@Article{Tarigan2020,
  author    = {Suria Tarigan and Christian Stiegler and Kerstin Wiegand and Alexander Knohl and Kukuh Murtilaksono},
  journal   = {Hydrological Sciences Journal},
  title     = {Relative contribution of evapotranspiration and soil compaction to the fluctuation of catchment discharge: case study from a plantation landscape},
  year      = {2020},
  number    = {0},
  pages     = {1-10},
  volume    = {0},
  abstract  = {Over the last decade, monoculture plantations have rapidly developed in Jambi Province on Sumatra, Indonesia. Meanwhile, there has been intensification of discharge  fluctuation in the study area. We examined the relative contribution of changes in evapotranspiration and soil compaction to the catchment discharge by using the Soil Water Assessment Tool model. Evapotranspiration values based on the catchment water balance analysis in intensively cultivated oil palm plantations, smallholder oil palm plantations, rubber plantations, and the secondary forest are 5.03 ± 0.30, 4.11 ± 0.38, 3.36 ± 0.32, and 4.50 ± 0.18 mm d−1, respectively. Infiltration rate  in active interrows of oil palm, rubber plantations, agroforest, oil palm frond pile is 2.6 ± 1.7, 16.3 ± 6.8, 28.0 ± 3.9, 58.2 ± 21.8 cm h−1, respectively. We found that increased evapotranspiration and soil compaction increased the frequency of low discharge by 30\%, with increased evapotranspiration contributing 10\% and increased soil compaction contributing 20\%.},
  comment   = {public frontpage},
  doi       = {10.1080/02626667.2020.1739287},
  eprint    = {https://doi.org/10.1080/02626667.2020.1739287},
  publisher = {Taylor & Francis},
  url       = {https://doi.org/10.1080/02626667.2020.1739287},
}

Over the last decade, monoculture plantations have rapidly developed in Jambi Province on Sumatra, Indonesia. Meanwhile, there has been intensification of discharge  fluctuation in the study area. We examined the relative contribution of changes in evapotranspiration and soil compaction to the catchment discharge by using the Soil Water Assessment Tool model. Evapotranspiration values based on the catchment water balance analysis in intensively cultivated oil palm plantations, smallholder oil palm plantations, rubber plantations, and the secondary forest are 5.03 ± 0.30, 4.11 ± 0.38, 3.36 ± 0.32, and 4.50 ± 0.18 mm d−1, respectively. Infiltration rate  in active interrows of oil palm, rubber plantations, agroforest, oil palm frond pile is 2.6 ± 1.7, 16.3 ± 6.8, 28.0 ± 3.9, 58.2 ± 21.8 cm h−1, respectively. We found that increased evapotranspiration and soil compaction increased the frequency of low discharge by 30%, with increased evapotranspiration contributing 10% and increased soil compaction contributing 20%.

@Article{Pietzsch2020,
  author   = {Pietzsch, Bruno and Fiedler, Sebastian and Mertens, Kai G. and Richter, Markus and Scherer, C\'{e}dric and Widyastuti, Kirana and Wimmler, Marie-Christin and Zakharova, Liubov and Berger, Uta},
  journal  = {Journal of Artificial Societies and Social Simulation},
  title    = {Metamodels for Evaluating, Calibrating and Applying Agent-Based Models: A Review},
  year     = {2020},
  issn     = {1460-7425},
  number   = {2},
  pages    = {9},
  volume   = {23},
  abstract = {The recent advancement of agent-based modeling is characterized by higher demands on the parameterization, evaluation and documentation of these computationally expensive models. Accordingly, there is also a growing request for "easy to go" applications just mimicking the input-output behavior of such models. Metamodels are being increasingly used for these tasks. In this paper, we provide an overview of common metamodel types and the purposes of their usage in an agent-based modeling context. To guide modelers in the selection and application of metamodels for their own needs, we further assessed their implementation effort and performance. We performed a literature research in January 2019 using four different databases. Five different terms paraphrasing metamodels (approximation, emulator, meta-model, metamodel and surrogate) were used to capture the whole range of relevant literature in all disciplines. All metamodel applications found were then categorized into specific metamodel types and rated by different junior and senior researches from varying disciplines (including forest sciences, landscape ecology, or economics) regarding the implementation effort and performance. Specifically, we captured the metamodel performance according to (i) the consideration of uncertainties, (ii) the suitability assessment provided by the authors for the particular purpose, and (iii) the number of valuation criteria provided for suitability assessment. We selected 40 distinct metamodel applications from studies published in peer-reviewed journals from 2005 to 2019. These were used for the sensitivity analysis, calibration and upscaling of agent-based models, as well to mimic their prediction for different scenarios. This review provides information about the most applicable metamodel types for each purpose and forms a first guidance for the implementation and validation of metamodels for agent-based models.},
  comment  = {public frontpage},
  doi      = {10.18564/jasss.4274},
  keywords = {Individual-Based Model, Surrogate Model, Emulator, Calibration, Sensitivity Analysis, Review},
  url      = {http://jasss.soc.surrey.ac.uk/23/2/9.html},
}

The recent advancement of agent-based modeling is characterized by higher demands on the parameterization, evaluation and documentation of these computationally expensive models. Accordingly, there is also a growing request for "easy to go" applications just mimicking the input-output behavior of such models. Metamodels are being increasingly used for these tasks. In this paper, we provide an overview of common metamodel types and the purposes of their usage in an agent-based modeling context. To guide modelers in the selection and application of metamodels for their own needs, we further assessed their implementation effort and performance. We performed a literature research in January 2019 using four different databases. Five different terms paraphrasing metamodels (approximation, emulator, meta-model, metamodel and surrogate) were used to capture the whole range of relevant literature in all disciplines. All metamodel applications found were then categorized into specific metamodel types and rated by different junior and senior researches from varying disciplines (including forest sciences, landscape ecology, or economics) regarding the implementation effort and performance. Specifically, we captured the metamodel performance according to (i) the consideration of uncertainties, (ii) the suitability assessment provided by the authors for the particular purpose, and (iii) the number of valuation criteria provided for suitability assessment. We selected 40 distinct metamodel applications from studies published in peer-reviewed journals from 2005 to 2019. These were used for the sensitivity analysis, calibration and upscaling of agent-based models, as well to mimic their prediction for different scenarios. This review provides information about the most applicable metamodel types for each purpose and forms a first guidance for the implementation and validation of metamodels for agent-based models.

@Article{Borthwick2020,
  author   = {Borthwick, Richard and de Flamingh, Alida and Hesselbarth, Maximilian H. K. and Parandhaman, Anjana and Wagner, Helene H. and Abdel Moniem, Hossam E. M.},
  journal  = {Frontiers in Genetics},
  title    = {Alternative Quantifications of Landscape Complementation to Model Gene Flow in Banded Longhorn Beetles [Typocerus v. velutinus (Olivier)]},
  year     = {2020},
  issn     = {1664-8021},
  pages    = {307},
  volume   = {11},
  abstract = {Rapid progression of human socio-economic activities has altered the structure and function of natural landscapes. Species that rely on multiple, complementary habitat types (i.e., landscape complementation) to complete their life cycle may be especially at risk. However, such landscape complementation has received little attention in the context of landscape connectivity modeling. A previous study on flower longhorn beetles (Cerambycidae: Lepturinae) integrated landscape complementation into a continuous habitat suitability ‘surface’, which was then used to quantify landscape connectivity between pairs of sampling sites using gradient-surface metrics. This connectivity model was validated with molecular genetic data collected for the banded longhorn beetle (Typocerus v. velutinus) in Indiana, United States. However, this approach has not been compared to alternative models in a landscape genetics context. Here, we used a discrete land use/land cover map to calculate landscape metrics related to landscape complementation based on a patch mosaic model (PMM) as an alternative to the previously published, continuous habitat suitability model (HSM). We evaluated the HSM surface with gradient surface metrics (GSM) and with two resistance-based models (RBM) based on least cost path (LCP) and commute distance (CD), in addition to an isolation-by-distance (IBD) model based on Euclidean distance. We compared the ability of these competing models of connectivity to explain pairwise genetic distances (R<sub>ST</sub>) previously calculated from ten microsatellite genotypes of 454 beetles collected from 17 sites across Indiana, United States. Model selection with maximum likelihood population effects (MLPE) models found that GSM were most effective at explaining pairwise genetic distances as a proxy for gene flow across the landscape, followed by the landscape metrics calculated from the PMM, whereas the LCP model performed worse than both the CD and the isolation by distance model. We argue that the analysis of a continuous HSM with GSM might perform better because of their combined ability to effectively represent and quantify the continuous degree of landscape complementation (i.e., availability of complementary habitats in vicinity) found at and in-between sites, on which these beetles depend. Our findings may inform future studies that seek to model habitat connectivity in complex heterogeneous landscapes as natural habitats continue to become more fragmented in the Anthropocene.},
  comment  = {public frontpage},
  doi      = {10.3389/fgene.2020.00307},
  url      = {https://www.frontiersin.org/article/10.3389/fgene.2020.00307},
}

Rapid progression of human socio-economic activities has altered the structure and function of natural landscapes. Species that rely on multiple, complementary habitat types (i.e., landscape complementation) to complete their life cycle may be especially at risk. However, such landscape complementation has received little attention in the context of landscape connectivity modeling. A previous study on flower longhorn beetles (Cerambycidae: Lepturinae) integrated landscape complementation into a continuous habitat suitability ‘surface’, which was then used to quantify landscape connectivity between pairs of sampling sites using gradient-surface metrics. This connectivity model was validated with molecular genetic data collected for the banded longhorn beetle (Typocerus v. velutinus) in Indiana, United States. However, this approach has not been compared to alternative models in a landscape genetics context. Here, we used a discrete land use/land cover map to calculate landscape metrics related to landscape complementation based on a patch mosaic model (PMM) as an alternative to the previously published, continuous habitat suitability model (HSM). We evaluated the HSM surface with gradient surface metrics (GSM) and with two resistance-based models (RBM) based on least cost path (LCP) and commute distance (CD), in addition to an isolation-by-distance (IBD) model based on Euclidean distance. We compared the ability of these competing models of connectivity to explain pairwise genetic distances (R_ST) previously calculated from ten microsatellite genotypes of 454 beetles collected from 17 sites across Indiana, United States. Model selection with maximum likelihood population effects (MLPE) models found that GSM were most effective at explaining pairwise genetic distances as a proxy for gene flow across the landscape, followed by the landscape metrics calculated from the PMM, whereas the LCP model performed worse than both the CD and the isolation by distance model. We argue that the analysis of a continuous HSM with GSM might perform better because of their combined ability to effectively represent and quantify the continuous degree of landscape complementation (i.e., availability of complementary habitats in vicinity) found at and in-between sites, on which these beetles depend. Our findings may inform future studies that seek to model habitat connectivity in complex heterogeneous landscapes as natural habitats continue to become more fragmented in the Anthropocene.

