\n

\n \n 2024\n \n \n (1)\n \n \n

\n

\n \n \n

\n \n\n \n \n \n \n \n \n Short- and long-term plant and microbial uptake of 15N-labelled urea in a mesic tundra heath, West Greenland.\n \n \n \n \n\n\n \n Barthelemy, H.; Nobel, L. A.; Stark, S.; Väisänen, M.; Olofsson, J.; and Michelsen, A.\n\n\n \n\n\n\n Polar Biology, 47(1): 1–15. 2024.\n Publisher: Springer Nature\n\n\n\n
\n\n\n\n \n \n $\"Short-$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{barthelemy_short-_2024,\n\ttitle = {Short- and long-term plant and microbial uptake of {15N}-labelled urea in a mesic tundra heath, {West} {Greenland}},\n\tvolume = {47},\n\turl = {https://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-216900},\n\tdoi = {10.1007/s00300-023-03209-6},\n\tabstract = {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  ...},\n\tlanguage = {eng},\n\tnumber = {1},\n\turldate = {2024-03-26},\n\tjournal = {Polar Biology},\n\tauthor = {Barthelemy, Hélène and Nobel, Liv Alexa and Stark, Sari and Väisänen, Maria and Olofsson, Johan and Michelsen, Anders},\n\tyear = {2024},\n\tnote = {Publisher: Springer Nature},\n\tpages = {1--15},\n}\n\n

\n

\n\n\n\n\n\n

\n

\n \n 2023\n \n \n (1)\n \n \n

\n

\n \n \n

\n \n\n \n \n \n \n \n \n Tundra cryogenic land surface processes and CO2–C balance in sub-Arctic alpine environment withstand winter and spring warming.\n \n \n \n \n\n\n \n Väisänen, M.; Klaminder, J.; Ylänne, H.; Teuber, L.; Dorrepaal, E.; and Krab, E. J.\n\n\n \n\n\n\n Environmental Research: Climate, 2(2): 021001. March 2023.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Tundra$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

\n

@article{vaisanen_tundra_2023,\n\ttitle = {Tundra cryogenic land surface processes and {CO2}–{C} balance in sub-{Arctic} alpine environment withstand winter and spring warming},\n\tvolume = {2},\n\tissn = {2752-5295},\n\turl = {https://dx.doi.org/10.1088/2752-5295/acc08b},\n\tdoi = {10.1088/2752-5295/acc08b},\n\tabstract = {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.},\n\tlanguage = {en},\n\tnumber = {2},\n\turldate = {2024-03-27},\n\tjournal = {Environmental Research: Climate},\n\tauthor = {Väisänen, Maria and Klaminder, Jonatan and Ylänne, Henni and Teuber, Laurenz and Dorrepaal, Ellen and Krab, Eveline J.},\n\tmonth = mar,\n\tyear = {2023},\n\tnote = {Publisher: IOP Publishing},\n\tkeywords = {\\#nosource},\n\tpages = {021001},\n}\n\n

\n

\n\n\n\n\n\n

\n

\n \n 2022\n \n \n (1)\n \n \n

\n

\n \n \n

\n \n\n \n \n \n \n \n \n Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types.\n \n \n \n \n\n\n \n Gavazov, K.; Canarini, A.; Jassey, V. E. J.; Mills, R.; Richter, A.; Sundqvist, M. K.; Väisänen, M.; Walker, T. W. N.; Wardle, D. A.; and Dorrepaal, E.\n\n\n \n\n\n\n Soil Biology and Biochemistry, 165: 108530. February 2022.\n \n\n\n\n
\n\n\n\n \n \n $\"Plant-microbial$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{gavazov_plant-microbial_2022,\n\ttitle = {Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types},\n\tvolume = {165},\n\tissn = {0038-0717},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0038071721004041},\n\tdoi = {10.1016/j.soilbio.2021.108530},\n\tabstract = {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.},\n\tlanguage = {en},\n\turldate = {2022-01-20},\n\tjournal = {Soil Biology and Biochemistry},\n\tauthor = {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},\n\tmonth = feb,\n\tyear = {2022},\n\tkeywords = {\\#nosource, Above- and belowground interactions, C:N stoichiometry, Carbon use efficiency, Elevation gradient, Microbial physiology, Primary productivity},\n\tpages = {108530},\n}\n\n

