies via trade-offs between resource acquisition and conservation. When we considered the entire root economics spectrum, we found that PSFs were more negative when root trait values were more acquisitive across the 18 species. In addition, PSF was more negative when values of root nitrogen content and root forks per root length were higher, and more positive when root dry matter content was higher. We additionally identified two fungal orders that were negatively related to PSF. However, we found no evidence that root traits influenced PSF through its relationship with these fungal orders. Synthesis. Our results provide evidence that for some fine root traits, the root economics spectrum and some fungal orders have an important role in influencing PSF. By investigating the roles of soil micro-organisms and fine root traits in driving PSF, this study enables us to better understand root trait?microbial linkages across species and therefore offers new insights about the mechanisms that underpin PSFs and ultimately plant community assembly.

@article{bergstrom_biomass_2022,
	title = {Biomass, community composition and {N}:{P} recycling ratios of zooplankton in northern high-latitude lakes with contrasting levels of {N} deposition and dissolved organic carbon},
	volume = {67},
	issn = {0046-5070},
	url = {https://doi.org/10.1111/fwb.13956},
	doi = {10.1111/fwb.13956},
	abstract = {Abstract Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved. In 33 Swedish headwater lakes across subarctic-to-boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll-a [Chl-a], Chl-a:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models. There was a large-scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl-a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass. Zooplankton community composition differed in the north vs. south, with a dominance of N-requiring calanoid copepods with high N:P in the north and P-requiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition. The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing seston N:P and/or by enhancing calanoid copepod dominance in the zooplankton community. Our findings suggest that the combination of declining N deposition and increasing lake browning in northern high-latitude lakes will reduce phytoplankton biomass, but will concurrently enhance seston mineral quality and probably also zooplankton biomass and their recycling efficiency of P relative to N.},
	number = {9},
	urldate = {2023-07-22},
	journal = {Freshwater Biology},
	author = {Bergström, Ann-Kristin and Lau, Danny C. P. and Isles, Peter D. F. and Jonsson, Anders and Creed, Irena F.},
	month = sep,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {C:N:P stoichiometry, biomass, community composition, plankton, subarctic-to-boreal},
	pages = {1508--1520},
}

Abstract Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved. In 33 Swedish headwater lakes across subarctic-to-boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll-a [Chl-a], Chl-a:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models. There was a large-scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl-a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass. Zooplankton community composition differed in the north vs. south, with a dominance of N-requiring calanoid copepods with high N:P in the north and P-requiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition. The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing seston N:P and/or by enhancing calanoid copepod dominance in the zooplankton community. Our findings suggest that the combination of declining N deposition and increasing lake browning in northern high-latitude lakes will reduce phytoplankton biomass, but will concurrently enhance seston mineral quality and probably also zooplankton biomass and their recycling efficiency of P relative to N.

@article{scharn_limited_2022,
	title = {Limited decadal growth of mountain birch saplings has minor impact on surrounding tundra vegetation},
	volume = {12},
	issn = {2045-7758},
	url = {https://doi.org/10.1002/ece3.9028},
	doi = {10.1002/ece3.9028},
	abstract = {Abstract Temperatures over the Arctic region are increasing at three times the rate of the global average. Consequently, Arctic vegetation is changing and trees are encroaching into the tundra. In this study, we examine the establishment and growth of mountain birch (Betula pubescens ssp. tortuosa), which forms the treeline in subarctic Europe, and its impact on community composition across the treeline ecotone nearby Abisko, Sweden. Birch advancement along elevational gradients was studied by comparing data collected in 2016 with data collected 10 and 15?years previously. Species identity, cover, and phylogenetic relatedness were used to assess the impact of birch encroachment on community composition. Our results show that birch occurrence above the treeline did not affect plant community composition, probably owing to the observed lack of significant growth due to herbivore browsing, nitrogen limitation, or a reduction in snow cover. Independent of birch performance, the tundra community structure shifted toward a novel community dissimilar from the forest plant community found below the treeline. Taken together, our findings are explained by species-specific responses to climate change, rather than by a linear forest advance. Future treeline advancements are likely more restricted than previously expected.},
	number = {6},
	urldate = {2023-07-22},
	journal = {Ecology and Evolution},
	author = {Scharn, Ruud and Negri, Isabel S. and Sundqvist, Maja K. and Løkken, Jørn O. and Bacon, Christine D. and Antonelli, Alexandre and Hofgaard, Annika and Nilsson, R. Henrik and Björk, Robert G.},
	month = jun,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Betula pubescens, Oroarctic, climate change, phylogenetic diversity, plant community structure, treeline advance},
	pages = {e9028},
}

Abstract Temperatures over the Arctic region are increasing at three times the rate of the global average. Consequently, Arctic vegetation is changing and trees are encroaching into the tundra. In this study, we examine the establishment and growth of mountain birch (Betula pubescens ssp. tortuosa), which forms the treeline in subarctic Europe, and its impact on community composition across the treeline ecotone nearby Abisko, Sweden. Birch advancement along elevational gradients was studied by comparing data collected in 2016 with data collected 10 and 15?years previously. Species identity, cover, and phylogenetic relatedness were used to assess the impact of birch encroachment on community composition. Our results show that birch occurrence above the treeline did not affect plant community composition, probably owing to the observed lack of significant growth due to herbivore browsing, nitrogen limitation, or a reduction in snow cover. Independent of birch performance, the tundra community structure shifted toward a novel community dissimilar from the forest plant community found below the treeline. Taken together, our findings are explained by species-specific responses to climate change, rather than by a linear forest advance. Future treeline advancements are likely more restricted than previously expected.

@article{wedegartner_hiking_2022,
	title = {Hiking trails shift plant species' realized climatic niches and locally increase species richness},
	volume = {28},
	issn = {1366-9516},
	url = {https://doi.org/10.1111/ddi.13552},
	doi = {10.1111/ddi.13552},
	abstract = {Abstract Aim The presence and use of trails may change plant species' realized climatic niches via modified abiotic and biotic conditions including propagule transport, allowing competition-pressed alpine species to expand their rear edges towards warmer locations and lowland species to extend their leading edges towards cooler locations. We investigated whether mountain trails indeed act as corridors for colonization and shift species' realized climatic niches, resulting in higher species richness in trailsides. Location Dovrefjell and Abisko area in the Scandes mountains of Norway and Sweden. Methods We surveyed plant community composition and disturbances along 16 hiking trails in summer 2018 (Dovrefjell) and 2019 (Abisko). We linked changes in species' realized climatic niches to their climatic optimum and variation in species richness to climate, trail effects and resident plant community characteristics. Results Plant species richness was on average 24\% greater in trailside than in interior vegetation plots. Proximity to trails accounted for 9\% and climatic harshness for 55\% of variation in species richness explained in our model. Trailsides increased in richness, especially in relatively species-poor sites and close to introduction points (each accounting for 24\% of variation in our model of species gains). Shifts in rear edges and optima of realized climatic niches along trails related to species' undisturbed climatic optimum, with alpine species being more likely to move into warmer locations. While some disturbance-associated species shifted their leading edges towards colder locations, contrary to expectations this was not the case for lowland species. Overall, shifts in climatic niches resulted in more species' niches overlapping in trailsides than in the interior vegetation. Main conclusion Trails can locally increase species richness by creating opportunities for colonizing species and weaker competitors. Because of prevailing disturbance, they may even provide opportunities for persistence and downward expansion of alpine species, aiding conservation efforts.},
	number = {7},
	urldate = {2023-07-22},
	journal = {Diversity and Distributions},
	author = {Wedegärtner, Ronja E. M. and Lembrechts, Jonas J. and van der Wal, René and Barros, Agustina and Chauvin, Aurélie and Janssens, Ilias and Graae, Bente Jessen},
	month = jul,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {alpine plants, biotic interactions, climate gradient, disturbance, mountain trails, realized niche, species range shifts},
	pages = {1416--1429},
}

Abstract Aim The presence and use of trails may change plant species' realized climatic niches via modified abiotic and biotic conditions including propagule transport, allowing competition-pressed alpine species to expand their rear edges towards warmer locations and lowland species to extend their leading edges towards cooler locations. We investigated whether mountain trails indeed act as corridors for colonization and shift species' realized climatic niches, resulting in higher species richness in trailsides. Location Dovrefjell and Abisko area in the Scandes mountains of Norway and Sweden. Methods We surveyed plant community composition and disturbances along 16 hiking trails in summer 2018 (Dovrefjell) and 2019 (Abisko). We linked changes in species' realized climatic niches to their climatic optimum and variation in species richness to climate, trail effects and resident plant community characteristics. Results Plant species richness was on average 24% greater in trailside than in interior vegetation plots. Proximity to trails accounted for 9% and climatic harshness for 55% of variation in species richness explained in our model. Trailsides increased in richness, especially in relatively species-poor sites and close to introduction points (each accounting for 24% of variation in our model of species gains). Shifts in rear edges and optima of realized climatic niches along trails related to species' undisturbed climatic optimum, with alpine species being more likely to move into warmer locations. While some disturbance-associated species shifted their leading edges towards colder locations, contrary to expectations this was not the case for lowland species. Overall, shifts in climatic niches resulted in more species' niches overlapping in trailsides than in the interior vegetation. Main conclusion Trails can locally increase species richness by creating opportunities for colonizing species and weaker competitors. Because of prevailing disturbance, they may even provide opportunities for persistence and downward expansion of alpine species, aiding conservation efforts.

@article{bottone_sodium_2022,
	title = {Sodium hypochlorite as an oxidizing agent for removal of soil organic matter before microplastics analyses},
	volume = {51},
	issn = {0047-2425},
	url = {https://doi.org/10.1002/jeq2.20321},
	doi = {10.1002/jeq2.20321},
	abstract = {Abstract The omnipresence of microplastics (MPs) across Earth's surface has raised concerns about their environmental impact and created an urgent need for methods to identify them in complex soil and sedimentary matrices. However, detecting MPs in the O horizons of soils is difficult because plastic polymers share many physical and chemical properties with natural soil organic matter (SOM). In this study, we assessed whether sodium hypochlorite (NaOCl), a reagent that can oxidize SOM and simultaneously preserve mineral constituents, can be used for MP analysis and characterization in soil environments. In addition, we scrutinized how factors such as MP size, polymer type, extraction methods, and soil matrix affect the recovery of microplastic particles. We used both hydrophobic and density-dependent separation methods to assess the effects of our oxidation treatment on the recovery of MP. We observed that NaOCl effectively removed SOM without greatly altering the surface properties of resistant MP polymers (polypropylene, polylactic acid, low-density polyethylene, and polyethylene terephthalate), which were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy after SOM removal. The NaOCl treatment caused some chlorination and formation of additional C?OH bonds on polymer surfaces, which likely contributed to the reduced efficiency of the hydrophobic-based (oil) extraction. We conclude that NaOCl treatment can improve detection of MPs in SOM-rich soil and that recovery of MPs from soils is influenced by MP size, polymer type, extraction method, and soil type, which makes it challenging to develop a universal analytical method.},
	number = {1},
	urldate = {2023-07-22},
	journal = {Journal of Environmental Quality},
	author = {Bottone, Anna and Boily, Jean-Francois and Shchukarev, Andrey and Andersson, Patrik L. and Klaminder, Jonatan},
	month = jan,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	pages = {112--122},
}

Abstract The omnipresence of microplastics (MPs) across Earth's surface has raised concerns about their environmental impact and created an urgent need for methods to identify them in complex soil and sedimentary matrices. However, detecting MPs in the O horizons of soils is difficult because plastic polymers share many physical and chemical properties with natural soil organic matter (SOM). In this study, we assessed whether sodium hypochlorite (NaOCl), a reagent that can oxidize SOM and simultaneously preserve mineral constituents, can be used for MP analysis and characterization in soil environments. In addition, we scrutinized how factors such as MP size, polymer type, extraction methods, and soil matrix affect the recovery of microplastic particles. We used both hydrophobic and density-dependent separation methods to assess the effects of our oxidation treatment on the recovery of MP. We observed that NaOCl effectively removed SOM without greatly altering the surface properties of resistant MP polymers (polypropylene, polylactic acid, low-density polyethylene, and polyethylene terephthalate), which were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy after SOM removal. The NaOCl treatment caused some chlorination and formation of additional C?OH bonds on polymer surfaces, which likely contributed to the reduced efficiency of the hydrophobic-based (oil) extraction. We conclude that NaOCl treatment can improve detection of MPs in SOM-rich soil and that recovery of MPs from soils is influenced by MP size, polymer type, extraction method, and soil type, which makes it challenging to develop a universal analytical method.

@article{lembrechts_global_2022,
	title = {Global maps of soil temperature},
	volume = {28},
	issn = {1354-1013},
	url = {https://doi.org/10.1111/gcb.16060},
	doi = {10.1111/gcb.16060},
	abstract = {Abstract Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0?5 and 5?15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (?0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.},
	number = {9},
	urldate = {2023-07-21},
	journal = {Global Change Biology},
	author = {Lembrechts, Jonas J. and van den Hoogen, Johan and Aalto, Juha and Ashcroft, Michael B. and De Frenne, Pieter and Kemppinen, Julia and Kopecký, Martin and Luoto, Miska and Maclean, Ilya M. D. and Crowther, Thomas W. and Bailey, Joseph J. and Haesen, Stef and Klinges, David H. and Niittynen, Pekka and Scheffers, Brett R. and Van Meerbeek, Koenraad and Aartsma, Peter and Abdalaze, Otar and Abedi, Mehdi and Aerts, Rien and Ahmadian, Negar and Ahrends, Antje and Alatalo, Juha M. and Alexander, Jake M. and Allonsius, Camille Nina and Altman, Jan and Ammann, Christof and Andres, Christian and Andrews, Christopher and Ardö, Jonas and Arriga, Nicola and Arzac, Alberto and Aschero, Valeria and Assis, Rafael L. and Assmann, Jakob Johann and Bader, Maaike Y. and Bahalkeh, Khadijeh and Barančok, Peter and Barrio, Isabel C. and Barros, Agustina and Barthel, Matti and Basham, Edmund W. and Bauters, Marijn and Bazzichetto, Manuele and Marchesini, Luca Belelli and Bell, Michael C. and Benavides, Juan C. and Benito Alonso, José Luis and Berauer, Bernd J. and Bjerke, Jarle W. and Björk, Robert G. and Björkman, Mats P. and Björnsdóttir, Katrin and Blonder, Benjamin and Boeckx, Pascal and Boike, Julia and Bokhorst, Stef and Brum, Bárbara N. S. and Brůna, Josef and Buchmann, Nina and Buysse, Pauline and Camargo, José Luís and Campoe, Otávio C. and Candan, Onur and Canessa, Rafaella and Cannone, Nicoletta and Carbognani, Michele and Carnicer, Jofre and Casanova-Katny, Angélica and Cesarz, Simone and Chojnicki, Bogdan and Choler, Philippe and Chown, Steven L. and Cifuentes, Edgar F. and Čiliak, Marek and Contador, Tamara and Convey, Peter and Cooper, Elisabeth J. and Cremonese, Edoardo and Curasi, Salvatore R. and Curtis, Robin and Cutini, Maurizio and Dahlberg, C. Johan and Daskalova, Gergana N. and de Pablo, Miguel Angel and Della Chiesa, Stefano and Dengler, Jürgen and Deronde, Bart and Descombes, Patrice and Di Cecco, Valter and Di Musciano, Michele and Dick, Jan and Dimarco, Romina D. and Dolezal, Jiri and Dorrepaal, Ellen and Dušek, Jiří and Eisenhauer, Nico and Eklundh, Lars and Erickson, Todd E. and Erschbamer, Brigitta and Eugster, Werner and Ewers, Robert M. and Exton, Dan A. and Fanin, Nicolas and Fazlioglu, Fatih and Feigenwinter, Iris and Fenu, Giuseppe and Ferlian, Olga and Fernández Calzado, M. Rosa and Fernández-Pascual, Eduardo and Finckh, Manfred and Higgens, Rebecca Finger and Forte, T'ai G. W. and Freeman, Erika C. and Frei, Esther R. and Fuentes-Lillo, Eduardo and García, Rafael A. and García, María B. and Géron, Charly and Gharun, Mana and Ghosn, Dany and Gigauri, Khatuna and Gobin, Anne and Goded, Ignacio and Goeckede, Mathias and Gottschall, Felix and Goulding, Keith and Govaert, Sanne and Graae, Bente Jessen and Greenwood, Sarah and Greiser, Caroline and Grelle, Achim and Guénard, Benoit and Guglielmin, Mauro and Guillemot, Joannès and Haase, Peter and Haider, Sylvia and Halbritter, Aud H. and Hamid, Maroof and Hammerle, Albin and Hampe, Arndt and Haugum, Siri V. and Hederová, Lucia and Heinesch, Bernard and Helfter, Carole and Hepenstrick, Daniel and Herberich, Maximiliane and Herbst, Mathias and Hermanutz, Luise and Hik, David S. and Hoffrén, Raúl and Homeier, Jürgen and Hörtnagl, Lukas and Høye, Toke T. and Hrbacek, Filip and Hylander, Kristoffer and Iwata, Hiroki and Jackowicz-Korczynski, Marcin Antoni and Jactel, Hervé and Järveoja, Järvi and Jastrzębowski, Szymon and Jentsch, Anke and Jiménez, Juan J. and Jónsdóttir, Ingibjörg S. and Jucker, Tommaso and Jump, Alistair S. and Juszczak, Radoslaw and Kanka, Róbert and Kašpar, Vít and Kazakis, George and Kelly, Julia and Khuroo, Anzar A. and Klemedtsson, Leif and Klisz, Marcin and Kljun, Natascha and Knohl, Alexander and Kobler, Johannes and Kollár, Jozef and Kotowska, Martyna M. and Kovács, Bence and Kreyling, Juergen and Lamprecht, Andrea and Lang, Simone I. and Larson, Christian and Larson, Keith and Laska, Kamil and le Maire, Guerric and Leihy, Rachel I. and Lens, Luc and Liljebladh, Bengt and Lohila, Annalea and Lorite, Juan and Loubet, Benjamin and Lynn, Joshua and Macek, Martin and Mackenzie, Roy and Magliulo, Enzo and Maier, Regine and Malfasi, Francesco and Máliš, František and Man, Matěj and Manca, Giovanni and Manco, Antonio and Manise, Tanguy and Manolaki, Paraskevi and Marciniak, Felipe and Matula, Radim and Mazzolari, Ana Clara and Medinets, Sergiy and Medinets, Volodymyr and Meeussen, Camille and Merinero, Sonia and Mesquita, Rita de Cássia Guimarães and Meusburger, Katrin and Meysman, Filip J. R. and Michaletz, Sean T. and Milbau, Ann and Moiseev, Dmitry and Moiseev, Pavel and Mondoni, Andrea and Monfries, Ruth and Montagnani, Leonardo and Moriana-Armendariz, Mikel and Morra di Cella, Umberto and Mörsdorf, Martin and Mosedale, Jonathan R. and Muffler, Lena and Muñoz-Rojas, Miriam and Myers, Jonathan A. and Myers-Smith, Isla H. and Nagy, Laszlo and Nardino, Marianna and Naujokaitis-Lewis, Ilona and Newling, Emily and Nicklas, Lena and Niedrist, Georg and Niessner, Armin and Nilsson, Mats B. and Normand, Signe and Nosetto, Marcelo D. and Nouvellon, Yann and Nuñez, Martin A. and Ogaya, Romà and Ogée, Jérôme and Okello, Joseph and Olejnik, Janusz and Olesen, Jørgen Eivind and Opedal, Øystein H. and Orsenigo, Simone and Palaj, Andrej and Pampuch, Timo and Panov, Alexey V. and Pärtel, Meelis and Pastor, Ada and Pauchard, Aníbal and Pauli, Harald and Pavelka, Marian and Pearse, William D. and Peichl, Matthias and Pellissier, Loïc and Penczykowski, Rachel M. and Penuelas, Josep and Petit Bon, Matteo and Petraglia, Alessandro and Phartyal, Shyam S. and Phoenix, Gareth K. and Pio, Casimiro and Pitacco, Andrea and Pitteloud, Camille and Plichta, Roman and Porro, Francesco and Portillo-Estrada, Miguel and Poulenard, Jérôme and Poyatos, Rafael and Prokushkin, Anatoly S. and Puchalka, Radoslaw and Pușcaș, Mihai and Radujković, Dajana and Randall, Krystal and Ratier Backes, Amanda and Remmele, Sabine and Remmers, Wolfram and Renault, David and Risch, Anita C. and Rixen, Christian and Robinson, Sharon A. and Robroek, Bjorn J. M. and Rocha, Adrian V. and Rossi, Christian and Rossi, Graziano and Roupsard, Olivier and Rubtsov, Alexey V. and Saccone, Patrick and Sagot, Clotilde and Sallo Bravo, Jhonatan and Santos, Cinthya C. and Sarneel, Judith M. and Scharnweber, Tobias and Schmeddes, Jonas and Schmidt, Marius and Scholten, Thomas and Schuchardt, Max and Schwartz, Naomi and Scott, Tony and Seeber, Julia and Segalin de Andrade, Ana Cristina and Seipel, Tim and Semenchuk, Philipp and Senior, Rebecca A. and Serra-Diaz, Josep M. and Sewerniak, Piotr and Shekhar, Ankit and Sidenko, Nikita V. and Siebicke, Lukas and Siegwart Collier, Laura and Simpson, Elizabeth and Siqueira, David P. and Sitková, Zuzana and Six, Johan and Smiljanic, Marko and Smith, Stuart W. and Smith-Tripp, Sarah and Somers, Ben and Sørensen, Mia Vedel and Souza, José João L. L. and Souza, Bartolomeu Israel and Souza Dias, Arildo and Spasojevic, Marko J. and Speed, James D. M. and Spicher, Fabien and Stanisci, Angela and Steinbauer, Klaus and Steinbrecher, Rainer and Steinwandter, Michael and Stemkovski, Michael and Stephan, Jörg G. and Stiegler, Christian and Stoll, Stefan and Svátek, Martin and Svoboda, Miroslav and Tagesson, Torbern and Tanentzap, Andrew J. and Tanneberger, Franziska and Theurillat, Jean-Paul and Thomas, Haydn J. D. and Thomas, Andrew D. and Tielbörger, Katja and Tomaselli, Marcello and Treier, Urs Albert and Trouillier, Mario and Turtureanu, Pavel Dan and Tutton, Rosamond and Tyystjärvi, Vilna A. and Ueyama, Masahito and Ujházy, Karol and Ujházyová, Mariana and Uogintas, Domas and Urban, Anastasiya V. and Urban, Josef and Urbaniak, Marek and Ursu, Tudor-Mihai and Vaccari, Francesco Primo and Van de Vondel, Stijn and van den Brink, Liesbeth and Van Geel, Maarten and Vandvik, Vigdis and Vangansbeke, Pieter and Varlagin, Andrej and Veen, G. F. and Veenendaal, Elmar and Venn, Susanna E. and Verbeeck, Hans and Verbrugggen, Erik and Verheijen, Frank G. A. and Villar, Luis and Vitale, Luca and Vittoz, Pascal and Vives-Ingla, Maria and von Oppen, Jonathan and Walz, Josefine and Wang, Runxi and Wang, Yifeng and Way, Robert G. and Wedegärtner, Ronja E. M. and Weigel, Robert and Wild, Jan and Wilkinson, Matthew and Wilmking, Martin and Wingate, Lisa and Winkler, Manuela and Wipf, Sonja and Wohlfahrt, Georg and Xenakis, Georgios and Yang, Yan and Yu, Zicheng and Yu, Kailiang and Zellweger, Florian and Zhang, Jian and Zhang, Zhaochen and Zhao, Peng and Ziemblińska, Klaudia and Zimmermann, Reiner and Zong, Shengwei and Zyryanov, Viacheslav I. and Nijs, Ivan and Lenoir, Jonathan},
	month = may,
	year = {2022},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, bioclimatic variables, global maps, microclimate, near-surface temperatures, soil temperature, soil-dwelling organisms, temperature offset, weather stations},
	pages = {3110--3144},
}

Abstract Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0?5 and 5?15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (?0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.

@article{poppeliers_functional_2022,
	title = {Functional microbial ecology in arctic soils: the need for a year-round perspective},
	volume = {98},
	issn = {0168-6496},
	url = {https://doi.org/10.1093/femsec/fiac134},
	doi = {10.1093/femsec/fiac134},
	abstract = {The microbial ecology of arctic and sub-arctic soils is an important aspect of the global carbon cycle, due to the sensitivity of the large soil carbon stocks to ongoing climate warming. These regions are characterized by strong climatic seasonality, but the emphasis of most studies on the short vegetation growing season could potentially limit our ability to predict year-round ecosystem functions. We compiled a database of studies from arctic, subarctic, and boreal environments that include sampling of microbial community and functions outside the growing season. We found that for studies comparing across seasons, in most environments, microbial biomass and community composition vary intra-annually, with the spring thaw period often identified by researchers as the most dynamic time of year. This seasonality of microbial communities will have consequences for predictions of ecosystem function under climate change if it results in: seasonality in process kinetics of microbe-mediated functions; intra-annual variation in the importance of different (a)biotic drivers; and/or potential temporal asynchrony between climate change-related perturbations and their corresponding effects. Future research should focus on (i) sampling throughout the entire year; (ii) linking these multi-season measures of microbial community composition with corresponding functional or physiological measurements to elucidate the temporal dynamics of the links between them; and (iii) identifying dominant biotic and abiotic drivers of intra-annual variation in different ecological contexts.},
	number = {12},
	urldate = {2023-07-21},
	journal = {FEMS Microbiology Ecology},
	author = {Poppeliers, Sanne W M and Hefting, Mariet and Dorrepaal, Ellen and Weedon, James T},
	month = dec,
	year = {2022},
	keywords = {\#nosource, *Microbiota, *Soil, Arctic Regions, Carbon Cycle, Climate Change, bacteria, fluxes, fungi, seasonality, soil},
	pages = {fiac134},
}

The microbial ecology of arctic and sub-arctic soils is an important aspect of the global carbon cycle, due to the sensitivity of the large soil carbon stocks to ongoing climate warming. These regions are characterized by strong climatic seasonality, but the emphasis of most studies on the short vegetation growing season could potentially limit our ability to predict year-round ecosystem functions. We compiled a database of studies from arctic, subarctic, and boreal environments that include sampling of microbial community and functions outside the growing season. We found that for studies comparing across seasons, in most environments, microbial biomass and community composition vary intra-annually, with the spring thaw period often identified by researchers as the most dynamic time of year. This seasonality of microbial communities will have consequences for predictions of ecosystem function under climate change if it results in: seasonality in process kinetics of microbe-mediated functions; intra-annual variation in the importance of different (a)biotic drivers; and/or potential temporal asynchrony between climate change-related perturbations and their corresponding effects. Future research should focus on (i) sampling throughout the entire year; (ii) linking these multi-season measures of microbial community composition with corresponding functional or physiological measurements to elucidate the temporal dynamics of the links between them; and (iii) identifying dominant biotic and abiotic drivers of intra-annual variation in different ecological contexts.

@phdthesis{verheijen_factors_2022,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Factors regulating the origin and magnitude of carbon dioxide emissions from high-latitude lakes},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-198962},
	abstract = {Lake ecosystems receive, transmit and process terrestrial carbon and thereby link terrestrial, aquatic and global carbon cycles. Most lakes evade CO2 to the atmosphere, but the annual magnitude of  ...},
	language = {eng},
	urldate = {2023-07-21},
	school = {Umeå University},
	author = {Verheijen, Hendricus},
	collaborator = {Karlsson, Jan and Gudasz, Cristian and Seekell, David A. and Klaus, Marcus},
	year = {2022},
	note = {Publisher: Umeå University},
	keywords = {\#nosource, ⛔ No DOI found},
}

Lake ecosystems receive, transmit and process terrestrial carbon and thereby link terrestrial, aquatic and global carbon cycles. Most lakes evade CO2 to the atmosphere, but the annual magnitude of ...

@article{terhaar_observation-constrained_2022,
	title = {Observation-constrained estimates of the global ocean carbon sink from {Earth} system models},
	volume = {19},
	url = {https://bg.copernicus.org/articles/19/4431/2022/},
	doi = {10.5194/bg-19-4431-2022},
	number = {18},
	journal = {Biogeosciences},
	author = {Terhaar, J. and Frölicher, T. L. and Joos, F.},
	year = {2022},
	keywords = {\#nosource},
	pages = {4431--4457},
}

@article{spath_effects_2022,
	title = {Effects of conventionally treated and ozonated wastewater on the damselfly larva oxylipidome in response to on-site exposure},
	volume = {309},
	issn = {0045-6535},
	url = {https://www.sciencedirect.com/science/article/pii/S0045653522030971},
	doi = {10.1016/j.chemosphere.2022.136604},
	abstract = {Pharmaceutical residues discharged through insufficiently treated or untreated wastewater enter aquatic environments, where they may adversely impact organisms such as aquatic invertebrates. Ozonation, an advanced wastewater treatment technique, has been successfully implemented to enhance the removal of a broad range of pharmaceuticals, however diverse byproducts and transformation products that are formed during the ozonation process make it difficult to predict how ozonated wastewater may affect aquatic biota. The aim of this study was to investigate effects on fatty acid metabolites, oxylipins, in a common invertebrate species, damselfly larvae, after on-site exposure to conventional wastewater treatment plant (WWTP) effluent and additionally ozonated effluent at a full-scale WWTP. Subsequent ozonation of the conventionally treated wastewater was assessed in terms of i) removal of pharmaceuticals and ii) potential sub-lethal effects on the oxylipidome. Northern damselfly (Coenagrion hastulatum) larvae were exposed for six days in the treatment plant facility to either conventional WWTP effluent or ozonated effluent and the effects on pharmaceutical levels and oxylipin levels were compared with those from tap water control exposure. Ozonation removed pharmaceuticals at an average removal efficiency of 67\% (ozone dose of 0.49 g O3/g DOC). Of 38 pharmaceuticals detected in the effluent, 16 were removed to levels below the limit of quantification by ozonation. Levels of two oxylipins, 12(13)-EpODE and 15(16)-EpODE, were reduced in larvae exposed to the conventionally treated wastewater in comparison to the tap water control. 15(16)-EpODE was reduced in the larvae exposed to ozonated effluent in comparison to the tap water control. One oxylipin, 8-HETE, was significantly lower in larvae exposed to conventional WWTP effluent compared to ozonated effluent. In conclusion, the study provides proof-of-principle that damselfly larvae can be used on-site to test the impact of differentially treated wastewater.},
	journal = {Chemosphere},
	author = {Späth, Jana and Brodin, Tomas and Falås, Per and Niinipuu, Mirva and Lindberg, Richard and Fick, Jerker and Nording, Malin},
	month = dec,
	year = {2022},
	keywords = {\#nosource, Benthic invertebrate, Liquid chromatography tandem mass spectrometry, Metabolomics, Oxylipin, Ozonation, Sewage, Wastewater treatment plant},
	pages = {136604},
}

Pharmaceutical residues discharged through insufficiently treated or untreated wastewater enter aquatic environments, where they may adversely impact organisms such as aquatic invertebrates. Ozonation, an advanced wastewater treatment technique, has been successfully implemented to enhance the removal of a broad range of pharmaceuticals, however diverse byproducts and transformation products that are formed during the ozonation process make it difficult to predict how ozonated wastewater may affect aquatic biota. The aim of this study was to investigate effects on fatty acid metabolites, oxylipins, in a common invertebrate species, damselfly larvae, after on-site exposure to conventional wastewater treatment plant (WWTP) effluent and additionally ozonated effluent at a full-scale WWTP. Subsequent ozonation of the conventionally treated wastewater was assessed in terms of i) removal of pharmaceuticals and ii) potential sub-lethal effects on the oxylipidome. Northern damselfly (Coenagrion hastulatum) larvae were exposed for six days in the treatment plant facility to either conventional WWTP effluent or ozonated effluent and the effects on pharmaceutical levels and oxylipin levels were compared with those from tap water control exposure. Ozonation removed pharmaceuticals at an average removal efficiency of 67% (ozone dose of 0.49 g O3/g DOC). Of 38 pharmaceuticals detected in the effluent, 16 were removed to levels below the limit of quantification by ozonation. Levels of two oxylipins, 12(13)-EpODE and 15(16)-EpODE, were reduced in larvae exposed to the conventionally treated wastewater in comparison to the tap water control. 15(16)-EpODE was reduced in the larvae exposed to ozonated effluent in comparison to the tap water control. One oxylipin, 8-HETE, was significantly lower in larvae exposed to conventional WWTP effluent compared to ozonated effluent. In conclusion, the study provides proof-of-principle that damselfly larvae can be used on-site to test the impact of differentially treated wastewater.

@phdthesis{puts_impacts_2022,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Impacts of global change on primary production in northern lakes},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-194523},
	abstract = {Algae are primary producers, a major component of the aquatic foodweb, and changes in primary production affect aquatic ecology in general. Global changes such as warming, recovery of acidification ...},
	language = {eng},
	urldate = {2023-07-21},
	school = {Umeå University},
	author = {Puts, Isolde Callisto},
	collaborator = {Bergström, Ann-Kristin and Ask, Jenny},
	year = {2022},
	note = {Publisher: Umeå University},
	keywords = {\#nosource, ⛔ No DOI found},
}

Algae are primary producers, a major component of the aquatic foodweb, and changes in primary production affect aquatic ecology in general. Global changes such as warming, recovery of acidification ...

@article{oehri_vegetation_2022,
	title = {Vegetation type is an important predictor of the arctic summer land surface energy budget},
	volume = {13},
	issn = {2041-1723},
	url = {https://doi.org/10.1038/s41467-022-34049-3},
	doi = {10.1038/s41467-022-34049-3},
	abstract = {Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994–2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm−2) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.},
	number = {1},
	journal = {Nature Communications},
	author = {Oehri, Jacqueline and Schaepman-Strub, Gabriela and Kim, Jin-Soo and Grysko, Raleigh and Kropp, Heather and Grünberg, Inge and Zemlianskii, Vitalii and Sonnentag, Oliver and Euskirchen, Eugénie S. and Reji Chacko, Merin and Muscari, Giovanni and Blanken, Peter D. and Dean, Joshua F. and di Sarra, Alcide and Harding, Richard J. and Sobota, Ireneusz and Kutzbach, Lars and Plekhanova, Elena and Riihelä, Aku and Boike, Julia and Miller, Nathaniel B. and Beringer, Jason and López-Blanco, Efrén and Stoy, Paul C. and Sullivan, Ryan C. and Kejna, Marek and Parmentier, Frans-Jan W. and Gamon, John A. and Mastepanov, Mikhail and Wille, Christian and Jackowicz-Korczynski, Marcin and Karger, Dirk N. and Quinton, William L. and Putkonen, Jaakko and van As, Dirk and Christensen, Torben R. and Hakuba, Maria Z. and Stone, Robert S. and Metzger, Stefan and Vandecrux, Baptiste and Frost, Gerald V. and Wild, Martin and Hansen, Birger and Meloni, Daniela and Domine, Florent and te Beest, Mariska and Sachs, Torsten and Kalhori, Aram and Rocha, Adrian V. and Williamson, Scott N. and Morris, Sara and Atchley, Adam L. and Essery, Richard and Runkle, Benjamin R. K. and Holl, David and Riihimaki, Laura D. and Iwata, Hiroki and Schuur, Edward A. G. and Cox, Christopher J. and Grachev, Andrey A. and McFadden, Joseph P. and Fausto, Robert S. and Göckede, Mathias and Ueyama, Masahito and Pirk, Norbert and de Boer, Gijs and Bret-Harte, M. Syndonia and Leppäranta, Matti and Steffen, Konrad and Friborg, Thomas and Ohmura, Atsumu and Edgar, Colin W. and Olofsson, Johan and Chambers, Scott D.},
	month = oct,
	year = {2022},
	keywords = {\#nosource},
	pages = {6379},
}

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994–2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm−2) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.

@article{linden_circum-arctic_2022,
	title = {Circum-{Arctic} distribution of chemical anti-herbivore compounds suggests biome-wide trade-off in defence strategies in {Arctic} shrubs},
	volume = {2022},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ecog.06166},
	doi = {10.1111/ecog.06166},
	abstract = {Spatial variation in plant chemical defence towards herbivores can help us understand variation in herbivore top–down control of shrubs in the Arctic and possibly also shrub responses to global warming. Less defended, non-resinous shrubs could be more influenced by herbivores than more defended, resinous shrubs. However, sparse field measurements limit our current understanding of how much of the circum-Arctic variation in defence compounds is explained by taxa or defence functional groups (resinous/non-resinous). We measured circum-Arctic chemical defence and leaf digestibility in resinous (Betula glandulosa, B. nana ssp. exilis) and non-resinous (B. nana ssp. nana, B. pumila) shrub birches to see how they vary among and within taxa and functional groups. Using liquid chromatography–mass spectrometry (LC–MS) metabolomic analyses and in vitro leaf digestibility via incubation in cattle rumen fluid, we analysed defence composition and leaf digestibility in 128 samples from 44 tundra locations. We found biogeographical patterns in anti-herbivore defence where mean leaf triterpene concentrations and twig resin gland density were greater in resinous taxa and mean concentrations of condensing tannins were greater in non-resinous taxa. This indicates a biome-wide trade-off between triterpene- or tannin-dominated defences. However, we also found variations in chemical defence composition and resin gland density both within and among functional groups (resinous/non-resinous) and taxa, suggesting these categorisations only partly predict chemical herbivore defence. Complex tannins were the only defence compounds negatively related to in vitro digestibility, identifying this previously neglected tannin group as having a potential key role in birch anti-herbivore defence. We conclude that circum-Arctic variation in birch anti-herbivore defence can be partly derived from biogeographical distributions of birch taxa, although our detailed mapping of plant defence provides more information on this variation and can be used for better predictions of herbivore effects on Arctic vegetation.},
	number = {11},
	journal = {Ecography},
	author = {Lindén, Elin and te Beest, Mariska and Abreu, Ilka N. and Moritz, Thomas and Sundqvist, Maja K. and Barrio, Isabel C. and Boike, Julia and Bryant, John P. and Bråthen, Kari Anne and Buchwal, Agata and Bueno, C. Guillermo and Cuerrier, Alain and Egelkraut, Dagmar D. and Forbes, Bruce C. and Hallinger, Martin and Heijmans, Monique and Hermanutz, Luise and Hik, David S. and Hofgaard, Annika and Holmgren, Milena and Huebner, Diane C. and Høye, Toke T. and Jónsdóttir, Ingibjörg S. and Kaarlejärvi, Elina and Kissler, Emilie and Kumpula, Timo and Limpens, Juul and Myers-Smith, Isla H. and Normand, Signe and Post, Eric and Rocha, Adrian V. and Schmidt, Niels Martin and Skarin, Anna and Soininen, Eeva M. and Sokolov, Aleksandr and Sokolova, Natalia and Speed, James D. M. and Street, Lorna and Tananaev, Nikita and Tremblay, Jean-Pierre and Urbanowicz, Christine and Watts, David A. and Zimmermann, Heike and Olofsson, Johan},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/ecog.06166},
	keywords = {\#nosource, Arctic, Betula, birch, herbivory, metabolomics, plant chemical defence, shrubs, tundra},
	pages = {e06166},
}

Spatial variation in plant chemical defence towards herbivores can help us understand variation in herbivore top–down control of shrubs in the Arctic and possibly also shrub responses to global warming. Less defended, non-resinous shrubs could be more influenced by herbivores than more defended, resinous shrubs. However, sparse field measurements limit our current understanding of how much of the circum-Arctic variation in defence compounds is explained by taxa or defence functional groups (resinous/non-resinous). We measured circum-Arctic chemical defence and leaf digestibility in resinous (Betula glandulosa, B. nana ssp. exilis) and non-resinous (B. nana ssp. nana, B. pumila) shrub birches to see how they vary among and within taxa and functional groups. Using liquid chromatography–mass spectrometry (LC–MS) metabolomic analyses and in vitro leaf digestibility via incubation in cattle rumen fluid, we analysed defence composition and leaf digestibility in 128 samples from 44 tundra locations. We found biogeographical patterns in anti-herbivore defence where mean leaf triterpene concentrations and twig resin gland density were greater in resinous taxa and mean concentrations of condensing tannins were greater in non-resinous taxa. This indicates a biome-wide trade-off between triterpene- or tannin-dominated defences. However, we also found variations in chemical defence composition and resin gland density both within and among functional groups (resinous/non-resinous) and taxa, suggesting these categorisations only partly predict chemical herbivore defence. Complex tannins were the only defence compounds negatively related to in vitro digestibility, identifying this previously neglected tannin group as having a potential key role in birch anti-herbivore defence. We conclude that circum-Arctic variation in birch anti-herbivore defence can be partly derived from biogeographical distributions of birch taxa, although our detailed mapping of plant defence provides more information on this variation and can be used for better predictions of herbivore effects on Arctic vegetation.

@article{krab_experimentally_2022,
	title = {Experimentally increased snow depth affects high {Arctic} microarthropods inconsistently over two consecutive winters},
	volume = {12},
	issn = {2045-2322},
	url = {https://doi.org/10.1038/s41598-022-22591-5},
	doi = {10.1038/s41598-022-22591-5},
	abstract = {Climate change induced alterations to winter conditions may affect decomposer organisms controlling the vast carbon stores in northern soils. Soil microarthropods are particularly abundant decomposers in Arctic ecosystems. We studied whether increased snow depth affected microarthropods, and if effects were consistent over two consecutive winters. We sampled Collembola and soil mites from a snow accumulation experiment at Svalbard in early summer and used soil microclimatic data to explore to which aspects of winter climate microarthropods are most sensitive. Community densities differed substantially between years and increased snow depth had inconsistent effects. Deeper snow hardly affected microarthropods in 2015, but decreased densities and altered relative abundances of microarthropods and Collembola species after a milder winter in 2016. Although increased snow depth increased soil temperatures by 3.2 °C throughout the snow cover periods, the best microclimatic predictors of microarthropod density changes were spring soil temperature and snowmelt day. Our study shows that extrapolation of observations of decomposer responses to altered winter climate conditions to future scenarios should be avoided when communities are only sampled on a single occasion, since effects of longer-term gradual changes in winter climate may be obscured by inter-annual weather variability and natural variability in population sizes.},
	number = {1},
	journal = {Scientific Reports},
	author = {Krab, Eveline J. and Lundin, Erik J. and Coulson, Stephen J. and Dorrepaal, Ellen and Cooper, Elisabeth J.},
	month = oct,
	year = {2022},
	keywords = {\#nosource},
	pages = {18049},
}

Climate change induced alterations to winter conditions may affect decomposer organisms controlling the vast carbon stores in northern soils. Soil microarthropods are particularly abundant decomposers in Arctic ecosystems. We studied whether increased snow depth affected microarthropods, and if effects were consistent over two consecutive winters. We sampled Collembola and soil mites from a snow accumulation experiment at Svalbard in early summer and used soil microclimatic data to explore to which aspects of winter climate microarthropods are most sensitive. Community densities differed substantially between years and increased snow depth had inconsistent effects. Deeper snow hardly affected microarthropods in 2015, but decreased densities and altered relative abundances of microarthropods and Collembola species after a milder winter in 2016. Although increased snow depth increased soil temperatures by 3.2 °C throughout the snow cover periods, the best microclimatic predictors of microarthropod density changes were spring soil temperature and snowmelt day. Our study shows that extrapolation of observations of decomposer responses to altered winter climate conditions to future scenarios should be avoided when communities are only sampled on a single occasion, since effects of longer-term gradual changes in winter climate may be obscured by inter-annual weather variability and natural variability in population sizes.

@article{olid_groundwater_2022,
	title = {Groundwater discharge as a driver of methane emissions from {Arctic} lakes},
	volume = {13},
	copyright = {2022 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-022-31219-1},
	doi = {10.1038/s41467-022-31219-1},
	abstract = {Lateral CH4 inputs to Arctic lakes through groundwater discharge could be substantial and constitute an important pathway that links CH4 production in thawing permafrost to atmospheric emissions via lakes. Yet, groundwater CH4 inputs and associated drivers are hitherto poorly constrained because their dynamics and spatial variability are largely unknown. Here, we unravel the important role and drivers of groundwater discharge for CH4 emissions from Arctic lakes. Spatial patterns across lakes suggest groundwater inflows are primarily related to lake depth and wetland cover. Groundwater CH4 inputs to lakes are higher in summer than in autumn and are influenced by hydrological (groundwater recharge) and biological drivers (CH4 production). This information on the spatial and temporal patterns on groundwater discharge at high northern latitudes is critical for predicting lake CH4 emissions in the warming Arctic, as rising temperatures, increasing precipitation, and permafrost thawing may further exacerbate groundwater CH4 inputs to lakes.},
	language = {en},
	number = {1},
	urldate = {2023-07-20},
	journal = {Nature Communications},
	author = {Olid, Carolina and Rodellas, Valentí and Rocher-Ros, Gerard and Garcia-Orellana, Jordi and Diego-Feliu, Marc and Alorda-Kleinglass, Aaron and Bastviken, David and Karlsson, Jan},
	month = jun,
	year = {2022},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource, Carbon cycle, Climate-change impacts},
	pages = {3667},
}

Lateral CH4 inputs to Arctic lakes through groundwater discharge could be substantial and constitute an important pathway that links CH4 production in thawing permafrost to atmospheric emissions via lakes. Yet, groundwater CH4 inputs and associated drivers are hitherto poorly constrained because their dynamics and spatial variability are largely unknown. Here, we unravel the important role and drivers of groundwater discharge for CH4 emissions from Arctic lakes. Spatial patterns across lakes suggest groundwater inflows are primarily related to lake depth and wetland cover. Groundwater CH4 inputs to lakes are higher in summer than in autumn and are influenced by hydrological (groundwater recharge) and biological drivers (CH4 production). This information on the spatial and temporal patterns on groundwater discharge at high northern latitudes is critical for predicting lake CH4 emissions in the warming Arctic, as rising temperatures, increasing precipitation, and permafrost thawing may further exacerbate groundwater CH4 inputs to lakes.

@article{hamdan_carbon_2022,
	title = {Carbon dioxide limitation of benthic primary production in a boreal lake},
	volume = {67},
	copyright = {© 2022 The Authors. Freshwater Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2427},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.13972},
	doi = {10.1111/fwb.13972},
	abstract = {Gross primary production (GPP) by benthic microalgae growing on soft sediments is an important contributor to lake productivity in many lakes world-wide. As benthic microalgae have access to nutrients in the sediment they have been regarded as primarily controlled by light, while the role of CO2 as a limiting factor for benthic GPP in lake ecosystems is largely unknown. In this study, we experimentally tested for CO2 limitation of benthic GPP by collecting littoral surface sediments, with associated benthic microalgae, from a typical boreal lake. Intact sediment cores were incubated at different depths (light conditions) after addition of dissolved inorganic (bicarbonate) or organic (DOC; glucose) carbon as direct and indirect sources of CO2, respectively. Benthic microalgal GPP was stimulated by both dissolved inorganic carbon and DOC additions at high, but not at low, light levels. This study shows that benthic microalgal GPP can be CO2-limited when light is not limiting and suggests that both direct (e.g., via groundwater inflow) and indirect (via mineralisation of DOC) CO2 supply can stimulate benthic GPP.},
	language = {en},
	number = {10},
	urldate = {2023-07-20},
	journal = {Freshwater Biology},
	author = {Hamdan, Mohammed and Karlsson, Jan and Byström, Pär and Al-Haidarey, Mohammed J. and Ask, Jenny},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.13972},
	keywords = {\#nosource, CO2 limitation, benthic microalgal gross primary production, dissolved organic carbon, lakes, light limitation},
	pages = {1752--1760},
}

Gross primary production (GPP) by benthic microalgae growing on soft sediments is an important contributor to lake productivity in many lakes world-wide. As benthic microalgae have access to nutrients in the sediment they have been regarded as primarily controlled by light, while the role of CO2 as a limiting factor for benthic GPP in lake ecosystems is largely unknown. In this study, we experimentally tested for CO2 limitation of benthic GPP by collecting littoral surface sediments, with associated benthic microalgae, from a typical boreal lake. Intact sediment cores were incubated at different depths (light conditions) after addition of dissolved inorganic (bicarbonate) or organic (DOC; glucose) carbon as direct and indirect sources of CO2, respectively. Benthic microalgal GPP was stimulated by both dissolved inorganic carbon and DOC additions at high, but not at low, light levels. This study shows that benthic microalgal GPP can be CO2-limited when light is not limiting and suggests that both direct (e.g., via groundwater inflow) and indirect (via mineralisation of DOC) CO2 supply can stimulate benthic GPP.

@article{verheijen_magnitude_2022,
	title = {Magnitude and {Origin} of {CO2} {Evasion} {From} {High}-{Latitude} {Lakes}},
	volume = {127},
	copyright = {© 2022 The Authors.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021JG006768},
	doi = {10.1029/2021JG006768},
	abstract = {Lakes evade significant amounts of carbon dioxide (CO2) to the atmosphere; yet the magnitude and origin of the evasion are still poorly constrained. We quantified annual CO2 evasion and its origin (in-lake net ecosystem production vs. lateral inputs from terrestrial ecosystems) in 14 high-latitude lakes through high-frequency estimates of open water CO2 flux and ecosystem metabolism and inorganic carbon mass-balance before and after ice breakup. Annual CO2 evasion ranged from 1 to 25 g C m−2 yr−1 of which an average of 57\% was evaded over a short period at ice-breakup. Annual internal CO2 production ranged from −6 to 21 g C m−2 yr−1, of which at least half was produced over winter. The contribution of internal versus external source contribution to annual CO2 evasion varied between lakes, ranging from fully internal to fully external with most lakes having over 75\% of the evasion sustained through a single source. Overall, the study stresses the large variability in magnitude and control of CO2 evasion and suggests that environmental change impacts on CO2 evasion from high-latitude lakes are not uniform.},
	language = {en},
	number = {6},
	urldate = {2023-07-20},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Verheijen, H. A. and Klaus, M. and Seekell, D. A. and Karlsson, J.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021JG006768},
	keywords = {\#nosource, carbon cycling, carbon dioxide flux, high-latitude, lakes, net ecosystem production, subarctic},
	pages = {e2021JG006768},
}

Lakes evade significant amounts of carbon dioxide (CO2) to the atmosphere; yet the magnitude and origin of the evasion are still poorly constrained. We quantified annual CO2 evasion and its origin (in-lake net ecosystem production vs. lateral inputs from terrestrial ecosystems) in 14 high-latitude lakes through high-frequency estimates of open water CO2 flux and ecosystem metabolism and inorganic carbon mass-balance before and after ice breakup. Annual CO2 evasion ranged from 1 to 25 g C m−2 yr−1 of which an average of 57% was evaded over a short period at ice-breakup. Annual internal CO2 production ranged from −6 to 21 g C m−2 yr−1, of which at least half was produced over winter. The contribution of internal versus external source contribution to annual CO2 evasion varied between lakes, ranging from fully internal to fully external with most lakes having over 75% of the evasion sustained through a single source. Overall, the study stresses the large variability in magnitude and control of CO2 evasion and suggests that environmental change impacts on CO2 evasion from high-latitude lakes are not uniform.

@article{klaus_depth_2022,
	title = {Depth and basin shape constrain ecosystem metabolism in lakes dominated by benthic primary producers},
	volume = {67},
	copyright = {© 2022 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.12236},
	doi = {10.1002/lno.12236},
	abstract = {Metabolism is one of the most fundamental ecosystem processes, but the drivers of variation in metabolic rates among lakes dominated by benthic primary producers remain poorly constrained. Here, we report the magnitudes and potential drivers of whole-lake metabolism across 43 Swedish arctic–alpine lakes, based on the free-water diel oxygen technique with sondes deployed during the open-water season near the surface and bottom of the lakes. Gross primary production (GPP) and ecosystem respiration (R) were strongly coupled and ranged from 0.06 to 0.45 mg and 0.05 to 0.43 mg L−1 d−1 among lakes. On average, GPP and R decreased eightfold from relatively shallow to deep lakes (mean depth 0.5–10.9 m) and twofold from concave to convex lakes (mean depth: maximum depth 0.2–0.5). We attribute this to light limitation and shape-specific sensitivity of benthic GPP to disturbance by lake ice. Net ecosystem production (GPP-R) ranged from −0.09 to 0.14 mg L−1 d−1 and switched, on average, from positive to negative towards deeper lakes and lakes richer in dissolved organic carbon (DOC; 0.5–7.4 mg DOC L−1). Uncertainties in metabolism estimates were high (around one and three times mean R and GPP), especially in deep lakes with low insulation and diurnally variable wind speed. Our results confirm the role of DOC in stimulating net heterotrophy and highlight novel effects of lake shape on productivity in benthic-dominated lake ecosystems and its response to changes in lake ice cover.},
	language = {en},
	number = {12},
	urldate = {2023-07-20},
	journal = {Limnology and Oceanography},
	author = {Klaus, Marcus and Verheijen, Hendricus A. and Karlsson, Jan and Seekell, David A.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.12236},
	keywords = {\#nosource},
	pages = {2763--2778},
}

Metabolism is one of the most fundamental ecosystem processes, but the drivers of variation in metabolic rates among lakes dominated by benthic primary producers remain poorly constrained. Here, we report the magnitudes and potential drivers of whole-lake metabolism across 43 Swedish arctic–alpine lakes, based on the free-water diel oxygen technique with sondes deployed during the open-water season near the surface and bottom of the lakes. Gross primary production (GPP) and ecosystem respiration (R) were strongly coupled and ranged from 0.06 to 0.45 mg and 0.05 to 0.43 mg L−1 d−1 among lakes. On average, GPP and R decreased eightfold from relatively shallow to deep lakes (mean depth 0.5–10.9 m) and twofold from concave to convex lakes (mean depth: maximum depth 0.2–0.5). We attribute this to light limitation and shape-specific sensitivity of benthic GPP to disturbance by lake ice. Net ecosystem production (GPP-R) ranged from −0.09 to 0.14 mg L−1 d−1 and switched, on average, from positive to negative towards deeper lakes and lakes richer in dissolved organic carbon (DOC; 0.5–7.4 mg DOC L−1). Uncertainties in metabolism estimates were high (around one and three times mean R and GPP), especially in deep lakes with low insulation and diurnally variable wind speed. Our results confirm the role of DOC in stimulating net heterotrophy and highlight novel effects of lake shape on productivity in benthic-dominated lake ecosystems and its response to changes in lake ice cover.

@article{de_la_barreda-bautista_towards_2022,
	title = {Towards a {Monitoring} {Approach} for {Understanding} {Permafrost} {Degradation} and {Linked} {Subsidence} in {Arctic} {Peatlands}},
	volume = {14},
	copyright = {http://creativecommons.org/licenses/by/3.0/},
	url = {https://www.mdpi.com/2072-4292/14/3/444},
	doi = {10.3390/rs14030444},
	abstract = {Permafrost thaw resulting from climate warming is threatening to release carbon from high latitude peatlands. The aim of this research was to determine subsidence rates linked to permafrost thaw in sub-Arctic peatlands in Sweden using historical orthophotographic (orthophotos), Unoccupied Aerial Vehicle (UAV), and Interferometric Synthetic Aperture Radar (InSAR) data. The orthophotos showed that the permafrost palsa on the study sites have been contracting in their areal extent, with the greatest rates of loss between 2002 and 2008. The surface motion estimated from differential digital elevation models from the UAV data showed high levels of subsidence (maximum of \−25 cm between 2017 and 2020) around the edges of the raised palsa plateaus. The InSAR data analysis showed that raised palsa areas had the greatest subsidence rates, with maximum subsidence rates of 1.5 cm between 2017 and 2020; however, all wetland vegetation types showed subsidence. We suggest that the difference in spatial units associated with each sensor explains parts of the variation in the subsidence levels recorded. We conclude that InSAR was able to identify the areas most at risk of subsidence and that it can be used to investigate subsidence over large spatial extents, whereas UAV data can be used to better understand the dynamics of permafrost degradation at a local level. These findings underpin a monitoring approach for these peatlands.},
	language = {en},
	number = {3},
	urldate = {2022-01-24},
	journal = {Remote Sensing},
	author = {de la Barreda-Bautista, Betsabe and Boyd, Doreen S. and Ledger, Martha and Siewert, Matthias B. and Chandler, Chris and Bradley, Andrew V. and Gee, David and Large, David J. and Olofsson, Johan and Sowter, Andrew and Sjögersten, Sofie},
	month = jan,
	year = {2022},
	note = {Number: 3
Publisher: Multidisciplinary Digital Publishing Institute},
	keywords = {\#nosource, InSAR, peatland, permafrost},
	pages = {444},
}

Permafrost thaw resulting from climate warming is threatening to release carbon from high latitude peatlands. The aim of this research was to determine subsidence rates linked to permafrost thaw in sub-Arctic peatlands in Sweden using historical orthophotographic (orthophotos), Unoccupied Aerial Vehicle (UAV), and Interferometric Synthetic Aperture Radar (InSAR) data. The orthophotos showed that the permafrost palsa on the study sites have been contracting in their areal extent, with the greatest rates of loss between 2002 and 2008. The surface motion estimated from differential digital elevation models from the UAV data showed high levels of subsidence (maximum of −25 cm between 2017 and 2020) around the edges of the raised palsa plateaus. The InSAR data analysis showed that raised palsa areas had the greatest subsidence rates, with maximum subsidence rates of 1.5 cm between 2017 and 2020; however, all wetland vegetation types showed subsidence. We suggest that the difference in spatial units associated with each sensor explains parts of the variation in the subsidence levels recorded. We conclude that InSAR was able to identify the areas most at risk of subsidence and that it can be used to investigate subsidence over large spatial extents, whereas UAV data can be used to better understand the dynamics of permafrost degradation at a local level. These findings underpin a monitoring approach for these peatlands.

@article{hough_coupling_2022,
	title = {Coupling plant litter quantity to a novel metric for litter quality explains {C} storage changes in a thawing permafrost peatland},
	volume = {28},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15970},
	doi = {10.1111/gcb.15970},
	abstract = {Permafrost thaw is a major potential feedback source to climate change as it can drive the increased release of greenhouse gases carbon dioxide (CO2) and methane (CH4). This carbon release from the decomposition of thawing soil organic material can be mitigated by increased net primary productivity (NPP) caused by warming, increasing atmospheric CO2, and plant community transition. However, the net effect on C storage also depends on how these plant community changes alter plant litter quantity, quality, and decomposition rates. Predicting decomposition rates based on litter quality remains challenging, but a promising new way forward is to incorporate measures of the energetic favorability to soil microbes of plant biomass decomposition. We asked how the variation in one such measure, the nominal oxidation state of carbon (NOSC), interacts with changing quantities of plant material inputs to influence the net C balance of a thawing permafrost peatland. We found: (1) Plant productivity (NPP) increased post-thaw, but instead of contributing to increased standing biomass, it increased plant biomass turnover via increased litter inputs to soil; (2) Plant litter thermodynamic favorability (NOSC) and decomposition rate both increased post-thaw, despite limited changes in bulk C:N ratios; (3) these increases caused the higher NPP to cycle more rapidly through both plants and soil, contributing to higher CO2 and CH4 fluxes from decomposition. Thus, the increased C-storage expected from higher productivity was limited and the high global warming potential of CH4 contributed a net positive warming effect. Although post-thaw peatlands are currently C sinks due to high NPP offsetting high CO2 release, this status is very sensitive to the plant community's litter input rate and quality. Integration of novel bioavailability metrics based on litter chemistry, including NOSC, into studies of ecosystem dynamics, is needed to improve the understanding of controls on arctic C stocks under continued ecosystem transition.},
	language = {en},
	number = {3},
	urldate = {2022-01-20},
	journal = {Global Change Biology},
	author = {Hough, Moira and McCabe, Samantha and Vining, S. Rose and Pickering Pedersen, Emily and Wilson, Rachel M. and Lawrence, Ryan and Chang, Kuang-Yu and Bohrer, Gil and Coordinators, The IsoGenie and Riley, William J. and Crill, Patrick M. and Varner, Ruth K. and Blazewicz, Steven J. and Dorrepaal, Ellen and Tfaily, Malak M. and Saleska, Scott R. and Rich, Virginia I.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15970},
	keywords = {\#nosource, C storage, NOSC, Stordalen Mire, decomposition, litter chemistry, peat, permafrost thaw, plant community change},
	pages = {950--968},
}

Permafrost thaw is a major potential feedback source to climate change as it can drive the increased release of greenhouse gases carbon dioxide (CO2) and methane (CH4). This carbon release from the decomposition of thawing soil organic material can be mitigated by increased net primary productivity (NPP) caused by warming, increasing atmospheric CO2, and plant community transition. However, the net effect on C storage also depends on how these plant community changes alter plant litter quantity, quality, and decomposition rates. Predicting decomposition rates based on litter quality remains challenging, but a promising new way forward is to incorporate measures of the energetic favorability to soil microbes of plant biomass decomposition. We asked how the variation in one such measure, the nominal oxidation state of carbon (NOSC), interacts with changing quantities of plant material inputs to influence the net C balance of a thawing permafrost peatland. We found: (1) Plant productivity (NPP) increased post-thaw, but instead of contributing to increased standing biomass, it increased plant biomass turnover via increased litter inputs to soil; (2) Plant litter thermodynamic favorability (NOSC) and decomposition rate both increased post-thaw, despite limited changes in bulk C:N ratios; (3) these increases caused the higher NPP to cycle more rapidly through both plants and soil, contributing to higher CO2 and CH4 fluxes from decomposition. Thus, the increased C-storage expected from higher productivity was limited and the high global warming potential of CH4 contributed a net positive warming effect. Although post-thaw peatlands are currently C sinks due to high NPP offsetting high CO2 release, this status is very sensitive to the plant community's litter input rate and quality. Integration of novel bioavailability metrics based on litter chemistry, including NOSC, into studies of ecosystem dynamics, is needed to improve the understanding of controls on arctic C stocks under continued ecosystem transition.

@article{costello_global_2022,
	title = {Global {Patterns} and {Controls} of {Nutrient} {Immobilization} on {Decomposing} {Cellulose} in {Riverine} {Ecosystems}},
	volume = {36},
	issn = {1944-9224},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021GB007163},
	doi = {10.1029/2021GB007163},
	abstract = {Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.},
	language = {en},
	number = {3},
	urldate = {2022-05-04},
	journal = {Global Biogeochemical Cycles},
	author = {Costello, David M. and Tiegs, Scott D. and Boyero, Luz and Canhoto, Cristina and Capps, Krista A. and Danger, Michael and Frost, Paul C. and Gessner, Mark O. and Griffiths, Natalie A. and Halvorson, Halvor M. and Kuehn, Kevin A. and Marcarelli, Amy M. and Royer, Todd V. and Mathie, Devan M. and Albariño, Ricardo J. and Arango, Clay P. and Aroviita, Jukka and Baxter, Colden V. and Bellinger, Brent J. and Bruder, Andreas and Burdon, Francis J. and Callisto, Marcos and Camacho, Antonio and Colas, Fanny and Cornut, Julien and Crespo-Pérez, Verónica and Cross, Wyatt F. and Derry, Alison M. and Douglas, Michael M. and Elosegi, Arturo and de Eyto, Elvira and Ferreira, Verónica and Ferriol, Carmen and Fleituch, Tadeusz and Follstad Shah, Jennifer J. and Frainer, André and Garcia, Erica A. and García, Liliana and García, Pavel E. and Giling, Darren P. and Gonzales-Pomar, R. Karina and Graça, Manuel A. S. and Grossart, Hans-Peter and Guérold, François and Hepp, Luiz U. and Higgins, Scott N. and Hishi, Takuo and Iñiguez-Armijos, Carlos and Iwata, Tomoya and Kirkwood, Andrea E. and Koning, Aaron A. and Kosten, Sarian and Laudon, Hjalmar and Leavitt, Peter R. and Lemes da Silva, Aurea L. and Leroux, Shawn J. and LeRoy, Carri J. and Lisi, Peter J. and Masese, Frank O. and McIntyre, Peter B. and McKie, Brendan G. and Medeiros, Adriana O. and Miliša, Marko and Miyake, Yo and Mooney, Robert J. and Muotka, Timo and Nimptsch, Jorge and Paavola, Riku and Pardo, Isabel and Parnikoza, Ivan Y. and Patrick, Christopher J. and Peeters, Edwin T. H. M. and Pozo, Jesus and Reid, Brian and Richardson, John S. and Rincón, José and Risnoveanu, Geta and Robinson, Christopher T. and Santamans, Anna C. and Simiyu, Gelas M. and Skuja, Agnija and Smykla, Jerzy and Sponseller, Ryan A. and Teixeira-de Mello, Franco and Vilbaste, Sirje and Villanueva, Verónica D. and Webster, Jackson R. and Woelfl, Stefan and Xenopoulos, Marguerite A. and Yates, Adam G. and Yule, Catherine M. and Zhang, Yixin and Zwart, Jacob A.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021GB007163},
	keywords = {\#nosource, cotton strip assay, ecological stoichiometry, nitrogen, nutrient cycling, organic matter, phosphorus},
	pages = {e2021GB007163},
}

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.

@article{gavazov_plant-microbial_2022,
	title = {Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types},
	volume = {165},
	issn = {0038-0717},
	url = {https://www.sciencedirect.com/science/article/pii/S0038071721004041},
	doi = {10.1016/j.soilbio.2021.108530},
	abstract = {Tundra ecosystems hold large stocks of soil organic matter (SOM), likely due to low temperatures limiting rates of microbial SOM decomposition more than those of SOM accumulation from plant primary productivity and microbial necromass inputs. Here we test the hypotheses that distinct tundra vegetation types and their carbon supply to characteristic rhizosphere microbes determine SOM cycling independent of temperature. In the subarctic Scandes, we used a three-way factorial design with paired heath and meadow vegetation at each of two elevations, and with each combination of vegetation type and elevation subjected during one growing season to either ambient light (i.e., ambient plant productivity), or 95\% shading (i.e., reduced plant productivity). We assessed potential above- and belowground ecosystem linkages by uni- and multivariate analyses of variance, and structural equation modelling. We observed direct coupling between tundra vegetation type and microbial community composition and function, which underpinned the ecosystem's potential for SOM storage. Greater primary productivity at low elevation and ambient light supported higher microbial biomass and nitrogen immobilisation, with lower microbial mass-specific enzymatic activity and SOM humification. Congruently, larger SOM at lower elevation and in heath sustained fungal-dominated microbial communities, which were less substrate-limited, and invested less into enzymatic SOM mineralisation, owing to a greater carbon-use efficiency (CUE). Our results highlight the importance of tundra plant community characteristics (i.e., productivity and vegetation type), via their effects on soil microbial community size, structure and physiology, as essential drivers of SOM turnover. The here documented concerted patterns in above- and belowground ecosystem functioning is strongly supportive of using plant community characteristics as surrogates for assessing tundra carbon storage potential and its evolution under climate and vegetation changes.},
	language = {en},
	urldate = {2022-01-20},
	journal = {Soil Biology and Biochemistry},
	author = {Gavazov, Konstantin and Canarini, Alberto and Jassey, Vincent E. J. and Mills, Robert and Richter, Andreas and Sundqvist, Maja K. and Väisänen, Maria and Walker, Tom W. N. and Wardle, David A. and Dorrepaal, Ellen},
	month = feb,
	year = {2022},
	keywords = {\#nosource, Above- and belowground interactions, C:N stoichiometry, Carbon use efficiency, Elevation gradient, Microbial physiology, Primary productivity},
	pages = {108530},
}

Tundra ecosystems hold large stocks of soil organic matter (SOM), likely due to low temperatures limiting rates of microbial SOM decomposition more than those of SOM accumulation from plant primary productivity and microbial necromass inputs. Here we test the hypotheses that distinct tundra vegetation types and their carbon supply to characteristic rhizosphere microbes determine SOM cycling independent of temperature. In the subarctic Scandes, we used a three-way factorial design with paired heath and meadow vegetation at each of two elevations, and with each combination of vegetation type and elevation subjected during one growing season to either ambient light (i.e., ambient plant productivity), or 95% shading (i.e., reduced plant productivity). We assessed potential above- and belowground ecosystem linkages by uni- and multivariate analyses of variance, and structural equation modelling. We observed direct coupling between tundra vegetation type and microbial community composition and function, which underpinned the ecosystem's potential for SOM storage. Greater primary productivity at low elevation and ambient light supported higher microbial biomass and nitrogen immobilisation, with lower microbial mass-specific enzymatic activity and SOM humification. Congruently, larger SOM at lower elevation and in heath sustained fungal-dominated microbial communities, which were less substrate-limited, and invested less into enzymatic SOM mineralisation, owing to a greater carbon-use efficiency (CUE). Our results highlight the importance of tundra plant community characteristics (i.e., productivity and vegetation type), via their effects on soil microbial community size, structure and physiology, as essential drivers of SOM turnover. The here documented concerted patterns in above- and belowground ecosystem functioning is strongly supportive of using plant community characteristics as surrogates for assessing tundra carbon storage potential and its evolution under climate and vegetation changes.

@article{manasypov_carbon_2022,
	title = {Carbon storage and burial in thermokarst lakes of permafrost peatlands},
	volume = {159},
	issn = {1573-515X},
	url = {https://doi.org/10.1007/s10533-022-00914-y},
	doi = {10.1007/s10533-022-00914-y},
	abstract = {Thermokarst (thaw) lakes of the Western Siberian Lowland (WSL), the World´s largest permafrost peatland, contain important but poorly constrained stocks of organic carbon (OC) and nitrogen. These lakes are highly vulnerable to climate warming and permafrost thaw. The present work aims to quantify the OC and total nitrogen (TN) stocks and accumulation rates in sediments of 11 thermokarst lakes in the WSL across a permafrost gradient, from isolated to discontinuous and continuous permafrost. We found an increase in OC and TN stocks in lake sediments (0–30 cm) from the northern taiga with sporadic permafrost (285 Tg C and 10.5 Tg N) to the tundra zone with continuous permafrost (628 Tg C and 26 Tg N). The upper 30 cm thermokarst lake sediments of the permafrost-affected WSL store 1250 ± 35 Tg C and 50 ± 1.4 Tg N). The OC accumulation rates in thermokarst lake sediments ranged from 36 to 250 g C m−2 year−1, which is 5 to 10 times higher than C accumulation rates in peatlands of western Siberia. The total OC accumulation in lakes of WSL is 7.8 ± 0.7 Tg C year−1. This is about 24–47\% of the C emission from the WSL thermokarst lakes, implying that it represents an important factor in the C budget to consider in order to understand impacts of climate change and permafrost thaw on the C cycle.},
	language = {en},
	number = {1},
	urldate = {2022-05-04},
	journal = {Biogeochemistry},
	author = {Manasypov, R. M. and Lim, A. G. and Krickov, I. V. and Shirokova, L. S. and Shevchenko, V. P. and Aliev, R. A. and Karlsson, J. and Pokrovsky, O. S.},
	month = may,
	year = {2022},
	keywords = {\#nosource, Accumulation, Organic carbon, Sediments, Storage, Thermokarst lakes, Western Siberia},
	pages = {69--86},
}

Thermokarst (thaw) lakes of the Western Siberian Lowland (WSL), the World´s largest permafrost peatland, contain important but poorly constrained stocks of organic carbon (OC) and nitrogen. These lakes are highly vulnerable to climate warming and permafrost thaw. The present work aims to quantify the OC and total nitrogen (TN) stocks and accumulation rates in sediments of 11 thermokarst lakes in the WSL across a permafrost gradient, from isolated to discontinuous and continuous permafrost. We found an increase in OC and TN stocks in lake sediments (0–30 cm) from the northern taiga with sporadic permafrost (285 Tg C and 10.5 Tg N) to the tundra zone with continuous permafrost (628 Tg C and 26 Tg N). The upper 30 cm thermokarst lake sediments of the permafrost-affected WSL store 1250 ± 35 Tg C and 50 ± 1.4 Tg N). The OC accumulation rates in thermokarst lake sediments ranged from 36 to 250 g C m−2 year−1, which is 5 to 10 times higher than C accumulation rates in peatlands of western Siberia. The total OC accumulation in lakes of WSL is 7.8 ± 0.7 Tg C year−1. This is about 24–47% of the C emission from the WSL thermokarst lakes, implying that it represents an important factor in the C budget to consider in order to understand impacts of climate change and permafrost thaw on the C cycle.

@article{puts_ecological_2022,
	title = {An ecological and methodological assessment of benthic gross primary production in northern lakes},
	volume = {13},
	issn = {2150-8925},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ecs2.3973},
	doi = {10.1002/ecs2.3973},
	abstract = {Benthic gross primary production (GPP) is often the most important part of aquatic food webs in northern lakes, which are gradually warming and receiving increased terrestrial colored dissolved organic carbon loadings due to global change. Yet, measurements of benthic GPP are fairly uncommon, and methods and unit dimensions of benthic GPP are unstandardized and rarely compared. In this study, we measured benthic GPP in 27 headwater lakes from three regions in northern Sweden and analyzed potential constraining drivers of benthic GPPz rates at discrete depths and estimates of benthic GPP averages across the whole lake, as well as across the littoral zone. We also compared in situ measurements of benthic GPP averages across the whole lake with modeled values using the “autotrophic structuring model.” We found that benthic GPPz rates were best explained by, and positively related to, available light (i.e., a function of depth and water color) and temperature. Benthic GPP averages across the whole lake, on the contrary, were best explained by the relative size of the littoral area, which is a measure that combines lake bathymetry and water color. The comparison between in situ measured and modeled estimates of benthic GPP averages across the whole lake revealed that (1) the autotrophic structuring model underestimates GPP at low values and overestimates GPP at high values compared with measured data, and that (2) measured values were related to temperature, which is not included as a variable in the autotrophic structuring model. Considering future predicted changes impacting northern latitude lakes, our results suggest that increased lake water temperatures can to some extent mitigate the negative impacts of reduced light availability from lake browning on benthic GPPz rates. The combined impact of these changes on benthic GPP averages across the whole lake will depend on, and be moderated by, lake bathymetry determining the relative size of the littoral area.},
	language = {en},
	number = {3},
	urldate = {2022-05-04},
	journal = {Ecosphere},
	author = {Puts, I. C. and Bergström, A.-K. and Verheijen, H. A. and Norman, S. and Ask, J.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.3973},
	keywords = {\#nosource, dissolved organic carbon, freshwater, gross primary production, littoral, soft sediments, upscaling},
	pages = {e3973},
}

Benthic gross primary production (GPP) is often the most important part of aquatic food webs in northern lakes, which are gradually warming and receiving increased terrestrial colored dissolved organic carbon loadings due to global change. Yet, measurements of benthic GPP are fairly uncommon, and methods and unit dimensions of benthic GPP are unstandardized and rarely compared. In this study, we measured benthic GPP in 27 headwater lakes from three regions in northern Sweden and analyzed potential constraining drivers of benthic GPPz rates at discrete depths and estimates of benthic GPP averages across the whole lake, as well as across the littoral zone. We also compared in situ measurements of benthic GPP averages across the whole lake with modeled values using the “autotrophic structuring model.” We found that benthic GPPz rates were best explained by, and positively related to, available light (i.e., a function of depth and water color) and temperature. Benthic GPP averages across the whole lake, on the contrary, were best explained by the relative size of the littoral area, which is a measure that combines lake bathymetry and water color. The comparison between in situ measured and modeled estimates of benthic GPP averages across the whole lake revealed that (1) the autotrophic structuring model underestimates GPP at low values and overestimates GPP at high values compared with measured data, and that (2) measured values were related to temperature, which is not included as a variable in the autotrophic structuring model. Considering future predicted changes impacting northern latitude lakes, our results suggest that increased lake water temperatures can to some extent mitigate the negative impacts of reduced light availability from lake browning on benthic GPPz rates. The combined impact of these changes on benthic GPP averages across the whole lake will depend on, and be moderated by, lake bathymetry determining the relative size of the littoral area.

@article{sytiuk_biochemical_2022,
	title = {Biochemical traits enhance the trait concept in {Sphagnum} ecology},
	volume = {2022},
	issn = {1600-0706},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/oik.09119},
	doi = {10.1111/oik.09119},
	abstract = {Sphagnum mosses are key to northern peatland carbon sequestration. They have a range of morphological and anatomical characteristics that allow them to cope with environmental stress. Sphagnum also produces a plethora of biochemicals that may prevent stress-induced cell-damage. However, the linkages between Sphagnum anatomical, morphological and biochemical traits (i.e. metabolites, pigments and antioxidant enzyme activities) are poorly known, neither are their joint responses to environmental change. Here, we quantify and link an array of Sphagnum anatomical, morphological and biochemical traits in five Sphagnum-dominated peatlands distributed along a latitudinal gradient in Europe, covering a range of regional and local environmental conditions. Sphagnum morphological and anatomical traits were intrinsically linked to Sphagnum metabolites and enzyme activities, and these relationships were driven by shared responses to local and regional environmental factors. More particularly, we found that Sphagnum traits can be grouped into four clusters related to growth, biomass, defense and water stress tolerance. We used regional and local environmental conditions data to further show that biochemicals and their specific linkages with some morphological traits describe dimensions of physiology not captured by anatomical and morphological traits alone. These results suggest that Sphagnum morphology and function is rooted in the metabolome, and that incorporating biochemicals into the functional trait space concept can enhance our mechanistic understanding and predictive power in Sphagnum ecology.},
	language = {en},
	number = {4},
	urldate = {2022-05-04},
	journal = {Oikos},
	author = {Sytiuk, Anna and Céréghino, Regis and Hamard, Samuel and Delarue, Frédéric and Dorrepaal, Ellen and Küttim, Martin and Lamentowicz, Mariusz and Pourrut, Bertrand and Robroek, Bjorn J. M. and Tuittila, Eeva-Stiina and Jassey, Vincent E. J.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/oik.09119},
	keywords = {\#nosource, Sphagnum, antioxidant enzyme activities, bryophytes, climate change, metabolites, peatlands},
	pages = {e09119},
}

Sphagnum mosses are key to northern peatland carbon sequestration. They have a range of morphological and anatomical characteristics that allow them to cope with environmental stress. Sphagnum also produces a plethora of biochemicals that may prevent stress-induced cell-damage. However, the linkages between Sphagnum anatomical, morphological and biochemical traits (i.e. metabolites, pigments and antioxidant enzyme activities) are poorly known, neither are their joint responses to environmental change. Here, we quantify and link an array of Sphagnum anatomical, morphological and biochemical traits in five Sphagnum-dominated peatlands distributed along a latitudinal gradient in Europe, covering a range of regional and local environmental conditions. Sphagnum morphological and anatomical traits were intrinsically linked to Sphagnum metabolites and enzyme activities, and these relationships were driven by shared responses to local and regional environmental factors. More particularly, we found that Sphagnum traits can be grouped into four clusters related to growth, biomass, defense and water stress tolerance. We used regional and local environmental conditions data to further show that biochemicals and their specific linkages with some morphological traits describe dimensions of physiology not captured by anatomical and morphological traits alone. These results suggest that Sphagnum morphology and function is rooted in the metabolome, and that incorporating biochemicals into the functional trait space concept can enhance our mechanistic understanding and predictive power in Sphagnum ecology.

@article{vincent_soil_2022,
	title = {Soil phosphorus forms show only minor changes across a 5000-year-old boreal wildfire chronosequence},
	volume = {159},
	issn = {1573-515X},
	url = {https://doi.org/10.1007/s10533-022-00910-2},
	doi = {10.1007/s10533-022-00910-2},
	abstract = {Wildfire is the main disturbance in most boreal forests. In the prolonged absence of wildfire, ecosystem retrogression occurs, which is characterized by reduced productivity, plant biomass and belowground process rates. Previous evidence suggests that phosphorus (P) decreases during retrogression, but the mechanisms involved remain poorly understood. Here we use 1-D 31P and 2-D, 1H-31P NMR to characterize changes in humus P composition across a 5000 year post-fire chronosequence in northern Sweden, to understand why P availability declines during long term fire absence. Against expectations, humus P composition varied only modestly with increasing time since fire. Using a method to back-calculate the in situ soil organic P speciation, we found that it was dominated by biologically active compounds such as RNA (41\%), phospholipids (28\%) and DNA (22\%). The concentration of DNA and pyrophosphate was 19\% and 29\% lower, respectively, on infrequently burnt than recently burnt islands, and the concentration of DNA, phospholipids and nucleotides was positively correlated with net primary productivity (NPP). Given the lack of evidence for the accumulation of “recalcitrant” P or a geochemical P sink, reductions in P availability during retrogression may be associated with impaired P cycling through slower decomposition rates, and increasing humus depth separating surface humus from P-rich mineral soil. Our findings align with observed negative relationships between NPP and organic P concentration across other chronosequences. They also suggest that changing fire regimes in the boreal zone could indirectly affect the P cycle through changes in NPP and soil microflora rather than through changes in humus P composition.},
	language = {en},
	number = {1},
	urldate = {2022-05-04},
	journal = {Biogeochemistry},
	author = {Vincent, Andrea G. and Schleucher, Jürgen and Giesler, Reiner and Wardle, David A.},
	month = may,
	year = {2022},
	keywords = {\#nosource, Anthropogenic fire suppression, Arjeplog, Ecosystem retrogression, Fennoscandia, One-dimensional 31P NMR, Two-dimensional 1H, 31P NMR},
	pages = {15--32},
}

Wildfire is the main disturbance in most boreal forests. In the prolonged absence of wildfire, ecosystem retrogression occurs, which is characterized by reduced productivity, plant biomass and belowground process rates. Previous evidence suggests that phosphorus (P) decreases during retrogression, but the mechanisms involved remain poorly understood. Here we use 1-D 31P and 2-D, 1H-31P NMR to characterize changes in humus P composition across a 5000 year post-fire chronosequence in northern Sweden, to understand why P availability declines during long term fire absence. Against expectations, humus P composition varied only modestly with increasing time since fire. Using a method to back-calculate the in situ soil organic P speciation, we found that it was dominated by biologically active compounds such as RNA (41%), phospholipids (28%) and DNA (22%). The concentration of DNA and pyrophosphate was 19% and 29% lower, respectively, on infrequently burnt than recently burnt islands, and the concentration of DNA, phospholipids and nucleotides was positively correlated with net primary productivity (NPP). Given the lack of evidence for the accumulation of “recalcitrant” P or a geochemical P sink, reductions in P availability during retrogression may be associated with impaired P cycling through slower decomposition rates, and increasing humus depth separating surface humus from P-rich mineral soil. Our findings align with observed negative relationships between NPP and organic P concentration across other chronosequences. They also suggest that changing fire regimes in the boreal zone could indirectly affect the P cycle through changes in NPP and soil microflora rather than through changes in humus P composition.

@article{bastias_seasonal_2022,
	title = {Seasonal variation in the coupling of microbial activity and leaf litter decomposition in a boreal stream network},
	volume = {67},
	issn = {1365-2427},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.13883},
	doi = {10.1111/fwb.13883},
	abstract = {Most stream networks are characterised by spatial and temporal variability in the physico-chemical conditions that regulate microbial processing of particulate organic matter. How these patterns control the turnover of particulate organic matter via altered activity of leaf-associated microbes has rarely been studied in high-latitude landscapes, particularly throughout long (i.e., up to 6 months) ice- and snow-covered periods. We investigated development of fungal biomass, enzyme activity, microbial respiration, and birch leaf litter decomposition from autumn to early summer in 11 nested streams in a boreal catchment that encompass a gradient in wetland (mire) cover. We observed relatively low variability in decomposition rates across the network, despite differences in key physical and chemical variables (e.g. temperature, pH, and dissolved organic carbon [DOC] concentrations) over time and space. Microbial enzymatic activity and respiration were positively related to leaf litter decomposition rates during early stages of decomposition (i.e., up to c. 30\% loss of initial ash-free dry mass). Thereafter, variation in microbial activity and respiration was decoupled from leaf litter mass loss, as enzymatic activity and respiration instead became positively related to DOC concentrations and upstream mire (wetland) cover among streams. Our results suggest that leaf-associated microbes increase their reliance on external sources of energy over time. This switch in resource use was more evident in streams with higher DOC concentration, which in boreal landscapes is largely determined by mire cover. Hence, variation in DOC concentration, linked to landscape configuration, or from intensified land use and climate change, could affect how different carbon sources are used by stream microbial communities, with consequences for overall carbon cycling in boreal headwaters.},
	language = {en},
	number = {5},
	urldate = {2022-05-04},
	journal = {Freshwater Biology},
	author = {Bastias, Elliot and Sponseller, Ryan A. and Bundschuh, Mirco and Jonsson, Micael},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.13883},
	keywords = {\#nosource, Krycklan Catchment Study, birch, cellobiohydrolase, extracellular enzyme activity, leaf-use efficiency},
	pages = {812--827},
}

Most stream networks are characterised by spatial and temporal variability in the physico-chemical conditions that regulate microbial processing of particulate organic matter. How these patterns control the turnover of particulate organic matter via altered activity of leaf-associated microbes has rarely been studied in high-latitude landscapes, particularly throughout long (i.e., up to 6 months) ice- and snow-covered periods. We investigated development of fungal biomass, enzyme activity, microbial respiration, and birch leaf litter decomposition from autumn to early summer in 11 nested streams in a boreal catchment that encompass a gradient in wetland (mire) cover. We observed relatively low variability in decomposition rates across the network, despite differences in key physical and chemical variables (e.g. temperature, pH, and dissolved organic carbon [DOC] concentrations) over time and space. Microbial enzymatic activity and respiration were positively related to leaf litter decomposition rates during early stages of decomposition (i.e., up to c. 30% loss of initial ash-free dry mass). Thereafter, variation in microbial activity and respiration was decoupled from leaf litter mass loss, as enzymatic activity and respiration instead became positively related to DOC concentrations and upstream mire (wetland) cover among streams. Our results suggest that leaf-associated microbes increase their reliance on external sources of energy over time. This switch in resource use was more evident in streams with higher DOC concentration, which in boreal landscapes is largely determined by mire cover. Hence, variation in DOC concentration, linked to landscape configuration, or from intensified land use and climate change, could affect how different carbon sources are used by stream microbial communities, with consequences for overall carbon cycling in boreal headwaters.

@article{blume-werry_belowground_2022,
	title = {The belowground growing season},
	volume = {12},
	copyright = {2021 Springer Nature Limited},
	issn = {1758-6798},
	url = {http://www.nature.com/articles/s41558-021-01243-y},
	doi = {10.1038/s41558-021-01243-y},
	abstract = {As temperatures rise, plants unfold their leaves earlier in spring, but whether plant roots respond similarly is seldom quantified. Now, a meta-analysis suggests that leaf and root phenology do not respond to warming in the same way, even within the same plant types.},
	language = {en},
	number = {1},
	urldate = {2022-01-17},
	journal = {Nature Climate Change},
	author = {Blume-Werry, Gesche},
	month = jan,
	year = {2022},
	note = {Bandiera\_abtest: a
Cg\_type: Nature Research Journals
Number: 1
Primary\_atype: News \& Views
Publisher: Nature Publishing Group
Subject\_term: Ecosystem ecology;Phenology
Subject\_term\_id: ecosystem-ecology;phenology},
	keywords = {\#nosource, Ecosystem ecology, Phenology},
	pages = {11--12},
}

As temperatures rise, plants unfold their leaves earlier in spring, but whether plant roots respond similarly is seldom quantified. Now, a meta-analysis suggests that leaf and root phenology do not respond to warming in the same way, even within the same plant types.

@article{seekell_scaling_2022,
	title = {The {Scaling} {Relationship} for the {Length} of {Tributaries} to {Lakes}},
	volume = {49},
	issn = {1944-8007},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GL098183},
	doi = {10.1029/2022GL098183},
	abstract = {Globally, the length of tributaries to lakes varies from 0 to more than 15,000 km, but scaling relationships describing this aspect of lake-river connectivity are lacking. In this study, we describe a simple theoretical scaling relationship for tributary length based on the principle of line intercepts of topographic features, and test this theory using data from Scandinavia. Tributary length increases by 73\% for each doubling of lake area. This pattern reflects the relationship between catchment and lake area, and is modified by inlet frequency, junction angle, and lake shape—factors related to specific geologic and hydrologic processes. The theory is precise (r2 = 0.74), with low bias (mean error is 14\% of mean tributary length) when the characteristic junction angle (∼76°) is estimated statistically. Our study bridges the gap between geomorphic and large-scale statistical relationships to provide simple rules for understanding complex patterns of lake-river connectivity.},
	language = {en},
	number = {7},
	urldate = {2022-05-04},
	journal = {Geophysical Research Letters},
	author = {Seekell, D. and Cael, B. and Byström, P.},
	year = {2022},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GL098183},
	keywords = {\#nosource, hydrography, junction angle, lake-river connectivity, limnology, scaling},
	pages = {e2022GL098183},
}

Globally, the length of tributaries to lakes varies from 0 to more than 15,000 km, but scaling relationships describing this aspect of lake-river connectivity are lacking. In this study, we describe a simple theoretical scaling relationship for tributary length based on the principle of line intercepts of topographic features, and test this theory using data from Scandinavia. Tributary length increases by 73% for each doubling of lake area. This pattern reflects the relationship between catchment and lake area, and is modified by inlet frequency, junction angle, and lake shape—factors related to specific geologic and hydrologic processes. The theory is precise (r2 = 0.74), with low bias (mean error is 14% of mean tributary length) when the characteristic junction angle (∼76°) is estimated statistically. Our study bridges the gap between geomorphic and large-scale statistical relationships to provide simple rules for understanding complex patterns of lake-river connectivity.

@article{klaus_unravelling_2022,
	title = {Unravelling the {Contribution} of {Turbulence} and {Bubbles} to {Air}-{Water} {Gas} {Exchange} in {Running} {Waters}},
	volume = {127},
	url = {https://hal-insu.archives-ouvertes.fr/insu-03578679},
	doi = {10.1029/2021JG006520},
	abstract = {Quantifying air-water gas exchange is critical for estimating greenhouse gas fluxes and metabolism in aquatic ecosystems. In high-energy streams, the gas exchange rate k is poorly constrained, due to an incomplete understanding of turbulence and bubble contributions to k. We performed a flume experiment with air bubble additions to evaluate the combined effects of turbulence and bubbles on k for helium, argon, xenon, and methane. We created contrasting hydraulic conditions by varying channel slope, bed roughness, water discharge, and bubble flux. We found that k increased from 1−4 to 17−66 m d-1 with increases in turbulence and bubble flux metrics. Mechanistic models that explicitly account for these metrics, as well as gas diffusivity and solubility agreed well with the data and indicated that bubble-mediated gas exchange accounted for 64−93\% of k. Bubble contributions increased with bubble flux but were independent of gas type, as bubbles did not equilibrate with the water. This was evident through modelled bubble life and equilibration times inferred from bubble size distributions obtained from underwater sound spectra. Sound spectral properties correlated well with turbulence and bubble flux metrics. Our results demonstrate that i) mechanistic models can be applied to separate free surface- and bubble-mediated gas exchange in running waters, ii) bubble life and equilibration times are critical for accurate scaling of k between different gases, and iii) ambient sound spectra can be used to approximate contributions of turbulence and bubbles.},
	number = {3},
	urldate = {2022-05-04},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Klaus, Marcus and Labasque, Thierry and Botter, G. and Durighetto, N. and Schelker, J.},
	year = {2022},
	note = {Publisher: American Geophysical Union},
	keywords = {\#nosource},
	pages = {e2021JG006520},
}

Quantifying air-water gas exchange is critical for estimating greenhouse gas fluxes and metabolism in aquatic ecosystems. In high-energy streams, the gas exchange rate k is poorly constrained, due to an incomplete understanding of turbulence and bubble contributions to k. We performed a flume experiment with air bubble additions to evaluate the combined effects of turbulence and bubbles on k for helium, argon, xenon, and methane. We created contrasting hydraulic conditions by varying channel slope, bed roughness, water discharge, and bubble flux. We found that k increased from 1−4 to 17−66 m d-1 with increases in turbulence and bubble flux metrics. Mechanistic models that explicitly account for these metrics, as well as gas diffusivity and solubility agreed well with the data and indicated that bubble-mediated gas exchange accounted for 64−93% of k. Bubble contributions increased with bubble flux but were independent of gas type, as bubbles did not equilibrate with the water. This was evident through modelled bubble life and equilibration times inferred from bubble size distributions obtained from underwater sound spectra. Sound spectral properties correlated well with turbulence and bubble flux metrics. Our results demonstrate that i) mechanistic models can be applied to separate free surface- and bubble-mediated gas exchange in running waters, ii) bubble life and equilibration times are critical for accurate scaling of k between different gases, and iii) ambient sound spectra can be used to approximate contributions of turbulence and bubbles.