@Article{Ratzmann2019,
  author   = {Ratzmann, G. and Zakharova, L. and Tietjen, B.},
  title    = {Optimal leaf water status regulation of plants in drylands},
  journal  = {Scientific reports},
  year     = {2019},
  volume   = {9},
  number   = {1},
  pages    = {3768},
  abstract = {Leaf water potential regulation is a key process in whole plant and ecosystem functioning. While low water potentials induced by open stomata may initially be associated with greater CO2 supply and a higher water flux from the rhizosphere to the canopy, they also inhibit cell growth, photosynthesis and ultimately water supply. Here, we show that plants regulate their leaf water potential in an optimal manner under given constraints using a simple leaf water status regulation model and data from a global dryland leaf water potential database. Model predictions agree strongly with observations across locations and species and are further supported by experimental data. Leaf water potentials non-linearly decline with soil water potential, underlining the shift from maximizing water supply to avoiding stress with declining water availability. Our results suggest that optimal regulation of the leaf water status under varying water supply and stress tolerance is a ubiquitous property of plants in drylands. The proposed model moreover provides a novel quantitative framework describing how plants respond to short- and long-term changes in water availability and may help elaborating models of plant and ecosystem functioning.},
  comment  = {public frontpage},
  doi      = {10.1038/s41598-019-40448-2},
  url      = {https://doi.org/10.1038/s41598-019-40448-2},
}

Leaf water potential regulation is a key process in whole plant and ecosystem functioning. While low water potentials induced by open stomata may initially be associated with greater CO2 supply and a higher water flux from the rhizosphere to the canopy, they also inhibit cell growth, photosynthesis and ultimately water supply. Here, we show that plants regulate their leaf water potential in an optimal manner under given constraints using a simple leaf water status regulation model and data from a global dryland leaf water potential database. Model predictions agree strongly with observations across locations and species and are further supported by experimental data. Leaf water potentials non-linearly decline with soil water potential, underlining the shift from maximizing water supply to avoiding stress with declining water availability. Our results suggest that optimal regulation of the leaf water status under varying water supply and stress tolerance is a ubiquitous property of plants in drylands. The proposed model moreover provides a novel quantitative framework describing how plants respond to short- and long-term changes in water availability and may help elaborating models of plant and ecosystem functioning.

@Article{doi:10.1002/ecs2.2620,
  author   = {Getzin, Stephan and Yizhaq, Hezi and Muñoz-Rojas, Miriam and Wiegand, Kerstin and Erickson, Todd E.},
  title    = {A multi-scale study of Australian fairy circles using soil excavations and drone-based image analysis},
  journal  = {Ecosphere},
  year     = {2019},
  volume   = {10},
  number   = {2},
  pages    = {e02620},
  abstract = {Abstract Fairy circles (FCs) are extremely ordered round patches of bare soil within arid grasslands of southwestern Africa and northwestern Australia. Their origin is disputed because biotic factors such as insects or abiotic factors such as edaphic and eco-hydrological feedback mechanisms have been suggested to be causal. In this research, we used a multi-scale approach to shed light on the origin of Australian FCs. At a local scale, we investigated the potential cause of FCs using analyses of soil compaction and texture within FCs, the surrounding matrix vegetation, and in nearby large bare-soil areas. We found that soil hardness and clay content were similarly higher inside the FCs and in the large bare-soil areas. When compared to the matrix soils with protective grass cover, the 2.6–2.8 times higher clay content in FCs and large bare-soil areas is likely sourced via multiple abiotic weathering processes. Intense rainfall events, particle dispersion, surface heat, evaporation, and mechanical crust building inhibit plant growth in both areas. At the landscape scale, a systematic survey of 154 soil excavations within FCs was undertaken to evaluate the presence of pavement termitaria that could inhibit plant growth. We show that in up to 100\% and most of the excavations per plot, no hard pavement termitaria were present in the FCs. This fact is substantiated by the observation that small, newly forming FCs are initiated on soft sand without evidence of termite activity. At the regional scale, we investigated the spatial properties of FCs and common termite-created gaps in Western Australia, using spatially explicit statistics. We mapped three 25-ha FC plots with a drone and compared them with three aerial images of typical vegetation gaps created by harvester and spinifex termites. We demonstrate that the small diameters, the lower ordering, and the heterogeneous patterns of these common termite gaps strongly differ from the unique spatial signature of FCs. Our multi-scale approach emphasizes that FCs are not trivial termite gaps and that partial correlation with termites at some sites does not imply causation. Instead, we highlight the need to study the edaphic and eco-hydrological drivers of vegetation-pattern formation in water-limited environments.},
  comment  = {public frontpage},
  doi      = {10.1002/ecs2.2620},
  eprint   = {https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.2620},
  keywords = {clay crust, cyclone, emergent vegetation patterns, heterogeneity, hydrology, nearest-neighbor distance, pair-correlation function, spatial periodicity, Triodia basedowii, vegetation self-organization, wavelength, weathering},
  url      = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecs2.2620},
}

Abstract Fairy circles (FCs) are extremely ordered round patches of bare soil within arid grasslands of southwestern Africa and northwestern Australia. Their origin is disputed because biotic factors such as insects or abiotic factors such as edaphic and eco-hydrological feedback mechanisms have been suggested to be causal. In this research, we used a multi-scale approach to shed light on the origin of Australian FCs. At a local scale, we investigated the potential cause of FCs using analyses of soil compaction and texture within FCs, the surrounding matrix vegetation, and in nearby large bare-soil areas. We found that soil hardness and clay content were similarly higher inside the FCs and in the large bare-soil areas. When compared to the matrix soils with protective grass cover, the 2.6–2.8 times higher clay content in FCs and large bare-soil areas is likely sourced via multiple abiotic weathering processes. Intense rainfall events, particle dispersion, surface heat, evaporation, and mechanical crust building inhibit plant growth in both areas. At the landscape scale, a systematic survey of 154 soil excavations within FCs was undertaken to evaluate the presence of pavement termitaria that could inhibit plant growth. We show that in up to 100% and most of the excavations per plot, no hard pavement termitaria were present in the FCs. This fact is substantiated by the observation that small, newly forming FCs are initiated on soft sand without evidence of termite activity. At the regional scale, we investigated the spatial properties of FCs and common termite-created gaps in Western Australia, using spatially explicit statistics. We mapped three 25-ha FC plots with a drone and compared them with three aerial images of typical vegetation gaps created by harvester and spinifex termites. We demonstrate that the small diameters, the lower ordering, and the heterogeneous patterns of these common termite gaps strongly differ from the unique spatial signature of FCs. Our multi-scale approach emphasizes that FCs are not trivial termite gaps and that partial correlation with termites at some sites does not imply causation. Instead, we highlight the need to study the edaphic and eco-hydrological drivers of vegetation-pattern formation in water-limited environments.

@Article{GETZIN201985,
  author   = {Stephan Getzin and Hezi Yizhaq},
  title    = {Unusual Namibian fairy circle patterns in heterogeneous and atypical environments},
  journal  = {Journal of Arid Environments},
  year     = {2019},
  volume   = {164},
  pages    = {85 - 89},
  issn     = {0140-1963},
  abstract = {Under homogeneous habitat conditions, fairy circles are extremely ordered grassland gaps that are densely packed and that function as an extra source of water for the surrounding matrix vegetation. While the origin of fairy circles is still disputed, most of the research has so far focused on such typical habitat conditions where the fairy circles are almost round and have a grid-like hexagonal pattern. However, Namibian fairy circles also occur under atypical habitat conditions where topographical heterogeneity or extreme aridity are forcing the circles to change their shapes and patterns. In this pilot study, we are describing some striking and new examples how shapes and patterns of fairy circles may change under such atypical environmental conditions. We emphasize the need to study fairy circles in disturbed catchment areas, mega circles in drainage lines, as well as soil-water budgets of irregularly spaced fairy circles in very arid locations. Furthermore, there is need to understand the formation of the very large mega circles and desertification fronts in flat habitat. Finally, we also discuss the potential role of abiotic drivers such as soil-crust formation in the vegetation matrix or aeolian erosion and subsequent de-rooting of grasses in forming unusual fairy circle shapes, sizes and patterns.},
  comment  = {public frontpage},
  doi      = {https://doi.org/10.1016/j.jaridenv.2019.01.017},
  keywords = {Desertification front, Eco-hydrology, Fairy circles, Heterogeneity, Soil crust, Wind erosion},
  url      = {http://www.sciencedirect.com/science/article/pii/S0140196318309820},
}

Under homogeneous habitat conditions, fairy circles are extremely ordered grassland gaps that are densely packed and that function as an extra source of water for the surrounding matrix vegetation. While the origin of fairy circles is still disputed, most of the research has so far focused on such typical habitat conditions where the fairy circles are almost round and have a grid-like hexagonal pattern. However, Namibian fairy circles also occur under atypical habitat conditions where topographical heterogeneity or extreme aridity are forcing the circles to change their shapes and patterns. In this pilot study, we are describing some striking and new examples how shapes and patterns of fairy circles may change under such atypical environmental conditions. We emphasize the need to study fairy circles in disturbed catchment areas, mega circles in drainage lines, as well as soil-water budgets of irregularly spaced fairy circles in very arid locations. Furthermore, there is need to understand the formation of the very large mega circles and desertification fronts in flat habitat. Finally, we also discuss the potential role of abiotic drivers such as soil-crust formation in the vegetation matrix or aeolian erosion and subsequent de-rooting of grasses in forming unusual fairy circle shapes, sizes and patterns.

@Article{Siebert2019,
  author   = {Siebert, Frances and Dreber, Niels},
  title    = {Forb ecology research in dry African savannas: Knowledge, gaps, and future perspectives},
  journal  = {Ecology and Evolution},
  year     = {2019},
  volume   = {9},
  number   = {13},
  pages    = {7875-7891},
  abstract = {Abstract Savannas are commonly described as a vegetation type with a grass layer interspersed with a discontinuous tree or shrub layer. On the contrary, forbs, a plant life form that can include any nongraminoid herbaceous vascular plant, are poorly represented in definitions of savannas worldwide. While forbs have been acknowledged as a diverse component of the herbaceous layer in savanna ecosystems and valued for the ecosystem services and functions they provide, they have not been the primary focus in most savanna vegetation studies. We performed a systematic review of scientific literature to establish the extent to which forbs are implicitly or explicitly considered as a discrete vegetation component in savanna research. The overall aims were to summarize knowledge on forb ecology, identify knowledge gaps, and derive new perspectives for savanna research and management with a special focus on arid and semiarid ecosystems in Africa. We synthesize and discuss our findings in the context of different overarching research themes: (a) functional organization and spatial patterning, (b) land degradation and range management, (c) conservation and reserve management, (d) resource use and forage patterning, and (e) germination and recruitment. Our results revealed biases in published research with respect to study origin (country coverage in Africa), climate (more semiarid than arid systems), spatial scale (more local than landscape scale), the level at which responses or resource potential was analyzed (primarily plant functional groups rather than species), and the focus on interactions between life forms (rather seldom between forbs and grasses and/or trees). We conclude that the understanding of African savanna community responses to drivers of global environmental change requires knowledge beyond interactions between trees and grasses only and beyond the plant functional group level. Despite multifaceted evidence of our current understanding of forbs in dry savannas, there appear to be knowledge gaps, specifically in linking drivers of environmental change to forb community responses. We therefore propose that more attention be given to forbs as an additional ecologically important plant life form in the conventional tree–grass paradigm of savannas.},
  comment  = {public frontpage},
  doi      = {10.1002/ece3.5307},
  eprint   = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.5307},
  keywords = {biodiversity, biomass, disturbance, forage, herbaceous community, indicator, semi-arid},
  url      = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ece3.5307},
}

Abstract Savannas are commonly described as a vegetation type with a grass layer interspersed with a discontinuous tree or shrub layer. On the contrary, forbs, a plant life form that can include any nongraminoid herbaceous vascular plant, are poorly represented in definitions of savannas worldwide. While forbs have been acknowledged as a diverse component of the herbaceous layer in savanna ecosystems and valued for the ecosystem services and functions they provide, they have not been the primary focus in most savanna vegetation studies. We performed a systematic review of scientific literature to establish the extent to which forbs are implicitly or explicitly considered as a discrete vegetation component in savanna research. The overall aims were to summarize knowledge on forb ecology, identify knowledge gaps, and derive new perspectives for savanna research and management with a special focus on arid and semiarid ecosystems in Africa. We synthesize and discuss our findings in the context of different overarching research themes: (a) functional organization and spatial patterning, (b) land degradation and range management, (c) conservation and reserve management, (d) resource use and forage patterning, and (e) germination and recruitment. Our results revealed biases in published research with respect to study origin (country coverage in Africa), climate (more semiarid than arid systems), spatial scale (more local than landscape scale), the level at which responses or resource potential was analyzed (primarily plant functional groups rather than species), and the focus on interactions between life forms (rather seldom between forbs and grasses and/or trees). We conclude that the understanding of African savanna community responses to drivers of global environmental change requires knowledge beyond interactions between trees and grasses only and beyond the plant functional group level. Despite multifaceted evidence of our current understanding of forbs in dry savannas, there appear to be knowledge gaps, specifically in linking drivers of environmental change to forb community responses. We therefore propose that more attention be given to forbs as an additional ecologically important plant life form in the conventional tree–grass paradigm of savannas.