\n

\n\n\n

\n 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.\n

\n\n\n

\n\n\n\n\n\n

\n

\n \n 2021\n \n \n (1)\n \n \n

\n

\n \n \n

\n \n\n \n \n \n \n \n \n Metabolism overrides photo-oxidation in CO2 dynamics of Arctic permafrost streams.\n \n \n \n \n\n\n \n Rocher-Ros, G.; Harms, T. K.; Sponseller, R. A.; Väisänen, M.; Mörth, C.; and Giesler, R.\n\n\n \n\n\n\n Limnology and Oceanography, 66(S1): S169–S181. 2021.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11564\n\n\n\n
\n\n\n\n \n \n $\"Metabolism$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

\n

@article{rocher-ros_metabolism_2021,\n\ttitle = {Metabolism overrides photo-oxidation in {CO2} dynamics of {Arctic} permafrost streams},\n\tvolume = {66},\n\tcopyright = {© 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.},\n\tissn = {1939-5590},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11564},\n\tdoi = {10.1002/lno.11564},\n\tabstract = {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.},\n\tlanguage = {en},\n\tnumber = {S1},\n\turldate = {2024-03-27},\n\tjournal = {Limnology and Oceanography},\n\tauthor = {Rocher-Ros, Gerard and Harms, Tamara K. and Sponseller, Ryan A. and Väisänen, Maria and Mörth, Carl-Magnus and Giesler, Reiner},\n\tyear = {2021},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/lno.11564},\n\tkeywords = {\\#nosource},\n\tpages = {S169--S181},\n}\n\n

\n

\n\n\n\n\n\n

\n

\n \n 2020\n \n \n (3)\n \n \n

\n

\n \n \n

\n \n\n \n \n \n \n \n \n Invasive earthworms unlock arctic plant nitrogen limitation.\n \n \n \n \n\n\n \n Blume-Werry, G.; Krab, E. J.; Olofsson, J.; Sundqvist, M. K.; Väisänen, M.; and Klaminder, J.\n\n\n \n\n\n\n Nature Communications, 11(1): 1–10. April 2020.\n Number: 1 Publisher: Nature Publishing Group\n\n\n\n
\n\n\n\n \n \n $\"Invasive$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

\n

@article{blume-werry_invasive_2020,\n\ttitle = {Invasive earthworms unlock arctic plant nitrogen limitation},\n\tvolume = {11},\n\tcopyright = {2020 The Author(s)},\n\tissn = {2041-1723},\n\turl = {https://www.nature.com/articles/s41467-020-15568-3},\n\tdoi = {10.1038/s41467-020-15568-3},\n\tabstract = {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.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2020-04-23},\n\tjournal = {Nature Communications},\n\tauthor = {Blume-Werry, Gesche and Krab, Eveline J. and Olofsson, Johan and Sundqvist, Maja K. and Väisänen, Maria and Klaminder, Jonatan},\n\tmonth = apr,\n\tyear = {2020},\n\tnote = {Number: 1\nPublisher: Nature Publishing Group},\n\tkeywords = {\\#nosource},\n\tpages = {1--10},\n}\n\n

\n

\n\n\n\n\n\n

\n\n\n

\n \n\n \n \n \n \n \n \n Meshes in mesocosms control solute and biota exchange in soils: A step towards disentangling (a)biotic impacts on the fate of thawing permafrost.\n \n \n \n \n\n\n \n Väisänen, M.; Krab, E. J.; Monteux, S.; Teuber, L. M.; Gavazov, K.; Weedon, J. T.; Keuper, F.; and Dorrepaal, E.\n\n\n \n\n\n\n Applied Soil Ecology, 151: 103537. July 2020.\n \n\n\n\n
\n\n\n\n \n \n $\"Meshes$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{vaisanen_meshes_2020,\n\ttitle = {Meshes in mesocosms control solute and biota exchange in soils: {A} step towards disentangling (a)biotic impacts on the fate of thawing permafrost},\n\tvolume = {151},\n\tissn = {0929-1393},\n\tshorttitle = {Meshes in mesocosms control solute and biota exchange in soils},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0929139319307206},\n\tdoi = {10.1016/j.apsoil.2020.103537},\n\tabstract = {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.},\n\tlanguage = {en},\n\turldate = {2020-04-23},\n\tjournal = {Applied Soil Ecology},\n\tauthor = {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},\n\tmonth = jul,\n\tyear = {2020},\n\tkeywords = {\\#nosource, Bacterial community, Faunal inoculation, Field incubation, Lateral soil connection, Nitrogen, Root},\n\tpages = {103537},\n}\n\n