@article{siewert_permafrost_2021,
	title = {Permafrost {Causes} {Unique} {Fine}-{Scale} {Spatial} {Variability} {Across} {Tundra} {Soils}},
	volume = {35},
	copyright = {© 2021. The Authors.},
	issn = {1944-9224},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020GB006659},
	doi = {10.1029/2020GB006659},
	abstract = {Spatial analysis in earth sciences is often based on the concept of spatial autocorrelation, expressed by W. Tobler as the first law of geography: “everything is related to everything else, but near things are more related than distant things.' Here, we show that subsurface soil properties in permafrost tundra terrain exhibit tremendous spatial variability. We describe the subsurface variability of soil organic carbon (SOC) and ground ice content from the centimeter to the landscape scale in three typical tundra terrain types common across the Arctic region. At the soil pedon scale, that is, from centimeters to 1–2 m, variability is caused by cryoturbation and affected by tussocks, hummocks and nonsorted circles. At the terrain scale, from meters to tens of meters, variability is caused by different generations of ice-wedges. Variability at the landscape scale, that is, ranging hundreds of meters, is associated with geomorphic disturbances and catenary shifts. The co-occurrence and overlap of different processes and landforms creates a spatial structure unique to permafrost environments. The coefficient of variation of SOC at the pedon scale (21\%–73\%) exceeds that found at terrain (17\%–66\%) and even landscape scale (24\%–67\%). Such high values for spatial variation are otherwise found at regional to continental scale. Clearly, permafrost soils do not conform to Tobler's law, but are among the most variable soils on Earth. This needs to be accounted for in mapping and predictions of the permafrost carbon feedbacks through various ecosystem processes. We conclude that scale deserves special attention in permafrost regions.},
	language = {en},
	number = {3},
	urldate = {2024-03-27},
	journal = {Global Biogeochemical Cycles},
	author = {Siewert, M. B. and Lantuit, H. and Richter, A. and Hugelius, G.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020GB006659},
	keywords = {\#nosource, ground ice, permafrost, scale, soil organic carbon, tundra soils},
	pages = {e2020GB006659},
}

Spatial analysis in earth sciences is often based on the concept of spatial autocorrelation, expressed by W. Tobler as the first law of geography: “everything is related to everything else, but near things are more related than distant things.' Here, we show that subsurface soil properties in permafrost tundra terrain exhibit tremendous spatial variability. We describe the subsurface variability of soil organic carbon (SOC) and ground ice content from the centimeter to the landscape scale in three typical tundra terrain types common across the Arctic region. At the soil pedon scale, that is, from centimeters to 1–2 m, variability is caused by cryoturbation and affected by tussocks, hummocks and nonsorted circles. At the terrain scale, from meters to tens of meters, variability is caused by different generations of ice-wedges. Variability at the landscape scale, that is, ranging hundreds of meters, is associated with geomorphic disturbances and catenary shifts. The co-occurrence and overlap of different processes and landforms creates a spatial structure unique to permafrost environments. The coefficient of variation of SOC at the pedon scale (21%–73%) exceeds that found at terrain (17%–66%) and even landscape scale (24%–67%). Such high values for spatial variation are otherwise found at regional to continental scale. Clearly, permafrost soils do not conform to Tobler's law, but are among the most variable soils on Earth. This needs to be accounted for in mapping and predictions of the permafrost carbon feedbacks through various ecosystem processes. We conclude that scale deserves special attention in permafrost regions.

@article{linden_large_2021,
	title = {Large and small herbivores have strong effects on tundra vegetation in {Scandinavia} and {Alaska}},
	volume = {11},
	copyright = {© 2021 The Authors. Ecology and Evolution published by John Wiley \& Sons Ltd.},
	issn = {2045-7758},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ece3.7977},
	doi = {10.1002/ece3.7977},
	abstract = {Large and small mammalian herbivores are present in most vegetated areas in the Arctic and often have large impacts on plant community composition and ecosystem functioning. The relative importance of different herbivores and especially how their specific impact on the vegetation varies across the Arctic is however poorly understood. Here, we investigate how large and small herbivores influence vegetation density and plant community composition in four arctic vegetation types in Scandinavia and Alaska. We used a unique set of exclosures, excluding only large (reindeer and muskoxen) or all mammalian herbivores (also voles and lemmings) for at least 20 years. We found that mammalian herbivores in general decreased leaf area index, NDVI, and abundance of vascular plants in all four locations, even though the strength of the effect and which herbivore type caused these effects differed across locations. In three locations, herbivore presence caused contrasting plant communities, but not in the location with lowest productivity. Large herbivores had a negative effect on plant height, whereas small mammalian herbivores increased species diversity by decreasing dominance of the initially dominating plant species. Above- or belowground disturbances caused by herbivores were found to play an important role in shaping the vegetation in all locations. Synthesis: Based on these results, we conclude that both small and large mammalian herbivores influence vegetation in Scandinavia and Alaska in a similar way, some of which can mitigate effects of climate change. We also see important differences across locations, but these depend rather on local herbivore and plant community composition than large biogeographical differences among continents.},
	language = {en},
	number = {17},
	urldate = {2024-03-27},
	journal = {Ecology and Evolution},
	author = {Lindén, Elin and Gough, Laura and Olofsson, Johan},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.7977},
	keywords = {\#nosource, Arctic, Herbivores, diversity, exclosures, plant communities},
	pages = {12141--12152},
}

Large and small mammalian herbivores are present in most vegetated areas in the Arctic and often have large impacts on plant community composition and ecosystem functioning. The relative importance of different herbivores and especially how their specific impact on the vegetation varies across the Arctic is however poorly understood. Here, we investigate how large and small herbivores influence vegetation density and plant community composition in four arctic vegetation types in Scandinavia and Alaska. We used a unique set of exclosures, excluding only large (reindeer and muskoxen) or all mammalian herbivores (also voles and lemmings) for at least 20 years. We found that mammalian herbivores in general decreased leaf area index, NDVI, and abundance of vascular plants in all four locations, even though the strength of the effect and which herbivore type caused these effects differed across locations. In three locations, herbivore presence caused contrasting plant communities, but not in the location with lowest productivity. Large herbivores had a negative effect on plant height, whereas small mammalian herbivores increased species diversity by decreasing dominance of the initially dominating plant species. Above- or belowground disturbances caused by herbivores were found to play an important role in shaping the vegetation in all locations. Synthesis: Based on these results, we conclude that both small and large mammalian herbivores influence vegetation in Scandinavia and Alaska in a similar way, some of which can mitigate effects of climate change. We also see important differences across locations, but these depend rather on local herbivore and plant community composition than large biogeographical differences among continents.

@article{laudon_legacy_2021,
	title = {From legacy effects of acid deposition in boreal streams to future environmental threats},
	volume = {16},
	issn = {1748-9326},
	url = {https://dx.doi.org/10.1088/1748-9326/abd064},
	doi = {10.1088/1748-9326/abd064},
	abstract = {Few environmental issues have resulted in such a heated policy-science controversy in Sweden as the 1990s acidification debate in the north of the country. The belief that exceptionally high stream acidity levels during hydrological events was caused by anthropogenic deposition resulted in a governmentally funded, multi-million dollar surface-water liming program. This program was heavily criticized by a large part of the scientific community arguing that the acidity of northern streams was primarily caused by naturally occurring organic acids. Here, we revisit the acid deposition legacy in northern Sweden two decades after the culmination of the controversy by examining the long-term water chemistry trends in the Svartberget/Krycklan research catchment that became a nexus for the Swedish debate. In this reference stream, trends in acidic episodes do show a modest recovery that matches declines in acid deposition to pre-industrial levels, although stream acidity continues to be overwhelmingly driven by organic acidity. Yet there are legacies of acid deposition related to calcium losses from soils, which are more pronounced than anticipated. Finally, assessment of these trends are becoming increasingly complicated by new changes and threats to water resources that must be recognized to avoid unnecessary, expensive, and potentially counterproductive measures to adapt and mitigate human influences. Here we make the argument that while the acidification era is ending, climate change, land-use transitions, and long-range transport of other contaminants warrant close monitoring in the decades to come.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Environmental Research Letters},
	author = {Laudon, Hjalmar and Sponseller, Ryan A. and Bishop, Kevin},
	month = jan,
	year = {2021},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {015007},
}

Few environmental issues have resulted in such a heated policy-science controversy in Sweden as the 1990s acidification debate in the north of the country. The belief that exceptionally high stream acidity levels during hydrological events was caused by anthropogenic deposition resulted in a governmentally funded, multi-million dollar surface-water liming program. This program was heavily criticized by a large part of the scientific community arguing that the acidity of northern streams was primarily caused by naturally occurring organic acids. Here, we revisit the acid deposition legacy in northern Sweden two decades after the culmination of the controversy by examining the long-term water chemistry trends in the Svartberget/Krycklan research catchment that became a nexus for the Swedish debate. In this reference stream, trends in acidic episodes do show a modest recovery that matches declines in acid deposition to pre-industrial levels, although stream acidity continues to be overwhelmingly driven by organic acidity. Yet there are legacies of acid deposition related to calcium losses from soils, which are more pronounced than anticipated. Finally, assessment of these trends are becoming increasingly complicated by new changes and threats to water resources that must be recognized to avoid unnecessary, expensive, and potentially counterproductive measures to adapt and mitigate human influences. Here we make the argument that while the acidification era is ending, climate change, land-use transitions, and long-range transport of other contaminants warrant close monitoring in the decades to come.

@article{zabelina_carbon_2021,
	title = {Carbon emission from thermokarst lakes in {NE} {European} tundra},
	volume = {66},
	copyright = {© 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11560},
	doi = {10.1002/lno.11560},
	abstract = {Emission of greenhouse gases (GHGs) from inland waters is recognized as highly important and an understudied part of the terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in subarctic regions that contain vast amounts of surface C in permafrost peatlands. This is especially true in NE European peatlands, located within sporadic to discontinuous permafrost zones which are highly vulnerable to thaw. Initial measurements of C emissions from lentic waters of the Bolshezemelskaya Tundra (BZT; 200,000 km2) demonstrated sizable CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds, and thermokarst lakes ranging from 0.5 × 106 to 5 × 106 m2 in size. CO2 fluxes decreased by an order of magnitude as waterbody size increased by {\textgreater} 3 orders of magnitude while CH4 fluxes showed large variability unrelated to lake size. By using a combination of Landsat-8 and GeoEye-1 images, we determined lakes cover 4\% of BZT and thus calculated overall C emissions from lentic waters to be 3.8 ± 0.65 Tg C yr−1 (99\% C-CO2, 1\% C-CH4), which is two times higher than the lateral riverine export. Large lakes dominated GHG emissions whereas small thaw ponds had a minor contribution to overall water surface area and GHG emissions. These data suggest that, if permafrost thaw in NE Europe results in disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, GHG emissions from lentic waters in this region may decrease.},
	language = {en},
	number = {S1},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography},
	author = {Zabelina, Svetlana A. and Shirokova, Liudmila S. and Klimov, Sergey I. and Chupakov, Artem V. and Lim, Artem G. and Polishchuk, Yuri M. and Polishchuk, Vladimir Y. and Bogdanov, Alexander N. and Muratov, Ildar N. and Guerin, Frederic and Karlsson, Jan and Pokrovsky, Oleg S.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11560},
	keywords = {\#nosource},
	pages = {S216--S230},
}

Emission of greenhouse gases (GHGs) from inland waters is recognized as highly important and an understudied part of the terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in subarctic regions that contain vast amounts of surface C in permafrost peatlands. This is especially true in NE European peatlands, located within sporadic to discontinuous permafrost zones which are highly vulnerable to thaw. Initial measurements of C emissions from lentic waters of the Bolshezemelskaya Tundra (BZT; 200,000 km2) demonstrated sizable CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds, and thermokarst lakes ranging from 0.5 × 106 to 5 × 106 m2 in size. CO2 fluxes decreased by an order of magnitude as waterbody size increased by \textgreater 3 orders of magnitude while CH4 fluxes showed large variability unrelated to lake size. By using a combination of Landsat-8 and GeoEye-1 images, we determined lakes cover 4% of BZT and thus calculated overall C emissions from lentic waters to be 3.8 ± 0.65 Tg C yr−1 (99% C-CO2, 1% C-CH4), which is two times higher than the lateral riverine export. Large lakes dominated GHG emissions whereas small thaw ponds had a minor contribution to overall water surface area and GHG emissions. These data suggest that, if permafrost thaw in NE Europe results in disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, GHG emissions from lentic waters in this region may decrease.

@article{wang_anthropogenic_2021,
	title = {Anthropogenic forcing of fish boldness and its impacts on ecosystem structure},
	volume = {27},
	copyright = {© 2020 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15473},
	doi = {10.1111/gcb.15473},
	abstract = {Modified fish behaviors in response to anthropogenic stressors, such as chemicals, microplastics, acoustic emissions and fisheries, are a debated driver of change in freshwater ecosystems and oceans. Our ability to judge the severity of observed behavioral responses is hampered by limited knowledge regarding how subtle behavior modifications in prey fish affect ecosystems. Here we show that anthropogenic stressors affecting fish boldness are not expected to cause population collapse, but rather elusive effects on fish length, population biomass, reproduction and ecosystem state shifts. We use a physiologically structured population model (three trophic levels), well fed with empirical data, to simulate how previously suggested alterations of fish boldness traits due to anthropogenic stressors affect ecosystem structure. Our results suggest that these stressors may cause ecosystem structure effects, such as skewed size distributions, reduced fish biomass and reduced reproduction success, by altering the foraging behavior of fish. However, the specific structure effects depend on where the boldness–shyness continuum change occurs and on the species-specific life stages. The model also highlights somewhat counterintuitive effects leading to possible extinction of predators when the foraging behavior of the prey is hampered. We conclude that anthropogenic forcing of fish behavior may be a hidden mechanism behind ecosystem structure changes in both freshwater and marine ecosystems.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Global Change Biology},
	author = {Wang, Wei and Xu, Nuo and Zhang, Lai and Andersen, Ken H. and Klaminder, Jonatan},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15473},
	keywords = {\#nosource, aquatic ecosystem, behavioral trait, boldness alteration, life history, regime shift, size-structured population model},
	pages = {1239--1249},
}

Modified fish behaviors in response to anthropogenic stressors, such as chemicals, microplastics, acoustic emissions and fisheries, are a debated driver of change in freshwater ecosystems and oceans. Our ability to judge the severity of observed behavioral responses is hampered by limited knowledge regarding how subtle behavior modifications in prey fish affect ecosystems. Here we show that anthropogenic stressors affecting fish boldness are not expected to cause population collapse, but rather elusive effects on fish length, population biomass, reproduction and ecosystem state shifts. We use a physiologically structured population model (three trophic levels), well fed with empirical data, to simulate how previously suggested alterations of fish boldness traits due to anthropogenic stressors affect ecosystem structure. Our results suggest that these stressors may cause ecosystem structure effects, such as skewed size distributions, reduced fish biomass and reduced reproduction success, by altering the foraging behavior of fish. However, the specific structure effects depend on where the boldness–shyness continuum change occurs and on the species-specific life stages. The model also highlights somewhat counterintuitive effects leading to possible extinction of predators when the foraging behavior of the prey is hampered. We conclude that anthropogenic forcing of fish behavior may be a hidden mechanism behind ecosystem structure changes in both freshwater and marine ecosystems.

@article{vachon_integrating_2021,
	title = {Integrating carbon emission, accumulation and transport in inland waters to understand their role in the global carbon cycle},
	volume = {27},
	copyright = {© 2020 The Authors. Global Change Biology published by John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15448},
	doi = {10.1111/gcb.15448},
	abstract = {Inland waters receive a significant quantity of carbon (C) from land. The fate of this C during transit, whether it is emitted to the atmosphere, accumulated in sediments or transported to the ocean, can considerably reshape the landscape C balance. However, these different fates of terrestrial C are not independent but are instead linked via several catchment and aquatic processes. Thus, according to mass conservation, any environmental change inducing a shift in a particular C fate should come at the expense of at least one other fate. Nonetheless, studies that have investigated C emission, accumulation and transport concertedly are scarce, resulting in fragmented knowledge of the role of inland waters in the global C cycle. Here, we propose a framework to understand how different C fates in aquatic systems are interlinked and covary under environmental changes. First, to explore how C fates are currently distributed in streams, rivers, reservoirs and lakes, we compiled data from the literature and show that ‘C fate allocation’ varies widely both within and among inland water systems types. Secondly, we developed a framework that integrates C fates in any inland water system by identifying the key processes underlying their linkages. Our framework places the partitioning between the different C forms, and how this is controlled by export from land, internal transformations and hydrology, as central to understanding C fate allocation. We argue that, by focusing on a single fate, studies could risk drawing misleading conclusions regarding how environmental changes will alter the role of inland waters in the global C cycle. Our framework thus allows us to holistically assess the consequences of such changes on coupled C fluxes, setting a foundation for understanding the contemporary and future fate of land-derived C in inland water systems.},
	language = {en},
	number = {4},
	urldate = {2024-03-27},
	journal = {Global Change Biology},
	author = {Vachon, Dominic and Sponseller, Ryan A. and Karlsson, Jan},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15448},
	keywords = {\#nosource, carbon cycle, conceptual framework, coupled fluxes, global change, inland waters, terrestrial carbon fate},
	pages = {719--727},
}

Inland waters receive a significant quantity of carbon (C) from land. The fate of this C during transit, whether it is emitted to the atmosphere, accumulated in sediments or transported to the ocean, can considerably reshape the landscape C balance. However, these different fates of terrestrial C are not independent but are instead linked via several catchment and aquatic processes. Thus, according to mass conservation, any environmental change inducing a shift in a particular C fate should come at the expense of at least one other fate. Nonetheless, studies that have investigated C emission, accumulation and transport concertedly are scarce, resulting in fragmented knowledge of the role of inland waters in the global C cycle. Here, we propose a framework to understand how different C fates in aquatic systems are interlinked and covary under environmental changes. First, to explore how C fates are currently distributed in streams, rivers, reservoirs and lakes, we compiled data from the literature and show that ‘C fate allocation’ varies widely both within and among inland water systems types. Secondly, we developed a framework that integrates C fates in any inland water system by identifying the key processes underlying their linkages. Our framework places the partitioning between the different C forms, and how this is controlled by export from land, internal transformations and hydrology, as central to understanding C fate allocation. We argue that, by focusing on a single fate, studies could risk drawing misleading conclusions regarding how environmental changes will alter the role of inland waters in the global C cycle. Our framework thus allows us to holistically assess the consequences of such changes on coupled C fluxes, setting a foundation for understanding the contemporary and future fate of land-derived C in inland water systems.

@article{rocher-ros_metabolism_2021,
	title = {Metabolism overrides photo-oxidation in {CO2} dynamics of {Arctic} permafrost streams},
	volume = {66},
	copyright = {© 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11564},
	doi = {10.1002/lno.11564},
	abstract = {Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Abiotic photo-oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 concentrations and the isotopic composition of dissolved inorganic C (δ13CDIC) at diel resolution in two Arctic streams, and coupled this with whole-system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO2 concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo-oxidation is the dominant source of CO2. Instead, the observed decrease in CO2 during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in δ13CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in δ13CDIC values, suggesting that metabolic estimates are partly masked by O2 consumption from photo-oxidation. Our results suggest that 6–12 mmol CO2-C m−2 d−1 may be generated from photo-oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo-oxidation rates for these Arctic streams, and accounted for 33–80\% of total CO2 evasion. Our results suggest that metabolic activity is the dominant process for CO2 production in Arctic streams. Thus, future aquatic CO2 emissions may depend on how biotic processes respond to the ongoing environmental change.},
	language = {en},
	number = {S1},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography},
	author = {Rocher-Ros, Gerard and Harms, Tamara K. and Sponseller, Ryan A. and Väisänen, Maria and Mörth, Carl-Magnus and Giesler, Reiner},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11564},
	keywords = {\#nosource},
	pages = {S169--S181},
}

Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Abiotic photo-oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 concentrations and the isotopic composition of dissolved inorganic C (δ13CDIC) at diel resolution in two Arctic streams, and coupled this with whole-system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO2 concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo-oxidation is the dominant source of CO2. Instead, the observed decrease in CO2 during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in δ13CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in δ13CDIC values, suggesting that metabolic estimates are partly masked by O2 consumption from photo-oxidation. Our results suggest that 6–12 mmol CO2-C m−2 d−1 may be generated from photo-oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo-oxidation rates for these Arctic streams, and accounted for 33–80% of total CO2 evasion. Our results suggest that metabolic activity is the dominant process for CO2 production in Arctic streams. Thus, future aquatic CO2 emissions may depend on how biotic processes respond to the ongoing environmental change.

@article{myrstener_nutrients_2021,
	title = {Nutrients influence seasonal metabolic patterns and total productivity of {Arctic} streams},
	volume = {66},
	copyright = {© 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11614},
	doi = {10.1002/lno.11614},
	abstract = {The seasonality of gross primary production (GPP) in streams is driven by multiple physical and chemical factors, yet incident light is often thought to be most important. In Arctic tundra streams, however, light is available in saturating amounts throughout the summer, but sharp declines in nutrient supply during the terrestrial growing season may constrain aquatic productivity. Given the opposing seasonality of these drivers, we hypothesized that “shoulder seasons”—spring and autumn—represent critical time windows when light and nutrients align to optimize rates of stream productivity in the Arctic. To test this, we measured annual patterns of GPP and biofilm accumulation in eight streams in Arctic Sweden. We found that the aquatic growing season length differed by 4 months across streams and was determined largely by the timing of ice-off in spring. During the growing season, temporal variability in GPP for nitrogen (N) poor streams was correlated with inorganic N concentration, while in more N-rich streams GPP was instead linked to changes in phosphorus and light. Annual GPP varied ninefold among streams and was enhanced by N availability, the length of ice-free period, and low flood frequency. Finally, network scale estimates of GPP highlight the overall significance of the shoulder seasons, which accounted for 48\% of annual productivity. We suggest that the timing of ice off and nutrient supply from land interact to regulate the annual metabolic regimes of nutrient poor, Arctic streams, leading to unexpected peaks in productivity that are offset from the terrestrial growing season.},
	language = {en},
	number = {S1},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Myrstener, Maria and Gómez-Gener, Lluís and Rocher-Ros, Gerard and Giesler, Reiner and Sponseller, Ryan A.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11614},
	keywords = {\#nosource},
	pages = {S182--S196},
}

The seasonality of gross primary production (GPP) in streams is driven by multiple physical and chemical factors, yet incident light is often thought to be most important. In Arctic tundra streams, however, light is available in saturating amounts throughout the summer, but sharp declines in nutrient supply during the terrestrial growing season may constrain aquatic productivity. Given the opposing seasonality of these drivers, we hypothesized that “shoulder seasons”—spring and autumn—represent critical time windows when light and nutrients align to optimize rates of stream productivity in the Arctic. To test this, we measured annual patterns of GPP and biofilm accumulation in eight streams in Arctic Sweden. We found that the aquatic growing season length differed by 4 months across streams and was determined largely by the timing of ice-off in spring. During the growing season, temporal variability in GPP for nitrogen (N) poor streams was correlated with inorganic N concentration, while in more N-rich streams GPP was instead linked to changes in phosphorus and light. Annual GPP varied ninefold among streams and was enhanced by N availability, the length of ice-free period, and low flood frequency. Finally, network scale estimates of GPP highlight the overall significance of the shoulder seasons, which accounted for 48% of annual productivity. We suggest that the timing of ice off and nutrient supply from land interact to regulate the annual metabolic regimes of nutrient poor, Arctic streams, leading to unexpected peaks in productivity that are offset from the terrestrial growing season.

@article{macdougall_comparison_2021,
	title = {Comparison of the distribution and phenology of {Arctic} {Mountain} plants between the early 20th and 21st centuries},
	volume = {27},
	copyright = {© 2021 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15767},
	doi = {10.1111/gcb.15767},
	abstract = {Arctic plants are adapted to climatic variability, but their long-term responses to warming remain unclear. Responses may occur by range shifts, phenological adjustments in growth and reproduction, or both. Here, we compare distribution and phenology of 83 arctic and boreal mountain species, sampled identically in the early 20th (1917–1919) and 21st centuries (2017–2018) from a region of northern Sweden that has warmed significantly. We test two compensatory hypotheses to high-latitude warming—upward shifts in distribution, and earlier or extended growth and reproduction. For distribution, we show dramatic upward migration by 69\% of species, averaging 6.1 m per decade, especially boreal woodland taxa whose upward expansion has reduced arctic montane habitat by 30\%. Twenty percent of summit species showed distributional shifts but downward, especially moisture-associated snowbed flora. For phenology, we detected wide inter-annual variability in the onset of leafing and flowering in both eras. However, there was no detectable change in growing-season length, relating to two mechanisms. First, plot-level snow melt data starting in 1917 demonstrated that melt date, rather than vernal temperatures, better predicts plant emergence, with snow melt influenced by warmer years having greater snowfall—warmer springs did not always result in earlier emergence because snowbeds can persist longer. Second, the onset of reproductive senescence between eras was similar, even when plant emergence was earlier by a month, possibly due to intensified summer heat stress or hard-wired ‘canalization’ where senescence occurs regardless of summer temperature. Migrations in this system have possibly buffered arctic species against displacement by boreal expansion and warming, but ongoing temperature increases, woody plant invasion, and a potential lack of flexibility in timing of senescence may foreshadow challenges.},
	language = {en},
	number = {20},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {MacDougall, Andrew S. and Caplat, Paul and Olofsson, Johan and Siewert, Matthias B. and Bonner, Colin and Esch, Ellen and Lessard-Therrien, Malie and Rosenzweig, Hannah and Schäfer, Anne-Kathrin and Raker, Pia and Ridha, Hassan and Bolmgren, Kjell and Fries, Thore C. E. and Larson, Keith},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15767},
	keywords = {\#nosource, arctic flora, climate change, historical data, migration, mountain, phenology, resiliency},
	pages = {5070--5083},
}

Arctic plants are adapted to climatic variability, but their long-term responses to warming remain unclear. Responses may occur by range shifts, phenological adjustments in growth and reproduction, or both. Here, we compare distribution and phenology of 83 arctic and boreal mountain species, sampled identically in the early 20th (1917–1919) and 21st centuries (2017–2018) from a region of northern Sweden that has warmed significantly. We test two compensatory hypotheses to high-latitude warming—upward shifts in distribution, and earlier or extended growth and reproduction. For distribution, we show dramatic upward migration by 69% of species, averaging 6.1 m per decade, especially boreal woodland taxa whose upward expansion has reduced arctic montane habitat by 30%. Twenty percent of summit species showed distributional shifts but downward, especially moisture-associated snowbed flora. For phenology, we detected wide inter-annual variability in the onset of leafing and flowering in both eras. However, there was no detectable change in growing-season length, relating to two mechanisms. First, plot-level snow melt data starting in 1917 demonstrated that melt date, rather than vernal temperatures, better predicts plant emergence, with snow melt influenced by warmer years having greater snowfall—warmer springs did not always result in earlier emergence because snowbeds can persist longer. Second, the onset of reproductive senescence between eras was similar, even when plant emergence was earlier by a month, possibly due to intensified summer heat stress or hard-wired ‘canalization’ where senescence occurs regardless of summer temperature. Migrations in this system have possibly buffered arctic species against displacement by boreal expansion and warming, but ongoing temperature increases, woody plant invasion, and a potential lack of flexibility in timing of senescence may foreshadow challenges.

@article{lau_lowered_2021,
	title = {Lowered nutritional quality of plankton caused by global environmental changes},
	volume = {27},
	copyright = {© 2021 The Authors. Global Change Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15887},
	doi = {10.1111/gcb.15887},
	abstract = {Global environmental changes are causing widespread nutrient depletion, declines in the ratio of dissolved inorganic nitrogen (N) to total phosphorus (DIN:TP), and increases in both water temperature and terrestrial colored dissolved organic carbon (DOC) concentration (browning) in high-latitude northern lakes. Declining lake DIN:TP, warming, and browning alter the nutrient limitation regime and biomass of phytoplankton, but how these stressors together affect the nutritional quality in terms of polyunsaturated fatty acid (PUFA) contents of the pelagic food web components remains unknown. We assessed the fatty acid compositions of seston and zooplankton in 33 lakes across south-to-north and boreal-to-subarctic gradients in Sweden. Data showed higher lake DIN:TP in the south than in the north, and that boreal lakes were warmer and browner than subarctic lakes. Lake DIN:TP strongly affected the PUFA contents—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—in seston, calanoids, and copepods (as a group), but not in cladocerans. The EPA+DHA contents increased by 123\% in seston, 197\% in calanoids, and 230\% in copepods across a lake molar DIN:TP gradient from 0.17 to 14.53, indicating lower seston and copepod nutritional quality in the more N-limited lakes (those with lower DIN:TP). Water temperature affected EPA+DHA contents of zooplankton, especially cladocerans, but not seston. Cladoceran EPA+DHA contents were reduced by ca. 6\% for every 1°C increase in surface water. Also, the EPA, DHA, or EPA+DHA contents of Bosmina, cyclopoids, and copepods increased in lakes with higher DOC concentrations or aromaticity. Our findings indicate that zooplankton food quality for higher consumers will decrease with warming alone (for cladocerans) or in combination with declining lake DIN:TP (for copepods), but impacts of these stressors are moderated by lake browning. Global environmental changes that drive northern lakes toward more N-limited, warmer, and browner conditions will reduce PUFA availability and nutritional quality of the pelagic food web components.},
	language = {en},
	number = {23},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Lau, Danny C. P. and Jonsson, Anders and Isles, Peter D. F. and Creed, Irena F. and Bergström, Ann‑Kristin},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15887},
	keywords = {\#nosource, N:P stoichiometry, boreal lakes, dissolved organic carbon, fatty acids, nitrogen deposition, phytoplankton, seston, subarctic lakes, warming, zooplankton},
	pages = {6294--6306},
}

Global environmental changes are causing widespread nutrient depletion, declines in the ratio of dissolved inorganic nitrogen (N) to total phosphorus (DIN:TP), and increases in both water temperature and terrestrial colored dissolved organic carbon (DOC) concentration (browning) in high-latitude northern lakes. Declining lake DIN:TP, warming, and browning alter the nutrient limitation regime and biomass of phytoplankton, but how these stressors together affect the nutritional quality in terms of polyunsaturated fatty acid (PUFA) contents of the pelagic food web components remains unknown. We assessed the fatty acid compositions of seston and zooplankton in 33 lakes across south-to-north and boreal-to-subarctic gradients in Sweden. Data showed higher lake DIN:TP in the south than in the north, and that boreal lakes were warmer and browner than subarctic lakes. Lake DIN:TP strongly affected the PUFA contents—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—in seston, calanoids, and copepods (as a group), but not in cladocerans. The EPA+DHA contents increased by 123% in seston, 197% in calanoids, and 230% in copepods across a lake molar DIN:TP gradient from 0.17 to 14.53, indicating lower seston and copepod nutritional quality in the more N-limited lakes (those with lower DIN:TP). Water temperature affected EPA+DHA contents of zooplankton, especially cladocerans, but not seston. Cladoceran EPA+DHA contents were reduced by ca. 6% for every 1°C increase in surface water. Also, the EPA, DHA, or EPA+DHA contents of Bosmina, cyclopoids, and copepods increased in lakes with higher DOC concentrations or aromaticity. Our findings indicate that zooplankton food quality for higher consumers will decrease with warming alone (for cladocerans) or in combination with declining lake DIN:TP (for copepods), but impacts of these stressors are moderated by lake browning. Global environmental changes that drive northern lakes toward more N-limited, warmer, and browner conditions will reduce PUFA availability and nutritional quality of the pelagic food web components.

@article{isles_trade-offs_2021,
	title = {Trade-offs {Between} {Light} and {Nutrient} {Availability} {Across} {Gradients} of {Dissolved} {Organic} {Carbon} {Lead} to {Spatially} and {Temporally} {Variable} {Responses} of {Lake} {Phytoplankton} {Biomass} to {Browning}},
	volume = {24},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-021-00619-7},
	doi = {10.1007/s10021-021-00619-7},
	abstract = {Northern lakes are experiencing widespread increases in dissolved organic carbon (DOC) that are likely to lead to changes in pelagic phytoplankton biomass. Pelagic phytoplankton biomass responds to trade-offs between light and nutrient availability. However, the influence of DOC light absorbing properties and carbon–nutrient stoichiometry on phytoplankton biomass across seasonal or spatial gradients has not been assessed. Here, we analyzed data from almost 5000 lakes to examine how the carbon–phytoplankton biomass relationship is influenced by seasonal changes in light availability, DOC light absorbing properties (carbon-specific visual absorbance, SVA420), and DOC–nutrient [total nitrogen (TN) and total phosphorus (TP)] stoichiometry, using TOC as a proxy for DOC. We found evidence for trade-offs between light and nutrient availability in the relationship between DOC and phytoplankton biomass [chlorophyll (chl)-a], with the shape of the relationship varying with season. A clear unimodal relationship was found only in the fall, particularly in the subsets of lakes with the highest TOC:TP. Observed trends of increasing TOC:TP and decreasing TOC:TN suggest that the effects of future browning will be contingent on future changes in carbon–nutrient stoichiometry. If browning continues, phytoplankton biomass will likely increase in most northern lakes, with increases of up to 76\% for a 1.7 mg L−1 increase in DOC expected in subarctic regions, where DOC, SVA420, DOC:TN, and DOC:TP are all low. In boreal regions with higher DOC and higher SVA420, and thus lower light availability, lakes may experience only moderate increases or even decreases in phytoplankton biomass with future browning.},
	language = {en},
	number = {8},
	urldate = {2024-03-26},
	journal = {Ecosystems},
	author = {Isles, Peter D. F. and Creed, Irena F. and Jonsson, Anders and Bergström, Ann-Kristin},
	month = dec,
	year = {2021},
	keywords = {\#nosource, Boreal, Browning, Chlorophyll-a, DOC, DOC:TN, DOC:TP, Lake, Stoichiometry, Subarctic, Sweden},
	pages = {1837--1852},
}

Northern lakes are experiencing widespread increases in dissolved organic carbon (DOC) that are likely to lead to changes in pelagic phytoplankton biomass. Pelagic phytoplankton biomass responds to trade-offs between light and nutrient availability. However, the influence of DOC light absorbing properties and carbon–nutrient stoichiometry on phytoplankton biomass across seasonal or spatial gradients has not been assessed. Here, we analyzed data from almost 5000 lakes to examine how the carbon–phytoplankton biomass relationship is influenced by seasonal changes in light availability, DOC light absorbing properties (carbon-specific visual absorbance, SVA420), and DOC–nutrient [total nitrogen (TN) and total phosphorus (TP)] stoichiometry, using TOC as a proxy for DOC. We found evidence for trade-offs between light and nutrient availability in the relationship between DOC and phytoplankton biomass [chlorophyll (chl)-a], with the shape of the relationship varying with season. A clear unimodal relationship was found only in the fall, particularly in the subsets of lakes with the highest TOC:TP. Observed trends of increasing TOC:TP and decreasing TOC:TN suggest that the effects of future browning will be contingent on future changes in carbon–nutrient stoichiometry. If browning continues, phytoplankton biomass will likely increase in most northern lakes, with increases of up to 76% for a 1.7 mg L−1 increase in DOC expected in subarctic regions, where DOC, SVA420, DOC:TN, and DOC:TP are all low. In boreal regions with higher DOC and higher SVA420, and thus lower light availability, lakes may experience only moderate increases or even decreases in phytoplankton biomass with future browning.

@article{hamdan_experimental_2021,
	title = {An experimental test of climate change effects in northern lakes: {Increasing} allochthonous organic matter and warming alters autumn primary production},
	volume = {66},
	copyright = {© 2021 The Authors. Freshwater Biology published by John Wiley \& Sons Ltd.},
	issn = {1365-2427},
	shorttitle = {An experimental test of climate change effects in northern lakes},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.13679},
	doi = {10.1111/fwb.13679},
	abstract = {Climate changes are predicted to influence gross primary production (GPP) of lakes directly through warming and indirectly through increased loads of allochthonous coloured dissolved organic matter (cDOM) from surrounding landscapes. However, few studies have investigated this combined effect. Here we tested the effects of warming (elevated 3℃) and cDOM input (three levels of humic river water addition) on GPP in autumn (2 months including open water and ice-covered periods) in experimental pond ecosystems. The cDOM input decreased whole-ecosystem GPP at natural temperature conditions mainly as a result of lower benthic GPP not fully counteracted by an increase in pelagic GPP, while warming increased whole-ecosystem GPP due to a positive response of mainly pelagic GPP at all levels of cDOM input. Warming delayed autumn ice cover formation by 2 weeks but did not affect light availability in the water column compared to ambient ice-covered treatments. Gross primary production during this period was still affected by warming and cDOM. The results stress the importance of accounting for multiple climate drivers and habitats when predicting lake GPP responses to climate change. We conclude that climate change may shift whole-ecosystem GPP through different responses of habitat-specific GPP to increasing cDOM inputs and warming.},
	language = {en},
	number = {5},
	urldate = {2024-03-26},
	journal = {Freshwater Biology},
	author = {Hamdan, Mohammed and Byström, Pär and Hotchkiss, Erin R. and Al-Haidarey, Mohammed J. and Karlsson, Jan},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.13679},
	keywords = {\#nosource, brownification, habitat-specific, limitation, rising temperature, whole productivity},
	pages = {815--825},
}

Climate changes are predicted to influence gross primary production (GPP) of lakes directly through warming and indirectly through increased loads of allochthonous coloured dissolved organic matter (cDOM) from surrounding landscapes. However, few studies have investigated this combined effect. Here we tested the effects of warming (elevated 3℃) and cDOM input (three levels of humic river water addition) on GPP in autumn (2 months including open water and ice-covered periods) in experimental pond ecosystems. The cDOM input decreased whole-ecosystem GPP at natural temperature conditions mainly as a result of lower benthic GPP not fully counteracted by an increase in pelagic GPP, while warming increased whole-ecosystem GPP due to a positive response of mainly pelagic GPP at all levels of cDOM input. Warming delayed autumn ice cover formation by 2 weeks but did not affect light availability in the water column compared to ambient ice-covered treatments. Gross primary production during this period was still affected by warming and cDOM. The results stress the importance of accounting for multiple climate drivers and habitats when predicting lake GPP responses to climate change. We conclude that climate change may shift whole-ecosystem GPP through different responses of habitat-specific GPP to increasing cDOM inputs and warming.

@article{gibson_pulse_2021,
	title = {Pulse grazing by reindeer ({Rangifer} tarandus) can increase the phylogenetic diversity of vascular plant communities in the {Fennoscandian} tundra},
	volume = {11},
	copyright = {© 2021 The Authors. Ecology and Evolution published by John Wiley \& Sons Ltd.},
	issn = {2045-7758},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ece3.8131},
	doi = {10.1002/ece3.8131},
	abstract = {Herbivore grazing is an important determinant of plant community assemblages. Thus, it is essential to understand its impact to direct conservation efforts in regions where herbivores are managed. While the impacts of reindeer (Rangifer tarandus) grazing on plant biodiversity and community composition in the Fennoscandian tundra are well studied, the impact of reindeer grazing on phylogenetic community structure is not. We used data from a multiyear quasi-experimental study in northern Fennoscandia to analyze the effect of reindeer grazing on plant community diversity including its phylogenetic structure. Our study design used a permanent fence constructed in the 1960s and temporary fences constructed along the permanent fence to expose plant communities to three different grazing regimes: light (almost never grazed), pulse (grazed every other year), and press (chronic grazing for over 40 years). Similar to previous studies on low productivity ecosystems in this region, the species richness and evenness of plant communities with pulse and press grazing did not differ from communities with light grazing. Also consistent with previous studies in this region, we observed a transition from shrub-dominated communities with light grazing to graminoid-dominated communities with pulse and press grazing. Interestingly, communities with pulse, but not press, grazing were more phylogenetically dispersed than communities with light grazing. If grazing pulses can increase the phylogenetic diversity of plant communities, our result suggests changes in reindeer management allowing for pulses of grazing to increase phylogenetic diversity of plant communities.},
	language = {en},
	number = {21},
	urldate = {2024-03-26},
	journal = {Ecology and Evolution},
	author = {Gibson, Kate and Olofsson, Johan and Mooers, Arne Ø. and Monroe, Melanie J.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.8131},
	keywords = {\#nosource, biodiversity, community structure, grazing, herbivore, phylogenetic diversity},
	pages = {14598--14614},
}

Herbivore grazing is an important determinant of plant community assemblages. Thus, it is essential to understand its impact to direct conservation efforts in regions where herbivores are managed. While the impacts of reindeer (Rangifer tarandus) grazing on plant biodiversity and community composition in the Fennoscandian tundra are well studied, the impact of reindeer grazing on phylogenetic community structure is not. We used data from a multiyear quasi-experimental study in northern Fennoscandia to analyze the effect of reindeer grazing on plant community diversity including its phylogenetic structure. Our study design used a permanent fence constructed in the 1960s and temporary fences constructed along the permanent fence to expose plant communities to three different grazing regimes: light (almost never grazed), pulse (grazed every other year), and press (chronic grazing for over 40 years). Similar to previous studies on low productivity ecosystems in this region, the species richness and evenness of plant communities with pulse and press grazing did not differ from communities with light grazing. Also consistent with previous studies in this region, we observed a transition from shrub-dominated communities with light grazing to graminoid-dominated communities with pulse and press grazing. Interestingly, communities with pulse, but not press, grazing were more phylogenetically dispersed than communities with light grazing. If grazing pulses can increase the phylogenetic diversity of plant communities, our result suggests changes in reindeer management allowing for pulses of grazing to increase phylogenetic diversity of plant communities.

@article{bergstrom_effects_2021,
	title = {Effects of nitrogen enrichment on zooplankton biomass and {N}:{P} recycling ratios across a {DOC} gradient in northern-latitude lakes},
	volume = {848},
	issn = {1573-5117},
	shorttitle = {Effects of nitrogen enrichment on zooplankton biomass and {N}},
	url = {https://doi.org/10.1007/s10750-021-04689-5},
	doi = {10.1007/s10750-021-04689-5},
	abstract = {We used data from whole-lake studies to assess how changes in food quantity (phytoplankton biomass) and quality (phytoplankton community composition, seston C:P and N:P) with N fertilization affect zooplankton biomass, community composition and C:N:P stoichiometry, and their N:P recycling ratio along a gradient in lake DOC concentrations. We found that despite major differences in phytoplankton biomass with DOC (unimodal distributions, especially with N fertilization), no major differences in zooplankton biomass were detectable. Instead, phytoplankton to zooplankton biomass ratios were high, especially at intermediate DOC and after N fertilization, implying low trophic transfer efficiencies. An explanation for the observed low phytoplankton resource use, and biomass responses in zooplankton, was dominance of colony forming chlorophytes of reduced edibility at intermediate lake DOC, combined with reduced phytoplankton mineral quality (enhanced seston N:P) with N fertilization. N fertilization, however, increased zooplankton N:P recycling ratios, with largest impact at low DOC where phytoplankton benefitted from light sufficiently to cause enhanced seston N:P. Our results suggest that although N enrichment and increased phytoplankton biomass do not necessarily increase zooplankton biomass, bottom-up effects may still impact zooplankton and their N:P recycling ratio through promotion of phytoplankton species of low edibility and altered mineral quality.},
	language = {en},
	number = {21},
	urldate = {2024-03-26},
	journal = {Hydrobiologia},
	author = {Bergström, A.-K. and Deininger, A. and Jonsson, A. and Karlsson, J. and Vrede, T.},
	month = dec,
	year = {2021},
	keywords = {\#nosource, Dissolved organic carbon, Food quantity-quality, Light, Nitrogen, Pelagic food web, Phosphorus},
	pages = {4991--5010},
}

We used data from whole-lake studies to assess how changes in food quantity (phytoplankton biomass) and quality (phytoplankton community composition, seston C:P and N:P) with N fertilization affect zooplankton biomass, community composition and C:N:P stoichiometry, and their N:P recycling ratio along a gradient in lake DOC concentrations. We found that despite major differences in phytoplankton biomass with DOC (unimodal distributions, especially with N fertilization), no major differences in zooplankton biomass were detectable. Instead, phytoplankton to zooplankton biomass ratios were high, especially at intermediate DOC and after N fertilization, implying low trophic transfer efficiencies. An explanation for the observed low phytoplankton resource use, and biomass responses in zooplankton, was dominance of colony forming chlorophytes of reduced edibility at intermediate lake DOC, combined with reduced phytoplankton mineral quality (enhanced seston N:P) with N fertilization. N fertilization, however, increased zooplankton N:P recycling ratios, with largest impact at low DOC where phytoplankton benefitted from light sufficiently to cause enhanced seston N:P. Our results suggest that although N enrichment and increased phytoplankton biomass do not necessarily increase zooplankton biomass, bottom-up effects may still impact zooplankton and their N:P recycling ratio through promotion of phytoplankton species of low edibility and altered mineral quality.

@phdthesis{hamdan_effects_2021,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Effects of temperature and terrestrial carbon on primary production in lake ecosystems},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-182526},
	abstract = {Climate warming is predicted to affect northern lake food webs in two ways: (1)directly via changes in water temperature and ice conditions, and (2) indirectlyvia changes in catchment characteristi ...},
	language = {eng},
	urldate = {2023-07-25},
	school = {Umeå University},
	author = {Hamdan, Mohammed},
	collaborator = {Karlsson, Jan and Byström, Pär and Hotchkiss, Erin R.},
	year = {2021},
	note = {Publisher: Umeå University},
	keywords = {⛔ No DOI found},
}

Climate warming is predicted to affect northern lake food webs in two ways: (1)directly via changes in water temperature and ice conditions, and (2) indirectlyvia changes in catchment characteristi ...

@incollection{kullman_review_2021,
	title = {A {Review} of {Abisko} {Case} {Study}: {Recent} and {Past} {Trees} an {Climates} at the {Arctic}/{Alpine} {Margin} in {Swedish} {Lapland}},
	volume = {2},
	isbn = {978-93-90768-63-9},
	abstract = {For about a century, Abisko Scientific Research Station in northern Swedish Lapland has served as a logistic base for high-quality geoecological research in subalpine/subarctic environments. In recent years, and driven by the prospect of alleged man-made global warming, much of the scientific focus has been on dynamics of the treeline ecotone. In this context, field observations, analyses and interpretations emanating from research carried out in the Abisko region are discussed in perspective of recent observations and analyses. Local mountain birch (Betula pubescens ssp. czerepanovii) treeline rise by maximum 230 m during the past 100 years conforms quantitatively to data obtained further south in the Scandes. This broad-scale inter-regional coincidence indicates that a common operative agent has been responsible. The most likely candidate is recorded secular climate warming by 2.5°C. This contention is further supported by age structure analysis in the birch treeline advance zone, indicating that the vegetative initiation of new trees peaked during the warm 1930s, when reindeer number were high and reached a nadir during the relatively cold 1960s and 1970s, coincident with smaller reindeer herds. These data suggest, contrary to previous hypotheses, stating that, relative to climate change, intensity of reindeer browsing has been of minor importance for birch treeline dynamics. The upper limit of closed stands of mountain birch and pine have shifted relatively insignificantly in elevational position during the predominantly warm past 100 years. Over the same period or longer, common aspen (Populus tremula) has frequently occurred as low-growing krummholz (stunted growth forms) over the entire mountain birch region. During the warm 1930s and just like birch, rapid height increment was initiated and has continued up to the present day. Thereby, many individuals have attained tree-sized in recent decades. Accordingly, aspen (Populus tremula) has, presumably in response to climate warming, become a more conspicuous element in the mountain birch forest. The current analyses refute prior claims that aspen regeneration is accomplished by seed regeneration rather than phenotypic adjustment of old-growth creeping individuals. Picea abies and Larix sp. are recorded as new species in the Abisko area. In accordance with prior analyses in other parts of the Scandes, megafossil data show that the treelines of Scots pine (Pinus sylvestris), mountain birch (Betula pubescens ssp. czerepanovii) and grey alder (Alnus incana) peaked in the early Holocene. Based on the elevational difference between early Holocene and present treeline positions (adjusted for 100 m land uplift) it may be inferred that the summer temperatures exceeded those of the last few decades by about 3.0°C. This study challenges recent proposals that aspen is currently spreading upslope and westwards in the birch forest belt by seed establishment of new individuals. In response to recent warming they have attained tree size and have become a more conspicuous element of the landscape.},
	booktitle = {Challenging {Issues} on {Environment} and {Earth} {Science}},
	publisher = {Book Publisher International},
	author = {Kullman, Leif},
	editor = {Turkman, Mustafa},
	month = mar,
	year = {2021},
	doi = {10.9734/bpi/ciees/v2/7576D},
	pages = {1--25},
}

For about a century, Abisko Scientific Research Station in northern Swedish Lapland has served as a logistic base for high-quality geoecological research in subalpine/subarctic environments. In recent years, and driven by the prospect of alleged man-made global warming, much of the scientific focus has been on dynamics of the treeline ecotone. In this context, field observations, analyses and interpretations emanating from research carried out in the Abisko region are discussed in perspective of recent observations and analyses. Local mountain birch (Betula pubescens ssp. czerepanovii) treeline rise by maximum 230 m during the past 100 years conforms quantitatively to data obtained further south in the Scandes. This broad-scale inter-regional coincidence indicates that a common operative agent has been responsible. The most likely candidate is recorded secular climate warming by 2.5°C. This contention is further supported by age structure analysis in the birch treeline advance zone, indicating that the vegetative initiation of new trees peaked during the warm 1930s, when reindeer number were high and reached a nadir during the relatively cold 1960s and 1970s, coincident with smaller reindeer herds. These data suggest, contrary to previous hypotheses, stating that, relative to climate change, intensity of reindeer browsing has been of minor importance for birch treeline dynamics. The upper limit of closed stands of mountain birch and pine have shifted relatively insignificantly in elevational position during the predominantly warm past 100 years. Over the same period or longer, common aspen (Populus tremula) has frequently occurred as low-growing krummholz (stunted growth forms) over the entire mountain birch region. During the warm 1930s and just like birch, rapid height increment was initiated and has continued up to the present day. Thereby, many individuals have attained tree-sized in recent decades. Accordingly, aspen (Populus tremula) has, presumably in response to climate warming, become a more conspicuous element in the mountain birch forest. The current analyses refute prior claims that aspen regeneration is accomplished by seed regeneration rather than phenotypic adjustment of old-growth creeping individuals. Picea abies and Larix sp. are recorded as new species in the Abisko area. In accordance with prior analyses in other parts of the Scandes, megafossil data show that the treelines of Scots pine (Pinus sylvestris), mountain birch (Betula pubescens ssp. czerepanovii) and grey alder (Alnus incana) peaked in the early Holocene. Based on the elevational difference between early Holocene and present treeline positions (adjusted for 100 m land uplift) it may be inferred that the summer temperatures exceeded those of the last few decades by about 3.0°C. This study challenges recent proposals that aspen is currently spreading upslope and westwards in the birch forest belt by seed establishment of new individuals. In response to recent warming they have attained tree size and have become a more conspicuous element of the landscape.

@article{azevedo_predicting_2021,
	title = {Predicting {Soil} {Respiration} from {Plant} {Productivity} ({NDVI}) in a {Sub}-{Arctic} {Tundra} {Ecosystem}},
	volume = {13},
	doi = {10.3390/rs13132571},
	journal = {Remote Sensing},
	author = {Azevedo, Olivia and Parker, Thomas and Siewert, Matthias and Subke, Jens-Arne},
	month = jun,
	year = {2021},
	pages = {2571},
}

@article{cruz-paredes_can_2021,
	title = {Can moisture affect temperature dependences of microbial growth and respiration?},
	volume = {156},
	issn = {0038-0717},
	url = {https://www.sciencedirect.com/science/article/pii/S003807172100095X},
	doi = {10.1016/j.soilbio.2021.108223},
	abstract = {It is of great importance to understand how terrestrial ecosystems will respond to global changes. However, most experimental approaches have focused on single factors. In natural systems, moisture and temperature often change simultaneously, and they can interact and shape microbial responses. Even though soil moisture and temperature are very important factors controlling microbial activity, there is disagreement on the dependence of microbial rates on temperature and moisture as well as their sensitivity when both variables change simultaneously. Here we created a moisture gradient and determined high resolution intrinsic temperature dependences for bacterial and fungal growth rates as well as respiration rates. We found that microbial rates decreased with lower moisture and increased with higher temperatures until optimum values. Additionally, we found independence between temperature and moisture as rate modifiers. We also found that temperature sensitivities (Q10) for microbial growth and respiration were not affected by changes in moisture. This provided an experimental framework to validate assumptions of temperature and moisture rate modifiers used in ecosystem and global cycling models (GCMs).},
	journal = {Soil Biology and Biochemistry},
	author = {Cruz-Paredes, Carla and Tájmel, Dániel and Rousk, Johannes},
	month = may,
	year = {2021},
	keywords = {Microbial growth, Moisture, Soil respiration, Temperature dependence},
	pages = {108223},
}

It is of great importance to understand how terrestrial ecosystems will respond to global changes. However, most experimental approaches have focused on single factors. In natural systems, moisture and temperature often change simultaneously, and they can interact and shape microbial responses. Even though soil moisture and temperature are very important factors controlling microbial activity, there is disagreement on the dependence of microbial rates on temperature and moisture as well as their sensitivity when both variables change simultaneously. Here we created a moisture gradient and determined high resolution intrinsic temperature dependences for bacterial and fungal growth rates as well as respiration rates. We found that microbial rates decreased with lower moisture and increased with higher temperatures until optimum values. Additionally, we found independence between temperature and moisture as rate modifiers. We also found that temperature sensitivities (Q10) for microbial growth and respiration were not affected by changes in moisture. This provided an experimental framework to validate assumptions of temperature and moisture rate modifiers used in ecosystem and global cycling models (GCMs).

@article{baggesen_phenological_2021,
	title = {Phenological stage of tundra vegetation controls bidirectional exchange of {BVOCs} in a climate change experiment on a subarctic heath},
	volume = {27},
	issn = {1354-1013},
	url = {https://doi.org/10.1111/gcb.15596},
	doi = {10.1111/gcb.15596},
	abstract = {Abstract Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR?ToF?MS). The warming treatment increased monoterpene and isoprene emissions by ≈50\%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by {\textasciitilde}50\%?75\%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.},
	number = {12},
	urldate = {2023-07-22},
	journal = {Global Change Biology},
	author = {Baggesen, Nanna and Li, Tao and Seco, Roger and Holst, Thomas and Michelsen, Anders and Rinnan, Riikka},
	month = jun,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Arctic, BVOC, climate change, methanol, phenology, plant volatiles, terpenoids, tundra},
	pages = {2928--2944},
}

Abstract Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR?ToF?MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%?75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.

@article{clemmensen_tipping_2021,
	title = {A tipping point in carbon storage when forest expands into tundra is related to mycorrhizal recycling of nitrogen},
	volume = {24},
	issn = {1461-023X},
	url = {https://doi.org/10.1111/ele.13735},
	doi = {10.1111/ele.13735},
	abstract = {Abstract Tundra ecosystems are global belowground sinks for atmospheric CO2. Ongoing warming-induced encroachment by shrubs and trees risks turning this sink into a CO2 source, resulting in a positive feedback on climate warming. To advance mechanistic understanding of how shifts in mycorrhizal types affect long-term carbon (C) and nitrogen (N) stocks, we studied small-scale soil depth profiles of fungal communities and C?N dynamics across a subarctic-alpine forest-heath vegetation gradient. Belowground organic stocks decreased abruptly at the transition from heath to forest, linked to the presence of certain tree-associated ectomycorrhizal fungi that contribute to decomposition when mining N from organic matter. In contrast, ericoid mycorrhizal plants and fungi were associated with organic matter accumulation and slow decomposition. If climatic controls on arctic-alpine forest lines are relaxed, increased decomposition will likely outbalance increased plant productivity, decreasing the overall C sink capacity of displaced tundra.},
	number = {6},
	urldate = {2023-07-22},
	journal = {Ecology Letters},
	author = {Clemmensen, Karina Engelbrecht and Durling, Mikael Brandström and Michelsen, Anders and Hallin, Sara and Finlay, Roger D. and Lindahl, Björn D.},
	month = jun,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Arctic warming, carbon sequestration, decomposition, functional genes, meta-barcoding, mycorrhizal type, nitrogen cycling, soil fungal communities, stable isotopes, treeline ecotone},
	pages = {1193--1204},
}

Abstract Tundra ecosystems are global belowground sinks for atmospheric CO2. Ongoing warming-induced encroachment by shrubs and trees risks turning this sink into a CO2 source, resulting in a positive feedback on climate warming. To advance mechanistic understanding of how shifts in mycorrhizal types affect long-term carbon (C) and nitrogen (N) stocks, we studied small-scale soil depth profiles of fungal communities and C?N dynamics across a subarctic-alpine forest-heath vegetation gradient. Belowground organic stocks decreased abruptly at the transition from heath to forest, linked to the presence of certain tree-associated ectomycorrhizal fungi that contribute to decomposition when mining N from organic matter. In contrast, ericoid mycorrhizal plants and fungi were associated with organic matter accumulation and slow decomposition. If climatic controls on arctic-alpine forest lines are relaxed, increased decomposition will likely outbalance increased plant productivity, decreasing the overall C sink capacity of displaced tundra.

@article{spitzer_root_2021,
	title = {Root trait–microbial relationships across tundra plant species},
	volume = {229},
	issn = {0028-646X},
	url = {https://doi.org/10.1111/nph.16982},
	doi = {10.1111/nph.16982},
	abstract = {Summary Fine roots, and their functional traits, influence associated rhizosphere microorganisms via root exudation and root litter quality. However, little information is known about their relationship with rhizosphere microbial taxa and functional guilds. We investigated the relationships of 11 fine root traits of 20 sub-arctic tundra meadow plant species and soil microbial community composition, using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We primarily focused on the root economics spectrum, as it provides a useful framework to examine plant strategies by integrating the co-ordination of belowground root traits along a resource acquisition?conservation trade-off axis. We found that the chemical axis of the fine root economics spectrum was positively related to fungal to bacterial ratios, but negatively to Gram-positive to Gram-negative bacterial ratios. However, this spectrum was unrelated to the relative abundance of functional guilds of soil fungi. Nevertheless, the relative abundance of arbuscular mycorrhizal fungi was positively correlated to root carbon content, but negatively to the numbers of root forks per root length. Our results suggest that the fine root economics spectrum is important for predicting broader groups of soil microorganisms (i.e. fungi and bacteria), while individual root traits may be more important for predicting soil microbial taxa and functional guilds.},
	number = {3},
	urldate = {2023-07-22},
	journal = {New Phytologist},
	author = {Spitzer, Clydecia M. and Lindahl, Björn and Wardle, David A. and Sundqvist, Maja K. and Gundale, Michael J. and Fanin, Nicolas and Kardol, Paul},
	month = feb,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {fine root traits, fungi, plant–microorganism interactions, rhizosphere, tundra ecosystems},
	pages = {1508--1520},
}

Summary Fine roots, and their functional traits, influence associated rhizosphere microorganisms via root exudation and root litter quality. However, little information is known about their relationship with rhizosphere microbial taxa and functional guilds. We investigated the relationships of 11 fine root traits of 20 sub-arctic tundra meadow plant species and soil microbial community composition, using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We primarily focused on the root economics spectrum, as it provides a useful framework to examine plant strategies by integrating the co-ordination of belowground root traits along a resource acquisition?conservation trade-off axis. We found that the chemical axis of the fine root economics spectrum was positively related to fungal to bacterial ratios, but negatively to Gram-positive to Gram-negative bacterial ratios. However, this spectrum was unrelated to the relative abundance of functional guilds of soil fungi. Nevertheless, the relative abundance of arbuscular mycorrhizal fungi was positively correlated to root carbon content, but negatively to the numbers of root forks per root length. Our results suggest that the fine root economics spectrum is important for predicting broader groups of soil microorganisms (i.e. fungi and bacteria), while individual root traits may be more important for predicting soil microbial taxa and functional guilds.

@article{myrstener_nitrogen_2021,
	title = {Nitrogen supply and physical disturbance shapes {Arctic} stream nitrogen uptake through effects on metabolic activity},
	volume = {66},
	issn = {0046-5070},
	url = {https://doi.org/10.1111/fwb.13734},
	doi = {10.1111/fwb.13734},
	abstract = {Abstract Climate change in the Arctic is altering the delivery of nutrients from terrestrial to aquatic ecosystems. The impact of these changes on downstream lakes and rivers is influenced by the capacity of small streams to retain such inputs. Given the potential for nutrient limitation in oligotrophic Arctic streams, biotic demand should be high, unless harsh environmental conditions maintain low biomass standing stocks that limit nutrient uptake capacity. We assessed the drivers of nutrient uptake in two contrasting headwater environments in Arctic Sweden: one stream draining upland tundra and the other draining an alluvial valley with birch forest. At both sites, we measured nitrate (NO3?) uptake biweekly using short-term slug releases and estimated rates of gross primary production (GPP) and ecosystem respiration from continuous dissolved oxygen measurements. Catchment characteristics were associated with distinct stream chemical and biological properties. For example, the tundra stream maintained relatively low NO3? concentrations (average: 46 µg N/L) and rates of GPP (0.2 g O2 m?2 day?1). By comparison, the birch forest stream was more NO3? rich (88 µg N/L) and productive (GPP: 1.7 g O2 m?2 day?1). These differences corresponded to greater areal NO3? uptake rate and increased NO3? use efficiency (as uptake velocity) in the birch forest stream (max 192 µg N m?2 min?1 and 96 mm/hr) compared to its tundra counterpart (max 52 µg N m?2 min?1 and 49 mm/hr) during 2017. Further, different sets of environmental drivers predicted temporal patterns of nutrient uptake at these sites: abiotic factors (e.g. NO3? concentration and discharge) were associated with changes in uptake in the tundra stream, while metabolic activity was more important in the birch forest stream. Between sites, variation in uptake metrics suggests that the ability to retain pulses of nutrients is linked to nutrient supply regimes controlled at larger spatial and temporal scales and habitat properties that promote biomass accrual and thus biotic demand. Overall, constraints on biotic potential imposed by the habitat template determined the capacity of these high latitude streams to respond to future changes in nutrient inputs arising from climate warming or human land use. ?},
	number = {8},
	urldate = {2023-07-22},
	journal = {Freshwater Biology},
	author = {Myrstener, Maria and Thomas, Steven A. and Giesler, Reiner and Sponseller, Ryan A.},
	month = aug,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {Arctic, catchment, metabolism, nutrient uptake, tundra},
	pages = {1502--1514},
}

Abstract Climate change in the Arctic is altering the delivery of nutrients from terrestrial to aquatic ecosystems. The impact of these changes on downstream lakes and rivers is influenced by the capacity of small streams to retain such inputs. Given the potential for nutrient limitation in oligotrophic Arctic streams, biotic demand should be high, unless harsh environmental conditions maintain low biomass standing stocks that limit nutrient uptake capacity. We assessed the drivers of nutrient uptake in two contrasting headwater environments in Arctic Sweden: one stream draining upland tundra and the other draining an alluvial valley with birch forest. At both sites, we measured nitrate (NO3?) uptake biweekly using short-term slug releases and estimated rates of gross primary production (GPP) and ecosystem respiration from continuous dissolved oxygen measurements. Catchment characteristics were associated with distinct stream chemical and biological properties. For example, the tundra stream maintained relatively low NO3? concentrations (average: 46 µg N/L) and rates of GPP (0.2 g O2 m?2 day?1). By comparison, the birch forest stream was more NO3? rich (88 µg N/L) and productive (GPP: 1.7 g O2 m?2 day?1). These differences corresponded to greater areal NO3? uptake rate and increased NO3? use efficiency (as uptake velocity) in the birch forest stream (max 192 µg N m?2 min?1 and 96 mm/hr) compared to its tundra counterpart (max 52 µg N m?2 min?1 and 49 mm/hr) during 2017. Further, different sets of environmental drivers predicted temporal patterns of nutrient uptake at these sites: abiotic factors (e.g. NO3? concentration and discharge) were associated with changes in uptake in the tundra stream, while metabolic activity was more important in the birch forest stream. Between sites, variation in uptake metrics suggests that the ability to retain pulses of nutrients is linked to nutrient supply regimes controlled at larger spatial and temporal scales and habitat properties that promote biomass accrual and thus biotic demand. Overall, constraints on biotic potential imposed by the habitat template determined the capacity of these high latitude streams to respond to future changes in nutrient inputs arising from climate warming or human land use. ?

@article{pascual_missing_2021,
	title = {The missing pieces for better future predictions in subarctic ecosystems: {A} {Torneträsk} case study},
	volume = {50},
	issn = {1654-7209},
	url = {https://doi.org/10.1007/s13280-020-01381-1},
	doi = {10.1007/s13280-020-01381-1},
	abstract = {Arctic and subarctic ecosystems are experiencing substantial changes in hydrology, vegetation, permafrost conditions, and carbon cycling, in response to climatic change and other anthropogenic drivers, and these changes are likely to continue over this century. The total magnitude of these changes results from multiple interactions among these drivers. Field measurements can address the overall responses to different changing drivers, but are less capable of quantifying the interactions among them. Currently, a comprehensive assessment of the drivers of ecosystem changes, and the magnitude of their direct and indirect impacts on subarctic ecosystems, is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years, and is one of the most studied sites in the Arctic. In this study, we summarize and rank the drivers of ecosystem change in the Torneträsk area, and propose research priorities identified, by expert assessment, to improve predictions of ecosystem changes. The research priorities identified include understanding impacts on ecosystems brought on by altered frequency and intensity of winter warming events, evapotranspiration rates, rainfall, duration of snow cover and lake-ice, changed soil moisture, and droughts. This case study can help us understand the ongoing ecosystem changes occurring in the Torneträsk area, and contribute to improve predictions of future ecosystem changes at a larger scale. This understanding will provide the basis for the future mitigation and adaptation plans needed in a changing climate.},
	number = {2},
	journal = {Ambio},
	author = {Pascual, Didac and Åkerman, Jonas and Becher, Marina and Callaghan, Terry V. and Christensen, Torben R. and Dorrepaal, Ellen and Emanuelsson, Urban and Giesler, Reiner and Hammarlund, Dan and Hanna, Edward and Hofgaard, Annika and Jin, Hongxiao and Johansson, Cecilia and Jonasson, Christer and Klaminder, Jonatan and Karlsson, Jan and Lundin, Erik and Michelsen, Anders and Olefeldt, David and Persson, Andreas and Phoenix, Gareth K. and Rączkowska, Zofia and Rinnan, Riikka and Ström, Lena and Tang, Jing and Varner, Ruth K. and Wookey, Philip and Johansson, Margareta},
	month = feb,
	year = {2021},
	keywords = {\#nosource},
	pages = {375--392},
}

Arctic and subarctic ecosystems are experiencing substantial changes in hydrology, vegetation, permafrost conditions, and carbon cycling, in response to climatic change and other anthropogenic drivers, and these changes are likely to continue over this century. The total magnitude of these changes results from multiple interactions among these drivers. Field measurements can address the overall responses to different changing drivers, but are less capable of quantifying the interactions among them. Currently, a comprehensive assessment of the drivers of ecosystem changes, and the magnitude of their direct and indirect impacts on subarctic ecosystems, is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years, and is one of the most studied sites in the Arctic. In this study, we summarize and rank the drivers of ecosystem change in the Torneträsk area, and propose research priorities identified, by expert assessment, to improve predictions of ecosystem changes. The research priorities identified include understanding impacts on ecosystems brought on by altered frequency and intensity of winter warming events, evapotranspiration rates, rainfall, duration of snow cover and lake-ice, changed soil moisture, and droughts. This case study can help us understand the ongoing ecosystem changes occurring in the Torneträsk area, and contribute to improve predictions of future ecosystem changes at a larger scale. This understanding will provide the basis for the future mitigation and adaptation plans needed in a changing climate.

@article{gillespie_seasonal_2021,
	title = {The seasonal dynamics of a {High} {Arctic} plant–visitor network: temporal observations and responses to delayed snow melt},
	volume = {8},
	doi = {10.1139/as-2020-0056},
	abstract = {Plant - visitor food webs provide important insights into species interactions, and more information about their seasonal dynamics is vital to understanding the resilience of species to external pressures. Studies of Arctic networks can also improve our understanding of species responses to the pressures of climate change. This study provides the first description of a plant – insect visitor network in Svalbard, a High Arctic archipelago already experiencing the consequences of climate change. A subset of the network was collected from experimental plots where the snow melt date was delayed with snow fences. The deep snow plots delayed flowering and we expected this to disrupt plant-visitor interactions compared to ambient snow conditions. However, the composition of flowers and insect visitors were similar between regimes, and the network tracked patterns of overall flowering phenology. Nevertheless, the deep snow significantly reduced the average overlap between flower availability and insect activity, reducing the probability of an interaction. We suggest that at a landscape scale, Arctic pollinators will benefit from patchy changes to snow melt that maintain heterogeneity in the timing of flowering but changes that increase homogeneity in snowmelt across the landscape may negatively impact some species.},
	number = {3},
	journal = {Arctic Science},
	author = {Gillespie, Mark AK and Cooper, Elisabeth J},
	year = {2021},
	note = {Publisher: Canadian Science Publishing 1840 Woodward Drive, Suite 1, Ottawa, ON K2C 0P7},
	keywords = {\#nosource},
	pages = {786--803},
}

Plant - visitor food webs provide important insights into species interactions, and more information about their seasonal dynamics is vital to understanding the resilience of species to external pressures. Studies of Arctic networks can also improve our understanding of species responses to the pressures of climate change. This study provides the first description of a plant – insect visitor network in Svalbard, a High Arctic archipelago already experiencing the consequences of climate change. A subset of the network was collected from experimental plots where the snow melt date was delayed with snow fences. The deep snow plots delayed flowering and we expected this to disrupt plant-visitor interactions compared to ambient snow conditions. However, the composition of flowers and insect visitors were similar between regimes, and the network tracked patterns of overall flowering phenology. Nevertheless, the deep snow significantly reduced the average overlap between flower availability and insect activity, reducing the probability of an interaction. We suggest that at a landscape scale, Arctic pollinators will benefit from patchy changes to snow melt that maintain heterogeneity in the timing of flowering but changes that increase homogeneity in snowmelt across the landscape may negatively impact some species.

@article{bengtsson_environmental_2021,
	title = {Environmental drivers of {Sphagnum} growth in peatlands across the {Holarctic} region},
	volume = {109},
	issn = {0022-0477},
	url = {https://doi.org/10.1111/1365-2745.13499},
	doi = {10.1111/1365-2745.13499},
	abstract = {Abstract The relative importance of global versus local environmental factors for growth and thus carbon uptake of the bryophyte genus Sphagnum?the main peat-former and ecosystem engineer in northern peatlands?remains unclear. We measured length growth and net primary production (NPP) of two abundant Sphagnum species across 99 Holarctic peatlands. We tested the importance of previously proposed abiotic and biotic drivers for peatland carbon uptake (climate, N deposition, water table depth and vascular plant cover) on these two responses. Employing structural equation models (SEMs), we explored both indirect and direct effects of drivers on Sphagnum growth. Variation in growth was large, but similar within and between peatlands. Length growth showed a stronger response to predictors than NPP. Moreover, the smaller and denser Sphagnum fuscum growing on hummocks had weaker responses to climatic variation than the larger and looser Sphagnum magellanicum growing in the wetter conditions. Growth decreased with increasing vascular plant cover within a site. Between sites, precipitation and temperature increased growth for S. magellanicum. The SEMs indicate that indirect effects are important. For example, vascular plant cover increased with a deeper water table, increased nitrogen deposition, precipitation and temperature. These factors also influenced Sphagnum growth indirectly by affecting moss shoot density. Synthesis. Our results imply that in a warmer climate, S. magellanicum will increase length growth as long as precipitation is not reduced, while S. fuscum is more resistant to decreased precipitation, but also less able to take advantage of increased precipitation and temperature. Such species-specific sensitivity to climate may affect competitive outcomes in a changing environment, and potentially the future carbon sink function of peatlands.},
	number = {1},
	urldate = {2023-07-21},
	journal = {Journal of Ecology},
	author = {Bengtsson, Fia and Rydin, Håkan and Baltzer, Jennifer L. and Bragazza, Luca and Bu, Zhao-Jun and Caporn, Simon J. M. and Dorrepaal, Ellen and Flatberg, Kjell Ivar and Galanina, Olga and Gałka, Mariusz and Ganeva, Anna and Goia, Irina and Goncharova, Nadezhda and Hájek, Michal and Haraguchi, Akira and Harris, Lorna I. and Humphreys, Elyn and Jiroušek, Martin and Kajukało, Katarzyna and Karofeld, Edgar and Koronatova, Natalia G. and Kosykh, Natalia P. and Laine, Anna M. and Lamentowicz, Mariusz and Lapshina, Elena and Limpens, Juul and Linkosalmi, Maiju and Ma, Jin-Ze and Mauritz, Marguerite and Mitchell, Edward A. D. and Munir, Tariq M. and Natali, Susan M. and Natcheva, Rayna and Payne, Richard J. and Philippov, Dmitriy A. and Rice, Steven K. and Robinson, Sean and Robroek, Bjorn J. M. and Rochefort, Line and Singer, David and Stenøien, Hans K. and Tuittila, Eeva-Stiina and Vellak, Kai and Waddington, James Michael and Granath, Gustaf},
	month = jan,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, PAR, climate, global change, net primary production, nitrogen deposition, peat mosses, plant–climate interactions, structural equation model},
	pages = {417--431},
}

Abstract The relative importance of global versus local environmental factors for growth and thus carbon uptake of the bryophyte genus Sphagnum?the main peat-former and ecosystem engineer in northern peatlands?remains unclear. We measured length growth and net primary production (NPP) of two abundant Sphagnum species across 99 Holarctic peatlands. We tested the importance of previously proposed abiotic and biotic drivers for peatland carbon uptake (climate, N deposition, water table depth and vascular plant cover) on these two responses. Employing structural equation models (SEMs), we explored both indirect and direct effects of drivers on Sphagnum growth. Variation in growth was large, but similar within and between peatlands. Length growth showed a stronger response to predictors than NPP. Moreover, the smaller and denser Sphagnum fuscum growing on hummocks had weaker responses to climatic variation than the larger and looser Sphagnum magellanicum growing in the wetter conditions. Growth decreased with increasing vascular plant cover within a site. Between sites, precipitation and temperature increased growth for S. magellanicum. The SEMs indicate that indirect effects are important. For example, vascular plant cover increased with a deeper water table, increased nitrogen deposition, precipitation and temperature. These factors also influenced Sphagnum growth indirectly by affecting moss shoot density. Synthesis. Our results imply that in a warmer climate, S. magellanicum will increase length growth as long as precipitation is not reduced, while S. fuscum is more resistant to decreased precipitation, but also less able to take advantage of increased precipitation and temperature. Such species-specific sensitivity to climate may affect competitive outcomes in a changing environment, and potentially the future carbon sink function of peatlands.

@article{hamard_contribution_2021,
	title = {Contribution of microbial photosynthesis to peatland carbon uptake along a latitudinal gradient},
	volume = {109},
	issn = {0022-0477},
	url = {https://doi.org/10.1111/1365-2745.13732},
	doi = {10.1111/1365-2745.13732},
	abstract = {Abstract Phototrophic microbes, also known as micro-algae, display a high abundance in many terrestrial surface soils. They contribute to atmospheric carbon dioxide fluxes through their photosynthesis, and thus regulate climate similar to plants. However, microbial photosynthesis remains overlooked in most terrestrial ecosystems. Here, we hypothesise that phototrophic microbes significantly contribute to peatland C uptake, unless environmental conditions limit their development and their photosynthetic activity. To test our hypothesis, we studied phototrophic microbial communities in five peatlands distributed along a latitudinal gradient in Europe. By means of metabarcoding, microscopy and cytometry analyses, as well as measures of photosynthesis, we investigated the diversity, absolute abundance and photosynthetic rates of the phototrophic microbial communities. We identified 351 photosynthetic prokaryotic and eukaryotic operational taxonomic units (OTUs) across the five peatlands. We found that water availability and plant composition were important determinants of the composition and the structure of phototrophic microbial communities. Despite environmental shifts in community structure and composition, we showed that microbial C fixation rates remained similar along the latitudinal gradient. Our results further revealed that phototrophic microbes accounted for approximately 10\% of peatland C uptake. Synthesis. Our findings show that phototrophic microbes are extremely diverse and abundant in peatlands. While species turnover with environmental conditions, microbial photosynthesis similarly contributed to peatland C uptake at all latitudes. We estimate that phototrophic microbes take up around 75 MT CO2 per year in northern peatlands. This amount roughly equals the magnitude of projected peatland C loss due to climate warming and highlights the importance of phototrophic microbes for the peatland C cycle.},
	number = {9},
	urldate = {2023-07-21},
	journal = {Journal of Ecology},
	author = {Hamard, Samuel and Céréghino, Regis and Barret, Maialen and Sytiuk, Anna and Lara, Enrique and Dorrepaal, Ellen and Kardol, Paul and Küttim, Martin and Lamentowicz, Mariusz and Leflaive, Joséphine and Le Roux, Gaël and Tuittila, Eeva-Stiina and Jassey, Vincent E. J.},
	month = sep,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, algae, carbon cycle, metabarcoding, microbial diversity, peatland, photosynthesis, phototrophs, primary productivity},
	pages = {3424--3441},
}

Abstract Phototrophic microbes, also known as micro-algae, display a high abundance in many terrestrial surface soils. They contribute to atmospheric carbon dioxide fluxes through their photosynthesis, and thus regulate climate similar to plants. However, microbial photosynthesis remains overlooked in most terrestrial ecosystems. Here, we hypothesise that phototrophic microbes significantly contribute to peatland C uptake, unless environmental conditions limit their development and their photosynthetic activity. To test our hypothesis, we studied phototrophic microbial communities in five peatlands distributed along a latitudinal gradient in Europe. By means of metabarcoding, microscopy and cytometry analyses, as well as measures of photosynthesis, we investigated the diversity, absolute abundance and photosynthetic rates of the phototrophic microbial communities. We identified 351 photosynthetic prokaryotic and eukaryotic operational taxonomic units (OTUs) across the five peatlands. We found that water availability and plant composition were important determinants of the composition and the structure of phototrophic microbial communities. Despite environmental shifts in community structure and composition, we showed that microbial C fixation rates remained similar along the latitudinal gradient. Our results further revealed that phototrophic microbes accounted for approximately 10% of peatland C uptake. Synthesis. Our findings show that phototrophic microbes are extremely diverse and abundant in peatlands. While species turnover with environmental conditions, microbial photosynthesis similarly contributed to peatland C uptake at all latitudes. We estimate that phototrophic microbes take up around 75 MT CO2 per year in northern peatlands. This amount roughly equals the magnitude of projected peatland C loss due to climate warming and highlights the importance of phototrophic microbes for the peatland C cycle.

@article{koranda_mosses_2021,
	title = {Mosses reduce soil nitrogen availability in a subarctic birch forest via effects on soil thermal regime and sequestration of deposited nitrogen},
	volume = {109},
	issn = {0022-0477},
	url = {https://doi.org/10.1111/1365-2745.13567},
	doi = {10.1111/1365-2745.13567},
	abstract = {Abstract In high-latitude ecosystems bryophytes are important drivers of ecosystem functions. Alterations in abundance of mosses due to global change may thus strongly influence carbon (C) and nitrogen (N) cycling and hence cause feedback on climate. The effects of mosses on soil microbial activity are, however, still poorly understood. Our study aims at elucidating how and by which mechanisms bryophytes influence microbial decomposition processes of soil organic matter and thus soil nutrient availability. We present results from a field experiment in a subarctic birch forest in northern Sweden, where we partly removed the moss cover and replaced it with an artificial soil cover for simulating moss effects on soil temperature and moisture. We combined this with a fertilization experiment with 15N-labelled N for analysing the effects of moss N sequestration on soil processes. Our results demonstrate the capacity of mosses to reduce soil N availability and retard N cycling. The comparison with artificial soil cover plots suggests that the effect of mosses on N cycling is linked to the thermal insulation capacity of mosses causing low average soil temperature in summer and strongly reduced soil temperature fluctuations, the latter also leading to a decreased frequency of freeze-thaw events in autumn and spring. Our results also showed, however, that the negative temperature effect of mosses on soil microbial activity was in part compensated by stimulatory effects of the moss layer, possibly linked to leaching of labile substrates from the moss. Furthermore, our results revealed that bryophytes efficiently sequester added N from wet deposition and thus prevent effects of increased atmospheric N deposition on soil N availability and soil processes. Synthesis. Our study emphasizes the important role of mosses in carbon and nutrient cycling in high-latitude ecosystems and the potential strong impacts of reductions in moss abundance on microbial decomposition processes and nutrient availability in subarctic and boreal forests.},
	number = {3},
	urldate = {2023-07-21},
	journal = {Journal of Ecology},
	author = {Koranda, Marianne and Michelsen, Anders},
	month = mar,
	year = {2021},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, bryophytes, extracellular enzyme activities, microbial communities, microbial processes, moss, nitrogen availability, nitrogen cycling, soil temperature},
	pages = {1424--1438},
}

Abstract In high-latitude ecosystems bryophytes are important drivers of ecosystem functions. Alterations in abundance of mosses due to global change may thus strongly influence carbon (C) and nitrogen (N) cycling and hence cause feedback on climate. The effects of mosses on soil microbial activity are, however, still poorly understood. Our study aims at elucidating how and by which mechanisms bryophytes influence microbial decomposition processes of soil organic matter and thus soil nutrient availability. We present results from a field experiment in a subarctic birch forest in northern Sweden, where we partly removed the moss cover and replaced it with an artificial soil cover for simulating moss effects on soil temperature and moisture. We combined this with a fertilization experiment with 15N-labelled N for analysing the effects of moss N sequestration on soil processes. Our results demonstrate the capacity of mosses to reduce soil N availability and retard N cycling. The comparison with artificial soil cover plots suggests that the effect of mosses on N cycling is linked to the thermal insulation capacity of mosses causing low average soil temperature in summer and strongly reduced soil temperature fluctuations, the latter also leading to a decreased frequency of freeze-thaw events in autumn and spring. Our results also showed, however, that the negative temperature effect of mosses on soil microbial activity was in part compensated by stimulatory effects of the moss layer, possibly linked to leaching of labile substrates from the moss. Furthermore, our results revealed that bryophytes efficiently sequester added N from wet deposition and thus prevent effects of increased atmospheric N deposition on soil N availability and soil processes. Synthesis. Our study emphasizes the important role of mosses in carbon and nutrient cycling in high-latitude ecosystems and the potential strong impacts of reductions in moss abundance on microbial decomposition processes and nutrient availability in subarctic and boreal forests.

@article{rudberg_diel_2021,
	title = {Diel {Variability} of {CO2} {Emissions} {From} {Northern} {Lakes}},
	volume = {126},
	copyright = {© 2021. The Authors.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021JG006246},
	doi = {10.1029/2021JG006246},
	abstract = {Lakes are generally supersaturated in carbon dioxide (CO2) and emitters of CO2 to the atmosphere. However, estimates of CO2 flux () from lakes are seldom based on direct flux measurements and usually do not account for nighttime emissions, yielding risk of biased assessments. Here, we present direct measurements from automated floating chambers collected every 2–3 hr and spanning 115 24 hr periods in three boreal lakes during summer stratification and before and after autumn mixing in the most eutrophic lake of these. We observed 40\%–67\% higher mean in daytime during periods of surface water CO2 supersaturation in all lakes. Day-night differences in wind speed were correlated with the day-night differences in the two larger lakes, but in the smallest and most wind-sheltered lake peaks of coincided with low-winds at night. During stratification in the eutrophic lake, CO2 was near equilibrium and diel variability of insignificant, but after autumn mixing was high with distinct diel variability making this lake a net CO2 source on an annual basis. We found that extrapolating daytime measurements to 24 hr periods overestimated by up to 30\%, whereas extrapolating measurements from the stratified period to annual rates in the eutrophic lake underestimated by 86\%. This shows the importance of accounting for diel and seasonal variability in lake CO2 emission estimates.},
	language = {en},
	number = {10},
	urldate = {2023-07-20},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Rudberg, D. and Duc, N. T. and Schenk, J. and Sieczko, A. K. and Pajala, G. and Sawakuchi, H. O. and Verheijen, H. A. and Melack, J. M. and MacIntyre, S. and Karlsson, J. and Bastviken, D.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021JG006246},
	keywords = {\#nosource, automated flux chambers, autumn mixing, carbon dioxide fluxes, diel variability, lake greenhouse gas emissions},
	pages = {e2021JG006246},
}

Lakes are generally supersaturated in carbon dioxide (CO2) and emitters of CO2 to the atmosphere. However, estimates of CO2 flux () from lakes are seldom based on direct flux measurements and usually do not account for nighttime emissions, yielding risk of biased assessments. Here, we present direct measurements from automated floating chambers collected every 2–3 hr and spanning 115 24 hr periods in three boreal lakes during summer stratification and before and after autumn mixing in the most eutrophic lake of these. We observed 40%–67% higher mean in daytime during periods of surface water CO2 supersaturation in all lakes. Day-night differences in wind speed were correlated with the day-night differences in the two larger lakes, but in the smallest and most wind-sheltered lake peaks of coincided with low-winds at night. During stratification in the eutrophic lake, CO2 was near equilibrium and diel variability of insignificant, but after autumn mixing was high with distinct diel variability making this lake a net CO2 source on an annual basis. We found that extrapolating daytime measurements to 24 hr periods overestimated by up to 30%, whereas extrapolating measurements from the stratified period to annual rates in the eutrophic lake underestimated by 86%. This shows the importance of accounting for diel and seasonal variability in lake CO2 emission estimates.

@article{sawakuchi_phosphorus_2021,
	title = {Phosphorus {Regulation} of {Methane} {Oxidation} in {Water} {From} {Ice}-{Covered} {Lakes}},
	volume = {126},
	copyright = {© 2021. The Authors.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020JG006190},
	doi = {10.1029/2020JG006190},
	abstract = {Winter methane (CH4) accumulation in seasonally ice-covered lakes can contribute to large episodic emissions to the atmosphere during spring ice melt. Biological methane oxidation can significantly mitigate such CH4 emissions, but despite favorable CH4 and O2 concentrations, CH4 oxidation appears constrained in some lakes for unknown reasons. Here we experimentally test the hypothesis that phosphorus (P) availability is limiting CH4 oxidation, resulting in differences in ice-out emissions among lakes. We observed a positive relationship between potential CH4 oxidation and P concentration across 12 studied lakes and found an increase in CH4 oxidation in response to P amendment, without any parallel change in the methanotrophic community composition. Hence, while an increase in sedimentary CH4 production and ebullitive emissions may happen with eutrophication, our study indicates that the increase in P associated with eutrophication may also enhance CH4 oxidation. The increase in CH4 oxidation may hence play an important role in nutrient-rich ice-covered lakes where bubbles trapped under the ice may to a greater extent be oxidized, reducing the ice-out emissions of CH4. This may be an important factor regulating CH4 emissions from high latitude lakes.},
	language = {en},
	number = {9},
	urldate = {2023-07-20},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Sawakuchi, Henrique O. and Martin, Gaëtan and Peura, Sari and Bertilsson, Stefan and Karlsson, Jan and Bastviken, David},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020JG006190},
	keywords = {\#nosource, CH4 oxidation, boreal lakes, ice-out CH4 emissions, methanotrophs, phosphorus},
	pages = {e2020JG006190},
}

Winter methane (CH4) accumulation in seasonally ice-covered lakes can contribute to large episodic emissions to the atmosphere during spring ice melt. Biological methane oxidation can significantly mitigate such CH4 emissions, but despite favorable CH4 and O2 concentrations, CH4 oxidation appears constrained in some lakes for unknown reasons. Here we experimentally test the hypothesis that phosphorus (P) availability is limiting CH4 oxidation, resulting in differences in ice-out emissions among lakes. We observed a positive relationship between potential CH4 oxidation and P concentration across 12 studied lakes and found an increase in CH4 oxidation in response to P amendment, without any parallel change in the methanotrophic community composition. Hence, while an increase in sedimentary CH4 production and ebullitive emissions may happen with eutrophication, our study indicates that the increase in P associated with eutrophication may also enhance CH4 oxidation. The increase in CH4 oxidation may hence play an important role in nutrient-rich ice-covered lakes where bubbles trapped under the ice may to a greater extent be oxidized, reducing the ice-out emissions of CH4. This may be an important factor regulating CH4 emissions from high latitude lakes.

@article{gudasz_when_2021,
	title = {When does temperature matter for ecosystem respiration?},
	volume = {3},
	issn = {2515-7620},
	url = {https://dx.doi.org/10.1088/2515-7620/ac3b9f},
	doi = {10.1088/2515-7620/ac3b9f},
	abstract = {The temperature response of ecosystem processes is key to understand and predict impacts of climate change. This is especially true for respiration, given its high temperature sensitivity and major role in the global carbon cycle. However, similar intrinsic temperature sensitivity for respiration does not mean comparable temperature effects across ecosystems and biomes because non-temperature factors can be more important. Here we analyzed soil and sediment respiration data and found that in temperature ranges corresponding to high latitude mean temperatures, absolute respiration rates are more sensitive to non-temperature factors than to projected direct temperature effects. However, at higher temperatures ({\textgreater}20 °C) the direct effect of temperature mediated by temperature sensitivity will likely be more important over changes in non-temperature factors in shaping how respiration change over time. This supports past suggestions that the relatively small projected temperature increase at low (tropical) latitudes may have a large direct impact on absolute respiration. In contrast, absolute respiration rates at high (boreal/arctic) latitudes will likely be more sensitive on the development of the non-temperature factors than on the direct effects of the large projected temperature increase there. Social media abstract. Respiration may be less dependent to changes in temperature at higher than lower latitudes.},
	language = {en},
	number = {12},
	urldate = {2023-07-20},
	journal = {Environmental Research Communications},
	author = {Gudasz, Cristian and Karlsson, Jan and Bastviken, David},
	month = dec,
	year = {2021},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {121001},
}

The temperature response of ecosystem processes is key to understand and predict impacts of climate change. This is especially true for respiration, given its high temperature sensitivity and major role in the global carbon cycle. However, similar intrinsic temperature sensitivity for respiration does not mean comparable temperature effects across ecosystems and biomes because non-temperature factors can be more important. Here we analyzed soil and sediment respiration data and found that in temperature ranges corresponding to high latitude mean temperatures, absolute respiration rates are more sensitive to non-temperature factors than to projected direct temperature effects. However, at higher temperatures (\textgreater20 °C) the direct effect of temperature mediated by temperature sensitivity will likely be more important over changes in non-temperature factors in shaping how respiration change over time. This supports past suggestions that the relatively small projected temperature increase at low (tropical) latitudes may have a large direct impact on absolute respiration. In contrast, absolute respiration rates at high (boreal/arctic) latitudes will likely be more sensitive on the development of the non-temperature factors than on the direct effects of the large projected temperature increase there. Social media abstract. Respiration may be less dependent to changes in temperature at higher than lower latitudes.