@Article{Harmse2019,
  author    = {Christiaan J Harmse and Niels Dreber and Winston SW Trollope},
  journal   = {African Journal of Range \& Forage Science},
  title     = {Disc pasture meter calibration to estimate grass biomass production in the arid dunefield of the south-western Kalahari},
  year      = {2019},
  abstract  = {The disc pasture meter (DPM) is a tool that is widely used to estimate aboveground standing grass biomass (ASB) in a rapid and non-destructive manner. Depending on the species composition, rangeland condition and local climate, available DPM calibrations may fail in providing precise measurements for a certain area. We calibrated a DPM for the arid dunefield savanna of the south-western Kalahari as found in the Northern Cape province of South Africa and bordering Namibia and Botswana. Assessments were done at 30 sites and restricted to inter-dune areas. The site selection accounted for different grazing conditions to ensure a better representation of the variability in ASB in the region. We determined grass species composition, basal cover and dry matter production in relation to height readings of the DPM. The grass sward was dominated by the species Stipagrostis ciliata, S. obtusa and Schmidtia kalahariensis, with a mean density of 25 cm point-to-tuft distances. Based on 90 paired observations of ASB and disc height (x; cm), the equation ӯ (kg ha−1) = 213.37(x) + 103.36 (r2 = 0.760) was established. In comparison to other models, the equation avoids an overestimation of ASB in this vegetation type, and thus leads to more accurate estimations.},
  comment   = {public frontpage},
  doi       = {10.2989/10220119.2019.1610905},
  eprint    = {https://doi.org/10.2989/10220119.2019.1610905},
  publisher = {Taylor \& Francis},
  url       = {https://doi.org/10.2989/10220119.2019.1610905},
}

The disc pasture meter (DPM) is a tool that is widely used to estimate aboveground standing grass biomass (ASB) in a rapid and non-destructive manner. Depending on the species composition, rangeland condition and local climate, available DPM calibrations may fail in providing precise measurements for a certain area. We calibrated a DPM for the arid dunefield savanna of the south-western Kalahari as found in the Northern Cape province of South Africa and bordering Namibia and Botswana. Assessments were done at 30 sites and restricted to inter-dune areas. The site selection accounted for different grazing conditions to ensure a better representation of the variability in ASB in the region. We determined grass species composition, basal cover and dry matter production in relation to height readings of the DPM. The grass sward was dominated by the species Stipagrostis ciliata, S. obtusa and Schmidtia kalahariensis, with a mean density of 25 cm point-to-tuft distances. Based on 90 paired observations of ASB and disc height (x; cm), the equation ӯ (kg ha−1) = 213.37(x) + 103.36 (r2 = 0.760) was established. In comparison to other models, the equation avoids an overestimation of ASB in this vegetation type, and thus leads to more accurate estimations.

@Article{Salecker2019,
  author   = {Salecker, Jan and Dislich, Claudia and Wiegand, Kerstin, and Meyer, Katrin M. and Pe´er, Guy},
  title    = {EFForTS-LGraf: A Landscape Generator for Creating Smallholder-Driven Land-Use Mosaics},
  journal  = {EFForTS Discussion Paper Series},
  year     = {2019},
  volume   = {29},
  url_pdf  = {http://webdoc.sub.gwdg.de/pub/mon/sfb990/dp-29.pdf},
  abstract = {Spatially-explicit  simulation  models  are  commonly  used  to  study  complex  ecological and  socio-economic  research  questions.  Often  these  models  depend  on  detailed  input  data,such  as initial land-cover maps to set up model simulations. Here we present the landscape generator EFFortS-LGraf  that  provides  artificially-generated  land-use  maps  of  agricultural  landscapes  shaped  by  small-scale  farms.  EFForTS-LGraf  is  a  process-based landscape  generator  that  explicitly  incorporates  the human  dimension  of  land-use  change.  The  model  generates  roads  and  villages  that  consist  of smallholder  farming  households.  These  smallholders  use  different  establishment  strategies  to  create fields  in  their  close  vicinity.  Crop  types  are  distributed  to  these  fields  based  on  crop  fractions  and specialization  levels. EFForTS-LGraf  model  parameters  such  as  household  area  or  field size frequency distributions can be derived from household surveys or geospatial data. This can be an advantage over the  abstract  parameters  of  neutral  landscape  generators.  We  tested  the  model  using  oil  palm  and rubber  farming  in  Indonesia  as  a  case  study  and  validated  the  artificially-generated  maps  against classified satellite images. Our results show that EFForTS-LGraf is able to generate realistic land-cover maps with properties that lie within the boundaries of landscapes from classified satellite images. An applied  simulation  experiment  on  landscape-level  effects  of  increasing household  area  and  crop specialization  revealed  that  larger  households  with  higher  specialization  levels  led  to  spatially  more homogeneous  and  less  scattered  crop  type  distributions  and  reduced  edge  area  proportion.  Thus, EFForTS-LGraf  can  be  applied  both to  generate  maps  as  inputs  for  simulation  modelling  and  as  a stand-alone tool for specific landscape-scale analyses in the context of ecological-economic studies of smallholder farming systems.},
  comment  = {public},
  keywords = {landscape generator; agent-based model; ABM; NetLogo; process-based; Indonesia},
  url      = {http://webdoc.sub.gwdg.de/pub/mon/sfb990/dp-29.pdf},
}

Spatially-explicit simulation models are commonly used to study complex ecological and socio-economic research questions. Often these models depend on detailed input data,such as initial land-cover maps to set up model simulations. Here we present the landscape generator EFFortS-LGraf that provides artificially-generated land-use maps of agricultural landscapes shaped by small-scale farms. EFForTS-LGraf is a process-based landscape generator that explicitly incorporates the human dimension of land-use change. The model generates roads and villages that consist of smallholder farming households. These smallholders use different establishment strategies to create fields in their close vicinity. Crop types are distributed to these fields based on crop fractions and specialization levels. EFForTS-LGraf model parameters such as household area or field size frequency distributions can be derived from household surveys or geospatial data. This can be an advantage over the abstract parameters of neutral landscape generators. We tested the model using oil palm and rubber farming in Indonesia as a case study and validated the artificially-generated maps against classified satellite images. Our results show that EFForTS-LGraf is able to generate realistic land-cover maps with properties that lie within the boundaries of landscapes from classified satellite images. An applied simulation experiment on landscape-level effects of increasing household area and crop specialization revealed that larger households with higher specialization levels led to spatially more homogeneous and less scattered crop type distributions and reduced edge area proportion. Thus, EFForTS-LGraf can be applied both to generate maps as inputs for simulation modelling and as a stand-alone tool for specific landscape-scale analyses in the context of ecological-economic studies of smallholder farming systems.

@Article{ZAKHAROVA2019108703,
  author   = {L. Zakharova and K.M. Meyer and M. Seifan},
  title    = {Trait-based modelling in ecology: A review of two decades of research},
  journal  = {Ecological Modelling},
  year     = {2019},
  volume   = {407},
  pages    = {108703},
  issn     = {0304-3800},
  abstract = {Trait-based approaches are an alternative to species-based approaches for functionally linking individual organisms with community structure and dynamics. In the trait-based approach, rather than focusing on the species identity of the organism, the focus is on the organism traits, which represent their physiological, morphological, or life-history characteristics. Although used in ecological research for several decades, this approach only emerged in ecological modelling about twenty years ago. We review this rise of trait-based models and trace the occasional transfer of trait-based modelling concepts between terrestrial plant ecology, animal and microbial ecology, and aquatic ecology, discuss terminology of trait-based approaches and evaluate future implementation of trait-based models, including cross-discipline exchange. Trait-based models have a variety of purposes, such as predicting changes in community patterns under climate and land-use change, understand underlying mechanisms for community assemblies, planning and assessing conservation management, or studying invasion processes. In modelling, trait-based approaches can reduce technical challenges such as computational limitations, scaling problems, and data scarcity. However, we note inconsistencies in the current usage of terms in trait-based approaches and these inconsistencies must be resolved if trait-based concepts are to be easily exchanged between disciplines. Specifically, future trait-based models may further benefit from incorporating intraspecific trait variability and addressing more complex species interactions. We also recommend expanding the combination of trait-based approaches with individual-based modelling to simplify the parameterization of models, to capture plant-plant interactions at the individual level, and to explain community dynamics under global change.},
  comment  = {public frontpage},
  doi      = {10.1016/j.ecolmodel.2019.05.008},
  keywords = {Functional traits, Functional types, Model types, Trait-based approach, Trait-based model, Individual-based modelling},
  url      = {http://www.sciencedirect.com/science/article/pii/S0304380019301735},
}

Trait-based approaches are an alternative to species-based approaches for functionally linking individual organisms with community structure and dynamics. In the trait-based approach, rather than focusing on the species identity of the organism, the focus is on the organism traits, which represent their physiological, morphological, or life-history characteristics. Although used in ecological research for several decades, this approach only emerged in ecological modelling about twenty years ago. We review this rise of trait-based models and trace the occasional transfer of trait-based modelling concepts between terrestrial plant ecology, animal and microbial ecology, and aquatic ecology, discuss terminology of trait-based approaches and evaluate future implementation of trait-based models, including cross-discipline exchange. Trait-based models have a variety of purposes, such as predicting changes in community patterns under climate and land-use change, understand underlying mechanisms for community assemblies, planning and assessing conservation management, or studying invasion processes. In modelling, trait-based approaches can reduce technical challenges such as computational limitations, scaling problems, and data scarcity. However, we note inconsistencies in the current usage of terms in trait-based approaches and these inconsistencies must be resolved if trait-based concepts are to be easily exchanged between disciplines. Specifically, future trait-based models may further benefit from incorporating intraspecific trait variability and addressing more complex species interactions. We also recommend expanding the combination of trait-based approaches with individual-based modelling to simplify the parameterization of models, to capture plant-plant interactions at the individual level, and to explain community dynamics under global change.