\n

\n\n\n\n\n\n

\n\n\n

\n \n\n \n \n \n \n \n \n Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability.\n \n \n \n \n\n\n \n Ylänne, H.; Kaarlejärvi, E.; Väisänen, M.; Männistö, M. K.; Ahonen, S. H. K.; Olofsson, J.; and Stark, S.\n\n\n \n\n\n\n Ecological Monographs, 90(1): e01396. 2020.\n _eprint: https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecm.1396\n\n\n\n
\n\n\n\n \n \n $\"Removal$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{ylanne_removal_2020,\n\ttitle = {Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability},\n\tvolume = {90},\n\tcopyright = {© 2019 by the Ecological Society of America},\n\tissn = {1557-7015},\n\turl = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1396},\n\tdoi = {10.1002/ecm.1396},\n\tabstract = {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.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2020-03-19},\n\tjournal = {Ecological Monographs},\n\tauthor = {Ylänne, Henni and Kaarlejärvi, Elina and Väisänen, Maria and Männistö, Minna K. and Ahonen, Saija H. K. and Olofsson, Johan and Stark, Sari},\n\tyear = {2020},\n\tnote = {\\_eprint: https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecm.1396},\n\tkeywords = {\\#nosource, Rangifer tarandus, SEM, fertilization, herbivory, land use, open-top chamber, reindeer, soil carbon storage},\n\tpages = {e01396},\n}\n\n

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\n\n\n\n\n\n

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\n \n 2019\n \n \n (2)\n \n \n

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\n \n \n

\n \n\n \n \n \n \n \n \n Herbivore Effects on Ecosystem Process Rates in a Low-Productive System.\n \n \n \n \n\n\n \n Tuomi, M.; Stark, S.; Hoset, K. S.; Väisänen, M.; Oksanen, L.; Murguzur, F. J. A.; Tuomisto, H.; Dahlgren, J.; and Bråthen, K. A.\n\n\n \n\n\n\n Ecosystems, 22(4): 827–843. June 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Herbivore$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{tuomi_herbivore_2019,\n\ttitle = {Herbivore {Effects} on {Ecosystem} {Process} {Rates} in a {Low}-{Productive} {System}},\n\tvolume = {22},\n\tissn = {1435-0629},\n\turl = {https://doi.org/10.1007/s10021-018-0307-4},\n\tdoi = {10.1007/s10021-018-0307-4},\n\tabstract = {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.},\n\tlanguage = {en},\n\tnumber = {4},\n\turldate = {2024-03-27},\n\tjournal = {Ecosystems},\n\tauthor = {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},\n\tmonth = jun,\n\tyear = {2019},\n\tkeywords = {\\#nosource, NIRS, Northern Fennoscandia, dwarf shrub tundra, microbial activity, microtine rodent, plant community traits, plant–soil interactions, soil N and P},\n\tpages = {827--843},\n}\n\n

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\n\n\n\n\n\n

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\n \n\n \n \n \n \n \n \n The Legacy Effects of Winter Climate on Microbial Functioning After Snowmelt in a Subarctic Tundra.\n \n \n \n \n\n\n \n Väisänen, M.; Gavazov, K.; Krab, E. J.; and Dorrepaal, E.\n\n\n \n\n\n\n Microbial Ecology, 77(1): 186–190. January 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

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@article{vaisanen_legacy_2019,\n\ttitle = {The {Legacy} {Effects} of {Winter} {Climate} on {Microbial} {Functioning} {After} {Snowmelt} in a {Subarctic} {Tundra}},\n\tvolume = {77},\n\tissn = {1432-184X},\n\turl = {https://doi.org/10.1007/s00248-018-1213-1},\n\tdoi = {10.1007/s00248-018-1213-1},\n\tabstract = {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.},\n\tnumber = {1},\n\tjournal = {Microbial Ecology},\n\tauthor = {Väisänen, Maria and Gavazov, Konstantin and Krab, Eveline J. and Dorrepaal, Ellen},\n\tmonth = jan,\n\tyear = {2019},\n\tkeywords = {\\#nosource},\n\tpages = {186--190},\n}\n\n