@article{krickov_sizable_2021,
	title = {Sizable carbon emission from the floodplain of {Ob} {River}},
	volume = {131},
	issn = {1470-160X},
	url = {https://www.sciencedirect.com/science/article/pii/S1470160X21008293},
	doi = {10.1016/j.ecolind.2021.108164},
	abstract = {The Ob River floodplain is the second largest floodplain in the world. Despite its vast area, estimates of carbon (C) emissions from the Ob River floodplain are largely absent. Here we present seasonal C emission and water area extent from the main channel and the floodplain along a {\textasciitilde}4 km reach in the boreal zone of the Ob River. We found strong seasonality in water area extent of the Ob main channel ({\textasciitilde}1.8 km2) and floodplain ({\textasciitilde}3 km2) with water covering 34\% of land during flood and subsequently declining to {\textasciitilde}16\% and {\textasciitilde}14\% during summer and autumn baseflow, respectively. The C emissions also varied seasonally over the open water period, ranging from −0.1 to 0.6 g C m−2 d−1 for the Ob main channel and from 0 to 9 g C m−2 d−1 for the floodplain. The dissolved organic carbon positively affected CO2 concentrations and fluxes in the floodplain during all seasons, whereas pH and oxygen concentration negatively impacted CO2 concentrations and fluxes. Some nutrients (ammonia and phosphate) positively correlated with CO2 and CH4 concentrations in summer. The total C emission from the study reach (1.8 km2 main channel, 3 km2 floodplain) during moderate flooding was 236 ± 51 tons C yr−1 ({\textgreater}99\% CO2, {\textless}1\% CH4) with the floodplain accounting for {\textasciitilde}65\%. The contribution of the floodplain to the net river C evasion may be even greater during years of high flooding and in northern regions of the Ob River basin, where floodplain soils are more C-rich and are underlain by permafrost, and in years with more extensive flooding.},
	language = {en},
	urldate = {2021-10-28},
	journal = {Ecological Indicators},
	author = {Krickov, Ivan V. and Serikova, Svetlana and Pokrovsky, Oleg S. and Vorobyev, Sergey N. and Lim, Artem G. and Siewert, Matthias B. and Karlsson, Jan},
	month = nov,
	year = {2021},
	keywords = {\#nosource, Carbon emission, Floodplain, Greenhouse gases, Ob river, Seasonal influences},
	pages = {108164},
}

The Ob River floodplain is the second largest floodplain in the world. Despite its vast area, estimates of carbon (C) emissions from the Ob River floodplain are largely absent. Here we present seasonal C emission and water area extent from the main channel and the floodplain along a ~4 km reach in the boreal zone of the Ob River. We found strong seasonality in water area extent of the Ob main channel (~1.8 km2) and floodplain (~3 km2) with water covering 34% of land during flood and subsequently declining to ~16% and ~14% during summer and autumn baseflow, respectively. The C emissions also varied seasonally over the open water period, ranging from −0.1 to 0.6 g C m−2 d−1 for the Ob main channel and from 0 to 9 g C m−2 d−1 for the floodplain. The dissolved organic carbon positively affected CO2 concentrations and fluxes in the floodplain during all seasons, whereas pH and oxygen concentration negatively impacted CO2 concentrations and fluxes. Some nutrients (ammonia and phosphate) positively correlated with CO2 and CH4 concentrations in summer. The total C emission from the study reach (1.8 km2 main channel, 3 km2 floodplain) during moderate flooding was 236 ± 51 tons C yr−1 (\textgreater99% CO2, \textless1% CH4) with the floodplain accounting for ~65%. The contribution of the floodplain to the net river C evasion may be even greater during years of high flooding and in northern regions of the Ob River basin, where floodplain soils are more C-rich and are underlain by permafrost, and in years with more extensive flooding.

@article{yang_effects_2021,
	title = {Effects of a long-term anoxic warming scenario on microbial community structure and functional potential of permafrost-affected soil},
	volume = {32},
	issn = {1099-1530},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ppp.2131},
	doi = {10.1002/ppp.2131},
	abstract = {Permafrost (PF)-affected soils are widespread in the Arctic and store about half the global soil organic carbon. This large carbon pool becomes vulnerable to microbial decomposition through PF warming and deepening of the seasonal thaw layer (active layer [AL]). Here we combined greenhouse gas (GHG) production rate measurements with a metagenome-based assessment of the microbial taxonomic and metabolic potential before and after 5 years of incubation under anoxic conditions at a constant temperature of 4°C in the AL, PF transition layer, and intact PF. Warming led to a rapid initial release of CO2 and, to a lesser extent, CH4 in all layers. After the initial pulse, especially in CO2 production, GHG production rates declined and conditions became more methanogenic. Functional gene-based analyses indicated a decrease in carbon- and nitrogen-cycling genes and a community shift to the degradation of less-labile organic matter. This study reveals low but continuous GHG production in long-term warming scenarios, which coincides with a decrease in the relative abundance of major metabolic pathway genes and an increase in carbohydrate-active enzyme classes.},
	language = {en},
	number = {4},
	urldate = {2021-10-28},
	journal = {Permafrost and Periglacial Processes},
	author = {Yang, Sizhong and Liebner, Susanne and Walz, Josefine and Knoblauch, Christian and Bornemann, Till L. V. and Probst, Alexander J. and Wagner, Dirk and Jetten, Mike S. M. and in ‘t Zandt, Michiel H.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.2131},
	keywords = {\#nosource, climate change, greenhouse gases, microbial dynamics, permafrost},
	pages = {641--656},
}

Permafrost (PF)-affected soils are widespread in the Arctic and store about half the global soil organic carbon. This large carbon pool becomes vulnerable to microbial decomposition through PF warming and deepening of the seasonal thaw layer (active layer [AL]). Here we combined greenhouse gas (GHG) production rate measurements with a metagenome-based assessment of the microbial taxonomic and metabolic potential before and after 5 years of incubation under anoxic conditions at a constant temperature of 4°C in the AL, PF transition layer, and intact PF. Warming led to a rapid initial release of CO2 and, to a lesser extent, CH4 in all layers. After the initial pulse, especially in CO2 production, GHG production rates declined and conditions became more methanogenic. Functional gene-based analyses indicated a decrease in carbon- and nitrogen-cycling genes and a community shift to the degradation of less-labile organic matter. This study reveals low but continuous GHG production in long-term warming scenarios, which coincides with a decrease in the relative abundance of major metabolic pathway genes and an increase in carbohydrate-active enzyme classes.

@article{siewert_uav_2021,
	title = {{UAV} reveals substantial but heterogeneous effects of herbivores on {Arctic} vegetation},
	volume = {11},
	copyright = {2021 The Author(s)},
	issn = {2045-2322},
	url = {https://www.nature.com/articles/s41598-021-98497-5},
	doi = {10.1038/s41598-021-98497-5},
	abstract = {Understanding how herbivores shape plant biomass and distribution is a core challenge in ecology. Yet, the lack of suitable remote sensing technology limits our knowledge of temporal and spatial impacts of mammal herbivores in the Earth system. The regular interannual density fluctuations of voles and lemmings are exceptional with their large reduction of plant biomass in Arctic landscapes during peak years (12–24\%) as previously shown at large spatial scales using satellites. This provides evidence that herbivores are important drivers of observed global changes in vegetation productivity. Here, we use a novel approach with repeated unmanned aerial vehicle (UAV) flights, to map vegetation impact by rodents, indicating that many important aspects of vegetation dynamics otherwise hidden by the coarse resolution of satellite images, including plant–herbivore interactions, can be revealed using UAVs. We quantify areas impacted by rodents at four complex Arctic landscapes with very high spatial resolution UAV imagery to get a new perspective on how herbivores shape Arctic ecosystems. The area impacted by voles and lemmings is indeed substantial, larger at higher altitude tundra environments, varies between habitats depending on local snow cover and plant community composition, and is heterogeneous even within habitats at submeter scales. Coupling this with spectral reflectance of vegetation (NDVI), we can show that the impact on central ecosystem properties like GPP and biomass is stronger than currently accounted for in Arctic ecosystems. As an emerging technology, UAVs will allow us to better disentangle important information on how herbivores maintain spatial heterogeneity, function and diversity in natural ecosystems.},
	language = {en},
	number = {1},
	urldate = {2021-10-28},
	journal = {Scientific Reports},
	author = {Siewert, Matthias B. and Olofsson, Johan},
	month = sep,
	year = {2021},
	note = {Bandiera\_abtest: a
Cc\_license\_type: cc\_by
Cg\_type: Nature Research Journals
Number: 1
Primary\_atype: Research
Publisher: Nature Publishing Group
Subject\_term: Climate-change ecology;Ecosystem ecology
Subject\_term\_id: climate-change-ecology;ecosystem-ecology},
	keywords = {\#nosource, Climate-change ecology, Ecosystem ecology},
	pages = {19468},
}

Understanding how herbivores shape plant biomass and distribution is a core challenge in ecology. Yet, the lack of suitable remote sensing technology limits our knowledge of temporal and spatial impacts of mammal herbivores in the Earth system. The regular interannual density fluctuations of voles and lemmings are exceptional with their large reduction of plant biomass in Arctic landscapes during peak years (12–24%) as previously shown at large spatial scales using satellites. This provides evidence that herbivores are important drivers of observed global changes in vegetation productivity. Here, we use a novel approach with repeated unmanned aerial vehicle (UAV) flights, to map vegetation impact by rodents, indicating that many important aspects of vegetation dynamics otherwise hidden by the coarse resolution of satellite images, including plant–herbivore interactions, can be revealed using UAVs. We quantify areas impacted by rodents at four complex Arctic landscapes with very high spatial resolution UAV imagery to get a new perspective on how herbivores shape Arctic ecosystems. The area impacted by voles and lemmings is indeed substantial, larger at higher altitude tundra environments, varies between habitats depending on local snow cover and plant community composition, and is heterogeneous even within habitats at submeter scales. Coupling this with spectral reflectance of vegetation (NDVI), we can show that the impact on central ecosystem properties like GPP and biomass is stronger than currently accounted for in Arctic ecosystems. As an emerging technology, UAVs will allow us to better disentangle important information on how herbivores maintain spatial heterogeneity, function and diversity in natural ecosystems.

@article{seekell_patterns_2021,
	title = {Patterns and {Variation} of {Littoral} {Habitat} {Size} {Among} {Lakes}},
	volume = {48},
	issn = {1944-8007},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021GL095046},
	doi = {10.1029/2021GL095046},
	abstract = {The littoral zone varies in size among lakes from ∼3\% to 100\% of lake surface area. In this paper, we derive a simple theoretical scaling relationship that explains this variation, and test this theory using bathymetric data across the size spectra of freshwater lakes (surface area = 0.01–82,103 km2, maximum depth = 2–1,741 m). Littoral area primarily reflects the ratio of the maximum depth of photosynthesis to maximum lake depth. However, lakes that are similar in these characteristics can have different relative littoral areas because of variation in basin shape. Hypsometric (area-elevation) models that describe these patterns for individual lakes can be generalized among lakes to accurately predict the relative size of littoral habitat when there is incomplete bathymetric information. Collectively, our results provide simple rules for understanding patterns of littoral habitat size at the regional and global scales.},
	language = {en},
	number = {20},
	urldate = {2021-10-28},
	journal = {Geophysical Research Letters},
	author = {Seekell, D. and Cael, B. and Norman, S. and Byström, P.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021GL095046},
	keywords = {\#nosource, hypsometry, lake morphometry, light penetration, littoral zone, scaling},
	pages = {e2021GL095046},
}

The littoral zone varies in size among lakes from ∼3% to 100% of lake surface area. In this paper, we derive a simple theoretical scaling relationship that explains this variation, and test this theory using bathymetric data across the size spectra of freshwater lakes (surface area = 0.01–82,103 km2, maximum depth = 2–1,741 m). Littoral area primarily reflects the ratio of the maximum depth of photosynthesis to maximum lake depth. However, lakes that are similar in these characteristics can have different relative littoral areas because of variation in basin shape. Hypsometric (area-elevation) models that describe these patterns for individual lakes can be generalized among lakes to accurately predict the relative size of littoral habitat when there is incomplete bathymetric information. Collectively, our results provide simple rules for understanding patterns of littoral habitat size at the regional and global scales.

@article{serk_global_2021,
	title = {Global {CO2} fertilization of {Sphagnum} peat mosses via suppression of photorespiration during the twentieth century},
	volume = {11},
	copyright = {2021 The Author(s)},
	issn = {2045-2322},
	url = {https://www.nature.com/articles/s41598-021-02953-1},
	doi = {10.1038/s41598-021-02953-1},
	abstract = {Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. Atmospheric CO2 levels have increased dramatically during the twentieth century, from 280 to {\textgreater} 400 ppm, which has affected plant carbon dynamics. Net carbon assimilation is strongly reduced by photorespiration, a process that depends on the CO2 to O2 ratio. Here we investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from five continents. Rising CO2 levels generally suppressed photorespiration relative to photosynthesis but the magnitude of suppression depended on the current water table depth. By estimating the changes in water table depth, temperature, and precipitation during the twentieth century, we excluded potential effects of these climate parameters on the observed isotopomer responses. Further, we showed that the photorespiration to photosynthesis ratio varied between Sphagnum subgenera, indicating differences in their photosynthetic capacity. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths.},
	language = {en},
	number = {1},
	urldate = {2022-01-20},
	journal = {Scientific Reports},
	author = {Serk, Henrik and Nilsson, Mats B. and Bohlin, Elisabet and Ehlers, Ina and Wieloch, Thomas and Olid, Carolina and Grover, Samantha and Kalbitz, Karsten and Limpens, Juul and Moore, Tim and Münchberger, Wiebke and Talbot, Julie and Wang, Xianwei and Knorr, Klaus-Holger and Pancotto, Verónica and Schleucher, Jürgen},
	month = dec,
	year = {2021},
	note = {Bandiera\_abtest: a
Cc\_license\_type: cc\_by
Cg\_type: Nature Research Journals
Number: 1
Primary\_atype: Research
Publisher: Nature Publishing Group
Subject\_term: Biochemistry;Biogeochemistry;Biophysics;Chemical biology;Climate sciences;Ecology;Environmental sciences;Plant sciences
Subject\_term\_id: biochemistry;biogeochemistry;biophysics;chemical-biology;climate-sciences;ecology;environmental-sciences;plant-sciences},
	keywords = {\#nosource, Biochemistry, Biogeochemistry, Biophysics, Chemical biology, Climate sciences, Ecology, Environmental sciences, Plant sciences},
	pages = {24517},
}

Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. Atmospheric CO2 levels have increased dramatically during the twentieth century, from 280 to \textgreater 400 ppm, which has affected plant carbon dynamics. Net carbon assimilation is strongly reduced by photorespiration, a process that depends on the CO2 to O2 ratio. Here we investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from five continents. Rising CO2 levels generally suppressed photorespiration relative to photosynthesis but the magnitude of suppression depended on the current water table depth. By estimating the changes in water table depth, temperature, and precipitation during the twentieth century, we excluded potential effects of these climate parameters on the observed isotopomer responses. Further, we showed that the photorespiration to photosynthesis ratio varied between Sphagnum subgenera, indicating differences in their photosynthetic capacity. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths.

@article{lindborg_how_2021,
	title = {How does a wetland plant respond to increasing temperature along a latitudinal gradient?},
	volume = {11},
	issn = {2045-7758},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ece3.8303},
	doi = {10.1002/ece3.8303},
	abstract = {Global warming affects plant fitness through changes in functional traits and thereby ecosystem function. Wetlands are declining worldwide, and hence, ecosystem functions linked to wetlands are threatened. We use Caltha palustris “a common wetland plant” to study whether warming affects growth and reproduction differently depending on origin of source population, potentially affecting phenotypic response to local climate. We conducted a 2-year in situ temperature manipulation experiment using clone pairs of C. palustris in four regions, along a 1300-km latitudinal gradient of Sweden. Open-top chambers were used to passively increase temperature, paired with controls. Growth and reproductive traits were measured from 320 plants (four regions × five sites × two treatments × eight plants) over two consecutive seasons to assess the effect of warming over time. We found that warming increased plant height, leaf area, number of leaves, and roots. High-latitude populations responded more strongly to warming than low-latitude populations, especially by increasing leaf area. Warming increased number of flowers in general, but only in the second year, while number of fruits increased in low-latitude populations the first year. Prolonged warming leads to an increase in both number of leaves and flowers over time. While reproduction shows varying and regional responses to warming, impacts on plant growth, especially in high-latitude populations, have more profound effects. Such effects could lead to changes in plant community composition with increased abundance of fast-growing plants with larger leaves and more clones, affecting plant competition and ecological functions such as decomposition and nutrient retention. Effects of warming were highly context dependent; thus, we encourage further use of warming experiments to predict changes in growth, reproduction, and community composition across wetland types and climate gradients targeting different plant forms.},
	language = {en},
	number = {22},
	urldate = {2022-01-20},
	journal = {Ecology and Evolution},
	author = {Lindborg, Regina and Ermold, Matti and Kuglerová, Lenka and Jansson, Roland and Larson, Keith W. and Milbau, Ann and Cousins, Sara A. O.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.8303},
	keywords = {\#nosource, Caltha palustris, climate change, experiment, open top chamber, traits, wetland},
	pages = {16228--16238},
}

Global warming affects plant fitness through changes in functional traits and thereby ecosystem function. Wetlands are declining worldwide, and hence, ecosystem functions linked to wetlands are threatened. We use Caltha palustris “a common wetland plant” to study whether warming affects growth and reproduction differently depending on origin of source population, potentially affecting phenotypic response to local climate. We conducted a 2-year in situ temperature manipulation experiment using clone pairs of C. palustris in four regions, along a 1300-km latitudinal gradient of Sweden. Open-top chambers were used to passively increase temperature, paired with controls. Growth and reproductive traits were measured from 320 plants (four regions × five sites × two treatments × eight plants) over two consecutive seasons to assess the effect of warming over time. We found that warming increased plant height, leaf area, number of leaves, and roots. High-latitude populations responded more strongly to warming than low-latitude populations, especially by increasing leaf area. Warming increased number of flowers in general, but only in the second year, while number of fruits increased in low-latitude populations the first year. Prolonged warming leads to an increase in both number of leaves and flowers over time. While reproduction shows varying and regional responses to warming, impacts on plant growth, especially in high-latitude populations, have more profound effects. Such effects could lead to changes in plant community composition with increased abundance of fast-growing plants with larger leaves and more clones, affecting plant competition and ecological functions such as decomposition and nutrient retention. Effects of warming were highly context dependent; thus, we encourage further use of warming experiments to predict changes in growth, reproduction, and community composition across wetland types and climate gradients targeting different plant forms.

@article{donis_stratification_2021,
	title = {Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a {European} multilake survey in a heatwave summer},
	volume = {66},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11963},
	doi = {10.1002/lno.11963},
	abstract = {To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.},
	language = {en},
	number = {12},
	urldate = {2022-01-20},
	journal = {Limnology and Oceanography},
	author = {Donis, Daphne and Mantzouki, Evanthia and McGinnis, Daniel F. and Vachon, Dominic and Gallego, Irene and Grossart, Hans-Peter and de Senerpont Domis, Lisette N. and Teurlincx, Sven and Seelen, Laura and Lürling, Miquel and Verstijnen, Yvon and Maliaka, Valentini and Fonvielle, Jeremy and Visser, Petra M. and Verspagen, Jolanda and van Herk, Maria and Antoniou, Maria G. and Tsiarta, Nikoletta and McCarthy, Valerie and Perello, Victor C. and Machado-Vieira, Danielle and de Oliveira, Alinne Gurjão and Maronić, Dubravka Špoljarić and Stević, Filip and Pfeiffer, Tanja Žuna and Vucelić, Itana Bokan and Žutinić, Petar and Udovič, Marija Gligora and Plenković-Moraj, Anđelka and Bláha, Luděk and Geriš, Rodan and Fránková, Markéta and Christoffersen, Kirsten Seestern and Warming, Trine Perlt and Feldmann, Tõnu and Laas, Alo and Panksep, Kristel and Tuvikene, Lea and Kangro, Kersti and Koreivienė, Judita and Karosienė, Jūratė and Kasperovičienė, Jūratė and Savadova-Ratkus, Ksenija and Vitonytė, Irma and Häggqvist, Kerstin and Salmi, Pauliina and Arvola, Lauri and Rothhaupt, Karl and Avagianos, Christos and Kaloudis, Triantafyllos and Gkelis, Spyros and Panou, Manthos and Triantis, Theodoros and Zervou, Sevasti-Kiriaki and Hiskia, Anastasia and Obertegger, Ulrike and Boscaini, Adriano and Flaim, Giovanna and Salmaso, Nico and Cerasino, Leonardo and Haande, Sigrid and Skjelbred, Birger and Grabowska, Magdalena and Karpowicz, Maciej and Chmura, Damian and Nawrocka, Lidia and Kobos, Justyna and Mazur-Marzec, Hanna and Alcaraz-Párraga, Pablo and Wilk-Woźniak, Elżbieta and Krztoń, Wojciech and Walusiak, Edward and Gagala-Borowska, Ilona and Mankiewicz-Boczek, Joana and Toporowska, Magdalena and Pawlik-Skowronska, Barbara and Niedźwiecki, Michał and Pęczuła, Wojciech and Napiórkowska-Krzebietke, Agnieszka and Dunalska, Julita and Sieńska, Justyna and Szymański, Daniel and Kruk, Marek and Budzyńska, Agnieszka and Goldyn, Ryszard and Kozak, Anna and Rosińska, Joanna and Szeląg-Wasielewska, Elżbieta and Domek, Piotr and Jakubowska-Krepska, Natalia and Kwasizur, Kinga and Messyasz, Beata and Pełechata, Aleksandra and Pełechaty, Mariusz and Kokocinski, Mikolaj and Madrecka-Witkowska, Beata and Kostrzewska-Szlakowska, Iwona and Frąk, Magdalena and Bańkowska-Sobczak, Agnieszka and Wasilewicz, Michał and Ochocka, Agnieszka and Pasztaleniec, Agnieszka and Jasser, Iwona and Antão-Geraldes, Ana M. and Leira, Manel and Vasconcelos, Vitor and Morais, Joao and Vale, Micaela and Raposeiro, Pedro M. and Gonçalves, Vítor and Aleksovski, Boris and Krstić, Svetislav and Nemova, Hana and Drastichova, Iveta and Chomova, Lucia and Remec-Rekar, Spela and Elersek, Tina and Hansson, Lars-Anders and Urrutia-Cordero, Pablo and Bravo, Andrea G. and Buck, Moritz and Colom-Montero, William and Mustonen, Kristiina and Pierson, Don and Yang, Yang and Richardson, Jessica and Edwards, Christine and Cromie, Hannah and Delgado-Martín, Jordi and García, David and Cereijo, Jose Luís and Gomà, Joan and Trapote, Mari Carmen and Vegas-Vilarrúbia, Teresa and Obrador, Biel and García-Murcia, Ana and Real, Monserrat and Romans, Elvira and Noguero-Ribes, Jordi and Duque, David Parreño and Fernández-Morán, Elísabeth and Úbeda, Bárbara and Gálvez, José Ángel and Catalán, Núria and Pérez-Martínez, Carmen and Ramos-Rodríguez, Eloísa and Cillero-Castro, Carmen and Moreno-Ostos, Enrique and Blanco, José María and Rodríguez, Valeriano and Montes-Pérez, Jorge Juan and Palomino, Roberto L. and Rodríguez-Pérez, Estela and Hernández, Armand and Carballeira, Rafael and Camacho, Antonio and Picazo, Antonio and Rochera, Carlos and Santamans, Anna C. and Ferriol, Carmen and Romo, Susana and Soria, Juan Miguel and Özen, Arda and Karan, Tünay and Demir, Nilsun and Beklioğlu, Meryem and Filiz, Nur and Levi, Eti and Iskin, Uğur and Bezirci, Gizem and Tavşanoğlu, Ülkü Nihan and Çelik, Kemal and Ozhan, Koray and Karakaya, Nusret and Koçer, Mehmet Ali Turan and Yilmaz, Mete and Maraşlıoğlu, Faruk and Fakioglu, Özden and Soylu, Elif Neyran and Yağcı, Meral Apaydın and Çınar, Şakir and Çapkın, Kadir and Yağcı, Abdulkadir and Cesur, Mehmet and Bilgin, Fuat and Bulut, Cafer and Uysal, Rahmi and Latife, Köker and Akçaalan, Reyhan and Albay, Meriç and Alp, Mehmet Tahir and Özkan, Korhan and Sevindik, Tuğba Ongun and Tunca, Hatice and Önem, Burçin and Paerl, Hans and Carey, Cayelan C. and Ibelings, Bastiaan W.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11963},
	keywords = {\#nosource},
	pages = {4314--4333},
}

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.

@article{attermeyer_carbon_2021,
	title = {Carbon dioxide fluxes increase from day to night across {European} streams},
	volume = {2},
	issn = {2662-4435},
	url = {http://www.nature.com/articles/s43247-021-00192-w},
	doi = {10.1038/s43247-021-00192-w},
	abstract = {Abstract
            
              Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1 mmol m
              −2
              h
              −1
              at midday and midnight, respectively, with night fluxes exceeding those during the day by 39\%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.},
	language = {en},
	number = {1},
	urldate = {2021-09-03},
	journal = {Communications Earth \& Environment},
	author = {Attermeyer, Katrin and Casas-Ruiz, Joan Pere and Fuss, Thomas and Pastor, Ada and Cauvy-Fraunié, Sophie and Sheath, Danny and Nydahl, Anna C. and Doretto, Alberto and Portela, Ana Paula and Doyle, Brian C. and Simov, Nikolay and Gutmann Roberts, Catherine and Niedrist, Georg H. and Timoner, Xisca and Evtimova, Vesela and Barral-Fraga, Laura and Bašić, Tea and Audet, Joachim and Deininger, Anne and Busst, Georgina and Fenoglio, Stefano and Catalán, Núria and de Eyto, Elvira and Pilotto, Francesca and Mor, Jordi-René and Monteiro, Juliana and Fletcher, David and Noss, Christian and Colls, Miriam and Nagler, Magdalena and Liu, Liu and Romero González-Quijano, Clara and Romero, Ferran and Pansch, Nina and Ledesma, José L. J. and Pegg, Josephine and Klaus, Marcus and Freixa, Anna and Herrero Ortega, Sonia and Mendoza-Lera, Clara and Bednařík, Adam and Fonvielle, Jérémy A. and Gilbert, Peter J. and Kenderov, Lyubomir A. and Rulík, Martin and Bodmer, Pascal},
	month = dec,
	year = {2021},
	keywords = {\#nosource},
	pages = {118},
}

Abstract Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1 mmol m −2 h −1 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.

@article{maher_hasselquist_moving_2021,
	title = {Moving towards multi-layered, mixed-species forests in riparian buffers will enhance their long-term function in boreal landscapes},
	volume = {493},
	issn = {03781127},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S037811272100342X},
	doi = {10.1016/j.foreco.2021.119254},
	abstract = {Riparian buffers are the primary tool in forest management for protecting the habitat structure and function of streams. They help protect against biogeochemical perturbation, filter sediments and nutrients, prevent erosion, contribute food to aquatic organisms, regulate light and hence water temperature, contribute deadwood, and preserve biodiversity. However, in production forests of Sweden and Finland, many headwater streams have been straightened, ditched, and/or channelized, resulting in altered hydrology and reduced natural disturbance by floods, which in turn affects important riparian functions. Furthermore, in even-aged management systems as practiced in much of Fennoscandia, understory trees have usually been cleared right up to the stream’s edge during thinning operations, especially around small, headwater streams. Fire suppression has further favored succession towards shade tolerant species. In the regions within Fennoscandia that have experienced this combination of intensive management and lack of natural disturbance, riparian zones are now dominated by single-storied, native Norway spruce. When the adjacent forest is cut, thin (5 - 15m) conifer-dominated riparian buffers are typically left. These buffers do not provide the protection and subsidies, in terms of leaf litter quality, needed to maintain water quality or support riparian or aquatic biodiversity. Based on a literature review, we found compelling evidence that the ecological benefits of multi-layered, mixed-species riparian forest with a large component of broadleaved species are higher than what is now commonly found in the managed stands of Fennoscandia. To improve the functionality of riparian zones, and hence the protection of streams in managed forest landscapes, we present some basic principles that could be used to enhance the ecological function of these interfaces. These management actions should be prioritized on streams and streamside stands that have been affected by simplification either through forest management or hydrological modification. Key to these principles is the planning and managing of buffer zones as early as possible in the rotation to ensure improved function throughout the rotation cycle and not only at final felling. This is well in line with EU and national legislation which can be interpreted as requiring landscape planning at all forest ages to meet biodiversity and other environmental goals. However, it is still rare that planning for conservation is done other than at the final felling stage. Implementing this new strategy is likely to have long-term positive effects and improve the protection of surface waters from negative forestry effects and a history of fire suppression. By following these suggested management principles, there will be a longer time period with high function and greater future management flexibility in addition to the benefits provided by leaving riparian buffers at the final felling stage.},
	language = {en},
	urldate = {2021-09-03},
	journal = {Forest Ecology and Management},
	author = {Maher Hasselquist, Eliza and Kuglerová, Lenka and Sjögren, Jörgen and Hjältén, Joakim and Ring, Eva and Sponseller, Ryan A. and Andersson, Elisabet and Lundström, Johanna and Mancheva, Irina and Nordin, Annika and Laudon, Hjalmar},
	month = aug,
	year = {2021},
	keywords = {\#nosource},
	pages = {119254},
}

Riparian buffers are the primary tool in forest management for protecting the habitat structure and function of streams. They help protect against biogeochemical perturbation, filter sediments and nutrients, prevent erosion, contribute food to aquatic organisms, regulate light and hence water temperature, contribute deadwood, and preserve biodiversity. However, in production forests of Sweden and Finland, many headwater streams have been straightened, ditched, and/or channelized, resulting in altered hydrology and reduced natural disturbance by floods, which in turn affects important riparian functions. Furthermore, in even-aged management systems as practiced in much of Fennoscandia, understory trees have usually been cleared right up to the stream’s edge during thinning operations, especially around small, headwater streams. Fire suppression has further favored succession towards shade tolerant species. In the regions within Fennoscandia that have experienced this combination of intensive management and lack of natural disturbance, riparian zones are now dominated by single-storied, native Norway spruce. When the adjacent forest is cut, thin (5 - 15m) conifer-dominated riparian buffers are typically left. These buffers do not provide the protection and subsidies, in terms of leaf litter quality, needed to maintain water quality or support riparian or aquatic biodiversity. Based on a literature review, we found compelling evidence that the ecological benefits of multi-layered, mixed-species riparian forest with a large component of broadleaved species are higher than what is now commonly found in the managed stands of Fennoscandia. To improve the functionality of riparian zones, and hence the protection of streams in managed forest landscapes, we present some basic principles that could be used to enhance the ecological function of these interfaces. These management actions should be prioritized on streams and streamside stands that have been affected by simplification either through forest management or hydrological modification. Key to these principles is the planning and managing of buffer zones as early as possible in the rotation to ensure improved function throughout the rotation cycle and not only at final felling. This is well in line with EU and national legislation which can be interpreted as requiring landscape planning at all forest ages to meet biodiversity and other environmental goals. However, it is still rare that planning for conservation is done other than at the final felling stage. Implementing this new strategy is likely to have long-term positive effects and improve the protection of surface waters from negative forestry effects and a history of fire suppression. By following these suggested management principles, there will be a longer time period with high function and greater future management flexibility in addition to the benefits provided by leaving riparian buffers at the final felling stage.

@incollection{jonsson_role_2021,
	address = {Cham},
	title = {The {Role} of {Macroinvertebrates} on {Plant} {Litter} {Decomposition} in {Streams}},
	isbn = {978-3-030-72854-0},
	url = {https://doi.org/10.1007/978-3-030-72854-0_10},
	abstract = {Macroinvertebrate detritivores (i.e., shredders) in freshwaters are often a main driver of decomposition rates of terrestrial plant litter. Yet, the extent to which shredders drive this process depends on the specific functional traits and species present in the shredder community, which in turn are determined by the broader species pool, as well as a range of local environmental conditions, such as pH, substrate characteristics, water chemistry, water temperature, and current velocity. Projected global change will modify several of these environmental conditions, with potential consequences for litter decomposition rates and overall carbon cycling in freshwaters. In this chapter, we describe how a range of freshwater environmental conditions determines the presence of certain species (i.e., functional traits) and the characteristics of shredder communities (i.e., species composition and richness). We then discuss how these characteristics in turn may influence interactions among shredders, and between shredders and other freshwater organisms, to determine their influence on litter decomposition in streams.},
	language = {en},
	urldate = {2021-09-03},
	booktitle = {The {Ecology} of {Plant} {Litter} {Decomposition} in {Stream} {Ecosystems}},
	publisher = {Springer International Publishing},
	author = {Jonsson, Micael and Sponseller, Ryan A.},
	editor = {Swan, Christopher M. and Boyero, Luz and Canhoto, Cristina},
	year = {2021},
	doi = {10.1007/978-3-030-72854-0_10},
	keywords = {\#nosource},
	pages = {193--216},
}

Macroinvertebrate detritivores (i.e., shredders) in freshwaters are often a main driver of decomposition rates of terrestrial plant litter. Yet, the extent to which shredders drive this process depends on the specific functional traits and species present in the shredder community, which in turn are determined by the broader species pool, as well as a range of local environmental conditions, such as pH, substrate characteristics, water chemistry, water temperature, and current velocity. Projected global change will modify several of these environmental conditions, with potential consequences for litter decomposition rates and overall carbon cycling in freshwaters. In this chapter, we describe how a range of freshwater environmental conditions determines the presence of certain species (i.e., functional traits) and the characteristics of shredder communities (i.e., species composition and richness). We then discuss how these characteristics in turn may influence interactions among shredders, and between shredders and other freshwater organisms, to determine their influence on litter decomposition in streams.

@article{gomez-gener_global_2021,
	title = {Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions},
	volume = {14},
	copyright = {2021 The Author(s), under exclusive licence to Springer Nature Limited},
	issn = {1752-0908},
	url = {https://www.nature.com/articles/s41561-021-00722-3},
	doi = {10.1038/s41561-021-00722-3},
	abstract = {Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27\% (0.9 gC m−2 d−1) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65–1.8 PgC yr−1) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20–0.55 PgC yr−1.},
	language = {en},
	number = {5},
	urldate = {2021-09-03},
	journal = {Nature Geoscience},
	author = {Gómez-Gener, Lluís and Rocher-Ros, Gerard and Battin, Tom and Cohen, Matthew J. and Dalmagro, Higo J. and Dinsmore, Kerry J. and Drake, Travis W. and Duvert, Clément and Enrich-Prast, Alex and Horgby, Åsa and Johnson, Mark S. and Kirk, Lily and Machado-Silva, Fausto and Marzolf, Nicholas S. and McDowell, Mollie J. and McDowell, William H. and Miettinen, Heli and Ojala, Anne K. and Peter, Hannes and Pumpanen, Jukka and Ran, Lishan and Riveros-Iregui, Diego A. and Santos, Isaac R. and Six, Johan and Stanley, Emily H. and Wallin, Marcus B. and White, Shane A. and Sponseller, Ryan A.},
	month = may,
	year = {2021},
	note = {Bandiera\_abtest: a
Cg\_type: Nature Research Journals
Number: 5
Primary\_atype: Research
Publisher: Nature Publishing Group
Subject\_term: Carbon cycle;Ecosystem ecology;Limnology
Subject\_term\_id: carbon-cycle;ecosystem-ecology;limnology},
	keywords = {\#nosource},
	pages = {289--294},
}

Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m−2 d−1) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65–1.8 PgC yr−1) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20–0.55 PgC yr−1.

@article{klaus_tree_2021,
	title = {Tree line advance reduces mixing and oxygen concentrations in arctic–alpine lakes through wind sheltering and organic carbon supply},
	volume = {27},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15660},
	doi = {10.1111/gcb.15660},
	abstract = {Oxygen depletion in lake bottom waters has adverse impacts on ecosystem health including decreased water quality from release of nutrients and reduced substances from sediments, and the reduction of fish growth and reproduction. Depletion occurs when oxygen is consumed during decomposition of organic matter, and oxygen replenishment is limited by water column stratification. Arctic–alpine lakes are often well mixed and oxygenated, but rapid climate change in these regions is an important driver of shifts in catchment vegetation that could affect the mixing and oxygen dynamics of lakes. Here, we analyze high-resolution time series of dissolved oxygen concentration and temperature profiles in 40 Swedish arctic–alpine lakes across the tree line ecotone. The lakes stratified for 1−125 days, and during stratification, near-bottom dissolved oxygen concentrations changed by −0.20 to +0.15 mg L−1 day−1, resulting in final concentrations of 1.1−15.5 mg L−1 at the end of the longest stratification period. Structural equation modeling revealed that lakes with taller shoreline vegetation relative to lake area had higher dissolved organic carbon concentrations and oxygen consumption rates, but also lower wind speeds and longer stratification periods, and ultimately, lower near-bottom dissolved oxygen concentrations. We use an index of shoreline canopy height and lake area to predict variations among our study lakes in near-bottom dissolved oxygen concentrations at the end of the longest stratification period (R2 = 0.41). Upscaling this relationship to 8392 Swedish arctic–alpine lakes revealed that near-bottom dissolved oxygen concentrations drop below 3, 5, and 7 mg L−1 in 15\%, 32\%, and 53\% of the lakes and that this proportion is sensitive (5\%−22\%, 13\%−45\%, and 29\%−69\%) to hypothetical tree line shifts observed in the past century or reconstructed for the Holocene (±200 m elevation; ±0.5° latitude). Assuming space-for-time substitution, we predict that tree line advance will decrease near-bottom dissolved oxygen concentrations in many arctic–alpine lakes.},
	language = {en},
	number = {18},
	urldate = {2021-09-03},
	journal = {Global Change Biology},
	author = {Klaus, Marcus and Karlsson, Jan and Seekell, David},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15660},
	keywords = {\#nosource, dissolved organic carbon, environmental change, forest–tundra ecotone, hypoxia, lake ecosystem, lake stratification, thermal structure, wind speed},
	pages = {4238--4253},
}

Oxygen depletion in lake bottom waters has adverse impacts on ecosystem health including decreased water quality from release of nutrients and reduced substances from sediments, and the reduction of fish growth and reproduction. Depletion occurs when oxygen is consumed during decomposition of organic matter, and oxygen replenishment is limited by water column stratification. Arctic–alpine lakes are often well mixed and oxygenated, but rapid climate change in these regions is an important driver of shifts in catchment vegetation that could affect the mixing and oxygen dynamics of lakes. Here, we analyze high-resolution time series of dissolved oxygen concentration and temperature profiles in 40 Swedish arctic–alpine lakes across the tree line ecotone. The lakes stratified for 1−125 days, and during stratification, near-bottom dissolved oxygen concentrations changed by −0.20 to +0.15 mg L−1 day−1, resulting in final concentrations of 1.1−15.5 mg L−1 at the end of the longest stratification period. Structural equation modeling revealed that lakes with taller shoreline vegetation relative to lake area had higher dissolved organic carbon concentrations and oxygen consumption rates, but also lower wind speeds and longer stratification periods, and ultimately, lower near-bottom dissolved oxygen concentrations. We use an index of shoreline canopy height and lake area to predict variations among our study lakes in near-bottom dissolved oxygen concentrations at the end of the longest stratification period (R2 = 0.41). Upscaling this relationship to 8392 Swedish arctic–alpine lakes revealed that near-bottom dissolved oxygen concentrations drop below 3, 5, and 7 mg L−1 in 15%, 32%, and 53% of the lakes and that this proportion is sensitive (5%−22%, 13%−45%, and 29%−69%) to hypothetical tree line shifts observed in the past century or reconstructed for the Holocene (±200 m elevation; ±0.5° latitude). Assuming space-for-time substitution, we predict that tree line advance will decrease near-bottom dissolved oxygen concentrations in many arctic–alpine lakes.

@article{seekell_fractal_2021,
	title = {The {Fractal} {Scaling} {Relationship} for {River} {Inlets} to {Lakes}},
	volume = {48},
	issn = {1944-8007},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL093366},
	doi = {10.1029/2021GL093366},
	abstract = {Scaling relationships provide simple rules for understanding complex hydrographic patterns. Globally, river inlet abundance varies among lakes by about three orders of magnitude, but few scaling relationships describe this aspect of lake-river connectivity. In this study, we describe a simple theoretical scaling relationship between lake surface area and river inlet abundance, and test this theory using data from Scandinavia. On average, the number of inlets increases by 67\% for each doubling of lake area. However, lakes of vastly different areas can have the same number of inlets with relatively small variations of drainage density, lake shape, or junction angle - characteristics that can often be linked to specific geological processes. Our approach bridges the gap between the detailed understanding of geomorphic processes and large-scale statistical relationships, and engenders predictions about additional patterns including the relationship between lake area and water residence time.},
	language = {en},
	number = {9},
	urldate = {2021-09-03},
	journal = {Geophysical Research Letters},
	author = {Seekell, D. and Cael, B. and Lindmark, E. and Byström, P.},
	year = {2021},
	note = {\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021GL093366},
	keywords = {\#nosource, fractal dimension, hydrography, junction angle, river inlets, scaling},
	pages = {e2021GL093366},
}

Scaling relationships provide simple rules for understanding complex hydrographic patterns. Globally, river inlet abundance varies among lakes by about three orders of magnitude, but few scaling relationships describe this aspect of lake-river connectivity. In this study, we describe a simple theoretical scaling relationship between lake surface area and river inlet abundance, and test this theory using data from Scandinavia. On average, the number of inlets increases by 67% for each doubling of lake area. However, lakes of vastly different areas can have the same number of inlets with relatively small variations of drainage density, lake shape, or junction angle - characteristics that can often be linked to specific geological processes. Our approach bridges the gap between the detailed understanding of geomorphic processes and large-scale statistical relationships, and engenders predictions about additional patterns including the relationship between lake area and water residence time.

@article{olid_role_2021,
	title = {The {Role} of {Methane} {Transport} {From} the {Active} {Layer} in {Sustaining} {Methane} {Emissions} and {Food} {Chains} in {Subarctic} {Ponds}},
	volume = {126},
	copyright = {© 2021. The Authors.},
	issn = {2169-8961},
	url = {http://agupubs.pericles.prod.literatumonline.com/doi/abs/10.1029/2020JG005810},
	doi = {10.1029/2020jg005810},
	abstract = {Groundwater discharge from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds and its influence on the trophic support and nutritional quality of pond food chains remains unexplored. We quantified the transport of CH4 from the active layer through groundwater discharge into thaw ponds in a subarctic catchment in northern Sweden, using radon (222Rn) as groundwater tracer. We analyzed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of groundwater-mediated CH4 inputs on the aquatic food chains. Our results indicate that active layer groundwater discharge flows are nontrivial (range 6\%–46\% of pond volume per day) and the associated CH4 fluxes (median 339 mg C m−2day−1, interquartile range [IQR]: 179–419 mg C m−2 day−1) can sustain the diffusive CH4 emissions from most of the ponds (155 mg C m−2 day−1, IQR: 55–234 mg C m−2 day−1). Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon (C) isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Overall, this work links physical (CH4 transport from the active layer), biogeochemical (CH4 emission), and ecological (MOB-consumer interaction) processes to provide direct evidence for the role of active layer groundwater discharge in CH4 cycling of subarctic thaw ponds.},
	language = {en},
	number = {3},
	urldate = {2021-04-01},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Olid, C. and Zannella, A. and Lau, D. C. P.},
	year = {2021},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020JG005810},
	keywords = {\#nosource, climate change, groundwater, methane, methane-oxidizing bacteria, ponds, trophic chain},
	pages = {e2020JG005810},
}

Groundwater discharge from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds and its influence on the trophic support and nutritional quality of pond food chains remains unexplored. We quantified the transport of CH4 from the active layer through groundwater discharge into thaw ponds in a subarctic catchment in northern Sweden, using radon (222Rn) as groundwater tracer. We analyzed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of groundwater-mediated CH4 inputs on the aquatic food chains. Our results indicate that active layer groundwater discharge flows are nontrivial (range 6%–46% of pond volume per day) and the associated CH4 fluxes (median 339 mg C m−2day−1, interquartile range [IQR]: 179–419 mg C m−2 day−1) can sustain the diffusive CH4 emissions from most of the ponds (155 mg C m−2 day−1, IQR: 55–234 mg C m−2 day−1). Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon (C) isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Overall, this work links physical (CH4 transport from the active layer), biogeochemical (CH4 emission), and ecological (MOB-consumer interaction) processes to provide direct evidence for the role of active layer groundwater discharge in CH4 cycling of subarctic thaw ponds.

@article{kytoviita_idiosyncratic_2021,
	title = {Idiosyncratic responses to simulated herbivory by root fungal symbionts in a subarctic meadow},
	volume = {53},
	issn = {1523-0430, 1938-4246},
	url = {https://www.tandfonline.com/doi/full/10.1080/15230430.2021.1878738},
	doi = {10.1080/15230430.2021.1878738},
	abstract = {Plant-associated fungi have elementary roles in ecosystem productivity. There is little information on the interactions between arbuscular mycorrhizal (AM) fungal symbiosis, fine endophytic (FE) and dark septate endophytic (DSE) fungi, and their host plants in cold climate systems. In particular, the environmental filters potentially driving the relative abundance of these root symbionts remain unknown. We investigated the interlinkage of plant and belowground fungal responses to simu­ lated herbivory (clipping, fertilization, and trampling) in a subarctic meadow system. AM and FE frequency in the two target plant roots, Potentilla crantzii and Saussurea alpina, was unaffected by simulated herbivory, highlighting the importance and resilience of arbuscule forming mycorrhizas in a range of environmental conditions. Fertilization and trampling increased DSE colonization in P. crantzii roots although generally P. crantzii performance was reduced in these plots. The idiosyncratic responses by DSE fungal frequency in the two host plants in our experiment indicate that the host plant identity has a pivotal role in the DSE fungus–plant outcome. DSE fungal frequency did not respond to environmental manipulations in a manner similar to arbuscular mycorrhizas, suggesting that they have a different role in plant ecology.},
	language = {en},
	number = {1},
	urldate = {2021-04-01},
	journal = {Arctic, Antarctic, and Alpine Research},
	author = {Kytöviita, Minna-Maarit and Olofsson, Johan},
	month = jan,
	year = {2021},
	keywords = {\#nosource},
	pages = {80--92},
}

Plant-associated fungi have elementary roles in ecosystem productivity. There is little information on the interactions between arbuscular mycorrhizal (AM) fungal symbiosis, fine endophytic (FE) and dark septate endophytic (DSE) fungi, and their host plants in cold climate systems. In particular, the environmental filters potentially driving the relative abundance of these root symbionts remain unknown. We investigated the interlinkage of plant and belowground fungal responses to simu­ lated herbivory (clipping, fertilization, and trampling) in a subarctic meadow system. AM and FE frequency in the two target plant roots, Potentilla crantzii and Saussurea alpina, was unaffected by simulated herbivory, highlighting the importance and resilience of arbuscule forming mycorrhizas in a range of environmental conditions. Fertilization and trampling increased DSE colonization in P. crantzii roots although generally P. crantzii performance was reduced in these plots. The idiosyncratic responses by DSE fungal frequency in the two host plants in our experiment indicate that the host plant identity has a pivotal role in the DSE fungus–plant outcome. DSE fungal frequency did not respond to environmental manipulations in a manner similar to arbuscular mycorrhizas, suggesting that they have a different role in plant ecology.

@article{karlsson_carbon_2021,
	title = {Carbon emission from {Western} {Siberian} inland waters},
	volume = {12},
	copyright = {2021 The Author(s)},
	issn = {2041-1723},
	url = {http://www.nature.com/articles/s41467-021-21054-1},
	doi = {10.1038/s41467-021-21054-1},
	abstract = {High-latitude regions play a key role in the carbon (C) cycle and climate system. An important question is the degree of mobilization and atmospheric release of vast soil C stocks, partly stored in permafrost, with amplified warming of these regions. A fraction of this C is exported to inland waters and emitted to the atmosphere, yet these losses are poorly constrained and seldom accounted for in assessments of high-latitude C balances. This is particularly relevant for Western Siberia, with its extensive peatland C stocks, which can be strongly sensitive to the ongoing changes in climate. Here we quantify C emission from inland waters, including the Ob’ River (Arctic’s largest watershed), across all permafrost zones of Western Siberia. We show that the inland water C emission is high (0.08–0.10 Pg C yr−1) and of major significance in the regional C cycle, largely exceeding (7–9 times) C export to the Arctic Ocean and reaching nearly half (35–50\%) of the region’s land C uptake. This important role of C emission from inland waters highlights the need for coupled land–water studies to understand the contemporary C cycle and its response to warming.},
	language = {en},
	number = {1},
	urldate = {2021-04-01},
	journal = {Nature Communications},
	author = {Karlsson, Jan and Serikova, Svetlana and Vorobyev, Sergey N. and Rocher-Ros, Gerard and Denfeld, Blaize and Pokrovsky, Oleg S.},
	month = feb,
	year = {2021},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {825},
}

High-latitude regions play a key role in the carbon (C) cycle and climate system. An important question is the degree of mobilization and atmospheric release of vast soil C stocks, partly stored in permafrost, with amplified warming of these regions. A fraction of this C is exported to inland waters and emitted to the atmosphere, yet these losses are poorly constrained and seldom accounted for in assessments of high-latitude C balances. This is particularly relevant for Western Siberia, with its extensive peatland C stocks, which can be strongly sensitive to the ongoing changes in climate. Here we quantify C emission from inland waters, including the Ob’ River (Arctic’s largest watershed), across all permafrost zones of Western Siberia. We show that the inland water C emission is high (0.08–0.10 Pg C yr−1) and of major significance in the regional C cycle, largely exceeding (7–9 times) C export to the Arctic Ocean and reaching nearly half (35–50%) of the region’s land C uptake. This important role of C emission from inland waters highlights the need for coupled land–water studies to understand the contemporary C cycle and its response to warming.

@article{shirokova_diurnal_2020,
	title = {Diurnal cycles in thermokarst lakes of a permafrost peatland},
	volume = {4},
	copyright = {Copyright (c) 2020 Limnology and Freshwater Biology},
	issn = {2658-3518},
	url = {http://limnolfwbiol.com/index.php/LFWB/article/view/643},
	doi = {10.31951/2658-3518-2020-A-4-886},
	abstract = {Despite the importance of surface waters of permafrost landscapes in carbon (C) emission, dissolved C, metal storage and export, the diel pattern of dissolved components and gases in thermokarst lakes remain virtually unknown. Here we discovered a factor of 2 to 3 higher CO2 concentrations and fluxes during the night compared to day-time in the high-DOC lake. The emission fluxes in the low-DOC lake increased from zero to negative values during the day to highly positive values during the end of the night and early morning. The bulk of dissolved (\< 0.45 m) hydrochemical parameters remained highly stable with 10\% variation in concentration over 2 days of observation. Overall, the impact of diel cycle on dissolved CH4, DOC, nutrient and metal concentration was below 10\%. However, neglecting night-time period may underestimate net CO2 emission by ca. 30 to 50\% in small organic-rich thaw ponds and switch the CO2 exchange from uptake/zero to net emission in larger thermokarst lakes. Given the dominance of large lakes in permafrost regions, the global underestimation of the emission flux may be quite high. As such, monitoring CO2 concentrations and fluxes in thermokarst lakes during months of extended night time (August to October) is mandatory for assessing the net emissions from lentic waters of frozen peatlands.},
	language = {en},
	urldate = {2024-03-27},
	journal = {Limnology and Freshwater Biology},
	author = {Shirokova, L. S. and Payandi-Rolland, D. and Lim, A. G. and Manasypov, R. M. and Allen, J. and Rols, J.-L. and Benezeth, P. and Karlsson, J. and Pokrovsky, O. S.},
	month = sep,
	year = {2020},
	keywords = {\#nosource, GHG emission, organic carbon, pond, thermokarst, trace metal, warming},
	pages = {886--887},
}

Despite the importance of surface waters of permafrost landscapes in carbon (C) emission, dissolved C, metal storage and export, the diel pattern of dissolved components and gases in thermokarst lakes remain virtually unknown. Here we discovered a factor of 2 to 3 higher CO2 concentrations and fluxes during the night compared to day-time in the high-DOC lake. The emission fluxes in the low-DOC lake increased from zero to negative values during the day to highly positive values during the end of the night and early morning. The bulk of dissolved (< 0.45 m) hydrochemical parameters remained highly stable with 10% variation in concentration over 2 days of observation. Overall, the impact of diel cycle on dissolved CH4, DOC, nutrient and metal concentration was below 10%. However, neglecting night-time period may underestimate net CO2 emission by ca. 30 to 50% in small organic-rich thaw ponds and switch the CO2 exchange from uptake/zero to net emission in larger thermokarst lakes. Given the dominance of large lakes in permafrost regions, the global underestimation of the emission flux may be quite high. As such, monitoring CO2 concentrations and fluxes in thermokarst lakes during months of extended night time (August to October) is mandatory for assessing the net emissions from lentic waters of frozen peatlands.

@article{payandi-rolland_doc_2020,
	title = {{DOC} biodegradation behavior along permafrost affected hydrological continuum},
	volume = {4},
	copyright = {Copyright (c) 2020 Limnology and Freshwater Biology},
	issn = {2658-3518},
	url = {http://limnolfwbiol.com/index.php/LFWB/article/view/638},
	doi = {10.31951/2658-3518-2020-A-4-874},
	abstract = {In Arctic regions, water bodies are hot spots of dissolved organic carbon (DOC) biodegradation, and their well-known large heterogeneity in the permafrost affected area could lead to a misrepresentation of their importance in the carbon (C) cycle. In this study, the biodegradation potential of various water bodies from two hydrological continuums has been assessed via 15 days aerobic incubation of waters. Results show that biodegradability of waters increases along the continuum while the removal rate of DOC decreases as the consequence of a preferential biodegradation of low molecular weight organic acids (LMWOA). This preferential uptake leads to a relative accumulation of aromatic compounds in the end-members of the continuum. This suggests a shift in the dominantly used pools of DOC along the continuum: a rapidly consumed DOC pool at the beginning of the continuum and a more slowly consumed one at the end of the continuum.},
	language = {en},
	urldate = {2024-03-27},
	journal = {Limnology and Freshwater Biology},
	author = {Payandi-Rolland, D. and Shirokova, L. S. and Tesfa, M. and Benezeth, P. and Lim, A. and Kuzmina, D. and Karlsson, J. and Giesler, R. and Pokrovsky, O. S.},
	month = sep,
	year = {2020},
	keywords = {\#nosource, aromaticity},
	pages = {874--875},
}

In Arctic regions, water bodies are hot spots of dissolved organic carbon (DOC) biodegradation, and their well-known large heterogeneity in the permafrost affected area could lead to a misrepresentation of their importance in the carbon (C) cycle. In this study, the biodegradation potential of various water bodies from two hydrological continuums has been assessed via 15 days aerobic incubation of waters. Results show that biodegradability of waters increases along the continuum while the removal rate of DOC decreases as the consequence of a preferential biodegradation of low molecular weight organic acids (LMWOA). This preferential uptake leads to a relative accumulation of aromatic compounds in the end-members of the continuum. This suggests a shift in the dominantly used pools of DOC along the continuum: a rapidly consumed DOC pool at the beginning of the continuum and a more slowly consumed one at the end of the continuum.

@article{lupon_discrete_2020,
	title = {Discrete groundwater inflows influence patterns of nitrogen uptake in a boreal headwater stream},
	volume = {39},
	issn = {2161-9549},
	url = {https://www.journals.uchicago.edu/doi/abs/10.1086/708521},
	doi = {10.1086/708521},
	abstract = {Dissolved organic carbon (DOC) influences stream nitrogen (N) dynamics by regulating the nutrient demand of heterotrophic microbes and mediating their interactions with nitrifiers. However, DOC supply to streams is dynamic in space and time, which may create variability in N dynamics as a result of shifts between heterotrophic and chemoautotrophic influences. To test this, we measured spatial and temporal variation in concentrations and net uptake of dissolved organic nitrogen (DON), ammonium (NH4+), and nitrate (NO3−) along a 1.4-km boreal stream fed by 4 discrete groundwater inflow zones. We also performed constant rate additions of NH4+, with and without acetate, to test the influence of labile DOC availability on N cycling. Groundwater N supply did not drive spatial patterns in N concentrations. However, we observed high rates of net NH4+ uptake at the sub-reach with the greatest groundwater DOC inputs, whereas net nitrification occurred where such inputs were negligible. At the reach scale, net DON and NH4+ uptake increased with greater groundwater discharge, DOC∶DIN, and ecosystem respiration, whereas net nitrification increased with greater DOC aromaticity. Finally, constant rate additions showed that, under increased DOC availability, NH4+ uptake increased 2×, whereas the proportion of NH4+ nitrified decreased from 42 to 15\%. Together, these observations suggest that nitrification rivals heterotrophic uptake when aromatic DOC promotes heterotrophic carbon limitation. Discrete groundwater inflows and periods of elevated discharge can partially alleviate this limitation by supplying labile DOC from riparian soils. Hence, accounting for these land–water connections, over both time and space, is critical for understanding N dynamics in boreal streams.},
	number = {2},
	urldate = {2024-03-27},
	journal = {Freshwater Science},
	author = {Lupon, Anna and Denfeld, Blaize A. and Laudon, Hjalmar and Leach, Jason and Sponseller, Ryan A.},
	month = jun,
	year = {2020},
	note = {Publisher: The University of Chicago Press},
	keywords = {\#nosource, dissolved organic carbon, dissolved organic nitrogen, groundwater inputs, Krycklan, metabolism, net nitrogen uptake, nitrification},
	pages = {228--240},
}

Dissolved organic carbon (DOC) influences stream nitrogen (N) dynamics by regulating the nutrient demand of heterotrophic microbes and mediating their interactions with nitrifiers. However, DOC supply to streams is dynamic in space and time, which may create variability in N dynamics as a result of shifts between heterotrophic and chemoautotrophic influences. To test this, we measured spatial and temporal variation in concentrations and net uptake of dissolved organic nitrogen (DON), ammonium (NH4+), and nitrate (NO3−) along a 1.4-km boreal stream fed by 4 discrete groundwater inflow zones. We also performed constant rate additions of NH4+, with and without acetate, to test the influence of labile DOC availability on N cycling. Groundwater N supply did not drive spatial patterns in N concentrations. However, we observed high rates of net NH4+ uptake at the sub-reach with the greatest groundwater DOC inputs, whereas net nitrification occurred where such inputs were negligible. At the reach scale, net DON and NH4+ uptake increased with greater groundwater discharge, DOC∶DIN, and ecosystem respiration, whereas net nitrification increased with greater DOC aromaticity. Finally, constant rate additions showed that, under increased DOC availability, NH4+ uptake increased 2×, whereas the proportion of NH4+ nitrified decreased from 42 to 15%. Together, these observations suggest that nitrification rivals heterotrophic uptake when aromatic DOC promotes heterotrophic carbon limitation. Discrete groundwater inflows and periods of elevated discharge can partially alleviate this limitation by supplying labile DOC from riparian soils. Hence, accounting for these land–water connections, over both time and space, is critical for understanding N dynamics in boreal streams.

@article{denfeld_heterogeneous_2020,
	title = {Heterogeneous {CO2} and {CH4} patterns across space and time in a small boreal lake},
	volume = {10},
	issn = {2044-2041},
	url = {https://doi.org/10.1080/20442041.2020.1787765},
	doi = {10.1080/20442041.2020.1787765},
	abstract = {Small boreal lakes emit large amounts of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Yet emissions of these greenhouse gases are variable in space and time, in part due to variable within-lake CO2 and CH4 concentrations. To determine the extent and the underlying drivers of this variation, we measured lake water CO2 and CH4 concentrations and estimated associated emissions using spatially discrete water samples collected every 2 weeks from a small boreal lake. On select dates, we also collected groundwater samples from the surrounding catchment. On average, groundwater draining a connected peat mire complex had significantly higher CO2 and CH4 concentrations compared to waters draining forest on mineral soils. However, within the lake, only CH4 concentrations nearshore from the mire complex were significantly elevated. We observed little spatial variability in surface water CO2; however, bottom water CO2 in the pelagic zone was significantly higher than bottom waters at nearshore locations. Overall, temperature, precipitation, and thermal stratification explained temporal patterns of CO2 concentration, whereas hydrology (discharge and precipitation) best predicted the variation in CH4 concentration. Consistent with these different controls, the highest CO2 emission was related to lake turnover at the end of August while the highest CH4 emission was associated with precipitation events at the end of June. These results suggest that annual carbon emissions from small boreal lakes are influenced by temporal variation in weather conditions that regulate thermal stratification and trigger hydrologic land–water connections that supply gases from catchment soils to the lake.},
	number = {3},
	urldate = {2024-03-27},
	journal = {Inland Waters},
	author = {Denfeld, Blaize A. and Lupon, Anna and Sponseller, Ryan A. and Laudon, Hjalmar and Karlsson, Jan},
	month = jul,
	year = {2020},
	note = {Publisher: Taylor \& Francis
\_eprint: https://doi.org/10.1080/20442041.2020.1787765},
	keywords = {\#nosource, carbon dioxide, carbon emissions, groundwater, lakes, methane, mire},
	pages = {348--359},
}

Small boreal lakes emit large amounts of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Yet emissions of these greenhouse gases are variable in space and time, in part due to variable within-lake CO2 and CH4 concentrations. To determine the extent and the underlying drivers of this variation, we measured lake water CO2 and CH4 concentrations and estimated associated emissions using spatially discrete water samples collected every 2 weeks from a small boreal lake. On select dates, we also collected groundwater samples from the surrounding catchment. On average, groundwater draining a connected peat mire complex had significantly higher CO2 and CH4 concentrations compared to waters draining forest on mineral soils. However, within the lake, only CH4 concentrations nearshore from the mire complex were significantly elevated. We observed little spatial variability in surface water CO2; however, bottom water CO2 in the pelagic zone was significantly higher than bottom waters at nearshore locations. Overall, temperature, precipitation, and thermal stratification explained temporal patterns of CO2 concentration, whereas hydrology (discharge and precipitation) best predicted the variation in CH4 concentration. Consistent with these different controls, the highest CO2 emission was related to lake turnover at the end of August while the highest CH4 emission was associated with precipitation events at the end of June. These results suggest that annual carbon emissions from small boreal lakes are influenced by temporal variation in weather conditions that regulate thermal stratification and trigger hydrologic land–water connections that supply gases from catchment soils to the lake.

@article{vachon_methane_2020,
	title = {Methane emission offsets carbon dioxide uptake in a small productive lake},
	volume = {5},
	copyright = {© 2020 The Authors. Limnology and Oceanography Letters published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10161},
	doi = {10.1002/lol2.10161},
	abstract = {Here, we investigate the importance of net CH4 production and emissions in the carbon (C) budget of a small productive lake by monitoring CH4, CO2, and O2 for two consecutive years. During the study period, the lake was mostly a net emitter of both CH4 and CO2, while showing positive net ecosystem production. The analyses suggest that during the whole study period, 32\% ± 26\% of C produced by net ecosystem production was ultimately converted to CH4 and emitted to the atmosphere. When converted to global warming potential, CH4 emission (in CO2 equivalents) was about 3–10 times higher than CO2 removal from in-lake net ecosystem production over 100-yr and 20-yr time frames, respectively. Although more work in similar systems is needed to generalize these findings, our results provide evidence of the important greenhouse gas imbalance in human-impacted aquatic systems.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography Letters},
	author = {Vachon, Dominic and Langenegger, Timon and Donis, Daphne and Beaubien, Stan E. and McGinnis, Daniel F.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10161},
	keywords = {\#nosource},
	pages = {384--392},
}

Here, we investigate the importance of net CH4 production and emissions in the carbon (C) budget of a small productive lake by monitoring CH4, CO2, and O2 for two consecutive years. During the study period, the lake was mostly a net emitter of both CH4 and CO2, while showing positive net ecosystem production. The analyses suggest that during the whole study period, 32% ± 26% of C produced by net ecosystem production was ultimately converted to CH4 and emitted to the atmosphere. When converted to global warming potential, CH4 emission (in CO2 equivalents) was about 3–10 times higher than CO2 removal from in-lake net ecosystem production over 100-yr and 20-yr time frames, respectively. Although more work in similar systems is needed to generalize these findings, our results provide evidence of the important greenhouse gas imbalance in human-impacted aquatic systems.

@article{sundqvist_responses_2020,
	title = {Responses of tundra plant community carbon flux to experimental warming, dominant species removal and elevation},
	volume = {34},
	copyright = {© 2020 The Authors. Functional Ecology published by John Wiley \& Sons Ltd on behalf of British Ecological Society},
	issn = {1365-2435},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13567},
	doi = {10.1111/1365-2435.13567},
	abstract = {Rising temperatures can influence ecosystem processes both directly and indirectly, through effects on plant species and communities. An improved understanding of direct versus indirect effects of warming on ecosystem processes is needed for robust predictions of the impacts of climate change on terrestrial ecosystem carbon (C) dynamics. To explore potential direct and indirect effects of warming on C dynamics in arctic tundra heath, we established a warming (open top chambers) and dominant plant species (Empetrum hermaphroditum Hagerup) removal experiment at a high and low elevation site. We measured the individual and interactive effects of warming, dominant species removal and elevation on plant species cover, the normalized difference vegetation index (NDVI), leaf area index (LAI), temperature, soil moisture and instantaneous net ecosystem CO2 exchange. We hypothesized that ecosystems would be stronger CO2 sinks at the low elevation site, and that warming and species removal would weaken the CO2 sink because warming should increase ecosystem respiration (ER) and species removal should reduce gross primary productivity (GPP). Furthermore, we hypothesized that warming and species removal would have the greatest impact on processes at the high elevation where site temperature should be most limiting and dominant species may buffer the overall community to environmental stress more compared to the low elevation site where plants are more likely to compete with the dominant species. The instantaneous CO2 flux, which reflected a weak CO2 sink, was similar at both elevations. Neither experimental warming nor dominant species removal significantly changed GPP or instantaneous net ecosystem CO2 exchange even though species removal significantly reduced ER, NDVI and LAI. Our results show that even the loss of dominant plant species may not result in significant landscape-scale responses of net ecosystem CO2 exchange to warming. They also show that NDVI and LAI may be limited in their ability to predict changes in GPP in these tundra heaths systems. Our study highlights the need for more detailed vegetation analyses and ground-truthed measurements in order to accurately predict direct and indirect impacts of climatic change on ecosystem C dynamics. A free Plain Language Summary can be found within the Supporting Information of this article.},
	language = {en},
	number = {7},
	urldate = {2024-03-27},
	journal = {Functional Ecology},
	author = {Sundqvist, Maja K. and Sanders, Nathan J. and Dorrepaal, Ellen and Lindén, Elin and Metcalfe, Daniel B. and Newman, Gregory S. and Olofsson, Johan and Wardle, David A. and Classen, Aimée T.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.13567},
	keywords = {\#nosource, carbon, ecosystem respiration, global warming, gross primary productivity, leaf area index, normalized difference vegetation index, plant–plant interactions},
	pages = {1497--1506},
}

Rising temperatures can influence ecosystem processes both directly and indirectly, through effects on plant species and communities. An improved understanding of direct versus indirect effects of warming on ecosystem processes is needed for robust predictions of the impacts of climate change on terrestrial ecosystem carbon (C) dynamics. To explore potential direct and indirect effects of warming on C dynamics in arctic tundra heath, we established a warming (open top chambers) and dominant plant species (Empetrum hermaphroditum Hagerup) removal experiment at a high and low elevation site. We measured the individual and interactive effects of warming, dominant species removal and elevation on plant species cover, the normalized difference vegetation index (NDVI), leaf area index (LAI), temperature, soil moisture and instantaneous net ecosystem CO2 exchange. We hypothesized that ecosystems would be stronger CO2 sinks at the low elevation site, and that warming and species removal would weaken the CO2 sink because warming should increase ecosystem respiration (ER) and species removal should reduce gross primary productivity (GPP). Furthermore, we hypothesized that warming and species removal would have the greatest impact on processes at the high elevation where site temperature should be most limiting and dominant species may buffer the overall community to environmental stress more compared to the low elevation site where plants are more likely to compete with the dominant species. The instantaneous CO2 flux, which reflected a weak CO2 sink, was similar at both elevations. Neither experimental warming nor dominant species removal significantly changed GPP or instantaneous net ecosystem CO2 exchange even though species removal significantly reduced ER, NDVI and LAI. Our results show that even the loss of dominant plant species may not result in significant landscape-scale responses of net ecosystem CO2 exchange to warming. They also show that NDVI and LAI may be limited in their ability to predict changes in GPP in these tundra heaths systems. Our study highlights the need for more detailed vegetation analyses and ground-truthed measurements in order to accurately predict direct and indirect impacts of climatic change on ecosystem C dynamics. A free Plain Language Summary can be found within the Supporting Information of this article.

@article{sjoberg_hot_2020,
	title = {Hot trends and impact in permafrost science},
	volume = {31},
	copyright = {© 2020 The Authors. Permafrost and Periglacial Processes published by John Wiley \& Sons Ltd},
	issn = {1099-1530},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ppp.2047},
	doi = {10.1002/ppp.2047},
	abstract = {An increased interest in Arctic environments, mainly due to climate change, has changed the conditions for permafrost research in recent years. This change has been accompanied by a global increase in scientific publications, as well as a trend towards open access publications. We have analyzed abstracts, titles and keywords for publications on permafrost from 1998 to 2017 to identify developments (topics, impact and collaboration) in the field of permafrost research in light of these changes. Furthermore, to understand how scientists build on and are inspired by each other's work, we have (a) developed citation networks from scientific publications on permafrost and (b) conducted an online survey on inspiration in permafrost science. Our results show an almost 400\% increase in publications containing the word permafrost in the title, keywords or abstract over the study period, and a strong increase in climate-change-related research in terms of publications and citations. Survey respondents (n = 122) find inspiration not only in scientific journal publications, but to a large extent in books and public outreach materials. We argue that this increase in global-scope issues (i.e., climate change) complementing core permafrost research has provided new incentives for international collaborations and wider communication efforts.},
	language = {en},
	number = {4},
	urldate = {2024-03-27},
	journal = {Permafrost and Periglacial Processes},
	author = {Sjöberg, Ylva and Siewert, Matthias B. and Rudy, Ashley C.A. and Paquette, Michel and Bouchard, Frédéric and Malenfant-Lepage, Julie and Fritz, Michael},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.2047},
	keywords = {\#nosource, Arctic, bibliometrics, climate change, inspiration, open access, publication trends, science communication},
	pages = {461--471},
}

An increased interest in Arctic environments, mainly due to climate change, has changed the conditions for permafrost research in recent years. This change has been accompanied by a global increase in scientific publications, as well as a trend towards open access publications. We have analyzed abstracts, titles and keywords for publications on permafrost from 1998 to 2017 to identify developments (topics, impact and collaboration) in the field of permafrost research in light of these changes. Furthermore, to understand how scientists build on and are inspired by each other's work, we have (a) developed citation networks from scientific publications on permafrost and (b) conducted an online survey on inspiration in permafrost science. Our results show an almost 400% increase in publications containing the word permafrost in the title, keywords or abstract over the study period, and a strong increase in climate-change-related research in terms of publications and citations. Survey respondents (n = 122) find inspiration not only in scientific journal publications, but to a large extent in books and public outreach materials. We argue that this increase in global-scope issues (i.e., climate change) complementing core permafrost research has provided new incentives for international collaborations and wider communication efforts.

@article{siewert_scale-dependency_2020,
	title = {Scale-dependency of {Arctic} ecosystem properties revealed by {UAV}},
	volume = {15},
	issn = {1748-9326},
	url = {https://dx.doi.org/10.1088/1748-9326/aba20b},
	doi = {10.1088/1748-9326/aba20b},
	abstract = {In the face of climate change, it is important to estimate changes in key ecosystem properties such as plant biomass and gross primary productivity (GPP). Ground truth estimates and especially experiments are performed at small spatial scales (0.01–1 m2) and scaled up using coarse scale satellite remote sensing products. This will lead to a scaling bias for non-linearly related properties in heterogeneous environments when the relationships are not developed at the same spatial scale as the remote sensing products. We show that unmanned aerial vehicles (UAVs) can reliably measure normalized difference vegetation index (NDVI) at centimeter resolution even in highly heterogeneous Arctic tundra terrain. This reveals that this scaling bias increases most at very fine resolution, but UAVs can overcome this by generating remote sensing products at the same scales as ecological changes occur. Using ground truth data generated at 0.0625 m2 and 1 m2 with Landsat 30 m scale satellite imagery the resulting underestimation is large (8.9\%–17.0\% for biomass and 5.0\%–9.7\% for GPP600) and of a magnitude comparable to the expected effects of decades of climate change. Methods to correct this upscaling bias exist but rely on sub-pixel information. Our data shows that this scale-dependency will vary strongly between areas and across seasons, making it hard to derive generalized functions compensating for it. This is particularly relevant to Arctic greening with a predominantly heterogeneous land cover, strong seasonality and much experimental research at sub-meter scale, but also applies to other heterogeneous landscapes. These results demonstrate the value of UAVs for satellite validation. UAVs can bridge between plot scale used in ecological field investigations and coarse scale in satellite monitoring relevant for Earth System Models. Since future climate changes are expected to alter landscape heterogeneity, seasonally updated UAV imagery will be an essential tool to correctly predict landscape-scale changes in ecosystem properties.},
	language = {en},
	number = {9},
	urldate = {2024-03-27},
	journal = {Environmental Research Letters},
	author = {Siewert, Matthias B. and Olofsson, Johan},
	month = aug,
	year = {2020},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {094030},
}

In the face of climate change, it is important to estimate changes in key ecosystem properties such as plant biomass and gross primary productivity (GPP). Ground truth estimates and especially experiments are performed at small spatial scales (0.01–1 m2) and scaled up using coarse scale satellite remote sensing products. This will lead to a scaling bias for non-linearly related properties in heterogeneous environments when the relationships are not developed at the same spatial scale as the remote sensing products. We show that unmanned aerial vehicles (UAVs) can reliably measure normalized difference vegetation index (NDVI) at centimeter resolution even in highly heterogeneous Arctic tundra terrain. This reveals that this scaling bias increases most at very fine resolution, but UAVs can overcome this by generating remote sensing products at the same scales as ecological changes occur. Using ground truth data generated at 0.0625 m2 and 1 m2 with Landsat 30 m scale satellite imagery the resulting underestimation is large (8.9%–17.0% for biomass and 5.0%–9.7% for GPP600) and of a magnitude comparable to the expected effects of decades of climate change. Methods to correct this upscaling bias exist but rely on sub-pixel information. Our data shows that this scale-dependency will vary strongly between areas and across seasons, making it hard to derive generalized functions compensating for it. This is particularly relevant to Arctic greening with a predominantly heterogeneous land cover, strong seasonality and much experimental research at sub-meter scale, but also applies to other heterogeneous landscapes. These results demonstrate the value of UAVs for satellite validation. UAVs can bridge between plot scale used in ecological field investigations and coarse scale in satellite monitoring relevant for Earth System Models. Since future climate changes are expected to alter landscape heterogeneity, seasonally updated UAV imagery will be an essential tool to correctly predict landscape-scale changes in ecosystem properties.

@article{rousk_responses_2020,
	title = {The responses of moss-associated nitrogen fixation and belowground microbial community to chronic {Mo} and {P} supplements in subarctic dry heaths},
	volume = {451},
	issn = {1573-5036},
	url = {https://doi.org/10.1007/s11104-020-04492-6},
	doi = {10.1007/s11104-020-04492-6},
	abstract = {Although nitrogen (N) fixation by moss-associated bacteria is the main source of new N in N-limited ecosystems like arctic tundra, we do not know which nutrient, molybdenum (Mo) or phosphorus (P), is rate-limiting for sustaining this process in the long-term. Further, how moss-associated N2 fixation impacts the belowground microbial regulation of decomposition remains unresolved.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Plant and Soil},
	author = {Rousk, Kathrin and Rousk, Johannes},
	month = jun,
	year = {2020},
	keywords = {\#nosource, Bryophytes, Cyanobacteria, Nitrogen fixation, Nutrient limitation, Soil fungal and bacterial growth},
	pages = {261--276},
}

Although nitrogen (N) fixation by moss-associated bacteria is the main source of new N in N-limited ecosystems like arctic tundra, we do not know which nutrient, molybdenum (Mo) or phosphorus (P), is rate-limiting for sustaining this process in the long-term. Further, how moss-associated N2 fixation impacts the belowground microbial regulation of decomposition remains unresolved.

@article{parker_rhizosphere_2020,
	title = {Rhizosphere allocation by canopy-forming species dominates soil {CO2} efflux in a subarctic landscape},
	volume = {227},
	copyright = {© 2020 The Authors. New Phytologist © 2020 New Phytologist Trust},
	issn = {1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.16573},
	doi = {10.1111/nph.16573},
	abstract = {In arctic ecosystems, climate change has increased plant productivity. As arctic carbon (C) stocks predominantly are located belowground, the effects of greater plant productivity on soil C storage will significantly determine the net sink/source potential of these ecosystems, but vegetation controls on soil CO2 efflux remain poorly resolved. In order to identify the role of canopy-forming species in belowground C dynamics, we conducted a girdling experiment with plots distributed across 1 km2 of treeline birch (Betula pubescens) forest and willow (Salix lapponum) patches in northern Sweden and quantified the contribution of canopy vegetation to soil CO2 fluxes and belowground productivity. Girdling birches reduced total soil CO2 efflux in the peak growing season by 53\%, which is double the expected amount, given that trees contribute only half of the total leaf area in the forest. Root and mycorrhizal mycelial production also decreased substantially. At peak season, willow shrubs contributed 38\% to soil CO2 efflux in their patches. Our findings indicate that C, recently fixed by trees and tall shrubs, makes a substantial contribution to soil respiration. It is critically important that these processes are taken into consideration in the context of a greening arctic because productivity and ecosystem C sequestration are not synonymous.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {New Phytologist},
	author = {Parker, Thomas C. and Clemmensen, Karina E. and Friggens, Nina L. and Hartley, Iain P. and Johnson, David and Lindahl, Björn D. and Olofsson, Johan and Siewert, Matthias B. and Street, Lorna E. and Subke, Jens-Arne and Wookey, Philip A.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.16573},
	keywords = {\#nosource, Arctic, ectomycorrhizal fungi, girdling, rhizosphere, shrub expansion, soil CO2 efflux, treeline},
	pages = {1818--1830},
}

In arctic ecosystems, climate change has increased plant productivity. As arctic carbon (C) stocks predominantly are located belowground, the effects of greater plant productivity on soil C storage will significantly determine the net sink/source potential of these ecosystems, but vegetation controls on soil CO2 efflux remain poorly resolved. In order to identify the role of canopy-forming species in belowground C dynamics, we conducted a girdling experiment with plots distributed across 1 km2 of treeline birch (Betula pubescens) forest and willow (Salix lapponum) patches in northern Sweden and quantified the contribution of canopy vegetation to soil CO2 fluxes and belowground productivity. Girdling birches reduced total soil CO2 efflux in the peak growing season by 53%, which is double the expected amount, given that trees contribute only half of the total leaf area in the forest. Root and mycorrhizal mycelial production also decreased substantially. At peak season, willow shrubs contributed 38% to soil CO2 efflux in their patches. Our findings indicate that C, recently fixed by trees and tall shrubs, makes a substantial contribution to soil respiration. It is critically important that these processes are taken into consideration in the context of a greening arctic because productivity and ecosystem C sequestration are not synonymous.

@article{olid_decade_2020,
	title = {Decade of experimental permafrost thaw reduces turnover of young carbon and increases losses of old carbon, without affecting the net carbon balance},
	volume = {26},
	copyright = {© 2020 The Authors. Global Change Biology published by John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15283},
	doi = {10.1111/gcb.15283},
	abstract = {Thicker snowpacks and their insulation effects cause winter-warming and invoke thaw of permafrost ecosystems. Temperature-dependent decomposition of previously frozen carbon (C) is currently considered one of the strongest feedbacks between the Arctic and the climate system, but the direction and magnitude of the net C balance remains uncertain. This is because winter effects are rarely integrated with C fluxes during the snow-free season and because predicting the net C balance from both surface processes and thawing deep layers remains challenging. In this study, we quantified changes in the long-term net C balance (net ecosystem production) in a subarctic peat plateau subjected to 10 years of experimental winter-warming. By combining 210Pb and 14Cdating of peat cores with peat growth models, we investigated thawing effects on year-round primary production and C losses through respiration and leaching from both shallow and deep peat layers. Winter-warming and permafrost thaw had no effect on the net C balance, but strongly affected gross C fluxes. Carbon losses through decomposition from the upper peat were reduced as thawing of permafrost induced surface subsidence and subsequent waterlogging. However, primary production was also reduced likely due to a strong decline in bryophytes cover while losses from the old C pool almost tripled, caused by the deepened active layer. Our findings highlight the need to estimate long-term responses of whole-year production and decomposition processes to thawing, both in shallow and deep soil layers, as they may contrast and lead to unexpected net effects on permafrost C storage.},
	language = {en},
	number = {10},
	urldate = {2024-03-27},
	journal = {Global Change Biology},
	author = {Olid, Carolina and Klaminder, Jonatan and Monteux, Sylvain and Johansson, Margareta and Dorrepaal, Ellen},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15283},
	keywords = {\#nosource, age–depth modelling, carbon accumulation, carbon cycle, climate change, decomposition, peat dating, permafrost thawing, production, snow addition, winter-warming},
	pages = {5886--5898},
}

Thicker snowpacks and their insulation effects cause winter-warming and invoke thaw of permafrost ecosystems. Temperature-dependent decomposition of previously frozen carbon (C) is currently considered one of the strongest feedbacks between the Arctic and the climate system, but the direction and magnitude of the net C balance remains uncertain. This is because winter effects are rarely integrated with C fluxes during the snow-free season and because predicting the net C balance from both surface processes and thawing deep layers remains challenging. In this study, we quantified changes in the long-term net C balance (net ecosystem production) in a subarctic peat plateau subjected to 10 years of experimental winter-warming. By combining 210Pb and 14Cdating of peat cores with peat growth models, we investigated thawing effects on year-round primary production and C losses through respiration and leaching from both shallow and deep peat layers. Winter-warming and permafrost thaw had no effect on the net C balance, but strongly affected gross C fluxes. Carbon losses through decomposition from the upper peat were reduced as thawing of permafrost induced surface subsidence and subsequent waterlogging. However, primary production was also reduced likely due to a strong decline in bryophytes cover while losses from the old C pool almost tripled, caused by the deepened active layer. Our findings highlight the need to estimate long-term responses of whole-year production and decomposition processes to thawing, both in shallow and deep soil layers, as they may contrast and lead to unexpected net effects on permafrost C storage.

@article{lembrechts_soiltemp_2020,
	title = {{SoilTemp}: {A} global database of near-surface temperature},
	volume = {26},
	copyright = {© 2020 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	shorttitle = {{SoilTemp}},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15123},
	doi = {10.1111/gcb.15123},
	abstract = {Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long-term average thermal conditions at coarse spatial resolutions only. Hence, many climate-forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold-air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free-air temperatures, microclimatic ground and near-surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near-surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes.},
	language = {en},
	number = {11},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Lembrechts, Jonas J. and Aalto, Juha and Ashcroft, Michael B. and De Frenne, Pieter and Kopecký, Martin and Lenoir, Jonathan and Luoto, Miska and Maclean, Ilya M. D. and Roupsard, Olivier and Fuentes-Lillo, Eduardo and García, Rafael A. and Pellissier, Loïc and Pitteloud, Camille and Alatalo, Juha M. and Smith, Stuart W. and Björk, Robert G. and Muffler, Lena and Ratier Backes, Amanda and Cesarz, Simone and Gottschall, Felix and Okello, Joseph and Urban, Josef and Plichta, Roman and Svátek, Martin and Phartyal, Shyam S. and Wipf, Sonja and Eisenhauer, Nico and Pușcaș, Mihai and Turtureanu, Pavel D. and Varlagin, Andrej and Dimarco, Romina D. and Jump, Alistair S. and Randall, Krystal and Dorrepaal, Ellen and Larson, Keith and Walz, Josefine and Vitale, Luca and Svoboda, Miroslav and Finger Higgens, Rebecca and Halbritter, Aud H. and Curasi, Salvatore R. and Klupar, Ian and Koontz, Austin and Pearse, William D. and Simpson, Elizabeth and Stemkovski, Michael and Jessen Graae, Bente and Vedel Sørensen, Mia and Høye, Toke T. and Fernández Calzado, M. Rosa and Lorite, Juan and Carbognani, Michele and Tomaselli, Marcello and Forte, T'ai G. W. and Petraglia, Alessandro and Haesen, Stef and Somers, Ben and Van Meerbeek, Koenraad and Björkman, Mats P. and Hylander, Kristoffer and Merinero, Sonia and Gharun, Mana and Buchmann, Nina and Dolezal, Jiri and Matula, Radim and Thomas, Andrew D. and Bailey, Joseph J. and Ghosn, Dany and Kazakis, George and de Pablo, Miguel A. and Kemppinen, Julia and Niittynen, Pekka and Rew, Lisa and Seipel, Tim and Larson, Christian and Speed, James D. M. and Ardö, Jonas and Cannone, Nicoletta and Guglielmin, Mauro and Malfasi, Francesco and Bader, Maaike Y. and Canessa, Rafaella and Stanisci, Angela and Kreyling, Juergen and Schmeddes, Jonas and Teuber, Laurenz and Aschero, Valeria and Čiliak, Marek and Máliš, František and De Smedt, Pallieter and Govaert, Sanne and Meeussen, Camille and Vangansbeke, Pieter and Gigauri, Khatuna and Lamprecht, Andrea and Pauli, Harald and Steinbauer, Klaus and Winkler, Manuela and Ueyama, Masahito and Nuñez, Martin A. and Ursu, Tudor-Mihai and Haider, Sylvia and Wedegärtner, Ronja E. M. and Smiljanic, Marko and Trouillier, Mario and Wilmking, Martin and Altman, Jan and Brůna, Josef and Hederová, Lucia and Macek, Martin and Man, Matěj and Wild, Jan and Vittoz, Pascal and Pärtel, Meelis and Barančok, Peter and Kanka, Róbert and Kollár, Jozef and Palaj, Andrej and Barros, Agustina and Mazzolari, Ana C. and Bauters, Marijn and Boeckx, Pascal and Benito Alonso, José-Luis and Zong, Shengwei and Di Cecco, Valter and Sitková, Zuzana and Tielbörger, Katja and van den Brink, Liesbeth and Weigel, Robert and Homeier, Jürgen and Dahlberg, C. Johan and Medinets, Sergiy and Medinets, Volodymyr and De Boeck, Hans J. and Portillo-Estrada, Miguel and Verryckt, Lore T. and Milbau, Ann and Daskalova, Gergana N. and Thomas, Haydn J. D. and Myers-Smith, Isla H. and Blonder, Benjamin and Stephan, Jörg G. and Descombes, Patrice and Zellweger, Florian and Frei, Esther R. and Heinesch, Bernard and Andrews, Christopher and Dick, Jan and Siebicke, Lukas and Rocha, Adrian and Senior, Rebecca A. and Rixen, Christian and Jimenez, Juan J. and Boike, Julia and Pauchard, Aníbal and Scholten, Thomas and Scheffers, Brett and Klinges, David and Basham, Edmund W. and Zhang, Jian and Zhang, Zhaochen and Géron, Charly and Fazlioglu, Fatih and Candan, Onur and Sallo Bravo, Jhonatan and Hrbacek, Filip and Laska, Kamil and Cremonese, Edoardo and Haase, Peter and Moyano, Fernando E. and Rossi, Christian and Nijs, Ivan},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15123},
	keywords = {\#nosource, climate change, database, ecosystem processes, microclimate, soil climate, species distributions, temperature, topoclimate},
	pages = {6616--6629},
}

Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long-term average thermal conditions at coarse spatial resolutions only. Hence, many climate-forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold-air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free-air temperatures, microclimatic ground and near-surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near-surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes.

@article{leander_old_2020,
	title = {The old and the new: evaluating performance of acoustic telemetry systems in tracking migrating {Atlantic} salmon ({Salmo} salar) smolt and {European} eel ({Anguilla} anguilla) around hydropower facilities},
	volume = {77},
	issn = {0706-652X},
	shorttitle = {The old and the new},
	url = {https://cdnsciencepub.com/doi/abs/10.1139/cjfas-2019-0058},
	doi = {10.1139/cjfas-2019-0058},
	abstract = {Acoustic telemetry represents the state-of-the-art technology for monitoring behaviour of aquatic organisms in the wild. Yet, the performance of different systems is rarely evaluated across species and environments. In this study, we evaluate two different acoustic telemetry systems, a commonly used analogue pulse-position-modulation-based system (VEMCO PPM) and a newly developed high-residency digital binary phase shift key-based system (VEMCO HR2), in ability to track downstream migrating Atlantic salmon smolt (Salmo salar) and European eel (Anguilla anguilla) around hydropower facilities. High-precision GPS were used to evaluate precision and accuracy of hyperbolically positioned data derived from each system. The PPM-based system had higher detection range than HR2 and generated more positions per transmission for eels migrating close to bottom than for surface-oriented salmon smolts. HR2 generated tenfold more positions per time unit than PPM, were less sensitive to noise, achieved submetre positional precision, and were considerably more accurate than PPM-derived positions after filtering. HR2 was deemed more capable than PPM in fine-scale positioning at moderate distances at hydropower facilities.},
	number = {1},
	urldate = {2024-03-26},
	journal = {Canadian Journal of Fisheries and Aquatic Sciences},
	author = {Leander, Johan and Klaminder, Jonatan and Jonsson, Micael and Brodin, Tomas and Leonardsson, Kjell and Hellström, Gustav},
	month = jan,
	year = {2020},
	note = {Publisher: NRC Research Press},
	keywords = {\#nosource},
	pages = {177--187},
}

Acoustic telemetry represents the state-of-the-art technology for monitoring behaviour of aquatic organisms in the wild. Yet, the performance of different systems is rarely evaluated across species and environments. In this study, we evaluate two different acoustic telemetry systems, a commonly used analogue pulse-position-modulation-based system (VEMCO PPM) and a newly developed high-residency digital binary phase shift key-based system (VEMCO HR2), in ability to track downstream migrating Atlantic salmon smolt (Salmo salar) and European eel (Anguilla anguilla) around hydropower facilities. High-precision GPS were used to evaluate precision and accuracy of hyperbolically positioned data derived from each system. The PPM-based system had higher detection range than HR2 and generated more positions per transmission for eels migrating close to bottom than for surface-oriented salmon smolts. HR2 generated tenfold more positions per time unit than PPM, were less sensitive to noise, achieved submetre positional precision, and were considerably more accurate than PPM-derived positions after filtering. HR2 was deemed more capable than PPM in fine-scale positioning at moderate distances at hydropower facilities.

@article{kristensen_background_2020,
	title = {Background insect herbivory increases with local elevation but makes minor contribution to element cycling along natural gradients in the {Subarctic}},
	volume = {10},
	copyright = {© 2020 The Authors. Ecology and Evolution published by John Wiley \& Sons Ltd},
	issn = {2045-7758},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ece3.6803},
	doi = {10.1002/ece3.6803},
	abstract = {Herbivores can exert major controls over biogeochemical cycling. As invertebrates are highly sensitive to temperature shifts (ectothermal), the abundances of insects in high-latitude systems, where climate warming is rapid, is expected to increase. In subarctic mountain birch forests, research has focussed on geometrid moth outbreaks, while the contribution of background insect herbivory (BIH) to elemental cycling is poorly constrained. In northern Sweden, we estimated BIH along 9 elevational gradients distributed across a gradient in regional elevation, temperature, and precipitation to allow evaluation of consistency in local versus regional variation. We converted foliar loss via BIH to fluxes of C, nitrogen (N), and phosphorus (P) from the birch canopy to the soil to compare with other relevant soil inputs of the same elements and assessed different abiotic and biotic drivers of the observed variability. We found that leaf area loss due to BIH was 1.6\% on average. This is comparable to estimates from tundra, but considerably lower than ecosystems at lower latitudes. The C, N, and P fluxes from canopy to soil associated with BIH were 1–2 orders of magnitude lower than the soil input from senesced litter and external nutrient sources such as biological N fixation, atmospheric deposition of N, and P weathering estimated from the literature. Despite the minor contribution to overall elemental cycling in subarctic birch forests, the higher quality and earlier timing of the input of herbivore deposits to soils compared to senesced litter may make this contribution disproportionally important for various ecosystem functions. BIH increased significantly with leaf N content as well as local elevation along each transect, yet showed no significant relationship with temperature or humidity, nor the commonly used temperature proxy, absolute elevation. The lack of consistency between the local and regional elevational trends calls for caution when using elevation gradients as climate proxies.},
	language = {en},
	number = {20},
	urldate = {2024-03-26},
	journal = {Ecology and Evolution},
	author = {Kristensen, Jeppe A. and Michelsen, Anders and Metcalfe, Daniel B.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.6803},
	keywords = {\#nosource, Subarctic mountain birch forest, carbon cycling, fast cycle versus slow cycle, insect herbivory, nutrient cycling, space-for-time substitution},
	pages = {11684--11698},
}

Herbivores can exert major controls over biogeochemical cycling. As invertebrates are highly sensitive to temperature shifts (ectothermal), the abundances of insects in high-latitude systems, where climate warming is rapid, is expected to increase. In subarctic mountain birch forests, research has focussed on geometrid moth outbreaks, while the contribution of background insect herbivory (BIH) to elemental cycling is poorly constrained. In northern Sweden, we estimated BIH along 9 elevational gradients distributed across a gradient in regional elevation, temperature, and precipitation to allow evaluation of consistency in local versus regional variation. We converted foliar loss via BIH to fluxes of C, nitrogen (N), and phosphorus (P) from the birch canopy to the soil to compare with other relevant soil inputs of the same elements and assessed different abiotic and biotic drivers of the observed variability. We found that leaf area loss due to BIH was 1.6% on average. This is comparable to estimates from tundra, but considerably lower than ecosystems at lower latitudes. The C, N, and P fluxes from canopy to soil associated with BIH were 1–2 orders of magnitude lower than the soil input from senesced litter and external nutrient sources such as biological N fixation, atmospheric deposition of N, and P weathering estimated from the literature. Despite the minor contribution to overall elemental cycling in subarctic birch forests, the higher quality and earlier timing of the input of herbivore deposits to soils compared to senesced litter may make this contribution disproportionally important for various ecosystem functions. BIH increased significantly with leaf N content as well as local elevation along each transect, yet showed no significant relationship with temperature or humidity, nor the commonly used temperature proxy, absolute elevation. The lack of consistency between the local and regional elevational trends calls for caution when using elevation gradients as climate proxies.