@Article{Salecker2019a,
  author   = {Salecker, Jan and Sciaini, Marco and Meyer, Katrin M. and Wiegand, Kerstin},
  title    = {The nlrx R package: A next-generation framework for reproducible NetLogo model analyses},
  journal  = {Methods in Ecology and Evolution},
  year     = {2019},
  volume   = {10},
  pages    = {1854--1863},
  abstract = {1.Agent-based models find wide application in all fields of science where large scale patterns emerge from properties of individuals. Due to increasing capacities of computing resources it was possible to improve the level of detail and structural realism of next-generation models in recent years. However, this is at the expense of increased model complexity, which requires more efficient tools for model exploration, analysis and documentation that enable reproducibility, repeatability and parallelisation. NetLogo is a widely used environment for agent-based model development, but it does not provide sufficient built-in tools for extensive model exploration, such as sensitivity analyses. One tool for controlling NetLogo externally is the R-package RNetLogo. However, this package is not suited for efficient, reproducible research as it has stability and resource allocation issues, is not straightforward to be setup and used on high performance computing clusters and does not provide utilities, such as storing and exchanging metadata, in an easy way. 2.We present the R-package nlrx, which overcomes stability and resource allocation issues by running NetLogo simulations via dynamically created XML experiment files. Class objects make setting up experiments more convenient and helper functions provide many parameter exploration approaches, such as Latin Hypercube designs, Sobol sensitivity analyses or optimization approaches. Output is automatically collected in user-friendly formats and can be post-processed with provided utility functions. nlrx enables reproducibility by storing all relevant information and simulation output of experiments in one R object which can conveniently be archived and shared. 3.We provide a detailed description of the nlrx package functions and the overall workflow. We also present a use case scenario using a NetLogo model, for which we performed a sensitivity analysis and a genetic algorithm optimization. 4.The nlrx package is the first framework for documentation and application of reproducible NetLogo simulation model analysis. This article is protected by copyright. All rights reserved.},
  comment  = {public frontpage},
  doi      = {10.1111/2041-210X.13286},
  eprint   = {https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13286},
  keywords = {agent-based modelling, individual-based modelling, reproducible workflow, R package, NetLogo},
  url      = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13286},
}

1.Agent-based models find wide application in all fields of science where large scale patterns emerge from properties of individuals. Due to increasing capacities of computing resources it was possible to improve the level of detail and structural realism of next-generation models in recent years. However, this is at the expense of increased model complexity, which requires more efficient tools for model exploration, analysis and documentation that enable reproducibility, repeatability and parallelisation. NetLogo is a widely used environment for agent-based model development, but it does not provide sufficient built-in tools for extensive model exploration, such as sensitivity analyses. One tool for controlling NetLogo externally is the R-package RNetLogo. However, this package is not suited for efficient, reproducible research as it has stability and resource allocation issues, is not straightforward to be setup and used on high performance computing clusters and does not provide utilities, such as storing and exchanging metadata, in an easy way. 2.We present the R-package nlrx, which overcomes stability and resource allocation issues by running NetLogo simulations via dynamically created XML experiment files. Class objects make setting up experiments more convenient and helper functions provide many parameter exploration approaches, such as Latin Hypercube designs, Sobol sensitivity analyses or optimization approaches. Output is automatically collected in user-friendly formats and can be post-processed with provided utility functions. nlrx enables reproducibility by storing all relevant information and simulation output of experiments in one R object which can conveniently be archived and shared. 3.We provide a detailed description of the nlrx package functions and the overall workflow. We also present a use case scenario using a NetLogo model, for which we performed a sensitivity analysis and a genetic algorithm optimization. 4.The nlrx package is the first framework for documentation and application of reproducible NetLogo simulation model analysis. This article is protected by copyright. All rights reserved.

@Article{Dreber2019,
  author   = {N. Dreber and S.E. van Rooyen and K. Kellner},
  title    = {One savanna, many shapes: How bush control affects the woody layer in the southern Kalahari},
  journal  = {South African Journal of Botany},
  year     = {2019},
  volume   = {125},
  pages    = {511 - 520},
  issn     = {0254-6299},
  abstract = {Bush thickening (shrub encroachment) is a major ecological and economic threat in southern African savannas. Different types and intensities of bush control (BC) are applied to counteract and mitigate bush thickening. However, woody vegetation response to BC and possible ecological side effects can be manifold. Land users therefore require solid knowledge about the associated structural and compositional changes, helping to apply an informed BC strategy that preserves multiple ecosystem services and functions. The present study addresses this need in a South African thornbush-type savanna. We sampled 41 rangeland sites with a known history of BC in comparison to benchmark conditions. The BC treatments included a selective and non-selective arboricide application and a selective stem burning. We identified each woody species in belt transects and measured the size and canopy of all individuals. The data were used to calculate measures of diversity, cover and density and to describe the population structure of key species. Marked differences in woody species composition and abundance patterns as well as significant alterations of the horizontal and vertical woody vegetation structure clearly reflected the intensity and level of selectivity with which BC had been conducted. While population trends displayed regeneration of key species, important structural elements (large mature trees) were often at risk of being lost from the savanna ecosystem. Results suggest varying degrees of ecosystem functional integrity following the BC treatments. It is concluded that selective BC treatments should be preferred as they allow to create open and well-structured savannas in benefit of the stability and biodiversity of the system. Yet, for improved predictions further research is needed into species-specific population dynamics and trait-related plant–plant interactions. In addition, there is still uncertainty about possible long-term ecological effects associated with the use of arboricides in this type of savanna, which should receive special attention in future research.},
  comment  = {public frontpage},
  doi      = {https://doi.org/10.1016/j.sajb.2019.08.026},
  keywords = {Arboricide, Biodiversity, Diversity profile, Height-class distribution, Savanna, Shrub encroachment, Species composition, Sustainable land management, Vegetation structure, Woody vegetation},
  url      = {http://www.sciencedirect.com/science/article/pii/S0254629919308968},
}

Bush thickening (shrub encroachment) is a major ecological and economic threat in southern African savannas. Different types and intensities of bush control (BC) are applied to counteract and mitigate bush thickening. However, woody vegetation response to BC and possible ecological side effects can be manifold. Land users therefore require solid knowledge about the associated structural and compositional changes, helping to apply an informed BC strategy that preserves multiple ecosystem services and functions. The present study addresses this need in a South African thornbush-type savanna. We sampled 41 rangeland sites with a known history of BC in comparison to benchmark conditions. The BC treatments included a selective and non-selective arboricide application and a selective stem burning. We identified each woody species in belt transects and measured the size and canopy of all individuals. The data were used to calculate measures of diversity, cover and density and to describe the population structure of key species. Marked differences in woody species composition and abundance patterns as well as significant alterations of the horizontal and vertical woody vegetation structure clearly reflected the intensity and level of selectivity with which BC had been conducted. While population trends displayed regeneration of key species, important structural elements (large mature trees) were often at risk of being lost from the savanna ecosystem. Results suggest varying degrees of ecosystem functional integrity following the BC treatments. It is concluded that selective BC treatments should be preferred as they allow to create open and well-structured savannas in benefit of the stability and biodiversity of the system. Yet, for improved predictions further research is needed into species-specific population dynamics and trait-related plant–plant interactions. In addition, there is still uncertainty about possible long-term ecological effects associated with the use of arboricides in this type of savanna, which should receive special attention in future research.

@Article{Salecker2019b,
  author    = {Salecker, Jan and Dislich, Claudia and Wiegand, Kerstin and Meyer, Katrin M. and Pe´er, Guy},
  title     = {EFForTS-LGraf: A landscape generator for creating smallholder-driven land-use mosaics},
  journal   = {PLOS ONE},
  year      = {2019},
  volume    = {14},
  number    = {9},
  pages     = {1-24},
  month     = {09},
  abstract  = {Spatially-explicit simulation models are commonly used to study complex ecological and socio-economic research questions. Often these models depend on detailed input data, such as initial land-cover maps to set up model simulations. Here we present the landscape generator EFFortS-LGraf that provides artificially-generated land-use maps of agricultural landscapes shaped by small-scale farms. EFForTS-LGraf is a process-based landscape generator that explicitly incorporates the human dimension of land-use change. The model generates roads and villages that consist of smallholder farming households. These smallholders use different establishment strategies to create fields in their close vicinity. Crop types are distributed to these fields based on crop fractions and specialization levels. EFForTS-LGraf model parameters such as household area or field size frequency distributions can be derived from household surveys or geospatial data. This can be an advantage over the abstract parameters of neutral landscape generators. We tested the model using oil palm and rubber farming in Indonesia as a case study and validated the artificially-generated maps against classified satellite images. Our results show that EFForTS-LGraf is able to generate realistic land-cover maps with properties that lie within the boundaries of landscapes from classified satellite images. An applied simulation experiment on landscape-level effects of increasing household area and crop specialization revealed that larger households with higher specialization levels led to spatially more homogeneous and less scattered crop type distributions and reduced edge area proportion. Thus, EFForTS-LGraf can be applied both to generate maps as inputs for simulation modelling and as a stand-alone tool for specific landscape-scale analyses in the context of ecological-economic studies of smallholder farming systems.},
  comment   = {public frontpage},
  doi       = {10.1371/journal.pone.0222949},
  publisher = {Public Library of Science},
  url       = {https://doi.org/10.1371/journal.pone.0222949},
}

Spatially-explicit simulation models are commonly used to study complex ecological and socio-economic research questions. Often these models depend on detailed input data, such as initial land-cover maps to set up model simulations. Here we present the landscape generator EFFortS-LGraf that provides artificially-generated land-use maps of agricultural landscapes shaped by small-scale farms. EFForTS-LGraf is a process-based landscape generator that explicitly incorporates the human dimension of land-use change. The model generates roads and villages that consist of smallholder farming households. These smallholders use different establishment strategies to create fields in their close vicinity. Crop types are distributed to these fields based on crop fractions and specialization levels. EFForTS-LGraf model parameters such as household area or field size frequency distributions can be derived from household surveys or geospatial data. This can be an advantage over the abstract parameters of neutral landscape generators. We tested the model using oil palm and rubber farming in Indonesia as a case study and validated the artificially-generated maps against classified satellite images. Our results show that EFForTS-LGraf is able to generate realistic land-cover maps with properties that lie within the boundaries of landscapes from classified satellite images. An applied simulation experiment on landscape-level effects of increasing household area and crop specialization revealed that larger households with higher specialization levels led to spatially more homogeneous and less scattered crop type distributions and reduced edge area proportion. Thus, EFForTS-LGraf can be applied both to generate maps as inputs for simulation modelling and as a stand-alone tool for specific landscape-scale analyses in the context of ecological-economic studies of smallholder farming systems.