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\n \n 2017\n \n \n (1)\n \n \n

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\n \n\n \n \n \n \n \n \n Carbon dynamics at frost-patterned tundra driven by long-term vegetation change rather than by short-term non-growing season warming.\n \n \n \n \n\n\n \n Väisänen, M.; Krab, E. J.; and Dorrepaal, E.\n\n\n \n\n\n\n Biogeochemistry, 136(1): 103–117. October 2017.\n 00000\n\n\n\n
\n\n\n\n \n \n $\"Carbon$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

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@article{vaisanen_carbon_2017,\n\ttitle = {Carbon dynamics at frost-patterned tundra driven by long-term vegetation change rather than by short-term non-growing season warming},\n\tvolume = {136},\n\tissn = {0168-2563, 1573-515X},\n\turl = {https://link.springer.com/article/10.1007/s10533-017-0385-y},\n\tdoi = {10.1007/s10533-017-0385-y},\n\tabstract = {Frost-patterned grounds, such as mostly barren frost boils surrounded by denser vegetation, are typical habitat mosaics in tundra. Plant and microbial processes in these habitats may be susceptible to short-term warming outside the growing season, while the areal cover of barren frost boils has decreased during the past decades due to climate warming-induced shrub expansion. The relative importance of such short-term and long-term climate impacts on carbon (C) dynamics remains unknown. We measured ecosystem CO2 uptake and release (in the field), microbial respiration (in the laboratory), as well as microbial biomass N and soil extractable N in frost boils and the directly adjacent heath in late spring and late summer. These habitats had been experimentally warmed with insulating fleeces from late September until late May for three consecutive years, which allowed us to investigate the direct short-term effects of warming and longer-term, indirect climate effects via vegetation establishment into frost boils. Non-growing season warming increased C uptake at the frost boils in late spring and decreased it in late summer, while the timing and direction of responses was opposite for the heath. Experimental warming had no effects on microbial or ecosystem C release or soil N at either of the habitats. However, C cycling was manifold higher at the heath compared to the frost boils, likely because of a higher SOM stock in the soil. Short-term climate change can thus directly alter ecosystem C uptake at frost-patterned grounds but will most likely not affect microbial C release. We conclude that the C dynamics at frost-patterned grounds under a changing climate depend most strongly on the potential of vegetation to encroach into frost boils in the long-term.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2017-11-17},\n\tjournal = {Biogeochemistry},\n\tauthor = {Väisänen, Maria and Krab, Eveline J. and Dorrepaal, Ellen},\n\tmonth = oct,\n\tyear = {2017},\n\tnote = {00000},\n\tkeywords = {\\#nosource},\n\tpages = {103--117},\n}\n\n

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\n \n 2015\n \n \n (1)\n \n \n

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\n \n\n \n \n \n \n \n \n Long-term reindeer grazing limits warming-induced increases in CO 2 released by tundra heath soil: potential role of soil C quality.\n \n \n \n \n\n\n \n Väisänen, M.; Sjögersten, S.; Large, D.; Drage, T.; and Stark, S.\n\n\n \n\n\n\n Environmental Research Letters, 10(9): 094020. 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Long-term$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