@article{klaus_challenges_2020,
	title = {Challenges of predicting gas transfer velocity from wind measurements over global lakes},
	volume = {82},
	issn = {1420-9055},
	url = {https://doi.org/10.1007/s00027-020-00729-9},
	doi = {10.1007/s00027-020-00729-9},
	abstract = {Estimating air–water gas transfer velocities (k) is integral to understand biogeochemical and ecological processes in aquatic systems. In lakes, k is commonly predicted using wind-based empirical models, however, their predictive performance under conditions that differ from their original calibration remains largely unassessed. Here, we collected 2222 published k estimates derived from various methods in 46 globally distributed lakes to (1) evaluate the predictions of a selection of six available wind-speed based k models for lakes and (2) explore and develop new empirical models to predict k over global lakes. We found that selected k models generally performed poorly in predicting k in lakes. Model predictions were more accurate than simply assuming a mean k in only 2–39\% of all lakes, however, we could not identify with confidence the specific conditions in which some models outperformed others. We developed new wind-based models in which additional variables describing the spatial coverage of k estimates and the lake size and shape had a significant effect on the wind speed-k relationship. Although these new models did not fit the global dataset significantly better than previous k models, they generate overall less biased predictions for global lakes. We further provide explicit estimates of prediction errors that integrate methodological and lake-specific uncertainties. Our results highlight the potential limits when using wind-based models to predict k across lakes and urge scientists to properly account for prediction errors, or measure k directly in the field whenever possible.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Aquatic Sciences},
	author = {Klaus, Marcus and Vachon, Dominic},
	month = may,
	year = {2020},
	keywords = {\#nosource, Air–water gas exchange, Lake gas flux, Model assessment, Reaeration, Wind speed, k 600},
	pages = {53},
}

Estimating air–water gas transfer velocities (k) is integral to understand biogeochemical and ecological processes in aquatic systems. In lakes, k is commonly predicted using wind-based empirical models, however, their predictive performance under conditions that differ from their original calibration remains largely unassessed. Here, we collected 2222 published k estimates derived from various methods in 46 globally distributed lakes to (1) evaluate the predictions of a selection of six available wind-speed based k models for lakes and (2) explore and develop new empirical models to predict k over global lakes. We found that selected k models generally performed poorly in predicting k in lakes. Model predictions were more accurate than simply assuming a mean k in only 2–39% of all lakes, however, we could not identify with confidence the specific conditions in which some models outperformed others. We developed new wind-based models in which additional variables describing the spatial coverage of k estimates and the lake size and shape had a significant effect on the wind speed-k relationship. Although these new models did not fit the global dataset significantly better than previous k models, they generate overall less biased predictions for global lakes. We further provide explicit estimates of prediction errors that integrate methodological and lake-specific uncertainties. Our results highlight the potential limits when using wind-based models to predict k across lakes and urge scientists to properly account for prediction errors, or measure k directly in the field whenever possible.

@article{jonsson_stand_2020,
	title = {Stand age and climate influence forest ecosystem service delivery and multifunctionality},
	volume = {15},
	issn = {1748-9326},
	url = {https://dx.doi.org/10.1088/1748-9326/abaf1c},
	doi = {10.1088/1748-9326/abaf1c},
	abstract = {We examine how levels of multiple ecosystem services (ESs) change with succession in forests with different tree species composition. More specifically we ask how ecosystem age interacts with environmental conditions to regulate ES delivery. Using the nationwide Swedish forest inventory, comprising boreal and temperate regions, we investigated how levels of six provisioning, regulating, recreational, and/or cultural forest ESs changed with forest age (10–185 years) in stands of different tree species composition. We also tested whether the number of ESs delivered (i.e. multifunctionality) changed substantially with stand age, using different threshold levels for ES delivery. Accounting for environmental conditions and stand properties, we found that levels of single ESs changed with stand age. Tree biomass production usually peaked in young to medium aged stands. In contrast, production of berries and game, and services related to biodiversity, were typically highest in old stands (120–185 years). Consistent with this strong temporal tradeoff, multifunctionality at lower threshold levels increased with stand age in most monocultures and mixtures, with the highest multifunctionality being reached somewhere between 100 and 185 years, depending on tree species composition. This was not evident for the highest threshold ES level (the top-20\%), however. Moreover, multifunctionality usually decreased with warmer climatic conditions, with the exception of spruce–pine–birch mixtures. Taken together, our results show that a reduced forest age, e.g. due to forestry targeting early harvest of stands, most likely would limit the delivery of several ESs valued by society and result in less multifunctional forests. To maintain the capacity of forests to deliver high levels of multiple ESs, the role of stand age and tree species composition should be considered in decisions on how to manage future forests.},
	language = {en},
	number = {9},
	urldate = {2024-03-26},
	journal = {Environmental Research Letters},
	author = {Jonsson, Micael and Bengtsson, Jan and Moen, Jon and Gamfeldt, Lars and Snäll, Tord},
	month = sep,
	year = {2020},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {0940a8},
}

We examine how levels of multiple ecosystem services (ESs) change with succession in forests with different tree species composition. More specifically we ask how ecosystem age interacts with environmental conditions to regulate ES delivery. Using the nationwide Swedish forest inventory, comprising boreal and temperate regions, we investigated how levels of six provisioning, regulating, recreational, and/or cultural forest ESs changed with forest age (10–185 years) in stands of different tree species composition. We also tested whether the number of ESs delivered (i.e. multifunctionality) changed substantially with stand age, using different threshold levels for ES delivery. Accounting for environmental conditions and stand properties, we found that levels of single ESs changed with stand age. Tree biomass production usually peaked in young to medium aged stands. In contrast, production of berries and game, and services related to biodiversity, were typically highest in old stands (120–185 years). Consistent with this strong temporal tradeoff, multifunctionality at lower threshold levels increased with stand age in most monocultures and mixtures, with the highest multifunctionality being reached somewhere between 100 and 185 years, depending on tree species composition. This was not evident for the highest threshold ES level (the top-20%), however. Moreover, multifunctionality usually decreased with warmer climatic conditions, with the exception of spruce–pine–birch mixtures. Taken together, our results show that a reduced forest age, e.g. due to forestry targeting early harvest of stands, most likely would limit the delivery of several ESs valued by society and result in less multifunctional forests. To maintain the capacity of forests to deliver high levels of multiple ESs, the role of stand age and tree species composition should be considered in decisions on how to manage future forests.

@article{jessen_mammalian_2020,
	title = {Mammalian herbivory shapes intraspecific trait responses to warmer climate and nutrient enrichment},
	volume = {26},
	copyright = {© 2020 The Authors. Global Change Biology published by John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15378},
	doi = {10.1111/gcb.15378},
	abstract = {Variation in intraspecific traits is one important mechanism that can allow plant species to respond to global changes. Understanding plant trait responses to environmental changes such as grazing patterns, nutrient enrichment and climate warming is, thus, essential for predicting the composition of future plant communities. We measured traits of eight common tundra species in a fully factorial field experiment with mammalian herbivore exclusion, fertilization, and passive warming, and assessed how trait responsiveness to the treatments was associated with abundance changes in those treatments. Herbivory exhibited the strongest impact on traits. Exclusion of herbivores increased vegetative plant height by 50\% and specific leaf area (SLA) by 19\%, and decreased foliar C:N by 11\%; fertilization and warming also increased height and SLA but to a smaller extent. Herbivory also modulated intraspecific height, SLA and foliar C:N responses to fertilization and warming, and these interactions were species-specific. Furthermore, herbivory affected how trait change translated into relative abundance change: increased height under warming and fertilization was more positively related to abundance change inside fences than in grazed plots. Our findings highlight the key role of mammalian herbivory when assessing intraspecific trait change in tundra and its consequences for plant performance under global changes.},
	language = {en},
	number = {12},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Jessen, Maria-Theresa and Kaarlejärvi, Elina and Olofsson, Johan and Eskelinen, Anu},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15378},
	keywords = {\#nosource, anthropogenic change, climate warming, grazing, herbivory, intraspecific trait plasticity, nutrient addition, open-top chamber, plant performance, reindeer, trait–environment relationship},
	pages = {6742--6752},
}

Variation in intraspecific traits is one important mechanism that can allow plant species to respond to global changes. Understanding plant trait responses to environmental changes such as grazing patterns, nutrient enrichment and climate warming is, thus, essential for predicting the composition of future plant communities. We measured traits of eight common tundra species in a fully factorial field experiment with mammalian herbivore exclusion, fertilization, and passive warming, and assessed how trait responsiveness to the treatments was associated with abundance changes in those treatments. Herbivory exhibited the strongest impact on traits. Exclusion of herbivores increased vegetative plant height by 50% and specific leaf area (SLA) by 19%, and decreased foliar C:N by 11%; fertilization and warming also increased height and SLA but to a smaller extent. Herbivory also modulated intraspecific height, SLA and foliar C:N responses to fertilization and warming, and these interactions were species-specific. Furthermore, herbivory affected how trait change translated into relative abundance change: increased height under warming and fertilization was more positively related to abundance change inside fences than in grazed plots. Our findings highlight the key role of mammalian herbivory when assessing intraspecific trait change in tundra and its consequences for plant performance under global changes.

@article{freeman_global_2020,
	title = {Global changes may be promoting a rise in select cyanobacteria in nutrient-poor northern lakes},
	volume = {26},
	copyright = {© 2020 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15189},
	doi = {10.1111/gcb.15189},
	abstract = {The interacting effects of global changes—including increased temperature, altered precipitation, reduced acidification and increased dissolved organic matter loads to lakes—are anticipated to create favourable environmental conditions for cyanobacteria in northern lakes. However, responses of cyanobacteria to these global changes are complex, if not contradictory. We hypothesized that absolute and relative biovolumes of cyanobacteria (both total and specific genera) are increasing in Swedish nutrient-poor lakes and that these increases are associated with global changes. We tested these hypotheses using data from 28 nutrient-poor Swedish lakes over 16 years (1998–2013). Increases in cyanobacteria relative biovolume were identified in 21\% of the study sites, primarily in the southeastern region of Sweden, and were composed mostly of increases from three specific genera: Merismopedia, Chroococcus and Dolichospermum. Taxon-specific changes were related to different environmental stressors; that is, increased surface water temperature favoured higher Merismopedia relative biovolume in low pH lakes with high nitrogen to phosphorus ratios, whereas acidification recovery was statistically related to increased relative biovolumes of Chroococcus and Dolichospermum. In addition, enhanced dissolved organic matter loads were identified as potential determinants of Chroococcus suppression and Dolichospermum promotion. Our findings highlight that specific genera of cyanobacteria benefit from different environmental changes. Our ability to predict the risk of cyanobacteria prevalence requires consideration of the environmental condition of a lake and the sensitivities of the cyanobacteria genera within the lake. Regional patterns may emerge due to spatial autocorrelations within and among lake history, rates and direction of environmental change and the niche space occupied by specific cyanobacteria.},
	language = {en},
	number = {9},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Freeman, Erika C. and Creed, Irena F. and Jones, Blake and Bergström, Ann-Kristin},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15189},
	keywords = {\#nosource, Climate change, Sweden, acidification recovery, browning, climate change, cyanobacteria, northern lakes},
	pages = {4966--4987},
}

The interacting effects of global changes—including increased temperature, altered precipitation, reduced acidification and increased dissolved organic matter loads to lakes—are anticipated to create favourable environmental conditions for cyanobacteria in northern lakes. However, responses of cyanobacteria to these global changes are complex, if not contradictory. We hypothesized that absolute and relative biovolumes of cyanobacteria (both total and specific genera) are increasing in Swedish nutrient-poor lakes and that these increases are associated with global changes. We tested these hypotheses using data from 28 nutrient-poor Swedish lakes over 16 years (1998–2013). Increases in cyanobacteria relative biovolume were identified in 21% of the study sites, primarily in the southeastern region of Sweden, and were composed mostly of increases from three specific genera: Merismopedia, Chroococcus and Dolichospermum. Taxon-specific changes were related to different environmental stressors; that is, increased surface water temperature favoured higher Merismopedia relative biovolume in low pH lakes with high nitrogen to phosphorus ratios, whereas acidification recovery was statistically related to increased relative biovolumes of Chroococcus and Dolichospermum. In addition, enhanced dissolved organic matter loads were identified as potential determinants of Chroococcus suppression and Dolichospermum promotion. Our findings highlight that specific genera of cyanobacteria benefit from different environmental changes. Our ability to predict the risk of cyanobacteria prevalence requires consideration of the environmental condition of a lake and the sensitivities of the cyanobacteria genera within the lake. Regional patterns may emerge due to spatial autocorrelations within and among lake history, rates and direction of environmental change and the niche space occupied by specific cyanobacteria.

@article{fork_dissolved_2020,
	title = {Dissolved organic matter regulates nutrient limitation and growth of benthic algae in northern lakes through interacting effects on nutrient and light availability},
	volume = {5},
	copyright = {© 2020 The Authors. Limnology and Oceanography Letters published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10166},
	doi = {10.1002/lol2.10166},
	abstract = {Widespread increases in dissolved organic matter (DOM) concentration across northern lakes can alter rates of primary production by increasing nutrient availability and decreasing light availability. These dual effects of DOM generate a unimodal relationship in pelagic primary production and primary producer biomass among lakes over a gradient of DOM concentration. However, the responses of benthic algae to variation in DOM loading are less clear because of their potential to access sediment nutrients. We tested algal production and nutrient limitation along a DOM gradient in northern Sweden. Without added nutrients, benthic algal production showed a unimodal relationship with DOM, similar to reported pelagic responses. Nutrient addition revealed widespread nitrogen limitation, with decreasing severity in lakes with higher DOM. Because the majority of northern Swedish lakes currently fall below the inflection point in this unimodal relationship, moderate increases in DOM have the potential to increase benthic primary production, particularly for epilithic algae.},
	language = {en},
	number = {6},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography Letters},
	author = {Fork, Megan L. and Karlsson, Jan and Sponseller, Ryan A.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10166},
	keywords = {\#nosource},
	pages = {417--424},
}

Widespread increases in dissolved organic matter (DOM) concentration across northern lakes can alter rates of primary production by increasing nutrient availability and decreasing light availability. These dual effects of DOM generate a unimodal relationship in pelagic primary production and primary producer biomass among lakes over a gradient of DOM concentration. However, the responses of benthic algae to variation in DOM loading are less clear because of their potential to access sediment nutrients. We tested algal production and nutrient limitation along a DOM gradient in northern Sweden. Without added nutrients, benthic algal production showed a unimodal relationship with DOM, similar to reported pelagic responses. Nutrient addition revealed widespread nitrogen limitation, with decreasing severity in lakes with higher DOM. Because the majority of northern Swedish lakes currently fall below the inflection point in this unimodal relationship, moderate increases in DOM have the potential to increase benthic primary production, particularly for epilithic algae.

@article{fanin_relative_2020,
	title = {Relative {Importance} of {Climate}, {Soil} and {Plant} {Functional} {Traits} {During} the {Early} {Decomposition} {Stage} of {Standardized} {Litter}},
	volume = {23},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-019-00452-z},
	doi = {10.1007/s10021-019-00452-z},
	abstract = {Climatic factors have long been considered predominant in controlling decomposition rates at large spatial scales. However, recent research suggests that edaphic factors and plant functional traits may play a more important role than previously expected. In this study, we investigated how biotic and abiotic factors interacted with litter quality by analyzing decomposition rates for two forms of standardized litter substitutes: green tea (high-quality litter) and red tea (low-quality litter). We placed 1188 teabags at two different positions (forest floor and 8 cm deep) across 99 forest sites in France and measured 46 potential drivers at each site. We found that high-quality litter decomposition was strongly related to climatic factors, whereas low-quality litter decomposition was strongly related to edaphic factors and the identity of the dominant tree species in the stand. This indicates that the relative importance of climate, soil and plant functional traits in the litter decomposition process depends on litter quality, which was the predominant factor controlling decomposition rate in this experiment. We also found that burying litter increased decomposition rates, and that this effect was more important for green tea in drier environments. This suggests that changes in position (surface vs. buried) at the plot scale may be as important as the role of macroclimate on decomposition rates because of varying water availability along the soil profile. Acknowledging that the effect of climate on decomposition depends on litter quality and that the macroclimate is not necessarily the predominant factor at large spatial scales is the first step toward identifying the factors regulating decomposition rates from the local scale to the global scale.},
	language = {en},
	number = {5},
	urldate = {2024-03-26},
	journal = {Ecosystems},
	author = {Fanin, Nicolas and Bezaud, Sophie and Sarneel, Judith M. and Cecchini, Sébastien and Nicolas, Manuel and Augusto, Laurent},
	month = aug,
	year = {2020},
	keywords = {\#nosource, Carbon turnover, climate, decomposition, nutrient cycling, plant traits, soil depth, soil parent material, soil properties, tea bag index},
	pages = {1004--1018},
}

Climatic factors have long been considered predominant in controlling decomposition rates at large spatial scales. However, recent research suggests that edaphic factors and plant functional traits may play a more important role than previously expected. In this study, we investigated how biotic and abiotic factors interacted with litter quality by analyzing decomposition rates for two forms of standardized litter substitutes: green tea (high-quality litter) and red tea (low-quality litter). We placed 1188 teabags at two different positions (forest floor and 8 cm deep) across 99 forest sites in France and measured 46 potential drivers at each site. We found that high-quality litter decomposition was strongly related to climatic factors, whereas low-quality litter decomposition was strongly related to edaphic factors and the identity of the dominant tree species in the stand. This indicates that the relative importance of climate, soil and plant functional traits in the litter decomposition process depends on litter quality, which was the predominant factor controlling decomposition rate in this experiment. We also found that burying litter increased decomposition rates, and that this effect was more important for green tea in drier environments. This suggests that changes in position (surface vs. buried) at the plot scale may be as important as the role of macroclimate on decomposition rates because of varying water availability along the soil profile. Acknowledging that the effect of climate on decomposition depends on litter quality and that the macroclimate is not necessarily the predominant factor at large spatial scales is the first step toward identifying the factors regulating decomposition rates from the local scale to the global scale.

@article{ehrich_documenting_2020,
	title = {Documenting lemming population change in the {Arctic}: {Can} we detect trends?},
	volume = {49},
	issn = {1654-7209},
	shorttitle = {Documenting lemming population change in the {Arctic}},
	url = {https://doi.org/10.1007/s13280-019-01198-7},
	doi = {10.1007/s13280-019-01198-7},
	abstract = {Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Ambio},
	author = {Ehrich, Dorothée and Schmidt, Niels M. and Gauthier, Gilles and Alisauskas, Ray and Angerbjörn, Anders and Clark, Karin and Ecke, Frauke and Eide, Nina E. and Framstad, Erik and Frandsen, Jay and Franke, Alastair and Gilg, Olivier and Giroux, Marie-Andrée and Henttonen, Heikki and Hörnfeldt, Birger and Ims, Rolf A. and Kataev, Gennadiy D. and Kharitonov, Sergey P. and Killengreen, Siw T. and Krebs, Charles J. and Lanctot, Richard B. and Lecomte, Nicolas and Menyushina, Irina E. and Morris, Douglas W. and Morrisson, Guy and Oksanen, Lauri and Oksanen, Tarja and Olofsson, Johan and Pokrovsky, Ivan G. and Popov, Igor Yu. and Reid, Donald and Roth, James D. and Saalfeld, Sarah T. and Samelius, Gustaf and Sittler, Benoit and Sleptsov, Sergey M. and Smith, Paul A. and Sokolov, Aleksandr A. and Sokolova, Natalya A. and Soloviev, Mikhail Y. and Solovyeva, Diana V.},
	month = mar,
	year = {2020},
	keywords = {\#nosource, Arctic, Dicrostonyx, Lemmus, Population monitoring, Small rodent, Temporal trends},
	pages = {786--800},
}

Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.

@article{bogard_patterns_2020,
	title = {Patterns of {Spring}/{Summer} {Open}-{Water} {Metabolism} {Across} {Boreal} {Lakes}},
	volume = {23},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-020-00487-7},
	doi = {10.1007/s10021-020-00487-7},
	abstract = {Northern regions host the greatest density of surface water globally, but knowledge of lake metabolism in this vast yet remote landscape is limited. Here, we used an oxygen stable isotope approach to quantify patterns and drivers of surface layer metabolism in lakes throughout an approximately 106 km2 tract of boreal Canada. Ecosystem gross primary production (GPP) and respiration rates (R) were much higher than previously assumed for spring and summer months. Both rates were strongly linked to nitrogen (N) concentrations, not light availability, despite earlier work showing community-level light effects. Net ecosystem production (NEP = GPP − R) was negative for most lakes. Hierarchical modeling revealed that although NEP is strongly stabilized via similar effects of N on both GPP and R, NEP decreases with increasing dissolved organic carbon (DOC). These interactive controls on NEP were not predictable from bivariate regressions linking NEP to physical, chemical or habitat-specific drivers. In contrast to expectations, NEP was higher in warmer waters due to increased temperature dependency of GPP, not R. Temperature and DOC content had opposing effects on NEP in all but the most dystrophic lakes, possibly implying a muted response of metabolic balances to future shifts in both regional climate and OC delivery.},
	language = {en},
	number = {8},
	urldate = {2024-03-26},
	journal = {Ecosystems},
	author = {Bogard, Matthew J. and St-Gelais, Nicolas F. and Vachon, Dominic and del Giorgio, Paul A.},
	month = dec,
	year = {2020},
	keywords = {\#nosource, Boreal lake, Catchment, Climate, Food web, Landscape, Metabolism, Net ecosystem production, Primary production, Respiration},
	pages = {1581--1597},
}

Northern regions host the greatest density of surface water globally, but knowledge of lake metabolism in this vast yet remote landscape is limited. Here, we used an oxygen stable isotope approach to quantify patterns and drivers of surface layer metabolism in lakes throughout an approximately 106 km2 tract of boreal Canada. Ecosystem gross primary production (GPP) and respiration rates (R) were much higher than previously assumed for spring and summer months. Both rates were strongly linked to nitrogen (N) concentrations, not light availability, despite earlier work showing community-level light effects. Net ecosystem production (NEP = GPP − R) was negative for most lakes. Hierarchical modeling revealed that although NEP is strongly stabilized via similar effects of N on both GPP and R, NEP decreases with increasing dissolved organic carbon (DOC). These interactive controls on NEP were not predictable from bivariate regressions linking NEP to physical, chemical or habitat-specific drivers. In contrast to expectations, NEP was higher in warmer waters due to increased temperature dependency of GPP, not R. Temperature and DOC content had opposing effects on NEP in all but the most dystrophic lakes, possibly implying a muted response of metabolic balances to future shifts in both regional climate and OC delivery.

@article{blume-werry_invasive_2020,
	title = {Invasive earthworms unlock arctic plant nitrogen limitation},
	volume = {11},
	copyright = {2020 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-020-15568-3},
	doi = {10.1038/s41467-020-15568-3},
	abstract = {Arctic plant growth is predominantly nitrogen limited, where the slow nitrogen turnover in the soil is commonly attributed to the cold arctic climate. Here the authors show that the arctic plant-soil nitrogen cycling is also constrained by the lack of larger detritivores like earthworms.},
	language = {en},
	number = {1},
	urldate = {2020-04-23},
	journal = {Nature Communications},
	author = {Blume-Werry, Gesche and Krab, Eveline J. and Olofsson, Johan and Sundqvist, Maja K. and Väisänen, Maria and Klaminder, Jonatan},
	month = apr,
	year = {2020},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {1--10},
}

Arctic plant growth is predominantly nitrogen limited, where the slow nitrogen turnover in the soil is commonly attributed to the cold arctic climate. Here the authors show that the arctic plant-soil nitrogen cycling is also constrained by the lack of larger detritivores like earthworms.

@article{payandi-rolland_dissolved_2020,
	title = {Dissolved organic matter biodegradation along a hydrological continuum in permafrost peatlands},
	volume = {749},
	issn = {0048-9697},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969720349925},
	doi = {10.1016/j.scitotenv.2020.141463},
	abstract = {Arctic regions contain large amounts of organic carbon (OC) trapped in soil and wetland permafrost. With climate warming, part of this OC is released to aquatic systems and degraded by microorganisms, thus resulting in positive feedback due to carbon (C) emission. In wetland areas, water bodies are spatially heterogenic and separated by landscape position and water residence time. This represents a hydrological continuum, from depressions, smaller water bodies and lakes to the receiving streams and rivers. Yet, the effect of this heterogeneity on the OC release from the soil and its processing in waters is largely unknown and not accounted for in C cycle models of Arctic regions. Here we investigated the dissolved OC (DOC) biodegradation of aquatic systems along a hydrological continuum located in two discontinuous permafrost sites: in western Siberia and northern Sweden. The biodegradable dissolved OC (BDOC15; \% DOC lost relative to the initial DOC concentration after 15 days incubation at 20 °C) ranged from 0 to 20\% for small water bodies located at the beginning of the continuum (soil solutions, small ponds, fen and lakes) and from 10 to 20\% for streams and rivers. While the BDOC15 increased, the removal rate of DOC decreased along the hydrological continuum. The potential maximum CO2 production from DOC biodegradation was estimated to account for only a small part of in-situ CO2 emissions measured in peatland aquatic systems of northern Sweden and western Siberia. This suggests that other sources, such as sediment respiration and soil input, largely contribute to CO2 emissions from small surface waters of permafrost peatlands. Our results highlight the need to account for large heterogeneity of dissolved OC concentration and biodegradability in order to quantify C cycling in arctic water bodies susceptible to permafrost thaw.},
	journal = {Science of The Total Environment},
	author = {Payandi-Rolland, D. and Shirokova, L.S. and Tesfa, M. and Bénézeth, P. and Lim, A.G. and Kuzmina, D. and Karlsson, J. and Giesler, R. and Pokrovsky, O.S.},
	month = dec,
	year = {2020},
	keywords = {Carbon dioxide emission, Low molecular weight organic acids, River, Stream, Supra-permafrost water, Thermokarst lake},
	pages = {141463},
}

Arctic regions contain large amounts of organic carbon (OC) trapped in soil and wetland permafrost. With climate warming, part of this OC is released to aquatic systems and degraded by microorganisms, thus resulting in positive feedback due to carbon (C) emission. In wetland areas, water bodies are spatially heterogenic and separated by landscape position and water residence time. This represents a hydrological continuum, from depressions, smaller water bodies and lakes to the receiving streams and rivers. Yet, the effect of this heterogeneity on the OC release from the soil and its processing in waters is largely unknown and not accounted for in C cycle models of Arctic regions. Here we investigated the dissolved OC (DOC) biodegradation of aquatic systems along a hydrological continuum located in two discontinuous permafrost sites: in western Siberia and northern Sweden. The biodegradable dissolved OC (BDOC15; % DOC lost relative to the initial DOC concentration after 15 days incubation at 20 °C) ranged from 0 to 20% for small water bodies located at the beginning of the continuum (soil solutions, small ponds, fen and lakes) and from 10 to 20% for streams and rivers. While the BDOC15 increased, the removal rate of DOC decreased along the hydrological continuum. The potential maximum CO2 production from DOC biodegradation was estimated to account for only a small part of in-situ CO2 emissions measured in peatland aquatic systems of northern Sweden and western Siberia. This suggests that other sources, such as sediment respiration and soil input, largely contribute to CO2 emissions from small surface waters of permafrost peatlands. Our results highlight the need to account for large heterogeneity of dissolved OC concentration and biodegradability in order to quantify C cycling in arctic water bodies susceptible to permafrost thaw.

@article{vaisanen_meshes_2020,
	title = {Meshes in mesocosms control solute and biota exchange in soils: {A} step towards disentangling (a)biotic impacts on the fate of thawing permafrost},
	volume = {151},
	issn = {0929-1393},
	shorttitle = {Meshes in mesocosms control solute and biota exchange in soils},
	url = {http://www.sciencedirect.com/science/article/pii/S0929139319307206},
	doi = {10.1016/j.apsoil.2020.103537},
	abstract = {Environmental changes feedback to climate through their impact on soil functions such as carbon (C) and nutrient sequestration. Abiotic conditions and the interactions between above- and belowground biota drive soil responses to environmental change but these (a)biotic interactions are challenging to study. Nonetheless, better understanding of these interactions would improve predictions of future soil functioning and the soil-climate feedback and, in this context, permafrost soils are of particular interest due to their vast soil C-stores. We need new tools to isolate abiotic (microclimate, chemistry) and biotic (roots, fauna, microorganisms) components and to identify their respective roles in soil processes. We developed a new experimental setup, in which we mimic thermokarst (permafrost thaw-induced soil subsidence) by fitting thawed permafrost and vegetated active layer sods side by side into mesocosms deployed in a subarctic tundra over two growing seasons. In each mesocosm, the two sods were separated from each other by barriers with different mesh sizes to allow varying degrees of physical connection and, consequently, (a)biotic exchange between active layer and permafrost. We demonstrate that our mesh-approach succeeded in controlling 1) lateral exchange of solutes between the two soil types, 2) colonization of permafrost by microbes but not by soil fauna, and 3) ingrowth of roots into permafrost. In particular, experimental thermokarst induced a {\textasciitilde}60\% decline in permafrost nitrogen (N) content, a shift in soil bacteria and a rapid buildup of root biomass (+33.2 g roots m−2 soil). This indicates that cascading plant-soil-microbe linkages are at the heart of biogeochemical cycling in thermokarst events. We propose that this novel setup can be used to explore the effects of (a)biotic ecosystem components on focal biogeochemical processes in permafrost soils and beyond.},
	language = {en},
	urldate = {2020-04-23},
	journal = {Applied Soil Ecology},
	author = {Väisänen, Maria and Krab, Eveline J. and Monteux, Sylvain and Teuber, Laurenz M. and Gavazov, Konstantin and Weedon, James T. and Keuper, Frida and Dorrepaal, Ellen},
	month = jul,
	year = {2020},
	keywords = {\#nosource, Bacterial community, Faunal inoculation, Field incubation, Lateral soil connection, Nitrogen, Root},
	pages = {103537},
}

Environmental changes feedback to climate through their impact on soil functions such as carbon (C) and nutrient sequestration. Abiotic conditions and the interactions between above- and belowground biota drive soil responses to environmental change but these (a)biotic interactions are challenging to study. Nonetheless, better understanding of these interactions would improve predictions of future soil functioning and the soil-climate feedback and, in this context, permafrost soils are of particular interest due to their vast soil C-stores. We need new tools to isolate abiotic (microclimate, chemistry) and biotic (roots, fauna, microorganisms) components and to identify their respective roles in soil processes. We developed a new experimental setup, in which we mimic thermokarst (permafrost thaw-induced soil subsidence) by fitting thawed permafrost and vegetated active layer sods side by side into mesocosms deployed in a subarctic tundra over two growing seasons. In each mesocosm, the two sods were separated from each other by barriers with different mesh sizes to allow varying degrees of physical connection and, consequently, (a)biotic exchange between active layer and permafrost. We demonstrate that our mesh-approach succeeded in controlling 1) lateral exchange of solutes between the two soil types, 2) colonization of permafrost by microbes but not by soil fauna, and 3) ingrowth of roots into permafrost. In particular, experimental thermokarst induced a ~60% decline in permafrost nitrogen (N) content, a shift in soil bacteria and a rapid buildup of root biomass (+33.2 g roots m−2 soil). This indicates that cascading plant-soil-microbe linkages are at the heart of biogeochemical cycling in thermokarst events. We propose that this novel setup can be used to explore the effects of (a)biotic ecosystem components on focal biogeochemical processes in permafrost soils and beyond.

@article{doherty_transition_2020,
	title = {The {Transition} {From} {Stochastic} to {Deterministic} {Bacterial} {Community} {Assembly} {During} {Permafrost} {Thaw} {Succession}},
	volume = {11},
	doi = {10.3389/fmicb.2020.596589},
	abstract = {The Northern high latitudes are warming twice as fast as the global average, and permafrost has become vulnerable to thaw. Changes to the environment during thaw leads to shifts in microbial communities and their associated functions, such as greenhouse gas emissions. Understanding the ecological processes that structure the identity and abundance (i.e., assembly) of pre- and post-thaw communities may improve predictions of the functional outcomes of permafrost thaw. We characterized microbial community assembly during permafrost thaw using in situ observations and a laboratory incubation of soils from the Storflaket Mire in Abisko, Sweden, where permafrost thaw has occurred over the past decade. In situ observations indicated that bacterial community assembly was driven by randomness (i.e., stochastic processes) immediately after thaw with drift and dispersal limitation being the dominant processes. As post-thaw succession progressed, environmentally driven (i.e., deterministic) processes became increasingly important in structuring microbial communities where homogenizing selection was the only process structuring upper active layer soils. Furthermore, laboratory-induced thaw reflected assembly dynamics immediately after thaw indicated by an increase in drift, but did not capture the long-term effects of permafrost thaw on microbial community dynamics. Our results did not reflect a link between assembly dynamics and carbon emissions, likely because respiration is the product of many processes in microbial communities. Identification of dominant microbial community assembly processes has the potential to improve our understanding of the ecological impact of permafrost thaw and the permafrost–climate feedback.},
	journal = {Frontiers in Microbiology},
	author = {Doherty, Stacey and Barbato, Robyn and Grandy, A. and Thomas, William and Monteux, Sylvain and Dorrepaal, Ellen and Johansson, Margareta and Ernakovich, Jessica},
	month = nov,
	year = {2020},
	keywords = {\#nosource},
	pages = {596589},
}

The Northern high latitudes are warming twice as fast as the global average, and permafrost has become vulnerable to thaw. Changes to the environment during thaw leads to shifts in microbial communities and their associated functions, such as greenhouse gas emissions. Understanding the ecological processes that structure the identity and abundance (i.e., assembly) of pre- and post-thaw communities may improve predictions of the functional outcomes of permafrost thaw. We characterized microbial community assembly during permafrost thaw using in situ observations and a laboratory incubation of soils from the Storflaket Mire in Abisko, Sweden, where permafrost thaw has occurred over the past decade. In situ observations indicated that bacterial community assembly was driven by randomness (i.e., stochastic processes) immediately after thaw with drift and dispersal limitation being the dominant processes. As post-thaw succession progressed, environmentally driven (i.e., deterministic) processes became increasingly important in structuring microbial communities where homogenizing selection was the only process structuring upper active layer soils. Furthermore, laboratory-induced thaw reflected assembly dynamics immediately after thaw indicated by an increase in drift, but did not capture the long-term effects of permafrost thaw on microbial community dynamics. Our results did not reflect a link between assembly dynamics and carbon emissions, likely because respiration is the product of many processes in microbial communities. Identification of dominant microbial community assembly processes has the potential to improve our understanding of the ecological impact of permafrost thaw and the permafrost–climate feedback.

@article{hough_biotic_2020,
	title = {Biotic and environmental drivers of plant microbiomes across a permafrost thaw gradient},
	volume = {11},
	doi = {10.3389/fmicb.2020.00796},
	journal = {Frontiers in Microbiology},
	author = {Hough, Moira and McClure, Amelia and Bolduc, Benjamin and Dorrepaal, Ellen and Saleska, Scott and Klepac-Ceraj, Vanja and Rich, Virginia},
	year = {2020},
	note = {Publisher: Frontiers Media SA},
	keywords = {\#nosource},
	pages = {796},
}

@article{bolduc_isogenie_2020,
	title = {The {IsoGenie} database: {An} interdisciplinary data management solution for ecosystems biology and environmental research},
	volume = {8},
	doi = {10.7717/peerj.9467},
	abstract = {Modern microbial and ecosystem sciences require diverse interdisciplinary teams that are often challenged in “speaking” to one another due to different languages and data product types. Here we introduce the IsoGenie Database (IsoGenieDB; https://isogenie-db.asc.ohio-state.edu/ ), a de novo developed data management and exploration platform, as a solution to this challenge of accurately representing and integrating heterogenous environmental and microbial data across ecosystem scales. The IsoGenieDB is a public and private data infrastructure designed to store and query data generated by the IsoGenie Project, a {\textasciitilde}10 year DOE-funded project focused on discovering ecosystem climate feedbacks in a thawing permafrost landscape. The IsoGenieDB provides (i) a platform for IsoGenie Project members to explore the project’s interdisciplinary datasets across scales through the inherent relationships among data entities, (ii) a framework to consolidate and harmonize the datasets needed by the team’s modelers, and (iii) a public venue that leverages the same spatially explicit, disciplinarily integrated data structure to share published datasets. The IsoGenieDB is also being expanded to cover the NASA-funded Archaea to Atmosphere (A2A) project, which scales the findings of IsoGenie to a broader suite of Arctic peatlands, via the umbrella A2A Database (A2A-DB). The IsoGenieDB’s expandability and flexible architecture allow it to serve as an example ecosystems database.},
	journal = {PeerJ},
	author = {Bolduc, Benjamin and Hodgkins, Suzanne and Varner, Ruth and Crill, Patrick and Mccalley, Carmody and Chanton, Jeffrey and Tyson, Gene and Riley, William and Palace, Michael and Duhaime, Melissa and Hough, Moira and Saleska, Scott and Sullivan, Matthew and Rich, Virginia and Zayed, Ahmed and Cory, Alex and Mcclure, Amelia and Garnello, Anthony and Perry, Apryl and Cooper, William},
	month = aug,
	year = {2020},
	keywords = {\#nosource},
	pages = {e9467},
}

Modern microbial and ecosystem sciences require diverse interdisciplinary teams that are often challenged in “speaking” to one another due to different languages and data product types. Here we introduce the IsoGenie Database (IsoGenieDB; https://isogenie-db.asc.ohio-state.edu/ ), a de novo developed data management and exploration platform, as a solution to this challenge of accurately representing and integrating heterogenous environmental and microbial data across ecosystem scales. The IsoGenieDB is a public and private data infrastructure designed to store and query data generated by the IsoGenie Project, a ~10 year DOE-funded project focused on discovering ecosystem climate feedbacks in a thawing permafrost landscape. The IsoGenieDB provides (i) a platform for IsoGenie Project members to explore the project’s interdisciplinary datasets across scales through the inherent relationships among data entities, (ii) a framework to consolidate and harmonize the datasets needed by the team’s modelers, and (iii) a public venue that leverages the same spatially explicit, disciplinarily integrated data structure to share published datasets. The IsoGenieDB is also being expanded to cover the NASA-funded Archaea to Atmosphere (A2A) project, which scales the findings of IsoGenie to a broader suite of Arctic peatlands, via the umbrella A2A Database (A2A-DB). The IsoGenieDB’s expandability and flexible architecture allow it to serve as an example ecosystems database.

@article{lett_mosses_2020,
	title = {Mosses modify effects of warmer and wetter conditions on tree seedlings at the alpine treeline},
	volume = {26},
	issn = {1365-2486},
	url = {http://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15256},
	doi = {10.1111/gcb.15256},
	abstract = {Climate warming enables tree seedling establishment beyond the current alpine treeline, but to achieve this, seedlings have to establish within existing tundra vegetation. In tundra, mosses are a prominent feature, known to regulate soil temperature and moisture through their physical structure and associated water retention capacity. Moss presence and species identity might therefore modify the impact of increases in temperature and precipitation on tree seedling establishment at the arctic-alpine treeline. We followed Betula pubescens and Pinus sylvestris seedling survival and growth during three growing seasons in the field. Tree seedlings were transplanted along a natural precipitation gradient at the subarctic-alpine treeline in northern Sweden, into plots dominated by each of three common moss species and exposed to combinations of moss removal and experimental warming by open-top chambers (OTCs). Independent of climate, the presence of feather moss, but not Sphagnum, strongly supressed survival of both tree species. Positive effects of warming and precipitation on survival and growth of B. pubescens seedlings occurred in the absence of mosses and as expected, this was partly dependent on moss species. P. sylvestris survival was greatest at high precipitation, and this effect was more pronounced in Sphagnum than in feather moss plots irrespective of whether the mosses had been removed or not. Moss presence did not reduce the effects of OTCs on soil temperature. Mosses therefore modified seedling response to climate through other mechanisms, such as altered competition or nutrient availability. We conclude that both moss presence and species identity pose a strong control on seedling establishment at the alpine treeline, and that in some cases mosses weaken climate-change effects on seedling establishment. Changes in moss abundance and species composition therefore have the potential to hamper treeline expansion induced by climate warming.},
	language = {en},
	number = {10},
	urldate = {2022-06-28},
	journal = {Global Change Biology},
	author = {Lett, Signe and Teuber, Laurenz M. and Krab, Eveline J. and Michelsen, Anders and Olofsson, Johan and Nilsson, Marie-Charlotte and Wardle, David A. and Dorrepaal, Ellen},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15256},
	keywords = {\#nosource, Arctic, Betula pubescens, Pinus sylvestris, bryophytes, climate change, plant interactions, precipitation, treeline expansion},
	pages = {5754--5766},
}

Climate warming enables tree seedling establishment beyond the current alpine treeline, but to achieve this, seedlings have to establish within existing tundra vegetation. In tundra, mosses are a prominent feature, known to regulate soil temperature and moisture through their physical structure and associated water retention capacity. Moss presence and species identity might therefore modify the impact of increases in temperature and precipitation on tree seedling establishment at the arctic-alpine treeline. We followed Betula pubescens and Pinus sylvestris seedling survival and growth during three growing seasons in the field. Tree seedlings were transplanted along a natural precipitation gradient at the subarctic-alpine treeline in northern Sweden, into plots dominated by each of three common moss species and exposed to combinations of moss removal and experimental warming by open-top chambers (OTCs). Independent of climate, the presence of feather moss, but not Sphagnum, strongly supressed survival of both tree species. Positive effects of warming and precipitation on survival and growth of B. pubescens seedlings occurred in the absence of mosses and as expected, this was partly dependent on moss species. P. sylvestris survival was greatest at high precipitation, and this effect was more pronounced in Sphagnum than in feather moss plots irrespective of whether the mosses had been removed or not. Moss presence did not reduce the effects of OTCs on soil temperature. Mosses therefore modified seedling response to climate through other mechanisms, such as altered competition or nutrient availability. We conclude that both moss presence and species identity pose a strong control on seedling establishment at the alpine treeline, and that in some cases mosses weaken climate-change effects on seedling establishment. Changes in moss abundance and species composition therefore have the potential to hamper treeline expansion induced by climate warming.

@article{myers-smith_complexity_2020,
	title = {Complexity revealed in the greening of the {Arctic}},
	volume = {10},
	copyright = {2020 Springer Nature Limited},
	issn = {1758-6798},
	url = {http://www.nature.com/articles/s41558-019-0688-1},
	doi = {10.1038/s41558-019-0688-1},
	abstract = {As the Arctic warms, vegetation is responding, and satellite measures indicate widespread greening at high latitudes. This ‘greening of the Arctic’ is among the world’s most important large-scale ecological responses to global climate change. However, a consensus is emerging that the underlying causes and future dynamics of so-called Arctic greening and browning trends are more complex, variable and inherently scale-dependent than previously thought. Here we summarize the complexities of observing and interpreting high-latitude greening to identify priorities for future research. Incorporating satellite and proximal remote sensing with in-situ data, while accounting for uncertainties and scale issues, will advance the study of past, present and future Arctic vegetation change.},
	language = {en},
	number = {2},
	urldate = {2021-11-09},
	journal = {Nature Climate Change},
	author = {Myers-Smith, Isla H. and Kerby, Jeffrey T. and Phoenix, Gareth K. and Bjerke, Jarle W. and Epstein, Howard E. and Assmann, Jakob J. and John, Christian and Andreu-Hayles, Laia and Angers-Blondin, Sandra and Beck, Pieter S. A. and Berner, Logan T. and Bhatt, Uma S. and Bjorkman, Anne D. and Blok, Daan and Bryn, Anders and Christiansen, Casper T. and Cornelissen, J. Hans C. and Cunliffe, Andrew M. and Elmendorf, Sarah C. and Forbes, Bruce C. and Goetz, Scott J. and Hollister, Robert D. and de Jong, Rogier and Loranty, Michael M. and Macias-Fauria, Marc and Maseyk, Kadmiel and Normand, Signe and Olofsson, Johan and Parker, Thomas C. and Parmentier, Frans-Jan W. and Post, Eric and Schaepman-Strub, Gabriela and Stordal, Frode and Sullivan, Patrick F. and Thomas, Haydn J. D. and Tømmervik, Hans and Treharne, Rachael and Tweedie, Craig E. and Walker, Donald A. and Wilmking, Martin and Wipf, Sonja},
	month = feb,
	year = {2020},
	note = {Bandiera\_abtest: a
Cg\_type: Nature Research Journals
Number: 2
Primary\_atype: Reviews
Publisher: Nature Publishing Group
Subject\_term: Climate change;Climate-change ecology
Subject\_term\_id: climate-change;climate-change-ecology},
	keywords = {\#nosource, Climate change, Climate-change ecology},
	pages = {106--117},
}

As the Arctic warms, vegetation is responding, and satellite measures indicate widespread greening at high latitudes. This ‘greening of the Arctic’ is among the world’s most important large-scale ecological responses to global climate change. However, a consensus is emerging that the underlying causes and future dynamics of so-called Arctic greening and browning trends are more complex, variable and inherently scale-dependent than previously thought. Here we summarize the complexities of observing and interpreting high-latitude greening to identify priorities for future research. Incorporating satellite and proximal remote sensing with in-situ data, while accounting for uncertainties and scale issues, will advance the study of past, present and future Arctic vegetation change.

@article{vachon_paired_2020,
	title = {Paired {O}$_{\textrm{2}}$–{CO}$_{\textrm{2}}$ measurements provide emergent insights into aquatic ecosystem function},
	volume = {5},
	copyright = {© 2019 The Authors. Limnology and Oceanography Letters published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {http://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10135},
	doi = {10.1002/lol2.10135},
	abstract = {Scientific Significance Statement Metabolic stoichiometry predicts that dissolved oxygen (O2) and carbon dioxide (CO2) in aquatic ecosystems should covary inversely; however, field observations often diverge from theoretical expectations. Here, we propose a suite of metrics describing this O2 and CO2 decoupling and introduce a conceptual framework for interpreting these metrics within aquatic ecosystems. Within this framework, we interpret cross-system patterns of high-frequency O2 and CO2 measurements in 11 northern lakes and extract emergent insights into the metabolic behavior and the simultaneous roles of chemical and physical forcing in shaping ecosystem processes. This approach leverages the power of high-frequency paired O2–CO2 measurements, and yields a novel, integrative aquatic system typology which can also be applicable more broadly to streams and rivers, wetlands and marine systems.},
	language = {en},
	number = {4},
	urldate = {2021-01-19},
	journal = {Limnology and Oceanography Letters},
	author = {Vachon, Dominic and Sadro, Steven and Bogard, Matthew J. and Lapierre, Jean-François and Baulch, Helen M. and Rusak, James A. and Denfeld, Blaize A. and Laas, Alo and Klaus, Marcus and Karlsson, Jan and Weyhenmeyer, Gesa A. and Giorgio, Paul A. del},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10135},
	keywords = {\#nosource},
	pages = {287--294},
}

Scientific Significance Statement Metabolic stoichiometry predicts that dissolved oxygen (O2) and carbon dioxide (CO2) in aquatic ecosystems should covary inversely; however, field observations often diverge from theoretical expectations. Here, we propose a suite of metrics describing this O2 and CO2 decoupling and introduce a conceptual framework for interpreting these metrics within aquatic ecosystems. Within this framework, we interpret cross-system patterns of high-frequency O2 and CO2 measurements in 11 northern lakes and extract emergent insights into the metabolic behavior and the simultaneous roles of chemical and physical forcing in shaping ecosystem processes. This approach leverages the power of high-frequency paired O2–CO2 measurements, and yields a novel, integrative aquatic system typology which can also be applicable more broadly to streams and rivers, wetlands and marine systems.

@article{perryman_thaw_2020,
	title = {Thaw {Transitions} and {Redox} {Conditions} {Drive} {Methane} {Oxidation} in a {Permafrost} {Peatland}},
	volume = {125},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {2169-8961},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005526},
	doi = {10.1029/2019JG005526},
	abstract = {Permafrost peatlands are a significant source of methane (CH4) emissions to the atmosphere and could emit more CH4 with continued permafrost thaw. Aerobic methane-oxidizing bacteria may attenuate a substantial fraction of CH4 emissions in thawing permafrost peatlands; however, the impact of permafrost thaw on CH4 oxidation is uncertain. We measured potential CH4 oxidation rates (hereafter, CH4 oxidation) and their predictors using laboratory incubations and in situ porewater redox chemistry across a permafrost thaw gradient of eight thaw stages at Stordalen Mire, a permafrost peatland complex in northernmost Sweden. Methane oxidation rates increased across a gradient of permafrost thaw and differed in transitional thaw stages relative to end-member stages. Oxidation was consistently higher in submerged fens than in bogs or palsas across a range of CH4 concentrations. We also observed that CH4 oxidation increased with decreasing in situ redox potential and was highest in sites with lower redox potential (Eh {\textless} 10 mV) and high water table. Our results suggest that redox potential can be used as an important predictor of CH4 oxidation, especially in thawed permafrost peatlands. Our results also highlight the importance of considering transitional thaw stages when characterizing landscape-scale CH4 dynamics, because these transitional areas have different rates and controls of CH4 oxidation relative to intact or completely thawed permafrost areas. As permafrost thaw increases the total area of semiwet and wet thaw stages in permafrost peatlands, CH4 oxidation represents an important control on CH4 emissions to the atmosphere.},
	language = {en},
	number = {3},
	urldate = {2020-03-19},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Perryman, Clarice R. and McCalley, Carmody K. and Malhotra, Avni and Fahnestock, M. Florencia and Kashi, Natalie N. and Bryce, Julia G. and Giesler, Reiner and Varner, Ruth K.},
	year = {2020},
	note = {\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JG005526},
	keywords = {\#nosource, methane, methanotrophs, peatland, permafrost, redox},
	pages = {e2019JG005526},
}

Permafrost peatlands are a significant source of methane (CH4) emissions to the atmosphere and could emit more CH4 with continued permafrost thaw. Aerobic methane-oxidizing bacteria may attenuate a substantial fraction of CH4 emissions in thawing permafrost peatlands; however, the impact of permafrost thaw on CH4 oxidation is uncertain. We measured potential CH4 oxidation rates (hereafter, CH4 oxidation) and their predictors using laboratory incubations and in situ porewater redox chemistry across a permafrost thaw gradient of eight thaw stages at Stordalen Mire, a permafrost peatland complex in northernmost Sweden. Methane oxidation rates increased across a gradient of permafrost thaw and differed in transitional thaw stages relative to end-member stages. Oxidation was consistently higher in submerged fens than in bogs or palsas across a range of CH4 concentrations. We also observed that CH4 oxidation increased with decreasing in situ redox potential and was highest in sites with lower redox potential (Eh \textless 10 mV) and high water table. Our results suggest that redox potential can be used as an important predictor of CH4 oxidation, especially in thawed permafrost peatlands. Our results also highlight the importance of considering transitional thaw stages when characterizing landscape-scale CH4 dynamics, because these transitional areas have different rates and controls of CH4 oxidation relative to intact or completely thawed permafrost areas. As permafrost thaw increases the total area of semiwet and wet thaw stages in permafrost peatlands, CH4 oxidation represents an important control on CH4 emissions to the atmosphere.

@article{pioli_linking_2020,
	title = {Linking plant litter microbial diversity to microhabitat conditions, environmental gradients and litter mass loss: {Insights} from a {European} study using standard litter bags},
	volume = {144},
	issn = {0038-0717},
	shorttitle = {Linking plant litter microbial diversity to microhabitat conditions, environmental gradients and litter mass loss},
	url = {http://www.sciencedirect.com/science/article/pii/S0038071720300754},
	doi = {10.1016/j.soilbio.2020.107778},
	abstract = {Plant litter decomposition is a key process for carbon dynamics and nutrient cycling in terrestrial ecosystems. The interaction between litter properties, climatic conditions and soil attributes, influences the activity of microorganisms responsible for litter mineralization. So far, studies using standardized litters to investigate the response of bacterial and fungal communities under different environmental conditions are scarce, especially along wide geographic ranges. We used a standardized protocol to investigate the diversity of bacteria and fungi in plant litter with the aim of: (i) comparing the microbial communities of native and exotic litters with the community of local soil along a European transect from northern Finland to southern Italy, (ii) defining whether and to what extent, litter types with different traits represent selective substrates for microbial communities, (iii) disentangling the abiotic drivers of microbial diversity, and (iv) correlating the microbial diversity and species co-occurrences patterns with litter mass loss. We buried native litter and three exotic standardized litters (Deschampsia cespitosa, rooibos tea and green tea) at 12 European study sites. We determined litter mass loss after 94 days. We used an automated molecular DNA-based fingerprinting (ARISA) to profile the bacterial and fungal communities of each litter type and soil (180 samples in total). Microbial communities in native and exotic litters differed from local soil assemblages. Green tea and D. cespitosa litter represented more selective substrates compared to native litter and rooibos. Soil moisture and soil temperature were the major drivers of microbial community structure at larger scales, though with varying patterns according to litter type. Soil attributes (i.e. moisture and C/N ratios) better explained the differences in microbial abundances than litter type. Green tea degraded faster than all other litter types and accounted for the largest number of positive co-occurrences among microbial taxa. Litter mass loss was positively correlated with fungal evenness and with the percentage of positive co-occurrences between fungi. Our findings suggest that the microbial community at larger scales reflects the complex interplay between litter type and soil attributes, with the latter exerting a major influence. Mass loss patterns are in part determined by inter- and intra-kingdom interactions and fungal diversity.},
	language = {en},
	urldate = {2020-03-18},
	journal = {Soil Biology and Biochemistry},
	author = {Pioli, Silvia and Sarneel, Judith and Thomas, Haydn J. D. and Domene, Xavier and Andrés, Pilar and Hefting, Mariet and Reitz, Thomas and Laudon, Hjalmar and Sandén, Taru and Piscová, Veronika and Aurela, Mika and Brusetti, Lorenzo},
	month = may,
	year = {2020},
	keywords = {\#nosource, Abiotic drivers, Litter decomposition, Microbial co-occurrences, Microbial communities' diversity, Molecular fingerprinting, Pan-European study},
	pages = {107778},
}

Plant litter decomposition is a key process for carbon dynamics and nutrient cycling in terrestrial ecosystems. The interaction between litter properties, climatic conditions and soil attributes, influences the activity of microorganisms responsible for litter mineralization. So far, studies using standardized litters to investigate the response of bacterial and fungal communities under different environmental conditions are scarce, especially along wide geographic ranges. We used a standardized protocol to investigate the diversity of bacteria and fungi in plant litter with the aim of: (i) comparing the microbial communities of native and exotic litters with the community of local soil along a European transect from northern Finland to southern Italy, (ii) defining whether and to what extent, litter types with different traits represent selective substrates for microbial communities, (iii) disentangling the abiotic drivers of microbial diversity, and (iv) correlating the microbial diversity and species co-occurrences patterns with litter mass loss. We buried native litter and three exotic standardized litters (Deschampsia cespitosa, rooibos tea and green tea) at 12 European study sites. We determined litter mass loss after 94 days. We used an automated molecular DNA-based fingerprinting (ARISA) to profile the bacterial and fungal communities of each litter type and soil (180 samples in total). Microbial communities in native and exotic litters differed from local soil assemblages. Green tea and D. cespitosa litter represented more selective substrates compared to native litter and rooibos. Soil moisture and soil temperature were the major drivers of microbial community structure at larger scales, though with varying patterns according to litter type. Soil attributes (i.e. moisture and C/N ratios) better explained the differences in microbial abundances than litter type. Green tea degraded faster than all other litter types and accounted for the largest number of positive co-occurrences among microbial taxa. Litter mass loss was positively correlated with fungal evenness and with the percentage of positive co-occurrences between fungi. Our findings suggest that the microbial community at larger scales reflects the complex interplay between litter type and soil attributes, with the latter exerting a major influence. Mass loss patterns are in part determined by inter- and intra-kingdom interactions and fungal diversity.

@article{fork_changing_2020,
	title = {Changing {Source}-{Transport} {Dynamics} {Drive} {Differential} {Browning} {Trends} in a {Boreal} {Stream} {Network}},
	volume = {56},
	copyright = {© 2020 The Authors.},
	issn = {1944-7973},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019WR026336},
	doi = {10.1029/2019WR026336},
	abstract = {Dissolved organic carbon (DOC) concentrations are increasing in freshwaters worldwide, with important implications for aquatic ecology, biogeochemistry, and ecosystem services. While multiple environmental changes may be responsible for these trends, predicting the occurrence and magnitude of “browning” and relating such trends to changes in DOC sources versus hydrologic transport remain key challenges. We analyzed long-term trends in DOC concentration from the two dominant landscape sources (riparian soils and mire peats) and receiving streams in a boreal catchment to evaluate how browning patterns relate to land cover and hydrology. Increases in stream DOC were widespread but not universal. Browning was most pronounced in small, forested streams, where trends corresponded to twofold to threefold increases in DOC production in riparian soils and increases in annual DOC export from a forested headwater. By contrast, DOC did not change in mire peats or streams draining catchments with high lake or mire cover, nor did we observe trends in DOC export from a mire-dominated headwater. The distinct long-term trends in DOC sources also altered concentration-discharge relationships, with a forested headwater shifting from transport-limited toward chemostasis, and a mire outlet stream shifting from chemostasis to source-limitated. Modified DOC supply to headwaters, together with altered seasonal hydrology and differences in the dominant water source along the stream network gave rise to predictable browning trends and consistent concentration-discharge relationships. Overall, our results show that the sources of DOC to boreal aquatic ecosystems are responding to environmental change in fundamentally different ways, with important consequences for browning along boreal stream networks.},
	language = {en},
	number = {2},
	urldate = {2020-03-19},
	journal = {Water Resources Research},
	author = {Fork, Megan L. and Sponseller, Ryan A. and Laudon, Hjalmar},
	year = {2020},
	note = {\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019WR026336},
	keywords = {\#nosource, DOC, brownification, concentration-discharge, flux, riparian, wetland},
	pages = {e2019WR026336},
}

Dissolved organic carbon (DOC) concentrations are increasing in freshwaters worldwide, with important implications for aquatic ecology, biogeochemistry, and ecosystem services. While multiple environmental changes may be responsible for these trends, predicting the occurrence and magnitude of “browning” and relating such trends to changes in DOC sources versus hydrologic transport remain key challenges. We analyzed long-term trends in DOC concentration from the two dominant landscape sources (riparian soils and mire peats) and receiving streams in a boreal catchment to evaluate how browning patterns relate to land cover and hydrology. Increases in stream DOC were widespread but not universal. Browning was most pronounced in small, forested streams, where trends corresponded to twofold to threefold increases in DOC production in riparian soils and increases in annual DOC export from a forested headwater. By contrast, DOC did not change in mire peats or streams draining catchments with high lake or mire cover, nor did we observe trends in DOC export from a mire-dominated headwater. The distinct long-term trends in DOC sources also altered concentration-discharge relationships, with a forested headwater shifting from transport-limited toward chemostasis, and a mire outlet stream shifting from chemostasis to source-limitated. Modified DOC supply to headwaters, together with altered seasonal hydrology and differences in the dominant water source along the stream network gave rise to predictable browning trends and consistent concentration-discharge relationships. Overall, our results show that the sources of DOC to boreal aquatic ecosystems are responding to environmental change in fundamentally different ways, with important consequences for browning along boreal stream networks.

@article{ylanne_removal_2020,
	title = {Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability},
	volume = {90},
	copyright = {© 2019 by the Ecological Society of America},
	issn = {1557-7015},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1396},
	doi = {10.1002/ecm.1396},
	abstract = {The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long-term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long-term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long-term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic.},
	language = {en},
	number = {1},
	urldate = {2020-03-19},
	journal = {Ecological Monographs},
	author = {Ylänne, Henni and Kaarlejärvi, Elina and Väisänen, Maria and Männistö, Minna K. and Ahonen, Saija H. K. and Olofsson, Johan and Stark, Sari},
	year = {2020},
	note = {\_eprint: https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecm.1396},
	keywords = {\#nosource, Rangifer tarandus, SEM, fertilization, herbivory, land use, open-top chamber, reindeer, soil carbon storage},
	pages = {e01396},
}

The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long-term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long-term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long-term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic.

@article{bergstrom_changes_2020,
	title = {Changes in nutritional quality and nutrient limitation regimes of phytoplankton in response to declining {N} deposition in mountain lakes},
	volume = {82},
	issn = {1420-9055},
	url = {https://doi.org/10.1007/s00027-020-0697-1},
	doi = {10.1007/s00027-020-0697-1},
	abstract = {Phytoplankton play a key role in supporting aquatic food webs. However, the effects of ongoing large-scale changes in the concentrations and stoichiometry of important biological compounds [dissolved inorganic N (DIN), total phosphorus (TP), dissolved organic carbon (DOC) and DIN:TP] on the development and nutritional quality of phytoplankton for higher trophic levels are unclear. We conducted lake studies and in situ bioassay experiments in two Swedish mountain regions [Abisko (north) and Jämtland (south)] with different N deposition and where lakes in each region were distributed along a similar gradient in lake DOC (2–7 mg L−1) to assess whether differences in nutrients, DOC and DIN:TP induced differences in phytoplankton quantity [chlorophyll a (Chl-a) and seston carbon (C)] and quality [seston C:N:P stoichiometry and fatty acid (FA) composition]. Using long-term monitoring data from lakes in these two mountain regions, we found declining long-term trends in N deposition and lake DIN and total TP concentrations, but not in lake DIN:TP. Lakes in Abisko received lower N deposition and had lower DIN:TP than those in Jämtland. Phytoplankton was N- to NP-limited in Abisko lakes but NP dual-limited in Jämtland lakes. The N fertilization effects induced by higher DIN:TP were weak on phytoplankton quantity but strong on phytoplankton quality. The phytoplankton had lower eicosapentaenoic acid (EPA) content and higher P content (lower seston C:P) in Abisko compared to in Jämtland. In addition, the quality of the DOC (as indicated by its aromaticity and SUVA) influenced not only the light conditions and the seston C:P ratios, but also the FA composition. We found higher bacteria FA concentrations in seston in Abisko than in Jämtland, despite lower amounts of FA of terrestrial origin in Abisko. Our findings suggest that declining N deposition and enhanced colored terrestrial C loadings leads to lower nutritional quality of basal resources for higher consumers in mountain lakes.},
	language = {en},
	number = {2},
	urldate = {2020-03-19},
	journal = {Aquatic Sciences},
	author = {Bergström, Ann-Kristin and Jonsson, Anders and Isles, Peter D. F. and Creed, Irena F. and Lau, Danny C. P.},
	month = feb,
	year = {2020},
	keywords = {\#nosource},
	pages = {31},
}

Phytoplankton play a key role in supporting aquatic food webs. However, the effects of ongoing large-scale changes in the concentrations and stoichiometry of important biological compounds [dissolved inorganic N (DIN), total phosphorus (TP), dissolved organic carbon (DOC) and DIN:TP] on the development and nutritional quality of phytoplankton for higher trophic levels are unclear. We conducted lake studies and in situ bioassay experiments in two Swedish mountain regions [Abisko (north) and Jämtland (south)] with different N deposition and where lakes in each region were distributed along a similar gradient in lake DOC (2–7 mg L−1) to assess whether differences in nutrients, DOC and DIN:TP induced differences in phytoplankton quantity [chlorophyll a (Chl-a) and seston carbon (C)] and quality [seston C:N:P stoichiometry and fatty acid (FA) composition]. Using long-term monitoring data from lakes in these two mountain regions, we found declining long-term trends in N deposition and lake DIN and total TP concentrations, but not in lake DIN:TP. Lakes in Abisko received lower N deposition and had lower DIN:TP than those in Jämtland. Phytoplankton was N- to NP-limited in Abisko lakes but NP dual-limited in Jämtland lakes. The N fertilization effects induced by higher DIN:TP were weak on phytoplankton quantity but strong on phytoplankton quality. The phytoplankton had lower eicosapentaenoic acid (EPA) content and higher P content (lower seston C:P) in Abisko compared to in Jämtland. In addition, the quality of the DOC (as indicated by its aromaticity and SUVA) influenced not only the light conditions and the seston C:P ratios, but also the FA composition. We found higher bacteria FA concentrations in seston in Abisko than in Jämtland, despite lower amounts of FA of terrestrial origin in Abisko. Our findings suggest that declining N deposition and enhanced colored terrestrial C loadings leads to lower nutritional quality of basal resources for higher consumers in mountain lakes.

@article{rocherros_stream_2020,
	title = {Stream metabolism controls diel patterns and evasion of {CO} $_{\textrm{2}}$ in {Arctic} streams},
	volume = {26},
	issn = {1354-1013, 1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14895},
	doi = {10.1111/gcb.14895},
	abstract = {Streams play an important role in the global carbon (C) cycle, accounting for a large portion of CO2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 production and evasion from streams remains poorly understood. In this study, we measured O2 and CO2 continuously in streams draining tundra-dominated catchments in northern Sweden, during the summers of 2015 and 2016. From this, we estimated daily metabolic rates and CO2 evasion simultaneously and thus provide insight into the role of stream metabolism as a driver of C dynamics in Arctic streams. Our results show that aquatic biological processes regulate CO2 concentrations and evasion at multiple timescales. Photosynthesis caused CO2 concentrations to decrease by as much as 900 ppm during the day, with the magnitude of this diel variation being strongest at the low-turbulence streams. Diel patterns in CO2 concentrations in turn influenced evasion, with up to 45\% higher rates at night. Throughout the summer, CO2 evasion was sustained by aquatic ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases, the contribution of stream respiration exceeded CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, thus creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO2 evasion in the Arctic and demonstrate that stream metabolic processes are key drivers of the transformation and fate of terrestrial organic matter exported from these landscapes.},
	language = {en},
	number = {3},
	urldate = {2020-03-19},
	journal = {Global Change Biology},
	author = {Rocher‐Ros, Gerard and Sponseller, Ryan A. and Bergström, Ann‐Kristin and Myrstener, Maria and Giesler, Reiner},
	month = mar,
	year = {2020},
	keywords = {\#nosource},
	pages = {1400--1413},
}

Streams play an important role in the global carbon (C) cycle, accounting for a large portion of CO2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 production and evasion from streams remains poorly understood. In this study, we measured O2 and CO2 continuously in streams draining tundra-dominated catchments in northern Sweden, during the summers of 2015 and 2016. From this, we estimated daily metabolic rates and CO2 evasion simultaneously and thus provide insight into the role of stream metabolism as a driver of C dynamics in Arctic streams. Our results show that aquatic biological processes regulate CO2 concentrations and evasion at multiple timescales. Photosynthesis caused CO2 concentrations to decrease by as much as 900 ppm during the day, with the magnitude of this diel variation being strongest at the low-turbulence streams. Diel patterns in CO2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO2 evasion was sustained by aquatic ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases, the contribution of stream respiration exceeded CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, thus creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO2 evasion in the Arctic and demonstrate that stream metabolic processes are key drivers of the transformation and fate of terrestrial organic matter exported from these landscapes.

@article{liu_vegetation_2020,
	title = {Vegetation and soil responses to added carbon and nutrients remain six years after discontinuation of long-term treatments},
	volume = {722},
	issn = {0048-9697},
	url = {http://www.sciencedirect.com/science/article/pii/S004896972031398X},
	doi = {10.1016/j.scitotenv.2020.137885},
	abstract = {Global warming and increased nutrient availability in the Arctic have attracted wide attention. However, it is unknown how an increased supply of nitrogen (N), phosphorus (P) and/or labile carbon (C) – alone and in combinations – affects the concentrations and pools of C and nutrients in plants, soil and soil microorganisms, and whether the cessation of these additions allows the ecosystem to recover from amendments. Six treatments (control, C, N, P, NP and C + NP) were applied at a subarctic heath for 8–10 years. After being untreated for two years, amendments were re-applied to one half of the plots for four years while the other plot half received no amendments. When the plots were harvested, we could therefore compare responses in plots with nearly continuous 14–16-year amendments to those with six years with discontinued treatments. The responses to individual and combined nutrient additions were mostly similar in re-initiated and discontinued plots. Individual N addition strongly increased the C and N pools in the graminoids, thereby also increasing the C and N pools in litter and fine roots compared to the plots without added N. This contributed to the increased microbial biomass C and total C in soil. P addition alone increased C and N pools in vascular cryptogams, as well as PO43−, NH4+, dissolved organic carbon and dissolved organic nitrogen concentrations in soil compared to the plots without added P. Hence, plant functional groups showed differential responses to long-term N and P amendment, and after the initial nutrient additions for 8–10 years, the investigated subarctic tundra ecosystem had reached a new steady state that was resilient to further changes still six years after cessation of additions.},
	language = {en},
	urldate = {2020-04-23},
	journal = {Science of The Total Environment},
	author = {Liu, Na and Michelsen, Anders and Rinnan, Riikka},
	month = jun,
	year = {2020},
	keywords = {\#nosource, Arctic vegetation, Fertilization, Nitrogen, Nutrient limitation, Phosphorus, Tundra ecosystem},
	pages = {137885},
}

Global warming and increased nutrient availability in the Arctic have attracted wide attention. However, it is unknown how an increased supply of nitrogen (N), phosphorus (P) and/or labile carbon (C) – alone and in combinations – affects the concentrations and pools of C and nutrients in plants, soil and soil microorganisms, and whether the cessation of these additions allows the ecosystem to recover from amendments. Six treatments (control, C, N, P, NP and C + NP) were applied at a subarctic heath for 8–10 years. After being untreated for two years, amendments were re-applied to one half of the plots for four years while the other plot half received no amendments. When the plots were harvested, we could therefore compare responses in plots with nearly continuous 14–16-year amendments to those with six years with discontinued treatments. The responses to individual and combined nutrient additions were mostly similar in re-initiated and discontinued plots. Individual N addition strongly increased the C and N pools in the graminoids, thereby also increasing the C and N pools in litter and fine roots compared to the plots without added N. This contributed to the increased microbial biomass C and total C in soil. P addition alone increased C and N pools in vascular cryptogams, as well as PO43−, NH4+, dissolved organic carbon and dissolved organic nitrogen concentrations in soil compared to the plots without added P. Hence, plant functional groups showed differential responses to long-term N and P amendment, and after the initial nutrient additions for 8–10 years, the investigated subarctic tundra ecosystem had reached a new steady state that was resilient to further changes still six years after cessation of additions.

@article{isles_does_2020,
	title = {Does browning affect the identity of limiting nutrients in lakes?},
	volume = {82},
	issn = {1420-9055},
	url = {https://doi.org/10.1007/s00027-020-00718-y},
	doi = {10.1007/s00027-020-00718-y},
	abstract = {Concentrations of dissolved organic carbon (DOC) have increased recently in many lakes at high latitudes in North America and Europe, but it is unclear what effect this will have on the identity of the limiting nutrient for phytoplankton [nitrogen (N) vs. phosphorus (P)]. Identifying the effect of changing DOC on phytoplankton nutrient limitation is complicated by spatial covariation between atmospheric N deposition and increasing DOC in areas where lake browning occurs. We conducted nutrient-limitation assays in 27 lakes from three sites along gradients of climate and atmospheric N deposition in Sweden. Within each site, lakes were selected to represent the range of DOC concentrations. We also conducted statistical analyses of large-scale lake survey data (n = 4768 lakes divided into 47 regions) to investigate relationships between DOC and nutrient stoichiometry while controlling for differences in N deposition. Our findings confirmed that most lakes were dual-limited by both N and P in the south, whereas northern lakes were primarily N-limited. Throughout Sweden the ratio of dissolved inorganic nitrogen (DIN) to total phosphorus (TP) declined with increasing DOC in most regions, suggesting that browner lakes are more likely to be N limited. These results were not supported by our nutrient limitation assays, which identified no relationship between DOC and relative strength of limitation by N or P. Increased DOC also resulted in significant increases in both total and inorganic N and P fractions, suggesting that other factors such as light limitation or increased top-down control become more important as DOC increases.},
	language = {en},
	number = {2},
	urldate = {2020-04-23},
	journal = {Aquatic Sciences},
	author = {Isles, Peter D. F. and Jonsson, Anders and Creed, Irena F. and Bergström, Ann-Kristin},
	month = mar,
	year = {2020},
	keywords = {\#nosource},
	pages = {45},
}

Concentrations of dissolved organic carbon (DOC) have increased recently in many lakes at high latitudes in North America and Europe, but it is unclear what effect this will have on the identity of the limiting nutrient for phytoplankton [nitrogen (N) vs. phosphorus (P)]. Identifying the effect of changing DOC on phytoplankton nutrient limitation is complicated by spatial covariation between atmospheric N deposition and increasing DOC in areas where lake browning occurs. We conducted nutrient-limitation assays in 27 lakes from three sites along gradients of climate and atmospheric N deposition in Sweden. Within each site, lakes were selected to represent the range of DOC concentrations. We also conducted statistical analyses of large-scale lake survey data (n = 4768 lakes divided into 47 regions) to investigate relationships between DOC and nutrient stoichiometry while controlling for differences in N deposition. Our findings confirmed that most lakes were dual-limited by both N and P in the south, whereas northern lakes were primarily N-limited. Throughout Sweden the ratio of dissolved inorganic nitrogen (DIN) to total phosphorus (TP) declined with increasing DOC in most regions, suggesting that browner lakes are more likely to be N limited. These results were not supported by our nutrient limitation assays, which identified no relationship between DOC and relative strength of limitation by N or P. Increased DOC also resulted in significant increases in both total and inorganic N and P fractions, suggesting that other factors such as light limitation or increased top-down control become more important as DOC increases.

@article{gomez-gener_drought_2020,
	title = {Drought alters the biogeochemistry of boreal stream networks},
	volume = {11},
	copyright = {2020 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-020-15496-2},
	doi = {10.1038/s41467-020-15496-2},
	abstract = {High latitude droughts are increasing, but their effects on freshwater systems are poorly understood. Here the authors investigate Sweden’s most severe drought in the last century and show that these dry conditions induce hypoxia and elevated methane production from streams.},
	language = {en},
	number = {1},
	urldate = {2020-04-23},
	journal = {Nature Communications},
	author = {Gómez-Gener, Lluís and Lupon, Anna and Laudon, Hjalmar and Sponseller, Ryan A.},
	month = apr,
	year = {2020},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {1--11},
}

High latitude droughts are increasing, but their effects on freshwater systems are poorly understood. Here the authors investigate Sweden’s most severe drought in the last century and show that these dry conditions induce hypoxia and elevated methane production from streams.

@article{lidman_availability_2020,
	title = {Availability of specific prey types impact pied flycatcher ({Ficedula} hypoleuca) nestling health in a moderately lead contaminated environment in northern {Sweden}},
	volume = {257},
	issn = {0269-7491},
	url = {http://www.sciencedirect.com/science/article/pii/S0269749119324418},
	doi = {10.1016/j.envpol.2019.113478},
	abstract = {Anthropogenic metal contamination can cause increased stress in exposed organisms, but it can be difficult to disentangle the anthropogenic influence from natural variation in environmental conditions. In the proximity of a closed lead (Pb)/zinc (Zn) mine in northern Sweden, the health effects of Pb exposure, essential element (calcium [Ca] and Zn) uptake, and prey availability and composition were estimated on pied flycatcher (Ficedula hypoleuca) nestlings, using hemoglobin (Hb) level as a proxy for health. Pb concentration in nestling blood range between 0.00034 and 2.21 μg/g (ww) and nestlings close to the mine had higher Pb concentrations and lower Hb, but contrary to our hypothesis, Hb was not directly related to Pb accumulation. Proportions of flying terrestrial and aquatic insects in available prey and availability of flying terrestrial insects were positively associated with nestling Hb, whereas the proportion of terrestrial ground living prey, the most common prey type, showed a negative association. This suggests that positive influence of certain prey, which does not have to be the most common in the surroundings, can counteract the negative effects from Pb contamination on bird health. Nestlings inhabiting sites adjacent to lakes had an advantage in terms of prey composition and availability of preferred prey, which resulted in higher Hb. As such, our results show that during moderate exposure to metals, variation in natural conditions, such as prey availability, can have great impact on organism health compared to Pb exposure.},
	language = {en},
	urldate = {2020-04-23},
	journal = {Environmental Pollution},
	author = {Lidman, Johan and Jonsson, Micael and Berglund, Åsa M. M.},
	month = feb,
	year = {2020},
	keywords = {\#nosource, Anthropogenic stressor, Hemoglobin, Metal exposure, Passerine, Prey availability},
	pages = {113478},
}

Anthropogenic metal contamination can cause increased stress in exposed organisms, but it can be difficult to disentangle the anthropogenic influence from natural variation in environmental conditions. In the proximity of a closed lead (Pb)/zinc (Zn) mine in northern Sweden, the health effects of Pb exposure, essential element (calcium [Ca] and Zn) uptake, and prey availability and composition were estimated on pied flycatcher (Ficedula hypoleuca) nestlings, using hemoglobin (Hb) level as a proxy for health. Pb concentration in nestling blood range between 0.00034 and 2.21 μg/g (ww) and nestlings close to the mine had higher Pb concentrations and lower Hb, but contrary to our hypothesis, Hb was not directly related to Pb accumulation. Proportions of flying terrestrial and aquatic insects in available prey and availability of flying terrestrial insects were positively associated with nestling Hb, whereas the proportion of terrestrial ground living prey, the most common prey type, showed a negative association. This suggests that positive influence of certain prey, which does not have to be the most common in the surroundings, can counteract the negative effects from Pb contamination on bird health. Nestlings inhabiting sites adjacent to lakes had an advantage in terms of prey composition and availability of preferred prey, which resulted in higher Hb. As such, our results show that during moderate exposure to metals, variation in natural conditions, such as prey availability, can have great impact on organism health compared to Pb exposure.

@article{halbritter_handbook_2020,
	title = {The handbook for standardized field and laboratory measurements in terrestrial climate change experiments and observational studies ({ClimEx})},
	volume = {11},
	copyright = {© 2019 The Authors. Methods in Ecology and Evolution published by John Wiley \& Sons Ltd on behalf of British Ecological Society.},
	issn = {2041-210X},
	url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13331},
	doi = {10.1111/2041-210X.13331},
	abstract = {Climate change is a world-wide threat to biodiversity and ecosystem structure, functioning and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate change impacts across the soil–plant–atmosphere continuum. An increasing number of climate change studies are creating new opportunities for meaningful and high-quality generalizations and improved process understanding. However, significant challenges exist related to data availability and/or compatibility across studies, compromising opportunities for data re-use, synthesis and upscaling. Many of these challenges relate to a lack of an established ‘best practice’ for measuring key impacts and responses. This restrains our current understanding of complex processes and mechanisms in terrestrial ecosystems related to climate change. To overcome these challenges, we collected best-practice methods emerging from major ecological research networks and experiments, as synthesized by 115 experts from across a wide range of scientific disciplines. Our handbook contains guidance on the selection of response variables for different purposes, protocols for standardized measurements of 66 such response variables and advice on data management. Specifically, we recommend a minimum subset of variables that should be collected in all climate change studies to allow data re-use and synthesis, and give guidance on additional variables critical for different types of synthesis and upscaling. The goal of this community effort is to facilitate awareness of the importance and broader application of standardized methods to promote data re-use, availability, compatibility and transparency. We envision improved research practices that will increase returns on investments in individual research projects, facilitate second-order research outputs and create opportunities for collaboration across scientific communities. Ultimately, this should significantly improve the quality and impact of the science, which is required to fulfil society's needs in a changing world.},
	language = {en},
	number = {1},
	urldate = {2020-04-23},
	journal = {Methods in Ecology and Evolution},
	author = {Halbritter, Aud H. and Boeck, Hans J. De and Eycott, Amy E. and Reinsch, Sabine and Robinson, David A. and Vicca, Sara and Berauer, Bernd and Christiansen, Casper T. and Estiarte, Marc and Grünzweig, José M. and Gya, Ragnhild and Hansen, Karin and Jentsch, Anke and Lee, Hanna and Linder, Sune and Marshall, John and Peñuelas, Josep and Schmidt, Inger Kappel and Stuart‐Haëntjens, Ellen and Wilfahrt, Peter and Vandvik, Vigdis},
	year = {2020},
	note = {\_eprint: https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13331},
	keywords = {\#nosource, best practice, coordinated experiments, data management and documentation, ecosystem, experimental macroecology, methodology, open science, vegetation},
	pages = {22--37},
}

Climate change is a world-wide threat to biodiversity and ecosystem structure, functioning and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate change impacts across the soil–plant–atmosphere continuum. An increasing number of climate change studies are creating new opportunities for meaningful and high-quality generalizations and improved process understanding. However, significant challenges exist related to data availability and/or compatibility across studies, compromising opportunities for data re-use, synthesis and upscaling. Many of these challenges relate to a lack of an established ‘best practice’ for measuring key impacts and responses. This restrains our current understanding of complex processes and mechanisms in terrestrial ecosystems related to climate change. To overcome these challenges, we collected best-practice methods emerging from major ecological research networks and experiments, as synthesized by 115 experts from across a wide range of scientific disciplines. Our handbook contains guidance on the selection of response variables for different purposes, protocols for standardized measurements of 66 such response variables and advice on data management. Specifically, we recommend a minimum subset of variables that should be collected in all climate change studies to allow data re-use and synthesis, and give guidance on additional variables critical for different types of synthesis and upscaling. The goal of this community effort is to facilitate awareness of the importance and broader application of standardized methods to promote data re-use, availability, compatibility and transparency. We envision improved research practices that will increase returns on investments in individual research projects, facilitate second-order research outputs and create opportunities for collaboration across scientific communities. Ultimately, this should significantly improve the quality and impact of the science, which is required to fulfil society's needs in a changing world.

@article{hicks_simulated_2020,
	title = {Simulated rhizosphere deposits induce microbial {N}-mining that may accelerate shrubification in the subarctic},
	volume = {n/a},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {1939-9170},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.3094},
	doi = {10.1002/ecy.3094},
	abstract = {Climate change is exposing high-latitude systems to warming and a shift towards more shrub-dominated plant communities, resulting in increased leaf-litter inputs at the soil surface, and more labile root-derived organic matter (OM) input in the soil profile. Labile OM can stimulate the mineralization of soil organic matter (SOM); a phenomenon termed “priming”. In N-poor subarctic soils, it is hypothesized that microorganisms may “prime” SOM in order to acquire N (“microbial N-mining”). Increased leaf-litter inputs with a high C/N ratio might further exacerbate microbial N demand, and increase the susceptibility of N-poor soils to N-mining. We investigated the N-control of SOM mineralization by amending soils from climate change simulation treatments in the subarctic (+1.1°C warming, birch litter addition, willow litter addition, and fungal sporocarp addition) with labile OM either in the form of glucose (labile C; equivalent to 400 µg C g-1 fwt soil) or alanine (labile C + N; equivalent to 400 µg C and 157 µg N g-1 fwt soil), to simulate rhizosphere inputs. Surprisingly, we found that despite five-years of simulated climate change treatments, there were no significant effects of the field-treatments on microbial process rates, community structure or responses to labile OM. Glucose primed the mineralization of both C and N from SOM, but gross mineralization of N was stimulated more than that of C, suggesting that microbial SOM-use increased in magnitude and shifted to components richer in N (i.e. selective microbial N-mining). The addition of alanine also resulted in priming of both C and N mineralization, but the N mineralization stimulated by alanine was greater than that stimulated by glucose, indicating strong N-mining even when a source of labile OM including N was supplied. Microbial carbon use efficiency was reduced in response to both labile OM inputs. Overall, these findings suggest that shrub-expansion could fundamentally alter biogeochemical cycling in the subarctic, yielding more N available for plant uptake in these N-limited soils, thus driving positive plant-soil feedbacks.},
	language = {en},
	number = {n/a},
	urldate = {2020-05-29},
	journal = {Ecology},
	author = {Hicks, Lettice C. and Leizeaga, Ainara and Rousk, Kathrin and Michelsen, Anders and Rousk, Johannes},
	month = may,
	year = {2020},
	note = {\_eprint: https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecy.3094},
	keywords = {\#nosource, carbon and nitrogen mineralization, climate change, microbial carbon use efficiency, nitrogen limitation, nitrogen-mining, rhizosphere biogeochemistry, soil priming effect, subarctic tundra},
	pages = {e03094},
}

Climate change is exposing high-latitude systems to warming and a shift towards more shrub-dominated plant communities, resulting in increased leaf-litter inputs at the soil surface, and more labile root-derived organic matter (OM) input in the soil profile. Labile OM can stimulate the mineralization of soil organic matter (SOM); a phenomenon termed “priming”. In N-poor subarctic soils, it is hypothesized that microorganisms may “prime” SOM in order to acquire N (“microbial N-mining”). Increased leaf-litter inputs with a high C/N ratio might further exacerbate microbial N demand, and increase the susceptibility of N-poor soils to N-mining. We investigated the N-control of SOM mineralization by amending soils from climate change simulation treatments in the subarctic (+1.1°C warming, birch litter addition, willow litter addition, and fungal sporocarp addition) with labile OM either in the form of glucose (labile C; equivalent to 400 µg C g-1 fwt soil) or alanine (labile C + N; equivalent to 400 µg C and 157 µg N g-1 fwt soil), to simulate rhizosphere inputs. Surprisingly, we found that despite five-years of simulated climate change treatments, there were no significant effects of the field-treatments on microbial process rates, community structure or responses to labile OM. Glucose primed the mineralization of both C and N from SOM, but gross mineralization of N was stimulated more than that of C, suggesting that microbial SOM-use increased in magnitude and shifted to components richer in N (i.e. selective microbial N-mining). The addition of alanine also resulted in priming of both C and N mineralization, but the N mineralization stimulated by alanine was greater than that stimulated by glucose, indicating strong N-mining even when a source of labile OM including N was supplied. Microbial carbon use efficiency was reduced in response to both labile OM inputs. Overall, these findings suggest that shrub-expansion could fundamentally alter biogeochemical cycling in the subarctic, yielding more N available for plant uptake in these N-limited soils, thus driving positive plant-soil feedbacks.

@article{sofo_comparing_2020,
	title = {Comparing the effects of soil fauna on litter decomposition and organic matter turnover in sustainably and conventionally managed olive orchards},
	volume = {372},
	issn = {0016-7061},
	url = {http://www.sciencedirect.com/science/article/pii/S0016706119325935},
	doi = {10.1016/j.geoderma.2020.114393},
	abstract = {Soils and crops in Mediterranean agrosystems are vulnerable to climate change and environmental stresses, and they will be more and more in the next future. In this scenario, soil organic matter (SOM) plays a crucial role and its level is principally determined by the continuous physical and chemical action of soil fauna. While the importance of microorganisms in fruit agrosystems has been extensively and recently highlighted, the role of soil fauna - and particularly of macrofauna - to ecosystem services has been often overlooked. On this basis, the aim of this study was to characterize and compare C/N dynamics and other soil physicochemical parameters, soil macrofauna abundance, bioturbation and litter/SOM decomposition indices in a Mediterranean olive (Olea europaea L.) orchard subjected to two different soil management systems (namely sustainable, Smng, and conventional, Cmng) for 18 years. The adoption of the Smng system significantly increased almost three times the abundance of earthworms and two times that of other soil macrofauna. Bioturbation due to soil fauna and roots was significantly higher in the Smng system, and this caused a significantly faster SOM decomposition measured both in 90-day incubated local litter bags (decomposition constant = 0.092 and 0.072 in the Smng and Cmng system, respectively) and in tea bags (decomposition rate constant = 0.018 and 0.010 in the Smng and Cmng system, respectively). Soil C and N dynamics were also affected by different soil management. The results highlighted that the soil chemical quality of the Smng system is the result of the higher abundance and activity of soil fauna, in terms of enhanced litter decomposition and bioturbation. From the general analysis of the data obtained, it emerged that the role of soil fauna should be seriously taken into account in land management strategies not exclusively oriented to fruit yield and quality, but also to soil fertility restoration.},
	language = {en},
	urldate = {2020-05-29},
	journal = {Geoderma},
	author = {Sofo, Adriano and Nicoletta Mininni, Alba and Ricciuti, Patrizia},
	month = aug,
	year = {2020},
	keywords = {\#nosource, Bioturbation, Litter decomposition, Olive orchards, Soil fauna, Sustainable land use, Tea bags},
	pages = {114393},
}

Soils and crops in Mediterranean agrosystems are vulnerable to climate change and environmental stresses, and they will be more and more in the next future. In this scenario, soil organic matter (SOM) plays a crucial role and its level is principally determined by the continuous physical and chemical action of soil fauna. While the importance of microorganisms in fruit agrosystems has been extensively and recently highlighted, the role of soil fauna - and particularly of macrofauna - to ecosystem services has been often overlooked. On this basis, the aim of this study was to characterize and compare C/N dynamics and other soil physicochemical parameters, soil macrofauna abundance, bioturbation and litter/SOM decomposition indices in a Mediterranean olive (Olea europaea L.) orchard subjected to two different soil management systems (namely sustainable, Smng, and conventional, Cmng) for 18 years. The adoption of the Smng system significantly increased almost three times the abundance of earthworms and two times that of other soil macrofauna. Bioturbation due to soil fauna and roots was significantly higher in the Smng system, and this caused a significantly faster SOM decomposition measured both in 90-day incubated local litter bags (decomposition constant = 0.092 and 0.072 in the Smng and Cmng system, respectively) and in tea bags (decomposition rate constant = 0.018 and 0.010 in the Smng and Cmng system, respectively). Soil C and N dynamics were also affected by different soil management. The results highlighted that the soil chemical quality of the Smng system is the result of the higher abundance and activity of soil fauna, in terms of enhanced litter decomposition and bioturbation. From the general analysis of the data obtained, it emerged that the role of soil fauna should be seriously taken into account in land management strategies not exclusively oriented to fruit yield and quality, but also to soil fertility restoration.