@Article{Hesselbarth2019,
  author   = {Hesselbarth, Maximilian H. K. and Sciaini, Marco and With, Kimberly A. and Wiegand, Kerstin and Nowosad, Jakub},
  title    = {landscapemetrics: an open-source R tool to calculate landscape metrics},
  journal  = {Ecography},
  year     = {2019},
  volume   = {42},
  number   = {10},
  pages    = {1648-1657},
  abstract = {Quantifying landscape characteristics and linking them to ecological processes is one of the central goals of landscape ecology. Landscape metrics are a widely used tool for the analysis of patch-based, discrete land-cover classes. Existing software to calculate landscape metrics has several constraints, such as being limited to a single platform, not being open-source or involving a complicated integration into large workflows. We present landscapemetrics, an open-source R package that overcomes many constraints of existing landscape metric software. The package includes an extensive collection of commonly used landscape metrics in a tidy workflow. To facilitate the integration into large workflows, landscapemetrics is based on a well-established spatial framework in R. This allows pre-processing of land-cover maps or further statistical analysis without importing and exporting the data from and to different software environments. Additionally, the package provides many utility functions to visualize, extract, and sample landscape metrics. Lastly, we provide building-blocks to motivate the development and integration of new metrics in the future. We demonstrate the usage and advantages of landscapemetrics by analysing the influence of different sampling schemes on the estimation of landscape metrics. In so doing, we demonstrate the many advantages of the package, especially its easy integration into large workflows. These new developments should help with the integration of landscape analysis in ecological research, given that ecologists are increasingly using R for the statistical analysis, modelling and visualization of spatial data.},
  comment  = {public frontpage},
  doi      = {10.1111/ecog.04617},
  eprint   = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/ecog.04617},
  keywords = {landscape analysis, landscape indices, landscape mosaic model, open-source software, R software, sampling design},
  url      = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ecog.04617},
}

Quantifying landscape characteristics and linking them to ecological processes is one of the central goals of landscape ecology. Landscape metrics are a widely used tool for the analysis of patch-based, discrete land-cover classes. Existing software to calculate landscape metrics has several constraints, such as being limited to a single platform, not being open-source or involving a complicated integration into large workflows. We present landscapemetrics, an open-source R package that overcomes many constraints of existing landscape metric software. The package includes an extensive collection of commonly used landscape metrics in a tidy workflow. To facilitate the integration into large workflows, landscapemetrics is based on a well-established spatial framework in R. This allows pre-processing of land-cover maps or further statistical analysis without importing and exporting the data from and to different software environments. Additionally, the package provides many utility functions to visualize, extract, and sample landscape metrics. Lastly, we provide building-blocks to motivate the development and integration of new metrics in the future. We demonstrate the usage and advantages of landscapemetrics by analysing the influence of different sampling schemes on the estimation of landscape metrics. In so doing, we demonstrate the many advantages of the package, especially its easy integration into large workflows. These new developments should help with the integration of landscape analysis in ecological research, given that ecologists are increasingly using R for the statistical analysis, modelling and visualization of spatial data.

@Article{Paul2019,
  author   = {Paul, Carola and Reith, Esther and Salecker, Jan and Knoke, Thomas},
  journal  = {Current Landscape Ecology Reports},
  title    = {How Integrated Ecological-Economic Modelling Can Inform Landscape Pattern in Forest Agroecosystems},
  year     = {2019},
  issn     = {2364-494X},
  month    = {Nov},
  number   = {4},
  pages    = {125--138},
  volume   = {4},
  abstract = {The purpose of this review is to analyse recent advances in ecological-economic modelling designed to inform desirable landscape composition and configuration. We explore how models capture the economic and ecological consequences of landscape pattern, and potential feedbacks to the responses by policy or landholders.
Modelling approaches are becoming increasingly interlinked, coupling components of empirical-statistical modelling, spatial and bioeconomic simulation, land-use optimization and agent-based models. We analyse recent methodological advances and find that only few examples capture feedbacks between landscape pattern and decision-making.
We outline how future hybrid models could build on these recent advances by inter alia an improved representation of landscape patterns, refining the theory behind decision-making, incorporating uncertainty and reducing model complexity. We conclude that coupling recent developments in land-use optimization and agent-based models may help bridge gaps between modelling philosophies as well as parsimony vs. complexity. This fruitful field of research could help to improve understanding on the role of landscape pattern in social-ecological systems.},
  comment  = {public frontpage},
  day      = {08},
  doi      = {10.1007/s40823-019-00046-4},
  keywords = {Bioeconomic modelling Social-economic models Portfolio analysis Landscape metrics Ecosystem services Trade-offs},
  url      = {https://doi.org/10.1007/s40823-019-00046-4},
}

The purpose of this review is to analyse recent advances in ecological-economic modelling designed to inform desirable landscape composition and configuration. We explore how models capture the economic and ecological consequences of landscape pattern, and potential feedbacks to the responses by policy or landholders. Modelling approaches are becoming increasingly interlinked, coupling components of empirical-statistical modelling, spatial and bioeconomic simulation, land-use optimization and agent-based models. We analyse recent methodological advances and find that only few examples capture feedbacks between landscape pattern and decision-making. We outline how future hybrid models could build on these recent advances by inter alia an improved representation of landscape patterns, refining the theory behind decision-making, incorporating uncertainty and reducing model complexity. We conclude that coupling recent developments in land-use optimization and agent-based models may help bridge gaps between modelling philosophies as well as parsimony vs. complexity. This fruitful field of research could help to improve understanding on the role of landscape pattern in social-ecological systems.

@Article{Getzin2019,
  author   = {Getzin, Stephan and Yizhaq, Hezi and Cramer, Michael D. and Tschinkel, Walter R.},
  title    = {Contrasting Global Patterns of Spatially Periodic Fairy Circles and Regular Insect Nests in Drylands},
  journal  = {Journal of Geophysical Research: Biogeosciences},
  year     = {2019},
  volume   = {n/a},
  number   = {n/a},
  abstract = {Abstract Numerical analysis of spatial pattern is widely used in ecology to describe the characteristics of floral and faunal distributions. These methods allow attribution of pattern to causal mechanisms by uncovering the specific signatures of patterns and causal agents. For example, grassland-gap patterns called fairy circles (FCs) in Namibia and Australia are characterized by highly regular and homogenous distributions across landscapes that show spatially periodic ordering. These FCs have been suggested to be caused by both social insects and competitive plant interactions. We compared eight Namibian and Australian FC patterns and also modeled FCs to 16 patterns of social insect nests in Africa, Australia, and America that include the most regular termite mound patterns known. For pattern-process inference, we used spatial statistics based on both nearest-neighbor analysis and neighborhood-density functions. None of the analyzed insect-nest distributions attain the spatially periodic ordering that is typical of FCs. The inherently more variable patterns of termite and ant nests are commonly attributable to well documented aspects of the faunal life-history. Our quantitative evidence from drylands shows that the more variable insect-nest distributions in water-limited environments cannot explain the characteristic spatial signature of FCs. The analysis demonstrates the interpretation of scale-dependent neighborhood-density functions and that it is the identification of unique spatial signatures in regular patterns that need to be linked to process. While our results cannot verify a specific hypothesis, they support the hypothesis that FCs in these drylands are more likely an emergent vegetation pattern caused by strong plant competition for water.},
  comment  = {public frontpage},
  doi      = {10.1029/2019JG005393},
  eprint   = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JG005393},
  url      = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005393},
}

Abstract Numerical analysis of spatial pattern is widely used in ecology to describe the characteristics of floral and faunal distributions. These methods allow attribution of pattern to causal mechanisms by uncovering the specific signatures of patterns and causal agents. For example, grassland-gap patterns called fairy circles (FCs) in Namibia and Australia are characterized by highly regular and homogenous distributions across landscapes that show spatially periodic ordering. These FCs have been suggested to be caused by both social insects and competitive plant interactions. We compared eight Namibian and Australian FC patterns and also modeled FCs to 16 patterns of social insect nests in Africa, Australia, and America that include the most regular termite mound patterns known. For pattern-process inference, we used spatial statistics based on both nearest-neighbor analysis and neighborhood-density functions. None of the analyzed insect-nest distributions attain the spatially periodic ordering that is typical of FCs. The inherently more variable patterns of termite and ant nests are commonly attributable to well documented aspects of the faunal life-history. Our quantitative evidence from drylands shows that the more variable insect-nest distributions in water-limited environments cannot explain the characteristic spatial signature of FCs. The analysis demonstrates the interpretation of scale-dependent neighborhood-density functions and that it is the identification of unique spatial signatures in regular patterns that need to be linked to process. While our results cannot verify a specific hypothesis, they support the hypothesis that FCs in these drylands are more likely an emergent vegetation pattern caused by strong plant competition for water.

@Article{Fischer2019,
  author  = {Fischer, Christoph and Saborowski, Joachim},
  journal = {Canadian Journal of Forest Research},
  title   = {Estimating volume growth from successive double sampling for stratification},
  year    = {2019},
  number  = {9},
  pages   = {1052-1059},
  volume  = {49},
  comment = {public frontpage},
  doi     = {10.1139/cjfr-2018-0520},
  eprint  = {https://doi.org/10.1139/cjfr-2018-0520},
  url     = {https://doi.org/10.1139/cjfr-2018-0520},
}

@Article{Cabral2019,
  author   = {Cabral, Juliano Sarmento and Wiegand, Kerstin and Kreft, Holger},
  title    = {Interactions between ecological, evolutionary and environmental processes unveil complex dynamics of insular plant diversity},
  journal  = {Journal of Biogeography},
  year     = {2019},
  volume   = {46},
  number   = {7},
  pages    = {1582-1597},
  abstract = {Abstract Aims Understanding how biodiversity emerges and how it varies in space and time requires integration of the underlying processes that affect biodiversity at different levels of ecological organization. We present BioGEEM (BioGeographical Eco-Evolutionary Model), a spatially explicit model that integrates theories and processes understood to drive biodiversity dynamics. We investigated the necessary degree of mechanistic complexity by exploring simulation experiments to evaluate the relative roles of the underlying processes across spatio-temporal scales and ecological levels (e.g. populations, species, communities). Location Hypothetical oceanic islands. Methods BioGEEM is stochastic and grid-based, and it integrates ecological (metabolic constraints, demography, dispersal and competition), evolutionary (mutation and speciation) and environmental (geo-climatic dynamics) processes. Plants on oceanic islands served as a model system. We ran the simulations both with all processes on and with selected processes switched off to assess the role of each process from the emergent patterns. Results The full model was able to generate patterns matching empirical evidence and theoretical expectations. Population sizes were largest on young islands, and species, particularly endemics, better filled their potential range on young and old islands due to limited area and reduced competition. Richness peaked at mid-elevations. The proportion of endemics was highest in old, large and isolated environments within the islands. Species and trait richness showed unimodal temporal trends. Switching off selected processes led to several unrealistic patterns, including the evolution of super-dominant species, extremely high richness and weakened spatial diversity gradients. Main conclusions The main predictions derived from BioGEEM are: Competition has cross-scale effects on diversity. Hump-shaped temporal dynamics can be obtained without speciation. Endemic species seem less susceptible to extinction than native non-endemic species. Endemism reflects stronger geographical and environmental isolation. Finally, only the integration of all implemented processes generates realistic spatio-temporal dynamics at population, species, community and assemblage levels.},
  comment  = {public frontpage},
  doi      = {10.1111/jbi.13606},
  eprint   = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/jbi.13606},
  keywords = {demography, dispersal, interspecific competition, island biogeography, mechanistic simulation model, metabolic theory, plant community, process-based niche model, speciation, species richness},
  url      = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jbi.13606},
}

Abstract Aims Understanding how biodiversity emerges and how it varies in space and time requires integration of the underlying processes that affect biodiversity at different levels of ecological organization. We present BioGEEM (BioGeographical Eco-Evolutionary Model), a spatially explicit model that integrates theories and processes understood to drive biodiversity dynamics. We investigated the necessary degree of mechanistic complexity by exploring simulation experiments to evaluate the relative roles of the underlying processes across spatio-temporal scales and ecological levels (e.g. populations, species, communities). Location Hypothetical oceanic islands. Methods BioGEEM is stochastic and grid-based, and it integrates ecological (metabolic constraints, demography, dispersal and competition), evolutionary (mutation and speciation) and environmental (geo-climatic dynamics) processes. Plants on oceanic islands served as a model system. We ran the simulations both with all processes on and with selected processes switched off to assess the role of each process from the emergent patterns. Results The full model was able to generate patterns matching empirical evidence and theoretical expectations. Population sizes were largest on young islands, and species, particularly endemics, better filled their potential range on young and old islands due to limited area and reduced competition. Richness peaked at mid-elevations. The proportion of endemics was highest in old, large and isolated environments within the islands. Species and trait richness showed unimodal temporal trends. Switching off selected processes led to several unrealistic patterns, including the evolution of super-dominant species, extremely high richness and weakened spatial diversity gradients. Main conclusions The main predictions derived from BioGEEM are: Competition has cross-scale effects on diversity. Hump-shaped temporal dynamics can be obtained without speciation. Endemic species seem less susceptible to extinction than native non-endemic species. Endemism reflects stronger geographical and environmental isolation. Finally, only the integration of all implemented processes generates realistic spatio-temporal dynamics at population, species, community and assemblage levels.