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@article{vaisanen_long-term_2015,\n\ttitle = {Long-term reindeer grazing limits warming-induced increases in {CO} 2 released by tundra heath soil: potential role of soil {C} quality},\n\tvolume = {10},\n\tissn = {1748-9326},\n\tshorttitle = {Long-term reindeer grazing limits warming-induced increases in {CO} 2 released by tundra heath soil},\n\turl = {http://stacks.iop.org/1748-9326/10/i=9/a=094020},\n\tdoi = {10.1088/1748-9326/10/9/094020},\n\tabstract = {The current climate warming in the Arctic may increase the microbial degradation of vast pools of soil carbon (C); however, the temperature sensitivity of decomposition is often highly dependent on the quality of accumulated soil C. Grazing by reindeer ( Rangifer tarandus L.) substantially affects the dominant vegetation and often increases graminoids in relation to dwarf shrubs in ecosystems, but the effect of this vegetation shift on the soil C quality has not been previously investigated. We analyzed the soil C quality and rate of microbially mediated CO 2 release at different temperatures in long-term laboratory incubations using soils from lightly grazed dwarf shrub-dominated and heavily grazed graminoid-dominated tundra ecosystem. The soil C quality was characterized by solid-state cross-polarization magic angle spinning (CPMAS 13 C NMR) spectroscopy, which showed a higher relative proportion of carbohydrate C under light grazing and higher relative proportion of aliphatic not-O-substituted C under heavy grazing. Initial measurements showed lower temperature sensitivity of the CO 2 release in soils under light grazing compared with soil under heavy grazing, but the overall CO 2 release rate and its temperature sensitivity increased under light grazing as the soil incubation progressed. At the end of incubation, significantly more carbohydrate C had been lost in soils under light grazing compared with heavy grazing. These findings indicate that there may be a link between the grazer-induced effects on soil C quality and the potential of soils to release CO 2 to atmosphere. We suggest that vegetation shifts induced by grazing could influence the proportion of accumulated soil C that is vulnerable to microbial degradation under warming climate.},\n\tlanguage = {en},\n\tnumber = {9},\n\turldate = {2017-05-27},\n\tjournal = {Environmental Research Letters},\n\tauthor = {Väisänen, Maria and Sjögersten, Sofie and Large, David and Drage, Trevor and Stark, Sari},\n\tyear = {2015},\n\tkeywords = {\\#nosource},\n\tpages = {094020},\n}\n\n

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\n \n 2014\n \n \n (2)\n \n \n

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\n \n\n \n \n \n \n \n \n Consequences of warming on tundra carbon balance determined by reindeer grazing history.\n \n \n \n \n\n\n \n Väisänen, M.; Ylänne, H.; Kaarlejärvi, E.; Sjögersten, S.; Olofsson, J.; Crout, N.; and Stark, S.\n\n\n \n\n\n\n Nature Climate Change, 4(5): 384–388. May 2014.\n 00026\n\n\n\n
\n\n\n\n \n \n $\"Consequences$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{vaisanen_consequences_2014,\n\ttitle = {Consequences of warming on tundra carbon balance determined by reindeer grazing history},\n\tvolume = {4},\n\tcopyright = {© 2014 Nature Publishing Group},\n\tissn = {1758-678X},\n\turl = {http://www.nature.com/nclimate/journal/v4/n5/full/nclimate2147.html},\n\tdoi = {10.1038/nclimate2147},\n\tabstract = {Arctic tundra currently stores half of the global soil carbon (C) stock. Climate warming in the Arctic may lead to accelerated CO2 release through enhanced decomposition and turn Arctic ecosystems from a net C sink into a net C source, if warming enhances decomposition more than plant photosynthesis. A large portion of the circumpolar Arctic is grazed by reindeer/caribou, and grazing causes important vegetation shifts in the long-term. Using a unique experimental set-up, where areas experiencing more than 50 years of either light (LG) or heavy (HG) grazing were warmed and/or fertilized, we show that under ambient conditions areas under LG were a 70\\% stronger C sink than HG areas. Although warming decreased the C sink by 38\\% under LG, it had no effect under HG. Grazing history will thus be an important determinant in the response of ecosystem C balance to climate warming, which at present is not taken into account in climate change models.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2017-02-08},\n\tjournal = {Nature Climate Change},\n\tauthor = {Väisänen, Maria and Ylänne, Henni and Kaarlejärvi, Elina and Sjögersten, Sofie and Olofsson, Johan and Crout, Neil and Stark, Sari},\n\tmonth = may,\n\tyear = {2014},\n\tnote = {00026},\n\tkeywords = {\\#nosource, Climate-change ecology, Climate-change impacts},\n\tpages = {384--388},\n}\n\n

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\n \n\n \n \n \n \n \n \n Insensitivity of Soil Microbial Activity to Temporal Variation in Soil N in Subarctic Tundra: Evidence from Responses to Large Migratory Grazers.\n \n \n \n \n\n\n \n Stark, S.; and Väisänen, M.\n\n\n \n\n\n\n Ecosystems, 17(5): 906–917. August 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Insensitivity$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