@article{ahmed_recent_2020,
	title = {Recent {Trends} in {Freshwater} {Influx} to the {Arctic} {Ocean} from {Four} {Major} {Arctic}-{Draining} {Rivers}},
	volume = {12},
	issn = {2073-4441},
	url = {https://www.mdpi.com/2073-4441/12/4/1189},
	doi = {10.3390/w12041189},
	abstract = {Runoff from Arctic rivers constitutes a major freshwater influx to the Arctic Ocean. In these nival-dominated river systems, the majority of annual discharge is released during the spring snowmelt period. The circulation regime of the salinity-stratified Arctic Ocean is connected to global earth–ocean dynamics through thermohaline circulation; hence, variability in freshwater input from the Arctic flowing rivers has important implications for the global climate system. Daily discharge data from each of the four largest Arctic-draining river watersheds (Mackenzie, Ob, Lena and Yenisei; herein referred to as MOLY) are analyzed to identify historic changes in the magnitude and timing of freshwater input to the Arctic Ocean with emphasis on the spring freshet. Results show that the total freshwater influx to the Arctic Ocean increased by 89 km3/decade, amounting to a 14\% increase during the 30-year period from 1980 to 2009. A distinct shift towards earlier melt timing is also indicated by proportional increases in fall, winter and spring discharges (by 2.5\%, 1.3\% and 2.5\% respectively) followed by a decrease (by 5.8\%) in summer discharge as a percentage of the mean annual flow. This seasonal increase in discharge and earlier pulse onset dates indicates a general shift towards a flatter, broad-based hydrograph with earlier peak discharges. The study also reveals that the increasing trend in freshwater discharge to the Arctic Ocean is not solely due to increased spring freshet discharge, but is a combination of increases in all seasons except that of the summer.},
	language = {en},
	number = {4},
	urldate = {2020-05-29},
	journal = {Water},
	author = {Ahmed, Roxanne and Prowse, Terry and Dibike, Yonas and Bonsal, Barrie and O’Neil, Hayley},
	month = apr,
	year = {2020},
	keywords = {\#nosource},
	pages = {1189},
}

Runoff from Arctic rivers constitutes a major freshwater influx to the Arctic Ocean. In these nival-dominated river systems, the majority of annual discharge is released during the spring snowmelt period. The circulation regime of the salinity-stratified Arctic Ocean is connected to global earth–ocean dynamics through thermohaline circulation; hence, variability in freshwater input from the Arctic flowing rivers has important implications for the global climate system. Daily discharge data from each of the four largest Arctic-draining river watersheds (Mackenzie, Ob, Lena and Yenisei; herein referred to as MOLY) are analyzed to identify historic changes in the magnitude and timing of freshwater input to the Arctic Ocean with emphasis on the spring freshet. Results show that the total freshwater influx to the Arctic Ocean increased by 89 km3/decade, amounting to a 14% increase during the 30-year period from 1980 to 2009. A distinct shift towards earlier melt timing is also indicated by proportional increases in fall, winter and spring discharges (by 2.5%, 1.3% and 2.5% respectively) followed by a decrease (by 5.8%) in summer discharge as a percentage of the mean annual flow. This seasonal increase in discharge and earlier pulse onset dates indicates a general shift towards a flatter, broad-based hydrograph with earlier peak discharges. The study also reveals that the increasing trend in freshwater discharge to the Arctic Ocean is not solely due to increased spring freshet discharge, but is a combination of increases in all seasons except that of the summer.

@article{grosbois_efficiency_2020,
	title = {Efficiency of crustacean zooplankton in transferring allochthonous carbon in a boreal lake},
	volume = {101},
	issn = {1939-9170},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.3013},
	doi = {10.1002/ecy.3013},
	abstract = {Increased incorporation of terrestrial organic matter (t-OM) into consumer biomass (allochthony) is believed to reduce growth capacity. In this study, we examined the relationship between crustacean zooplankton allochthony and production in a boreal lake that displays strong seasonal variability in t-OM inputs. Contrary to our hypotheses, we found no effect of allochthony on production at the community and the species levels. The high frequency seasonal sampling (time-for-space) allowed for estimating the efficiency of zooplankton in converting this external carbon source to growth. From the daily t-OM inputs in the lake (57 – 3027 kg C per day), the zooplankton community transferred 0.2\% into biomass (0.01 – 2.36 kg C per day); this level was of the same magnitude as the carbon transfer efficiency for algal-derived carbon (0.4\%). In the context of the boundless carbon cycle which integrates inland waters as a biologically active component of the terrestrial landscape, the use of the time-for-space approach for the quantifying of t-OM trophic transfer efficiency by zooplankton is a critical step toward a better understanding of the effects of increasing external carbon fluxes on pelagic food webs.},
	language = {en},
	number = {6},
	urldate = {2020-03-19},
	journal = {Ecology},
	author = {Grosbois, Guillaume and Vachon, Dominic and Giorgio, Paul del and Rautio, Milla},
	month = feb,
	year = {2020},
	note = {\_eprint: https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecy.3013},
	keywords = {\#nosource, Allochthony, Cyclops scutifer, Daphnia, Leptodiaptomus minutus, allochtrophy, carbon transfer efficiency, seasonal pattern, secondary production, stable isotopes},
	pages = {e03013},
}

Increased incorporation of terrestrial organic matter (t-OM) into consumer biomass (allochthony) is believed to reduce growth capacity. In this study, we examined the relationship between crustacean zooplankton allochthony and production in a boreal lake that displays strong seasonal variability in t-OM inputs. Contrary to our hypotheses, we found no effect of allochthony on production at the community and the species levels. The high frequency seasonal sampling (time-for-space) allowed for estimating the efficiency of zooplankton in converting this external carbon source to growth. From the daily t-OM inputs in the lake (57 – 3027 kg C per day), the zooplankton community transferred 0.2% into biomass (0.01 – 2.36 kg C per day); this level was of the same magnitude as the carbon transfer efficiency for algal-derived carbon (0.4%). In the context of the boundless carbon cycle which integrates inland waters as a biologically active component of the terrestrial landscape, the use of the time-for-space approach for the quantifying of t-OM trophic transfer efficiency by zooplankton is a critical step toward a better understanding of the effects of increasing external carbon fluxes on pelagic food webs.

@article{egelkraut_reindeer_2020,
	title = {Reindeer trampling promotes vegetation changes in tundra heathlands: results from a simulation experiment.},
	volume = {31},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {1654-1103},
	shorttitle = {Reindeer trampling promotes vegetation changes in tundra heathlands},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.12871},
	doi = {10.1111/jvs.12871},
	abstract = {Question Herbivores exert strong influences on vegetation through activities such as trampling, defoliation, and fertilization. The combined effect of these activities on plant performance may cause dramatic vegetation shifts. Because herbivore pressures and the relative importance of their different activities are not equally distributed across the landscape, it is important to understand their isolated effect. One example of an herbivore-induced vegetation shift is the reindeer-driven transition from a subarctic tundra vegetation dominated by dwarf shrubs into a more productive, graminoid-dominated state. Here, we asked how each of the grazing activities by reindeer separately and combined, shape vegetation composition. Location Nordreisa, Norway. Methods We used a field experiment over six summers to study the separate and interacting effects of reindeer trampling, defoliation, feces addition and moss removal on tundra heath vegetation, and to identify which of these factors were most important in driving the plant community towards a graminoid-dominated state. Results The combination of all treatments resulted in the strongest vegetation changes, but trampling was the single most important factor altering the vegetation composition by reducing the abundance of both evergreen and deciduous dwarf shrubs. In contrast to what we expected, none of our treatments, separate or combined, resulted in an increased abundance of graminoids in five years, although such rapid vegetation changes have been observed in the field; in similar environmental conditions. Conclusions Trampling is the key process by which reindeer influence the abundance of functional groups, but only many processes combined result in strong changes in community composition. Moreover, additional factors not included in this experiment, such as urine, may be important in causing a state shift to a graminoid-dominated community.},
	language = {en},
	number = {3},
	urldate = {2020-03-19},
	journal = {Journal of Vegetation Science},
	author = {Egelkraut, Dagmar and Barthelemy, Hélène and Olofsson, Johan},
	month = feb,
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvs.12871},
	keywords = {\#nosource, Defoliation, Rangifer tarandus, fertilization, grazing simulation, herbivory, shrubification, trampling, vegetation shifts},
	pages = {476--486},
}

Question Herbivores exert strong influences on vegetation through activities such as trampling, defoliation, and fertilization. The combined effect of these activities on plant performance may cause dramatic vegetation shifts. Because herbivore pressures and the relative importance of their different activities are not equally distributed across the landscape, it is important to understand their isolated effect. One example of an herbivore-induced vegetation shift is the reindeer-driven transition from a subarctic tundra vegetation dominated by dwarf shrubs into a more productive, graminoid-dominated state. Here, we asked how each of the grazing activities by reindeer separately and combined, shape vegetation composition. Location Nordreisa, Norway. Methods We used a field experiment over six summers to study the separate and interacting effects of reindeer trampling, defoliation, feces addition and moss removal on tundra heath vegetation, and to identify which of these factors were most important in driving the plant community towards a graminoid-dominated state. Results The combination of all treatments resulted in the strongest vegetation changes, but trampling was the single most important factor altering the vegetation composition by reducing the abundance of both evergreen and deciduous dwarf shrubs. In contrast to what we expected, none of our treatments, separate or combined, resulted in an increased abundance of graminoids in five years, although such rapid vegetation changes have been observed in the field; in similar environmental conditions. Conclusions Trampling is the key process by which reindeer influence the abundance of functional groups, but only many processes combined result in strong changes in community composition. Moreover, additional factors not included in this experiment, such as urine, may be important in causing a state shift to a graminoid-dominated community.

@article{truchy_habitat_2020,
	title = {Habitat patchiness, ecological connectivity and the uneven recovery of boreal stream ecosystems from an experimental drought},
	volume = {26},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15063},
	doi = {10.1111/gcb.15063},
	abstract = {Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (i) algal biomass accrual, (ii) microbial respiration and (iii) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An eight-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal die-back began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world’s vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.},
	language = {en},
	number = {6},
	urldate = {2020-03-18},
	journal = {Global Change Biology},
	author = {Truchy, Amélie and Sarremejane, Romain and Muotka, Timo and Mykrä, Heikki and Angeler, David G. and Lehosmaa, Kaisa and Huusko, Ari and Johnson, Richard K. and Sponseller, Ryan A. and McKie, Brendan G.},
	month = mar,
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15063},
	keywords = {\#nosource, Algal production, Detritivores, Drought, Ecosystem processes, Habitat patch, Hyphomycete fungi, Meta-ecosystem, Spatial connectivity},
	pages = {3455--3472},
}

Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (i) algal biomass accrual, (ii) microbial respiration and (iii) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An eight-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal die-back began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world’s vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.

@article{ochoahueso_microbial_2020,
	title = {Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands},
	volume = {28},
	copyright = {© 2020 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15146},
	doi = {10.1111/gcb.15146},
	abstract = {Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.},
	language = {en},
	number = {6},
	urldate = {2020-07-13},
	journal = {Global Change Biology},
	author = {Ochoa‐Hueso, Raúl and Borer, Elizabeth T. and Seabloom, Eric W. and Hobbie, Sarah E. and Risch, Anita C. and Collins, Scott L. and Alberti, Juan and Bahamonde, Héctor A. and Brown, Cynthia S. and Caldeira, Maria C. and Daleo, Pedro and Dickman, Chris R. and Ebeling, Anne and Eisenhauer, Nico and Esch, Ellen H. and Eskelinen, Anu and Fernández, Victoria and Güsewell, Sabine and Gutierrez‐Larruga, Blanca and Hofmockel, Kirsten and Laungani, Ramesh and Lind, Eric and López, Andrea and McCulley, Rebecca L. and Moore, Joslin L. and Peri, Pablo L. and Power, Sally A. and Price, Jodi N. and Prober, Suzanne M. and Roscher, Christiane and Sarneel, Judith M. and Schütz, Martin and Siebert, Julia and Standish, Rachel J. and Ayuso, Sergio Velasco and Virtanen, Risto and Wardle, Glenda M. and Wiehl, Georg and Yahdjian, Laura and Zamin, Tara},
	month = jun,
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.15146},
	keywords = {\#nosource, NutNet, carbon cycling and sequestration, decomposition, eutrophication, fertilization, microbial activity, nutrient (co-)limitation},
	pages = {4572--4582},
}

Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.

@article{keuper_carbon_2020,
	title = {Carbon loss from northern circumpolar permafrost soils amplified by rhizosphere priming},
	volume = {13},
	copyright = {2020 The Author(s), under exclusive licence to Springer Nature Limited},
	issn = {1752-0908},
	url = {https://www.nature.com/articles/s41561-020-0607-0},
	doi = {10.1038/s41561-020-0607-0},
	abstract = {As global temperatures continue to rise, a key uncertainty of climate projections is the microbial decomposition of vast organic carbon stocks in thawing permafrost soils. Decomposition rates can accelerate up to fourfold in the presence of plant roots, and this mechanism—termed the rhizosphere priming effect—may be especially relevant to thawing permafrost soils as rising temperatures also stimulate plant productivity in the Arctic. However, priming is currently not explicitly included in any model projections of future carbon losses from the permafrost area. Here, we combine high-resolution spatial and depth-resolved datasets of key plant and permafrost properties with empirical relationships of priming effects from living plants on microbial respiration. We show that rhizosphere priming amplifies overall soil respiration in permafrost-affected ecosystems by {\textasciitilde}12\%, which translates to a priming-induced absolute loss of {\textasciitilde}40 Pg soil carbon from the northern permafrost area by 2100. Our findings highlight the need to include fine-scale ecological interactions in order to accurately predict large-scale greenhouse gas emissions, and suggest even tighter restrictions on the estimated 200 Pg anthropogenic carbon emission budget to keep global warming below 1.5 °C.},
	language = {en},
	number = {8},
	urldate = {2020-08-31},
	journal = {Nature Geoscience},
	author = {Keuper, Frida and Wild, Birgit and Kummu, Matti and Beer, Christian and Blume-Werry, Gesche and Fontaine, Sébastien and Gavazov, Konstantin and Gentsch, Norman and Guggenberger, Georg and Hugelius, Gustaf and Jalava, Mika and Koven, Charles and Krab, Eveline J. and Kuhry, Peter and Monteux, Sylvain and Richter, Andreas and Shahzad, Tanvir and Weedon, James T. and Dorrepaal, Ellen},
	month = aug,
	year = {2020},
	note = {Number: 8
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {560--565},
}

As global temperatures continue to rise, a key uncertainty of climate projections is the microbial decomposition of vast organic carbon stocks in thawing permafrost soils. Decomposition rates can accelerate up to fourfold in the presence of plant roots, and this mechanism—termed the rhizosphere priming effect—may be especially relevant to thawing permafrost soils as rising temperatures also stimulate plant productivity in the Arctic. However, priming is currently not explicitly included in any model projections of future carbon losses from the permafrost area. Here, we combine high-resolution spatial and depth-resolved datasets of key plant and permafrost properties with empirical relationships of priming effects from living plants on microbial respiration. We show that rhizosphere priming amplifies overall soil respiration in permafrost-affected ecosystems by ~12%, which translates to a priming-induced absolute loss of ~40 Pg soil carbon from the northern permafrost area by 2100. Our findings highlight the need to include fine-scale ecological interactions in order to accurately predict large-scale greenhouse gas emissions, and suggest even tighter restrictions on the estimated 200 Pg anthropogenic carbon emission budget to keep global warming below 1.5 °C.

@article{jansen_drivers_2020,
	title = {Drivers of diffusive {CH4} emissions from shallow subarctic lakes on daily to multi-year timescales},
	volume = {17},
	issn = {1726-4189},
	url = {https://www.biogeosciences.net/17/1911/2020/},
	doi = {10.5194/bg-17-1911-2020},
	language = {en},
	number = {7},
	urldate = {2020-04-23},
	journal = {Biogeosciences},
	author = {Jansen, Joachim and Thornton, Brett F. and Cortés, Alicia and Snöälv, Jo and Wik, Martin and MacIntyre, Sally and Crill, Patrick M.},
	month = apr,
	year = {2020},
	keywords = {\#nosource},
	pages = {1911--1932},
}

@article{berggren_systematic_2020,
	title = {Systematic microbial production of optically active dissolved organic matter in subarctic lake water},
	volume = {65},
	copyright = {© 2019 Association for the Sciences of Limnology and Oceanography},
	issn = {1939-5590},
	url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lno.11362},
	doi = {10.1002/lno.11362},
	abstract = {The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20\% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22\% and 30\%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.},
	language = {en},
	number = {5},
	urldate = {2020-08-31},
	journal = {Limnology and Oceanography},
	author = {Berggren, Martin and Gudasz, Cristian and Guillemette, Francois and Hensgens, Geert and Ye, Linlin and Karlsson, Jan},
	year = {2020},
	note = {\_eprint: https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11362},
	keywords = {\#nosource},
	pages = {951--961},
}

The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22% and 30%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.

@article{zhao_autumn_2020,
	title = {Autumn migration direction of juvenile willow warblers ({Phylloscopus} t. trochilus and {P}. t. acredula) and their hybrids assessed by {qPCR} {SNP} genotyping},
	volume = {8},
	issn = {2051-3933},
	url = {https://doi.org/10.1186/s40462-020-00209-7},
	doi = {10.1186/s40462-020-00209-7},
	abstract = {Geographic regions, where two closely related taxa with different migration routes come into contact, are known as migratory divides. Hybrids originating from migratory divides are hypothesized to migrate intermediately relative to the parental populations. Few studies have tested this hypothesis in wild birds, and only in hybrids that have completed the migration back to the breeding grounds. Here, we make use of the well-established migration routes of willow warblers (Phylloscopus trochilus), for which the subspecies trochilus and acredula have migration-associated genetic markers on chromosomes 1 and 5. The genetic approach enabled us to analyze the geographic distribution of juveniles during their first autumn migration, predicting that hybrids should be more frequent in the central flyway over Italy than along the typical SW routes of trochilus and SE routes of acredula.},
	number = {1},
	urldate = {2020-06-08},
	journal = {Movement Ecology},
	author = {Zhao, Tianhao and Ilieva, Mihaela and Larson, Keith and Lundberg, Max and Neto, Júlio M. and Sokolovskis, Kristaps and Åkesson, Susanne and Bensch, Staffan},
	month = may,
	year = {2020},
	keywords = {\#nosource},
	pages = {22},
}

Geographic regions, where two closely related taxa with different migration routes come into contact, are known as migratory divides. Hybrids originating from migratory divides are hypothesized to migrate intermediately relative to the parental populations. Few studies have tested this hypothesis in wild birds, and only in hybrids that have completed the migration back to the breeding grounds. Here, we make use of the well-established migration routes of willow warblers (Phylloscopus trochilus), for which the subspecies trochilus and acredula have migration-associated genetic markers on chromosomes 1 and 5. The genetic approach enabled us to analyze the geographic distribution of juveniles during their first autumn migration, predicting that hybrids should be more frequent in the central flyway over Italy than along the typical SW routes of trochilus and SE routes of acredula.

@article{hugelius_large_2020,
	title = {Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw},
	volume = {117},
	copyright = {Copyright © 2020 the Author(s). Published by PNAS.. https://creativecommons.org/licenses/by/4.0/This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).},
	issn = {0027-8424, 1091-6490},
	url = {https://www.pnas.org/content/117/34/20438},
	doi = {10.1073/pnas.1916387117},
	abstract = {Northern peatlands have accumulated large stocks of organic carbon (C) and nitrogen (N), but their spatial distribution and vulnerability to climate warming remain uncertain. Here, we used machine-learning techniques with extensive peat core data (n {\textgreater} 7,000) to create observation-based maps of northern peatland C and N stocks, and to assess their response to warming and permafrost thaw. We estimate that northern peatlands cover 3.7 ± 0.5 million km2 and store 415 ± 150 Pg C and 10 ± 7 Pg N. Nearly half of the peatland area and peat C stocks are permafrost affected. Using modeled global warming stabilization scenarios (from 1.5 to 6 °C warming), we project that the current sink of atmospheric C (0.10 ± 0.02 Pg C⋅y−1) in northern peatlands will shift to a C source as 0.8 to 1.9 million km2 of permafrost-affected peatlands thaw. The projected thaw would cause peatland greenhouse gas emissions equal to ∼1\% of anthropogenic radiative forcing in this century. The main forcing is from methane emissions (0.7 to 3 Pg cumulative CH4-C) with smaller carbon dioxide forcing (1 to 2 Pg CO2-C) and minor nitrous oxide losses. We project that initial CO2-C losses reverse after ∼200 y, as warming strengthens peatland C-sinks. We project substantial, but highly uncertain, additional losses of peat into fluvial systems of 10 to 30 Pg C and 0.4 to 0.9 Pg N. The combined gaseous and fluvial peatland C loss estimated here adds 30 to 50\% onto previous estimates of permafrost-thaw C losses, with southern permafrost regions being the most vulnerable.},
	language = {en},
	number = {34},
	urldate = {2020-10-08},
	journal = {Proceedings of the National Academy of Sciences},
	author = {Hugelius, Gustaf and Loisel, Julie and Chadburn, Sarah and Jackson, Robert B. and Jones, Miriam and MacDonald, Glen and Marushchak, Maija and Olefeldt, David and Packalen, Maara and Siewert, Matthias B. and Treat, Claire and Turetsky, Merritt and Voigt, Carolina and Yu, Zicheng},
	month = aug,
	year = {2020},
	pmid = {32778585},
	note = {Publisher: National Academy of Sciences
Section: Physical Sciences},
	keywords = {\#nosource, carbon stocks, greenhouse gas fluxes, nitrogen stocks, northern peatlands, permafrost thaw},
	pages = {20438--20446},
}

Northern peatlands have accumulated large stocks of organic carbon (C) and nitrogen (N), but their spatial distribution and vulnerability to climate warming remain uncertain. Here, we used machine-learning techniques with extensive peat core data (n \textgreater 7,000) to create observation-based maps of northern peatland C and N stocks, and to assess their response to warming and permafrost thaw. We estimate that northern peatlands cover 3.7 ± 0.5 million km2 and store 415 ± 150 Pg C and 10 ± 7 Pg N. Nearly half of the peatland area and peat C stocks are permafrost affected. Using modeled global warming stabilization scenarios (from 1.5 to 6 °C warming), we project that the current sink of atmospheric C (0.10 ± 0.02 Pg C⋅y−1) in northern peatlands will shift to a C source as 0.8 to 1.9 million km2 of permafrost-affected peatlands thaw. The projected thaw would cause peatland greenhouse gas emissions equal to ∼1% of anthropogenic radiative forcing in this century. The main forcing is from methane emissions (0.7 to 3 Pg cumulative CH4-C) with smaller carbon dioxide forcing (1 to 2 Pg CO2-C) and minor nitrous oxide losses. We project that initial CO2-C losses reverse after ∼200 y, as warming strengthens peatland C-sinks. We project substantial, but highly uncertain, additional losses of peat into fluvial systems of 10 to 30 Pg C and 0.4 to 0.9 Pg N. The combined gaseous and fluvial peatland C loss estimated here adds 30 to 50% onto previous estimates of permafrost-thaw C losses, with southern permafrost regions being the most vulnerable.

@article{einarsdottir_particles_2020,
	title = {Particles and aeration at mire-stream interfaces cause selective removal and modification of dissolved organic matter},
	volume = {n/a},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {2169-8961},
	url = {http://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JG005654},
	doi = {10.1029/2020jg005654},
	abstract = {Peatlands are dominant sources of dissolved organic matter (DOM) to boreal inland waters and play important roles in the aquatic carbon cycle. Yet, before peat-derived DOM enters aquatic networks, it needs to pass through peat-stream interfaces that are often characterized by transitions from anoxic or hypoxic to oxic conditions. Aeration at these interfaces may trigger processes that impact the DOM pool, and its fate downstream. Here, we experimentally assessed how the aeration of iron- and organic-rich mire-waters influences biodegradation, particle-formation, and modification of DOM. In addition, we investigated how suspended peat-derived particles from mires may influence these processes. We found that within five days of aeration, 20\% of the DOM transformed into particulate organic matter (POM). This removal was likely due to combination of mechanisms including co-precipitation with oxidized iron, aggregation, and DOM-adsorption onto peat-derived particles. Peat-derived particles promoted microbial activity, but biodegradation was a minor loss mechanism of DOM removal. Interestingly, microbial respiration accounted for only half of the oxygen loss, suggesting substantial non-respiratory oxygen consumption. The differences observed in DOM characteristics between anoxic and aerated treatments suggest that hydrophilic, aromatic DOM co-precipitated with iron oxides in aerated samples, and the corresponding C:N analysis of generated POM revealed that these organic species were nitrogen-poor. Meanwhile, POM formed via adsorption onto peat-derived particles generated from non-aromatic DOM and more nitrogen-rich species. Hence, selective removal of DOM, dissolved iron, and thus oxygen may be important and overlooked processes in mire-dominated headwater systems.},
	language = {en},
	number = {n/a},
	urldate = {2020-11-20},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Einarsdóttir, Karólína and Attermeyer, Katrin and Hawkes, Jeffrey A. and Kothawala, Dolly and Sponseller, Ryan A. and Tranvik, Lars J.},
	year = {2020},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020JG005654},
	keywords = {\#nosource, CN, Co-precipitation, DOM, Iron, POM, Particle adsorption},
	pages = {e2020JG005654},
}

Peatlands are dominant sources of dissolved organic matter (DOM) to boreal inland waters and play important roles in the aquatic carbon cycle. Yet, before peat-derived DOM enters aquatic networks, it needs to pass through peat-stream interfaces that are often characterized by transitions from anoxic or hypoxic to oxic conditions. Aeration at these interfaces may trigger processes that impact the DOM pool, and its fate downstream. Here, we experimentally assessed how the aeration of iron- and organic-rich mire-waters influences biodegradation, particle-formation, and modification of DOM. In addition, we investigated how suspended peat-derived particles from mires may influence these processes. We found that within five days of aeration, 20% of the DOM transformed into particulate organic matter (POM). This removal was likely due to combination of mechanisms including co-precipitation with oxidized iron, aggregation, and DOM-adsorption onto peat-derived particles. Peat-derived particles promoted microbial activity, but biodegradation was a minor loss mechanism of DOM removal. Interestingly, microbial respiration accounted for only half of the oxygen loss, suggesting substantial non-respiratory oxygen consumption. The differences observed in DOM characteristics between anoxic and aerated treatments suggest that hydrophilic, aromatic DOM co-precipitated with iron oxides in aerated samples, and the corresponding C:N analysis of generated POM revealed that these organic species were nitrogen-poor. Meanwhile, POM formed via adsorption onto peat-derived particles generated from non-aromatic DOM and more nitrogen-rich species. Hence, selective removal of DOM, dissolved iron, and thus oxygen may be important and overlooked processes in mire-dominated headwater systems.

@article{harms_emission_2020,
	title = {Emission of {Greenhouse} {Gases} {From} {Water} {Tracks} {Draining} {Arctic} {Hillslopes}},
	volume = {125},
	copyright = {©2020. American Geophysical Union. All Rights Reserved.},
	issn = {2169-8961},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JG005889},
	doi = {10.1029/2020jg005889},
	abstract = {Experimental and ambient warming of Arctic tundra results in emissions of greenhouse gases to the atmosphere, contributing to a positive feedback to climate warming. Estimates of gas emissions from lakes and terrestrial tundra confirm the significance of aquatic fluxes in greenhouse gas budgets, whereas few estimates describe emissions from fluvial networks. We measured dissolved gas concentrations and estimated emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water tracks, vegetated depressions that hydrologically connect hillslope soils to lakes and streams. Concentrations of trace gases generally increased as ground thaw deepened through the growing season, indicating active production of greenhouse gases in thawed soils. Wet antecedent conditions were correlated with a decline in CO2 and CH4 concentrations. Dissolved N2O in excess of atmospheric equilibrium occurred in drier water tracks, but on average water tracks took up N2O from the atmosphere at low rates. Estimated CO2 emission rates for water tracks were among the highest observed for Arctic aquatic ecosystems, whereas CH4 emissions were of similar magnitude to streams. Despite occupying less than 1\% of total catchment area, surface waters within water tracks were an estimated source of up to 53–85\% of total CH4 emissions from their catchments and offset the terrestrial C sink by 5–9\% during the growing season. Water tracks are abundant features of tundra landscapes that contain warmer soils and incur deeper thaw than adjacent terrestrial ecosystems and as such might contribute to ongoing and accelerating release of greenhouse gases from permafrost soils to the atmosphere.},
	language = {en},
	number = {12},
	urldate = {2021-01-18},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Harms, Tamara K. and Rocher‐Ros, Gerard and Godsey, Sarah E.},
	year = {2020},
	note = {\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JG005889},
	keywords = {\#nosource, carbon dioxide (CO2), dissolved gases, flow paths, methane (CH4), nitrous oxide (N2O), tundra},
	pages = {e2020JG005889},
}

Experimental and ambient warming of Arctic tundra results in emissions of greenhouse gases to the atmosphere, contributing to a positive feedback to climate warming. Estimates of gas emissions from lakes and terrestrial tundra confirm the significance of aquatic fluxes in greenhouse gas budgets, whereas few estimates describe emissions from fluvial networks. We measured dissolved gas concentrations and estimated emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water tracks, vegetated depressions that hydrologically connect hillslope soils to lakes and streams. Concentrations of trace gases generally increased as ground thaw deepened through the growing season, indicating active production of greenhouse gases in thawed soils. Wet antecedent conditions were correlated with a decline in CO2 and CH4 concentrations. Dissolved N2O in excess of atmospheric equilibrium occurred in drier water tracks, but on average water tracks took up N2O from the atmosphere at low rates. Estimated CO2 emission rates for water tracks were among the highest observed for Arctic aquatic ecosystems, whereas CH4 emissions were of similar magnitude to streams. Despite occupying less than 1% of total catchment area, surface waters within water tracks were an estimated source of up to 53–85% of total CH4 emissions from their catchments and offset the terrestrial C sink by 5–9% during the growing season. Water tracks are abundant features of tundra landscapes that contain warmer soils and incur deeper thaw than adjacent terrestrial ecosystems and as such might contribute to ongoing and accelerating release of greenhouse gases from permafrost soils to the atmosphere.

@incollection{muehlbauer_variables_2020,
	address = {Cham},
	title = {Variables {Affecting} {Resource} {Subsidies} from {Streams} and {Rivers} to {Land} and their {Susceptibility} to {Global} {Change} {Stressors}},
	isbn = {978-3-030-49480-3},
	url = {https://doi.org/10.1007/978-3-030-49480-3_7},
	abstract = {Stream and river ecosystems provide subsidies of emergent adult aquatic insects and other resources to terrestrial food webs, and this lotic–land subsidy has garnered much attention in recent research. Here, we critically examine a list of biotic and abiotic variables—including productivity, dominant taxa, geomorphology, and weather—that should be important in affecting the nature of these subsidy dynamics between lotic and terrestrial ecosystems, especially the pathway from emergent aquatic insects to terrestrial predators. We also explore how interactions between these variables can lead to otherwise unexpected patterns in the importance of aquatic subsidies to terrestrial food webs. Utilizing a match-mismatch framework developed previously, we identify how these variables and interactions may be affected by a broad suite of stressors in addition to contaminants: climate change, land-use conversion, damming and water abstraction, and species invasions and extinctions. These stressors may all act to modify and potentially exacerbate the effects of contaminants on subsidies. The available literature on many variables is sparse, despite strong theoretical underpinnings supporting their importance for lotic–land subsidies. Notably, these understudied variables include those related to physical geomorphology and the structure of the stream/river and floodplain/riparian zone as well as species-specific interactions between aquatic and terrestrial organisms. We suggest that more explicit characterization of these variables and more research directly linking broad-scale stressors to subsidy resource–consumer interactions can help provide a more mechanistic understanding to lotic–land subsidy dynamics within a changing environment.},
	language = {en},
	urldate = {2020-11-20},
	booktitle = {Contaminants and {Ecological} {Subsidies}: {The} {Land}-{Water} {Interface}},
	publisher = {Springer International Publishing},
	author = {Muehlbauer, Jeffrey D. and Larsen, Stefano and Jonsson, Micael and Emilson, Erik J. S.},
	editor = {Kraus, Johanna M. and Walters, David M. and Mills, Marc A.},
	year = {2020},
	doi = {10.1007/978-3-030-49480-3_7},
	keywords = {\#nosource, Climate change, Dams, Freshwater subsidies, Invasive species, Land use, Stressors},
	pages = {129--155},
}

Stream and river ecosystems provide subsidies of emergent adult aquatic insects and other resources to terrestrial food webs, and this lotic–land subsidy has garnered much attention in recent research. Here, we critically examine a list of biotic and abiotic variables—including productivity, dominant taxa, geomorphology, and weather—that should be important in affecting the nature of these subsidy dynamics between lotic and terrestrial ecosystems, especially the pathway from emergent aquatic insects to terrestrial predators. We also explore how interactions between these variables can lead to otherwise unexpected patterns in the importance of aquatic subsidies to terrestrial food webs. Utilizing a match-mismatch framework developed previously, we identify how these variables and interactions may be affected by a broad suite of stressors in addition to contaminants: climate change, land-use conversion, damming and water abstraction, and species invasions and extinctions. These stressors may all act to modify and potentially exacerbate the effects of contaminants on subsidies. The available literature on many variables is sparse, despite strong theoretical underpinnings supporting their importance for lotic–land subsidies. Notably, these understudied variables include those related to physical geomorphology and the structure of the stream/river and floodplain/riparian zone as well as species-specific interactions between aquatic and terrestrial organisms. We suggest that more explicit characterization of these variables and more research directly linking broad-scale stressors to subsidy resource–consumer interactions can help provide a more mechanistic understanding to lotic–land subsidy dynamics within a changing environment.

@article{monteux_carbon_2020,
	title = {Carbon and nitrogen cycling in {Yedoma} permafrost controlled by microbial functional limitations},
	volume = {13},
	copyright = {2020 The Author(s), under exclusive licence to Springer Nature Limited},
	issn = {1752-0908},
	url = {http://www.nature.com/articles/s41561-020-00662-4},
	doi = {10.1038/s41561-020-00662-4},
	abstract = {Warming-induced microbial decomposition of organic matter in permafrost soils constitutes a climate-change feedback of uncertain magnitude. While physicochemical constraints on soil functioning are relatively well understood, the constraints attributable to microbial community composition remain unclear. Here we show that biogeochemical processes in permafrost can be impaired by missing functions in the microbial community—functional limitations—probably due to environmental filtering of the microbial community over millennia-long freezing. We inoculated Yedoma permafrost with a functionally diverse exogenous microbial community to test this mechanism by introducing potentially missing microbial functions. This initiated nitrification activity and increased CO2 production by 38\% over 161 days. The changes in soil functioning were strongly associated with an altered microbial community composition, rather than with changes in soil chemistry or microbial biomass. The present permafrost microbial community composition thus constrains carbon and nitrogen biogeochemical processes, but microbial colonization, likely to occur upon permafrost thaw in situ, can alleviate such functional limitations. Accounting for functional limitations and their alleviation could strongly increase our estimate of the vulnerability of permafrost soil organic matter to decomposition and the resulting global climate feedback.},
	language = {en},
	number = {12},
	urldate = {2021-01-18},
	journal = {Nature Geoscience},
	author = {Monteux, Sylvain and Keuper, Frida and Fontaine, Sébastien and Gavazov, Konstantin and Hallin, Sara and Juhanson, Jaanis and Krab, Eveline J. and Revaillot, Sandrine and Verbruggen, Erik and Walz, Josefine and Weedon, James T. and Dorrepaal, Ellen},
	month = dec,
	year = {2020},
	note = {Number: 12
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {794--798},
}

Warming-induced microbial decomposition of organic matter in permafrost soils constitutes a climate-change feedback of uncertain magnitude. While physicochemical constraints on soil functioning are relatively well understood, the constraints attributable to microbial community composition remain unclear. Here we show that biogeochemical processes in permafrost can be impaired by missing functions in the microbial community—functional limitations—probably due to environmental filtering of the microbial community over millennia-long freezing. We inoculated Yedoma permafrost with a functionally diverse exogenous microbial community to test this mechanism by introducing potentially missing microbial functions. This initiated nitrification activity and increased CO2 production by 38% over 161 days. The changes in soil functioning were strongly associated with an altered microbial community composition, rather than with changes in soil chemistry or microbial biomass. The present permafrost microbial community composition thus constrains carbon and nitrogen biogeochemical processes, but microbial colonization, likely to occur upon permafrost thaw in situ, can alleviate such functional limitations. Accounting for functional limitations and their alleviation could strongly increase our estimate of the vulnerability of permafrost soil organic matter to decomposition and the resulting global climate feedback.

@article{macintyre_turbulence_2020,
	title = {Turbulence in a small boreal lake: {Consequences} for air–water gas exchange},
	volume = {n/a},
	issn = {1939-5590},
	shorttitle = {Turbulence in a small boreal lake},
	url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lno.11645},
	doi = {10.1002/lno.11645},
	abstract = {The hydrodynamics within small boreal lakes have rarely been studied, yet knowing whether turbulence at the air–water interface and in the water column scales with metrics developed elsewhere is essential for computing metabolism and fluxes of climate-forcing trace gases. We instrumented a humic, 4.7 ha, boreal lake with two meteorological stations, three thermistor arrays, an infrared (IR) camera to quantify surface divergence, obtained turbulence as dissipation rate of turbulent kinetic energy (ε) using an acoustic Doppler velocimeter and a temperature-gradient microstructure profiler, and conducted chamber measurements for short periods to obtain fluxes and gas transfer velocities (k). Near-surface ε varied from 10−8 to 10−6 m2 s−3 for the 0–4 m s−1 winds and followed predictions from Monin–Obukhov similarity theory. The coefficient of eddy diffusivity in the mixed layer was up to 10−3 m2 s−1 on the windiest afternoons, an order of magnitude less other afternoons, and near molecular at deeper depths. The upper thermocline upwelled when Lake numbers (LN) dropped below four facilitating vertical and horizontal exchange. k computed from a surface renewal model using ε agreed with values from chambers and surface divergence and increased linearly with wind speed. Diurnal thermoclines formed on sunny days when winds were {\textless} 3 m s−1, a condition that can lead to elevated near-surface ε and k. Results extend scaling approaches developed in the laboratory and for larger water bodies, illustrate turbulence and k are greater than expected in small wind-sheltered lakes, and provide new equations to quantify fluxes.},
	language = {en},
	number = {n/a},
	urldate = {2021-01-18},
	journal = {Limnology and Oceanography},
	author = {MacIntyre, Sally and Bastviken, David and Arneborg, Lars and Crowe, Adam T. and Karlsson, Jan and Andersson, Andreas and Gålfalk, Magnus and Rutgersson, Anna and Podgrajsek, Eva and Melack, John M.},
	year = {2020},
	note = {\_eprint: https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11645},
	keywords = {\#nosource},
	pages = {20},
}

The hydrodynamics within small boreal lakes have rarely been studied, yet knowing whether turbulence at the air–water interface and in the water column scales with metrics developed elsewhere is essential for computing metabolism and fluxes of climate-forcing trace gases. We instrumented a humic, 4.7 ha, boreal lake with two meteorological stations, three thermistor arrays, an infrared (IR) camera to quantify surface divergence, obtained turbulence as dissipation rate of turbulent kinetic energy (ε) using an acoustic Doppler velocimeter and a temperature-gradient microstructure profiler, and conducted chamber measurements for short periods to obtain fluxes and gas transfer velocities (k). Near-surface ε varied from 10−8 to 10−6 m2 s−3 for the 0–4 m s−1 winds and followed predictions from Monin–Obukhov similarity theory. The coefficient of eddy diffusivity in the mixed layer was up to 10−3 m2 s−1 on the windiest afternoons, an order of magnitude less other afternoons, and near molecular at deeper depths. The upper thermocline upwelled when Lake numbers (LN) dropped below four facilitating vertical and horizontal exchange. k computed from a surface renewal model using ε agreed with values from chambers and surface divergence and increased linearly with wind speed. Diurnal thermoclines formed on sunny days when winds were \textless 3 m s−1, a condition that can lead to elevated near-surface ε and k. Results extend scaling approaches developed in the laboratory and for larger water bodies, illustrate turbulence and k are greater than expected in small wind-sheltered lakes, and provide new equations to quantify fluxes.

@article{ramberg_structure_2020,
	title = {The {Structure} of {Riparian} {Vegetation} in {Agricultural} {Landscapes} {Influences} {Spider} {Communities} and {Aquatic}-{Terrestrial} {Linkages}},
	volume = {12},
	copyright = {http://creativecommons.org/licenses/by/3.0/},
	url = {https://www.mdpi.com/2073-4441/12/10/2855},
	doi = {10.3390/w12102855},
	abstract = {Riparian habitats are important ecotones connecting aquatic and terrestrial ecosystems, but are often highly degraded by human activities. Riparian buffers might help support impacted riparian communities, and improve trophic connectivity. We sampled spider communities from riparian habitats in an agricultural catchment, and analyzed their polyunsaturated fatty acid (PUFA) content to quantify trophic connectivity. Specific PUFAs are exclusively produced by stream algae, and thus are used to track uptake of aquatic resources by terrestrial consumers. Riparian spiders were collected from 10 site pairs situated along agricultural streams, and from five forest sites (25 sites total). Each agricultural site pair comprised an unshaded site with predominantly herbaceous vegetation cover, and a second with a woody riparian buffer. Spider communities differed between site types, with web-building spiders dominating woody buffered sites and free-living spiders associated with more open habitats. PUFA concentrations were greatest overall in free-living spiders, but there was also evidence for increased PUFA uptake by some spider groups when a woody riparian buffer was present. Our results reveal the different roles of open and wooded riparian habitats in supporting terrestrial consumers and aquatic-terrestrial connectivity, and highlight the value of incorporating patches of woody vegetation within riparian networks in highly modified landscapes.},
	language = {en},
	number = {10},
	urldate = {2020-11-20},
	journal = {Water},
	author = {Ramberg, Ellinor and Burdon, Francis J. and Sargac, Jasmina and Kupilas, Benjamin and Rîşnoveanu, Geta and Lau, Danny C. P. and Johnson, Richard K. and McKie, Brendan G.},
	month = oct,
	year = {2020},
	note = {Number: 10
Publisher: Multidisciplinary Digital Publishing Institute},
	keywords = {\#nosource, agriculture, ecotone, polyunsaturated fatty acids, riparian buffer, spiders, trophic connectivity},
	pages = {2855},
}

Riparian habitats are important ecotones connecting aquatic and terrestrial ecosystems, but are often highly degraded by human activities. Riparian buffers might help support impacted riparian communities, and improve trophic connectivity. We sampled spider communities from riparian habitats in an agricultural catchment, and analyzed their polyunsaturated fatty acid (PUFA) content to quantify trophic connectivity. Specific PUFAs are exclusively produced by stream algae, and thus are used to track uptake of aquatic resources by terrestrial consumers. Riparian spiders were collected from 10 site pairs situated along agricultural streams, and from five forest sites (25 sites total). Each agricultural site pair comprised an unshaded site with predominantly herbaceous vegetation cover, and a second with a woody riparian buffer. Spider communities differed between site types, with web-building spiders dominating woody buffered sites and free-living spiders associated with more open habitats. PUFA concentrations were greatest overall in free-living spiders, but there was also evidence for increased PUFA uptake by some spider groups when a woody riparian buffer was present. Our results reveal the different roles of open and wooded riparian habitats in supporting terrestrial consumers and aquatic-terrestrial connectivity, and highlight the value of incorporating patches of woody vegetation within riparian networks in highly modified landscapes.

@phdthesis{myrstener_role_2020,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {The role of nutrients for stream ecosystem function in {Arctic} landscapes : drivers of productivity under environmental change},
	shorttitle = {The role of nutrients for stream ecosystem function in {Arctic} landscapes},
	url = {http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-177439},
	abstract = {Arctic and sub-Arctic freshwaters are currently experiencing substantial ecosystem changes due to the effects of global warming. Global warming effects on these freshwaters include increasing water ...},
	language = {eng},
	urldate = {2021-01-18},
	school = {Umeå University},
	author = {Myrstener, Maria},
	collaborator = {Sponseller, Ryan A. and Giesler, Reiner and Bergström, Ann-Kristin},
	year = {2020},
	note = {Publisher: Umeå universitet},
	keywords = {\#nosource},
}

Arctic and sub-Arctic freshwaters are currently experiencing substantial ecosystem changes due to the effects of global warming. Global warming effects on these freshwaters include increasing water ...

@article{al-kharusi_large-scale_2020,
	title = {Large-scale retrieval of coloured dissolved organic matter in northern lakes using {Sentinel}-2 data},
	volume = {12},
	issn = {2072-4292},
	url = {https://www.mdpi.com/2072-4292/12/1/157},
	doi = {10.3390/rs12010157},
	abstract = {Owing to the significant societal value of inland water resources, there is a need for cost-effective monitoring of water quality on large scales. We tested the suitability of the recently launched Sentinel-2A to monitor a key water quality parameter, coloured dissolved organic matter (CDOM), in various types of lakes in northern Sweden. Values of a(420)CDOM (CDOM absorption at 420 nm wavelength) were obtained by analyzing water samples from 46 lakes in five districts across Sweden within an area of approximately 800 km2. We evaluated the relationships between a(420)CDOM and band ratios derived from Sentinel-2A Level-1C and Level-2A products. The band ratios B2/B3 (460 nm/560 nm) and B3/B5 (560 nm/705 nm) showed poor relationships with a(420)CDOM in Level-1C and 2A data both before and after the removal of outliers. However, there was a slightly stronger power relationship between the atmospherically-corrected B3/B4 ratio and a(420)CDOM (R2 = 0.28, n = 46), and this relationship was further improved (R2 = 0.65, n = 41) by removing observations affected by light haze and cirrus clouds. This study covered a wide range of lakes in different landscape settings and demonstrates the broad applicability of a(420)CDOM retrieval algorithms based on the B3/B4 ratio derived from Sentinel-2A.},
	language = {en},
	number = {1},
	urldate = {2020-03-19},
	journal = {Remote Sensing},
	author = {Al-Kharusi, Enass Said. and Tenenbaum, David E. and Abdi, Abdulhakim M. and Kutser, Tiit and Karlsson, Jan and Bergström, Ann-Kristin and Berggren, Martin},
	month = jan,
	year = {2020},
	keywords = {\#nosource},
	pages = {157},
}

Owing to the significant societal value of inland water resources, there is a need for cost-effective monitoring of water quality on large scales. We tested the suitability of the recently launched Sentinel-2A to monitor a key water quality parameter, coloured dissolved organic matter (CDOM), in various types of lakes in northern Sweden. Values of a(420)CDOM (CDOM absorption at 420 nm wavelength) were obtained by analyzing water samples from 46 lakes in five districts across Sweden within an area of approximately 800 km2. We evaluated the relationships between a(420)CDOM and band ratios derived from Sentinel-2A Level-1C and Level-2A products. The band ratios B2/B3 (460 nm/560 nm) and B3/B5 (560 nm/705 nm) showed poor relationships with a(420)CDOM in Level-1C and 2A data both before and after the removal of outliers. However, there was a slightly stronger power relationship between the atmospherically-corrected B3/B4 ratio and a(420)CDOM (R2 = 0.28, n = 46), and this relationship was further improved (R2 = 0.65, n = 41) by removing observations affected by light haze and cirrus clouds. This study covered a wide range of lakes in different landscape settings and demonstrates the broad applicability of a(420)CDOM retrieval algorithms based on the B3/B4 ratio derived from Sentinel-2A.

@article{beer_protection_2020,
	title = {Protection of permafrost soils from thawing by increasing herbivore density},
	volume = {10},
	copyright = {2020 The Author(s)},
	issn = {2045-2322},
	url = {https://www.nature.com/articles/s41598-020-60938-y},
	doi = {10.1038/s41598-020-60938-y},
	abstract = {Climate change will cause a substantial future greenhouse gas release from warming and thawing permafrost-affected soils to the atmosphere enabling a positive feedback mechanism. Increasing the population density of big herbivores in northern high-latitude ecosystems will increase snow density and hence decrease the insulation strength of snow during winter. As a consequence, theoretically 80\% of current permafrost-affected soils ({\textless}10 m) is projected to remain until 2100 even when assuming a strong warming using the Representative Concentration Pathway 8.5. Importantly, permafrost temperature is estimated to remain below −4 °C on average after increasing herbivore population density. Such ecosystem management practices would be therefore theoretically an important additional climate change mitigation strategy. Our results also highlight the importance of new field experiments and observations, and the integration of fauna dynamics into complex Earth System models, in order to reliably project future ecosystem functions and climate.},
	language = {en},
	number = {1},
	urldate = {2020-04-23},
	journal = {Scientific Reports},
	author = {Beer, Christian and Zimov, Nikita and Olofsson, Johan and Porada, Philipp and Zimov, Sergey},
	month = mar,
	year = {2020},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {1--10},
}

Climate change will cause a substantial future greenhouse gas release from warming and thawing permafrost-affected soils to the atmosphere enabling a positive feedback mechanism. Increasing the population density of big herbivores in northern high-latitude ecosystems will increase snow density and hence decrease the insulation strength of snow during winter. As a consequence, theoretically 80% of current permafrost-affected soils (\textless10 m) is projected to remain until 2100 even when assuming a strong warming using the Representative Concentration Pathway 8.5. Importantly, permafrost temperature is estimated to remain below −4 °C on average after increasing herbivore population density. Such ecosystem management practices would be therefore theoretically an important additional climate change mitigation strategy. Our results also highlight the importance of new field experiments and observations, and the integration of fauna dynamics into complex Earth System models, in order to reliably project future ecosystem functions and climate.

@article{knoll_consequences_2019,
	title = {Consequences of lake and river ice loss on cultural ecosystem services},
	volume = {4},
	copyright = {© 2019 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10116},
	doi = {10.1002/lol2.10116},
	abstract = {People extensively use lakes and rivers covered by seasonal ice. Although ice cover duration has been declining over the past 150 years for Northern Hemisphere freshwaters, we know relatively little about how ice loss directly affects humans. Here, we synthesize the cultural ecosystem services (i.e., services that provide intangible or nonmaterial benefits) and associated benefits supported by inland ice. We also provide, for the first time, empirical examples that give quantitative evidence for a winter warming effect on a wide range of ice-related cultural ecosystem services and benefits. We show that in recent decades, warmer air temperatures delayed the opening date of winter ice roads and led to cancellations of spiritual ceremonies, outdoor ice skating races, and ice fishing tournaments. Additionally, our synthesis effort suggests unexploited data sets that allow for the use of integrative approaches to evaluate the interplay between inland ice loss and society.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography Letters},
	author = {Knoll, Lesley B. and Sharma, Sapna and Denfeld, Blaize A. and Flaim, Giovanna and Hori, Yukari and Magnuson, John J. and Straile, Dietmar and Weyhenmeyer, Gesa A.},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lol2.10116},
	keywords = {\#nosource},
	pages = {119--131},
}

People extensively use lakes and rivers covered by seasonal ice. Although ice cover duration has been declining over the past 150 years for Northern Hemisphere freshwaters, we know relatively little about how ice loss directly affects humans. Here, we synthesize the cultural ecosystem services (i.e., services that provide intangible or nonmaterial benefits) and associated benefits supported by inland ice. We also provide, for the first time, empirical examples that give quantitative evidence for a winter warming effect on a wide range of ice-related cultural ecosystem services and benefits. We show that in recent decades, warmer air temperatures delayed the opening date of winter ice roads and led to cancellations of spiritual ceremonies, outdoor ice skating races, and ice fishing tournaments. Additionally, our synthesis effort suggests unexploited data sets that allow for the use of integrative approaches to evaluate the interplay between inland ice loss and society.

@article{zeh_plant_2019,
	title = {Plant functional types and temperature control carbon input via roots in peatland soils},
	volume = {438},
	issn = {1573-5036},
	url = {https://doi.org/10.1007/s11104-019-03958-6},
	doi = {10.1007/s11104-019-03958-6},
	abstract = {Northern peatlands store large amounts of soil organic carbon (C) that can be very sensitive to ongoing global warming. Recently it has been shown that temperature-enhanced growth of vascular plants in these typically moss-dominated ecosystems may promote microbial peat decomposition by increased C input via root exudates. To what extent different plant functional types (PFT) and soil temperature interact in controlling root C input is still unclear. In this study we explored how root C input is related to the presence of ericoid shrubs (shrubs) and graminoid sedges (sedges) by means of a factorial plant clipping experiment (= PFT effect) in two peatlands located at different altitude (= temperature effect).},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Plant and Soil},
	author = {Zeh, Lilli and Limpens, Juul and Erhagen, Björn and Bragazza, Luca and Kalbitz, Karsten},
	month = may,
	year = {2019},
	keywords = {\#nosource, Dissolved organic carbon, Peatland, Root carbon input, Sedges, Shrubs, Soil respiration, Vascular plants, δ 13C},
	pages = {19--38},
}

Northern peatlands store large amounts of soil organic carbon (C) that can be very sensitive to ongoing global warming. Recently it has been shown that temperature-enhanced growth of vascular plants in these typically moss-dominated ecosystems may promote microbial peat decomposition by increased C input via root exudates. To what extent different plant functional types (PFT) and soil temperature interact in controlling root C input is still unclear. In this study we explored how root C input is related to the presence of ericoid shrubs (shrubs) and graminoid sedges (sedges) by means of a factorial plant clipping experiment (= PFT effect) in two peatlands located at different altitude (= temperature effect).

@article{vasconcelos_bottom-up_2019,
	title = {Bottom-up and top-down effects of browning and warming on shallow lake food webs},
	volume = {25},
	copyright = {© 2018 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14521},
	doi = {10.1111/gcb.14521},
	abstract = {Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom-up and top-down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process-based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient-poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (a) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (b) Because of active habitat choice, fish exert top-down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (c) Warming relaxes top-down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient-rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type.},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {Global Change Biology},
	author = {Vasconcelos, Francisco Rivera and Diehl, Sebastian and Rodríguez, Patricia and Hedström, Per and Karlsson, Jan and Byström, Pär},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14521},
	keywords = {\#nosource, benthic and pelagic habitats, bottom-up and top-down control, browning, food webs, light and nutrients, shallow lake, top predator, warming},
	pages = {504--521},
}

Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom-up and top-down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process-based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient-poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (a) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (b) Because of active habitat choice, fish exert top-down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (c) Warming relaxes top-down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient-rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type.

@article{vachon_influence_2019,
	title = {Influence of water column stratification and mixing patterns on the fate of methane produced in deep sediments of a small eutrophic lake},
	volume = {64},
	copyright = {© 2019 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11172},
	doi = {10.1002/lno.11172},
	abstract = {Methane (CH4), a potent greenhouse gas, is produced in and emitted from lakes at globally significant rates. The drivers controlling the proportion of produced CH4 that will reach the atmosphere, however, are still not well understood. We sampled a small eutrophic lake (Soppensee, Switzerland) in 2016–2017 for CH4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH4 produced in hypolimnetic sediments. Using a mass balance approach for the periods between April and October of both years, net CH4 production rates in hypolimnetic sediments ranged between 11.4 and 17.7 mmol m−2 d−1, of which 66–88\% was stored in the hypolimnion, 13–27\% was diffused to the epilimnion, and 6–7\% left the sediments via ebullition. Combining these results with a process-based model we show that water column turbulent diffusivity (K z) had a major influence on the fate of produced CH4 in the sediments, where higher K z values potentially lead to greater proportion being oxidized and lower K z lead to a greater proportion being stored. During fall when the water column mixes, we found that a greater proportion of stored CH4 is emitted if the lake mixes rapidly, whereas a greater proportion will be oxidized if the water column mixes more gradually. This work highlights the central role of lake hydrodynamics in regulating CH4 dynamics and further suggests the potential for CH4 production and emissions to be sensitive to climate-driven alterations in lake mixing regimes and stratification.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography},
	author = {Vachon, Dominic and Langenegger, Timon and Donis, Daphne and McGinnis, Daniel F.},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11172},
	keywords = {\#nosource},
	pages = {2114--2128},
}

Methane (CH4), a potent greenhouse gas, is produced in and emitted from lakes at globally significant rates. The drivers controlling the proportion of produced CH4 that will reach the atmosphere, however, are still not well understood. We sampled a small eutrophic lake (Soppensee, Switzerland) in 2016–2017 for CH4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH4 produced in hypolimnetic sediments. Using a mass balance approach for the periods between April and October of both years, net CH4 production rates in hypolimnetic sediments ranged between 11.4 and 17.7 mmol m−2 d−1, of which 66–88% was stored in the hypolimnion, 13–27% was diffused to the epilimnion, and 6–7% left the sediments via ebullition. Combining these results with a process-based model we show that water column turbulent diffusivity (K z) had a major influence on the fate of produced CH4 in the sediments, where higher K z values potentially lead to greater proportion being oxidized and lower K z lead to a greater proportion being stored. During fall when the water column mixes, we found that a greater proportion of stored CH4 is emitted if the lake mixes rapidly, whereas a greater proportion will be oxidized if the water column mixes more gradually. This work highlights the central role of lake hydrodynamics in regulating CH4 dynamics and further suggests the potential for CH4 production and emissions to be sensitive to climate-driven alterations in lake mixing regimes and stratification.

@article{tuomi_herbivore_2019,
	title = {Herbivore {Effects} on {Ecosystem} {Process} {Rates} in a {Low}-{Productive} {System}},
	volume = {22},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-018-0307-4},
	doi = {10.1007/s10021-018-0307-4},
	abstract = {Mammalian herbivores shape the structure and function of many nutrient-limited or low-productive terrestrial ecosystems through modification of plant communities and plant–soil feedbacks. In the tundra biome, mammalian herbivores may both accelerate and decelerate plant biomass growth, microbial activity and nutrient cycling, that is, ecosystem process rates. Selective foraging and associated declines of palatable species are known to be major drivers of plant–soil feedbacks. However, declines in dominant plants of low palatability often linked with high herbivore densities may also modify ecosystem process rates, yet have received little attention. We present data from an island experiment with a 10-year vole density manipulation, to test the hypothesis that herbivores accelerate process rates by decreasing the relative abundance of poorly palatable plants to palatable ones. We measured plant species abundances and community composition, nitrogen contents of green plant tissues and multiple soil and litter variables under high and low vole density. Corroborating our hypothesis, periodic high vole density increased ecosystem process rates in low-productive tundra. High vole density was associated with both increasing relative abundance of palatable forbs over unpalatable evergreen dwarf shrubs and higher plant N content both at species and at community level. Changes in plant community composition, in turn, explained variation in microbial activity in litter and soil inorganic nutrient availability. We propose a new conceptual model with two distinct vole–plant–soil feedback pathways. Voles may drive local plant–soil feedbacks that either increase or decrease ecosystem process rates, in turn promoting heterogeneity in vegetation and soils across tundra landscapes.},
	language = {en},
	number = {4},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Tuomi, Maria and Stark, Sari and Hoset, Katrine S. and Väisänen, Maria and Oksanen, Lauri and Murguzur, Francisco J. A. and Tuomisto, Hanna and Dahlgren, Jonas and Bråthen, Kari Anne},
	month = jun,
	year = {2019},
	keywords = {\#nosource, NIRS, Northern Fennoscandia, dwarf shrub tundra, microbial activity, microtine rodent, plant community traits, plant–soil interactions, soil N and P},
	pages = {827--843},
}

Mammalian herbivores shape the structure and function of many nutrient-limited or low-productive terrestrial ecosystems through modification of plant communities and plant–soil feedbacks. In the tundra biome, mammalian herbivores may both accelerate and decelerate plant biomass growth, microbial activity and nutrient cycling, that is, ecosystem process rates. Selective foraging and associated declines of palatable species are known to be major drivers of plant–soil feedbacks. However, declines in dominant plants of low palatability often linked with high herbivore densities may also modify ecosystem process rates, yet have received little attention. We present data from an island experiment with a 10-year vole density manipulation, to test the hypothesis that herbivores accelerate process rates by decreasing the relative abundance of poorly palatable plants to palatable ones. We measured plant species abundances and community composition, nitrogen contents of green plant tissues and multiple soil and litter variables under high and low vole density. Corroborating our hypothesis, periodic high vole density increased ecosystem process rates in low-productive tundra. High vole density was associated with both increasing relative abundance of palatable forbs over unpalatable evergreen dwarf shrubs and higher plant N content both at species and at community level. Changes in plant community composition, in turn, explained variation in microbial activity in litter and soil inorganic nutrient availability. We propose a new conceptual model with two distinct vole–plant–soil feedback pathways. Voles may drive local plant–soil feedbacks that either increase or decrease ecosystem process rates, in turn promoting heterogeneity in vegetation and soils across tundra landscapes.

@article{sitters_long-term_2019,
	title = {Long-term heavy reindeer grazing promotes plant phosphorus limitation in arctic tundra},
	volume = {33},
	copyright = {© 2019 The Authors. Functional Ecology © 2019 British Ecological Society},
	issn = {1365-2435},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13342},
	doi = {10.1111/1365-2435.13342},
	abstract = {The potential of large mammalian herbivores to shift plant communities between nitrogen (N) and phosphorus (P) limitation has received little attention so far. However, herbivores can influence the cycling of these growth-limiting nutrients, and thereby affect plant nutrient limitation and productivity. Tundra ecosystems are nutrient-poor and commonly grazed by large herbivores like reindeer and may thus be responsive to such changes. Here, we examined the effect of long-term light and heavy reindeer grazing on nutrient limitation of plant growth in a Scandinavian arctic tundra. We are the first to conduct a factorial N and P fertilization experiment across the two grazing regimes in two functionally contrasting vegetation types: heath and meadow. Annual primary productivity (APP) showed contrasting responses to our fertilization treatments under light and heavy grazing. Under light grazing, APP increased in response to N + P additions in both the heath and meadow. Under heavy grazing, APP increased in response to N in the heath, with an additional positive effect of N + P combined, while APP increased in response to P and N + P additions in the meadow. These results clearly show that an increase in the grazing intensity of reindeer facilitated a shift towards more P-limited conditions in Scandinavian arctic tundra, by increasing N cycling without having a corresponding positive effect on P cycling. In the N-poor heath, reindeer increased soil N availability at least partly due to a shift towards more N-rich graminoids, while in the meadow, reindeer decreased soil P availability. The mechanisms behind this decrease remain unclear, but reindeer may simply export more P from the system than N due to their large P demand for the production of their antlers. Synthesis. We conclude that heavy and long-term reindeer grazing promoted a more P-limited tundra, thus experimentally confirming the potential of large mammalian herbivores to influence nutrient limitation of plant growth. A plain language summary is available for this article.},
	language = {en},
	number = {7},
	urldate = {2024-03-27},
	journal = {Functional Ecology},
	author = {Sitters, Judith and Cherif, Mehdi and Egelkraut, Dagmar and Giesler, Reiner and Olofsson, Johan},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.13342},
	keywords = {\#nosource, Fertilization experiment, fertilization experiment, herbivory, nitrogen, nutrient limitation, plant-herbivore interactions, plant–herbivore interactions, primary productivity, stoichiometry},
	pages = {1233--1242},
}

The potential of large mammalian herbivores to shift plant communities between nitrogen (N) and phosphorus (P) limitation has received little attention so far. However, herbivores can influence the cycling of these growth-limiting nutrients, and thereby affect plant nutrient limitation and productivity. Tundra ecosystems are nutrient-poor and commonly grazed by large herbivores like reindeer and may thus be responsive to such changes. Here, we examined the effect of long-term light and heavy reindeer grazing on nutrient limitation of plant growth in a Scandinavian arctic tundra. We are the first to conduct a factorial N and P fertilization experiment across the two grazing regimes in two functionally contrasting vegetation types: heath and meadow. Annual primary productivity (APP) showed contrasting responses to our fertilization treatments under light and heavy grazing. Under light grazing, APP increased in response to N + P additions in both the heath and meadow. Under heavy grazing, APP increased in response to N in the heath, with an additional positive effect of N + P combined, while APP increased in response to P and N + P additions in the meadow. These results clearly show that an increase in the grazing intensity of reindeer facilitated a shift towards more P-limited conditions in Scandinavian arctic tundra, by increasing N cycling without having a corresponding positive effect on P cycling. In the N-poor heath, reindeer increased soil N availability at least partly due to a shift towards more N-rich graminoids, while in the meadow, reindeer decreased soil P availability. The mechanisms behind this decrease remain unclear, but reindeer may simply export more P from the system than N due to their large P demand for the production of their antlers. Synthesis. We conclude that heavy and long-term reindeer grazing promoted a more P-limited tundra, thus experimentally confirming the potential of large mammalian herbivores to influence nutrient limitation of plant growth. A plain language summary is available for this article.

@article{sarneel_local_2019,
	title = {Local flooding history affects plant recruitment in riparian zones},
	volume = {30},
	copyright = {© 2019 The Authors. Journal of Vegetation Science published by John Wiley \& Sons Ltd on behalf of Internation Association of Vegetation Science.},
	issn = {1654-1103},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.12731},
	doi = {10.1111/jvs.12731},
	abstract = {Aims Many rivers across the globe are severely impacted by changed flooding regimes, resulting in drastic shifts in vegetation, but the processes driving the exchange of flood-sensitive and flood-tolerant species are understood less. We studied the role of long-term and recent flooding histories for riparian plant recruitment in response to various changes in flooding regime. Location Vindel River catchment (Northern Sweden). Methods We experimentally changed long-term flooding regimes by transplanting turfs between high and low elevations in 2000 and in 2014 (n = 8 per treatment). We sowed seeds of five riparian species in both transplanted turfs and non-transplanted controls and counted seedling numbers over two growing seasons. Further, we inventoried natural seedling frequencies in 190 plots in 19 reaches in 2013 and 2014, and related natural seedling numbers to plot flooding history in the period 2012–2014. Results We observed effects of long-term flooding history in the second year of the transplantation study (2015), but not in the first year. In 2015, turfs transplanted to locations with less flooding resulted in higher plant recruitment while transplantation to sites with more frequent flooding reduced recruitment compared to the controls. Since these differences were only found in recently transplanted turfs and not in older turfs, the legacy effect of long-term flooding history can be transient. In the field seedling survey, similar differences were found between flooding-history categories in 2013, but not in 2014, when the moisture conditions of the most recent year determined flooding. Further, lowest seedling numbers were observed when the previous flooding occurred in winter, and higher seedling numbers when floods occurred in spring or not at all. Conclusions Both long-term and recent flooding histories can affect plant recruitment, and their influence should be taken into account when designing restoration projects.},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {Journal of Vegetation Science},
	author = {Sarneel, Judith M. and Bejarano, Maria Dolores and van Oosterhout, Martin and Nilsson, Christer},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvs.12731},
	keywords = {\#nosource, dispersal filtering, environmental filtering, flood dynamics, historic contingency, legacy effects, plant recruitment window, regime shifts, window of opportunity, zonation},
	pages = {224--234},
}

Aims Many rivers across the globe are severely impacted by changed flooding regimes, resulting in drastic shifts in vegetation, but the processes driving the exchange of flood-sensitive and flood-tolerant species are understood less. We studied the role of long-term and recent flooding histories for riparian plant recruitment in response to various changes in flooding regime. Location Vindel River catchment (Northern Sweden). Methods We experimentally changed long-term flooding regimes by transplanting turfs between high and low elevations in 2000 and in 2014 (n = 8 per treatment). We sowed seeds of five riparian species in both transplanted turfs and non-transplanted controls and counted seedling numbers over two growing seasons. Further, we inventoried natural seedling frequencies in 190 plots in 19 reaches in 2013 and 2014, and related natural seedling numbers to plot flooding history in the period 2012–2014. Results We observed effects of long-term flooding history in the second year of the transplantation study (2015), but not in the first year. In 2015, turfs transplanted to locations with less flooding resulted in higher plant recruitment while transplantation to sites with more frequent flooding reduced recruitment compared to the controls. Since these differences were only found in recently transplanted turfs and not in older turfs, the legacy effect of long-term flooding history can be transient. In the field seedling survey, similar differences were found between flooding-history categories in 2013, but not in 2014, when the moisture conditions of the most recent year determined flooding. Further, lowest seedling numbers were observed when the previous flooding occurred in winter, and higher seedling numbers when floods occurred in spring or not at all. Conclusions Both long-term and recent flooding histories can affect plant recruitment, and their influence should be taken into account when designing restoration projects.

@article{maier_interannual_2019,
	title = {Interannual variation in seasonal diatom sedimentation reveals the importance of late winter processes and their timing for sediment signal formation},
	volume = {64},
	copyright = {© 2019 Association for the Sciences of Limnology and Oceanography},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11106},
	doi = {10.1002/lno.11106},
	abstract = {Disentangling the process information contained in a diatom sediment signature is crucial for reliable future predictions based on paleolimnological records. In this study, we combine limnological and paleolimnological monitoring to address the fundamental question: Which environmental information is contained in a diatom sediment signal? We compared annual diatom sequential sediment trap records with the diatom record of the annually varved lake sediment of Nylandssjön (northern Sweden) from three meteorologically different years (2012–2014). The seasonal patterns in diatom sedimentation were strikingly different in varve years 2012 and 2014 compared to varve year 2013. In 2012 and 2014, up to 70\% of the annual flux occurred in a single spring month and was dominated by Cyclotella glomerata. In contrast, in 2013, peak fluxes were much lower and more annually integrated. Next, we compared the full-year diatom trap results with year round in-lake physical, chemical, and biological monitored parameters, as well as meteorological variables. Annual averages of environmental conditions did not explain the interannual variability in diatom sedimentation. Instead, the seasonality of diatom sedimentation was determined by the timing of the spring diatom bloom relative to lake over-turn in winters with warm vs. cold air temperature. With our combined limnological and paleolimnological monitoring approach, we find that an annual diatom signal can either contain primarily seasonal climate information from a short time period or be annually integrated. We synthesize our results in a novel conceptual model, which describes the response of sediment diatom signals to two distinct sequences of late-winter conditions.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Maier, Dominique Béatrice and Diehl, Sebastian and Bigler, Christian},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11106},
	keywords = {\#nosource},
	pages = {1186--1199},
}

Disentangling the process information contained in a diatom sediment signature is crucial for reliable future predictions based on paleolimnological records. In this study, we combine limnological and paleolimnological monitoring to address the fundamental question: Which environmental information is contained in a diatom sediment signal? We compared annual diatom sequential sediment trap records with the diatom record of the annually varved lake sediment of Nylandssjön (northern Sweden) from three meteorologically different years (2012–2014). The seasonal patterns in diatom sedimentation were strikingly different in varve years 2012 and 2014 compared to varve year 2013. In 2012 and 2014, up to 70% of the annual flux occurred in a single spring month and was dominated by Cyclotella glomerata. In contrast, in 2013, peak fluxes were much lower and more annually integrated. Next, we compared the full-year diatom trap results with year round in-lake physical, chemical, and biological monitored parameters, as well as meteorological variables. Annual averages of environmental conditions did not explain the interannual variability in diatom sedimentation. Instead, the seasonality of diatom sedimentation was determined by the timing of the spring diatom bloom relative to lake over-turn in winters with warm vs. cold air temperature. With our combined limnological and paleolimnological monitoring approach, we find that an annual diatom signal can either contain primarily seasonal climate information from a short time period or be annually integrated. We synthesize our results in a novel conceptual model, which describes the response of sediment diatom signals to two distinct sequences of late-winter conditions.

@article{lupon_groundwater_2019,
	title = {Groundwater inflows control patterns and sources of greenhouse gas emissions from streams},
	volume = {64},
	copyright = {© 2019 Association for the Sciences of Limnology and Oceanography},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11134},
	doi = {10.1002/lno.11134},
	abstract = {Headwater streams can be important sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO2, and CH4 concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH4 and CO2 concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. DOC mineralization and CH4 oxidation within the stream accounted for 17–51\% of stream CO2 emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.},
	language = {en},
	number = {4},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography},
	author = {Lupon, Anna and Denfeld, Blaize A. and Laudon, Hjalmar and Leach, Jason and Karlsson, Jan and Sponseller, Ryan A.},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11134},
	keywords = {\#nosource},
	pages = {1545--1557},
}

Headwater streams can be important sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO2, and CH4 concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH4 and CO2 concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. DOC mineralization and CH4 oxidation within the stream accounted for 17–51% of stream CO2 emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.

@article{klaus_evaluations_2019,
	title = {Evaluations of {Climate} and {Land} {Management} {Effects} on {Lake} {Carbon} {Cycling} {Need} to {Account} for {Temporal} {Variability} in {CO2} {Concentrations}},
	volume = {33},
	copyright = {©2019. American Geophysical Union. All Rights Reserved.},
	issn = {1944-9224},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GB005979},
	doi = {10.1029/2018GB005979},
	abstract = {Carbon dioxide (CO2) concentrations in lakes vary strongly over time. This variability is rarely captured by environmental monitoring but is crucial for accurately assessing the magnitude of lake CO2 emissions. However, it is unknown to what extent temporal variability needs to be captured to understand important drivers of lake carbon cycling such as climate and land management. We used environmental monitoring data of Swedish forest lakes collected in autumn (n = 439) and throughout the whole open water season (n = 22) from a wet and a dry year to assess temporal variability in effects of climate and forestry on CO2 concentrations across lakes. Effects differed depending on the season and year sampled. According to cross-lake comparisons based on autumn data, CO2 concentrations increased with annual mean air temperature (dry year) or catchment forest productivity (wet year) but were not related to colored dissolved organic matter concentrations. In contrast, open water-season averaged CO2 concentrations were similar across temperature and productivity gradients but increased with colored dissolved organic matter. These contradictions resulted from scale mismatches in input data, lead to weak explanatory power (R2 = 9–32\%), and were consistent across published data from 79 temperate, boreal, and arctic lakes. In a global survey of 144 published studies, we identified a trade-off between temporal and spatial coverage of CO2 sampling. This trade-off clearly determines which conclusions are drawn from landscape-scale CO2 assessments. Accurate evaluations of the effects of climate and land management require spatially and temporally representative data that can be provided by emerging sensor technologies and forms of collaborative sampling.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Global Biogeochemical Cycles},
	author = {Klaus, Marcus and Seekell, David A. and Lidberg, William and Karlsson, Jan},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005979},
	keywords = {\#nosource, carbon cycling, greenhouse gas, lake, sampling, seasonality, structural equation modeling},
	pages = {243--265},
}

Carbon dioxide (CO2) concentrations in lakes vary strongly over time. This variability is rarely captured by environmental monitoring but is crucial for accurately assessing the magnitude of lake CO2 emissions. However, it is unknown to what extent temporal variability needs to be captured to understand important drivers of lake carbon cycling such as climate and land management. We used environmental monitoring data of Swedish forest lakes collected in autumn (n = 439) and throughout the whole open water season (n = 22) from a wet and a dry year to assess temporal variability in effects of climate and forestry on CO2 concentrations across lakes. Effects differed depending on the season and year sampled. According to cross-lake comparisons based on autumn data, CO2 concentrations increased with annual mean air temperature (dry year) or catchment forest productivity (wet year) but were not related to colored dissolved organic matter concentrations. In contrast, open water-season averaged CO2 concentrations were similar across temperature and productivity gradients but increased with colored dissolved organic matter. These contradictions resulted from scale mismatches in input data, lead to weak explanatory power (R2 = 9–32%), and were consistent across published data from 79 temperate, boreal, and arctic lakes. In a global survey of 144 published studies, we identified a trade-off between temporal and spatial coverage of CO2 sampling. This trade-off clearly determines which conclusions are drawn from landscape-scale CO2 assessments. Accurate evaluations of the effects of climate and land management require spatially and temporally representative data that can be provided by emerging sensor technologies and forms of collaborative sampling.

@article{klaus_listening_2019,
	title = {Listening to air–water gas exchange in running waters},
	volume = {17},
	copyright = {© 2019 Association for the Sciences of Limnology and Oceanography},
	issn = {1541-5856},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lom3.10321},
	doi = {10.1002/lom3.10321},
	abstract = {Air–water gas exchange velocities (k) are critical components of many biogeochemical and ecological process studies in aquatic systems. However, their high spatiotemporal variability is difficult to capture with traditional methods, especially in turbulent flow. Here, we investigate the potential of sound spectral analysis to infer k in running waters, based on the rationale that both turbulence and entrained bubbles drive gas exchange and cause a characteristic sound. We explored the relationship between k and sound spectral properties using laboratory experiments and field observations under a wide range of turbulence and bubble conditions. We estimated k using flux chamber measurements of CO2 exchange and recorded sound above and below the water surface by microphones and hydrophones, respectively. We found a strong influence of turbulence and bubbles on sound pressure levels (SPLs) at octave bands of 31.5 Hz and 1000 Hz, respectively. The difference in SPLs at these bands and background noise bands showed a linear correlation with k both in the laboratory (R2 = 0.93–0.99) and in the field (median R2 = 0.42–0.90). Underwater sound indices outperformed aerial sound indices in general, and indices based on hydraulic parameters in particular, in turbulent and bubbly surface flow. The results highlight the unique potential of acoustic techniques to predict k, isolate mechanisms, and improve the spatiotemporal coverage of k estimates in bubbly flow.},
	language = {en},
	number = {7},
	urldate = {2024-03-26},
	journal = {Limnology and Oceanography: Methods},
	author = {Klaus, Marcus and Geibrink, Erik and Hotchkiss, Erin R. and Karlsson, Jan},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lom3.10321},
	keywords = {\#nosource},
	pages = {395--414},
}

Air–water gas exchange velocities (k) are critical components of many biogeochemical and ecological process studies in aquatic systems. However, their high spatiotemporal variability is difficult to capture with traditional methods, especially in turbulent flow. Here, we investigate the potential of sound spectral analysis to infer k in running waters, based on the rationale that both turbulence and entrained bubbles drive gas exchange and cause a characteristic sound. We explored the relationship between k and sound spectral properties using laboratory experiments and field observations under a wide range of turbulence and bubble conditions. We estimated k using flux chamber measurements of CO2 exchange and recorded sound above and below the water surface by microphones and hydrophones, respectively. We found a strong influence of turbulence and bubbles on sound pressure levels (SPLs) at octave bands of 31.5 Hz and 1000 Hz, respectively. The difference in SPLs at these bands and background noise bands showed a linear correlation with k both in the laboratory (R2 = 0.93–0.99) and in the field (median R2 = 0.42–0.90). Underwater sound indices outperformed aerial sound indices in general, and indices based on hydraulic parameters in particular, in turbulent and bubbly surface flow. The results highlight the unique potential of acoustic techniques to predict k, isolate mechanisms, and improve the spatiotemporal coverage of k estimates in bubbly flow.

@article{dodorico_food_2019,
	title = {Food {Inequality}, {Injustice}, and {Rights}},
	volume = {69},
	issn = {0006-3568},
	url = {https://doi.org/10.1093/biosci/biz002},
	doi = {10.1093/biosci/biz002},
	abstract = {As humanity continues to grow in size, questions related to human rights and the existing unequal distribution of food resources have taken on greater urgency. Is inequality in food access unjust or a regrettable consequence of the geographic distribution of biophysical resources? To what extent are there obligations to redress inequalities in access to food? We draw from a human rights perspective to identify obligations associated with access to food and develop a quantitative framework to evaluate the fulfillment of the human right to food. We discuss the capacity of socioeconomic development to reduce inequalities in per capita food availability with respect to the distribution of biophysical resources among countries. Although, at the country level, international trade shows the capacity to reduce human rights deficits by increasing food availability in countries with limited food production, whether it actually improves the fulfillment of the right to food will depend on within-country inequality.},
	number = {3},
	urldate = {2024-03-26},
	journal = {BioScience},
	author = {D’Odorico, Paolo and Carr, Joel A and Davis, Kyle F and Dell’Angelo, Jampel and Seekell, David A},
	month = mar,
	year = {2019},
	keywords = {\#nosource},
	pages = {180--190},
}

As humanity continues to grow in size, questions related to human rights and the existing unequal distribution of food resources have taken on greater urgency. Is inequality in food access unjust or a regrettable consequence of the geographic distribution of biophysical resources? To what extent are there obligations to redress inequalities in access to food? We draw from a human rights perspective to identify obligations associated with access to food and develop a quantitative framework to evaluate the fulfillment of the human right to food. We discuss the capacity of socioeconomic development to reduce inequalities in per capita food availability with respect to the distribution of biophysical resources among countries. Although, at the country level, international trade shows the capacity to reduce human rights deficits by increasing food availability in countries with limited food production, whether it actually improves the fulfillment of the right to food will depend on within-country inequality.

@article{capo_how_2019,
	title = {How does environmental inter-annual variability shape aquatic microbial communities? {A} 40-year annual record of sedimentary {DNA} from a boreal lake ({Nylandssj}\&\#246;n, {Sweden})},
	volume = {7},
	issn = {2296-701X},
	shorttitle = {How does environmental inter-annual variability shape aquatic microbial communities?},
	url = {https://www.frontiersin.org/articles/10.3389/fevo.2019.00245/abstract},
	doi = {10.3389/fevo.2019.00245},
	abstract = {To assess the sensitivity of lakes to anthropogenically-driven environmental changes (e.g., nutrient supply, climate change), it is necessary to first isolate the effects of between-year variability in weather conditions. This variability can strongly impact a lake’s biological community especially in boreal and arctic areas where snow phenology play an important role in controlling the input of terrestrial matter to the lake. Identifying the importance of this inherent variability is difficult without time series that span at least several decades. Here, we applied a molecular approach (metabarcoding on eukaryotic 18S rRNA genes and qPCR on cyanobacterial 16S rRNA genes) to sedimentary DNA (sed-DNA) to unravel the annual variability of microbial community in 40 years’ sediment record from the boreal lake Nylandssjön which preserve annually-laminated sediments. Our comparison between seasonal meteorological data, sediment inorganic geochemistry (X-ray fluorescence analyses) and organic biomarkers (pyrolysis-gas chromatography/mass spectrometry analyses), demonstrated that inter-annual variability strongly influence the sediment composition in Nylandssjön. Spring temperature, snow and ice phenology (e.g. the percentage of snow loss in spring, the timing of lake ice-off) were identified as important drivers for the inputs of terrestrial material to the lake, and were therefore also important for shaping the aquatic biological community. Main changes were detected in the late-80s/mid-90s and mid-2000s associated with increases in algal productivity (see from organic biomarkers), in total richness of the protistan community and in relative abundances of Chlorophyta, Dinophyceae as well as Cyanobacteria abundance. These changes could be linked to a decline in terrestrial inputs to the lake during the snow melt and run-off period, which in turn was driven by warmer winter temperatures. Even if our data shows that meteorological factors do affect the sediment composition, they only explain part of the variability. This is most likely a consequence of the high inter-annual variability in abiotic and biotic parameters highlighting the difficulty to draw firm conclusions concerning drivers of biological changes at an annual or sub-annual resolution even with the 40-year varved sediment record from Nylandssjön. Hence, it is necessary to have an even longer time perspective in order to reveal the full implications of climate change.},
	language = {English},
	urldate = {2019-06-24},
	journal = {Frontiers in Ecology and Evolution},
	author = {Capo, Eric and Rydberg, Johan and Tolu, Julie and Domaizon, Isabelle and Debroas, Didier and Bindler, Richard and Bigler, Christian},
	year = {2019},
	keywords = {\#nosource, Inorganic geochemistry, Meteorological data, Varved sediment record, metabarcoding, organic proxies, paleolimnology, sedimentary DNA},
	pages = {00245},
}

To assess the sensitivity of lakes to anthropogenically-driven environmental changes (e.g., nutrient supply, climate change), it is necessary to first isolate the effects of between-year variability in weather conditions. This variability can strongly impact a lake’s biological community especially in boreal and arctic areas where snow phenology play an important role in controlling the input of terrestrial matter to the lake. Identifying the importance of this inherent variability is difficult without time series that span at least several decades. Here, we applied a molecular approach (metabarcoding on eukaryotic 18S rRNA genes and qPCR on cyanobacterial 16S rRNA genes) to sedimentary DNA (sed-DNA) to unravel the annual variability of microbial community in 40 years’ sediment record from the boreal lake Nylandssjön which preserve annually-laminated sediments. Our comparison between seasonal meteorological data, sediment inorganic geochemistry (X-ray fluorescence analyses) and organic biomarkers (pyrolysis-gas chromatography/mass spectrometry analyses), demonstrated that inter-annual variability strongly influence the sediment composition in Nylandssjön. Spring temperature, snow and ice phenology (e.g. the percentage of snow loss in spring, the timing of lake ice-off) were identified as important drivers for the inputs of terrestrial material to the lake, and were therefore also important for shaping the aquatic biological community. Main changes were detected in the late-80s/mid-90s and mid-2000s associated with increases in algal productivity (see from organic biomarkers), in total richness of the protistan community and in relative abundances of Chlorophyta, Dinophyceae as well as Cyanobacteria abundance. These changes could be linked to a decline in terrestrial inputs to the lake during the snow melt and run-off period, which in turn was driven by warmer winter temperatures. Even if our data shows that meteorological factors do affect the sediment composition, they only explain part of the variability. This is most likely a consequence of the high inter-annual variability in abiotic and biotic parameters highlighting the difficulty to draw firm conclusions concerning drivers of biological changes at an annual or sub-annual resolution even with the 40-year varved sediment record from Nylandssjön. Hence, it is necessary to have an even longer time perspective in order to reveal the full implications of climate change.

@article{bergstrom_light_2019,
	title = {Light and nutrient control phytoplankton biomass responses to global change in northern lakes},
	volume = {25},
	copyright = {© 2019 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14623},
	doi = {10.1111/gcb.14623},
	abstract = {Global change affects terrestrial loadings of colored dissolved organic carbon (DOC) and nutrients to northern lakes. Still, little is known about how phytoplankton respond to changes in light and nutrient availability across gradients in lake DOC. In this study, we used results from whole-lake studies in northern Sweden to show that annual mean phytoplankton biomass expressed unimodal curved relationships across lake DOC gradients, peaking at threshold DOC levels of around 11 mg/L. Whole-lake single nutrient enrichment in selected lakes caused elevated biomass, with most pronounced effect at the threshold DOC level. These patterns give support to the suggested dual control by DOC on phytoplankton via nutrient (positively) and light (negatively) availability and imply that the lakes' location along the DOC axis is critical in determining to what extent phytoplankton respond to changes in DOC and/or nutrient loadings. By using data from the large Swedish Lake Monitoring Survey, we further estimated that 80\% of northern Swedish lakes are below the DOC threshold, potentially experiencing increased phytoplankton biomass with browning alone, and/or combined with nutrient enrichment. The results support the previous model results on effects of browning and eutrophication on lake phytoplankton, and provide important understanding of how northern lakes may respond to future global changes.},
	language = {en},
	number = {6},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Bergström, Ann-Kristin and Karlsson, Jan},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14623},
	keywords = {\#nosource, Dissolved organic carbon, Nitrogen, Phosphorus, Phytoplankton, Whole-lake nutrient enrichment experiments, dissolved organic carbon, nitrogen, phosphorus, phytoplankton, whole-lake nutrient enrichment experiments},
	pages = {2021--2029},
}

Global change affects terrestrial loadings of colored dissolved organic carbon (DOC) and nutrients to northern lakes. Still, little is known about how phytoplankton respond to changes in light and nutrient availability across gradients in lake DOC. In this study, we used results from whole-lake studies in northern Sweden to show that annual mean phytoplankton biomass expressed unimodal curved relationships across lake DOC gradients, peaking at threshold DOC levels of around 11 mg/L. Whole-lake single nutrient enrichment in selected lakes caused elevated biomass, with most pronounced effect at the threshold DOC level. These patterns give support to the suggested dual control by DOC on phytoplankton via nutrient (positively) and light (negatively) availability and imply that the lakes' location along the DOC axis is critical in determining to what extent phytoplankton respond to changes in DOC and/or nutrient loadings. By using data from the large Swedish Lake Monitoring Survey, we further estimated that 80% of northern Swedish lakes are below the DOC threshold, potentially experiencing increased phytoplankton biomass with browning alone, and/or combined with nutrient enrichment. The results support the previous model results on effects of browning and eutrophication on lake phytoplankton, and provide important understanding of how northern lakes may respond to future global changes.

@article{barthelemy_defoliation_2019,
	title = {Defoliation of a grass is mediated by the positive effect of dung deposition, moss removal and enhanced soil nutrient contents: results from a reindeer grazing simulation experiment},
	volume = {128},
	copyright = {© 2019 The Authors. Oikos © 2019 Nordic Society Oikos},
	issn = {1600-0706},
	shorttitle = {Defoliation of a grass is mediated by the positive effect of dung deposition, moss removal and enhanced soil nutrient contents},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/oik.06310},
	doi = {10.1111/oik.06310},
	abstract = {Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.},
	language = {en},
	number = {10},
	urldate = {2024-03-26},
	journal = {Oikos},
	author = {Barthelemy, Hélène and Dorrepaal, Ellen and Olofsson, Johan},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/oik.06310},
	keywords = {\#nosource, Arctic tundra, Festuca ovina, plant compensatory growth, plant nitrogen content, reindeer grazing, soil legacy},
	pages = {1515--1524},
}

Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.

@article{schwieger_patterns_2019,
	title = {Patterns and drivers in spring and autumn phenology differ above- and belowground in four ecosystems under the same macroclimatic conditions},
	volume = {445},
	url = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-187824},
	doi = {10.1007/s11104-019-04300-w},
	abstract = {Background and aims: Start and end of the growing season determine important ecosystem processes, but their drivers may differ above-and belowground, between autumn and spring, and between ecosyste ...},
	language = {eng},
	number = {1-2},
	urldate = {2024-03-26},
	journal = {Plant and Soil},
	author = {Schwieger, Sarah and Blume-Werry, Gesche and Peters, Bo and Smiljanic, Marko and Kreyling, Juergen},
	year = {2019},
	note = {Publisher: Springer},
	pages = {217--229},
}

Background and aims: Start and end of the growing season determine important ecosystem processes, but their drivers may differ above-and belowground, between autumn and spring, and between ecosyste ...

@phdthesis{rocher-ros_biophysical_2019,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {Biophysical controls on {CO2} evasion from {Arctic} inland waters},
	url = {http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-158882},
	abstract = {DiVA portal is a finding tool for research publications and student theses written at the following 49 universities and research institutions.},
	language = {eng},
	urldate = {2020-03-19},
	school = {Umeå University},
	author = {Rocher-Ros, Gerard},
	collaborator = {Giesler, Reiner and Sponseller, Ryan A. and Bergström, Ann-Kristin},
	year = {2019},
	note = {Publisher: Umeå University},
	keywords = {\#nosource},
}

DiVA portal is a finding tool for research publications and student theses written at the following 49 universities and research institutions.

@article{vaisanen_legacy_2019,
	title = {The {Legacy} {Effects} of {Winter} {Climate} on {Microbial} {Functioning} {After} {Snowmelt} in a {Subarctic} {Tundra}},
	volume = {77},
	issn = {1432-184X},
	url = {https://doi.org/10.1007/s00248-018-1213-1},
	doi = {10.1007/s00248-018-1213-1},
	abstract = {Warming-induced increases in microbial CO2 release in northern tundra may positively feedback to climate change. However, shifts in microbial extracellular enzyme activities (EEAs) may alter the impacts of warming over the longer term. We investigated the in situ effects of 3 years of winter warming in combination with the in vitro effects of a rapid warming (6 days) on microbial CO2 release and EEAs in a subarctic tundra heath after snowmelt in spring. Winter warming did not change microbial CO2 release at ambient (10 °C) or at rapidly increased temperatures, i.e., a warm spell (18 °C) but induced changes (P {\textless} 0.1) in the Q10 of microbial respiration and an oxidative EEA. Thus, although warmer winters may induce legacy effects in microbial temperature acclimation, we found no evidence for changes in potential carbon mineralization after spring thaw.},
	number = {1},
	journal = {Microbial Ecology},
	author = {Väisänen, Maria and Gavazov, Konstantin and Krab, Eveline J. and Dorrepaal, Ellen},
	month = jan,
	year = {2019},
	keywords = {\#nosource},
	pages = {186--190},
}

Warming-induced increases in microbial CO2 release in northern tundra may positively feedback to climate change. However, shifts in microbial extracellular enzyme activities (EEAs) may alter the impacts of warming over the longer term. We investigated the in situ effects of 3 years of winter warming in combination with the in vitro effects of a rapid warming (6 days) on microbial CO2 release and EEAs in a subarctic tundra heath after snowmelt in spring. Winter warming did not change microbial CO2 release at ambient (10 °C) or at rapidly increased temperatures, i.e., a warm spell (18 °C) but induced changes (P \textless 0.1) in the Q10 of microbial respiration and an oxidative EEA. Thus, although warmer winters may induce legacy effects in microbial temperature acclimation, we found no evidence for changes in potential carbon mineralization after spring thaw.