@Article{Cabral2019a,
  author   = {Cabral, Juliano Sarmento and Whittaker, Robert J. and Wiegand, Kerstin and Kreft, Holger},
  title    = {Assessing predicted isolation effects from the general dynamic model of island biogeography with an eco-evolutionary model for plants},
  journal  = {Journal of Biogeography},
  year     = {2019},
  volume   = {46},
  number   = {7},
  pages    = {1569-1581},
  abstract = {Abstract Aims The general dynamic model (GDM) of oceanic island biogeography predicts how biogeographical rates, species richness and endemism vary with island age, area and isolation. Here, we used a simulation model to assess whether the isolation-related predictions of the GDM may arise from low-level process at the level of individuals and populations. Location Hypothetical volcanic oceanic islands. Methods Our model considers (a) an idealized island ontogeny, (b) metabolic constraints and (c) stochastic, spatially explicit and niche-based processes at the level of individuals and populations (plant demography, dispersal, competition, mutation and speciation). Isolation scenarios involved varying the distance to mainland and the dispersal ability of the species pool. Results For all isolation scenarios, we obtained humped temporal trends for species richness, endemic richness, proportion of endemic species derived from within-island radiation, number of radiating lineages, number of species per radiating lineage and biogeographical rates. The proportion of endemics derived from mainland–island differentiation and of all endemics steadily increased over time. Extinction rates of endemic species peaked later than for non-endemic species. Species richness and the number of endemics derived from mainland–island differentiation decreased with isolation as did rates of colonization, mainland–island differentiation and extinction. The proportion of all endemics and of radiated endemics, the number of radiated endemics, of radiating lineages, and of species per radiating lineage and the within-island radiation rate all increased with isolation. Main conclusions Our results lend strong support to most of the isolation-related GDM predictions. New insights include an increasing proportion of endemics, particularly those arising from mainland–island differentiation, across isolation scenarios, as well as extinction trends of endemics differing from the overall extinction rates, with a much later peak. These results demonstrate how simulation models focusing on low ecological levels provide tools to assess biogeographical-scale predictions and to develop more detailed predictions for further empirical tests.},
  comment  = {public frontpage},
  doi      = {10.1111/jbi.13603},
  eprint   = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/jbi.13603},
  keywords = {BioGEEM, general dynamic model, interspecific competition, island biogeography, isolation effects, metabolic theory, oceanic islands, plant endemism, process-based models, speciation rate},
  url      = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jbi.13603},
}

Abstract Aims The general dynamic model (GDM) of oceanic island biogeography predicts how biogeographical rates, species richness and endemism vary with island age, area and isolation. Here, we used a simulation model to assess whether the isolation-related predictions of the GDM may arise from low-level process at the level of individuals and populations. Location Hypothetical volcanic oceanic islands. Methods Our model considers (a) an idealized island ontogeny, (b) metabolic constraints and (c) stochastic, spatially explicit and niche-based processes at the level of individuals and populations (plant demography, dispersal, competition, mutation and speciation). Isolation scenarios involved varying the distance to mainland and the dispersal ability of the species pool. Results For all isolation scenarios, we obtained humped temporal trends for species richness, endemic richness, proportion of endemic species derived from within-island radiation, number of radiating lineages, number of species per radiating lineage and biogeographical rates. The proportion of endemics derived from mainland–island differentiation and of all endemics steadily increased over time. Extinction rates of endemic species peaked later than for non-endemic species. Species richness and the number of endemics derived from mainland–island differentiation decreased with isolation as did rates of colonization, mainland–island differentiation and extinction. The proportion of all endemics and of radiated endemics, the number of radiated endemics, of radiating lineages, and of species per radiating lineage and the within-island radiation rate all increased with isolation. Main conclusions Our results lend strong support to most of the isolation-related GDM predictions. New insights include an increasing proportion of endemics, particularly those arising from mainland–island differentiation, across isolation scenarios, as well as extinction trends of endemics differing from the overall extinction rates, with a much later peak. These results demonstrate how simulation models focusing on low ecological levels provide tools to assess biogeographical-scale predictions and to develop more detailed predictions for further empirical tests.

@Article{Dislich2018,
  author    = {Dislich, Claudia and Hettig, Elisabeth and Salecker, Jan and Heinonen, Johannes and Lay, Jann and Meyer, Katrin M. and Wiegand, Kerstin and Tarigan, Suria},
  title     = {{Land-use change in oil palm dominated tropical landscapes—An agent-based model to explore ecological and socio-economic trade-offs}},
  journal   = {PLOS ONE},
  year      = {2018},
  volume    = {13},
  number    = {1},
  pages     = {e0190506},
  month     = {jan},
  issn      = {1932-6203},
  url_pdf   = {http://uni-goettingen.de/docs/396ae7967961248a393e20be62750a4d.pdf},
  abstract  = {Land-use changes have dramatically transformed tropical landscapes. We describe an ecological-economic land-use change model as an integrated, exploratory tool used to analyze how tropical land-use change affects ecological and socio-economic functions. The model analysis seeks to determine what kind of landscape mosaic can improve the ensemble of ecosystem functioning, biodiversity, and economic benefit based on the synergies and trade-offs that we have to account for. More specifically, (1) how do specific ecosystem functions, such as carbon storage, and economic functions, such as household consumption, relate to each other? (2) How do external factors, such as the output prices of crops, affect these relationships? (3) How do these relationships change when production inefficiency differs between smallholder farmers and learning is incorporated? We initialize the ecological-economic model with artificially generated land-use maps parameterized to our study region. The economic sub-model simulates smallholder land-use management decisions based on a profit maximization assumption. Each household determines factor inputs for all household fields and decides on land-use change based on available wealth. The ecological sub-model includes a simple account of carbon sequestration in above-ground and below-ground vegetation. We demonstrate model capabilities with results on household consumption and carbon sequestration from different output price and farming efficiency scenarios. The overall results reveal complex interactions between the economic and ecological spheres. For instance, model scenarios with heterogeneous crop-specific household productivity reveal a comparatively high inertia of land-use change. Our model analysis even shows such an increased temporal stability in landscape composition and carbon stocks of the agricultural area under dynamic price trends. These findings underline the utility of ecological-economic models, such as ours, to act as exploratory tools which can advance our understanding of the mechanisms underlying the trade-offs and synergies of ecological and economic functions in tropical landscapes.},
  comment   = {public frontpage},
  doi       = {10.1371/journal.pone.0190506},
  editor    = {Webb, Edward},
  publisher = {Public Library of Science},
  url       = {http://dx.plos.org/10.1371/journal.pone.0190506},
}

Land-use changes have dramatically transformed tropical landscapes. We describe an ecological-economic land-use change model as an integrated, exploratory tool used to analyze how tropical land-use change affects ecological and socio-economic functions. The model analysis seeks to determine what kind of landscape mosaic can improve the ensemble of ecosystem functioning, biodiversity, and economic benefit based on the synergies and trade-offs that we have to account for. More specifically, (1) how do specific ecosystem functions, such as carbon storage, and economic functions, such as household consumption, relate to each other? (2) How do external factors, such as the output prices of crops, affect these relationships? (3) How do these relationships change when production inefficiency differs between smallholder farmers and learning is incorporated? We initialize the ecological-economic model with artificially generated land-use maps parameterized to our study region. The economic sub-model simulates smallholder land-use management decisions based on a profit maximization assumption. Each household determines factor inputs for all household fields and decides on land-use change based on available wealth. The ecological sub-model includes a simple account of carbon sequestration in above-ground and below-ground vegetation. We demonstrate model capabilities with results on household consumption and carbon sequestration from different output price and farming efficiency scenarios. The overall results reveal complex interactions between the economic and ecological spheres. For instance, model scenarios with heterogeneous crop-specific household productivity reveal a comparatively high inertia of land-use change. Our model analysis even shows such an increased temporal stability in landscape composition and carbon stocks of the agricultural area under dynamic price trends. These findings underline the utility of ecological-economic models, such as ours, to act as exploratory tools which can advance our understanding of the mechanisms underlying the trade-offs and synergies of ecological and economic functions in tropical landscapes.

@Article{Simpkins2018,
  author   = {Simpkins, Craig E. and Dennis, Todd E. and Etherington, Thomas R. and Perry, George L.W.},
  title    = {{Assessing the performance of common landscape connectivity metrics using a virtual ecologist approach}},
  journal  = {Ecological Modelling},
  year     = {2018},
  volume   = {367},
  pages    = {13--23},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/91b6c7a8a5929789f6ef9a94dabf2ecf.pdf/Simpkins_et_al_2018_ECOLOGICAL_MODELLING_assessing_performance_common_landscape_connectivity_metrics.pdf},
  abstract = {Due to increasing habitat fragmentation and concern about its ecological effects, there has been an upsurge in the use of landscape connectivity estimates in conservation planning. Measuring connectivity is challenging, resulting in a limited understanding of the efficacy of connectivity estimation techniques and the conditions under which they perform best. We evaluated the performance of four commonly used connectivity metrics – Euclidean distance; least-cost paths (LCP) length and cost; and circuit theory's resistance distance – over a variety of simulated landscapes. We developed an agent-based model simulating the dispersal of individuals with different behavioural traits across landscapes varying in their spatial structure. The outcomes of multiple dispersal attempts were used to obtain ‘true' connectivity. These ‘true' connectivity measures were then compared to estimates generated using the connectivity metrics, employing the simulated landscapes as cost-surfaces. The four metrics differed in the strength of their correlation with true connectivity; resistance distance showed the strongest correlation, closely followed by LCP cost, with Euclidean distance having the weakest. Landscape structure and species behavioural attributes only weakly predicted the performance of resistance distance, LCP cost and length estimates, with none predicting Euclidean distance's efficacy. Our results indicate that resistance distance and LCP cost produce the most accurate connectivity estimates, although their absolute performance under different conditions is difficult to predict. We emphasise the importance of testing connectivity estimates against patterns derived from independent data, such as those acquired from tracking studies. Our findings should help to inform a more refined implementation of connectivity metrics in conservation management.},
  comment  = {public frontpage},
  doi      = {10.1016/j.ecolmodel.2017.11.001},
  keywords = {Agent-based model,Circuit theory,Euclidean distance,Least-cost modelling,Resistance,Simulated landscape},
}