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@article{stark_insensitivity_2014,\n\ttitle = {Insensitivity of {Soil} {Microbial} {Activity} to {Temporal} {Variation} in {Soil} {N} in {Subarctic} {Tundra}: {Evidence} from {Responses} to {Large} {Migratory} {Grazers}},\n\tvolume = {17},\n\tissn = {1432-9840, 1435-0629},\n\tshorttitle = {Insensitivity of {Soil} {Microbial} {Activity} to {Temporal} {Variation} in {Soil} {N} in {Subarctic} {Tundra}},\n\turl = {https://link.springer.com/article/10.1007/s10021-014-9768-2},\n\tdoi = {10.1007/s10021-014-9768-2},\n\tabstract = {Large migratory grazers commonly influence soil processes in tundra ecosystems. However, the extent to which grazing effects are limited to intensive grazing periods associated with migration has not previously been investigated. We analyzed seasonal patterns in soil nitrogen (N), microbial respiration and extracellular enzyme activities (EEAs) in a lightly grazed tundra and a heavily grazed tundra that has been subjected to intensive grazing during reindeer (Rangifer tarandus L.) migration for the past 50 years. We hypothesized that due to the fertilizing effect of the reindeer, microbial respiration and EEAs related to microbial C acquisition should be higher in heavily grazed areas compared to lightly grazed areas and that the effects of grazing should be strongest during reindeer migration. Reindeer migration caused a dramatic peak in soil N availability, but in contrast to our predictions, the effect of grazing was more or less constant over the growing season and the seasonal patterns of microbial activities and microbial N were strikingly uniform between the lightly and heavily grazed areas. Microbial respiration and the EEAs of β-glucosidase, acid-phosphatase, and leucine-aminopeptidase were higher, whereas that of N-acetylglucosamidase was lower in the heavily grazed area. Experimental fertilization had no effect on EEAs related to C acquisition at either level of grazing intensity. Our findings suggest that soil microbial activities were independent of grazing-induced temporal variation in soil N availability. Instead, the effect of grazing on soil microbial activities appeared to be mediated by substrate availability for soil microorganisms. Following a shift in the dominant vegetation in response to grazing from dwarf shrubs to graminoids, the effect of grazing on soil processes is no longer sensitive to temporal grazing patterns; rather, grazers exert a consistent positive effect on the soil microbial potential for soil C decomposition.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2017-05-27},\n\tjournal = {Ecosystems},\n\tauthor = {Stark, Sari and Väisänen, Maria},\n\tmonth = aug,\n\tyear = {2014},\n\tkeywords = {\\#nosource},\n\tpages = {906--917},\n}\n\n

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\n \n 2013\n \n \n (1)\n \n \n