@article{swindles_widespread_2019,
	title = {Widespread drying of {European} peatlands in recent centuries},
	volume = {12},
	doi = {10.1038/s41561-019-0462-z},
	abstract = {Climate warming and human impacts are thought to be causing peatlands to dry, potentially converting them from sinks to sources of carbon. However, it is unclear whether the hydrological status of peatlands has moved beyond their natural envelope. Here we show that European peatlands have undergone substantial, widespread drying during the last {\textasciitilde}300 years. We analyse testate amoeba-derived hydrological reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and Continental Europe to examine changes in peatland surface wetness during the last 2,000 years. We find that 60\% of our study sites were drier during the period 1800–2000 ce than they have been for the last 600 years, 40\% of sites were drier than they have been for 1,000 years and 24\% of sites were drier than they have been for 2,000 years. This marked recent transition in the hydrology of European peatlands is concurrent with compound pressures including climatic drying, warming and direct human impacts on peatlands, although these factors vary among regions and individual sites. Our results suggest that the wetness of many European peatlands may now be moving away from natural baselines. Our findings highlight the need for effective management and restoration of European peatlands.},
	number = {11},
	journal = {Nature Geoscience},
	author = {Swindles, Graeme T and Morris, Paul J and Mullan, Donal J and Payne, Richard J and Roland, Thomas P and Amesbury, Matthew J and Lamentowicz, Mariusz and Turner, T Edward and Gallego-Sala, Angela and Sim, Thomas and {others}},
	year = {2019},
	note = {Publisher: Nature Publishing Group UK London},
	keywords = {\#nosource},
	pages = {922--928},
}

Climate warming and human impacts are thought to be causing peatlands to dry, potentially converting them from sinks to sources of carbon. However, it is unclear whether the hydrological status of peatlands has moved beyond their natural envelope. Here we show that European peatlands have undergone substantial, widespread drying during the last ~300 years. We analyse testate amoeba-derived hydrological reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and Continental Europe to examine changes in peatland surface wetness during the last 2,000 years. We find that 60% of our study sites were drier during the period 1800–2000 ce than they have been for the last 600 years, 40% of sites were drier than they have been for 1,000 years and 24% of sites were drier than they have been for 2,000 years. This marked recent transition in the hydrology of European peatlands is concurrent with compound pressures including climatic drying, warming and direct human impacts on peatlands, although these factors vary among regions and individual sites. Our results suggest that the wetness of many European peatlands may now be moving away from natural baselines. Our findings highlight the need for effective management and restoration of European peatlands.

@article{krab_plant_2019,
	title = {Plant expansion drives bacteria and collembola communities under winter climate change in frost-affected tundra},
	volume = {138},
	issn = {0038-0717},
	url = {https://www.sciencedirect.com/science/article/pii/S0038071719302330},
	doi = {10.1016/j.soilbio.2019.107569},
	abstract = {At high latitudes, winter warming facilitates vegetation expansion into barren frost-affected soils. The interplay of changes in winter climate and plant presence may alter soil functioning via effects on decomposers. Responses of decomposer soil fauna and microorganisms to such changes likely differ from each other, since their life histories, dispersal mechanisms and microhabitats vary greatly. We investigated the relative impacts of short-term winter warming and increases in plant cover on bacteria and collembola community composition in cryoturbated, non-sorted circle tundra. By covering non-sorted circles with insulating gardening fibre cloth (fleeces) or using stone walls accumulating snow, we imposed two climate-change scenarios: snow accumulation increased autumn-to-late winter soil temperatures (−1 cm) by 1.4 °C, while fleeces warmed soils during that period by 1 °C and increased spring temperatures by 1.1 °C. Summer bacteria and collembola communities were sampled from within-circle locations differing in vegetation abundance and soil properties. Two years of winter warming had no effects on either decomposer community. Instead, their community compositions were strongly determined by sampling location: communities in barren circle centres were distinct from those in vegetated outer rims, while communities in sparsely vegetated patches of circle centres were intermediate. Diversity patterns indicate that collembola communities are tightly linked to plant presence while bacteria communities correlated with soil properties. Our results thus suggest that direct effects of short-term winter warming are likely to be minimal, but that vegetation encroachment on barren cryoturbated ground will affect decomposer community composition substantially. At decadal timescales, collembola community changes may follow relatively fast after warming-driven plant establishment into barren areas, whereas bacteria communities may take longer to respond. If shifts in decomposer community composition are indicative for changes in their activity, vegetation overgrowth will likely have much stronger effects on soil functioning in frost-affected tundra than short-term winter warming.},
	journal = {Soil Biology and Biochemistry},
	author = {Krab, Eveline J. and Monteux, Sylvain and Weedon, James T. and Dorrepaal, Ellen},
	month = nov,
	year = {2019},
	keywords = {\#nosource, Arctic, Global warming, Microbes, Shrub encroachment, Snow, Soil fauna},
	pages = {107569},
}

At high latitudes, winter warming facilitates vegetation expansion into barren frost-affected soils. The interplay of changes in winter climate and plant presence may alter soil functioning via effects on decomposers. Responses of decomposer soil fauna and microorganisms to such changes likely differ from each other, since their life histories, dispersal mechanisms and microhabitats vary greatly. We investigated the relative impacts of short-term winter warming and increases in plant cover on bacteria and collembola community composition in cryoturbated, non-sorted circle tundra. By covering non-sorted circles with insulating gardening fibre cloth (fleeces) or using stone walls accumulating snow, we imposed two climate-change scenarios: snow accumulation increased autumn-to-late winter soil temperatures (−1 cm) by 1.4 °C, while fleeces warmed soils during that period by 1 °C and increased spring temperatures by 1.1 °C. Summer bacteria and collembola communities were sampled from within-circle locations differing in vegetation abundance and soil properties. Two years of winter warming had no effects on either decomposer community. Instead, their community compositions were strongly determined by sampling location: communities in barren circle centres were distinct from those in vegetated outer rims, while communities in sparsely vegetated patches of circle centres were intermediate. Diversity patterns indicate that collembola communities are tightly linked to plant presence while bacteria communities correlated with soil properties. Our results thus suggest that direct effects of short-term winter warming are likely to be minimal, but that vegetation encroachment on barren cryoturbated ground will affect decomposer community composition substantially. At decadal timescales, collembola community changes may follow relatively fast after warming-driven plant establishment into barren areas, whereas bacteria communities may take longer to respond. If shifts in decomposer community composition are indicative for changes in their activity, vegetation overgrowth will likely have much stronger effects on soil functioning in frost-affected tundra than short-term winter warming.

@article{blume-werry_dwelling_2019,
	title = {Dwelling in the deep – strongly increased root growth and rooting depth enhance plant interactions with thawing permafrost soil},
	volume = {223},
	issn = {0028-646X},
	url = {https://doi.org/10.1111/nph.15903},
	doi = {10.1111/nph.15903},
	abstract = {Summary Climate-warming-induced permafrost thaw exposes large amounts of carbon and nitrogen in soil at considerable depths, below the seasonally thawing active layer. The extent to which plant roots can reach and interact with these hitherto detached, deep carbon and nitrogen stores remains unknown. We aimed to quantify how permafrost thaw affects root dynamics across soil depths and plant functional types compared with above-ground abundance, and potential consequences for plant?soil interactions. A decade of experimental permafrost thaw strongly increased total root length and growth in the active layer, and deep roots invaded the newly thawed permafrost underneath. Root litter input to soil across all depths was 10 times greater with permafrost thaw. Root growth timing was unaffected by experimental permafrost thaw but peaked later in deeper soil, reflecting the seasonally receding thaw front. Deep-rooting species could sequester 15N added at the base of the ambient active layer in October, which was after root growth had ceased. Deep soil organic matter that has long been locked up in permafrost is thus no longer detached from plant processes upon thaw. Whether via nutrient uptake, carbon storage, or rhizosphere priming, plant root interactions with thawing permafrost soils may feed back on our climate both positively and negatively.},
	number = {3},
	urldate = {2023-07-21},
	journal = {New Phytologist},
	author = {Blume-Werry, Gesche and Milbau, Ann and Teuber, Laurenz M. and Johansson, Margareta and Dorrepaal, Ellen},
	month = aug,
	year = {2019},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, Eriophorum, arctic tundra, fine roots, minirhizotrons, peatland, root biomass, root litter, root phenology},
	pages = {1328--1339},
}

Summary Climate-warming-induced permafrost thaw exposes large amounts of carbon and nitrogen in soil at considerable depths, below the seasonally thawing active layer. The extent to which plant roots can reach and interact with these hitherto detached, deep carbon and nitrogen stores remains unknown. We aimed to quantify how permafrost thaw affects root dynamics across soil depths and plant functional types compared with above-ground abundance, and potential consequences for plant?soil interactions. A decade of experimental permafrost thaw strongly increased total root length and growth in the active layer, and deep roots invaded the newly thawed permafrost underneath. Root litter input to soil across all depths was 10 times greater with permafrost thaw. Root growth timing was unaffected by experimental permafrost thaw but peaked later in deeper soil, reflecting the seasonally receding thaw front. Deep-rooting species could sequester 15N added at the base of the ambient active layer in October, which was after root growth had ceased. Deep soil organic matter that has long been locked up in permafrost is thus no longer detached from plant processes upon thaw. Whether via nutrient uptake, carbon storage, or rhizosphere priming, plant root interactions with thawing permafrost soils may feed back on our climate both positively and negatively.

@article{maranon-jimenez_coupled_2019,
	title = {Coupled carbon and nitrogen losses in response to seven years of chronic warming in subarctic soils},
	volume = {134},
	issn = {0038-0717},
	url = {http://www.sciencedirect.com/science/article/pii/S0038071719301038},
	doi = {10.1016/j.soilbio.2019.03.028},
	abstract = {Increasing temperatures may alter the stoichiometric demands of soil microbes and impair their capacity to stabilize carbon (C) and retain nitrogen (N), with critical consequences for the soil C and N storage at high latitude soils. Geothermally active areas in Iceland provided wide, continuous and stable gradients of soil temperatures to test this hypothesis. In order to characterize the stoichiometric demands of microbes from these subarctic soils, we incubated soils from ambient temperatures after the factorial addition of C, N and P substrates separately and in combination. In a second experiment, soils that had been exposed to different in situ warming intensities (+0, +0.5, +1.8, +3.4, +8.7, +15.9 °C above ambient) for seven years were incubated after the combined addition of C, N and P to evaluate the capacity of soil microbes to store and immobilize C and N at the different warming scenarios. The seven years of chronic soil warming triggered large and proportional soil C and N losses (4.1 ± 0.5\% °C−1 of the stocks in unwarmed soils) from the upper 10 cm of soil, with a predominant depletion of the physically accessible organic substrates that were weakly sorbed in soil minerals up to 8.7 °C warming. Soil microbes met the increasing respiratory demands under conditions of low C accessibility at the expenses of a reduction of the standing biomass in warmer soils. This together with the strict microbial C:N stoichiometric demands also constrained their capacity of N retention, and increased the vulnerability of soil to N losses. Our findings suggest a strong control of microbial physiology and C:N stoichiometric needs on the retention of soil N and on the resilience of soil C stocks from high-latitudes to warming, particularly during periods of vegetation dormancy and low C inputs.},
	urldate = {2019-05-20},
	journal = {Soil Biology and Biochemistry},
	author = {Marañón-Jiménez, S. and Peñuelas, J. and Richter, A. and Sigurdsson, B. D. and Fuchslueger, L. and Leblans, N. I. W. and Janssens, I. A.},
	month = jul,
	year = {2019},
	keywords = {\#nosource, Microbial biomass, Microbial carbon and nutrients limitation, Nitrogen immobilization, Nitrogen loss, Substrate induced respiration, Temperature increase},
	pages = {152--161},
}

Increasing temperatures may alter the stoichiometric demands of soil microbes and impair their capacity to stabilize carbon (C) and retain nitrogen (N), with critical consequences for the soil C and N storage at high latitude soils. Geothermally active areas in Iceland provided wide, continuous and stable gradients of soil temperatures to test this hypothesis. In order to characterize the stoichiometric demands of microbes from these subarctic soils, we incubated soils from ambient temperatures after the factorial addition of C, N and P substrates separately and in combination. In a second experiment, soils that had been exposed to different in situ warming intensities (+0, +0.5, +1.8, +3.4, +8.7, +15.9 °C above ambient) for seven years were incubated after the combined addition of C, N and P to evaluate the capacity of soil microbes to store and immobilize C and N at the different warming scenarios. The seven years of chronic soil warming triggered large and proportional soil C and N losses (4.1 ± 0.5% °C−1 of the stocks in unwarmed soils) from the upper 10 cm of soil, with a predominant depletion of the physically accessible organic substrates that were weakly sorbed in soil minerals up to 8.7 °C warming. Soil microbes met the increasing respiratory demands under conditions of low C accessibility at the expenses of a reduction of the standing biomass in warmer soils. This together with the strict microbial C:N stoichiometric demands also constrained their capacity of N retention, and increased the vulnerability of soil to N losses. Our findings suggest a strong control of microbial physiology and C:N stoichiometric needs on the retention of soil N and on the resilience of soil C stocks from high-latitudes to warming, particularly during periods of vegetation dormancy and low C inputs.

@article{serikova_high_2019,
	title = {High carbon emissions from thermokarst lakes of {Western} {Siberia}},
	volume = {10},
	copyright = {2019 The Author(s)},
	issn = {2041-1723},
	url = {http://www.nature.com/articles/s41467-019-09592-1},
	doi = {10.1038/s41467-019-09592-1},
	abstract = {The Western Siberia Lowland (WSL) is the world’s largest frozen peatland complex, however carbon emissions (CO2+CH4) from lakes in this region remain unknown. Here, the authors sample 76 lakes and show high carbon emissions from lakes across all permafrost zones in the WSL.},
	language = {En},
	number = {1},
	urldate = {2019-06-24},
	journal = {Nature Communications},
	author = {Serikova, S. and Pokrovsky, O. S. and Laudon, H. and Krickov, I. V. and Lim, A. G. and Manasypov, R. M. and Karlsson, J.},
	month = apr,
	year = {2019},
	keywords = {\#nosource},
	pages = {1552},
}

The Western Siberia Lowland (WSL) is the world’s largest frozen peatland complex, however carbon emissions (CO2+CH4) from lakes in this region remain unknown. Here, the authors sample 76 lakes and show high carbon emissions from lakes across all permafrost zones in the WSL.

@article{parts_acclimation_2019,
	title = {Acclimation of {Fine} {Root} {Systems} to {Soil} {Warming}: {Comparison} of an {Experimental} {Setup} and a {Natural} {Soil} {Temperature} {Gradient}},
	volume = {22},
	issn = {1435-0629},
	shorttitle = {Acclimation of {Fine} {Root} {Systems} to {Soil} {Warming}},
	url = {https://doi.org/10.1007/s10021-018-0280-y},
	doi = {10.1007/s10021-018-0280-y},
	abstract = {Global warming is predicted to impact high-latitude and high-altitude forests severely, jeopardizing their overall functioning and carbon storage, both of which depend on the warming response of tree fine root systems. This paper investigates the effect of soil warming on the biomass, morphology and colonizing ectomycorrhizal community of spruce fine and absorptive fine roots. We compare the responses of spruce roots growing at a man-made long-term soil warming (+ 4°C) experiment to results obtained from a geothermal soil temperature gradient (+ 1 to + 14°C) extending to the forest die-off edge, to shed light on the generalizability of the warming response and reveal any thresholds in acclimation ability. Trees in warmer soils formed longer and less-branched absorptive roots with higher specific root length and area, and lower root tissue density in both spruce stands, irrespective of warming method and location. Soil warming at the experimental warming site also supported the occurrence of a more varied EcM community and an increase in the abundance of Tomentella spp., indicating a shift in nutrient foraging. Fine and absorptive fine root biomass decreased toward warmer soil, with a sharp reduction occurring between + 4 and + 6°C from the ambient and leading to the collapse of the fine root system at the geothermal gradient. At the experimental warming site, the applied + 4°C warming had no effect on fine and absorptive fine root biomass. The similar fine root responses at the two warming sites suggest that the observations possibly reflect general acclimation patterns in spruce forests to global warming.},
	language = {en},
	number = {3},
	urldate = {2019-05-20},
	journal = {Ecosystems},
	author = {Parts, Kaarin and Tedersoo, Leho and Schindlbacher, Andreas and Sigurdsson, Bjarni D. and Leblans, Niki I. W. and Oddsdóttir, Edda S. and Borken, Werner and Ostonen, Ivika},
	month = jul,
	year = {2019},
	keywords = {\#nosource, Picea abies, Picea sitchensis, boreal and temperate forests, climate change, ectomycorrhiza, fine root biomass, root tissue density, root traits, soil temperature gradient, specific root length},
	pages = {457--472},
}

Global warming is predicted to impact high-latitude and high-altitude forests severely, jeopardizing their overall functioning and carbon storage, both of which depend on the warming response of tree fine root systems. This paper investigates the effect of soil warming on the biomass, morphology and colonizing ectomycorrhizal community of spruce fine and absorptive fine roots. We compare the responses of spruce roots growing at a man-made long-term soil warming (+ 4°C) experiment to results obtained from a geothermal soil temperature gradient (+ 1 to + 14°C) extending to the forest die-off edge, to shed light on the generalizability of the warming response and reveal any thresholds in acclimation ability. Trees in warmer soils formed longer and less-branched absorptive roots with higher specific root length and area, and lower root tissue density in both spruce stands, irrespective of warming method and location. Soil warming at the experimental warming site also supported the occurrence of a more varied EcM community and an increase in the abundance of Tomentella spp., indicating a shift in nutrient foraging. Fine and absorptive fine root biomass decreased toward warmer soil, with a sharp reduction occurring between + 4 and + 6°C from the ambient and leading to the collapse of the fine root system at the geothermal gradient. At the experimental warming site, the applied + 4°C warming had no effect on fine and absorptive fine root biomass. The similar fine root responses at the two warming sites suggest that the observations possibly reflect general acclimation patterns in spruce forests to global warming.

@article{cameron_uneven_2019,
	title = {Uneven global distribution of food web studies under climate change},
	volume = {10},
	issn = {2150-8925},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.2645},
	doi = {10.1002/ecs2.2645},
	abstract = {Abstract Trophic interactions within food webs affect species distributions, coexistence, and provision of ecosystem services but can be strongly impacted by climatic changes. Understanding these impacts is therefore essential for managing ecosystems and sustaining human well-being. Here, we conducted a global synthesis of terrestrial, marine, and freshwater studies to identify key gaps in our knowledge of climate change impacts on food webs and determine whether the areas currently studied are those most likely to be impacted by climate change. We found research suffers from a strong geographic bias, with only 3.5\% of studies occurring in the tropics. Importantly, the distribution of sites sampled under projected climate changes was biased?areas with decreases or large increases in precipitation and areas with low magnitudes of temperature change were under-represented. Our results suggest that understanding of climate change impacts on food webs could be broadened by considering more than two trophic levels, responses in addition to species abundance and biomass, impacts of a wider suite of climatic variables, and tropical ecosystems. Most importantly, to enable better forecasts of biodiversity responses to climate change, we identify critically under-represented geographic regions and climatic conditions which should be prioritized in future research.},
	number = {3},
	urldate = {2019-11-05},
	journal = {Ecosphere},
	author = {Cameron, Erin K. and Sundqvist, Maja K. and Keith, Sally A. and CaraDonna, Paul J. and Mousing, Erik A. and Nilsson, Karin A. and Metcalfe, Daniel B. and Classen, Aimée T.},
	month = mar,
	year = {2019},
	keywords = {\#nosource, aquatic, climate change, data gaps, extreme events, food webs, freshwater, global, marine, precipitation, species interactions, terrestrial, warming},
	pages = {e02645},
}

Abstract Trophic interactions within food webs affect species distributions, coexistence, and provision of ecosystem services but can be strongly impacted by climatic changes. Understanding these impacts is therefore essential for managing ecosystems and sustaining human well-being. Here, we conducted a global synthesis of terrestrial, marine, and freshwater studies to identify key gaps in our knowledge of climate change impacts on food webs and determine whether the areas currently studied are those most likely to be impacted by climate change. We found research suffers from a strong geographic bias, with only 3.5% of studies occurring in the tropics. Importantly, the distribution of sites sampled under projected climate changes was biased?areas with decreases or large increases in precipitation and areas with low magnitudes of temperature change were under-represented. Our results suggest that understanding of climate change impacts on food webs could be broadened by considering more than two trophic levels, responses in addition to species abundance and biomass, impacts of a wider suite of climatic variables, and tropical ecosystems. Most importantly, to enable better forecasts of biodiversity responses to climate change, we identify critically under-represented geographic regions and climatic conditions which should be prioritized in future research.

@article{sundqvist_experimental_2019,
	title = {Experimental evidence of the long-term effects of reindeer on {Arctic} vegetation greenness and species richness at a larger landscape scale},
	volume = {107},
	copyright = {© 2019 The Authors. Journal of Ecology © 2019 British Ecological Society},
	issn = {1365-2745},
	url = {http://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.13201},
	doi = {10.1111/1365-2745.13201},
	abstract = {Large herbivores influence plant community structure and ecosystem processes in many ecosystems. In large parts of the Arctic, reindeer (or caribou) are the only large herbivores present. Recent studies show that reindeer have the potential to mitigate recent warming-induced shrub encroachment in the Arctic and the associated greening of high-latitude ecosystems. This will potentially have large scale consequences for ecosystem productivity and carbon cycling. To date, information on variation in the interactions between reindeer and plants across Arctic landscapes has been scarce. We utilized a network of experimental sites across a latitudinal gradient in the Scandinavian mountains where reindeer have been excluded from 59 study plots for at least 15 years. We used this study system to test the effect of long-term exclusion of reindeer on the abundance of major plant functional groups, the greenness indexes Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), soil mineral nitrogen (N) and phosphorous (P), and species richness, and to determine whether the effect of reindeer exclusion is dependent on reindeer density, productivity, soil fertility or climate. We found that NDVI and LAI, lichen and deciduous shrub abundances were largely reduced while soil mineral N was enhanced by reindeer. The direction and amplitude of other plant functional group responses to reindeer exclusion differed between forest and tundra as well as shrub- and herbaceous-dominated vegetation. Higher reindeer densities were related to decreased plant species richness in low-productive sites and to increased species richness in productive sites. The relative reduction in LAI and associated absolute reductions of deciduous shrubs in response to reindeer were positively related to reindeer density, while the relative reduction in NDVI was not. Further, relative reductions in LAI and NDVI in response to reindeer were unrelated to climate and soil fertility. Synthesis. Our results provide long-term experimental evidence highlighting the role of reindeer density in regulating plant species richness, global climate change induced greenness patterns and shrub encroachment at regional scales in the Arctic. These findings emphasize the need to consider reindeer in models predicting vegetation patterns and changes in high-latitude ecosystems.},
	language = {en},
	number = {6},
	urldate = {2019-11-05},
	journal = {Journal of Ecology},
	author = {Sundqvist, Maja K. and Moen, Jon and Björk, Robert G. and Vowles, Tage and Kytöviita, Minna-Maarit and Parsons, Malcolm A. and Olofsson, Johan},
	year = {2019},
	keywords = {\#nosource, climate change, forest, grazing, large mammalian herbivores, plant community composition, plant–herbivore interactions, soil nutrients, tundra},
	pages = {2724--2736},
}

Large herbivores influence plant community structure and ecosystem processes in many ecosystems. In large parts of the Arctic, reindeer (or caribou) are the only large herbivores present. Recent studies show that reindeer have the potential to mitigate recent warming-induced shrub encroachment in the Arctic and the associated greening of high-latitude ecosystems. This will potentially have large scale consequences for ecosystem productivity and carbon cycling. To date, information on variation in the interactions between reindeer and plants across Arctic landscapes has been scarce. We utilized a network of experimental sites across a latitudinal gradient in the Scandinavian mountains where reindeer have been excluded from 59 study plots for at least 15 years. We used this study system to test the effect of long-term exclusion of reindeer on the abundance of major plant functional groups, the greenness indexes Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), soil mineral nitrogen (N) and phosphorous (P), and species richness, and to determine whether the effect of reindeer exclusion is dependent on reindeer density, productivity, soil fertility or climate. We found that NDVI and LAI, lichen and deciduous shrub abundances were largely reduced while soil mineral N was enhanced by reindeer. The direction and amplitude of other plant functional group responses to reindeer exclusion differed between forest and tundra as well as shrub- and herbaceous-dominated vegetation. Higher reindeer densities were related to decreased plant species richness in low-productive sites and to increased species richness in productive sites. The relative reduction in LAI and associated absolute reductions of deciduous shrubs in response to reindeer were positively related to reindeer density, while the relative reduction in NDVI was not. Further, relative reductions in LAI and NDVI in response to reindeer were unrelated to climate and soil fertility. Synthesis. Our results provide long-term experimental evidence highlighting the role of reindeer density in regulating plant species richness, global climate change induced greenness patterns and shrub encroachment at regional scales in the Arctic. These findings emphasize the need to consider reindeer in models predicting vegetation patterns and changes in high-latitude ecosystems.

@article{panneer_selvam_photo-reactivity_2019,
	title = {Photo-reactivity of dissolved organic carbon in the freshwater continuum},
	volume = {81},
	issn = {1420-9055},
	url = {https://doi.org/10.1007/s00027-019-0653-0},
	doi = {10.1007/s00027-019-0653-0},
	abstract = {The patterns in dissolved organic carbon (DOC) photo-mineralization along the freshwater continuum from land to sea are poorly known. Specifically, it has not been resolved how the photo-degradation of DOC into CO2 (PD) depends on the combination of intrinsic properties of DOC and extrinsic variables that affect the photo-reactions. We measured PD per unit of absorbed ultraviolet light energy (PD-Ew) in headwater streams, lakes, intermediate rivers and river mouths in Sweden. Surprisingly, no trend of decreasing PD-Ew was found with decreases in colored DOC. However, there was a relationship between PD-Ew and pH, best described by a quadratic (U-shaped) curve, indicating environmental control of photo-reactivity. Interestingly, the highest values for both of these variables were recorded for river mouths. Moreover, PD-Ew increased with proxy variables for the amount of autochthonous DOC in the water. Thus, changes in pH and autochthonous DOC input along the continuum may sustain high DOC photo-mineralization throughout continental aquatic networks.},
	language = {en},
	number = {4},
	urldate = {2019-07-30},
	journal = {Aquatic Sciences},
	author = {Panneer Selvam, Balathandayuthabani and Lapierre, Jean-François and Soares, Ana R. A. and Bastviken, David and Karlsson, Jan and Berggren, Martin},
	month = jul,
	year = {2019},
	keywords = {\#nosource, Colored dissolved organic matter, Dissolved organic carbon, Freshwater systems, Photo-reactivity, pH},
	pages = {57},
}

The patterns in dissolved organic carbon (DOC) photo-mineralization along the freshwater continuum from land to sea are poorly known. Specifically, it has not been resolved how the photo-degradation of DOC into CO2 (PD) depends on the combination of intrinsic properties of DOC and extrinsic variables that affect the photo-reactions. We measured PD per unit of absorbed ultraviolet light energy (PD-Ew) in headwater streams, lakes, intermediate rivers and river mouths in Sweden. Surprisingly, no trend of decreasing PD-Ew was found with decreases in colored DOC. However, there was a relationship between PD-Ew and pH, best described by a quadratic (U-shaped) curve, indicating environmental control of photo-reactivity. Interestingly, the highest values for both of these variables were recorded for river mouths. Moreover, PD-Ew increased with proxy variables for the amount of autochthonous DOC in the water. Thus, changes in pH and autochthonous DOC input along the continuum may sustain high DOC photo-mineralization throughout continental aquatic networks.

@article{shirokova_humic_2019,
	title = {Humic surface waters of frozen peat bogs (permafrost zone) are highly resistant to bio- and photodegradation},
	volume = {16},
	issn = {1726-4170},
	url = {https://www.biogeosciences.net/16/2511/2019/},
	doi = {10.5194/bg-16-2511-2019},
	abstract = {{\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} In contrast to the large number of studies on humic waters from permafrost-free regions and oligotrophic waters from permafrost-bearing regions, the bio- and photolability of DOM from the humic surface waters of permafrost-bearing regions has not been thoroughly evaluated. Following standardized protocol, we measured biodegradation (at low, intermediate and high temperatures) and photodegradation (at one intermediate temperature) of DOM in surface waters along the hydrological continuum (depression {\textless}span class="inline-formula"{\textgreater}→{\textless}/span{\textgreater} stream {\textless}span class="inline-formula"{\textgreater}→{\textless}/span{\textgreater} thermokarst lake {\textless}span class="inline-formula"{\textgreater}→{\textless}/span{\textgreater} Pechora River) within a frozen peatland in European Russia. In all systems, within the experimental resolution of 5\ \% to 10\ \%, there was no bio- or photodegradation of DOM over a 1-month incubation period. It is possible that the main cause of the lack of degradation is the dominance of allochthonous refractory (soil, peat) DOM in all waters studied. However, all surface waters were supersaturated with {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater}. Thus, this study suggests that, rather than bio- and photodegradation of DOM in the water column, other factors such as peat pore-water DOM processing and respiration of sediments are the main drivers of elevated {\textless}span class="inline-formula"{\textgreater}\textit{p}CO$_{\textrm{2}}${\textless}/span{\textgreater} and {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater} emission in humic boreal waters of frozen peat bogs.{\textless}/p{\textgreater}},
	language = {English},
	number = {12},
	urldate = {2019-07-30},
	journal = {Biogeosciences},
	author = {Shirokova, Liudmila S. and Chupakov, Artem V. and Zabelina, Svetlana A. and Neverova, Natalia V. and Payandi-Rolland, Dahedrey and Causserand, Carole and Karlsson, Jan and Pokrovsky, Oleg S.},
	month = jun,
	year = {2019},
	keywords = {\#nosource},
	pages = {2511--2526},
}

\textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater In contrast to the large number of studies on humic waters from permafrost-free regions and oligotrophic waters from permafrost-bearing regions, the bio- and photolability of DOM from the humic surface waters of permafrost-bearing regions has not been thoroughly evaluated. Following standardized protocol, we measured biodegradation (at low, intermediate and high temperatures) and photodegradation (at one intermediate temperature) of DOM in surface waters along the hydrological continuum (depression \textlessspan class="inline-formula"\textgreater→\textless/span\textgreater stream \textlessspan class="inline-formula"\textgreater→\textless/span\textgreater thermokarst lake \textlessspan class="inline-formula"\textgreater→\textless/span\textgreater Pechora River) within a frozen peatland in European Russia. In all systems, within the experimental resolution of 5 % to 10 %, there was no bio- or photodegradation of DOM over a 1-month incubation period. It is possible that the main cause of the lack of degradation is the dominance of allochthonous refractory (soil, peat) DOM in all waters studied. However, all surface waters were supersaturated with \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater. Thus, this study suggests that, rather than bio- and photodegradation of DOM in the water column, other factors such as peat pore-water DOM processing and respiration of sediments are the main drivers of elevated \textlessspan class="inline-formula"\textgreaterpCO$_{\textrm{2}}$\textless/span\textgreater and \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater emission in humic boreal waters of frozen peat bogs.\textless/p\textgreater

@article{ogden_trouble_2019,
	title = {Trouble brewing?},
	volume = {242},
	issn = {0262-4079},
	url = {http://www.sciencedirect.com/science/article/pii/S0262407919310371},
	doi = {10.1016/S0262-4079(19)31037-1},
	abstract = {An ingenious experiment is using the humble teabag to probe worrying carbon emissions in the Arctic, finds Lesley Evans Ogden},
	language = {en},
	number = {3233},
	urldate = {2020-03-19},
	journal = {New Scientist},
	author = {Ogden, Lesley Evans},
	month = jun,
	year = {2019},
	keywords = {\#nosource},
	pages = {42--43},
}

An ingenious experiment is using the humble teabag to probe worrying carbon emissions in the Arctic, finds Lesley Evans Ogden

@article{rheubottom_hiding_2019,
	title = {Hiding in the background: community-level patterns in invertebrate herbivory across the tundra biome},
	volume = {42},
	issn = {1432-2056},
	shorttitle = {Hiding in the background},
	url = {https://doi.org/10.1007/s00300-019-02568-3},
	doi = {10.1007/s00300-019-02568-3},
	abstract = {Invertebrate herbivores depend on external temperature for growth and metabolism. Continued warming in tundra ecosystems is proposed to result in increased invertebrate herbivory. However, empirical data about how current levels of invertebrate herbivory vary across the Arctic is limited and generally restricted to a single host plant or a small group of species, so predicting future change remains challenging. We investigated large-scale patterns of invertebrate herbivory across the tundra biome at the community level and explored how these patterns are related to long-term climatic conditions and year-of-sampling weather, habitat characteristics, and aboveground biomass production. Utilizing a standardized protocol, we collected samples from 92 plots nested within 20 tundra sites during summer 2015. We estimated the community-weighted biomass lost based on the total leaf area consumed by invertebrates for the most common plant species within each plot. Overall, invertebrate herbivory was prevalent at low intensities across the tundra, with estimates averaging 0.94\% and ranging between 0.02 and 5.69\% of plant biomass. Our results suggest that mid-summer temperature influences the intensity of invertebrate herbivory at the community level, consistent with the hypothesis that climate warming should increase plant losses to invertebrates in the tundra. However, most of the observed variation in herbivory was associated with other site level characteristics, indicating that other local ecological factors also play an important role. More details about the local drivers of invertebrate herbivory are necessary to predict the consequences for rapidly changing tundra ecosystems.},
	language = {en},
	number = {10},
	urldate = {2020-03-19},
	journal = {Polar Biology},
	author = {Rheubottom, Sarah I. and Barrio, Isabel C. and Kozlov, Mikhail V. and Alatalo, Juha M. and Andersson, Tommi and Asmus, Ashley L. and Baubin, Capucine and Brearley, Francis Q. and Egelkraut, Dagmar D. and Ehrich, Dorothee and Gauthier, Gilles and Jónsdóttir, Ingibjörg Svala and Konieczka, Sophia and Lévesque, Esther and Olofsson, Johan and Prevéy, Janet S. and Slevan-Tremblay, Guillaume and Sokolov, Aleksandr and Sokolova, Natalia and Sokovnina, Svetlana and Speed, James D. M. and Suominen, Otso and Zverev, Vitali and Hik, David S.},
	month = oct,
	year = {2019},
	keywords = {\#nosource},
	pages = {1881--1897},
}

Invertebrate herbivores depend on external temperature for growth and metabolism. Continued warming in tundra ecosystems is proposed to result in increased invertebrate herbivory. However, empirical data about how current levels of invertebrate herbivory vary across the Arctic is limited and generally restricted to a single host plant or a small group of species, so predicting future change remains challenging. We investigated large-scale patterns of invertebrate herbivory across the tundra biome at the community level and explored how these patterns are related to long-term climatic conditions and year-of-sampling weather, habitat characteristics, and aboveground biomass production. Utilizing a standardized protocol, we collected samples from 92 plots nested within 20 tundra sites during summer 2015. We estimated the community-weighted biomass lost based on the total leaf area consumed by invertebrates for the most common plant species within each plot. Overall, invertebrate herbivory was prevalent at low intensities across the tundra, with estimates averaging 0.94% and ranging between 0.02 and 5.69% of plant biomass. Our results suggest that mid-summer temperature influences the intensity of invertebrate herbivory at the community level, consistent with the hypothesis that climate warming should increase plant losses to invertebrates in the tundra. However, most of the observed variation in herbivory was associated with other site level characteristics, indicating that other local ecological factors also play an important role. More details about the local drivers of invertebrate herbivory are necessary to predict the consequences for rapidly changing tundra ecosystems.

@article{macura_impact_2019,
	title = {Impact of structural habitat modifications in coastal temperate systems on fish recruitment: a systematic review},
	volume = {8},
	issn = {2047-2382},
	shorttitle = {Impact of structural habitat modifications in coastal temperate systems on fish recruitment},
	url = {https://doi.org/10.1186/s13750-019-0157-3},
	doi = {10.1186/s13750-019-0157-3},
	abstract = {Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.},
	number = {1},
	urldate = {2020-03-19},
	journal = {Environmental Evidence},
	author = {Macura, Biljana and Byström, Pär and Airoldi, Laura and Eriksson, Britas Klemens and Rudstam, Lars and Støttrup, Josianne G.},
	month = mar,
	year = {2019},
	keywords = {\#nosource},
	pages = {14},
}

Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.

@article{phillips_global_2019,
	title = {Global distribution of earthworm diversity},
	volume = {366},
	issn = {0036-8075, 1095-9203},
	url = {https://www.sciencemag.org/lookup/doi/10.1126/science.aax4851},
	doi = {10.1126/science.aax4851},
	language = {en},
	number = {6464},
	urldate = {2020-03-19},
	journal = {Science},
	author = {Phillips, Helen R. P. and Guerra, Carlos A. and Bartz, Marie L. C. and Briones, Maria J. I. and Brown, George and Crowther, Thomas W. and Ferlian, Olga and Gongalsky, Konstantin B. and van den Hoogen, Johan and Krebs, Julia and Orgiazzi, Alberto and Routh, Devin and Schwarz, Benjamin and Bach, Elizabeth M. and Bennett, Joanne and Brose, Ulrich and Decaëns, Thibaud and König-Ries, Birgitta and Loreau, Michel and Mathieu, Jérôme and Mulder, Christian and van der Putten, Wim H. and Ramirez, Kelly S. and Rillig, Matthias C. and Russell, David and Rutgers, Michiel and Thakur, Madhav P. and de Vries, Franciska T. and Wall, Diana H. and Wardle, David A. and Arai, Miwa and Ayuke, Fredrick O. and Baker, Geoff H. and Beauséjour, Robin and Bedano, José C. and Birkhofer, Klaus and Blanchart, Eric and Blossey, Bernd and Bolger, Thomas and Bradley, Robert L. and Callaham, Mac A. and Capowiez, Yvan and Caulfield, Mark E. and Choi, Amy and Crotty, Felicity V. and Dávalos, Andrea and Cosin, Darío J. Diaz and Dominguez, Anahí and Duhour, Andrés Esteban and van Eekeren, Nick and Emmerling, Christoph and Falco, Liliana B. and Fernández, Rosa and Fonte, Steven J. and Fragoso, Carlos and Franco, André L. C. and Fugère, Martine and Fusilero, Abegail T. and Gholami, Shaieste and Gundale, Michael J. and López, Mónica Gutiérrez and Hackenberger, Davorka K. and Hernández, Luis M. and Hishi, Takuo and Holdsworth, Andrew R. and Holmstrup, Martin and Hopfensperger, Kristine N. and Lwanga, Esperanza Huerta and Huhta, Veikko and Hurisso, Tunsisa T. and Iannone, Basil V. and Iordache, Madalina and Joschko, Monika and Kaneko, Nobuhiro and Kanianska, Radoslava and Keith, Aidan M. and Kelly, Courtland A. and Kernecker, Maria L. and Klaminder, Jonatan and Koné, Armand W. and Kooch, Yahya and Kukkonen, Sanna T. and Lalthanzara, H. and Lammel, Daniel R. and Lebedev, Iurii M. and Li, Yiqing and Lidon, Juan B. Jesus and Lincoln, Noa K. and Loss, Scott R. and Marichal, Raphael and Matula, Radim and Moos, Jan Hendrik and Moreno, Gerardo and Morón-Ríos, Alejandro and Muys, Bart and Neirynck, Johan and Norgrove, Lindsey and Novo, Marta and Nuutinen, Visa and Nuzzo, Victoria and Rahman P, Mujeeb and Pansu, Johan and Paudel, Shishir and Pérès, Guénola and Pérez-Camacho, Lorenzo and Piñeiro, Raúl and Ponge, Jean-François and Rashid, Muhammad Imtiaz and Rebollo, Salvador and Rodeiro-Iglesias, Javier and Rodríguez, Miguel Á. and Roth, Alexander M. and Rousseau, Guillaume X. and Rozen, Anna and Sayad, Ehsan and van Schaik, Loes and Scharenbroch, Bryant C. and Schirrmann, Michael and Schmidt, Olaf and Schröder, Boris and Seeber, Julia and Shashkov, Maxim P. and Singh, Jaswinder and Smith, Sandy M. and Steinwandter, Michael and Talavera, José A. and Trigo, Dolores and Tsukamoto, Jiro and de Valença, Anne W. and Vanek, Steven J. and Virto, Iñigo and Wackett, Adrian A. and Warren, Matthew W. and Wehr, Nathaniel H. and Whalen, Joann K. and Wironen, Michael B. and Wolters, Volkmar and Zenkova, Irina V. and Zhang, Weixin and Cameron, Erin K. and Eisenhauer, Nico},
	month = oct,
	year = {2019},
	keywords = {\#nosource},
	pages = {480--485},
}

@article{truchy_partitioning_2019,
	title = {Partitioning spatial, environmental, and community drivers of ecosystem functioning},
	volume = {34},
	issn = {1572-9761},
	url = {https://doi.org/10.1007/s10980-019-00894-9},
	doi = {10.1007/s10980-019-00894-9},
	abstract = {Community composition, environmental variation, and spatial structuring can influence ecosystem functioning, and ecosystem service delivery. While the role of space in regulating ecosystem functioning is well recognised in theory, it is rarely considered explicitly in empirical studies.},
	language = {en},
	number = {10},
	urldate = {2020-03-19},
	journal = {Landscape Ecology},
	author = {Truchy, Amélie and Göthe, Emma and Angeler, David G. and Ecke, Frauke and Sponseller, Ryan A. and Bundschuh, Mirco and Johnson, Richard K. and McKie, Brendan G.},
	month = oct,
	year = {2019},
	keywords = {\#nosource},
	pages = {2371--2384},
}

Community composition, environmental variation, and spatial structuring can influence ecosystem functioning, and ecosystem service delivery. While the role of space in regulating ecosystem functioning is well recognised in theory, it is rarely considered explicitly in empirical studies.

@article{tiwari_contrasting_2019,
	title = {Contrasting responses in dissolved organic carbon to extreme climate events from adjacent boreal landscapes in {Northern} {Sweden}},
	volume = {14},
	issn = {1748-9326},
	url = {https://iopscience.iop.org/article/10.1088/1748-9326/ab23d4},
	doi = {10.1088/1748-9326/ab23d4},
	language = {en},
	number = {8},
	urldate = {2020-03-19},
	journal = {Environmental Research Letters},
	author = {Tiwari, Tejshree and Sponseller, Ryan A and Laudon, Hjalmar},
	month = jul,
	year = {2019},
	keywords = {\#nosource},
	pages = {084007},
}

@article{bidleman_bromoanisoles_2019,
	title = {Bromoanisoles and methoxylated bromodiphenyl ethers in macroalgae from {Nordic} coastal regions},
	volume = {21},
	issn = {2050-7887, 2050-7895},
	url = {http://xlink.rsc.org/?DOI=C9EM00042A},
	doi = {10.1039/C9EM00042A},
	abstract = {The content of bromoanisoles and methoxylated bromodiphenyl ethers varies by orders of magnitude among sixteen species of macroalgae collected from Nordic coastal waters.
          , 
            
              Marine macroalgae are used worldwide for human consumption, animal feed, cosmetics and agriculture. In addition to beneficial nutrients, macroalgae contain halogenated natural products (HNPs), some of which have toxic properties similar to those of well-known anthropogenic contaminants. Sixteen species of red, green and brown macroalgae were collected in 2017–2018 from coastal waters of the northern Baltic Sea, Sweden Atlantic and Norway Atlantic, and analyzed for bromoanisoles (BAs) and methoxylated bromodiphenyl ethers (MeO-BDEs). Target compounds were quantified by gas chromatography-low resolution mass spectrometry (GC-LRMS), with qualitative confirmation in selected species by GC-high resolution mass spectrometry (GC-HRMS). Quantified compounds were 2,4-diBA, 2,4,6-triBA, 2′-MeO-BDE68, 6-MeO-BDE47, and two tribromo-MeO-BDEs and one tetrabromo-MeO-BDE with unknown bromine substituent positions. Semiquantitative results for pentabromo-MeO-BDEs were also obtained for a few species by GC-HRMS. Three extraction methods were compared; soaking in methanol, soaking in methanol–dichloromethane, and blending with mixed solvents. Extraction yields of BAs did not differ significantly (
              p
              {\textgreater} 0.05) with the three methods and the two soaking methods gave equivalent yields of MeO-BDEs. Extraction efficiencies of MeO-BDEs were significantly lower using the blend method (
              p
              {\textless} 0.05). For reasons of simplicity and efficiency, the soaking methods are preferred. Concentrations varied by orders of magnitude among species: ∑
              2
              BAs 57 to 57 700 and ∑
              5
              MeO-BDEs {\textless} 10 to 476 pg g
              −1
              wet weight (ww). Macroalgae standing out with ∑
              2
              BAs {\textgreater}1000 pg g
              −1
              ww were
              Ascophyllum nodosum
              ,
              Ceramium tenuicorne
              ,
              Ceramium virgatum
              ,
              Fucus radicans
              ,
              Fucus serratus
              ,
              Fucus vesiculosus
              ,
              Saccharina latissima
              ,
              Laminaria digitata
              , and
              Acrosiphonia/Spongomorpha
              sp. Species
              A. nodosum
              ,
              C. tenuicorne
              ,
              Chara virgata
              ,
              F. radicans
              and
              F. vesiculosus
              (Sweden Atlantic only) had ∑
              5
              MeO-BDEs {\textgreater}100 pg g
              −1
              ww. Profiles of individual compounds showed distinct differences among species and locations.},
	language = {en},
	number = {5},
	urldate = {2020-03-19},
	journal = {Environmental Science: Processes \& Impacts},
	author = {Bidleman, Terry F. and Andersson, Agneta and Brugel, Sonia and Ericson, Lars and Haglund, Peter and Kupryianchyk, Darya and Lau, Danny C. P. and Liljelind, Per and Lundin, Lisa and Tysklind, Anders and Tysklind, Mats},
	year = {2019},
	keywords = {\#nosource},
	pages = {881--892},
}

The content of bromoanisoles and methoxylated bromodiphenyl ethers varies by orders of magnitude among sixteen species of macroalgae collected from Nordic coastal waters. , Marine macroalgae are used worldwide for human consumption, animal feed, cosmetics and agriculture. In addition to beneficial nutrients, macroalgae contain halogenated natural products (HNPs), some of which have toxic properties similar to those of well-known anthropogenic contaminants. Sixteen species of red, green and brown macroalgae were collected in 2017–2018 from coastal waters of the northern Baltic Sea, Sweden Atlantic and Norway Atlantic, and analyzed for bromoanisoles (BAs) and methoxylated bromodiphenyl ethers (MeO-BDEs). Target compounds were quantified by gas chromatography-low resolution mass spectrometry (GC-LRMS), with qualitative confirmation in selected species by GC-high resolution mass spectrometry (GC-HRMS). Quantified compounds were 2,4-diBA, 2,4,6-triBA, 2′-MeO-BDE68, 6-MeO-BDE47, and two tribromo-MeO-BDEs and one tetrabromo-MeO-BDE with unknown bromine substituent positions. Semiquantitative results for pentabromo-MeO-BDEs were also obtained for a few species by GC-HRMS. Three extraction methods were compared; soaking in methanol, soaking in methanol–dichloromethane, and blending with mixed solvents. Extraction yields of BAs did not differ significantly ( p \textgreater 0.05) with the three methods and the two soaking methods gave equivalent yields of MeO-BDEs. Extraction efficiencies of MeO-BDEs were significantly lower using the blend method ( p \textless 0.05). For reasons of simplicity and efficiency, the soaking methods are preferred. Concentrations varied by orders of magnitude among species: ∑ 2 BAs 57 to 57 700 and ∑ 5 MeO-BDEs \textless 10 to 476 pg g −1 wet weight (ww). Macroalgae standing out with ∑ 2 BAs \textgreater1000 pg g −1 ww were Ascophyllum nodosum , Ceramium tenuicorne , Ceramium virgatum , Fucus radicans , Fucus serratus , Fucus vesiculosus , Saccharina latissima , Laminaria digitata , and Acrosiphonia/Spongomorpha sp. Species A. nodosum , C. tenuicorne , Chara virgata , F. radicans and F. vesiculosus (Sweden Atlantic only) had ∑ 5 MeO-BDEs \textgreater100 pg g −1 ww. Profiles of individual compounds showed distinct differences among species and locations.

@article{mojarrad_effect_2019,
	title = {The {Effect} of {Stream} {Discharge} on {Hyporheic} {Exchange}},
	volume = {11},
	issn = {2073-4441},
	url = {https://www.mdpi.com/2073-4441/11/7/1436},
	doi = {10.3390/w11071436},
	abstract = {Streambed morphology, streamflow dynamics, and the heterogeneity of streambed sediments critically controls the interaction between surface water and groundwater. The present study investigated the impact of different flow regimes on hyporheic exchange in a boreal stream in northern Sweden using experimental and numerical approaches. Low-, base-, and high-flow discharges were simulated by regulating the streamflow upstream in the study area, and temperature was used as the natural tracer to monitor the impact of the different flow discharges on hyporheic exchange fluxes in stretches of stream featuring gaining and losing conditions. A numerical model was developed using geomorphological and hydrological properties of the stream and was then used to perform a detailed analysis of the subsurface water flow. Additionally, the impact of heterogeneity in sediment permeability on hyporheic exchange fluxes was investigated. Both the experimental and modelling results show that temporally increasing flow resulted in a larger (deeper) extent of the hyporheic zone as well as longer hyporheic flow residence times. However, the result of the numerical analysis is strongly controlled by heterogeneity in sediment permeability. In particular, for homogeneous sediments, the fragmentation of upwelling length substantially varies with streamflow dynamics due to the contribution of deeper fluxes.},
	language = {en},
	number = {7},
	urldate = {2019-07-30},
	journal = {Water},
	author = {Mojarrad, Brian Babak and Betterle, Andrea and Singh, Tanu and Olid, Carolina and Wörman, Anders},
	month = jul,
	year = {2019},
	keywords = {\#nosource},
	pages = {1436},
}

Streambed morphology, streamflow dynamics, and the heterogeneity of streambed sediments critically controls the interaction between surface water and groundwater. The present study investigated the impact of different flow regimes on hyporheic exchange in a boreal stream in northern Sweden using experimental and numerical approaches. Low-, base-, and high-flow discharges were simulated by regulating the streamflow upstream in the study area, and temperature was used as the natural tracer to monitor the impact of the different flow discharges on hyporheic exchange fluxes in stretches of stream featuring gaining and losing conditions. A numerical model was developed using geomorphological and hydrological properties of the stream and was then used to perform a detailed analysis of the subsurface water flow. Additionally, the impact of heterogeneity in sediment permeability on hyporheic exchange fluxes was investigated. Both the experimental and modelling results show that temporally increasing flow resulted in a larger (deeper) extent of the hyporheic zone as well as longer hyporheic flow residence times. However, the result of the numerical analysis is strongly controlled by heterogeneity in sediment permeability. In particular, for homogeneous sediments, the fragmentation of upwelling length substantially varies with streamflow dynamics due to the contribution of deeper fluxes.

@article{rocherros_landscape_2019,
	title = {Landscape process domains drive patterns of {CO2} evasion from river networks},
	volume = {4},
	copyright = {© 2019 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.},
	issn = {2378-2242},
	url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10108},
	doi = {10.1002/lol2.10108},
	abstract = {Streams are important emitters of CO2 but extreme spatial variability in their physical properties can make upscaling very uncertain. Here, we determined critical drivers of stream CO2 evasion at scales from 30 to 400 m across a 52.5 km2 catchment in northern Sweden. We found that turbulent reaches never have elevated CO2 concentrations, while less turbulent locations can potentially support a broad range of CO2 concentrations, consistent with global observations. The predictability of stream pCO2 is greatly improved when we include a proxy for soil-stream connectivity. Catchment topography shapes network patterns of evasion by creating hydrologically linked “domains” characterized by high water-atmosphere exchange and/or strong soil-stream connection. This template generates spatial variability in the drivers of CO2 evasion that can strongly bias regional and global estimates. To overcome this complexity, we provide the foundations of a mechanistic framework of CO2 evasion by considering how landscape process domains regulate transfer and supply.},
	language = {en},
	number = {4},
	urldate = {2019-08-30},
	journal = {Limnology and Oceanography Letters},
	author = {Rocher‐Ros, Gerard and Sponseller, Ryan A. and Lidberg, William and Mörth, Carl-Magnus and Giesler, Reiner},
	year = {2019},
	keywords = {\#nosource},
	pages = {87--95},
}

Streams are important emitters of CO2 but extreme spatial variability in their physical properties can make upscaling very uncertain. Here, we determined critical drivers of stream CO2 evasion at scales from 30 to 400 m across a 52.5 km2 catchment in northern Sweden. We found that turbulent reaches never have elevated CO2 concentrations, while less turbulent locations can potentially support a broad range of CO2 concentrations, consistent with global observations. The predictability of stream pCO2 is greatly improved when we include a proxy for soil-stream connectivity. Catchment topography shapes network patterns of evasion by creating hydrologically linked “domains” characterized by high water-atmosphere exchange and/or strong soil-stream connection. This template generates spatial variability in the drivers of CO2 evasion that can strongly bias regional and global estimates. To overcome this complexity, we provide the foundations of a mechanistic framework of CO2 evasion by considering how landscape process domains regulate transfer and supply.

@article{cazelles_homogenization_2019,
	title = {Homogenization of freshwater lakes: {Recent} compositional shifts in fish communities are explained by gamefish movement and not climate change},
	volume = {25},
	copyright = {© 2019 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	shorttitle = {Homogenization of freshwater lakes},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14829},
	doi = {10.1111/gcb.14829},
	abstract = {Globally, lake fish communities are being subjected to a range of scale-dependent anthropogenic pressures, from climate change to eutrophication, and from overexploitation to species introductions. As a consequence, the composition of these communities is being reshuffled, in most cases leading to a surge in taxonomic similarity at the regional scale termed homogenization. The drivers of homogenization remain unclear, which may be a reflection of interactions between various environmental changes. In this study, we investigate two potential drivers of the recent changes in the composition of freshwater fish communities: recreational fishing and climate change. Our results, derived from 524 lakes of Ontario, Canada sampled in two periods (1965–1982 and 2008–2012), demonstrate that the main contributors to homogenization are the dispersal of gamefish species, most of which are large predators. Alternative explanations relating to lake habitat (e.g., area, phosphorus) or variations in climate have limited explanatory power. Our analysis suggests that human-assisted migration is the primary driver of the observed compositional shifts, homogenizing freshwater fish community among Ontario lakes and generating food webs dominated by gamefish species.},
	language = {en},
	number = {12},
	urldate = {2020-04-23},
	journal = {Global Change Biology},
	author = {Cazelles, Kevin and Bartley, Timothy and Guzzo, Matthew M. and Brice, Marie-Hélène and MacDougall, Andrew S. and Bennett, Joseph R. and Esch, Ellen H. and Kadoya, Taku and Kelly, Jocelyn and Matsuzaki, Shin-ichiro and Nilsson, Karin A. and McCann, Kevin S.},
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14829},
	keywords = {\#nosource, Ontario, angling pressure, climate change, compositional shift, fresh lake fish communities, homogenization, predatory fish},
	pages = {4222--4233},
}

Globally, lake fish communities are being subjected to a range of scale-dependent anthropogenic pressures, from climate change to eutrophication, and from overexploitation to species introductions. As a consequence, the composition of these communities is being reshuffled, in most cases leading to a surge in taxonomic similarity at the regional scale termed homogenization. The drivers of homogenization remain unclear, which may be a reflection of interactions between various environmental changes. In this study, we investigate two potential drivers of the recent changes in the composition of freshwater fish communities: recreational fishing and climate change. Our results, derived from 524 lakes of Ontario, Canada sampled in two periods (1965–1982 and 2008–2012), demonstrate that the main contributors to homogenization are the dispersal of gamefish species, most of which are large predators. Alternative explanations relating to lake habitat (e.g., area, phosphorus) or variations in climate have limited explanatory power. Our analysis suggests that human-assisted migration is the primary driver of the observed compositional shifts, homogenizing freshwater fish community among Ontario lakes and generating food webs dominated by gamefish species.

@article{meyer-jacob_browning_2019,
	title = {The browning and re-browning of lakes: {Divergent} lake-water organic carbon trends linked to acid deposition and climate change},
	volume = {9},
	copyright = {2019 The Author(s)},
	issn = {2045-2322},
	shorttitle = {The browning and re-browning of lakes},
	url = {https://www.nature.com/articles/s41598-019-52912-0},
	doi = {10.1038/s41598-019-52912-0},
	abstract = {Dissolved organic carbon (DOC) concentrations and water colour are increasing in many inland waters across northern Europe and northeastern North America. This inland-water “browning” has profound physical, chemical and biological repercussions for aquatic ecosystems affecting water quality, biological community structures and aquatic productivity. Potential drivers of this “browning” trend are complex and include reductions in atmospheric acid deposition, changes in land use/cover, increased nitrogen deposition and climate change. However, because of the overlapping impacts of these stressors, their relative contributions to DOC dynamics remain unclear, and without appropriate long-term monitoring data, it has not been possible to determine whether the ongoing “browning” is unprecedented or simply a “re-browning” to pre-industrial DOC levels. Here, we demonstrate the long-term impacts of acid deposition and climate change on lake-water DOC concentrations in low and high acid-deposition areas using infrared spectroscopic techniques on {\textasciitilde}200-year-long lake-sediment records from central Canada. We show that acid deposition suppressed naturally higher DOC concentrations during the 20th century, but that a “re-browning” of lakes is now occurring with emissions reductions in formerly high deposition areas. In contrast, in low deposition areas, climate change is forcing lakes towards new ecological states, as lake-water DOC concentrations now often exceed pre-industrial levels.},
	language = {en},
	number = {1},
	urldate = {2020-04-23},
	journal = {Scientific Reports},
	author = {Meyer-Jacob, Carsten and Michelutti, Neal and Paterson, Andrew M. and Cumming, Brian F. and Keller, Wendel (Bill) and Smol, John P.},
	month = nov,
	year = {2019},
	note = {Number: 1
Publisher: Nature Publishing Group},
	keywords = {\#nosource},
	pages = {1--10},
}

Dissolved organic carbon (DOC) concentrations and water colour are increasing in many inland waters across northern Europe and northeastern North America. This inland-water “browning” has profound physical, chemical and biological repercussions for aquatic ecosystems affecting water quality, biological community structures and aquatic productivity. Potential drivers of this “browning” trend are complex and include reductions in atmospheric acid deposition, changes in land use/cover, increased nitrogen deposition and climate change. However, because of the overlapping impacts of these stressors, their relative contributions to DOC dynamics remain unclear, and without appropriate long-term monitoring data, it has not been possible to determine whether the ongoing “browning” is unprecedented or simply a “re-browning” to pre-industrial DOC levels. Here, we demonstrate the long-term impacts of acid deposition and climate change on lake-water DOC concentrations in low and high acid-deposition areas using infrared spectroscopic techniques on ~200-year-long lake-sediment records from central Canada. We show that acid deposition suppressed naturally higher DOC concentrations during the 20th century, but that a “re-browning” of lakes is now occurring with emissions reductions in formerly high deposition areas. In contrast, in low deposition areas, climate change is forcing lakes towards new ecological states, as lake-water DOC concentrations now often exceed pre-industrial levels.

@article{capo_effects_2019,
	title = {Effects of filtration methods and water volume on the quantification of brown trout ({Salmo} trutta) and {Arctic} char ({Salvelinus} alpinus) {eDNA} concentrations via droplet digital {PCR}},
	volume = {2},
	issn = {2637-4943},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/edn3.52},
	doi = {10.1002/edn3.52},
	abstract = {The quantification of the abundance of aquatic organisms via the use of environmental DNA (eDNA) molecules present in water is potentially a useful tool for efficient and noninvasive population monitoring. However, questions remain about the reliability of molecular methods. Among the factors that can hamper the reliability of the eDNA quantification, we investigated the influence of five filtration methods (filter pore size, filter type) and filtered water volume (1 and 2 L) on the total eDNA and the fish eDNA concentrations of two species, brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) from tanks with known number of individuals and biomass. We applied a droplet digital PCR (ddPCR) approach to DNA extracted from water samples collected from two cultivation tanks (each of them containing one of the targeted species). Results showed that the quantification of fish eDNA concentrations of both species varies with filtration methods. More specifically, the 0.45-µm Sterivex enclosed filters were identified to recover the highest eDNA concentrations. Difficulties to filter 2 L water samples were present for small pore size filters (≤0.45 µm) and likely caused by filter clogging. To overcome issues related to filter clogging, common in studies aiming to quantify fish eDNA molecules from water samples, we recommend a procedure involving filtration of multiple 1 L water samples with 0.45-µm enclosed filters, to recover both high quality and high concentrations of eDNA from targeted species, and subsequent processing of independent DNA extracts with the ddPCR method.},
	language = {en},
	number = {2},
	urldate = {2020-03-19},
	journal = {Environmental DNA},
	author = {Capo, Eric and Spong, Göran and Königsson, Helena and Byström, Pär},
	month = nov,
	year = {2019},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/edn3.52},
	keywords = {\#nosource, Arctic char, brown trout, ddPCR assays, environmental DNA, lakes},
	pages = {152--160},
}

The quantification of the abundance of aquatic organisms via the use of environmental DNA (eDNA) molecules present in water is potentially a useful tool for efficient and noninvasive population monitoring. However, questions remain about the reliability of molecular methods. Among the factors that can hamper the reliability of the eDNA quantification, we investigated the influence of five filtration methods (filter pore size, filter type) and filtered water volume (1 and 2 L) on the total eDNA and the fish eDNA concentrations of two species, brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) from tanks with known number of individuals and biomass. We applied a droplet digital PCR (ddPCR) approach to DNA extracted from water samples collected from two cultivation tanks (each of them containing one of the targeted species). Results showed that the quantification of fish eDNA concentrations of both species varies with filtration methods. More specifically, the 0.45-µm Sterivex enclosed filters were identified to recover the highest eDNA concentrations. Difficulties to filter 2 L water samples were present for small pore size filters (≤0.45 µm) and likely caused by filter clogging. To overcome issues related to filter clogging, common in studies aiming to quantify fish eDNA molecules from water samples, we recommend a procedure involving filtration of multiple 1 L water samples with 0.45-µm enclosed filters, to recover both high quality and high concentrations of eDNA from targeted species, and subsequent processing of independent DNA extracts with the ddPCR method.

@article{block_unique_2019,
	title = {The unique methodological challenges of winter limnology},
	volume = {17},
	copyright = {© 2018 Association for the Sciences of Limnology and Oceanography},
	issn = {1541-5856},
	url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lom3.10295},
	doi = {10.1002/lom3.10295},
	abstract = {Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0°C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period.},
	language = {en},
	number = {1},
	urldate = {2019-02-21},
	journal = {Limnology and Oceanography: Methods},
	author = {Block, Benjamin D. and Denfeld, Blaize A. and Stockwell, Jason D. and Flaim, Giovanna and Grossart, Hans-Peter F. and Knoll, Lesley B. and Maier, Dominique B. and North, Rebecca L. and Rautio, Milla and Rusak, James A. and Sadro, Steve and Weyhenmeyer, Gesa A. and Bramburger, Andrew J. and Branstrator, Donn K. and Salonen, Kalevi and Hampton, Stephanie E.},
	year = {2019},
	keywords = {\#nosource},
	pages = {42--57},
}

Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0°C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period.

@article{trager_belowground_2019,
	title = {Belowground plant parts are crucial for comprehensively estimating total plant richness in herbaceous and woody habitats},
	volume = {100},
	copyright = {© 2018 by the Ecological Society of America},
	issn = {1939-9170},
	url = {http://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2575},
	doi = {10.1002/ecy.2575},
	abstract = {Most studies consider aboveground plant species richness as a representative biodiversity measure. This approach inevitably assumes that the partitioning of total plant species richness into above- and belowground components is constant or at least consistent within and across vegetation types. However, with studies considering belowground plant richness still scarce and completely absent along vegetation gradients, this assumption lacks experimental support. Novel DNA sequencing techniques allow economical, high-throughput species identification of belowground environmental samples, enabling the measurement of the contributions of both above- and belowground plant components to total plant richness. We investigated above- and belowground plant species richness in four vegetation types (birch forest, heath, low alpine tundra, high alpine tundra) at the scale of herbaceous plant neighborhoods (dm) using 454 sequencing of the chloroplast trnL (UAA) intron to determine the plant species richness of environmental root samples and combined it with aboveground data from vegetation surveys to obtain total plant species richness. We correlated the measured plant species richness components with each other and with their respective plant biomass components within and across vegetation types. Total plant species richness exceeded aboveground richness twice on average and by as much as three times in low alpine tundra, indicating that a significant fraction of belowground plant richness cannot be recorded aboveground. More importantly, no consistent relationship among richness components (above- and belowground) was found within or across vegetation types, indicating that aboveground richness alone cannot predict total plant richness in contrasting vegetation types. Finally, no consistent relationship between plant richness and the corresponding biomass component was found. Our results clearly show that aboveground plant richness alone is a poor estimator of total plant species richness within and across different vegetation types. Consequently, it is crucial to account for belowground plant richness in future plant ecological studies in order to validate currently accepted plant richness patterns, as well as to measure potential changes in plant community composition in a changing environment.},
	language = {en},
	number = {2},
	urldate = {2019-02-21},
	journal = {Ecology},
	author = {Träger, Sabrina and Öpik, Maarja and Vasar, Martti and Wilson, Scott D.},
	year = {2019},
	keywords = {\#nosource, 454 sequencing, above- and belowground plant richness, next-generation sequencing, plant biomass, root identification, trnL (UAA) intron, vegetation surveys},
	pages = {e02575},
}

Most studies consider aboveground plant species richness as a representative biodiversity measure. This approach inevitably assumes that the partitioning of total plant species richness into above- and belowground components is constant or at least consistent within and across vegetation types. However, with studies considering belowground plant richness still scarce and completely absent along vegetation gradients, this assumption lacks experimental support. Novel DNA sequencing techniques allow economical, high-throughput species identification of belowground environmental samples, enabling the measurement of the contributions of both above- and belowground plant components to total plant richness. We investigated above- and belowground plant species richness in four vegetation types (birch forest, heath, low alpine tundra, high alpine tundra) at the scale of herbaceous plant neighborhoods (dm) using 454 sequencing of the chloroplast trnL (UAA) intron to determine the plant species richness of environmental root samples and combined it with aboveground data from vegetation surveys to obtain total plant species richness. We correlated the measured plant species richness components with each other and with their respective plant biomass components within and across vegetation types. Total plant species richness exceeded aboveground richness twice on average and by as much as three times in low alpine tundra, indicating that a significant fraction of belowground plant richness cannot be recorded aboveground. More importantly, no consistent relationship among richness components (above- and belowground) was found within or across vegetation types, indicating that aboveground richness alone cannot predict total plant richness in contrasting vegetation types. Finally, no consistent relationship between plant richness and the corresponding biomass component was found. Our results clearly show that aboveground plant richness alone is a poor estimator of total plant species richness within and across different vegetation types. Consequently, it is crucial to account for belowground plant richness in future plant ecological studies in order to validate currently accepted plant richness patterns, as well as to measure potential changes in plant community composition in a changing environment.

@article{mccallum_investigating_2019,
	title = {Investigating tissue bioconcentration and the behavioural effects of two pharmaceutical pollutants on sea trout ({Salmo} trutta) in the laboratory and field},
	volume = {207},
	issn = {0166-445X},
	url = {http://www.sciencedirect.com/science/article/pii/S0166445X18307173},
	doi = {10.1016/j.aquatox.2018.11.028},
	abstract = {Pharmaceuticals entering aquatic ecosystems via wastewater effluents are of increasing concern for wild animals. Because some pharmaceuticals are designed to modulate human behaviour, measuring the impacts of exposure to pharmaceuticals on fish behaviour has become a valuable endpoint. While laboratory studies have shown that pharmaceuticals can affect fish behaviour, there is a lack of understanding if behaviour is similarly affected in natural environments. Here, we exposed sea trout (Salmo trutta) smolts to two concentrations of two pharmaceutical pollutants often detected in surface waters: temazepam (a benzodiazepine, anxiolytic) or irbesartan (an angiotensin II receptor blocker, anti-hypertensive). We tested the hypothesis that changes to behavioural traits (anxiety and activity) measured in laboratory trials following exposure are predictive of behaviour in the natural environment (downstream migration). Measures of anxiety and activity in the laboratory assay did not vary with temazepam treatment, but temazepam-exposed fish began migrating faster in the field. Activity in the laboratory assay did predict overall migration speed in the field. In contrast to temazepam, we found that irbesartan exposure did not affect behaviour in the laboratory, field, or the relationship between the two endpoints. However, irbesartan was also not readily taken up into fish tissue (i.e. below detection levels in the muscle tissue), while temazepam bioconcentrated (bioconcentration factor 7.68) rapidly (t1/2 {\textless} 24 h). Our findings add to a growing literature showing that benzodiazepine pollutants can modulate fish behaviour and that laboratory assays may be less sensitive at detecting the effects of pollutants compared to measuring effects in natural settings. Therefore, we underscore the importance of measuring behavioural effects in the natural environment.},
	urldate = {2019-02-21},
	journal = {Aquatic Toxicology},
	author = {McCallum, Erin S. and Sundelin, Anna and Fick, Jerker and Alanärä, Anders and Klaminder, Jonatan and Hellström, Gustav and Brodin, Tomas},
	month = feb,
	year = {2019},
	keywords = {\#nosource, Bioconcentration, Ecotoxicology, In situ, Scototaxis, Steady-state},
	pages = {170--178},
}

Pharmaceuticals entering aquatic ecosystems via wastewater effluents are of increasing concern for wild animals. Because some pharmaceuticals are designed to modulate human behaviour, measuring the impacts of exposure to pharmaceuticals on fish behaviour has become a valuable endpoint. While laboratory studies have shown that pharmaceuticals can affect fish behaviour, there is a lack of understanding if behaviour is similarly affected in natural environments. Here, we exposed sea trout (Salmo trutta) smolts to two concentrations of two pharmaceutical pollutants often detected in surface waters: temazepam (a benzodiazepine, anxiolytic) or irbesartan (an angiotensin II receptor blocker, anti-hypertensive). We tested the hypothesis that changes to behavioural traits (anxiety and activity) measured in laboratory trials following exposure are predictive of behaviour in the natural environment (downstream migration). Measures of anxiety and activity in the laboratory assay did not vary with temazepam treatment, but temazepam-exposed fish began migrating faster in the field. Activity in the laboratory assay did predict overall migration speed in the field. In contrast to temazepam, we found that irbesartan exposure did not affect behaviour in the laboratory, field, or the relationship between the two endpoints. However, irbesartan was also not readily taken up into fish tissue (i.e. below detection levels in the muscle tissue), while temazepam bioconcentrated (bioconcentration factor 7.68) rapidly (t1/2 \textless 24 h). Our findings add to a growing literature showing that benzodiazepine pollutants can modulate fish behaviour and that laboratory assays may be less sensitive at detecting the effects of pollutants compared to measuring effects in natural settings. Therefore, we underscore the importance of measuring behavioural effects in the natural environment.

@article{metcalfe_ecological_2019,
	title = {Ecological stoichiometry and nutrient partitioning in two insect herbivores responsible for large-scale forest disturbance in the {Fennoscandian} subarctic},
	volume = {44},
	copyright = {© 2018 The Royal Entomological Society},
	issn = {1365-2311},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/een.12679},
	doi = {10.1111/een.12679},
	abstract = {1. Outbreaks of herbivorous insects can have large impacts on regional soil carbon (C) storage and nutrient cycling. In northernmost Europe, population outbreaks of several geometrid moth species regularly cause large-scale defoliation in subarctic birch forests. An improved understanding is required of how leaf C and nutrients are processed after ingestion by herbivores and what this means for the quantity and quality of different materials produced (frass, bodies). 2. In this study, larvae of two geometrid species responsible for major outbreaks (Epirrita autumnata and Operophtera brumata) were raised on exclusive diets of Betula pubescens var. czerepanovii (N. I. Orlova) Hämet Ahti and two other abundant understorey species (Betula nana, Vaccinium myrtillus). The quantities of C, nitrogen (N) and phosphorus (P) ingested and allocated to frass, bodies and (in the case of C) respired were recorded. 3. Overall, 23\%, 70\% and 48\% of ingested C, N and P were allocated to bodies, respectively, rather than frass and (in the case of C) respiration. Operophtera brumata consistently maintained more constant body stoichiometric ratios of C, N and P than did E. autumnata, across the wide variation in physico-chemical properties of plant diet supplied. 4. These observed differences and similarities on C and nutrient processing may improve researchers' ability to predict the amount and stoichiometry of frass and bodies generated after geometrid outbreaks.},
	language = {en},
	urldate = {2018-10-25},
	journal = {Ecological Entomology},
	author = {Metcalfe, Daniel B. and Cherif, Mehdi and Jepsen, Jane U. and Vindstad, Ole Petter L. and Kristensen, Jeppe Å and Belsing, Ulrika},
	year = {2019},
	keywords = {\#nosource, Consumer-driven nutrient recycling, ecological stoichiometry, geometrid moth, homeostasis, stable isotope, subarctic birch forest},
	pages = {118--128},
}

1. Outbreaks of herbivorous insects can have large impacts on regional soil carbon (C) storage and nutrient cycling. In northernmost Europe, population outbreaks of several geometrid moth species regularly cause large-scale defoliation in subarctic birch forests. An improved understanding is required of how leaf C and nutrients are processed after ingestion by herbivores and what this means for the quantity and quality of different materials produced (frass, bodies). 2. In this study, larvae of two geometrid species responsible for major outbreaks (Epirrita autumnata and Operophtera brumata) were raised on exclusive diets of Betula pubescens var. czerepanovii (N. I. Orlova) Hämet Ahti and two other abundant understorey species (Betula nana, Vaccinium myrtillus). The quantities of C, nitrogen (N) and phosphorus (P) ingested and allocated to frass, bodies and (in the case of C) respired were recorded. 3. Overall, 23%, 70% and 48% of ingested C, N and P were allocated to bodies, respectively, rather than frass and (in the case of C) respiration. Operophtera brumata consistently maintained more constant body stoichiometric ratios of C, N and P than did E. autumnata, across the wide variation in physico-chemical properties of plant diet supplied. 4. These observed differences and similarities on C and nutrient processing may improve researchers' ability to predict the amount and stoichiometry of frass and bodies generated after geometrid outbreaks.

@article{stark_contrasting_2019,
	title = {Contrasting vegetation states do not diverge in soil organic matter storage: evidence from historical sites in tundra},
	volume = {0},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {1939-9170},
	shorttitle = {Contrasting vegetation states do not diverge in soil organic matter storage},
	url = {http://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2731},
	doi = {10.1002/ecy.2731},
	abstract = {Ecosystems where severe disturbance has induced permanent shifts in vegetation and soil processes may represent alternative stable states. To date, little is known on how long-lasting changes in soil processes are following such disturbances, and how the changes in plant and soil processes between the alternative states eventually manifest themselves in soil organic matter (SOM) storage. Here, we analyzed plant density, the shrub:forb –ratio, microbial respiration, extracellular enzyme activities and SOM stocks in soils of subarctic tundra and historical milking grounds, where reindeer herding induced a vegetation transition from deciduous shrubs to graminoids several centuries earlier but were abandoned a century ago. This provides the possibility to compare sites with similar topography, but highly contrasting vegetation for centuries. We found that enzymatic activities and N:P stoichiometry differed between control and disturbed sites, confirming that culturally induced vegetation shifts exert lasting impacts on tundra soil processes. Transition zones, where shrubs had encroached into the historical milking grounds during the past 50 years, indicated that microbial activities for N and P acquisition changed more rapidly along a vegetation shift than those for microbial C acquisition. Although plant and soil processes differed between control and disturbed sites, we found no effect of historical vegetation transition on SOM stock. Across the study sites, soil SOM stocks were correlated with total plant density but not with the shrub:forb ratio. Our finding that SOM stock was insensitive to a centennial difference in plant community composition suggests that, as such, grazing-induced alternative vegetation states might not necessarily differ in SOM sequestration. This article is protected by copyright. All rights reserved.},
	language = {en},
	number = {0},
	urldate = {2019-04-23},
	journal = {Ecology},
	author = {Stark, Sari and Egelkraut, Dagmar and Aronsson, Kjell-Åke and Olofsson, Johan},
	year = {2019},
	keywords = {\#nosource, cultural landscape, extracellular enzymes, historical ecology, reindeer, soil carbon stock, tundra},
	pages = {e02731},
}

Ecosystems where severe disturbance has induced permanent shifts in vegetation and soil processes may represent alternative stable states. To date, little is known on how long-lasting changes in soil processes are following such disturbances, and how the changes in plant and soil processes between the alternative states eventually manifest themselves in soil organic matter (SOM) storage. Here, we analyzed plant density, the shrub:forb –ratio, microbial respiration, extracellular enzyme activities and SOM stocks in soils of subarctic tundra and historical milking grounds, where reindeer herding induced a vegetation transition from deciduous shrubs to graminoids several centuries earlier but were abandoned a century ago. This provides the possibility to compare sites with similar topography, but highly contrasting vegetation for centuries. We found that enzymatic activities and N:P stoichiometry differed between control and disturbed sites, confirming that culturally induced vegetation shifts exert lasting impacts on tundra soil processes. Transition zones, where shrubs had encroached into the historical milking grounds during the past 50 years, indicated that microbial activities for N and P acquisition changed more rapidly along a vegetation shift than those for microbial C acquisition. Although plant and soil processes differed between control and disturbed sites, we found no effect of historical vegetation transition on SOM stock. Across the study sites, soil SOM stocks were correlated with total plant density but not with the shrub:forb ratio. Our finding that SOM stock was insensitive to a centennial difference in plant community composition suggests that, as such, grazing-induced alternative vegetation states might not necessarily differ in SOM sequestration. This article is protected by copyright. All rights reserved.

@article{vorobyev_biogeochemistry_2019,
	title = {Biogeochemistry of dissolved carbon, major and trace elements during spring flood periods on the {Ob} {River}},
	volume = {0},
	copyright = {This article is protected by copyright. All rights reserved.},
	issn = {1099-1085},
	url = {http://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.13424},
	doi = {10.1002/hyp.13424},
	abstract = {Detailed knowledge of the flood period of Arctic rivers remains one of the few factors impeding rigorous prediction of the effect of climate change on carbon and related element flux from the land to the Arctic Ocean. In order to test the temporal and spatial variability of element concentration in the Ob River (western Siberia) water during flood period, and to quantify the contribution of spring flood period to the annual element export, we sampled the main channel year round in 2014-2017 for dissolved C, major and trace element concentrations. We revealed high stability (ca ≤ 10\% relative variation) of dissolved C, major and trace element concentrations in the Ob River during spring flood period over a 1 km section of the river channel and over 3 days continuous monitoring (3 h frequency). We identified two groups of elements with contrasting relationship to discharge: (1) DIC and soluble elements (Cl, SO4, Li, B, Na, Mg, Ca, P, V, Cr, Mn, As, Rb, Sr, Mo, Ba, W, U) negatively correlated (p {\textless} 0.05) with discharge and exhibited minimal concentrations during spring flood and autumn high flow, and (2) DOC and particle-reactive elements (Al, Fe, Ti, Y, Zr, Nb, Cs, REEs, Hf, Tl, Pb, Th), some nutrients (K) and metalloids (Ge, Sb, Te), positively correlated (p {\textless} 0.05) with discharge and showed highest concentrations during spring flood. We attribute the decreased concentration of soluble elements with discharge to dilution by groundwater feeding, and increased concentration of DOC and particle-reactive metals with discharge to leaching from surface soil, plant litter and suspended particles. Overall, the present study provides first order assessment of fluxes of major and trace elements in the middle course of the Ob River and reveals their high temporal and spatial stability as well as characterizes the mechanism of river water chemical composition acquisition.},
	language = {en},
	number = {0},
	urldate = {2019-03-22},
	journal = {Hydrological Processes},
	author = {Vorobyev, S. N. and Pokrovsky, O. S. and Kolesnichenko, L. G. and Manasypov, R. M. and Shirokova, L. S. and Karlsson, J. and Kirpotin, S. N.},
	year = {2019},
	keywords = {\#nosource, Siberia, baseflow, colloids, flood, lakes, metals, organic carbon, riparian zone, rivers, underground waters},
	pages = {0},
}

Detailed knowledge of the flood period of Arctic rivers remains one of the few factors impeding rigorous prediction of the effect of climate change on carbon and related element flux from the land to the Arctic Ocean. In order to test the temporal and spatial variability of element concentration in the Ob River (western Siberia) water during flood period, and to quantify the contribution of spring flood period to the annual element export, we sampled the main channel year round in 2014-2017 for dissolved C, major and trace element concentrations. We revealed high stability (ca ≤ 10% relative variation) of dissolved C, major and trace element concentrations in the Ob River during spring flood period over a 1 km section of the river channel and over 3 days continuous monitoring (3 h frequency). We identified two groups of elements with contrasting relationship to discharge: (1) DIC and soluble elements (Cl, SO4, Li, B, Na, Mg, Ca, P, V, Cr, Mn, As, Rb, Sr, Mo, Ba, W, U) negatively correlated (p \textless 0.05) with discharge and exhibited minimal concentrations during spring flood and autumn high flow, and (2) DOC and particle-reactive elements (Al, Fe, Ti, Y, Zr, Nb, Cs, REEs, Hf, Tl, Pb, Th), some nutrients (K) and metalloids (Ge, Sb, Te), positively correlated (p \textless 0.05) with discharge and showed highest concentrations during spring flood. We attribute the decreased concentration of soluble elements with discharge to dilution by groundwater feeding, and increased concentration of DOC and particle-reactive metals with discharge to leaching from surface soil, plant litter and suspended particles. Overall, the present study provides first order assessment of fluxes of major and trace elements in the middle course of the Ob River and reveals their high temporal and spatial stability as well as characterizes the mechanism of river water chemical composition acquisition.

@article{sarneel_alternative_2019,
	title = {Alternative transient states and slow plant community responses after changed flooding regimes},
	volume = {25},
	copyright = {© 2019 The Authors. Global Change Biology Published by John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {http://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14569},
	doi = {10.1111/gcb.14569},
	abstract = {Climate change will have large consequences for flooding frequencies in freshwater systems. In interaction with anthropogenic activities (flow regulation, channel restoration and catchment land-use) this will both increase flooding and drought across the world. Like in many other ecosystems facing changed environmental conditions, it remains difficult to predict the rate and trajectory of vegetation responses to changed conditions. Given that critical ecosystem services (e.g. bank stabilization, carbon subsidies to aquatic communities or water purification) depend on riparian vegetation composition, it is important to understand how and how fast riparian vegetation responds to changing flooding regimes. We studied vegetation changes over 19 growing seasons in turfs that were transplanted in a full-factorial design between three riparian elevations with different flooding frequencies. We found that (a) some transplanted communities may have developed into an alternative stable state and were still different from the target community, and (b) pathways of vegetation change were highly directional but alternative trajectories did occur, (c) changes were rather linear but faster when flooding frequencies increased than when they decreased, and (d) we observed fastest changes in turfs when proxies for mortality and colonization were highest. These results provide rare examples of alternative transient trajectories and stable states under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world.},
	language = {en},
	number = {4},
	urldate = {2019-04-05},
	journal = {Global Change Biology},
	author = {Sarneel, Judith M. and Hefting, Mariet M. and Kowalchuk, George A. and Nilsson, Christer and Velden, Merit Van der and Visser, Eric J. W. and Voesenek, Laurentius A. C. J. and Jansson, Roland},
	year = {2019},
	keywords = {\#nosource, alternative stable states, drought events, flood regime change, hydrological alterations, hysteresis, riparian vegetation, river restoration, species traits},
	pages = {1358--1367},
}

Climate change will have large consequences for flooding frequencies in freshwater systems. In interaction with anthropogenic activities (flow regulation, channel restoration and catchment land-use) this will both increase flooding and drought across the world. Like in many other ecosystems facing changed environmental conditions, it remains difficult to predict the rate and trajectory of vegetation responses to changed conditions. Given that critical ecosystem services (e.g. bank stabilization, carbon subsidies to aquatic communities or water purification) depend on riparian vegetation composition, it is important to understand how and how fast riparian vegetation responds to changing flooding regimes. We studied vegetation changes over 19 growing seasons in turfs that were transplanted in a full-factorial design between three riparian elevations with different flooding frequencies. We found that (a) some transplanted communities may have developed into an alternative stable state and were still different from the target community, and (b) pathways of vegetation change were highly directional but alternative trajectories did occur, (c) changes were rather linear but faster when flooding frequencies increased than when they decreased, and (d) we observed fastest changes in turfs when proxies for mortality and colonization were highest. These results provide rare examples of alternative transient trajectories and stable states under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world.

@article{ylanne_consequences_2018,
	title = {Consequences of grazer-induced vegetation transitions on ecosystem carbon storage in the tundra},
	volume = {32},
	copyright = {© 2017 The Authors. Functional Ecology © 2017 British Ecological Society},
	issn = {1365-2435},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13029},
	doi = {10.1111/1365-2435.13029},
	abstract = {Large herbivores can control plant community composition and, under certain conditions, even induce vegetation shifts to alternative ecosystem states. As different plant assemblages maintain contrasting carbon (C) cycling patterns, herbivores have the potential to alter C sequestration at regional scales. Their influence is of particular interest in the Arctic tundra, where a large share of the world's soil C reservoir is stored. We assessed the influence of grazing mammals on tundra vegetation and C stocks by resampling two sites located along pasture rotation fences in northern Norway. These fences have separated lightly grazed areas from heavily grazed areas (in close proximity to the fences) and moderately grazed areas (further away from the fences) for the past 50 years. Fourteen years earlier, the lightly and moderately grazed areas were dominated by dwarf shrubs, whereas heavy grazing had promoted the establishment of graminoid-dominated vegetation. Since then, both reindeer densities and temperatures have increased, and more time has passed for transient dynamics to be expressed. We expected that the vegetation and C stocks would have changed under all grazing intensities, but not necessarily in the same way. At the site where relative reindeer numbers and trampling intensity had increased the most, graminoid-dominated vegetation was now also found in the moderately grazed area. At the other site, the dominant vegetation types under all grazing intensities were the same as 14 years earlier. We show that the heavily grazed, graminoid-dominated areas stored less C above-ground than the lightly grazed, shrub-dominated areas. Yet, the below-ground consequences of grazing-induced grassification varied between the sites: Grazing did not alter organic soil C stocks at the site where both evergreen and deciduous shrubs were abundant in the lightly grazed area, whereas heavy grazing increased organic soil C stocks at the site where the deciduous shrub Betula nana was dominant. Our results indicate that, despite the negative impacts of grazers on above-ground C storage, their impact on below-ground C may even be positive. We suggest that the site-specific responses of organic soil C stocks to grazing could be explained by the differences in vegetation under light grazing. This would imply that the replacement of deciduous shrubs by graminoids, as a consequence of grazing could be beneficial for C sequestration in tundra soils. A plain language summary is available for this article.},
	language = {en},
	number = {4},
	urldate = {2024-03-27},
	journal = {Functional Ecology},
	author = {Ylänne, Henni and Olofsson, Johan and Oksanen, Lauri and Stark, Sari},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.13029},
	keywords = {\#nosource, Carbon stocks, Grazing, Herbivory, Plant functional types, Plant–soil interactions, Rangifer tarandus, Reindeer, Soil carbon, carbon stocks, grazing, herbivory, plant functional types, plant–soil interactions, reindeer, soil carbon},
	pages = {1091--1102},
}

Large herbivores can control plant community composition and, under certain conditions, even induce vegetation shifts to alternative ecosystem states. As different plant assemblages maintain contrasting carbon (C) cycling patterns, herbivores have the potential to alter C sequestration at regional scales. Their influence is of particular interest in the Arctic tundra, where a large share of the world's soil C reservoir is stored. We assessed the influence of grazing mammals on tundra vegetation and C stocks by resampling two sites located along pasture rotation fences in northern Norway. These fences have separated lightly grazed areas from heavily grazed areas (in close proximity to the fences) and moderately grazed areas (further away from the fences) for the past 50 years. Fourteen years earlier, the lightly and moderately grazed areas were dominated by dwarf shrubs, whereas heavy grazing had promoted the establishment of graminoid-dominated vegetation. Since then, both reindeer densities and temperatures have increased, and more time has passed for transient dynamics to be expressed. We expected that the vegetation and C stocks would have changed under all grazing intensities, but not necessarily in the same way. At the site where relative reindeer numbers and trampling intensity had increased the most, graminoid-dominated vegetation was now also found in the moderately grazed area. At the other site, the dominant vegetation types under all grazing intensities were the same as 14 years earlier. We show that the heavily grazed, graminoid-dominated areas stored less C above-ground than the lightly grazed, shrub-dominated areas. Yet, the below-ground consequences of grazing-induced grassification varied between the sites: Grazing did not alter organic soil C stocks at the site where both evergreen and deciduous shrubs were abundant in the lightly grazed area, whereas heavy grazing increased organic soil C stocks at the site where the deciduous shrub Betula nana was dominant. Our results indicate that, despite the negative impacts of grazers on above-ground C storage, their impact on below-ground C may even be positive. We suggest that the site-specific responses of organic soil C stocks to grazing could be explained by the differences in vegetation under light grazing. This would imply that the replacement of deciduous shrubs by graminoids, as a consequence of grazing could be beneficial for C sequestration in tundra soils. A plain language summary is available for this article.

@article{wackett_human-mediated_2018,
	title = {Human-mediated introduction of geoengineering earthworms in the {Fennoscandian} arctic},
	volume = {20},
	issn = {1573-1464},
	url = {https://doi.org/10.1007/s10530-017-1642-7},
	doi = {10.1007/s10530-017-1642-7},
	abstract = {It is now well established that European earthworms are re-shaping formerly glaciated forests in North America with dramatic ecological consequences. However, few have considered the potential invasiveness of this species assemblage in the European arctic. Here we argue that some earthworm species (Lumbricus rubellus, Lumbricus terrestris and Aporrectodea sp.) with great geomorphological impact (geoengineering species) are non-native and invasive in the Fennoscandian arctic birch forests, where they have been introduced by agrarian settlers and most recently through recreational fishing and gardening. Our exploratory surveys indicate no obvious historical dispersal mechanism that can explain early arrival of these earthworms into the Fennoscandian arctic: that is, these species do not appear to establish naturally along coastlines mimicking conditions following deglaciation in Fennoscandia, nor were they spread by early native (Sami) cultures. The importance of anthropogenic sources and the invasive characteristics of L. rubellus and Aporrectodea sp. in the arctic is evident from their radiation outwards from abandoned farms and modern cabin lawns into adjacent arctic birch forests. They appear to outcompete previously established litter-dwelling earthworm species (i.e. Dendrobaena octaedra) that likely colonized the Fennoscandian landscape rapidly following deglaciation via hydrochory and/or dispersal by early Sami settlements. The high geoengineering earthworm biomasses, their recognized ecological impact in other formerly glaciated environments, and their persistence once established leads us to suggest that geoengineering earthworms may pose a potent threat to some of the most remote and protected arctic environments in northern Europe.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Biological Invasions},
	author = {Wackett, Adrian A. and Yoo, Kyungsoo and Olofsson, Johan and Klaminder, Jonatan},
	month = jun,
	year = {2018},
	keywords = {\#nosource, Arctic, Earthworm invasion, Hydrochory, Land use, Lumbricidae},
	pages = {1377--1386},
}

It is now well established that European earthworms are re-shaping formerly glaciated forests in North America with dramatic ecological consequences. However, few have considered the potential invasiveness of this species assemblage in the European arctic. Here we argue that some earthworm species (Lumbricus rubellus, Lumbricus terrestris and Aporrectodea sp.) with great geomorphological impact (geoengineering species) are non-native and invasive in the Fennoscandian arctic birch forests, where they have been introduced by agrarian settlers and most recently through recreational fishing and gardening. Our exploratory surveys indicate no obvious historical dispersal mechanism that can explain early arrival of these earthworms into the Fennoscandian arctic: that is, these species do not appear to establish naturally along coastlines mimicking conditions following deglaciation in Fennoscandia, nor were they spread by early native (Sami) cultures. The importance of anthropogenic sources and the invasive characteristics of L. rubellus and Aporrectodea sp. in the arctic is evident from their radiation outwards from abandoned farms and modern cabin lawns into adjacent arctic birch forests. They appear to outcompete previously established litter-dwelling earthworm species (i.e. Dendrobaena octaedra) that likely colonized the Fennoscandian landscape rapidly following deglaciation via hydrochory and/or dispersal by early Sami settlements. The high geoengineering earthworm biomasses, their recognized ecological impact in other formerly glaciated environments, and their persistence once established leads us to suggest that geoengineering earthworms may pose a potent threat to some of the most remote and protected arctic environments in northern Europe.

@article{rivera_vasconcelos_effects_2018,
	title = {Effects of {Terrestrial} {Organic} {Matter} on {Aquatic} {Primary} {Production} as {Mediated} by {Pelagic}–{Benthic} {Resource} {Fluxes}},
	volume = {21},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-017-0217-x},
	doi = {10.1007/s10021-017-0217-x},
	abstract = {Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a substantial contribution of a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment–water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the relative contributions of benthic and pelagic habitats to total primary production. These results are particularly relevant for shallow northern lakes, which are projected to receive increased tDOM runoff.},
	language = {en},
	number = {6},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Rivera Vasconcelos, Francisco and Diehl, Sebastian and Rodríguez, Patricia and Karlsson, Jan and Byström, Pär},
	month = sep,
	year = {2018},
	keywords = {\#nosource, allochthonous input, benthic, brownification, dissolved organic matter, light, nutrients, pelagic, piecewise SEM, resource competition, spatial subsidy, warming},
	pages = {1255--1268},
}

Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a substantial contribution of a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment–water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the relative contributions of benthic and pelagic habitats to total primary production. These results are particularly relevant for shallow northern lakes, which are projected to receive increased tDOM runoff.