Due to increasing habitat fragmentation and concern about its ecological effects, there has been an upsurge in the use of landscape connectivity estimates in conservation planning. Measuring connectivity is challenging, resulting in a limited understanding of the efficacy of connectivity estimation techniques and the conditions under which they perform best. We evaluated the performance of four commonly used connectivity metrics – Euclidean distance; least-cost paths (LCP) length and cost; and circuit theory's resistance distance – over a variety of simulated landscapes. We developed an agent-based model simulating the dispersal of individuals with different behavioural traits across landscapes varying in their spatial structure. The outcomes of multiple dispersal attempts were used to obtain ‘true' connectivity. These ‘true' connectivity measures were then compared to estimates generated using the connectivity metrics, employing the simulated landscapes as cost-surfaces. The four metrics differed in the strength of their correlation with true connectivity; resistance distance showed the strongest correlation, closely followed by LCP cost, with Euclidean distance having the weakest. Landscape structure and species behavioural attributes only weakly predicted the performance of resistance distance, LCP cost and length estimates, with none predicting Euclidean distance's efficacy. Our results indicate that resistance distance and LCP cost produce the most accurate connectivity estimates, although their absolute performance under different conditions is difficult to predict. We emphasise the importance of testing connectivity estimates against patterns derived from independent data, such as those acquired from tracking studies. Our findings should help to inform a more refined implementation of connectivity metrics in conservation management.

@Article{Ward2018a,
  author   = {Ward, David and Trinogga, Juliane and Wiegand, Kerstin and du Toit, Justin and Okubamichael, Desale and Reinsch, Sabine and Schleicher, Jana},
  journal  = {Geoderma},
  title    = {{Large shrubs increase soil nutrients in a semi-arid savanna}},
  year     = {2018},
  issn     = {00167061},
  pages    = {153--162},
  volume   = {310},
  abstract = {The soil under savanna woody species is often enriched in nutrients in what is termed an ‘island of fertility'. We tested for positive feedbacks between encroaching woody plants and soil fertility in two co-occurring shrub species at three sites. One of these shrub species is nitrogen-fixing, Acacia mellifera, and the other is non‑nitrogen-fixing, Tarchonanthus camphoratus; we compared these effects to the grasslands surrounding the shrub patches. We found that soil nutrient concentrations were usually related to shrub size rather than the species. Fertile patches developed underneath large shrubs as indicated by higher carbon and nitrogen concentrations, a higher CECeff(especially sodium, which is a limiting nutrient for grazing livestock) and a pH near 6. We found no difference in soil nitrogen between the N-fixing A. mellifera and T. camphoratus. Plant cover under large shrubs was less than in open grassland. There are ‘islands of fertility' under large shrubs. However, the development of fertility islands did not facilitate understorey growth. Thus, increased soil fertility had no positive feedback on overall vegetation composition. Negative effects of the woody vegetation may override the positive effects of increased soil nutrient availability.},
  comment  = {public frontpage},
  doi      = {10.1016/j.geoderma.2017.09.023},
  groups   = {Jana:1},
  keywords = {Acacia,Carbon,Fertility islands,Legumes,Nitrogen,Senegalia,Tarchonanthus,pH},
}

The soil under savanna woody species is often enriched in nutrients in what is termed an ‘island of fertility'. We tested for positive feedbacks between encroaching woody plants and soil fertility in two co-occurring shrub species at three sites. One of these shrub species is nitrogen-fixing, Acacia mellifera, and the other is non‑nitrogen-fixing, Tarchonanthus camphoratus; we compared these effects to the grasslands surrounding the shrub patches. We found that soil nutrient concentrations were usually related to shrub size rather than the species. Fertile patches developed underneath large shrubs as indicated by higher carbon and nitrogen concentrations, a higher CECeff(especially sodium, which is a limiting nutrient for grazing livestock) and a pH near 6. We found no difference in soil nitrogen between the N-fixing A. mellifera and T. camphoratus. Plant cover under large shrubs was less than in open grassland. There are ‘islands of fertility' under large shrubs. However, the development of fertility islands did not facilitate understorey growth. Thus, increased soil fertility had no positive feedback on overall vegetation composition. Negative effects of the woody vegetation may override the positive effects of increased soil nutrient availability.

@Article{Tarigan2018,
  author    = {Tarigan, S and Wiegand, K and Sunarti, S and Slamet, B},
  title     = {Minimum forest cover required for sustainable water flow regulation of a watershed: a case study in Jambi Province, Indonesia},
  journal   = {Hydrology and Earth System Sciences},
  year      = {2018},
  volume    = {22},
  pages     = {581-594},
  url_pdf   = {http://uni-goettingen.de/de/document/download/9336bb5d0412a99b2097d0dd7e945228.pdf/Tarigan_et_al_2018_HESS_minimum_forest_cover_for_sustainable_water_flow_regulation.pdf},
  comment   = {public frontpage},
  doi       = {https://doi.org/10.5194/hess-22-581-2018},
  owner     = {Jan},
  timestamp = {2018.01.25},
  url       = {https://www.hydrol-earth-syst-sci.net/22/581/2018/},
}

@Article{Simpkins2018a,
  author   = {Simpkins, C. E. and Lee, F. and Powers, B. F. and Anderson, S. and Asena, Q. and Brock, J. M. and Perry, G. L.},
  title    = {Population viability analyses in New Zealand: a review},
  journal  = {New Zealand Journal of Ecology},
  year     = {2018},
  volume   = {42},
  number   = {2},
  pages    = {0-0},
  url_pdf  = {http://uni-goettingen.de/de/document/download/f119f9aa6fe8f444d2e4284cc8128ba6.pdf/Simpkins_et_al_2018_NZ_JOURNAL_OF_ECOLOGY_PVA_in_New_Zealand_review.pdf},
  abstract = {Biodiversity assets often require conservation management, which, in turn, necessitates decisions about which ecosystem, community or species should be prioritised to receive resources. Population viability analysis (PVA) uses a suite of quantitative methods to estimate the likelihood of population decline and extinction for a given species, and can be used to assess a population's status, providing useful information to decision-makers. In New Zealand, a range of taxa have been analysed using the PVA approach, but the scope of its implementation has not previously been reviewed. We compiled a database of 78 published PVAs for New Zealand indigenous fauna and flora, along with details of the species considered, the data used to parametrise the model, and the technical details of their implementation. We assessed the taxa and threat status of the species for which PVA were conducted relative to the distribution of taxa across threat classes in the New Zealand Threat Classification System database. There were clear biases in the species selected for analysis, notably an over-representation of birds and threatened species in general, and an under-representation of invertebrates and plants. Model parameterisation and implementation were often not reported in a transparent or standardised way, which hinders model communication and reconstruction. To maximise the benefit of PVAs, we suggest that more attention should be given to the ecosystem-level importance of species, and to species whose threat status is changing rapidly or are not yet threatened. More clearly describing the parameterisation, underlying assumptions and implementation of PVAs will help to better contextualise their results and support reproducible ecological science and decision-making.},
  comment  = {public frontpage},
  doi      = {10.20417/nzjecol.42.32},
  keywords = {biodiversity, conservation, demographic models, extinction, population dynamics, population models},
  url      = {https://newzealandecology.org/nzje/3343},
}

Biodiversity assets often require conservation management, which, in turn, necessitates decisions about which ecosystem, community or species should be prioritised to receive resources. Population viability analysis (PVA) uses a suite of quantitative methods to estimate the likelihood of population decline and extinction for a given species, and can be used to assess a population's status, providing useful information to decision-makers. In New Zealand, a range of taxa have been analysed using the PVA approach, but the scope of its implementation has not previously been reviewed. We compiled a database of 78 published PVAs for New Zealand indigenous fauna and flora, along with details of the species considered, the data used to parametrise the model, and the technical details of their implementation. We assessed the taxa and threat status of the species for which PVA were conducted relative to the distribution of taxa across threat classes in the New Zealand Threat Classification System database. There were clear biases in the species selected for analysis, notably an over-representation of birds and threatened species in general, and an under-representation of invertebrates and plants. Model parameterisation and implementation were often not reported in a transparent or standardised way, which hinders model communication and reconstruction. To maximise the benefit of PVAs, we suggest that more attention should be given to the ecosystem-level importance of species, and to species whose threat status is changing rapidly or are not yet threatened. More clearly describing the parameterisation, underlying assumptions and implementation of PVAs will help to better contextualise their results and support reproducible ecological science and decision-making.

@Article{Hesselbarth2018,
  author   = {Hesselbarth, M.H.K and Wiegand, K. and Dreber, N. and Kellner, K. and Esser, D. and Tsvuurac, Z.},
  journal  = {Journal of Arid Environments},
  title    = {Density-dependent spatial patterning of woody plants differs between a semi-arid and a mesic savanna in South Africa},
  year     = {2018},
  pages    = {103-112},
  volume   = {157},
  abstract = {Savannas can be defined by the co-dominance of grasses and trees. Interactions between these two life forms are relatively well studied, whereas tree-tree interactions attracted increased attention only recently. However, the influence of woody plant density on tree-tree interactions is rarely considered. We studied tree-tree interactions in a semi-arid and a mesic savanna to test for differences between open and dense woody vegetation in relation to broad-scale environmental conditions. We applied spatial point pattern analysis to gain a better understanding of processes, such as competition, facilitation and disturbances, affecting the spatial distribution of trees. Competition between trees was most pronounced in dense vegetation, whereas facilitation effects were more common in open vegetation. Further, we found that factors shaping the spatial patterns differ with scale. At short tree-to-tree distances, results indicate limited seed dispersal as the most influential factor explaining the spatial distribution of trees. However, with increasing tree-to-tree distances, environmental heterogeneity in the semi-arid savanna and disturbances in the mesic savanna became more important. We conclude that studying tree-tree interactions in savannas should explicitly consider the actual woody plant density, especially when different savanna types are compared.},
  comment  = {public frontpage},
  doi      = {https://doi.org/10.1016/j.jaridenv.2018.06.002},
  groups   = {Jana:1},
  keywords = {Competition Facilitation Tree-tree interactions Point pattern analysis},
  url      = {https://www.sciencedirect.com/science/article/pii/S0140196318303422},
}

Savannas can be defined by the co-dominance of grasses and trees. Interactions between these two life forms are relatively well studied, whereas tree-tree interactions attracted increased attention only recently. However, the influence of woody plant density on tree-tree interactions is rarely considered. We studied tree-tree interactions in a semi-arid and a mesic savanna to test for differences between open and dense woody vegetation in relation to broad-scale environmental conditions. We applied spatial point pattern analysis to gain a better understanding of processes, such as competition, facilitation and disturbances, affecting the spatial distribution of trees. Competition between trees was most pronounced in dense vegetation, whereas facilitation effects were more common in open vegetation. Further, we found that factors shaping the spatial patterns differ with scale. At short tree-to-tree distances, results indicate limited seed dispersal as the most influential factor explaining the spatial distribution of trees. However, with increasing tree-to-tree distances, environmental heterogeneity in the semi-arid savanna and disturbances in the mesic savanna became more important. We conclude that studying tree-tree interactions in savannas should explicitly consider the actual woody plant density, especially when different savanna types are compared.