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\n \n\n \n \n \n \n \n Phenolic Responses of Mountain Crowberry (Empetrum nigrum ssp hermaphroditum) to Global Climate Change are Compound Specific and Depend on Grazing by Reindeer (Rangifer tarandus).\n \n \n \n\n\n \n Väisänen, M.; Martz, F.; Kaarlejärvi, E.; Julkunen-Tiitto, R.; and Stark, S.\n\n\n \n\n\n\n Journal of Chemical Ecology, 39(11-12): 1390–1399. December 2013.\n 00008\n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{vaisanen_phenolic_2013,\n\ttitle = {Phenolic {Responses} of {Mountain} {Crowberry} ({Empetrum} nigrum ssp hermaphroditum) to {Global} {Climate} {Change} are {Compound} {Specific} and {Depend} on {Grazing} by {Reindeer} ({Rangifer} tarandus)},\n\tvolume = {39},\n\tissn = {0098-0331},\n\tdoi = {10.1007/s10886-013-0367-z},\n\tabstract = {Mountain crowberry (Empetrum nigrum ssp. hermaphroditum) is a keystone species in northern ecosystems and exerts important ecosystem-level effects through high concentrations of phenolic metabolites. It has not been investigated how crowberry phenolics will respond to global climate change. In the tundra, grazing by reindeer (Rangifer tarandus) affects vegetation and soil nutrient availability, but almost nothing is known about the interactions between grazing and global climate change on plant phenolics. We performed a factorial warming and fertilization experiment in a tundra ecosystem under light grazing and heavy grazing and analyzed individual foliar phenolics and crowberry abundance. Crowberry was more abundant under light grazing than heavy grazing. Although phenolic concentrations did not differ between grazing intensities, responses of crowberry abundance and phenolic concentrations to warming varied significantly depending on grazing intensity. Under light grazing, warming increased crowberry abundance and the concentration of stilbenes, but decreased e.g., the concentrations of flavonols, condensed tannins, and batatasin-III, resulting in no change in total phenolics. Under heavy grazing, warming did not affect crowberry abundance, and induced a weak but consistent decrease among the different phenolic compound groups, resulting in a net decrease in total phenolics. Our results show that the different phenolic compound groups may show varying or even opposing responses to warming in the tundra at different levels of grazing intensity. Even when plant phenolic concentrations do not directly respond to grazing, grazers may have a key control over plant responses to changes in the abiotic environment, reflecting multiple adaptive purposes of plant phenolics and complex interactions between the biotic and the abiotic factors.},\n\tlanguage = {English},\n\tnumber = {11-12},\n\tjournal = {Journal of Chemical Ecology},\n\tauthor = {Väisänen, Maria and Martz, Francoise and Kaarlejärvi, Elina and Julkunen-Tiitto, Riitta and Stark, Sari},\n\tmonth = dec,\n\tyear = {2013},\n\tnote = {00008},\n\tkeywords = {\\#nosource, Batatasin-III, Plants, Stilbenes, Warming, allocation, arctic tundra, carbon-nutrient balance, dwarf shrubs, fertilization, growth, herbivores, herbivory, tannins, tundra ecosystems, vegetation},\n\tpages = {1390--1399},\n}\n\n

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\n \n undefined\n \n \n (1)\n \n \n

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\n \n\n \n \n \n \n \n \n Controlling biases in targeted plant removal experiments.\n \n \n \n \n\n\n \n Monteux, S.; Blume-Werry, G.; Gavazov, K.; Kirchhoff, L.; Krab, E. J.; Lett, S.; Pedersen, E. P.; and Väisänen, M.\n\n\n \n\n\n\n New Phytologist, n/a(n/a): 19386. .\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.19386\n\n\n\n
\n\n\n\n \n \n $\"Controlling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{monteux_controlling_nodate,\n\ttitle = {Controlling biases in targeted plant removal experiments},\n\tvolume = {n/a},\n\tcopyright = {© 2023 The Authors. New Phytologist © 2023 New Phytologist Foundation},\n\tissn = {1469-8137},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.19386},\n\tdoi = {10.1111/nph.19386},\n\tabstract = {Targeted removal experiments are a powerful tool to assess the effects of plant species or (functional) groups on ecosystem functions. However, removing plant biomass in itself can bias the observed responses. This bias is commonly addressed by waiting until ecosystem recovery, but this is inherently based on unverified proxies or anecdotal evidence. Statistical control methods are efficient, but restricted in scope by underlying assumptions. We propose accounting for such biases within the experimental design, using a gradient of biomass removal controls. We demonstrate the relevance of this design by presenting (1) conceptual examples of suspected biases and (2) how to observe and control for these biases. Using data from a mycorrhizal association-based removal experiment, we show that ignoring biomass removal biases (including by assuming ecosystem recovery) can lead to incorrect, or even contrary conclusions (e.g. false positive and false negative). Our gradient design can prevent such incorrect interpretations, regardless of whether aboveground biomass has fully recovered. Our approach provides more objective and quantitative insights, independently assessed for each variable, than using a proxy to assume ecosystem recovery. Our approach circumvents the strict statistical assumptions of, for example, ANCOVA and thus offers greater flexibility in data analysis.},\n\tlanguage = {en},\n\tnumber = {n/a},\n\turldate = {2024-03-26},\n\tjournal = {New Phytologist},\n\tauthor = {Monteux, Sylvain and Blume-Werry, Gesche and Gavazov, Konstantin and Kirchhoff, Leah and Krab, Eveline J. and Lett, Signe and Pedersen, Emily P. and Väisänen, Maria},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.19386},\n\tkeywords = {Monte Carlo simulations, biomass removal gradient, disturbance bias, ectomycorrhizal plant, ericoid mycorrhizal plant, plant removal experiment, shrubification},\n\tpages = {19386},\n}\n\n

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