@article{sponseller_headwater_2018,
	title = {Headwater {Mires} {Constitute} a {Major} {Source} of {Nitrogen} ({N}) to {Surface} {Waters} in the {Boreal} {Landscape}},
	volume = {21},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-017-0133-0},
	doi = {10.1007/s10021-017-0133-0},
	abstract = {Nutrient exports from soils have important implications for long-term patterns of nutrient limitation on land and resource delivery to aquatic environments. While plant–soil systems are notably efficient at retaining limiting nutrients, spatial and temporal mismatches in resource supply and demand may create opportunities for hydrologic losses to occur. Spatial mismatches may be particularly important in peat-forming landscapes, where the development of a two-layer vertical structure can isolate plant communities on the surface from resource pools that accumulate at depth. Our objectives were to test this idea in northern Sweden, where nitrogen (N) limitation of terrestrial plants is widespread, and where peat-forming, mire ecosystems are dominant features of the landscape. We quantified vertical patterns of N chemistry in a minerogenic mire, estimated the seasonal and annual hydrologic export of organic and inorganic N from this system, and evaluated the broader influence of mire cover on N chemistry across a stream network. Relatively high concentrations of ammonium (up to 2 mg l−1) were observed in groundwater several meters below the peat surface, and N was routed to the outlet stream along deep, preferential flowpaths. Areal estimates of inorganic N export from the mire were several times greater than from an adjacent, forested catchment, with markedly higher loss rates during the growing season, when plant N demand is ostensibly greatest. At broader scales, mire cover was positively correlated with long-term concentrations of inorganic and organic N in streams across the drainage network. This study provides an example of how mire formation and peat accumulation can create broad-scale heterogeneity in nutrient supply and demand across boreal landscapes. This mismatch allows for hydrologic losses of reactive N that are independent of annual plant demand and potentially important to receiving lakes and streams.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Sponseller, Ryan A. and Blackburn, M. and Nilsson, M. B. and Laudon, H.},
	month = jan,
	year = {2018},
	keywords = {\#nosource, boreal, mire, nitrogen, peat, peatlands, watershed biogeochemistry},
	pages = {31--44},
}

Nutrient exports from soils have important implications for long-term patterns of nutrient limitation on land and resource delivery to aquatic environments. While plant–soil systems are notably efficient at retaining limiting nutrients, spatial and temporal mismatches in resource supply and demand may create opportunities for hydrologic losses to occur. Spatial mismatches may be particularly important in peat-forming landscapes, where the development of a two-layer vertical structure can isolate plant communities on the surface from resource pools that accumulate at depth. Our objectives were to test this idea in northern Sweden, where nitrogen (N) limitation of terrestrial plants is widespread, and where peat-forming, mire ecosystems are dominant features of the landscape. We quantified vertical patterns of N chemistry in a minerogenic mire, estimated the seasonal and annual hydrologic export of organic and inorganic N from this system, and evaluated the broader influence of mire cover on N chemistry across a stream network. Relatively high concentrations of ammonium (up to 2 mg l−1) were observed in groundwater several meters below the peat surface, and N was routed to the outlet stream along deep, preferential flowpaths. Areal estimates of inorganic N export from the mire were several times greater than from an adjacent, forested catchment, with markedly higher loss rates during the growing season, when plant N demand is ostensibly greatest. At broader scales, mire cover was positively correlated with long-term concentrations of inorganic and organic N in streams across the drainage network. This study provides an example of how mire formation and peat accumulation can create broad-scale heterogeneity in nutrient supply and demand across boreal landscapes. This mismatch allows for hydrologic losses of reactive N that are independent of annual plant demand and potentially important to receiving lakes and streams.

@article{serikova_high_2018,
	title = {High riverine {CO2} emissions at the permafrost boundary of {Western} {Siberia}},
	volume = {11},
	copyright = {2018 The Author(s)},
	issn = {1752-0908},
	url = {https://www.nature.com/articles/s41561-018-0218-1},
	doi = {10.1038/s41561-018-0218-1},
	abstract = {The fate of the vast stocks of organic carbon stored in permafrost of the Western Siberian Lowland, the world’s largest peatland, is uncertain. Specifically, the amount of greenhouse gas emissions from rivers in the region is unknown. Here we present estimates of annual CO2 emissions from 58 rivers across all permafrost zones of the Western Siberian Lowland, between 56 and 67° N. We find that emissions peak at the permafrost boundary, and decrease where permafrost is more prevalent and in colder climatic conditions. River CO2 emissions were high, and on average two times greater than downstream carbon export. We suggest that high emissions and emission/export ratios are a result of warm temperatures and the long transit times of river water. We show that rivers in the Western Siberian Lowland play an important role in the carbon cycle by degassing terrestrial carbon before its transport to the Arctic Ocean, and suggest that changes in both temperature and precipitation are important for understanding and predicting high-latitude river CO2 emissions in a changing climate.},
	language = {en},
	number = {11},
	urldate = {2024-03-27},
	journal = {Nature Geoscience},
	author = {Serikova, S. and Pokrovsky, O. S. and Ala-Aho, P. and Kazantsev, V. and Kirpotin, S. N. and Kopysov, S. G. and Krickov, I. V. and Laudon, H. and Manasypov, R. M. and Shirokova, L. S. and Soulsby, C. and Tetzlaff, D. and Karlsson, J.},
	month = nov,
	year = {2018},
	note = {Publisher: Nature Publishing Group},
	keywords = {\#nosource, Carbon cycle, Climate-change impacts, Limnology},
	pages = {825--829},
}

The fate of the vast stocks of organic carbon stored in permafrost of the Western Siberian Lowland, the world’s largest peatland, is uncertain. Specifically, the amount of greenhouse gas emissions from rivers in the region is unknown. Here we present estimates of annual CO2 emissions from 58 rivers across all permafrost zones of the Western Siberian Lowland, between 56 and 67° N. We find that emissions peak at the permafrost boundary, and decrease where permafrost is more prevalent and in colder climatic conditions. River CO2 emissions were high, and on average two times greater than downstream carbon export. We suggest that high emissions and emission/export ratios are a result of warm temperatures and the long transit times of river water. We show that rivers in the Western Siberian Lowland play an important role in the carbon cycle by degassing terrestrial carbon before its transport to the Arctic Ocean, and suggest that changes in both temperature and precipitation are important for understanding and predicting high-latitude river CO2 emissions in a changing climate.

@article{schwieger_autumnal_2018,
	title = {Autumnal warming does not change root phenology in two contrasting vegetation types of subarctic tundra},
	volume = {424},
	issn = {1573-5036},
	url = {https://doi.org/10.1007/s11104-017-3343-5},
	doi = {10.1007/s11104-017-3343-5},
	abstract = {Root phenology is important in controlling carbon and nutrient fluxes in terrestrial ecosystems, yet, remains largely unexplored, especially in the Arctic. We compared below- and aboveground phenology and ending of the growing season in two contrasting vegetation types of subarctic tundra: heath and meadow, and their response to experimental warming in autumn.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Plant and Soil},
	author = {Schwieger, Sarah and Kreyling, Jürgen and Milbau, Ann and Blume-Werry, Gesche},
	month = mar,
	year = {2018},
	keywords = {\#nosource, Belowground, Climate change, Fine roots, Plant phenology, Root growth, Subarctic tundra},
	pages = {145--156},
}

Root phenology is important in controlling carbon and nutrient fluxes in terrestrial ecosystems, yet, remains largely unexplored, especially in the Arctic. We compared below- and aboveground phenology and ending of the growing season in two contrasting vegetation types of subarctic tundra: heath and meadow, and their response to experimental warming in autumn.

@article{pokrovsky_freeze-thaw_2018,
	title = {Freeze-thaw cycles of {Arctic} thaw ponds remove colloidal metals and generate low-molecular-weight organic matter},
	volume = {137},
	issn = {1573-515X},
	url = {https://doi.org/10.1007/s10533-018-0421-6},
	doi = {10.1007/s10533-018-0421-6},
	abstract = {High-latitude boreal and arctic surface/inland waters contain sizeable reservoirs of dissolved organic matter (DOM) and trace elements (TE), which are subject to seasonal freezing. Specifically, shallow ponds and lakes in the permafrost zone often freeze solid, which can lead to transformations in the colloidal and dissolved fractions of DOM and TE. Here, we present results from experimental freeze-thaw cycles using iron (Fe)- and DOM-rich water from thaw ponds situated in Stordalen and Storflaket palsa mires in northern Sweden. After ten cycles of freezing, 85\% of Fe and 25\% of dissolved organic carbon (DOC) were removed from solution in circumneutral fen water (pH 6.9) but a much smaller removal of Fe and DOC ({\textless} 7\%) was found in acidic bog water (pH 3.6). This removal pattern was consistent with initial supersaturation of fen water with respect to Fe hydroxide and a lack of supersaturation with any secondary mineral phase in the bog water. There was a nearly two- to threefold increase in the low-molecular-weight (LMW) fraction of organic carbon (OC) and several TEs caused by the repeated freeze-thaw cycles. Future increases in the freeze-thaw frequency of surface waters with climate warming may remove up to 25\% of DOC in circumneutral organic-rich waters. Furthermore, an increase of LMW OC may result in enhanced carbon dioxide losses from aquatic ecosystems since this fraction is potentially more susceptible to biodegradation.},
	language = {en},
	number = {3},
	urldate = {2024-03-27},
	journal = {Biogeochemistry},
	author = {Pokrovsky, Oleg S. and Karlsson, Jan and Giesler, Reiner},
	month = feb,
	year = {2018},
	keywords = {\#nosource, Bog, Carbon, Fen, Metal, Peat, Ultrafiltration, stordalen, storflaket},
	pages = {321--336},
}

High-latitude boreal and arctic surface/inland waters contain sizeable reservoirs of dissolved organic matter (DOM) and trace elements (TE), which are subject to seasonal freezing. Specifically, shallow ponds and lakes in the permafrost zone often freeze solid, which can lead to transformations in the colloidal and dissolved fractions of DOM and TE. Here, we present results from experimental freeze-thaw cycles using iron (Fe)- and DOM-rich water from thaw ponds situated in Stordalen and Storflaket palsa mires in northern Sweden. After ten cycles of freezing, 85% of Fe and 25% of dissolved organic carbon (DOC) were removed from solution in circumneutral fen water (pH 6.9) but a much smaller removal of Fe and DOC (\textless 7%) was found in acidic bog water (pH 3.6). This removal pattern was consistent with initial supersaturation of fen water with respect to Fe hydroxide and a lack of supersaturation with any secondary mineral phase in the bog water. There was a nearly two- to threefold increase in the low-molecular-weight (LMW) fraction of organic carbon (OC) and several TEs caused by the repeated freeze-thaw cycles. Future increases in the freeze-thaw frequency of surface waters with climate warming may remove up to 25% of DOC in circumneutral organic-rich waters. Furthermore, an increase of LMW OC may result in enhanced carbon dioxide losses from aquatic ecosystems since this fraction is potentially more susceptible to biodegradation.

@article{myrstener_persistent_2018,
	title = {Persistent nitrogen limitation of stream biofilm communities along climate gradients in the {Arctic}},
	volume = {24},
	copyright = {© 2018 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14117},
	doi = {10.1111/gcb.14117},
	abstract = {Climate change is rapidly reshaping Arctic landscapes through shifts in vegetation cover and productivity, soil resource mobilization, and hydrological regimes. The implications of these changes for stream ecosystems and food webs is unclear and will depend largely on microbial biofilm responses to concurrent shifts in temperature, light, and resource supply from land. To study those responses, we used nutrient diffusing substrates to manipulate resource supply to biofilm communities along regional gradients in stream temperature, riparian shading, and dissolved organic carbon (DOC) loading in Arctic Sweden. We found strong nitrogen (N) limitation across this gradient for gross primary production, community respiration and chlorophyll-a accumulation. For unamended biofilms, activity and biomass accrual were not closely related to any single physical or chemical driver across this region. However, the magnitude of biofilm response to N addition was: in tundra streams, biofilm response was constrained by thermal regimes, whereas variation in light availability regulated this response in birch and coniferous forest streams. Furthermore, heterotrophic responses to experimental N addition increased across the region with greater stream water concentrations of DOC relative to inorganic N. Thus, future shifts in resource supply to these ecosystems are likely to interact with other concurrent environmental changes to regulate stream productivity. Indeed, our results suggest that in the absence of increased nutrient inputs, Arctic streams will be less sensitive to future changes in other habitat variables such as temperature and DOC loading.},
	language = {en},
	number = {8},
	urldate = {2024-03-27},
	journal = {Global Change Biology},
	author = {Myrstener, Maria and Rocher-Ros, Gerard and Burrows, Ryan M. and Bergström, Ann-Kristin and Giesler, Reiner and Sponseller, Ryan A.},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14117},
	keywords = {\#nosource, Arctic, Bioassay, Biofilm, Climate Change, Co-limitation, Nitrogen limitation, Nutrient addition, Stream productivity, bioassay, biofilm, climate change, colimitation, nitrogen limitation, nutrient addition, stream productivity},
	pages = {3680--3691},
}

Climate change is rapidly reshaping Arctic landscapes through shifts in vegetation cover and productivity, soil resource mobilization, and hydrological regimes. The implications of these changes for stream ecosystems and food webs is unclear and will depend largely on microbial biofilm responses to concurrent shifts in temperature, light, and resource supply from land. To study those responses, we used nutrient diffusing substrates to manipulate resource supply to biofilm communities along regional gradients in stream temperature, riparian shading, and dissolved organic carbon (DOC) loading in Arctic Sweden. We found strong nitrogen (N) limitation across this gradient for gross primary production, community respiration and chlorophyll-a accumulation. For unamended biofilms, activity and biomass accrual were not closely related to any single physical or chemical driver across this region. However, the magnitude of biofilm response to N addition was: in tundra streams, biofilm response was constrained by thermal regimes, whereas variation in light availability regulated this response in birch and coniferous forest streams. Furthermore, heterotrophic responses to experimental N addition increased across the region with greater stream water concentrations of DOC relative to inorganic N. Thus, future shifts in resource supply to these ecosystems are likely to interact with other concurrent environmental changes to regulate stream productivity. Indeed, our results suggest that in the absence of increased nutrient inputs, Arctic streams will be less sensitive to future changes in other habitat variables such as temperature and DOC loading.

@article{metcalfe_patchy_2018,
	title = {Patchy field sampling biases understanding of climate change impacts across the {Arctic}},
	volume = {2},
	copyright = {2018 The Author(s), under exclusive licence to Springer Nature Limited},
	issn = {2397-334X},
	url = {https://www.nature.com/articles/s41559-018-0612-5},
	doi = {10.1038/s41559-018-0612-5},
	abstract = {Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31\% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.},
	language = {en},
	number = {9},
	urldate = {2024-03-27},
	journal = {Nature Ecology \& Evolution},
	author = {Metcalfe, Daniel B. and Hermans, Thirze D. G. and Ahlstrand, Jenny and Becker, Michael and Berggren, Martin and Björk, Robert G. and Björkman, Mats P. and Blok, Daan and Chaudhary, Nitin and Chisholm, Chelsea and Classen, Aimée T. and Hasselquist, Niles J. and Jonsson, Micael and Kristensen, Jeppe A. and Kumordzi, Bright B. and Lee, Hanna and Mayor, Jordan R. and Prevéy, Janet and Pantazatou, Karolina and Rousk, Johannes and Sponseller, Ryan A. and Sundqvist, Maja K. and Tang, Jing and Uddling, Johan and Wallin, Göran and Zhang, Wenxin and Ahlström, Anders and Tenenbaum, David E. and Abdi, Abdulhakim M.},
	month = sep,
	year = {2018},
	note = {Publisher: Nature Publishing Group},
	keywords = {\#nosource, Climate change, Environmental sciences, Research data},
	pages = {1443--1448},
}

Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.

@article{lett_role_2018,
	title = {The role of bryophytes for tree seedling responses to winter climate change: {Implications} for the stress gradient hypothesis},
	volume = {106},
	copyright = {© 2017 The Authors. Journal of Ecology © 2017 British Ecological Society},
	issn = {1365-2745},
	shorttitle = {The role of bryophytes for tree seedling responses to winter climate change},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.12898},
	doi = {10.1111/1365-2745.12898},
	abstract = {When tree seedlings establish beyond the current tree line due to climate warming, they encounter existing vegetation, such as bryophytes that often dominate in arctic and alpine tundra. The stress gradient hypothesis (SGH) predicts that plant interactions in tundra become increasingly negative as climate warms and conditions become less harsh. However, for seedlings, climate warming might not result in lower winter stress, if insulating snow cover is reduced. We aimed to understand if bryophytes facilitate seedling survival in a changing winter climate and if these effects of bryophytes on tree seedlings comply with the SGH along elevational gradients under contrasting snow conditions. In the Swedish subarctic, we transplanted intact bryophyte cores covered by each of three bryophyte species and bryophyte-free control soil from above the tree line to two field common garden sites, representing current and future tree line air temperature conditions (i.e. current tree line elevation and a lower, warmer, elevation below the tree line). We planted seedlings of Betula pubescens and Pinus sylvestris into these cores and subjected them to experimental manipulation of snow cover during one winter. In agreement with the SGH, milder conditions caused by increased snow cover enhanced the generally negative or neutral effects of bryophytes on seedlings immediately after winter. Furthermore, survival of P. sylvestris seedlings after one full year was higher at lower elevation, especially when snow cover was thinner. However, in contrast with the SGH, impacts of bryophytes on over-winter survival of seedlings did not differ between elevations, and impacts on survival of B. pubescens seedlings after 1 year was more negative at lower elevation. Bryophyte species differed in their effect on seedling survival after winter, but these differences were not related to their insulating capacity. Synthesis. Our study demonstrates that interactions from bryophytes can modify the impacts of winter climate change on tree seedlings, and vice versa. These responses do not always comply with SGH, but could ultimately have consequences for large-scale ecological processes such as tree line shifts. These new insights need to be taken into account in predictions of plant species responses to climate change.},
	language = {en},
	number = {3},
	urldate = {2024-03-27},
	journal = {Journal of Ecology},
	author = {Lett, Signe and Wardle, David A. and Nilsson, Marie-Charlotte and Teuber, Laurenz M. and Dorrepaal, Ellen},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2745.12898},
	keywords = {\#nosource, B. pubescens, P. sylvestris, alpine, climate change, competition, facilitation, plant–plant interactions, snow cover, subarctic, tree line},
	pages = {1142--1155},
}

When tree seedlings establish beyond the current tree line due to climate warming, they encounter existing vegetation, such as bryophytes that often dominate in arctic and alpine tundra. The stress gradient hypothesis (SGH) predicts that plant interactions in tundra become increasingly negative as climate warms and conditions become less harsh. However, for seedlings, climate warming might not result in lower winter stress, if insulating snow cover is reduced. We aimed to understand if bryophytes facilitate seedling survival in a changing winter climate and if these effects of bryophytes on tree seedlings comply with the SGH along elevational gradients under contrasting snow conditions. In the Swedish subarctic, we transplanted intact bryophyte cores covered by each of three bryophyte species and bryophyte-free control soil from above the tree line to two field common garden sites, representing current and future tree line air temperature conditions (i.e. current tree line elevation and a lower, warmer, elevation below the tree line). We planted seedlings of Betula pubescens and Pinus sylvestris into these cores and subjected them to experimental manipulation of snow cover during one winter. In agreement with the SGH, milder conditions caused by increased snow cover enhanced the generally negative or neutral effects of bryophytes on seedlings immediately after winter. Furthermore, survival of P. sylvestris seedlings after one full year was higher at lower elevation, especially when snow cover was thinner. However, in contrast with the SGH, impacts of bryophytes on over-winter survival of seedlings did not differ between elevations, and impacts on survival of B. pubescens seedlings after 1 year was more negative at lower elevation. Bryophyte species differed in their effect on seedling survival after winter, but these differences were not related to their insulating capacity. Synthesis. Our study demonstrates that interactions from bryophytes can modify the impacts of winter climate change on tree seedlings, and vice versa. These responses do not always comply with SGH, but could ultimately have consequences for large-scale ecological processes such as tree line shifts. These new insights need to be taken into account in predictions of plant species responses to climate change.

@article{ledesma_towards_2018,
	title = {Towards an {Improved} {Conceptualization} of {Riparian} {Zones} in {Boreal} {Forest} {Headwaters}},
	volume = {21},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-017-0149-5},
	doi = {10.1007/s10021-017-0149-5},
	abstract = {The boreal ecoregion supports about one-third of the world’s forest. Over 90\% of boreal forest streams are found in headwaters, where terrestrial–aquatic interfaces are dominated by organic matter (OM)-rich riparian zones (RZs). Because these transition zones are key features controlling catchment biogeochemistry, appropriate RZ conceptualizations are needed to sustainably manage surface water quality in the face of a changing climate and increased demands for forest biomass. Here we present a simple, yet comprehensive, conceptualization of RZ function based on hydrological connectivity, biogeochemical processes, and spatial heterogeneity. We consider four dimensions of hydrological connectivity: (1) laterally along hillslopes, (2) longitudinally along the stream, (3) vertically down the riparian profile, and (4) temporally through event-based and seasonal changes in hydrology. Of particular importance is the vertical dimension, characterized by a ‘Dominant Source Layer’ that has the highest contribution to solute and water fluxes to streams. In addition to serving as the primary source of OM to boreal streams, RZs shape water chemistry through two sets of OM-dependent biogeochemical processes: (1) transport and retention of OM-associated material and (2) redox-mediated transformations controlled by RZ water residence time and availability of labile OM. These processes can lead to both retention and release of pollutants. Variations in width, hydrological connectivity, and OM storage drive spatial heterogeneity in RZ biogeochemical function. This conceptualization provides a useful theoretical framework for environmental scientists and ecologically sustainable and economically effective forest management in the boreal region and elsewhere, where forest headwaters are dominated by low-gradient, OM-rich RZs.},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {Ecosystems},
	author = {Ledesma, José L. J. and Futter, Martyn N. and Blackburn, M. and Lidman, Fredrik and Grabs, Thomas and Sponseller, Ryan A. and Laudon, Hjalmar and Bishop, Kevin H. and Köhler, Stephan J.},
	month = mar,
	year = {2018},
	keywords = {\#nosource, catchment biogeochemistry, catchment heterogeneity, forest management, hydrological connectivity, redox, riparian buffer, soil organic matter, terrestrial–aquatic interface, water quality},
	pages = {297--315},
}

The boreal ecoregion supports about one-third of the world’s forest. Over 90% of boreal forest streams are found in headwaters, where terrestrial–aquatic interfaces are dominated by organic matter (OM)-rich riparian zones (RZs). Because these transition zones are key features controlling catchment biogeochemistry, appropriate RZ conceptualizations are needed to sustainably manage surface water quality in the face of a changing climate and increased demands for forest biomass. Here we present a simple, yet comprehensive, conceptualization of RZ function based on hydrological connectivity, biogeochemical processes, and spatial heterogeneity. We consider four dimensions of hydrological connectivity: (1) laterally along hillslopes, (2) longitudinally along the stream, (3) vertically down the riparian profile, and (4) temporally through event-based and seasonal changes in hydrology. Of particular importance is the vertical dimension, characterized by a ‘Dominant Source Layer’ that has the highest contribution to solute and water fluxes to streams. In addition to serving as the primary source of OM to boreal streams, RZs shape water chemistry through two sets of OM-dependent biogeochemical processes: (1) transport and retention of OM-associated material and (2) redox-mediated transformations controlled by RZ water residence time and availability of labile OM. These processes can lead to both retention and release of pollutants. Variations in width, hydrological connectivity, and OM storage drive spatial heterogeneity in RZ biogeochemical function. This conceptualization provides a useful theoretical framework for environmental scientists and ecologically sustainable and economically effective forest management in the boreal region and elsewhere, where forest headwaters are dominated by low-gradient, OM-rich RZs.

@article{laudon_how_2018,
	title = {How landscape organization and scale shape catchment hydrology and biogeochemistry: insights from a long-term catchment study},
	volume = {5},
	copyright = {© 2017 Wiley Periodicals, Inc.},
	issn = {2049-1948},
	shorttitle = {How landscape organization and scale shape catchment hydrology and biogeochemistry},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/wat2.1265},
	doi = {10.1002/wat2.1265},
	abstract = {Catchment science plays a critical role in the protection of water resources in the face of ongoing changes in climate, long-range transport of air pollutants, and land use. Addressing these challenges, however, requires improved understanding of how, when, and where changes in water quantity and quality occur within river networks. To reach these goals, we must recognize how different catchment features are organized to regulate surface chemistry at multiple scales, from processes controlling headwaters, to the downstream mixing of water from multiple landscape sources and deep aquifers. Here we synthesize 30-years of hydrological and biogeochemical research from the Krycklan catchment study (KCS) in northern Sweden to demonstrate the benefits of coupling long-term monitoring with multi-scale research to advance our understanding of catchment functioning across space and time. We show that the regulation of hydrological and biogeochemical patterns in the KCS can be decomposed into four, hierarchically structured landscape features that include: (1) transmissivity and reactivity of dominant source layers within riparian soils, (2) spatial arrangement of groundwater input zones that govern water and solute fluxes at reach- to segment-scales, (3) landscape scale heterogeneity (forests, mires, and lakes) that generates unique biogeochemical signals downstream, and (4) broad-scale mixing of surface streams with deep groundwater contributions. While this set of features are perhaps specific to the study region, analogous hierarchical controls are likely to be widespread. Resolving these scale dependent processes is important for predicting how, when, and where different environmental changes may influence patterns of surface water chemistry within river networks. WIREs Water 2018, 5:e1265. doi: 10.1002/wat2.1265 This article is categorized under: Science of Water {\textgreater} Hydrological Processes Science of Water {\textgreater} Water and Environmental Change Science of Water {\textgreater} Methods},
	language = {en},
	number = {2},
	urldate = {2024-03-27},
	journal = {WIREs Water},
	author = {Laudon, Hjalmar and Sponseller, Ryan A.},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/wat2.1265},
	keywords = {\#nosource},
	pages = {e1265},
}

Catchment science plays a critical role in the protection of water resources in the face of ongoing changes in climate, long-range transport of air pollutants, and land use. Addressing these challenges, however, requires improved understanding of how, when, and where changes in water quantity and quality occur within river networks. To reach these goals, we must recognize how different catchment features are organized to regulate surface chemistry at multiple scales, from processes controlling headwaters, to the downstream mixing of water from multiple landscape sources and deep aquifers. Here we synthesize 30-years of hydrological and biogeochemical research from the Krycklan catchment study (KCS) in northern Sweden to demonstrate the benefits of coupling long-term monitoring with multi-scale research to advance our understanding of catchment functioning across space and time. We show that the regulation of hydrological and biogeochemical patterns in the KCS can be decomposed into four, hierarchically structured landscape features that include: (1) transmissivity and reactivity of dominant source layers within riparian soils, (2) spatial arrangement of groundwater input zones that govern water and solute fluxes at reach- to segment-scales, (3) landscape scale heterogeneity (forests, mires, and lakes) that generates unique biogeochemical signals downstream, and (4) broad-scale mixing of surface streams with deep groundwater contributions. While this set of features are perhaps specific to the study region, analogous hierarchical controls are likely to be widespread. Resolving these scale dependent processes is important for predicting how, when, and where different environmental changes may influence patterns of surface water chemistry within river networks. WIREs Water 2018, 5:e1265. doi: 10.1002/wat2.1265 This article is categorized under: Science of Water \textgreater Hydrological Processes Science of Water \textgreater Water and Environmental Change Science of Water \textgreater Methods

@article{jonsson_catchment_2018,
	title = {Catchment properties predict autochthony in stream filter feeders},
	volume = {815},
	issn = {1573-5117},
	url = {https://doi.org/10.1007/s10750-018-3553-8},
	doi = {10.1007/s10750-018-3553-8},
	abstract = {Stream ecological theory predicts that the use of allochthonous resources declines with increasing channel width, while at the same time primary production and autochthonous carbon use by consumers increase. Although these expectations have found support in several studies, it is not well known how terrestrial runoff and/or inputs of primary production from lakes alter these longitudinal patterns. To investigate this, we analyzed the diet of filter-feeding black fly and caddisfly larvae from 23 boreal streams, encompassing gradients in drainage area, land cover and land use, and distance to nearest upstream lake outlet. In five of these streams, we also sampled repeatedly during autumn to test if allochthony of filter feeders increases over time as new litter inputs are processed. Across sites, filter-feeder autochthony was 21.1–75.1\%, did not differ between black fly and caddisfly larvae, was not positively related to drainage area, and did not decrease with distance from lakes. Instead, lake and wetland cover promoted filter-feeder autochthony independently of stream size, whereas catchment-scale forest cover and forestry reduced autochthony. Further, we found no seasonal increase in allochthony, indicating low assimilation of particles derived from autumn litter fall. Hence, catchment properties, rather than local conditions, can influence levels of autochthony in boreal streams.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Hydrobiologia},
	author = {Jonsson, Micael and Polvi, Lina E. and Sponseller, Ryan A. and Stenroth, Karolina},
	month = jun,
	year = {2018},
	keywords = {\#nosource, Allochthony, Aquatic insects, Autochthony, Land cover, Land use, Stream},
	pages = {83--95},
}

Stream ecological theory predicts that the use of allochthonous resources declines with increasing channel width, while at the same time primary production and autochthonous carbon use by consumers increase. Although these expectations have found support in several studies, it is not well known how terrestrial runoff and/or inputs of primary production from lakes alter these longitudinal patterns. To investigate this, we analyzed the diet of filter-feeding black fly and caddisfly larvae from 23 boreal streams, encompassing gradients in drainage area, land cover and land use, and distance to nearest upstream lake outlet. In five of these streams, we also sampled repeatedly during autumn to test if allochthony of filter feeders increases over time as new litter inputs are processed. Across sites, filter-feeder autochthony was 21.1–75.1%, did not differ between black fly and caddisfly larvae, was not positively related to drainage area, and did not decrease with distance from lakes. Instead, lake and wetland cover promoted filter-feeder autochthony independently of stream size, whereas catchment-scale forest cover and forestry reduced autochthony. Further, we found no seasonal increase in allochthony, indicating low assimilation of particles derived from autumn litter fall. Hence, catchment properties, rather than local conditions, can influence levels of autochthony in boreal streams.

@article{hasselquist_identifying_2018,
	title = {Identifying and assessing the potential hydrological function of past artificial forest drainage},
	volume = {47},
	issn = {1654-7209},
	url = {https://doi.org/10.1007/s13280-017-0984-9},
	doi = {10.1007/s13280-017-0984-9},
	abstract = {Drainage of forested wetlands for increased timber production has profoundly altered the hydrology and water quality of their downstream waterways. Some ditches need network maintenance (DNM), but potential positive effects on tree productivity must be balanced against environmental impacts. Currently, no clear guidelines exist for DNM that strike this balance. Our study helps begin to prioritise DNM by: (1) quantifying ditches by soil type in the 68 km2 Krycklan Catchment Study in northern Sweden and (2) using upslope catchment area algorithms on new high-resolution digital elevation models to determine their likelihood to drain water. Ditches nearly doubled the size of the stream network (178–327 km) and 17\% of ditches occurred on well-draining sedimentary soils, presumably making DNM unwarranted. Modelling results suggest that 25–50\% of ditches may never support flow. With new laser scanning technology, simple mapping and modelling methods can locate ditches and model their function, facilitating efforts to balance DNM with environmental impacts.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Ambio},
	author = {Hasselquist, Eliza Maher and Lidberg, William and Sponseller, Ryan A. and Ågren, Anneli and Laudon, Hjalmar},
	month = sep,
	year = {2018},
	keywords = {\#nosource, DEM, Flow accumulation model, Hydrology, LiDAR, Peatland, Terrain-based prediction},
	pages = {546--556},
}

Drainage of forested wetlands for increased timber production has profoundly altered the hydrology and water quality of their downstream waterways. Some ditches need network maintenance (DNM), but potential positive effects on tree productivity must be balanced against environmental impacts. Currently, no clear guidelines exist for DNM that strike this balance. Our study helps begin to prioritise DNM by: (1) quantifying ditches by soil type in the 68 km2 Krycklan Catchment Study in northern Sweden and (2) using upslope catchment area algorithms on new high-resolution digital elevation models to determine their likelihood to drain water. Ditches nearly doubled the size of the stream network (178–327 km) and 17% of ditches occurred on well-draining sedimentary soils, presumably making DNM unwarranted. Modelling results suggest that 25–50% of ditches may never support flow. With new laser scanning technology, simple mapping and modelling methods can locate ditches and model their function, facilitating efforts to balance DNM with environmental impacts.

@article{george_organic_2018,
	title = {Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities},
	volume = {427},
	issn = {1573-5036},
	shorttitle = {Organic phosphorus in the terrestrial environment},
	url = {https://doi.org/10.1007/s11104-017-3391-x},
	doi = {10.1007/s11104-017-3391-x},
	abstract = {The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Plant and Soil},
	author = {George, T. S. and Giles, C. D. and Menezes-Blackburn, D. and Condron, L. M. and Gama-Rodrigues, A. C. and Jaisi, D. and Lang, F. and Neal, A. L. and Stutter, M. I. and Almeida, D. S. and Bol, R. and Cabugao, K. G. and Celi, L. and Cotner, J. B. and Feng, G. and Goll, D. S. and Hallama, M. and Krueger, J. and Plassard, C. and Rosling, A. and Darch, T. and Fraser, T. and Giesler, R. and Richardson, A. E. and Tamburini, F. and Shand, C. A. and Lumsdon, D. G. and Zhang, H. and Blackwell, M. S. A. and Wearing, C. and Mezeli, M. M. and Almås, Å. R. and Audette, Y. and Bertrand, I. and Beyhaut, E. and Boitt, G. and Bradshaw, N. and Brearley, C. A. and Bruulsema, T. W. and Ciais, P. and Cozzolino, V. and Duran, P. C. and Mora, M. L. and de Menezes, A. B. and Dodd, R. J. and Dunfield, K. and Engl, C. and Frazão, J. J. and Garland, G. and González Jiménez, J. L. and Graca, J. and Granger, S. J. and Harrison, A. F. and Heuck, C. and Hou, E. Q. and Johnes, P. J. and Kaiser, K. and Kjær, H. A. and Klumpp, E. and Lamb, A. L. and Macintosh, K. A. and Mackay, E. B. and McGrath, J. and McIntyre, C. and McLaren, T. and Mészáros, E. and Missong, A. and Mooshammer, M. and Negrón, C. P. and Nelson, L. A. and Pfahler, V. and Poblete-Grant, P. and Randall, M. and Seguel, A. and Seth, K. and Smith, A. C. and Smits, M. M. and Sobarzo, J. A. and Spohn, M. and Tawaraya, K. and Tibbett, M. and Voroney, P. and Wallander, H. and Wang, L. and Wasaki, J. and Haygarth, P. M.},
	month = jun,
	year = {2018},
	keywords = {\#nosource, Ecosystems services, Method development, Microbiome, Modelling, Organic phosphorus, Stoichiometry},
	pages = {191--208},
}

The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction.

@article{becher_decreased_2018,
	title = {Decreased cryogenic disturbance: one of the potential mechanisms behind the vegetation change in the {Arctic}},
	volume = {41},
	issn = {1432-2056},
	shorttitle = {Decreased cryogenic disturbance},
	url = {https://doi.org/10.1007/s00300-017-2173-5},
	doi = {10.1007/s00300-017-2173-5},
	abstract = {During the last few decades, the Arctic has experienced large-scale vegetation changes. Understanding the mechanisms behind this vegetation change is crucial for our ability to predict future changes. This study tested the hypothesis that decreased cryogenic disturbances cause vegetation change in patterned ground study fields (non-sorted circles) in Abisko, Sweden during the last few decades. The hypothesis was tested by surveying the composition of plant communities across a gradient in cryogenic disturbance and by reinvestigating plant communities previously surveyed in the 1980s to scrutinise how these communities changed in response to reduced cryogenic disturbance. Whereas the historical changes in species occurrence associated with decreased cryogenic disturbances were relatively consistent with the changes along the contemporary gradient of cryogenic disturbances, the species abundance revealed important transient changes highly dependent on the initial plant community composition. Our results suggest that altered cryogenic disturbances cause temporal changes in vegetation dynamics, but the net effects on vegetation communities depend on the composition of initial plant species.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Polar Biology},
	author = {Becher, M. and Olofsson, J. and Berglund, L. and Klaminder, J.},
	month = jan,
	year = {2018},
	keywords = {\#nosource, Cryogenic disturbance, Differential heave, Freeze/thaw-indices, Non-sorted circles, Patterned ground, Plant abundance},
	pages = {101--110},
}

During the last few decades, the Arctic has experienced large-scale vegetation changes. Understanding the mechanisms behind this vegetation change is crucial for our ability to predict future changes. This study tested the hypothesis that decreased cryogenic disturbances cause vegetation change in patterned ground study fields (non-sorted circles) in Abisko, Sweden during the last few decades. The hypothesis was tested by surveying the composition of plant communities across a gradient in cryogenic disturbance and by reinvestigating plant communities previously surveyed in the 1980s to scrutinise how these communities changed in response to reduced cryogenic disturbance. Whereas the historical changes in species occurrence associated with decreased cryogenic disturbances were relatively consistent with the changes along the contemporary gradient of cryogenic disturbances, the species abundance revealed important transient changes highly dependent on the initial plant community composition. Our results suggest that altered cryogenic disturbances cause temporal changes in vegetation dynamics, but the net effects on vegetation communities depend on the composition of initial plant species.

@article{barthelemy_urine_2018,
	title = {Urine is an important nitrogen source for plants irrespective of vegetation composition in an {Arctic} tundra: {Insights} from a {15N}-enriched urea tracer experiment},
	volume = {106},
	copyright = {© 2017 The Authors. Journal of Ecology © 2017 British Ecological Society},
	issn = {1365-2745},
	shorttitle = {Urine is an important nitrogen source for plants irrespective of vegetation composition in an {Arctic} tundra},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.12820},
	doi = {10.1111/1365-2745.12820},
	abstract = {Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems. This study explored the fate of 15N-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50 years. We followed the fate of the 15N applied to the plant canopy, at 2 weeks and 1 year after tracer addition, in the different ecosystem N pools. 15N-urea was rapidly incorporated in cryptogams and in above-ground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Furthermore, the litter layer constituted a large sink for the 15N-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition. Mosses and lichens still constituted the largest sink for the 15N-urea 1 year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the 15N-urea. The total recovery of 15N-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention. Synthesis. The rapid incorporation of the applied 15N-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, δ15N values of all taxa in the heavily grazed sites converged towards the δ15N values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.},
	language = {en},
	number = {1},
	urldate = {2024-03-27},
	journal = {Journal of Ecology},
	author = {Barthelemy, Hélène and Stark, Sari and Michelsen, Anders and Olofsson, Johan},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2745.12820},
	keywords = {\#nosource, Arctic tundra, N labelling, above- and belowground linkages, cryptogams, grazing intensity, microbial N biomass, nutrient cycling, plant nutrient uptake, plant–herbivore interactions, urine},
	pages = {367--378},
}

Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems. This study explored the fate of 15N-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50 years. We followed the fate of the 15N applied to the plant canopy, at 2 weeks and 1 year after tracer addition, in the different ecosystem N pools. 15N-urea was rapidly incorporated in cryptogams and in above-ground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Furthermore, the litter layer constituted a large sink for the 15N-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition. Mosses and lichens still constituted the largest sink for the 15N-urea 1 year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the 15N-urea. The total recovery of 15N-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention. Synthesis. The rapid incorporation of the applied 15N-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, δ15N values of all taxa in the heavily grazed sites converged towards the δ15N values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.

@article{seekell_lake_2018,
	title = {Lake morphometry moderates the relationship between water color and fish biomass in small boreal lakes},
	volume = {63},
	copyright = {© 2018 The Authors Limnology and Oceanography published by Wiley Periodicals, Inc.  on behalf of Association for the Sciences of Limnology and Oceanography},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.10931},
	doi = {10.1002/lno.10931},
	abstract = {Lake morphometry may moderate the effects of water color on fish biomass in boreal lakes, but empirical evidence is scarce because there are a limited number of lakes for which both water color and bathymetry have been measured. We evaluated variations in catch-per-unit-effort (CPUE), an indicator of fish biomass, across orthogonal gradients of light extinction and mean depth in 16 small Swedish lakes (mean depth 1.7–4.8 m, surface area 1–10 ha). Multiple regression coefficients indicated that the effect of light extinction on CPUE was negative, and that the relationship was more negative for deeper lakes than it was for shallower lakes. The pattern was strongest for lakes with mean depths between 2.1 m and 3.5 m. We estimated that 26\% of small lakes in boreal Sweden fall within this mean depth range. These results contribute to the growing understanding of how variations in water color and lake morphometry influence patterns of fish biomass across the boreal landscape.},
	language = {en},
	number = {5},
	urldate = {2024-03-27},
	journal = {Limnology and Oceanography},
	author = {Seekell, David A. and Byström, Pär and Karlsson, Jan},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.10931},
	keywords = {\#nosource},
	pages = {2171--2178},
}

Lake morphometry may moderate the effects of water color on fish biomass in boreal lakes, but empirical evidence is scarce because there are a limited number of lakes for which both water color and bathymetry have been measured. We evaluated variations in catch-per-unit-effort (CPUE), an indicator of fish biomass, across orthogonal gradients of light extinction and mean depth in 16 small Swedish lakes (mean depth 1.7–4.8 m, surface area 1–10 ha). Multiple regression coefficients indicated that the effect of light extinction on CPUE was negative, and that the relationship was more negative for deeper lakes than it was for shallower lakes. The pattern was strongest for lakes with mean depths between 2.1 m and 3.5 m. We estimated that 26% of small lakes in boreal Sweden fall within this mean depth range. These results contribute to the growing understanding of how variations in water color and lake morphometry influence patterns of fish biomass across the boreal landscape.

@article{radujkovic_prolonged_2018,
	title = {Prolonged exposure does not increase soil microbial community compositional response to warming along geothermal gradients},
	volume = {94},
	issn = {0168-6496},
	url = {https://doi.org/10.1093/femsec/fix174},
	doi = {10.1093/femsec/fix174},
	abstract = {Global change is expected to affect soil microbial communities through their responsiveness to temperature. It has been proposed that prolonged exposure to elevated temperatures may lead to progressively larger effects on soil microbial community composition. However, due to the relatively short-term nature of most warming experiments, this idea has been challenging to evaluate. The present study took the advantage of natural geothermal gradients (from +1°C to +19°C above ambient) in two subarctic grasslands to test the hypothesis that long-term exposure (\>50 years) intensifies the effect of warming on microbial community composition compared to short-term exposure (5–7 years). Community profiles from amplicon sequencing of bacterial and fungal rRNA genes did not support this hypothesis: significant changes relative to ambient were observed only starting from the warming intensity of +9°C in the long term and +7°C/+3°C in the short term, for bacteria and fungi, respectively. Our results suggest that microbial communities in high-latitude grasslands will not undergo lasting shifts in community composition under the warming predicted for the coming 100 years (+2.2°C to +8.3°C).},
	number = {2},
	urldate = {2024-03-27},
	journal = {FEMS Microbiology Ecology},
	author = {Radujković, Dajana and Verbruggen, Erik and Sigurdsson, Bjarni D and Leblans, Niki I W and Janssens, Ivan A and Vicca, Sara and Weedon, James T},
	month = feb,
	year = {2018},
	keywords = {\#nosource},
	pages = {fix174},
}

Global change is expected to affect soil microbial communities through their responsiveness to temperature. It has been proposed that prolonged exposure to elevated temperatures may lead to progressively larger effects on soil microbial community composition. However, due to the relatively short-term nature of most warming experiments, this idea has been challenging to evaluate. The present study took the advantage of natural geothermal gradients (from +1°C to +19°C above ambient) in two subarctic grasslands to test the hypothesis that long-term exposure (>50 years) intensifies the effect of warming on microbial community composition compared to short-term exposure (5–7 years). Community profiles from amplicon sequencing of bacterial and fungal rRNA genes did not support this hypothesis: significant changes relative to ambient were observed only starting from the warming intensity of +9°C in the long term and +7°C/+3°C in the short term, for bacteria and fungi, respectively. Our results suggest that microbial communities in high-latitude grasslands will not undergo lasting shifts in community composition under the warming predicted for the coming 100 years (+2.2°C to +8.3°C).

@article{pokrovsky_dissolved_2018,
	title = {Dissolved {Organic} {Matter} {Controls} {Seasonal} and {Spatial} {Selenium} {Concentration} {Variability} in {Thaw} {Lakes} across a {Permafrost} {Gradient}},
	volume = {52},
	issn = {0013-936X},
	url = {https://doi.org/10.1021/acs.est.8b00918},
	doi = {10.1021/acs.est.8b00918},
	abstract = {Little is known about the sources and processing of selenium, an important toxicant and essential micronutrient, within boreal and sub-arctic environments. Upon climate warming and permafrost thaw, the behavior of Se in northern peatlands becomes an issue of major concern, because a sizable amount of Se can be emitted to the atmosphere from thawing soils and inland water surfaces and exported to downstream waters, thus impacting the Arctic biota. Working toward providing a first-order assessment of spatial and temporal variation of Se concentration in thermokarst waters of the largest frozen peatland in the world, we sampled thaw lakes and rivers across a 750-km latitudinal profile. This profile covered sporadic, discontinuous, and continuous permafrost regions of western Siberia Lowland (WSL), where we measured dissolved ({\textless}0.45 μm) Se concentration during spring (June), summer (August), and autumn (September). We found maximum Se concentration in the discontinuous permafrost zone. Considering all sampled lakes, Se exhibited linear relationship (R2 = 0.7 to 0.9, p {\textless} 0.05, n ≈ 70) with dissolved organic carbon (DOC) concentration during summer and autumn. Across the permafrost gradient, the lakes in discontinuous permafrost regions demonstrated stronger relationship with DOC and UV-absorbance compared to lakes in sporadic/isolated and continuous permafrost zones. Both seasonal and spatial features of Se distribution in thermokarst lakes and ponds suggest that Se is mainly released during thawing of frozen peat. Mobilization and immobilization of Se within peat–lake–river watersheds likely occurs as organic and organo-Fe, Al colloids, probably associated with reduced and elemental Se forms. The increase of active layer thickness may enhance leaching of Se in the form of organic complexes with aromatic carbon from the deep horizons of the peat profile. Further, the northward shift of permafrost boundaries in WSL may sizably increase Se concentration in lakes of continuous permafrost zone.},
	number = {18},
	urldate = {2024-03-27},
	journal = {Environmental Science \& Technology},
	author = {Pokrovsky, Oleg S. and Bueno, Maite and Manasypov, Rinat M. and Shirokova, Liudmila S. and Karlsson, Jan and Amouroux, David},
	month = sep,
	year = {2018},
	note = {Publisher: American Chemical Society},
	keywords = {\#nosource},
	pages = {10254--10262},
}

Little is known about the sources and processing of selenium, an important toxicant and essential micronutrient, within boreal and sub-arctic environments. Upon climate warming and permafrost thaw, the behavior of Se in northern peatlands becomes an issue of major concern, because a sizable amount of Se can be emitted to the atmosphere from thawing soils and inland water surfaces and exported to downstream waters, thus impacting the Arctic biota. Working toward providing a first-order assessment of spatial and temporal variation of Se concentration in thermokarst waters of the largest frozen peatland in the world, we sampled thaw lakes and rivers across a 750-km latitudinal profile. This profile covered sporadic, discontinuous, and continuous permafrost regions of western Siberia Lowland (WSL), where we measured dissolved (\textless0.45 μm) Se concentration during spring (June), summer (August), and autumn (September). We found maximum Se concentration in the discontinuous permafrost zone. Considering all sampled lakes, Se exhibited linear relationship (R2 = 0.7 to 0.9, p \textless 0.05, n ≈ 70) with dissolved organic carbon (DOC) concentration during summer and autumn. Across the permafrost gradient, the lakes in discontinuous permafrost regions demonstrated stronger relationship with DOC and UV-absorbance compared to lakes in sporadic/isolated and continuous permafrost zones. Both seasonal and spatial features of Se distribution in thermokarst lakes and ponds suggest that Se is mainly released during thawing of frozen peat. Mobilization and immobilization of Se within peat–lake–river watersheds likely occurs as organic and organo-Fe, Al colloids, probably associated with reduced and elemental Se forms. The increase of active layer thickness may enhance leaching of Se in the form of organic complexes with aromatic carbon from the deep horizons of the peat profile. Further, the northward shift of permafrost boundaries in WSL may sizably increase Se concentration in lakes of continuous permafrost zone.

@article{kupryianchyk_industrial_2018,
	title = {Industrial and natural compounds in filter-feeding black fly larvae and water in 3 tundra streams},
	volume = {37},
	copyright = {© 2018 SETAC},
	issn = {1552-8618},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/etc.4267},
	doi = {10.1002/etc.4267},
	abstract = {We report concentrations of polychlorinated biphenyls, polybrominated diphenyl ethers, novel flame retardants, and naturally occurring bromoanisoles in water and filter-feeding black fly (Simuliidae) larvae in 3 tundra streams in northern Sweden. The results demonstrate that black fly larvae accumulate a wide range of organic contaminants and can be used as bioindicators of water pollution in Arctic streams. Environ Toxicol Chem 2018;37:3011–3017. © 2018 SETAC},
	language = {en},
	number = {12},
	urldate = {2024-03-26},
	journal = {Environmental Toxicology and Chemistry},
	author = {Kupryianchyk, Darya and Giesler, Reiner and Bidleman, Terry F. and Liljelind, Per and Lau, Danny Chun Pong and Sponseller, Ryan A. and Andersson, Patrik L.},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/etc.4267},
	keywords = {\#nosource, Arctic streams, Bioaccumulation, Emerging pollutants, Fate and transport, Legacy contaminants, Long-range transport, bioaccumulation, emerging pollutants, fate and transport},
	pages = {3011--3017},
}

We report concentrations of polychlorinated biphenyls, polybrominated diphenyl ethers, novel flame retardants, and naturally occurring bromoanisoles in water and filter-feeding black fly (Simuliidae) larvae in 3 tundra streams in northern Sweden. The results demonstrate that black fly larvae accumulate a wide range of organic contaminants and can be used as bioindicators of water pollution in Arctic streams. Environ Toxicol Chem 2018;37:3011–3017. © 2018 SETAC

@article{denfeld_carbon_2018,
	title = {Carbon {Dioxide} and {Methane} {Dynamics} in a {Small} {Boreal} {Lake} {During} {Winter} and {Spring} {Melt} {Events}},
	volume = {123},
	copyright = {©2018. American Geophysical Union. All Rights Reserved.},
	issn = {2169-8961},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018JG004622},
	doi = {10.1029/2018JG004622},
	abstract = {In seasonally ice-covered lakes, carbon dioxide (CO2) and methane (CH4) emission at ice-off can account for a significant fraction of the annual budget. Yet knowledge of the mechanisms controlling below lake-ice carbon (C) dynamics and subsequent CO2 and CH4 emissions at ice-off is limited. To understand the control of below ice C dynamics, and C emissions in spring, we measured spatial variation in CO2, CH4, and dissolved inorganic and organic carbon from ice-on to ice-off, in a small boreal lake during a winter with sporadic melting events. Winter melt events were associated with decreased surface water DOC in the forest-dominated basin and increased surface water CH4 in the mire-dominated basin. At the whole-lake scale, CH4 accumulated below ice throughout the winter, whereas CO2 accumulation was greatest in early winter. Mass-balance estimates suggest that, in addition to the CO2 and CH4 accumulated during winter, external inputs of CO2 and CH4 and internal processing during ice-melt could represent significant sources of C gas emissions during ice-off. Moreover, internal processing of CO2 and CH4 worked in opposition, with production of CO2 and oxidation of CH4 dominating at ice-off. These findings have important implications for how small boreal lakes will respond to warmer winters in the future; increased winter melt events will likely increase external inputs below ice and thus alter the extent and timing of CO2 and CH4 emissions to the atmosphere at ice-off.},
	language = {en},
	number = {8},
	urldate = {2024-03-26},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Denfeld, B. A. and Klaus, M. and Laudon, H. and Sponseller, R. A. and Karlsson, J.},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018JG004622},
	keywords = {\#nosource, carbon cycle, carbon dioxide, emissions, ice-covered lake, methane, winter limnology},
	pages = {2527--2540},
}

In seasonally ice-covered lakes, carbon dioxide (CO2) and methane (CH4) emission at ice-off can account for a significant fraction of the annual budget. Yet knowledge of the mechanisms controlling below lake-ice carbon (C) dynamics and subsequent CO2 and CH4 emissions at ice-off is limited. To understand the control of below ice C dynamics, and C emissions in spring, we measured spatial variation in CO2, CH4, and dissolved inorganic and organic carbon from ice-on to ice-off, in a small boreal lake during a winter with sporadic melting events. Winter melt events were associated with decreased surface water DOC in the forest-dominated basin and increased surface water CH4 in the mire-dominated basin. At the whole-lake scale, CH4 accumulated below ice throughout the winter, whereas CO2 accumulation was greatest in early winter. Mass-balance estimates suggest that, in addition to the CO2 and CH4 accumulated during winter, external inputs of CO2 and CH4 and internal processing during ice-melt could represent significant sources of C gas emissions during ice-off. Moreover, internal processing of CO2 and CH4 worked in opposition, with production of CO2 and oxidation of CH4 dominating at ice-off. These findings have important implications for how small boreal lakes will respond to warmer winters in the future; increased winter melt events will likely increase external inputs below ice and thus alter the extent and timing of CO2 and CH4 emissions to the atmosphere at ice-off.

@article{dodorico_global_2018,
	title = {The {Global} {Food}-{Energy}-{Water} {Nexus}},
	volume = {56},
	copyright = {©2018. The Authors.},
	issn = {1944-9208},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2017RG000591},
	doi = {10.1029/2017RG000591},
	abstract = {Water availability is a major factor constraining humanity's ability to meet the future food and energy needs of a growing and increasingly affluent human population. Water plays an important role in the production of energy, including renewable energy sources and the extraction of unconventional fossil fuels that are expected to become important players in future energy security. The emergent competition for water between the food and energy systems is increasingly recognized in the concept of the “food-energy-water nexus.” The nexus between food and water is made even more complex by the globalization of agriculture and rapid growth in food trade, which results in a massive virtual transfer of water among regions and plays an important role in the food and water security of some regions. This review explores multiple components of the food-energy-water nexus and highlights possible approaches that could be used to meet food and energy security with the limited renewable water resources of the planet. Despite clear tensions inherent in meeting the growing and changing demand for food and energy in the 21st century, the inherent linkages among food, water, and energy systems can offer an opportunity for synergistic strategies aimed at resilient food, water, and energy security, such as the circular economy.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Reviews of Geophysics},
	author = {D'Odorico, Paolo and Davis, Kyle Frankel and Rosa, Lorenzo and Carr, Joel A. and Chiarelli, Davide and Dell'Angelo, Jampel and Gephart, Jessica and MacDonald, Graham K. and Seekell, David A. and Suweis, Samir and Rulli, Maria Cristina},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2017RG000591},
	keywords = {\#nosource, Circular Economy, FEW Nexus, Food Security, Food-water nexus, Water Security, Water Sustainability},
	pages = {456--531},
}

Water availability is a major factor constraining humanity's ability to meet the future food and energy needs of a growing and increasingly affluent human population. Water plays an important role in the production of energy, including renewable energy sources and the extraction of unconventional fossil fuels that are expected to become important players in future energy security. The emergent competition for water between the food and energy systems is increasingly recognized in the concept of the “food-energy-water nexus.” The nexus between food and water is made even more complex by the globalization of agriculture and rapid growth in food trade, which results in a massive virtual transfer of water among regions and plays an important role in the food and water security of some regions. This review explores multiple components of the food-energy-water nexus and highlights possible approaches that could be used to meet food and energy security with the limited renewable water resources of the planet. Despite clear tensions inherent in meeting the growing and changing demand for food and energy in the 21st century, the inherent linkages among food, water, and energy systems can offer an opportunity for synergistic strategies aimed at resilient food, water, and energy security, such as the circular economy.

@article{bravo_interplay_2018,
	title = {The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: {A} latitudinal study across {Europe}},
	volume = {144},
	issn = {0043-1354},
	shorttitle = {The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems},
	url = {https://www.sciencedirect.com/science/article/pii/S0043135418305244},
	doi = {10.1016/j.watres.2018.06.064},
	abstract = {Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (\%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06–2.78 ng L−1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8–159 pg L−1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive \%MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.},
	urldate = {2024-03-26},
	journal = {Water Research},
	author = {Bravo, Andrea G. and Kothawala, Dolly N. and Attermeyer, Katrin and Tessier, Emmanuel and Bodmer, Pascal and Ledesma, José L. J. and Audet, Joachim and Casas-Ruiz, Joan Pere and Catalán, Núria and Cauvy-Fraunié, Sophie and Colls, Miriam and Deininger, Anne and Evtimova, Vesela V. and Fonvielle, Jérémy A. and Fuß, Thomas and Gilbert, Peter and Herrero Ortega, Sonia and Liu, Liu and Mendoza-Lera, Clara and Monteiro, Juliana and Mor, Jordi-René and Nagler, Magdalena and Niedrist, Georg H. and Nydahl, Anna C. and Pastor, Ada and Pegg, Josephine and Gutmann Roberts, Catherine and Pilotto, Francesca and Portela, Ana Paula and González-Quijano, Clara Romero and Romero, Ferran and Rulík, Martin and Amouroux, David},
	month = nov,
	year = {2018},
	keywords = {\#nosource, Fluorescence, Mercury, Methylmercury, Organic matter, Rivers, Streams},
	pages = {172--182},
}

Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06–2.78 ng L−1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8–159 pg L−1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.

@article{bognounou_role_2018,
	title = {Role of climate and herbivory on native and alien conifer seedling recruitment at and above the {Fennoscandian} tree line},
	volume = {29},
	copyright = {© 2018 International Association for Vegetation Science},
	issn = {1654-1103},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.12637},
	doi = {10.1111/jvs.12637},
	abstract = {Questions We investigated the importance of climate and herbivory on native and alien conifer colonization of the birch-dominated Fennoscandian tree line by addressing the following questions: (a) are tree line and tundra habitats similarly suitable for conifer seedling recruitment; (b) do ungulate and rodent herbivores differentially impact seedling recruitment; and (c) how does the role of habitat and herbivory on seedling recruitment vary across a marked climate gradient? Location Northern Fennoscandia, Sweden (Vassijaure and Paddus), and Norway (Joatka and Seiland). Methods We conducted an experiment to assess the emergence rate, survival probability and height development of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and Siberian larch (Larix sibirica) seedlings. Three experimental plots (i.e., open control, reindeer exclosure and complete vertebrate exclosure) were established in both tree line and tundra habitats at each of the four locations. Seeds of the three conifer species were sown in each plot in June 1999 during three consecutive years. The surviving seedlings were counted in August to September 1999, 2000, 2001, 2002 and 2007. The height of all seedlings was measured in 2007. Results Our study reveals that Norway spruce, Scots pine and Siberian larch can regenerate from seed at and above the current tree line in northern Fennoscandia. Their performance was generally higher above tree line in tundra than at tree line, but depended on species identity, climate aridity and mammal herbivory, particularly by rodents. These results suggest that the species composition and latitudinal limit of the tree line in the future might depend not only on direct effects of the future climate on the current tree line species, but also on the intensity of alien and native conifer introductions, as well as changes in herbivore populations. Conclusion If sufficient seeds of Norway spruce, Scots pine and Siberian larch should reach the current tree line, their performances will increase with a warmer and wetter climate, and this effect will be markedly modulated by herbivores (particularly rodents). Further work is required to extend these results to determine the ability of these conifers to become tree line-forming species in the future.},
	language = {en},
	number = {4},
	urldate = {2024-03-26},
	journal = {Journal of Vegetation Science},
	author = {Bognounou, Fidele and Hulme, Philip E. and Oksanen, Lauri and Suominen, Otso and Olofsson, Johan},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvs.12637},
	keywords = {\#nosource, biological invasions, conifer, exclosures, lemmings, propagule pressure, reindeer, seedling recruitment, seedling survival, tundra, vole},
	pages = {573--584},
}

Questions We investigated the importance of climate and herbivory on native and alien conifer colonization of the birch-dominated Fennoscandian tree line by addressing the following questions: (a) are tree line and tundra habitats similarly suitable for conifer seedling recruitment; (b) do ungulate and rodent herbivores differentially impact seedling recruitment; and (c) how does the role of habitat and herbivory on seedling recruitment vary across a marked climate gradient? Location Northern Fennoscandia, Sweden (Vassijaure and Paddus), and Norway (Joatka and Seiland). Methods We conducted an experiment to assess the emergence rate, survival probability and height development of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and Siberian larch (Larix sibirica) seedlings. Three experimental plots (i.e., open control, reindeer exclosure and complete vertebrate exclosure) were established in both tree line and tundra habitats at each of the four locations. Seeds of the three conifer species were sown in each plot in June 1999 during three consecutive years. The surviving seedlings were counted in August to September 1999, 2000, 2001, 2002 and 2007. The height of all seedlings was measured in 2007. Results Our study reveals that Norway spruce, Scots pine and Siberian larch can regenerate from seed at and above the current tree line in northern Fennoscandia. Their performance was generally higher above tree line in tundra than at tree line, but depended on species identity, climate aridity and mammal herbivory, particularly by rodents. These results suggest that the species composition and latitudinal limit of the tree line in the future might depend not only on direct effects of the future climate on the current tree line species, but also on the intensity of alien and native conifer introductions, as well as changes in herbivore populations. Conclusion If sufficient seeds of Norway spruce, Scots pine and Siberian larch should reach the current tree line, their performances will increase with a warmer and wetter climate, and this effect will be markedly modulated by herbivores (particularly rodents). Further work is required to extend these results to determine the ability of these conifers to become tree line-forming species in the future.

@article{bjorkman_tundra_2018,
	title = {Tundra {Trait} {Team}: {A} database of plant traits spanning the tundra biome},
	volume = {27},
	copyright = {© 2018 The Authors Global Ecology and Biogeography Published by John Wiley \& Sons Ltd},
	issn = {1466-8238},
	shorttitle = {Tundra {Trait} {Team}},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12821},
	doi = {10.1111/geb.12821},
	abstract = {Motivation The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits ({\textgreater} 1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99\% of observations are georeferenced. Time period and grain All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86\%), while the remainder represent plot or site means or maximums per species. Software format csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.},
	language = {en},
	number = {12},
	urldate = {2024-03-26},
	journal = {Global Ecology and Biogeography},
	author = {Bjorkman, Anne D. and Myers-Smith, Isla H. and Elmendorf, Sarah C. and Normand, Signe and Thomas, Haydn J. D. and Alatalo, Juha M. and Alexander, Heather and Anadon-Rosell, Alba and Angers-Blondin, Sandra and Bai, Yang and Baruah, Gaurav and te Beest, Mariska and Berner, Logan and Björk, Robert G. and Blok, Daan and Bruelheide, Helge and Buchwal, Agata and Buras, Allan and Carbognani, Michele and Christie, Katherine and Collier, Laura S. and Cooper, Elisabeth J. and Cornelissen, J. Hans C. and Dickinson, Katharine J. M. and Dullinger, Stefan and Elberling, Bo and Eskelinen, Anu and Forbes, Bruce C. and Frei, Esther R. and Iturrate-Garcia, Maitane and Good, Megan K. and Grau, Oriol and Green, Peter and Greve, Michelle and Grogan, Paul and Haider, Sylvia and Hájek, Tomáš and Hallinger, Martin and Happonen, Konsta and Harper, Karen A. and Heijmans, Monique M. P. D. and Henry, Gregory H. R. and Hermanutz, Luise and Hewitt, Rebecca E. and Hollister, Robert D. and Hudson, James and Hülber, Karl and Iversen, Colleen M. and Jaroszynska, Francesca and Jiménez-Alfaro, Borja and Johnstone, Jill and Jorgensen, Rasmus Halfdan and Kaarlejärvi, Elina and Klady, Rebecca and Klimešová, Jitka and Korsten, Annika and Kuleza, Sara and Kulonen, Aino and Lamarque, Laurent J. and Lantz, Trevor and Lavalle, Amanda and Lembrechts, Jonas J. and Lévesque, Esther and Little, Chelsea J. and Luoto, Miska and Macek, Petr and Mack, Michelle C. and Mathakutha, Rabia and Michelsen, Anders and Milbau, Ann and Molau, Ulf and Morgan, John W. and Mörsdorf, Martin Alfons and Nabe-Nielsen, Jacob and Nielsen, Sigrid Schøler and Ninot, Josep M. and Oberbauer, Steven F. and Olofsson, Johan and Onipchenko, Vladimir G. and Petraglia, Alessandro and Pickering, Catherine and Prevéy, Janet S. and Rixen, Christian and Rumpf, Sabine B. and Schaepman-Strub, Gabriela and Semenchuk, Philipp and Shetti, Rohan and Soudzilovskaia, Nadejda A. and Spasojevic, Marko J. and Speed, James David Mervyn and Street, Lorna E. and Suding, Katharine and Tape, Ken D. and Tomaselli, Marcello and Trant, Andrew and Treier, Urs A. and Tremblay, Jean-Pierre and Tremblay, Maxime and Venn, Susanna and Virkkala, Anna-Maria and Vowles, Tage and Weijers, Stef and Wilmking, Martin and Wipf, Sonja and Zamin, Tara},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/geb.12821},
	keywords = {\#nosource, Arctic, alpine, plant functional traits, tundra},
	pages = {1402--1411},
}

Motivation The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (\textgreater 1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.

@article{bakker_high_2018,
	title = {High {Grazing} {Pressure} of {Geese} {Threatens} {Conservation} and {Restoration} of {Reed} {Belts}},
	volume = {9},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01649/full},
	doi = {10.3389/fpls.2018.01649},
	abstract = {Reed (Phragmites australis Cav.) Trin. ex Steud.) beds are important habitat for marsh birds, but are declining throughout Europe. Increasing numbers of the native marsh bird, the Greylag goose ({\textless}italic{\textgreater}Anser anser{\textless}/italic{\textgreater} L.), are hypothesized to cause reed bed decline and inhibit restoration of reed beds, but data are largely lacking. In this study, we experimentally tested the effect of grazing by Greylag geese on the growth and expansion of reed growing in belts along lake shorelines. After 5 years of protecting reed from grazing with exclosures, reed stems were over 4-fold denser and taller than in the grazed plots. Grazing pressure was intense with 50–100\% of the stems being grazed among years in the control plots open to grazing. After 5 years of protection we opened half of the exclosures and the geese immediately grazed almost 100\% of the reed stems. Whereas this did not affect the reed stem density, the stem height was strongly reduced and similar to permanently grazed reed. The next year geese were actively chased away by management from mid-March to mid-June, which changed the maximum amount of geese from over 2300 to less than 50. As a result, reed stem density and height increased and the reed belt had recovered over the full 6 m length of the experimental plots. Lastly, we introduced reed plants in an adjacent lake where no reed was growing and geese did visit this area. After two years, the density of the planted reed was six to nine-fold higher and significantly taller in exclosures compared to control plots where geese had access to the reed plants. We conclude that there is a conservation dilemma regarding how to preserve and restore reed belts in the presence of high densities of Greylag geese as conservation of both reed belts and high goose numbers seems infeasible. We suggest that there are three possible solutions for this dilemma: (1) effects of the geese can be mediated by goose population management, (2) the robustness of the reed marshes can be increased, and (3) at the landscape level, spatial planning can be used to configure landscapes with large reed bed reserves surrounded by unmown, unfertilized meadows.},
	language = {English},
	urldate = {2024-03-26},
	journal = {Frontiers in Plant Science},
	author = {Bakker, Elisabeth S. and Veen, Ciska G. F. and Ter Heerdt, Gerard J. N. and Huig, Naomi and Sarneel, Judith M.},
	month = nov,
	year = {2018},
	note = {Publisher: Frontiers},
	keywords = {Anser anser, Aquatic plant, Exclosure, Herbivory, Landscape configuration, Phragmites australis, restoration, wetland},
	pages = {1649},
}

Reed (Phragmites australis Cav.) Trin. ex Steud.) beds are important habitat for marsh birds, but are declining throughout Europe. Increasing numbers of the native marsh bird, the Greylag goose (\textlessitalic\textgreaterAnser anser\textless/italic\textgreater L.), are hypothesized to cause reed bed decline and inhibit restoration of reed beds, but data are largely lacking. In this study, we experimentally tested the effect of grazing by Greylag geese on the growth and expansion of reed growing in belts along lake shorelines. After 5 years of protecting reed from grazing with exclosures, reed stems were over 4-fold denser and taller than in the grazed plots. Grazing pressure was intense with 50–100% of the stems being grazed among years in the control plots open to grazing. After 5 years of protection we opened half of the exclosures and the geese immediately grazed almost 100% of the reed stems. Whereas this did not affect the reed stem density, the stem height was strongly reduced and similar to permanently grazed reed. The next year geese were actively chased away by management from mid-March to mid-June, which changed the maximum amount of geese from over 2300 to less than 50. As a result, reed stem density and height increased and the reed belt had recovered over the full 6 m length of the experimental plots. Lastly, we introduced reed plants in an adjacent lake where no reed was growing and geese did visit this area. After two years, the density of the planted reed was six to nine-fold higher and significantly taller in exclosures compared to control plots where geese had access to the reed plants. We conclude that there is a conservation dilemma regarding how to preserve and restore reed belts in the presence of high densities of Greylag geese as conservation of both reed belts and high goose numbers seems infeasible. We suggest that there are three possible solutions for this dilemma: (1) effects of the geese can be mediated by goose population management, (2) the robustness of the reed marshes can be increased, and (3) at the landscape level, spatial planning can be used to configure landscapes with large reed bed reserves surrounded by unmown, unfertilized meadows.

@article{alexander_lags_2018,
	title = {Lags in the response of mountain plant communities to climate change},
	volume = {24},
	copyright = {© 2017 John Wiley \& Sons Ltd},
	issn = {1365-2486},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13976},
	doi = {10.1111/gcb.13976},
	abstract = {Rapid climatic changes and increasing human influence at high elevations around the world will have profound impacts on mountain biodiversity. However, forecasts from statistical models (e.g. species distribution models) rarely consider that plant community changes could substantially lag behind climatic changes, hindering our ability to make temporally realistic projections for the coming century. Indeed, the magnitudes of lags, and the relative importance of the different factors giving rise to them, remain poorly understood. We review evidence for three types of lag: “dispersal lags” affecting plant species’ spread along elevational gradients, “establishment lags” following their arrival in recipient communities, and “extinction lags” of resident species. Variation in lags is explained by variation among species in physiological and demographic responses, by effects of altered biotic interactions, and by aspects of the physical environment. Of these, altered biotic interactions could contribute substantially to establishment and extinction lags, yet impacts of biotic interactions on range dynamics are poorly understood. We develop a mechanistic community model to illustrate how species turnover in future communities might lag behind simple expectations based on species’ range shifts with unlimited dispersal. The model shows a combined contribution of altered biotic interactions and dispersal lags to plant community turnover along an elevational gradient following climate warming. Our review and simulation support the view that accounting for disequilibrium range dynamics will be essential for realistic forecasts of patterns of biodiversity under climate change, with implications for the conservation of mountain species and the ecosystem functions they provide.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Global Change Biology},
	author = {Alexander, Jake M. and Chalmandrier, Loïc and Lenoir, Jonathan and Burgess, Treena I. and Essl, Franz and Haider, Sylvia and Kueffer, Christoph and McDougall, Keith and Milbau, Ann and Nuñez, Martin A. and Pauchard, Aníbal and Rabitsch, Wolfgang and Rew, Lisa J. and Sanders, Nathan J. and Pellissier, Loïc},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13976},
	keywords = {\#nosource, alpine ecosystems, biotic interactions, climate change, climatic debt, migration, novel interactions, range dynamics, range expansion},
	pages = {563--579},
}

Rapid climatic changes and increasing human influence at high elevations around the world will have profound impacts on mountain biodiversity. However, forecasts from statistical models (e.g. species distribution models) rarely consider that plant community changes could substantially lag behind climatic changes, hindering our ability to make temporally realistic projections for the coming century. Indeed, the magnitudes of lags, and the relative importance of the different factors giving rise to them, remain poorly understood. We review evidence for three types of lag: “dispersal lags” affecting plant species’ spread along elevational gradients, “establishment lags” following their arrival in recipient communities, and “extinction lags” of resident species. Variation in lags is explained by variation among species in physiological and demographic responses, by effects of altered biotic interactions, and by aspects of the physical environment. Of these, altered biotic interactions could contribute substantially to establishment and extinction lags, yet impacts of biotic interactions on range dynamics are poorly understood. We develop a mechanistic community model to illustrate how species turnover in future communities might lag behind simple expectations based on species’ range shifts with unlimited dispersal. The model shows a combined contribution of altered biotic interactions and dispersal lags to plant community turnover along an elevational gradient following climate warming. Our review and simulation support the view that accounting for disequilibrium range dynamics will be essential for realistic forecasts of patterns of biodiversity under climate change, with implications for the conservation of mountain species and the ecosystem functions they provide.

@article{ala-aho_permafrost_2018,
	title = {Permafrost and lakes control river isotope composition across a boreal {Arctic} transect in the {Western} {Siberian} lowlands},
	volume = {13},
	issn = {1748-9326},
	url = {https://dx.doi.org/10.1088/1748-9326/aaa4fe},
	doi = {10.1088/1748-9326/aaa4fe},
	abstract = {The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South–North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10–105 km2) and permafrost coverage (0\%–70\%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.},
	language = {en},
	number = {3},
	urldate = {2024-03-26},
	journal = {Environmental Research Letters},
	author = {Ala-aho, P. and Soulsby, C. and Pokrovsky, O. S. and Kirpotin, S. N. and Karlsson, J. and Serikova, S. and Manasypov, R. and Lim, A. and Krickov, I. and Kolesnichenko, L. G. and Laudon, H. and Tetzlaff, D.},
	month = feb,
	year = {2018},
	note = {Publisher: IOP Publishing},
	keywords = {\#nosource},
	pages = {034028},
}

The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South–North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10–105 km2) and permafrost coverage (0%–70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.

@article{adolf_sedimentary_2018,
	title = {The sedimentary and remote-sensing reflection of biomass burning in {Europe}},
	volume = {27},
	copyright = {© 2017 John Wiley \& Sons Ltd},
	issn = {1466-8238},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12682},
	doi = {10.1111/geb.12682},
	abstract = {Aim We provide the first European-scale geospatial training set relating the charcoal signal in surface lake sediments to fire parameters (number, intensity and area) recorded by satellite moderate resolution imaging spectroradiometer (MODIS) sensors. Our calibration is intended for quantitative reconstructions of key fire-regime parameters by using sediment sequences of microscopic (MIC from pollen slides, particles 10–500 µm) and macroscopic charcoal (MAC from sieves, particles {\textgreater} 100 µm). Location North–south and east–west transects across Europe, covering the mediterranean, temperate, alpine, boreal and steppe biomes. Time period Lake sediments and MODIS active fire and burned area products were collected for the years 2012–2015. Methods Cylinder sediment traps were installed in lakes to annually collect charcoal particles in sediments. We quantitatively assessed the relationships between MIC and MAC influx (particles/cm2/year) and the MODIS-derived products to identify source areas of charcoal and the extent to which lake-sediment charcoal is linked to fire parameters across the continent. Results Source area of sedimentary charcoal was estimated to a 40-km radius around sites for both MIC and MAC particles. Fires occurred in grasslands and in forests, with grass morphotypes of MAC accurately reflecting the burned fuel-type. Despite the lack of local fires around the sites, MAC influx levels reached those reported for local fires. Both MIC and MAC showed strong and highly significant relationships with the MODIS-derived fire parameters, as well as with climatic variation along a latitudinal temperature gradient. Main conclusions MIC and MAC are suited to quantitatively reconstructing fire number and fire intensity on a regional scale. However, burned area may only be estimated using MAC. Local fires may be identified by using several lines of evidence, e.g. analysis of large particles ({\textgreater} 600 µm), magnetic susceptibility and sedimentological data. Our results offer new insights and applications to quantitatively reconstruct fires and to interpret available sedimentary charcoal records.},
	language = {en},
	number = {2},
	urldate = {2024-03-26},
	journal = {Global Ecology and Biogeography},
	author = {Adolf, Carole and Wunderle, Stefan and Colombaroli, Daniele and Weber, Helga and Gobet, Erika and Heiri, Oliver and van Leeuwen, Jacqueline F. N. and Bigler, Christian and Connor, Simon E. and Gałka, Mariusz and La Mantia, Tommaso and Makhortykh, Sergey and Svitavská-Svobodová, Helena and Vannière, Boris and Tinner, Willy},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/geb.12682},
	keywords = {\#nosource, MODIS, calibration in space, fire ecology, fire regime, lake-sediment charcoal, palaeoecology},
	pages = {199--212},
}

Aim We provide the first European-scale geospatial training set relating the charcoal signal in surface lake sediments to fire parameters (number, intensity and area) recorded by satellite moderate resolution imaging spectroradiometer (MODIS) sensors. Our calibration is intended for quantitative reconstructions of key fire-regime parameters by using sediment sequences of microscopic (MIC from pollen slides, particles 10–500 µm) and macroscopic charcoal (MAC from sieves, particles \textgreater 100 µm). Location North–south and east–west transects across Europe, covering the mediterranean, temperate, alpine, boreal and steppe biomes. Time period Lake sediments and MODIS active fire and burned area products were collected for the years 2012–2015. Methods Cylinder sediment traps were installed in lakes to annually collect charcoal particles in sediments. We quantitatively assessed the relationships between MIC and MAC influx (particles/cm2/year) and the MODIS-derived products to identify source areas of charcoal and the extent to which lake-sediment charcoal is linked to fire parameters across the continent. Results Source area of sedimentary charcoal was estimated to a 40-km radius around sites for both MIC and MAC particles. Fires occurred in grasslands and in forests, with grass morphotypes of MAC accurately reflecting the burned fuel-type. Despite the lack of local fires around the sites, MAC influx levels reached those reported for local fires. Both MIC and MAC showed strong and highly significant relationships with the MODIS-derived fire parameters, as well as with climatic variation along a latitudinal temperature gradient. Main conclusions MIC and MAC are suited to quantitatively reconstructing fire number and fire intensity on a regional scale. However, burned area may only be estimated using MAC. Local fires may be identified by using several lines of evidence, e.g. analysis of large particles (\textgreater 600 µm), magnetic susceptibility and sedimentological data. Our results offer new insights and applications to quantitatively reconstruct fires and to interpret available sedimentary charcoal records.

@article{granath_environmental_2018,
	title = {Environmental and taxonomic controls of carbon and oxygen stable isotope composition in \textit{{Sphagnum}} across broad climatic and geographic ranges},
	volume = {15},
	issn = {1726-4170},
	url = {https://www.biogeosciences.net/15/5189/2018/bg-15-5189-2018.html},
	doi = {10.5194/bg-15-5189-2018},
	abstract = {{\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} Rain-fed peatlands are dominated by peat mosses (\textit{Sphagnum} sp.), which for their growth depend on nutrients, water and CO$_{\textrm{2}}$ uptake from the atmosphere. As the isotopic composition of carbon ($^{\textrm{12,13}}$C) and oxygen ($^{\textrm{16,18}}$O) of these \textit{Sphagnum} mosses are affected by environmental conditions, \textit{Sphagnum} tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is inadequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of \textit{Sphagnum} is species-specific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation) and elevation; (ii) whether the C isotopic signature can be a proxy for net primary productivity (NPP) of \textit{Sphagnum}; and (iii) to what extent \textit{Sphagnum} tissue \textit{δ}$^{\textrm{18}}$O tracks the \textit{δ}$^{\textrm{18}}$O isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia using two important peat-forming \textit{Sphagnum }species (\textit{S. magellanicum}, \textit{S. fuscum}) common to the Holarctic realm. There were differences in \textit{δ}$^{\textrm{13}}$C values between species. For \textit{S. magellanicum} \textit{δ}$^{\textrm{13}}$C decreased with increasing height above the water table (HWT, \textit{R}$^{\textrm{2}}$ = 17{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\%) and was positively correlated to productivity (\textit{R}$^{\textrm{2}}$ = 7{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\%). Together these two variables explained 46{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\% of the between-site variation in \textit{δ}$^{\textrm{13}}$C values. For \textit{S. fuscum}, productivity was the only significant predictor of \textit{δ}$^{\textrm{13}}$C but had low explanatory power (total \textit{R}$^{\textrm{2}}$ = 6{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\%). For \textit{δ}$^{\textrm{18}}$O values, approximately 90{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\% of the variation was found between sites. Globally modelled annual \textit{δ}$^{\textrm{18}}$O values in precipitation explained 69{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\% of the between-site variation in tissue \textit{δ}$^{\textrm{18}}$O. \textit{S. magellanicum} showed lower \textit{δ}$^{\textrm{18}}$O enrichment than \textit{S. fuscum} (−0.83{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}‰ lower). Elevation and climatic variables were weak predictors of tissue \textit{δ}$^{\textrm{18}}$O values after controlling for \textit{δ}$^{\textrm{18}}$O values of the precipitation. To summarize, our study provides evidence for (a) good predictability of tissue \textit{δ}$^{\textrm{18}}$O values from modelled annual \textit{δ}$^{\textrm{18}}$O values in precipitation, and (b) the possibility of relating tissue \textit{δ}$^{\textrm{13}}$C values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used on a large scale for climatic reconstructions but that such models should be species-specific.{\textless}/p{\textgreater}},
	language = {English},
	number = {16},
	urldate = {2018-09-17},
	journal = {Biogeosciences},
	author = {Granath, Gustaf and Rydin, Håkan and Baltzer, Jennifer L. and Bengtsson, Fia and Boncek, Nicholas and Bragazza, Luca and Bu, Zhao-Jun and Caporn, Simon J. M. and Dorrepaal, Ellen and Galanina, Olga and Gałka, Mariusz and Ganeva, Anna and Gillikin, David P. and Goia, Irina and Goncharova, Nadezhda and Hájek, Michal and Haraguchi, Akira and Harris, Lorna I. and Humphreys, Elyn and Jiroušek, Martin and Kajukało, Katarzyna and Karofeld, Edgar and Koronatova, Natalia G. and Kosykh, Natalia P. and Lamentowicz, Mariusz and Lapshina, Elena and Limpens, Juul and Linkosalmi, Maiju and Ma, Jin-Ze and Mauritz, Marguerite and Munir, Tariq M. and Natali, Susan M. and Natcheva, Rayna and Noskova, Maria and Payne, Richard J. and Pilkington, Kyle and Robinson, Sean and Robroek, Bjorn J. M. and Rochefort, Line and Singer, David and Stenøien, Hans K. and Tuittila, Eeva-Stiina and Vellak, Kai and Verheyden, Anouk and Waddington, James Michael and Rice, Steven K.},
	month = aug,
	year = {2018},
	note = {00000},
	keywords = {\#nosource},
	pages = {5189--5202},
}

\textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on nutrients, water and CO$_{\textrm{2}}$ uptake from the atmosphere. As the isotopic composition of carbon ($^{\textrm{12,13}}$C) and oxygen ($^{\textrm{16,18}}$O) of these Sphagnum mosses are affected by environmental conditions, Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is inadequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is species-specific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation) and elevation; (ii) whether the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue δ$^{\textrm{18}}$O tracks the δ$^{\textrm{18}}$O isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia using two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holarctic realm. There were differences in δ$^{\textrm{13}}$C values between species. For S. magellanicum δ$^{\textrm{13}}$C decreased with increasing height above the water table (HWT, R$^{\textrm{2}}$ = 17\textlessspan class="thinspace"\textgreater\textless/span\textgreater%) and was positively correlated to productivity (R$^{\textrm{2}}$ = 7\textlessspan class="thinspace"\textgreater\textless/span\textgreater%). Together these two variables explained 46\textlessspan class="thinspace"\textgreater\textless/span\textgreater% of the between-site variation in δ$^{\textrm{13}}$C values. For S. fuscum, productivity was the only significant predictor of δ$^{\textrm{13}}$C but had low explanatory power (total R$^{\textrm{2}}$ = 6\textlessspan class="thinspace"\textgreater\textless/span\textgreater%). For δ$^{\textrm{18}}$O values, approximately 90\textlessspan class="thinspace"\textgreater\textless/span\textgreater% of the variation was found between sites. Globally modelled annual δ$^{\textrm{18}}$O values in precipitation explained 69\textlessspan class="thinspace"\textgreater\textless/span\textgreater% of the between-site variation in tissue δ$^{\textrm{18}}$O. S. magellanicum showed lower δ$^{\textrm{18}}$O enrichment than S. fuscum (−0.83\textlessspan class="thinspace"\textgreater\textless/span\textgreater‰ lower). Elevation and climatic variables were weak predictors of tissue δ$^{\textrm{18}}$O values after controlling for δ$^{\textrm{18}}$O values of the precipitation. To summarize, our study provides evidence for (a) good predictability of tissue δ$^{\textrm{18}}$O values from modelled annual δ$^{\textrm{18}}$O values in precipitation, and (b) the possibility of relating tissue δ$^{\textrm{13}}$C values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used on a large scale for climatic reconstructions but that such models should be species-specific.\textless/p\textgreater

@article{krickov_riverine_2018,
	title = {Riverine particulate {C} and {N} generated at the permafrost thaw front: case study of western {Siberian} rivers across a 1700\ km latitudinal transect},
	volume = {15},
	issn = {1726-4170},
	shorttitle = {Riverine particulate {C} and {N} generated at the permafrost thaw front},
	url = {https://www.biogeosciences.net/15/6867/2018/},
	doi = {10.5194/bg-15-6867-2018},
	abstract = {{\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} In contrast to numerous studies on the dynamics of dissolved ( \< 0.45{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}µm) elements in permafrost-affected high-latitude rivers, very little is known of the behavior of river suspended ( \> 0.45{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}µm) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physio-geographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentrations in river water, we sampled 33 small and medium-sized rivers (10–100{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}000{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}km$^{\textrm{2}}$ watershed) along a 1700{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}km N–S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL). The concentrations of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in the RSM. The C : N ratio in the RSM reflected the source from the deep soil horizon rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of both particulate C and N concentrations and export fluxes at the beginning of permafrost appearance, in the sporadic and discontinuous zone (62–64°{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}N). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentrations in RSM by 2 to 3 times.{\textless}/p{\textgreater}},
	language = {English},
	number = {22},
	urldate = {2018-11-27},
	journal = {Biogeosciences},
	author = {Krickov, Ivan V. and Lim, Artem G. and Manasypov, Rinat M. and Loiko, Sergey V. and Shirokova, Liudmila S. and Kirpotin, Sergey N. and Karlsson, Jan and Pokrovsky, Oleg S.},
	month = nov,
	year = {2018},
	keywords = {\#nosource},
	pages = {6867--6884},
}

\textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater In contrast to numerous studies on the dynamics of dissolved ( < 0.45\textlessspan class="thinspace"\textgreater\textless/span\textgreaterµm) elements in permafrost-affected high-latitude rivers, very little is known of the behavior of river suspended ( > 0.45\textlessspan class="thinspace"\textgreater\textless/span\textgreaterµm) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physio-geographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentrations in river water, we sampled 33 small and medium-sized rivers (10–100\textlessspan class="thinspace"\textgreater\textless/span\textgreater000\textlessspan class="thinspace"\textgreater\textless/span\textgreaterkm$^{\textrm{2}}$ watershed) along a 1700\textlessspan class="thinspace"\textgreater\textless/span\textgreaterkm N–S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL). The concentrations of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in the RSM. The C : N ratio in the RSM reflected the source from the deep soil horizon rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of both particulate C and N concentrations and export fluxes at the beginning of permafrost appearance, in the sporadic and discontinuous zone (62–64°\textlessspan class="thinspace"\textgreater\textless/span\textgreaterN). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentrations in RSM by 2 to 3 times.\textless/p\textgreater

@article{walz_greenhouse_2018,
	title = {Greenhouse gas production in degrading ice-rich permafrost deposits in northeastern {Siberia}},
	volume = {15},
	issn = {1726-4170},
	url = {https://www.biogeosciences.net/15/5423/2018/},
	doi = {10.5194/bg-15-5423-2018},
	abstract = {{\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} Permafrost deposits have been a sink for atmospheric carbon for millennia. Thaw-erosional processes, however, can lead to rapid degradation of ice-rich permafrost and the release of substantial amounts of organic carbon (OC). The amount of the OC stored in these deposits and their potential to be microbially decomposed to the greenhouse gases carbon dioxide ({\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater}) and methane ({\textless}span class="inline-formula"{\textgreater}CH$_{\textrm{4}}${\textless}/span{\textgreater}) depends on climatic and environmental conditions during deposition and the decomposition history before incorporation into the permafrost. Here, we examine potential greenhouse gas production as a result of degrading ice-rich permafrost deposits from three locations in the northeastern Siberian Laptev Sea region. The deposits span a period of about 55\ kyr from the last glacial period and Holocene interglacial. Samples from all three locations were incubated under aerobic and anaerobic conditions for 134 days at 4\ {\textless}span class="inline-formula"{\textgreater}$^{\textrm{∘}}${\textless}/span{\textgreater}C. Greenhouse gas production was generally higher in deposits from glacial periods, where 0.2\ \%–6.1\ \% of the initially available OC was decomposed to {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater}. In contrast, only 0.1\ \%–4.0\ \% of initial OC was decomposed in permafrost deposits from the Holocene and the late glacial transition. Within the deposits from the Kargin interstadial period (Marine Isotope Stage 3), local depositional environments, especially soil moisture, also affected the preservation of OC. Sediments deposited under wet conditions contained more labile OC and thus produced more greenhouse gases than sediments deposited under drier conditions. To assess the greenhouse gas production potentials over longer periods, deposits from two locations were incubated for a total of 785 days. However, more than 50\ \% of total {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater} production over 785 days occurred within the first 134 days under aerobic conditions, while 80\ \% were produced over the same period under anaerobic conditions, which emphasizes the nonlinearity of the OC decomposition processes. Methanogenesis was generally observed in active layer samples but only sporadically in permafrost samples and was several orders of magnitude smaller than {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater} production.{\textless}/p{\textgreater}},
	language = {English},
	number = {17},
	urldate = {2020-06-10},
	journal = {Biogeosciences},
	author = {Walz, Josefine and Knoblauch, Christian and Tigges, Ronja and Opel, Thomas and Schirrmeister, Lutz and Pfeiffer, Eva-Maria},
	month = sep,
	year = {2018},
	note = {Publisher: Copernicus GmbH},
	keywords = {\#nosource},
	pages = {5423--5436},
}

\textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater Permafrost deposits have been a sink for atmospheric carbon for millennia. Thaw-erosional processes, however, can lead to rapid degradation of ice-rich permafrost and the release of substantial amounts of organic carbon (OC). The amount of the OC stored in these deposits and their potential to be microbially decomposed to the greenhouse gases carbon dioxide (\textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater) and methane (\textlessspan class="inline-formula"\textgreaterCH$_{\textrm{4}}$\textless/span\textgreater) depends on climatic and environmental conditions during deposition and the decomposition history before incorporation into the permafrost. Here, we examine potential greenhouse gas production as a result of degrading ice-rich permafrost deposits from three locations in the northeastern Siberian Laptev Sea region. The deposits span a period of about 55 kyr from the last glacial period and Holocene interglacial. Samples from all three locations were incubated under aerobic and anaerobic conditions for 134 days at 4 \textlessspan class="inline-formula"\textgreater$^{\textrm{∘}}$\textless/span\textgreaterC. Greenhouse gas production was generally higher in deposits from glacial periods, where 0.2 %–6.1 % of the initially available OC was decomposed to \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater. In contrast, only 0.1 %–4.0 % of initial OC was decomposed in permafrost deposits from the Holocene and the late glacial transition. Within the deposits from the Kargin interstadial period (Marine Isotope Stage 3), local depositional environments, especially soil moisture, also affected the preservation of OC. Sediments deposited under wet conditions contained more labile OC and thus produced more greenhouse gases than sediments deposited under drier conditions. To assess the greenhouse gas production potentials over longer periods, deposits from two locations were incubated for a total of 785 days. However, more than 50 % of total \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater production over 785 days occurred within the first 134 days under aerobic conditions, while 80 % were produced over the same period under anaerobic conditions, which emphasizes the nonlinearity of the OC decomposition processes. Methanogenesis was generally observed in active layer samples but only sporadically in permafrost samples and was several orders of magnitude smaller than \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater production.\textless/p\textgreater

@article{weston_sphagnome_2018,
	title = {The {Sphagnome} {Project}: enabling ecological and evolutionary insights through a genus-level sequencing project},
	volume = {217},
	issn = {0028-646X},
	url = {https://doi.org/10.1111/nph.14860},
	doi = {10.1111/nph.14860},
	abstract = {Summary Considerable progress has been made in ecological and evolutionary genetics with studies demonstrating how genes underlying plant and microbial traits can influence adaptation and even ?extend? to influence community structure and ecosystem level processes. Progress in this area is limited to model systems with deep genetic and genomic resources that often have negligible ecological impact or interest. Thus, important linkages between genetic adaptations and their consequences at organismal and ecological scales are often lacking. Here we introduce the Sphagnome Project, which incorporates genomics into a long-running history of Sphagnum research that has documented unparalleled contributions to peatland ecology, carbon sequestration, biogeochemistry, microbiome research, niche construction, and ecosystem engineering. The Sphagnome Project encompasses a genus-level sequencing effort that represents a new type of model system driven not only by genetic tractability, but by ecologically relevant questions and hypotheses.},
	number = {1},
	urldate = {2023-07-21},
	journal = {New Phytologist},
	author = {Weston, David J. and Turetsky, Merritt R. and Johnson, Matthew G. and Granath, Gustaf and Lindo, Zoë and Belyea, Lisa R. and Rice, Steven K. and Hanson, David T. and Engelhardt, Katharina A. M. and Schmutz, Jeremy and Dorrepaal, Ellen and Euskirchen, Eugénie S. and Stenøien, Hans K. and Szövényi, Péter and Jackson, Michelle and Piatkowski, Bryan T. and Muchero, Wellington and Norby, Richard J. and Kostka, Joel E. and Glass, Jennifer B. and Rydin, Håkan and Limpens, Juul and Tuittila, Eeva-Stiina and Ullrich, Kristian K. and Carrell, Alyssa and Benscoter, Brian W. and Chen, Jin-Gui and Oke, Tobi A. and Nilsson, Mats B. and Ranjan, Priya and Jacobson, Daniel and Lilleskov, Erik A. and Clymo, R. S. and Shaw, A. Jonathan},
	month = jan,
	year = {2018},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, Sphagnome, Sphagnum, ecological genomics, ecosystem engineering, evolutionary genetics, genome sequencing, niche construction, peatlands},
	pages = {16--25},
}

Summary Considerable progress has been made in ecological and evolutionary genetics with studies demonstrating how genes underlying plant and microbial traits can influence adaptation and even ?extend? to influence community structure and ecosystem level processes. Progress in this area is limited to model systems with deep genetic and genomic resources that often have negligible ecological impact or interest. Thus, important linkages between genetic adaptations and their consequences at organismal and ecological scales are often lacking. Here we introduce the Sphagnome Project, which incorporates genomics into a long-running history of Sphagnum research that has documented unparalleled contributions to peatland ecology, carbon sequestration, biogeochemistry, microbiome research, niche construction, and ecosystem engineering. The Sphagnome Project encompasses a genus-level sequencing effort that represents a new type of model system driven not only by genetic tractability, but by ecologically relevant questions and hypotheses.

@article{ramirez_detecting_2018,
	title = {Detecting macroecological patterns in bacterial communities across independent studies of global soils},
	volume = {3},
	issn = {2058-5276},
	url = {https://doi.org/10.1038/s41564-017-0062-x},
	doi = {10.1038/s41564-017-0062-x},
	abstract = {The emergence of high-throughput DNA sequencing methods provides unprecedented opportunities to further unravel bacterial biodiversity and its worldwide role from human health to ecosystem functioning. However, despite the abundance of sequencing studies, combining data from multiple individual studies to address macroecological questions of bacterial diversity remains methodically challenging and plagued with biases. Here, using a machine-learning approach that accounts for differences among studies and complex interactions among taxa, we merge 30 independent bacterial data sets comprising 1,998 soil samples from 21 countries. Whereas previous meta-analysis efforts have focused on bacterial diversity measures or abundances of major taxa, we show that disparate amplicon sequence data can be combined at the taxonomy-based level to assess bacterial community structure. We find that rarer taxa are more important for structuring soil communities than abundant taxa, and that these rarer taxa are better predictors of community structure than environmental factors, which are often confounded across studies. We conclude that combining data from independent studies can be used to explore bacterial community dynamics, identify potential ‘indicator’ taxa with an important role in structuring communities, and propose hypotheses on the factors that shape bacterial biogeography that have been overlooked in the past.},
	number = {2},
	journal = {Nature Microbiology},
	author = {Ramirez, Kelly S. and Knight, Christopher G. and de Hollander, Mattias and Brearley, Francis Q. and Constantinides, Bede and Cotton, Anne and Creer, Si and Crowther, Thomas W. and Davison, John and Delgado-Baquerizo, Manuel and Dorrepaal, Ellen and Elliott, David R. and Fox, Graeme and Griffiths, Robert I. and Hale, Chris and Hartman, Kyle and Houlden, Ashley and Jones, David L. and Krab, Eveline J. and Maestre, Fernando T. and McGuire, Krista L. and Monteux, Sylvain and Orr, Caroline H. and van der Putten, Wim H. and Roberts, Ian S. and Robinson, David A. and Rocca, Jennifer D. and Rowntree, Jennifer and Schlaeppi, Klaus and Shepherd, Matthew and Singh, Brajesh K. and Straathof, Angela L. and Bhatnagar, Jennifer M. and Thion, Cécile and van der Heijden, Marcel G. A. and de Vries, Franciska T.},
	month = feb,
	year = {2018},
	keywords = {\#nosource},
	pages = {189--196},
}

The emergence of high-throughput DNA sequencing methods provides unprecedented opportunities to further unravel bacterial biodiversity and its worldwide role from human health to ecosystem functioning. However, despite the abundance of sequencing studies, combining data from multiple individual studies to address macroecological questions of bacterial diversity remains methodically challenging and plagued with biases. Here, using a machine-learning approach that accounts for differences among studies and complex interactions among taxa, we merge 30 independent bacterial data sets comprising 1,998 soil samples from 21 countries. Whereas previous meta-analysis efforts have focused on bacterial diversity measures or abundances of major taxa, we show that disparate amplicon sequence data can be combined at the taxonomy-based level to assess bacterial community structure. We find that rarer taxa are more important for structuring soil communities than abundant taxa, and that these rarer taxa are better predictors of community structure than environmental factors, which are often confounded across studies. We conclude that combining data from independent studies can be used to explore bacterial community dynamics, identify potential ‘indicator’ taxa with an important role in structuring communities, and propose hypotheses on the factors that shape bacterial biogeography that have been overlooked in the past.

@article{gavazov_vascular_2018,
	title = {Vascular plant-mediated controls on atmospheric carbon assimilation and peat carbon decomposition under climate change},
	volume = {24},
	issn = {1354-1013},
	url = {https://doi.org/10.1111/gcb.14140},
	doi = {10.1111/gcb.14140},
	abstract = {Abstract Climate change can alter peatland plant community composition by promoting the growth of vascular plants. How such vegetation change affects peatland carbon dynamics remains, however, unclear. In order to assess the effect of vegetation change on carbon uptake and release, we performed a vascular plant-removal experiment in two Sphagnum-dominated peatlands that represent contrasting stages of natural vegetation succession along a climatic gradient. Periodic measurements of net ecosystem CO2 exchange revealed that vascular plants play a crucial role in assuring the potential for net carbon uptake, particularly with a warmer climate. The presence of vascular plants, however, also increased ecosystem respiration, and by using the seasonal variation of respired CO2 radiocarbon (bomb-14C) signature we demonstrate an enhanced heterotrophic decomposition of peat carbon due to rhizosphere priming. The observed rhizosphere priming of peat carbon decomposition was matched by more advanced humification of dissolved organic matter, which remained apparent beyond the plant growing season. Our results underline the relevance of rhizosphere priming in peatlands, especially when assessing the future carbon sink function of peatlands undergoing a shift in vegetation community composition in association with climate change.},
	number = {9},
	urldate = {2023-07-21},
	journal = {Global Change Biology},
	author = {Gavazov, Konstantin and Albrecht, Remy and Buttler, Alexandre and Dorrepaal, Ellen and Garnett, Mark H. and Gogo, Sebastien and Hagedorn, Frank and Mills, Robert T. E. and Robroek, Bjorn J. M. and Bragazza, Luca},
	month = sep,
	year = {2018},
	note = {Publisher: John Wiley \& Sons, Ltd},
	keywords = {\#nosource, climate warming, decomposition, ecosystem respiration, elevation gradient, net ecosystem CO2 exchange, peatlands, rhizosphere priming, vascular plant biomass},
	pages = {3911--3921},
}

Abstract Climate change can alter peatland plant community composition by promoting the growth of vascular plants. How such vegetation change affects peatland carbon dynamics remains, however, unclear. In order to assess the effect of vegetation change on carbon uptake and release, we performed a vascular plant-removal experiment in two Sphagnum-dominated peatlands that represent contrasting stages of natural vegetation succession along a climatic gradient. Periodic measurements of net ecosystem CO2 exchange revealed that vascular plants play a crucial role in assuring the potential for net carbon uptake, particularly with a warmer climate. The presence of vascular plants, however, also increased ecosystem respiration, and by using the seasonal variation of respired CO2 radiocarbon (bomb-14C) signature we demonstrate an enhanced heterotrophic decomposition of peat carbon due to rhizosphere priming. The observed rhizosphere priming of peat carbon decomposition was matched by more advanced humification of dissolved organic matter, which remained apparent beyond the plant growing season. Our results underline the relevance of rhizosphere priming in peatlands, especially when assessing the future carbon sink function of peatlands undergoing a shift in vegetation community composition in association with climate change.

@article{monteux_long-term_2018,
	title = {Long-term in situ permafrost thaw effects on bacterial communities and potential aerobic respiration},
	volume = {12},
	issn = {1751-7370},
	url = {https://doi.org/10.1038/s41396-018-0176-z},
	doi = {10.1038/s41396-018-0176-z},
	abstract = {The decomposition of large stocks of soil organic carbon in thawing permafrost might depend on more than climate change-induced temperature increases: indirect effects of thawing via altered bacterial community structure (BCS) or rooting patterns are largely unexplored. We used a 10-year in situ permafrost thaw experiment and aerobic incubations to investigate alterations in BCS and potential respiration at different depths, and the extent to which they are related with each other and with root density. Active layer and permafrost BCS strongly differed, and the BCS in formerly frozen soils (below the natural thawfront) converged under induced deep thaw to strongly resemble the active layer BCS, possibly as a result of colonization by overlying microorganisms. Overall, respiration rates decreased with depth and soils showed lower potential respiration when subjected to deeper thaw, which we attributed to gradual labile carbon pool depletion. Despite deeper rooting under induced deep thaw, root density measurements did not improve soil chemistry-based models of potential respiration. However, BCS explained an additional unique portion of variation in respiration, particularly when accounting for differences in organic matter content. Our results suggest that by measuring bacterial community composition, we can improve both our understanding and the modeling of the permafrost carbon feedback.},
	number = {9},
	journal = {The ISME Journal},
	author = {Monteux, Sylvain and Weedon, James T. and Blume-Werry, Gesche and Gavazov, Konstantin and Jassey, Vincent E. J. and Johansson, Margareta and Keuper, Frida and Olid, Carolina and Dorrepaal, Ellen},
	month = sep,
	year = {2018},
	keywords = {\#nosource},
	pages = {2129--2141},
}

The decomposition of large stocks of soil organic carbon in thawing permafrost might depend on more than climate change-induced temperature increases: indirect effects of thawing via altered bacterial community structure (BCS) or rooting patterns are largely unexplored. We used a 10-year in situ permafrost thaw experiment and aerobic incubations to investigate alterations in BCS and potential respiration at different depths, and the extent to which they are related with each other and with root density. Active layer and permafrost BCS strongly differed, and the BCS in formerly frozen soils (below the natural thawfront) converged under induced deep thaw to strongly resemble the active layer BCS, possibly as a result of colonization by overlying microorganisms. Overall, respiration rates decreased with depth and soils showed lower potential respiration when subjected to deeper thaw, which we attributed to gradual labile carbon pool depletion. Despite deeper rooting under induced deep thaw, root density measurements did not improve soil chemistry-based models of potential respiration. However, BCS explained an additional unique portion of variation in respiration, particularly when accounting for differences in organic matter content. Our results suggest that by measuring bacterial community composition, we can improve both our understanding and the modeling of the permafrost carbon feedback.

@article{berggren_terrestrial_2018,
	title = {Terrestrial support of zooplankton biomass in northern rivers},
	volume = {63},
	copyright = {© 2018 Association for the Sciences of Limnology and Oceanography},
	issn = {1939-5590},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.10954},
	doi = {10.1002/lno.10954},
	abstract = {The contribution of terrestrially derived carbon to micro-crustacean zooplankton biomass (i.e., allochthony) has been previously studied in lakes, reservoirs, and estuaries, but little is known about zooplankton allochthony in rivers. In lacustrine environments, allochthony is regulated by distinct selective feeding behavior of different taxa. However, we hypothesized that restricted possibility for selective grazing in turbulent environments such as rivers would decouple zooplankton from specific microbial and algal food resources, such that their allochthony would mirror the terrestrial contribution to the surrounding bulk particle pool. We tested this idea by analyzing allochthony in 13 widely distributed Swedish rivers, using a dual-isotope mixing model. Zooplankton biomasses were generally low, and allochthony in different micro-crustacean groups (Cladocera, Cyclopoida, Calanoida) varied from 2\% to 77\%. As predicted, there were no correlations between allochthony and variables indicating the supply of algal and microbial food resources, such as chlorophyll a and bacterial production. Instead, the allochthony was generally similar to the share allochthonous contribution in bulk particulate organic matter, with relationships close to the 1 : 1 line. The zooplankton community allochthony was strongly regulated by the ecosystem metabolic balance between production and respiration, which in turn was dependent upon the ratio between total autochthonous organic carbon concentrations and water color. Our study for the first time shows that micro-crustacean allochthony is regulated differently in rivers compared to in lacustrine systems, and points to inefficient support of zooplankton biomass by algal resources in turbulent waters.},
	language = {en},
	number = {6},
	urldate = {2023-07-20},
	journal = {Limnology and Oceanography},
	author = {Berggren, M. and Bengtson, P. and Soares, A. R. A. and Karlsson, J.},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.10954},
	keywords = {\#nosource},
	pages = {2479--2492},
}

The contribution of terrestrially derived carbon to micro-crustacean zooplankton biomass (i.e., allochthony) has been previously studied in lakes, reservoirs, and estuaries, but little is known about zooplankton allochthony in rivers. In lacustrine environments, allochthony is regulated by distinct selective feeding behavior of different taxa. However, we hypothesized that restricted possibility for selective grazing in turbulent environments such as rivers would decouple zooplankton from specific microbial and algal food resources, such that their allochthony would mirror the terrestrial contribution to the surrounding bulk particle pool. We tested this idea by analyzing allochthony in 13 widely distributed Swedish rivers, using a dual-isotope mixing model. Zooplankton biomasses were generally low, and allochthony in different micro-crustacean groups (Cladocera, Cyclopoida, Calanoida) varied from 2% to 77%. As predicted, there were no correlations between allochthony and variables indicating the supply of algal and microbial food resources, such as chlorophyll a and bacterial production. Instead, the allochthony was generally similar to the share allochthonous contribution in bulk particulate organic matter, with relationships close to the 1 : 1 line. The zooplankton community allochthony was strongly regulated by the ecosystem metabolic balance between production and respiration, which in turn was dependent upon the ratio between total autochthonous organic carbon concentrations and water color. Our study for the first time shows that micro-crustacean allochthony is regulated differently in rivers compared to in lacustrine systems, and points to inefficient support of zooplankton biomass by algal resources in turbulent waters.

@article{ala-aho_using_2018,
	title = {Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape},
	volume = {556},
	issn = {0022-1694},
	url = {https://www.sciencedirect.com/science/article/pii/S0022169417307874},
	doi = {10.1016/j.jhydrol.2017.11.024},
	abstract = {Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.},
	language = {en},
	urldate = {2023-07-20},
	journal = {Journal of Hydrology},
	author = {Ala-aho, P. and Soulsby, C. and Pokrovsky, O. S. and Kirpotin, S. N. and Karlsson, J. and Serikova, S. and Vorobyev, S. N. and Manasypov, R. M. and Loiko, S. and Tetzlaff, D.},
	month = jan,
	year = {2018},
	keywords = {\#nosource, Hydrological connectivity, Low-relief, Runoff generation, Snowmelt, Stable water isotopes},
	pages = {279--293},
}

Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.

@article{blume-werry_proportion_2018,
	title = {Proportion of fine roots, but not plant biomass allocation belowground, increases with elevation in arctic tundra},
	volume = {29},
	issn = {1654-1103},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/jvs.12605/abstract},
	doi = {10.1111/jvs.12605},
	abstract = {Questions

Roots represent a considerable proportion of biomass, primary production, and litter input in arctic tundra, and plant allocation of biomass to above- or belowground tissue in response to climate change is a key factor in the future carbon balance of these ecosystems. According to optimality theory plants allocate carbon to the above- or belowground structure that captures the most limiting resource. We used an elevational gradient to test this theory and as a space-for-time substitution to inform on tundra carbon allocation patterns under a shifting climate, by exploring if increasing elevation was positively related to the root:shoot ratio, as well as a greater plant allocation to adsorptive over storage roots.


Location

Arctic tundra heath dominated by Empetrum hermaphroditum close to Abisko, Sweden.


Methods

We measured root:shoot and fine:coarse root ratios of the plant communities along an elevational gradient by sampling above- and belowground biomass, further separating root biomass into fine ({\textless} 1 mm) and coarse roots.


Results

Plant biomass was higher at the lower elevations, but the root:shoot ratio did not vary with elevation. Resource allocation to fine relative to coarse roots increased with elevation, resulting in a fine:coarse root ratio that more than doubled with increasing elevation.


Conclusions

Contrary to previous works, the root:shoot ratio along this elevational gradient remained stable. However, communities along our study system were dominated by the same species at each elevation which suggests that when changes in the root:shoot ratio occur with elevation these changes may be driven by differences in allocation patterns among species and thus turnover in plant community structure. Our results further reveal that the allocation of biomass to fine relative to coarse roots can differ between locations along an elevational gradient even when overall above- versus belowground biomass allocation does not. Given the functionally different roles of fine versus coarse roots this could have large implications for belowground carbon cycling. Our results highlight the importance of direct effects versus indirect effects (such as changes in plant community composition and nutrient availability) of climate change for future carbon allocation above- and belowground.
This article is protected by copyright. All rights reserved.},
	language = {en},
	urldate = {2018-01-02},
	journal = {Journal of Vegetation Science},
	author = {Blume-Werry, Gesche and Lindén, Elin and Andresen, Lisa and Classen, Aimée T. and Sanders, Nathan J. and von Oppen, Jonathan and Sundqvist, Maja K.},
	year = {2018},
	note = {00000},
	keywords = {\#nosource, Above- and belowground linkages, Betula nana, Empetrum hermaphroditum, above- and below-ground linkages, arctic tundra, biomass allocation, elevational gradient, fine roots, heath vegetation},
	pages = {226--235},
}

Questions Roots represent a considerable proportion of biomass, primary production, and litter input in arctic tundra, and plant allocation of biomass to above- or belowground tissue in response to climate change is a key factor in the future carbon balance of these ecosystems. According to optimality theory plants allocate carbon to the above- or belowground structure that captures the most limiting resource. We used an elevational gradient to test this theory and as a space-for-time substitution to inform on tundra carbon allocation patterns under a shifting climate, by exploring if increasing elevation was positively related to the root:shoot ratio, as well as a greater plant allocation to adsorptive over storage roots. Location Arctic tundra heath dominated by Empetrum hermaphroditum close to Abisko, Sweden. Methods We measured root:shoot and fine:coarse root ratios of the plant communities along an elevational gradient by sampling above- and belowground biomass, further separating root biomass into fine (\textless 1 mm) and coarse roots. Results Plant biomass was higher at the lower elevations, but the root:shoot ratio did not vary with elevation. Resource allocation to fine relative to coarse roots increased with elevation, resulting in a fine:coarse root ratio that more than doubled with increasing elevation. Conclusions Contrary to previous works, the root:shoot ratio along this elevational gradient remained stable. However, communities along our study system were dominated by the same species at each elevation which suggests that when changes in the root:shoot ratio occur with elevation these changes may be driven by differences in allocation patterns among species and thus turnover in plant community structure. Our results further reveal that the allocation of biomass to fine relative to coarse roots can differ between locations along an elevational gradient even when overall above- versus belowground biomass allocation does not. Given the functionally different roles of fine versus coarse roots this could have large implications for belowground carbon cycling. Our results highlight the importance of direct effects versus indirect effects (such as changes in plant community composition and nutrient availability) of climate change for future carbon allocation above- and belowground. This article is protected by copyright. All rights reserved.

@article{klaus_greenhouse_2018,
	title = {Greenhouse gas emissions from boreal inland waters unchanged after forest harvesting},
	volume = {15},
	issn = {1726-4170},
	url = {https://www.biogeosciences.net/15/5575/2018/},
	doi = {10.5194/bg-15-5575-2018},
	abstract = {{\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} Forestry practices often result in an increased export of carbon and nitrogen to downstream aquatic systems. Although these losses affect the greenhouse gas (GHG) budget of managed forests, it is unknown if they modify GHG emissions of recipient aquatic systems. To assess this question, air–water fluxes of carbon dioxide ({\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater}), methane ({\textless}span class="inline-formula"{\textgreater}CH$_{\textrm{4}}${\textless}/span{\textgreater}) and nitrous oxide ({\textless}span class="inline-formula"{\textgreater}N$_{\textrm{2}}$O{\textless}/span{\textgreater}) were quantified for humic lakes and their inlet streams in four boreal catchments using a before-after control-impact experiment. Two catchments were treated with forest clear-cuts followed by site preparation (18{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\% and 44{\textless}span class="thinspace"{\textgreater}{\textless}/span{\textgreater}\% of the catchment area). GHG fluxes and hydrological and physicochemical water characteristics were measured at multiple locations in lakes and streams at high temporal resolution throughout the summer season over a 4-year period. Both lakes and streams evaded all GHGs. The treatment did not significantly change GHG fluxes in streams or lakes within 3 years after the treatment, despite significant increases of {\textless}span class="inline-formula"{\textgreater}CO$_{\textrm{2}}${\textless}/span{\textgreater} and {\textless}span class="inline-formula"{\textgreater}CH$_{\textrm{4}}${\textless}/span{\textgreater} concentrations in hillslope groundwater. Our results highlight that GHGs leaching from forest clear-cuts may be buffered in the riparian zone–stream continuum, likely acting as effective biogeochemical processors and wind shelters to prevent additional GHG evasion via downstream inland waters. These findings are representative of low productive forests located in relatively flat landscapes where forestry practices cause only a limited initial impact on catchment hydrology and biogeochemistry.{\textless}/p{\textgreater}},
	language = {English},
	number = {18},
	urldate = {2019-05-06},
	journal = {Biogeosciences},
	author = {Klaus, Marcus and Geibrink, Erik and Jonsson, Anders and Bergström, Ann-Kristin and Bastviken, David and Laudon, Hjalmar and Klaminder, Jonatan and Karlsson, Jan},
	month = sep,
	year = {2018},
	keywords = {\#nosource},
	pages = {5575--5594},
}

\textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater Forestry practices often result in an increased export of carbon and nitrogen to downstream aquatic systems. Although these losses affect the greenhouse gas (GHG) budget of managed forests, it is unknown if they modify GHG emissions of recipient aquatic systems. To assess this question, air–water fluxes of carbon dioxide (\textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater), methane (\textlessspan class="inline-formula"\textgreaterCH$_{\textrm{4}}$\textless/span\textgreater) and nitrous oxide (\textlessspan class="inline-formula"\textgreaterN$_{\textrm{2}}$O\textless/span\textgreater) were quantified for humic lakes and their inlet streams in four boreal catchments using a before-after control-impact experiment. Two catchments were treated with forest clear-cuts followed by site preparation (18\textlessspan class="thinspace"\textgreater\textless/span\textgreater% and 44\textlessspan class="thinspace"\textgreater\textless/span\textgreater% of the catchment area). GHG fluxes and hydrological and physicochemical water characteristics were measured at multiple locations in lakes and streams at high temporal resolution throughout the summer season over a 4-year period. Both lakes and streams evaded all GHGs. The treatment did not significantly change GHG fluxes in streams or lakes within 3 years after the treatment, despite significant increases of \textlessspan class="inline-formula"\textgreaterCO$_{\textrm{2}}$\textless/span\textgreater and \textlessspan class="inline-formula"\textgreaterCH$_{\textrm{4}}$\textless/span\textgreater concentrations in hillslope groundwater. Our results highlight that GHGs leaching from forest clear-cuts may be buffered in the riparian zone–stream continuum, likely acting as effective biogeochemical processors and wind shelters to prevent additional GHG evasion via downstream inland waters. These findings are representative of low productive forests located in relatively flat landscapes where forestry practices cause only a limited initial impact on catchment hydrology and biogeochemistry.\textless/p\textgreater

@article{mclachlan_predicting_2018,
	title = {Predicting global scale exposure of humans to {PCB} 153 from historical emissions},
	volume = {20},
	issn = {2050-7887, 2050-7895},
	url = {http://xlink.rsc.org/?DOI=C8EM00023A},
	doi = {10.1039/C8EM00023A},
	language = {en},
	number = {5},
	urldate = {2019-04-23},
	journal = {Environmental Science: Processes \& Impacts},
	author = {McLachlan, Michael S. and Undeman, Emma and Zhao, Fangyuan and MacLeod, Matthew},
	year = {2018},
	keywords = {\#nosource},
	pages = {747--756},
}

@article{walker_microbial_2018,
	title = {Microbial temperature sensitivity and biomass change explain soil carbon loss with warming},
	volume = {8},
	copyright = {2018 The Author(s)},
	issn = {1758-6798},
	url = {https://www.nature.com/articles/s41558-018-0259-x},
	doi = {10.1038/s41558-018-0259-x},
	abstract = {Soil microbial activity is accelerated by warming and does not acclimate over periods of at least 50 years. Resulting soil carbon loss is nevertheless temporary because substrate depletion reduces microbial biomass and constrains the influence of microbes over the ecosystem.},
	language = {En},
	number = {10},
	urldate = {2019-05-20},
	journal = {Nature Climate Change},
	author = {Walker, Tom W. N. and Kaiser, Christina and Strasser, Florian and Herbold, Craig W. and Leblans, Niki I. W. and Woebken, Dagmar and Janssens, Ivan A. and Sigurdsson, Bjarni D. and Richter, Andreas},
	month = oct,
	year = {2018},
	keywords = {\#nosource},
	pages = {885},
}

Soil microbial activity is accelerated by warming and does not acclimate over periods of at least 50 years. Resulting soil carbon loss is nevertheless temporary because substrate depletion reduces microbial biomass and constrains the influence of microbes over the ecosystem.

@article{holmstrup_functional_2018,
	title = {Functional diversity of {Collembola} is reduced in soils subjected to short-term, but not long-term, geothermal warming},
	volume = {32},
	copyright = {© 2018 The Authors. Functional Ecology © 2018 British Ecological Society},
	issn = {1365-2435},
	url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13058},
	doi = {10.1111/1365-2435.13058},
	abstract = {Human activities have caused global changes of atmospheric chemistry resulting in increased temperature especially in the colder regions of the northern hemisphere. Since warming of the environment can have drastic effects on terrestrial ecosystems it is important to experimentally evaluate the extent of such effects in long-term field-based experiments. In this study we make use of both recent (short-term) and long-term geothermal warming of Icelandic soils to examine the responses of Collembola, an ecologically important group of soil invertebrates, to warming. On the basis of metabolic scaling theory, we hypothesized that species of small size would be more successful in warmed soils than species of larger size. Further we expected that top-soil-dwelling species would benefit more from warming than deep-soil-dwelling species. In order to test these hypotheses we sampled Collembola along replicated gradients of increasing temperature in areas that had been heated for about 6 years and more than 50 years respectively. Collembola were identified to species level, counted and the community-weighted mean trait scores for six functional and ecological traits were calculated. Results show that both short-term and long-term soil warming caused a shift towards a higher relative abundance of species with small body size. Furthermore, abundance of top-soil-dwelling Collembola tended to increase after short-term warming, but the opposite was observed after long-term warming. Using trait-based diversity indices (FRic and RaoQ), we show that functional richness and diversity of Collembola communities was significantly reduced (almost halved) as a result of short-term soil warming to about 10°C above normal, but this effect was not detected in plots equally warmed for more than 50 years. This indicates that the functional diversity of Collembola communities have high resilience towards soil warming in a long-term perspective. A plain language summary is available for this article.},
	language = {en},
	number = {5},
	urldate = {2019-05-20},
	journal = {Functional Ecology},
	author = {Holmstrup, Martin and Ehlers, Bodil K. and Slotsbo, Stine and Ilieva‐Makulec, Krassimira and Sigurdsson, Bjarni D. and Leblans, Niki I. W. and Ellers, Jacintha and Berg, Matty P.},
	year = {2018},
	keywords = {\#nosource, adaptation, ecological traits, global warming, soil ecology, springtails},
	pages = {1304--1316},
}

Human activities have caused global changes of atmospheric chemistry resulting in increased temperature especially in the colder regions of the northern hemisphere. Since warming of the environment can have drastic effects on terrestrial ecosystems it is important to experimentally evaluate the extent of such effects in long-term field-based experiments. In this study we make use of both recent (short-term) and long-term geothermal warming of Icelandic soils to examine the responses of Collembola, an ecologically important group of soil invertebrates, to warming. On the basis of metabolic scaling theory, we hypothesized that species of small size would be more successful in warmed soils than species of larger size. Further we expected that top-soil-dwelling species would benefit more from warming than deep-soil-dwelling species. In order to test these hypotheses we sampled Collembola along replicated gradients of increasing temperature in areas that had been heated for about 6 years and more than 50 years respectively. Collembola were identified to species level, counted and the community-weighted mean trait scores for six functional and ecological traits were calculated. Results show that both short-term and long-term soil warming caused a shift towards a higher relative abundance of species with small body size. Furthermore, abundance of top-soil-dwelling Collembola tended to increase after short-term warming, but the opposite was observed after long-term warming. Using trait-based diversity indices (FRic and RaoQ), we show that functional richness and diversity of Collembola communities was significantly reduced (almost halved) as a result of short-term soil warming to about 10°C above normal, but this effect was not detected in plots equally warmed for more than 50 years. This indicates that the functional diversity of Collembola communities have high resilience towards soil warming in a long-term perspective. A plain language summary is available for this article.

@article{maranon-jimenez_geothermally_2018,
	title = {Geothermally warmed soils reveal persistent increases in the respiratory costs of soil microbes contributing to substantial {C} losses},
	volume = {138},
	issn = {1573-515X},
	url = {https://doi.org/10.1007/s10533-018-0443-0},
	doi = {10.1007/s10533-018-0443-0},
	abstract = {Increasing temperatures can accelerate soil organic matter decomposition and release large amounts of CO2 to the atmosphere, potentially inducing positive warming feedbacks. Alterations to the temperature sensitivity and physiological functioning of soil microorganisms may play a key role in these carbon (C) losses. Geothermally active areas in Iceland provide stable and continuous soil temperature gradients to test this hypothesis, encompassing the full range of warming scenarios projected by the Intergovernmental Panel on Climate Change for the northern region. We took soils from these geothermal sites 7 years after the onset of warming and incubated them at varying temperatures and substrate availability conditions to detect persistent alterations of microbial physiology to long-term warming. Seven years of continuous warming ranging from 1.8 to 15.9 °C triggered a 8.6–58.0\% decrease on the C concentrations in the topsoil (0–10 cm) of these sub-arctic silt-loam Andosols. The sensitivity of microbial respiration to temperature (Q10) was not altered. However, soil microbes showed a persistent increase in their microbial metabolic quotients (microbial respiration per unit of microbial biomass) and a subsequent diminished C retention in biomass. After an initial depletion of labile soil C upon soil warming, increasing energy costs of metabolic maintenance and resource acquisition led to a weaker capacity of C stabilization in the microbial biomass of warmer soils. This mechanism contributes to our understanding of the acclimated response of soil respiration to in situ soil warming at the ecosystem level, despite a lack of acclimation at the physiological level. Persistent increases in the respiratory costs of soil microbes in response to warming constitute a fundamental process that should be incorporated into climate change-C cycling models.},
	language = {en},
	number = {3},
	urldate = {2019-05-20},
	journal = {Biogeochemistry},
	author = {Marañón-Jiménez, S. and Soong, J. L. and Leblans, N. I. W. and Sigurdsson, B. D. and Peñuelas, J. and Richter, A. and Asensio, D. and Fransen, E. and Janssens, I. A.},
	month = may,
	year = {2018},
	keywords = {\#nosource, Metabolic quotient, Microbial biomass, Microbial physiology, Q10, Soil CO2 fluxes, Soil respiration, Temperature increase},
	pages = {245--260},
}

Increasing temperatures can accelerate soil organic matter decomposition and release large amounts of CO2 to the atmosphere, potentially inducing positive warming feedbacks. Alterations to the temperature sensitivity and physiological functioning of soil microorganisms may play a key role in these carbon (C) losses. Geothermally active areas in Iceland provide stable and continuous soil temperature gradients to test this hypothesis, encompassing the full range of warming scenarios projected by the Intergovernmental Panel on Climate Change for the northern region. We took soils from these geothermal sites 7 years after the onset of warming and incubated them at varying temperatures and substrate availability conditions to detect persistent alterations of microbial physiology to long-term warming. Seven years of continuous warming ranging from 1.8 to 15.9 °C triggered a 8.6–58.0% decrease on the C concentrations in the topsoil (0–10 cm) of these sub-arctic silt-loam Andosols. The sensitivity of microbial respiration to temperature (Q10) was not altered. However, soil microbes showed a persistent increase in their microbial metabolic quotients (microbial respiration per unit of microbial biomass) and a subsequent diminished C retention in biomass. After an initial depletion of labile soil C upon soil warming, increasing energy costs of metabolic maintenance and resource acquisition led to a weaker capacity of C stabilization in the microbial biomass of warmer soils. This mechanism contributes to our understanding of the acclimated response of soil respiration to in situ soil warming at the ecosystem level, despite a lack of acclimation at the physiological level. Persistent increases in the respiratory costs of soil microbes in response to warming constitute a fundamental process that should be incorporated into climate change-C cycling models.

@article{lyon_lessons_2018,
	title = {Lessons learned from monitoring the stable water isotopic variability in precipitation and streamflow across a snow-dominated subarctic catchment},
	volume = {50},
	issn = {1523-0430},
	url = {https://doi.org/10.1080/15230430.2018.1454778},
	doi = {10.1080/15230430.2018.1454778},
	abstract = {This empirical study explores shifts in stable water isotopic composition for a subarctic catchment located in northern Sweden as it transitions from spring freshet to summer low flows. Relative changes in the isotopic composition of streamflow across the main catchment and fifteen nested subcatchments are characterized in relation to the isotopic composition of precipitation. With our sampling campaign, we explore the variability in stream-water isotopic composition that originates from precipitation as the input shifts from snow to rain and as landscape flow pathways change across scales. The isotopic similarity of high-elevation snowpack water and early season rainfall water seen through our sampling scheme made it difficult to truly isolate the impact of seasonal precipitation phase change on stream-water isotopic response. This highlights the need to explicitly consider the complexity of arctic and alpine landscapes when designing sampling strategies to characterize hydrological variability via stable water isotopes. Results show a potential influence of evaporation and source water mixing both spatially (variations with elevation) and temporally (variations from post-freshet to summer flows) on the composition of stream water across Miellajokka. As such, the data collected in this empirical study allow for initial conceptualization of the relative importance of, for example, hydrological connectivity within this mountainous, subarctic landscape.},
	number = {1},
	urldate = {2019-08-30},
	journal = {Arctic, Antarctic, and Alpine Research},
	author = {Lyon, Steve W. and Ploum, Stefan W. and Velde, Ype van der and Rocher-Ros, Gerard and Mörth, Carl-Magnus and Giesler, Reiner},
	month = jan,
	year = {2018},
	keywords = {\#nosource, Catchment hydrology, freshet, spring flood, stable water isotopes, tracers},
	pages = {e1454778},
}

This empirical study explores shifts in stable water isotopic composition for a subarctic catchment located in northern Sweden as it transitions from spring freshet to summer low flows. Relative changes in the isotopic composition of streamflow across the main catchment and fifteen nested subcatchments are characterized in relation to the isotopic composition of precipitation. With our sampling campaign, we explore the variability in stream-water isotopic composition that originates from precipitation as the input shifts from snow to rain and as landscape flow pathways change across scales. The isotopic similarity of high-elevation snowpack water and early season rainfall water seen through our sampling scheme made it difficult to truly isolate the impact of seasonal precipitation phase change on stream-water isotopic response. This highlights the need to explicitly consider the complexity of arctic and alpine landscapes when designing sampling strategies to characterize hydrological variability via stable water isotopes. Results show a potential influence of evaporation and source water mixing both spatially (variations with elevation) and temporally (variations from post-freshet to summer flows) on the composition of stream water across Miellajokka. As such, the data collected in this empirical study allow for initial conceptualization of the relative importance of, for example, hydrological connectivity within this mountainous, subarctic landscape.

@article{bokhorst_contrasting_2018,
	title = {Contrasting responses of springtails and mites to elevation and vegetation type in the sub-{Arctic}},
	volume = {67},
	issn = {0031-4056},
	url = {http://www.sciencedirect.com/science/article/pii/S0031405617302603},
	doi = {10.1016/j.pedobi.2018.02.004},
	abstract = {Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 °C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53\% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epi-edaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.},
	language = {en},
	urldate = {2019-11-05},
	journal = {Pedobiologia},
	author = {Bokhorst, Stef and (Ciska) Veen, G. F. and Sundqvist, Maja and De Long, Jonathan R. and Kardol, Paul and Wardle, David A.},
	month = mar,
	year = {2018},
	keywords = {\#nosource, Acari, Climate change, Collembola, Elevational gradient, Heath, Meadow, Microarthropod},
	pages = {57--64},
}

Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 °C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epi-edaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.

@article{zhao_soils_2018,
	title = {Soils beneath different arctic shrubs have contrasting responses to a natural gradient in temperature},
	volume = {9},
	copyright = {© 2018 The Authors.},
	issn = {2150-8925},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecs2.2290},
	doi = {10.1002/ecs2.2290},
	abstract = {Shrubs commonly form islands of fertility and are expanding their distribution and dominance in the arctic due to climate change, yet how soil properties may be influenced when different species of shrubs expand under warmer climates remains less explored. Important plant traits, such as their associated root community, are linked to functionally different and dominant shrub species in the arctic and these traits likely shape biogeochemical cycling in areas of shrub expansion. Using an elevational gradient as a proxy for warming, we explored how biochemical processes beneath two important arctic shrubs varied under warmer (low elevation) and cooler (high elevation) climates. Interestingly, the influence of elevation on biogeochemistry varied between the two shrubs. At the low elevation, Betula nana L., an ectomycorrhizal shrub, had high carbon (C) degrading enzyme activities, and relatively low potential net nitrogen (N) mineralization rates. Conversely, Empetrum nigrum ssp. hermaphroditum Hagerup, an ericoid mycorrhizal dwarf-shrub, had higher enzyme activities and net N immobilization rates at the higher elevation. Further, E. nigrum ssp. hermpahroditum appeared to have a more closed C and nutrient cycle than B. nana—enzymes degrading C, N, and phosphorus were tightly correlated with each other and with total C and ammonium concentrations in the humus beneath E. nigrum ssp. hermaphroditum, but not beneath B. nana. Our results suggest differences in the warming responses of C and N cycling beneath shrub species across an arctic tundra landscape.},
	language = {en},
	number = {6},
	urldate = {2019-11-05},
	journal = {Ecosphere},
	author = {Zhao, Qiong and Sundqvist, Maja K. and Newman, Gregory S. and Classen, Aimée T.},
	year = {2018},
	keywords = {\#nosource, biochemical processes, ectomycorrhizae, ericoid mycorrhizae, global warming, shrub species},
	pages = {e02290},
}

Shrubs commonly form islands of fertility and are expanding their distribution and dominance in the arctic due to climate change, yet how soil properties may be influenced when different species of shrubs expand under warmer climates remains less explored. Important plant traits, such as their associated root community, are linked to functionally different and dominant shrub species in the arctic and these traits likely shape biogeochemical cycling in areas of shrub expansion. Using an elevational gradient as a proxy for warming, we explored how biochemical processes beneath two important arctic shrubs varied under warmer (low elevation) and cooler (high elevation) climates. Interestingly, the influence of elevation on biogeochemistry varied between the two shrubs. At the low elevation, Betula nana L., an ectomycorrhizal shrub, had high carbon (C) degrading enzyme activities, and relatively low potential net nitrogen (N) mineralization rates. Conversely, Empetrum nigrum ssp. hermaphroditum Hagerup, an ericoid mycorrhizal dwarf-shrub, had higher enzyme activities and net N immobilization rates at the higher elevation. Further, E. nigrum ssp. hermpahroditum appeared to have a more closed C and nutrient cycle than B. nana—enzymes degrading C, N, and phosphorus were tightly correlated with each other and with total C and ammonium concentrations in the humus beneath E. nigrum ssp. hermaphroditum, but not beneath B. nana. Our results suggest differences in the warming responses of C and N cycling beneath shrub species across an arctic tundra landscape.

@article{murphy_roughness_2018,
	title = {Roughness effects of diatomaceous slime fouling on turbulent boundary layer hydrodynamics},
	volume = {34},
	issn = {0892-7014},
	url = {https://doi.org/10.1080/08927014.2018.1517867},
	doi = {10.1080/08927014.2018.1517867},
	abstract = {Biofilm fouling significantly impacts ship performance. Here, the impact of biofilm on boundary layer structure at a ship-relevant, low Reynolds number was investigated. Boundary layer measurements were performed over slime-fouled plates using high resolution particle image velocimetry (PIV). The velocity profile over the biofilm showed a downward shift in the log-law region (ΔU+), resulting in an effective roughness height (ks) of 8.8 mm, significantly larger than the physical thickness of the biofilm (1.7 ± 0.5 mm) and generating more than three times as much frictional drag as the smooth-wall. The skin-friction coefficient, Cf, of the biofilm was 9.0 × 10−3 compared with 2.9 × 10−3 for the smooth wall. The biofilm also enhances turbulent kinetic energy (tke) and Reynolds shear stress, which are more heterogeneous in the streamwise direction than smooth-wall flows. This suggests that biofilms increase drag due to high levels of momentum transport, likely resulting from protruding streamers and surface compliance.},
	number = {9},
	urldate = {2019-07-16},
	journal = {Biofouling},
	author = {Murphy, Elizabeth A. K. and Barros, Julio M. and Schultz, Michael P. and Flack, Karen A. and Steppe, Cecily N. and Reidenbach, Matthew A.},
	month = oct,
	year = {2018},
	pmid = {30602310},
	keywords = {\#nosource, Biofilm, PIV, boundary layer, drag, roughness, turbulence},
	pages = {976--988},
}

Biofilm fouling significantly impacts ship performance. Here, the impact of biofilm on boundary layer structure at a ship-relevant, low Reynolds number was investigated. Boundary layer measurements were performed over slime-fouled plates using high resolution particle image velocimetry (PIV). The velocity profile over the biofilm showed a downward shift in the log-law region (ΔU+), resulting in an effective roughness height (ks) of 8.8 mm, significantly larger than the physical thickness of the biofilm (1.7 ± 0.5 mm) and generating more than three times as much frictional drag as the smooth-wall. The skin-friction coefficient, Cf, of the biofilm was 9.0 × 10−3 compared with 2.9 × 10−3 for the smooth wall. The biofilm also enhances turbulent kinetic energy (tke) and Reynolds shear stress, which are more heterogeneous in the streamwise direction than smooth-wall flows. This suggests that biofilms increase drag due to high levels of momentum transport, likely resulting from protruding streamers and surface compliance.

@phdthesis{monteux_song_2018,
	address = {Umeå, Sweden},
	type = {Doctoral {Thesis}},
	title = {A song of ice and mud : {Interactions} of microbes with roots, fauna and carbon in warming permafrost-affected soils},
	shorttitle = {A song of ice and mud},
	url = {http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-151472},
	abstract = {Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis.

We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density.

We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32\% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning.

This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.},
	language = {eng},
	urldate = {2018-09-12},
	school = {Umeå University},
	author = {Monteux, Sylvain},
	collaborator = {Dorrepaal, Ellen and Keuper, Frida and Weedon, James T.},
	year = {2018},
	keywords = {\#nosource},
}

Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis. We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density. We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning. This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.

@article{nilsson_interaction_2018,
	title = {Interaction strength and stability in stage-structured food web modules},
	volume = {127},
	copyright = {© 2018 The Authors},
	issn = {1600-0706},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/oik.05029},
	doi = {10.1111/oik.05029},
	abstract = {There has been a long-standing debate on what creates stability in food webs. One major finding is that weak interactions can mute the destabilizing potential of strong interactions. Considering that stage structure is common in nature, that existing studies on stability that include population stage structure point in different directions, and the recent theoretical developments in the area of stage structure, there is a need to address the effects of population stage structure in this context. Using simple food web modules, with stage structure in an intermediate consumer, we here begin to theoretically investigate the effects of stage structure on food web stability. We found a general correspondence to previous results such that strong interactions had destabilizing effects and weak interactions that result in decreased energy flux had stabilizing effects. However, we also found a number of novel results connected to stage structure. Interestingly, weak interactions can be destabilizing when they excite other interactions. We also found that cohort cycles and predator–prey cycles did not respond in the same way to increasing interactions strength. We found that the combined effects of two predators feeding on the same prey can strongly destabilize a system. Consistent with previous studies, we also found that stage-specific feeding can create a refuge effect that leads to a lack of strong destabilization at high interaction strength. Overall, stage structure had both stabilizing and destabilizing aspects. Some effects could be explained by our current understanding of energetic processes; others need additional consideration. Additional aspects such as shunting of energy between stages, control of biomass fluxes, and interactions between lags and energy flux, should be considered.},
	language = {en},
	number = {10},
	urldate = {2018-07-05},
	journal = {Oikos},
	author = {Nilsson, Karin A. and McCann, Kevin S. and Caskenette, Amanda L.},
	month = apr,
	year = {2018},
	note = {00000},
	keywords = {\#nosource, interaction strength, stability, stage structure},
	pages = {1494--1505},
}

There has been a long-standing debate on what creates stability in food webs. One major finding is that weak interactions can mute the destabilizing potential of strong interactions. Considering that stage structure is common in nature, that existing studies on stability that include population stage structure point in different directions, and the recent theoretical developments in the area of stage structure, there is a need to address the effects of population stage structure in this context. Using simple food web modules, with stage structure in an intermediate consumer, we here begin to theoretically investigate the effects of stage structure on food web stability. We found a general correspondence to previous results such that strong interactions had destabilizing effects and weak interactions that result in decreased energy flux had stabilizing effects. However, we also found a number of novel results connected to stage structure. Interestingly, weak interactions can be destabilizing when they excite other interactions. We also found that cohort cycles and predator–prey cycles did not respond in the same way to increasing interactions strength. We found that the combined effects of two predators feeding on the same prey can strongly destabilize a system. Consistent with previous studies, we also found that stage-specific feeding can create a refuge effect that leads to a lack of strong destabilization at high interaction strength. Overall, stage structure had both stabilizing and destabilizing aspects. Some effects could be explained by our current understanding of energetic processes; others need additional consideration. Additional aspects such as shunting of energy between stages, control of biomass fluxes, and interactions between lags and energy flux, should be considered.

@article{faucherre_short_2018,
	title = {Short and {Long}-{Term} {Controls} on {Active} {Layer} and {Permafrost} {Carbon} {Turnover} {Across} the {Arctic}},
	volume = {123},
	copyright = {©2018. American Geophysical Union. All Rights Reserved.},
	issn = {2169-8961},
	url = {http://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JG004069},
	doi = {10.1002/2017JG004069},
	abstract = {Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (Closs) five times during a 1 year incubation. The incubated material consisted of near-surface active layer (ALNS), subsurface active layer (ALSS), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, δ13C, δ15N, and dry bulk density (DBD). While no significant differences were observed between total ALSS and permafrost Closs over 1 year incubation (2.3 ± 2.4\% and 2.5 ± 1.5\% Closs, respectively), ALNS samples showed higher Closs (7.9 ± 4.2\%). DBD was the best explanatory parameter for active layer Closs across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial Closs between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.},
	language = {en},
	number = {2},
	urldate = {2018-08-30},
	journal = {Journal of Geophysical Research: Biogeosciences},
	author = {Faucherre, Samuel and Jørgensen, Christian Juncher and Blok, Daan and Weiss, Niels and Siewert, Matthias Benjamin and Bang‐Andreasen, Toke and Hugelius, Gustaf and Kuhry, Peter and Elberling, Bo},
	month = feb,
	year = {2018},
	note = {00002},
	keywords = {\#nosource, carbon, carbon dioxide, carbon mineralization, decomposition, permafrost},
	pages = {372--390},
}

Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (Closs) five times during a 1 year incubation. The incubated material consisted of near-surface active layer (ALNS), subsurface active layer (ALSS), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, δ13C, δ15N, and dry bulk density (DBD). While no significant differences were observed between total ALSS and permafrost Closs over 1 year incubation (2.3 ± 2.4% and 2.5 ± 1.5% Closs, respectively), ALNS samples showed higher Closs (7.9 ± 4.2%). DBD was the best explanatory parameter for active layer Closs across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial Closs between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

@article{siewert_high-resolution_2018,
	title = {High-resolution digital mapping of soil organic carbon in permafrost terrain using machine learning : a case study in a sub-{Arctic} peatland environment},
	volume = {15},
	shorttitle = {High-resolution digital mapping of soil organic carbon in permafrost terrain using machine learning},
	url = {http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-146566},
	doi = {10.5194/bg-15-1663-2018},
	language = {eng},
	number = {6},
	urldate = {2018-08-30},
	journal = {Biogeosciences},
	author = {Siewert, Matthias B.},
	year = {2018},
	note = {00002},
	keywords = {\#nosource},
	pages = {1663--1682},
}

@article{tang_drivers_2018,
	title = {Drivers of dissolved organic carbon export in a subarctic catchment: {Importance} of microbial decomposition, sorption-desorption, peatland and lateral flow},
	volume = {622-623},
	issn = {0048-9697},
	shorttitle = {Drivers of dissolved organic carbon export in a subarctic catchment},
	url = {http://www.sciencedirect.com/science/article/pii/S0048969717333107},
	doi = {10.1016/j.scitotenv.2017.11.252},
	abstract = {Tundra soils account for 50\% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS is compared to observed DOC export at Stordalen catchment in northern Sweden. Vegetation communities include flood-tolerant graminoids (Eriophorum) and Sphagnum moss, birch forest and dwarf shrub communities. The processes, sorption-desorption and microbial decomposition (DOC production and mineralization) are found to contribute most to the variance in DOC export based on a detailed variance-based Sobol sensitivity analysis (SA) at grid cell-level. Catchment-level SA shows that the highest mean DOC exports come from the Eriophorum peatland (fen). A comparison with observations shows that the model captures the seasonality of DOC fluxes. Two catchment simulations, one without water lateral routing and one without peatland processes, were compared with the catchment simulations with all processes. The comparison showed that the current implementation of catchment lateral flow and peatland processes in LPJ-GUESS are essential to capture catchment-level DOC dynamics and indicate the model is at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The extended model provides a new tool to investigate potential interactions among climate change, vegetation dynamics, soil hydrology and DOC dynamics at both stand-alone to catchment scales.},
	urldate = {2018-08-30},
	journal = {Science of The Total Environment},
	author = {Tang, Jing and Yurova, Alla Y. and Schurgers, Guy and Miller, Paul A. and Olin, Stefan and Smith, Benjamin and Siewert, Matthias B. and Olefeldt, David and Pilesjö, Petter and Poska, Anneli},
	month = may,
	year = {2018},
	note = {00001},
	keywords = {\#nosource, DOC flux, LPJ-GUESS, Lateral flow, Peatland, Sorption-desorption, Subarctic catchment},
	pages = {260--274},
}

Tundra soils account for 50% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS is compared to observed DOC export at Stordalen catchment in northern Sweden. Vegetation communities include flood-tolerant graminoids (Eriophorum) and Sphagnum moss, birch forest and dwarf shrub communities. The processes, sorption-desorption and microbial decomposition (DOC production and mineralization) are found to contribute most to the variance in DOC export based on a detailed variance-based Sobol sensitivity analysis (SA) at grid cell-level. Catchment-level SA shows that the highest mean DOC exports come from the Eriophorum peatland (fen). A comparison with observations shows that the model captures the seasonality of DOC fluxes. Two catchment simulations, one without water lateral routing and one without peatland processes, were compared with the catchment simulations with all processes. The comparison showed that the current implementation of catchment lateral flow and peatland processes in LPJ-GUESS are essential to capture catchment-level DOC dynamics and indicate the model is at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The extended model provides a new tool to investigate potential interactions among climate change, vegetation dynamics, soil hydrology and DOC dynamics at both stand-alone to catchment scales.

@article{hamdan_carbon_2018,
	title = {Carbon dioxide stimulates lake primary production},
	volume = {8},
	copyright = {2018 The Author(s)},
	issn = {2045-2322},
	url = {http://www.nature.com/articles/s41598-018-29166-3},
	doi = {10.1038/s41598-018-29166-3},
	abstract = {Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO2) and forms the resource base for higher trophic levels. Still, the relative contribution of different controls on GPP at the whole-ecosystem scale is far from resolved. Here we show, by manipulating CO2 concentrations in large-scale experimental pond ecosystems, that CO2 availability is a key driver of whole-ecosystem GPP. This result suggests we need to reformulate past conceptual models describing controls of lake ecosystem productivity and include our findings when developing models used to predict future lake ecosystem responses to environmental change.},
	language = {en},
	number = {1},
	urldate = {2018-07-30},
	journal = {Scientific Reports},
	author = {Hamdan, Mohammed and Byström, Pär and Hotchkiss, Erin R. and Al-Haidarey, Mohammed J. and Ask, Jenny and Karlsson, Jan},
	month = jul,
	year = {2018},
	note = {00000},
	keywords = {\#nosource},
	pages = {10878},
}

Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO2) and forms the resource base for higher trophic levels. Still, the relative contribution of different controls on GPP at the whole-ecosystem scale is far from resolved. Here we show, by manipulating CO2 concentrations in large-scale experimental pond ecosystems, that CO2 availability is a key driver of whole-ecosystem GPP. This result suggests we need to reformulate past conceptual models describing controls of lake ecosystem productivity and include our findings when developing models used to predict future lake ecosystem responses to environmental change.

@article{mzobe_dissolved_2018,
	title = {Dissolved organic carbon in streams within a subarctic catchment analysed using a {GIS}/remote sensing approach},
	volume = {13},
	issn = {1932-6203},
	url = {http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199608},
	doi = {10.1371/journal.pone.0199608},
	abstract = {Climate change projections show that temperature and precipitation increases can alter the exchange of greenhouse gases between the atmosphere and high latitude landscapes, including their freshwaters. Dissolved organic carbon (DOC) plays an important role in greenhouse gas emissions, but the impact of catchment productivity on DOC release to subarctic waters remains poorly known, especially at regional scales. We test the hypothesis that increased terrestrial productivity, as indicated by the normalized difference vegetation index (NDVI), generates higher stream DOC concentrations in the Stordalen catchment in subarctic Sweden. Furthermore, we aimed to determine the degree to which other generic catchment properties (elevation, slope) explain DOC concentration, and whether or not land cover variables representing the local vegetation type (e.g., mire, forest) need to be included to obtain adequate predictive models for DOC delivered into rivers. We show that the land cover type, especially the proportion of mire, played a dominant role in the catchment’s release of DOC, while NDVI, slope, and elevation were supporting predictor variables. The NDVI as a single predictor showed weak and inconsistent relationships to DOC concentrations in recipient waters, yet NDVI was a significant positive regulator of DOC in multiple regression models that included land cover variables. Our study illustrates that vegetation type exerts primary control in DOC regulation in Stordalen, while productivity (NDVI) is of secondary importance. Thus, predictive multiple linear regression models for DOC can be utilized combining these different types of explanatory variables.},
	language = {en},
	number = {7},
	urldate = {2018-07-16},
	journal = {PLOS ONE},
	author = {Mzobe, Pearl and Berggren, Martin and Pilesjö, Petter and Lundin, Erik and Olefeldt, David and Roulet, Nigel T. and Persson, Andreas},
	month = jul,
	year = {2018},
	note = {00000},
	keywords = {\#nosource, Climate change, Forests, Lakes, Linear regression analysis, Rivers, Surface water, Tundra, Wetlands},
	pages = {e0199608},
}

Climate change projections show that temperature and precipitation increases can alter the exchange of greenhouse gases between the atmosphere and high latitude landscapes, including their freshwaters. Dissolved organic carbon (DOC) plays an important role in greenhouse gas emissions, but the impact of catchment productivity on DOC release to subarctic waters remains poorly known, especially at regional scales. We test the hypothesis that increased terrestrial productivity, as indicated by the normalized difference vegetation index (NDVI), generates higher stream DOC concentrations in the Stordalen catchment in subarctic Sweden. Furthermore, we aimed to determine the degree to which other generic catchment properties (elevation, slope) explain DOC concentration, and whether or not land cover variables representing the local vegetation type (e.g., mire, forest) need to be included to obtain adequate predictive models for DOC delivered into rivers. We show that the land cover type, especially the proportion of mire, played a dominant role in the catchment’s release of DOC, while NDVI, slope, and elevation were supporting predictor variables. The NDVI as a single predictor showed weak and inconsistent relationships to DOC concentrations in recipient waters, yet NDVI was a significant positive regulator of DOC in multiple regression models that included land cover variables. Our study illustrates that vegetation type exerts primary control in DOC regulation in Stordalen, while productivity (NDVI) is of secondary importance. Thus, predictive multiple linear regression models for DOC can be utilized combining these different types of explanatory variables.

@article{lett_global_2018,
	title = {Global drivers of tree seedling establishment at alpine treelines in a changing climate},
	volume = {32},
	copyright = {© 2018 The Authors. Functional Ecology © 2018 British Ecological Society},
	issn = {1365-2435},
	url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13137},
	doi = {10.1111/1365-2435.13137},
	abstract = {Alpine and Arctic treeline expansion depends on establishment of tree seedlings beyond the current treeline, which is expected to occur with climate warming. However, treelines often fail to respond to higher temperatures, and it is therefore likely that other environmental factors are important for seedling establishment. We aimed to analyse our current understanding of how temperature and a range of other environmental drivers affect tree seedling establishment at the alpine and Arctic treelines world-wide and to assess the relative importance of temperature compared with other factors and how they interact. We collected 366 observations from 76 experimental and observational papers for a qualitative analysis of the role of a wide range of environmental factors on tree seed germination, tree seedling growth, survival and natural occurrence. For a subset of these studies, where the experimental design allowed, we conducted formal meta-analyses to reveal if there were global drivers for different seedling life traits. The analyses showed that a wide range of abiotic and biotic factors affected tree seedling establishment besides from temperature, including water, snow, nutrients, light and surrounding vegetation. The meta-analyses showed that different seedling life stages do not respond similarly to environmental factors. For example, temperature had positive effects on growth, while tree seedling survival and germination showed mixed responses to warming. Further, warming was as often as not the strongest factor controlling tree seedling establishment, when compared to with one of five other environmental factors. Moreover, warming effects often depended on other factors such as moisture or the presence of surrounding vegetation. Our results suggest that population dynamics of trees at the alpine and Arctic treeline is responsive to environmental changes and show that there is a clear need for multifactorial studies if we want to fully understand and predict the interplay between warming and other environmental factors and their effect on tree seedling establishment across current treelines. A plain language summary is available for this article.},
	number = {7},
	urldate = {2018-07-05},
	journal = {Functional Ecology},
	author = {Lett, Signe and Dorrepaal, Ellen},
	year = {2018},
	note = {00000},
	keywords = {\#nosource, germination, growth, nutrients, plant interactions, snow, soil moisture, survival, warming},
	pages = {1666--1680},
}

Alpine and Arctic treeline expansion depends on establishment of tree seedlings beyond the current treeline, which is expected to occur with climate warming. However, treelines often fail to respond to higher temperatures, and it is therefore likely that other environmental factors are important for seedling establishment. We aimed to analyse our current understanding of how temperature and a range of other environmental drivers affect tree seedling establishment at the alpine and Arctic treelines world-wide and to assess the relative importance of temperature compared with other factors and how they interact. We collected 366 observations from 76 experimental and observational papers for a qualitative analysis of the role of a wide range of environmental factors on tree seed germination, tree seedling growth, survival and natural occurrence. For a subset of these studies, where the experimental design allowed, we conducted formal meta-analyses to reveal if there were global drivers for different seedling life traits. The analyses showed that a wide range of abiotic and biotic factors affected tree seedling establishment besides from temperature, including water, snow, nutrients, light and surrounding vegetation. The meta-analyses showed that different seedling life stages do not respond similarly to environmental factors. For example, temperature had positive effects on growth, while tree seedling survival and germination showed mixed responses to warming. Further, warming was as often as not the strongest factor controlling tree seedling establishment, when compared to with one of five other environmental factors. Moreover, warming effects often depended on other factors such as moisture or the presence of surrounding vegetation. Our results suggest that population dynamics of trees at the alpine and Arctic treeline is responsive to environmental changes and show that there is a clear need for multifactorial studies if we want to fully understand and predict the interplay between warming and other environmental factors and their effect on tree seedling establishment across current treelines. A plain language summary is available for this article.

@article{bjorkman_plant_2018,
	title = {Plant functional trait change across a warming tundra biome},
	volume = {562},
	copyright = {2018 Springer Nature Limited},
	issn = {1476-4687},
	url = {https://www.nature.com/articles/s41586-018-0563-7},
	doi = {10.1038/s41586-018-0563-7},
	abstract = {Analyses of the relationships between temperature, moisture and seven key plant functional traits across the tundra and over time show that community height increased with warming across all sites, whereas other traits lagged behind predicted rates of change.},
	language = {En},
	number = {7725},
	urldate = {2018-10-25},
	journal = {Nature},
	author = {Bjorkman, Anne D. and Myers-Smith, Isla H. and Elmendorf, Sarah C. and Normand, Signe and Rüger, Nadja and Beck, Pieter S. A. and Blach-Overgaard, Anne and Blok, Daan and Cornelissen, J. Hans C. and Forbes, Bruce C. and Georges, Damien and Goetz, Scott J. and Guay, Kevin C. and Henry, Gregory H. R. and HilleRisLambers, Janneke and Hollister, Robert D. and Karger, Dirk N. and Kattge, Jens and Manning, Peter and Prevéy, Janet S. and Rixen, Christian and Schaepman-Strub, Gabriela and Thomas, Haydn J. D. and Vellend, Mark and Wilmking, Martin and Wipf, Sonja and Carbognani, Michele and Hermanutz, Luise and Lévesque, Esther and Molau, Ulf and Petraglia, Alessandro and Soudzilovskaia, Nadejda A. and Spasojevic, Marko J. and Tomaselli, Marcello and Vowles, Tage and Alatalo, Juha M. and Alexander, Heather D. and Anadon-Rosell, Alba and Angers-Blondin, Sandra and Beest, Mariska te and Berner, Logan and Björk, Robert G. and Buchwal, Agata and Buras, Allan and Christie, Katherine and Cooper, Elisabeth J. and Dullinger, Stefan and Elberling, Bo and Eskelinen, Anu and Frei, Esther R. and Grau, Oriol and Grogan, Paul and Hallinger, Martin and Harper, Karen A. and Heijmans, Monique M. P. D. and Hudson, James and Hülber, Karl and Iturrate-Garcia, Maitane and Iversen, Colleen M. and Jaroszynska, Francesca and Johnstone, Jill F. and Jørgensen, Rasmus Halfdan and Kaarlejärvi, Elina and Klady, Rebecca and Kuleza, Sara and Kulonen, Aino and Lamarque, Laurent J. and Lantz, Trevor and Little, Chelsea J. and Speed, James D. M. and Michelsen, Anders and Milbau, Ann and Nabe-Nielsen, Jacob and Nielsen, Sigrid Schøler and Ninot, Josep M. and Oberbauer, Steven F. and Olofsson, Johan and Onipchenko, Vladimir G. and Rumpf, Sabine B. and Semenchuk, Philipp and Shetti, Rohan and Collier, Laura Siegwart and Street, Lorna E. and Suding, Katharine N. and Tape, Ken D. and Trant, Andrew and Treier, Urs A. and Tremblay, Jean-Pierre and Tremblay, Maxime and Venn, Susanna and Weijers, Stef and Zamin, Tara and Boulanger-Lapointe, Noémie and Gould, William A. and Hik, David S. and Hofgaard, Annika and Jónsdóttir, Ingibjörg S. and Jorgenson, Janet and Klein, Julia and Magnusson, Borgthor and Tweedie, Craig and Wookey, Philip A. and Bahn, Michael and Blonder, Benjamin and Bodegom, Peter M. van and Bond-Lamberty, Benjamin and Campetella, Giandiego and Cerabolini, Bruno E. L. and Chapin, F. Stuart and Cornwell, William K. and Craine, Joseph and Dainese, Matteo and Vries, Franciska T. de and Díaz, Sandra and Enquist, Brian J. and Green, Walton and Milla, Ruben and Niinemets, Ülo and Onoda, Yusuke and Ordoñez, Jenny C. and Ozinga, Wim A. and Penuelas, Josep and Poorter, Hendrik and Poschlod, Peter and Reich, Peter B. and Sandel, Brody and Schamp, Brandon and Sheremetev, Serge and Weiher, Evan},
	month = oct,
	year = {2018},
	keywords = {\#nosource},
	pages = {57},
}

Analyses of the relationships between temperature, moisture and seven key plant functional traits across the tundra and over time show that community height increased with warming across all sites, whereas other traits lagged behind predicted rates of change.

@article{lapierre_similarity_2018,
	title = {Similarity in spatial structure constrains ecosystem relationships: {Building} a macroscale understanding of lakes},
	volume = {27},
	copyright = {© 2018 John Wiley \& Sons Ltd},
	issn = {1466-8238},
	shorttitle = {Similarity in spatial structure constrains ecosystem relationships},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12781},
	doi = {10.1111/geb.12781},
	abstract = {Aim We aimed to measure the dominant spatial patterns in ecosystem properties (such as nutrients and measures of primary production) and the multi-scaled geographical driver variables of these properties and to quantify how the spatial structure of pattern in all of these variables influences the strength of relationships among them. Location and time period: We studied {\textgreater} 8,500 lakes in a 1.8 million km2 area of Northeast U.S.A. Data comprised 10-year medians (2002–2011) for measured ecosystem properties, long-term climate averages and recent land use/land cover variables. Major taxa studied: We focused on ecosystem properties at the base of aquatic food webs, including concentrations of nutrients and algal pigments that are proxies of primary productivity. Methods We quantified spatial structure in ecosystem properties and their geographical driver variables using distance-based Moran eigenvector maps (dbMEMs). We then compared the similarity in spatial structure for all pairs of variables with the correlation between variables to illustrate how spatial structure constrains relationships among ecosystem properties. Results The strength of spatial structure decreased in order for climate, land cover/use, lake ecosystem properties and lake and landscape morphometry. Having a comparable spatial structure is a necessary condition to observe a strong relationship between a pair of variables, but not a sufficient one; variables with very different spatial structure are never strongly correlated. Lake ecosystem properties tended to have an intermediary spatial structure compared with that of their main drivers, probably because climate and landscape variables with known ecological links induce spatial patterns. Main conclusions:Our empirical results describe inherent spatial constraints that dictate the expected relationships between ecosystem properties and their geographical drivers at macroscales. Our results also suggest that understanding the spatial scales at which ecological processes operate is necessary to predict the effects of multi-scaled environmental changes on ecosystem properties.},
	language = {en},
	urldate = {2018-09-20},
	journal = {Global Ecology and Biogeography},
	author = {Lapierre, Jean-Francois and Collins, Sarah M. and Seekell, David A. and Cheruvelil, Kendra Spence and Tan, Pang-Ning and Skaff, Nicholas K. and Taranu, Zofia E. and Fergus, C. Emi and Soranno, Patricia A.},
	month = sep,
	year = {2018},
	note = {00000},
	keywords = {\#nosource, Moran eigenvector maps, climate, ecosystem, lake, landscape, macroscales, spatial autocorrelation, spatial scale, spatial structure},
	pages = {1251--1263},
}

Aim We aimed to measure the dominant spatial patterns in ecosystem properties (such as nutrients and measures of primary production) and the multi-scaled geographical driver variables of these properties and to quantify how the spatial structure of pattern in all of these variables influences the strength of relationships among them. Location and time period: We studied \textgreater 8,500 lakes in a 1.8 million km2 area of Northeast U.S.A. Data comprised 10-year medians (2002–2011) for measured ecosystem properties, long-term climate averages and recent land use/land cover variables. Major taxa studied: We focused on ecosystem properties at the base of aquatic food webs, including concentrations of nutrients and algal pigments that are proxies of primary productivity. Methods We quantified spatial structure in ecosystem properties and their geographical driver variables using distance-based Moran eigenvector maps (dbMEMs). We then compared the similarity in spatial structure for all pairs of variables with the correlation between variables to illustrate how spatial structure constrains relationships among ecosystem properties. Results The strength of spatial structure decreased in order for climate, land cover/use, lake ecosystem properties and lake and landscape morphometry. Having a comparable spatial structure is a necessary condition to observe a strong relationship between a pair of variables, but not a sufficient one; variables with very different spatial structure are never strongly correlated. Lake ecosystem properties tended to have an intermediary spatial structure compared with that of their main drivers, probably because climate and landscape variables with known ecological links induce spatial patterns. Main conclusions:Our empirical results describe inherent spatial constraints that dictate the expected relationships between ecosystem properties and their geographical drivers at macroscales. Our results also suggest that understanding the spatial scales at which ecological processes operate is necessary to predict the effects of multi-scaled environmental changes on ecosystem properties.

@article{krab_winter_2018,
	title = {Winter warming effects on tundra shrub performance are species-specific and dependent on spring conditions},
	volume = {106},
	issn = {1365-2745},
	url = {http://onlinelibrary.wiley.com.proxy.ub.umu.se/doi/10.1111/1365-2745.12872/abstract},
	doi = {10.1111/1365-2745.12872},
	abstract = {1.Climate change driven increases in winter temperatures positively affect conditions for shrub growth in arctic tundra by decreasing plant frost damage and stimulation of nutrient availability. However, the extent to which shrubs may benefit from these conditions may be strongly dependent on the following spring climate. Species-specific differences in phenology and spring frost sensitivity likely affect shrub growth responses to warming. Additionally, effects of changes in winter and spring climate may differ over small spatial scales, as shrub growth may be dependent on natural variation in snow cover, shrub density and cryoturbation. 2.We investigated the effects of winter warming and altered spring climate on growing-season performance of three common and widespread shrub species in cryoturbated non-sorted circle arctic tundra. By insulating sparsely vegetated non-sorted circles and parts of the surrounding heath with additional snow or gardening fleeces we created two climate change scenarios: Snow addition increased soil temperatures in autumn and winter and delayed snowmelt timing without increasing spring temperatures, whereas fleeces increased soil temperature similarly in autumn and winter, but created warmer spring conditions without altering snowmelt timing. 3.Winter warming affected shrub performance, but the direction and magnitude were species-specific and dependent on spring conditions. Spring warming advanced, and later snowmelt delayed canopy green-up. The fleece treatment did not affect shoot growth and biomass in any shrub species despite decreasing leaf frost-damage in E. nigrum. Snow addition decreased frost damage and stimulated growth of V. vitis-idaea by approximately 50\%, while decreasing in B. nana growth (P {\textless} 0.1). All of these effects were consistent in the mostly barren circles and surrounding heath. 4.Synthesis. In cryoturbated arctic tundra, growth of V. vitis-idaea may substantially increase when a thicker snow cover delays snowmelt, whereas in longer-term, warmer winters and springs may favor E. nigrum instead. This may affect shrub community composition and cover, with potentially far-reaching effects on arctic ecosystem functioning via its effects on cryoturbation, carbon cycling and trophic cascading. Our results highlight the importance of disentangling effects of winter and spring climate change timing and nature, as spring conditions are a crucial factor in determining the impact of winter warming on plant performance. This article is protected by copyright. All rights reserved.},
	language = {en},
	urldate = {2017-09-26},
	journal = {Journal of Ecology},
	author = {Krab, Eveline J. and Rönnefarth, Jonas and Becher, Marina and Blume-Werry, Gesche and Keuper, Frida and Klaminder, Jonatan and Kreyling, Juergen and Makoto, Kobayashi and Milbau, Ann and Dorrepaal, Ellen},
	year = {2018},
	note = {00000},
	keywords = {\#nosource, Betula nana, Cryoturbation, Empetrum nigrum, Plant phenology, Vaccinium vitis-idaea, shrubs, snow cover, snowmelt timing, spring climate, winter climate change},
	pages = {599--612},
}

1.Climate change driven increases in winter temperatures positively affect conditions for shrub growth in arctic tundra by decreasing plant frost damage and stimulation of nutrient availability. However, the extent to which shrubs may benefit from these conditions may be strongly dependent on the following spring climate. Species-specific differences in phenology and spring frost sensitivity likely affect shrub growth responses to warming. Additionally, effects of changes in winter and spring climate may differ over small spatial scales, as shrub growth may be dependent on natural variation in snow cover, shrub density and cryoturbation. 2.We investigated the effects of winter warming and altered spring climate on growing-season performance of three common and widespread shrub species in cryoturbated non-sorted circle arctic tundra. By insulating sparsely vegetated non-sorted circles and parts of the surrounding heath with additional snow or gardening fleeces we created two climate change scenarios: Snow addition increased soil temperatures in autumn and winter and delayed snowmelt timing without increasing spring temperatures, whereas fleeces increased soil temperature similarly in autumn and winter, but created warmer spring conditions without altering snowmelt timing. 3.Winter warming affected shrub performance, but the direction and magnitude were species-specific and dependent on spring conditions. Spring warming advanced, and later snowmelt delayed canopy green-up. The fleece treatment did not affect shoot growth and biomass in any shrub species despite decreasing leaf frost-damage in E. nigrum. Snow addition decreased frost damage and stimulated growth of V. vitis-idaea by approximately 50%, while decreasing in B. nana growth (P \textless 0.1). All of these effects were consistent in the mostly barren circles and surrounding heath. 4.Synthesis. In cryoturbated arctic tundra, growth of V. vitis-idaea may substantially increase when a thicker snow cover delays snowmelt, whereas in longer-term, warmer winters and springs may favor E. nigrum instead. This may affect shrub community composition and cover, with potentially far-reaching effects on arctic ecosystem functioning via its effects on cryoturbation, carbon cycling and trophic cascading. Our results highlight the importance of disentangling effects of winter and spring climate change timing and nature, as spring conditions are a crucial factor in determining the impact of winter warming on plant performance. This article is protected by copyright. All rights reserved.

@article{berdan_inversion_2018,
	title = {Inversion frequencies and phenotypic effects are modulated by the environment: insights from a reciprocal transplant study in {Coelopa} frigida},
	volume = {32},
	issn = {1573-8477},
	shorttitle = {Inversion frequencies and phenotypic effects are modulated by the environment},
	url = {https://doi.org/10.1007/s10682-018-9960-5},
	doi = {10.1007/s10682-018-9960-5},
	abstract = {Understanding how environmental variation drives phenotypic diversification within species is a major objective in evolutionary biology. The seaweed fly Coelopa frigida provides an excellent model for the study of genetically driven phenotypes because it carries an α/β inversion polymorphism that affects body size. Coelopa frigida inhabits highly variable beds of decomposing seaweed on the coast in Scandinavia thus providing a suitable test ground to investigate the genetic effects of substrate on both the frequency of the inversion (directional selection) and on the phenotype (genotype × environment effects). Here we use a reciprocal transplant experiment to test the effect of the α/β inversion on body size traits and development time across four suitable natural breeding substrates from the clinal distribution. We show that while development time is unaffected by G × E effects, both the frequency of the inversion and the relative phenotypic effects of the inversion on body size differ between population × substrate combinations. This indicates that the environment modulates the fitness as well as the phenotypic effects of the inversion karyotypes. It further suggests that the inversion may have accumulated qualitatively different mutations in different populations that interact with the environment. Together our results are consistent with the idea that the inversion in C. frigida likely evolves via a combination of local mutation, G × E effects, and differential fitness of inversion karyotypes in heterogeneous environments.},
	language = {en},
	number = {6},
	urldate = {2018-10-25},
	journal = {Evolutionary Ecology},
	author = {Berdan, Emma and Rosenquist, Hanna and Larson, Keith and Wellenreuther, Maren},
	month = oct,
	year = {2018},
	keywords = {\#nosource, Adaptation, Coelopa frigida, Frequency effects, G × E interactions, Inversion polymorphism},
	pages = {683--698},
}

Understanding how environmental variation drives phenotypic diversification within species is a major objective in evolutionary biology. The seaweed fly Coelopa frigida provides an excellent model for the study of genetically driven phenotypes because it carries an α/β inversion polymorphism that affects body size. Coelopa frigida inhabits highly variable beds of decomposing seaweed on the coast in Scandinavia thus providing a suitable test ground to investigate the genetic effects of substrate on both the frequency of the inversion (directional selection) and on the phenotype (genotype × environment effects). Here we use a reciprocal transplant experiment to test the effect of the α/β inversion on body size traits and development time across four suitable natural breeding substrates from the clinal distribution. We show that while development time is unaffected by G × E effects, both the frequency of the inversion and the relative phenotypic effects of the inversion on body size differ between population × substrate combinations. This indicates that the environment modulates the fitness as well as the phenotypic effects of the inversion karyotypes. It further suggests that the inversion may have accumulated qualitatively different mutations in different populations that interact with the environment. Together our results are consistent with the idea that the inversion in C. frigida likely evolves via a combination of local mutation, G × E effects, and differential fitness of inversion karyotypes in heterogeneous environments.

@article{fahlman_using_2018,
	title = {Using laboratory incubations to predict the fate of pharmaceuticals in aquatic ecosystems},
	volume = {15},
	issn = {1449-8979},
	url = {http://www.publish.csiro.au/EN/EN18154},
	doi = {10.1071/EN18154},
	abstract = {Environmental context Environmental persistence of excreted pharmaceuticals in aquatic ecosystems is usually predicted using small-scale laboratory experiments assumed to simulate natural conditions. We studied five pharmaceuticals comparing their removal rates from water under laboratory conditions and under natural environmental conditions existing in a large pond. We found that the laboratory conditions did not fully capture the complexity within the pond, which led to different removal rates in the two systems. Abstract Environmental persistence is a key property when evaluating risks with excreted pharmaceuticals in aquatic ecosystems. Such persistence is typically predicted using small-scale laboratory incubations, but the variation in aquatic environments and scarcity of field studies to verify laboratory-based persistence estimates create uncertainties around the predictive power of these incubations. In this study we: (1) assess the persistence of five pharmaceuticals (diclofenac, diphenhydramine, hydroxyzine, trimethoprim and oxazepam) in laboratory experiments under different environmental conditions; and (2) use a three-month-long field study in an aquatic ecosystem to verify the laboratory-based persistence estimates. In our laboratory assays, we found that water temperature (TEMP), concentrations of organic solutes (TOC), presence of sediment (SED), and solar radiation (SOL) individually affected dissipation rates. Moreover, we identified rarely studied interaction effects between the treatments (i.e. SOL × SED and TEMP × SOL), which affected the persistence of the studied drugs. Half-lives obtained from the laboratory assays largely explained the dissipation rates during the first week of the field study. However, none of the applied models could accurately predict the long-term dissipation rates (month time-scale) from the water column. For example, the studied antibioticum (trimethoprim) and the anti-anxiety drug (oxazepam) remained at detectable levels in the aquatic environment long after ({\textasciitilde}150 days) our laboratory based models predicted complete dissipation. We conclude that small-scale laboratory incubations seem sufficient to approximate the short-term (i.e. within a week) dissipation rate of drugs in aquatic ecosystems. However, this simplistic approach does not capture interacting environmental processes that preserve a fraction of the dissolved pharmaceuticals for months in natural water bodies.},
	language = {en},
	number = {8},
	urldate = {2019-02-21},
	journal = {Environmental Chemistry},
	author = {Fahlman, Johan and Fick, Jerker and Karlsson, Jan and Jonsson, Micael and Brodin, Tomas and Klaminder, Jonatan},
	month = nov,
	year = {2018},
	keywords = {\#nosource},
	pages = {463--471},
}

Environmental context Environmental persistence of excreted pharmaceuticals in aquatic ecosystems is usually predicted using small-scale laboratory experiments assumed to simulate natural conditions. We studied five pharmaceuticals comparing their removal rates from water under laboratory conditions and under natural environmental conditions existing in a large pond. We found that the laboratory conditions did not fully capture the complexity within the pond, which led to different removal rates in the two systems. Abstract Environmental persistence is a key property when evaluating risks with excreted pharmaceuticals in aquatic ecosystems. Such persistence is typically predicted using small-scale laboratory incubations, but the variation in aquatic environments and scarcity of field studies to verify laboratory-based persistence estimates create uncertainties around the predictive power of these incubations. In this study we: (1) assess the persistence of five pharmaceuticals (diclofenac, diphenhydramine, hydroxyzine, trimethoprim and oxazepam) in laboratory experiments under different environmental conditions; and (2) use a three-month-long field study in an aquatic ecosystem to verify the laboratory-based persistence estimates. In our laboratory assays, we found that water temperature (TEMP), concentrations of organic solutes (TOC), presence of sediment (SED), and solar radiation (SOL) individually affected dissipation rates. Moreover, we identified rarely studied interaction effects between the treatments (i.e. SOL × SED and TEMP × SOL), which affected the persistence of the studied drugs. Half-lives obtained from the laboratory assays largely explained the dissipation rates during the first week of the field study. However, none of the applied models could accurately predict the long-term dissipation rates (month time-scale) from the water column. For example, the studied antibioticum (trimethoprim) and the anti-anxiety drug (oxazepam) remained at detectable levels in the aquatic environment long after (~150 days) our laboratory based models predicted complete dissipation. We conclude that small-scale laboratory incubations seem sufficient to approximate the short-term (i.e. within a week) dissipation rate of drugs in aquatic ecosystems. However, this simplistic approach does not capture interacting environmental processes that preserve a fraction of the dissolved pharmaceuticals for months in natural water bodies.

@article{althuizen_long-term_2018,
	title = {Long-{Term} {Climate} {Regime} {Modulates} the {Impact} of {Short}-{Term} {Climate} {Variability} on {Decomposition} in {Alpine} {Grassland} {Soils}},
	volume = {21},
	issn = {1435-0629},
	url = {https://doi.org/10.1007/s10021-018-0241-5},
	doi = {10.1007/s10021-018-0241-5},
	abstract = {Decomposition of plant litter is an important process in the terrestrial carbon cycle and makes up approximately 70\% of the global carbon flux from soils to the atmosphere. Climate change is expected to have significant direct and indirect effects on the litter decomposition processes at various timescales. Using the TeaBag Index, we investigated the impact on decomposition of short-term direct effects of temperature and precipitation by comparing temporal variability over years, versus long-term climate impacts that incorporate indirect effects mediated through environmental changes by comparing sites along climatic gradients. We measured the initial decomposition rate (k) and the stabilization factor (S; amount of labile litter stabilizing) across a climate grid combining three levels of summer temperature (6.5–10.5°C) with four levels of annual precipitation (600–2700 mm) in three summers with varying temperature and precipitation. Several (a)biotic factors were measured to characterize environmental differences between sites. Increased temperatures enhanced k, whereas increased precipitation decreased k across years and climatic regimes. In contrast, S showed diverse responses to annual changes in temperature and precipitation between climate regimes. Stabilization of labile litter fractions increased with temperature only in boreal and sub-alpine sites, while it decreased with increasing precipitation only in sub-alpine and alpine sites. Environmental factors such as soil pH, soil C/N, litter C/N, and plant diversity that are associated with long-term climate variation modulate the response of k and S. This highlights the importance of long-term climate in shaping the environmental conditions that influences the response of decomposition processes to climate change.},
	language = {en},
	number = {8},
	urldate = {2019-04-05},
	journal = {Ecosystems},
	author = {Althuizen, Inge H. J. and Lee, Hanna and Sarneel, Judith M. and Vandvik, Vigdis},
	month = dec,
	year = {2018},
	keywords = {\#nosource, annual variability, climate change, decomposition, grassland, litter bag, precipitation, tea bag index, temperature},
	pages = {1580--1592},
}

Decomposition of plant litter is an important process in the terrestrial carbon cycle and makes up approximately 70% of the global carbon flux from soils to the atmosphere. Climate change is expected to have significant direct and indirect effects on the litter decomposition processes at various timescales. Using the TeaBag Index, we investigated the impact on decomposition of short-term direct effects of temperature and precipitation by comparing temporal variability over years, versus long-term climate impacts that incorporate indirect effects mediated through environmental changes by comparing sites along climatic gradients. We measured the initial decomposition rate (k) and the stabilization factor (S; amount of labile litter stabilizing) across a climate grid combining three levels of summer temperature (6.5–10.5°C) with four levels of annual precipitation (600–2700 mm) in three summers with varying temperature and precipitation. Several (a)biotic factors were measured to characterize environmental differences between sites. Increased temperatures enhanced k, whereas increased precipitation decreased k across years and climatic regimes. In contrast, S showed diverse responses to annual changes in temperature and precipitation between climate regimes. Stabilization of labile litter fractions increased with temperature only in boreal and sub-alpine sites, while it decreased with increasing precipitation only in sub-alpine and alpine sites. Environmental factors such as soil pH, soil C/N, litter C/N, and plant diversity that are associated with long-term climate variation modulate the response of k and S. This highlights the importance of long-term climate in shaping the environmental conditions that influences the response of decomposition processes to climate change.

@article{nilsson_ecological_2018,
	title = {Ecological {Restoration} as a {Means} of {Managing} {Inland} {Flood} {Hazards}},
	volume = {68},
	issn = {0006-3568},
	url = {https://academic.oup.com/bioscience/article/68/2/89/4797263},
	doi = {10.1093/biosci/bix148},
	abstract = {Abstract.  Many streams and rivers experience major floods. Historically, human societies have responded to such floods by moving away from them or by abating t},
	language = {en},
	number = {2},
	urldate = {2019-03-27},
	journal = {BioScience},
	author = {Nilsson, Christer and Riis, Tenna and Sarneel, Judith M. and Svavarsdóttir, Kristín},
	month = feb,
	year = {2018},
	keywords = {\#nosource},
	pages = {89--99},
}

Abstract. Many streams and rivers experience major floods. Historically, human societies have responded to such floods by moving away from them or by abating t

@article{polvi_ecosystem_2018,
	title = {Ecosystem engineers in rivers: {An} introduction to how and where organisms create positive biogeomorphic feedbacks},
	volume = {5},
	copyright = {© 2017 Wiley Periodicals, Inc.},
	issn = {2049-1948},
	shorttitle = {Ecosystem engineers in rivers},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/wat2.1271},
	doi = {10.1002/wat2.1271},
	abstract = {Ecosystem engineers substantially alter physical flow characteristics and shape a river's form and function. Because the recurrence interval of geomorphic processes and disturbances in rivers commonly match the temporal scale of plants’ life cycles or alterations by animals, the resulting feedbacks are an important component of rivers. In this review, we focus on biota that directly or indirectly induce a physical change in rivers and cause positive feedbacks on the functioning of that organism. We provide an overview of how various ecosystem engineers affect rivers at different temporal and spatial scales and plot them on a conceptual gradient of river types. Various plants engineer the river environment through stabilizing sediment and reducing flow velocities, including macrophytes, woody plants, and algal mats and biofilms. Among animals that engineer, beaver that build dams cause substantial changes to river dynamics. In addition, benthic macroinvertebrates and mussels can stabilize sediment and reduce velocities, and aquatic and riparian grazers modulate the effect of plants. Humans are also considered river ecosystem engineers. Most of the ecosystem engineers reported in literature occur in rivers with low to intermediate relative stability, intermediate channel widths, and small to intermediate grain sizes. Ecosystem engineers that create positive biogeomorphic feedbacks are important to take into account when managing river systems, as many common invasive species are successful due to their engineering capabilities. River restoration can use ecosystem engineers to spur holistic recovery. Future research points towards examining ecosystem engineers on longer spatial and temporal scales and understanding the co-evolution of organisms and landforms through engineering. WIREs Water 2018, 5:e1271. doi: 10.1002/wat2.1271 This article is categorized under: Water and Life {\textgreater} Nature of Freshwater Ecosystems Water and Life {\textgreater} Conservation, Management, and Awareness},
	language = {en},
	number = {2},
	urldate = {2019-03-27},
	journal = {Wiley Interdisciplinary Reviews: Water},
	author = {Polvi, Lina E. and Sarneel, Judith M.},
	year = {2018},
	keywords = {\#nosource},
	pages = {e1271},
}

Ecosystem engineers substantially alter physical flow characteristics and shape a river's form and function. Because the recurrence interval of geomorphic processes and disturbances in rivers commonly match the temporal scale of plants’ life cycles or alterations by animals, the resulting feedbacks are an important component of rivers. In this review, we focus on biota that directly or indirectly induce a physical change in rivers and cause positive feedbacks on the functioning of that organism. We provide an overview of how various ecosystem engineers affect rivers at different temporal and spatial scales and plot them on a conceptual gradient of river types. Various plants engineer the river environment through stabilizing sediment and reducing flow velocities, including macrophytes, woody plants, and algal mats and biofilms. Among animals that engineer, beaver that build dams cause substantial changes to river dynamics. In addition, benthic macroinvertebrates and mussels can stabilize sediment and reduce velocities, and aquatic and riparian grazers modulate the effect of plants. Humans are also considered river ecosystem engineers. Most of the ecosystem engineers reported in literature occur in rivers with low to intermediate relative stability, intermediate channel widths, and small to intermediate grain sizes. Ecosystem engineers that create positive biogeomorphic feedbacks are important to take into account when managing river systems, as many common invasive species are successful due to their engineering capabilities. River restoration can use ecosystem engineers to spur holistic recovery. Future research points towards examining ecosystem engineers on longer spatial and temporal scales and understanding the co-evolution of organisms and landforms through engineering. WIREs Water 2018, 5:e1271. doi: 10.1002/wat2.1271 This article is categorized under: Water and Life \textgreater Nature of Freshwater Ecosystems Water and Life \textgreater Conservation, Management, and Awareness

@article{berggren_quality_2018,
	title = {Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes},
	volume = {15},
	issn = {1726-4189},
	shorttitle = {Quality transformation of dissolved organic carbon during water transit through lakes},
	url = {https://www.biogeosciences.net/15/457/2018/},
	doi = {10.5194/bg-15-457-2018},
	abstract = {Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm  {\textgreater} 7 m−1) biological processes dominated, and there was no systematic relationship between color loss and WTT. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.},
	number = {2},
	urldate = {2018-02-13},
	journal = {Biogeosciences},
	author = {Berggren, M. and Klaus, M. and Selvam, B. P. and Ström, L. and Laudon, H. and Jansson, M. and Karlsson, J.},
	month = jan,
	year = {2018},
	note = {00000},
	keywords = {\#nosource},
	pages = {457--470},
}

Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm  \textgreater 7 m−1) biological processes dominated, and there was no systematic relationship between color loss and WTT. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.