@Article{Radny2018,
  author   = {Radny, J. and Meyer, K.M.},
  journal  = {PeerJ},
  title    = {The role of biotic factors during plant establishment in novel communities assessed with an agent-based simulation model},
  year     = {2018},
  pages    = {6:e5342},
  abstract = {Background
Establishment success of non-native species is not only influenced by environmental conditions, but also by interactions with local competitors and enemies. The magnitude of these biotic interactions is mediated by species traits that reflect competitive strength or defence mechanisms. Our aim was to investigate the importance of species traits for successful establishment of non-native species in a native community exhibiting biotic resistance in the form of competition and herbivory.

Methods
We developed a trait-based, individual-based simulation model tracking the survival of non-native plants in a native community. In the model, non-native plants are characterized by high or low values of competition and defence traits. Model scenarios included variation of initial number of non-natives, intensity of competitive interaction, density of herbivores and density as well as mixture of the native community.

Results
Traits related to competition had a much greater impact on survival of non-native species than traits related to defence. Survival rates of strong competitors never fell below 50% while survival of weak competitors averaged at about 10%. Weak competitors were also much more susceptible to competitive pressures such as community density, composition and competition intensity. Strong competitors responded negatively to changes in competition intensity, but hardly to composition or density of the native community. High initial numbers of non-native individuals decreased survival rate of strong competitors, but increased the survival rate of weak competitors. Survival under herbivore attack was only slightly higher for plants with high defensive ability than for those with low defensive ability. Surprisingly, though, herbivory increased survival of species classified as weak competitors.

Discussion
High survival rates of strong non-native competitors relate to a higher probability of successful establishment than for weak competitors. However, the reduced survival of strong competitors at high initial numbers indicates a self-thinning effect, probably mediated by a strongly competitive milieu. For weak competitors, our model emphasizes positive effects of high propagule pressure known from field studies. General effects of herbivory or defence abilities on survival were not supported by our model. However, the positive effect of herbivory on survival of weak competitors indicated side effects of herbivory, such as weakening resident competitors. This might play an important role for establishment of non-natives in a new community.},
  comment  = {public frontpage},
  doi      = {10.7717/peerj.5342},
  keywords = {Invasive plant, Biotic interactions, Non-native species, Local establishment, Range shift, Herbivory, Competition, Agent-based model, Individual-based model, Trait-based model},
  url      = {https://peerj.com/articles/5342/},
  url_pdf  = {http://uni-goettingen.de/de/document/download/9f60837615917f0fc3a5df758393f0e5.pdf/Radny_Meyer_2018_role_biotic_factors_plant_establishment_novel_communities.pdf},
}

Background Establishment success of non-native species is not only influenced by environmental conditions, but also by interactions with local competitors and enemies. The magnitude of these biotic interactions is mediated by species traits that reflect competitive strength or defence mechanisms. Our aim was to investigate the importance of species traits for successful establishment of non-native species in a native community exhibiting biotic resistance in the form of competition and herbivory. Methods We developed a trait-based, individual-based simulation model tracking the survival of non-native plants in a native community. In the model, non-native plants are characterized by high or low values of competition and defence traits. Model scenarios included variation of initial number of non-natives, intensity of competitive interaction, density of herbivores and density as well as mixture of the native community. Results Traits related to competition had a much greater impact on survival of non-native species than traits related to defence. Survival rates of strong competitors never fell below 50% while survival of weak competitors averaged at about 10%. Weak competitors were also much more susceptible to competitive pressures such as community density, composition and competition intensity. Strong competitors responded negatively to changes in competition intensity, but hardly to composition or density of the native community. High initial numbers of non-native individuals decreased survival rate of strong competitors, but increased the survival rate of weak competitors. Survival under herbivore attack was only slightly higher for plants with high defensive ability than for those with low defensive ability. Surprisingly, though, herbivory increased survival of species classified as weak competitors. Discussion High survival rates of strong non-native competitors relate to a higher probability of successful establishment than for weak competitors. However, the reduced survival of strong competitors at high initial numbers indicates a self-thinning effect, probably mediated by a strongly competitive milieu. For weak competitors, our model emphasizes positive effects of high propagule pressure known from field studies. General effects of herbivory or defence abilities on survival were not supported by our model. However, the positive effect of herbivory on survival of weak competitors indicated side effects of herbivory, such as weakening resident competitors. This might play an important role for establishment of non-natives in a new community.

@Article{Radny2018a,
  author   = {Radny, J. and van der Putten, W.H. and Tielbörger, K. and Meyer, K.M.},
  title    = {{Influence of seed size on performance of non-native annual plant species in a novel community at two planting densities}},
  journal  = {Acta Oecologica},
  year     = {2018},
  volume   = {92},
  pages    = {131 - 137},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e1b23b028656400d8359353ceaa1d564.pdf/Radny_etal_2018_ActaOecologica.pdf},
  abstract = {Climate warming enables plant species to migrate to higher latitudes and altitudes. Within Europe, the Mediterranean harbours many species that might expand their ranges towards Western Europe. Small seed size may facilitate dispersal, however, it may impair establishment of the range-expanding plant species in the novel vegetation. In a greenhouse experiment, we examined effects of average seed size of Mediterranean plant species on their establishment in a mixed community of Western European plant species. Applying two levels of densities of the natives and a herbivory treatment, we tested how seed size is linked to response in plant growth and fitness in novel vegetation. While all non-native plant species showed a negative response to increased planting density, species with small seeds showed a less negative response. This effect persisted under herbivory. Our data suggest that small-seeded non-native plant species may tolerate competitive pressure from novel plant communities better than large-seeded species, so that small seed size may confer a higher probability of establishment of non-native species in novel communities.},
  comment  = {public frontpage},
  doi      = {10.1016/j.actao.2018.05.005},
  url      = {https://www.sciencedirect.com/science/article/pii/S1146609X17304022?via%3Dihub},
}

Climate warming enables plant species to migrate to higher latitudes and altitudes. Within Europe, the Mediterranean harbours many species that might expand their ranges towards Western Europe. Small seed size may facilitate dispersal, however, it may impair establishment of the range-expanding plant species in the novel vegetation. In a greenhouse experiment, we examined effects of average seed size of Mediterranean plant species on their establishment in a mixed community of Western European plant species. Applying two levels of densities of the natives and a herbivory treatment, we tested how seed size is linked to response in plant growth and fitness in novel vegetation. While all non-native plant species showed a negative response to increased planting density, species with small seeds showed a less negative response. This effect persisted under herbivory. Our data suggest that small-seeded non-native plant species may tolerate competitive pressure from novel plant communities better than large-seeded species, so that small seed size may confer a higher probability of establishment of non-native species in novel communities.

@Inbook{Meyer2018,
  chapter   = {Modeling Aboveground–Belowground Interactions},
  pages     = {47-68},
  title     = {Aboveground-Belowground Community Ecology},
  publisher = {Springer},
  year      = {2018},
  author    = {Meyer, K.M.},
  editor    = {Ohgushi, T. and Wurst, S. and Johnson, S.N.},
  volume    = {Ecological Studies 234},
  url_pdf   = {http://uni-goettingen.de/de/document/download/62128425e726dbfc1e65f950d2f1928e.pdf/Meyer_2018_BookChapter_Modeling_Aboveground_Belowground_Interactions.pdf},
  abstract  = {Models are powerful tools to capture the complexity of aboveground–belowground interactions in community ecology. Three general model aims can be distinguished: description, explanation, and prediction. These aims are covered by different model types such as conceptual models, graphical models, statistical models, functional–structural models, process-based models, reaction–diffusion models, cellular automaton models, and individual- or agent-based models. The available models of aboveground–belowground interactions always include interactions between root and shoot, and sometimes also trophic, competitive, facilitative, or mutualistic interactions. However, only very few of the existing aboveground–belowground models are community models that incorporate more than three species and more than one type of interaction. Furthermore, spatial relationships are rarely explicitly addressed. Thus, future approaches should (1) improve, simplify, and update current models, (2) extend current models to include more different interaction types and spatial relationships where this is justified by the model question, and (3) employ new modeling techniques such as game theoretical methods or Bayesian network models. Guidelines for model building are given based on the modeling cycle from question through concept, structure, and implementation to analysis and documentation. Close cooperation between empiricists and modelers will promote the success of future models of aboveground–belowground interactions.},
  comment   = {public frontpage},
  doi       = {10.1007/978-3-319-91614-9_3},
  url       = {https://link.springer.com/chapter/10.1007%2F978-3-319-91614-9_3},
}

Models are powerful tools to capture the complexity of aboveground–belowground interactions in community ecology. Three general model aims can be distinguished: description, explanation, and prediction. These aims are covered by different model types such as conceptual models, graphical models, statistical models, functional–structural models, process-based models, reaction–diffusion models, cellular automaton models, and individual- or agent-based models. The available models of aboveground–belowground interactions always include interactions between root and shoot, and sometimes also trophic, competitive, facilitative, or mutualistic interactions. However, only very few of the existing aboveground–belowground models are community models that incorporate more than three species and more than one type of interaction. Furthermore, spatial relationships are rarely explicitly addressed. Thus, future approaches should (1) improve, simplify, and update current models, (2) extend current models to include more different interaction types and spatial relationships where this is justified by the model question, and (3) employ new modeling techniques such as game theoretical methods or Bayesian network models. Guidelines for model building are given based on the modeling cycle from question through concept, structure, and implementation to analysis and documentation. Close cooperation between empiricists and modelers will promote the success of future models of aboveground–belowground interactions.

@Article{Sciaini2018,
  author   = {Sciaini, Marco and Fritsch, Matthias and Scherer, Cédric and Simpkins, Craig},
  journal  = {Methods in Ecology and Evolution},
  title    = {NLMR and landscapetools : An integrated environment for simulating and modifying neutral landscape models in R},
  year     = {2018},
  pages    = {2240– 2248},
  volume   = {9},
  abstract = {Neutral landscape models (NLMs) simulate landscape patterns based on theoretical distributions and can be used to systematically study the effect of landscape structure on ecological processes. NLMs are commonly used in landscape ecology to enhance the findings of field studies as well as in simulation studies to provide an underlying landscape. However, their creation so far has been limited to software that is platform dependent, does not allow a reproducible workflow or is not embedded in R, the prevailing programming language used by ecologists.

Here, we present two complementary R packages NLMR and landscapetools, that allow users to generate and manipulate NLMs in a single environment. They grant the simulation of the widest collection of NLMs found in any single piece of software thus far while allowing for easy manipulation in a self‐contained and reproducible workflow. The combination of both packages should stimulate a wider usage of NLMs in ecology. NLMR is a comprehensive collection of algorithms with which to simulate NLMs. landscapetools provides a utility toolbox which facilitates an easy workflow with simulated neutral landscapes and other raster data.

We show two example applications that illustrate potential use cases for NLMR and landscapetools: First, an agent‐based simulation study in which the effect of spatial structure on disease persistence was studied. The second example shows how increases in spatial scaling can introduce biases in calculated landscape metrics.

Simplifying the workflow around generating and handling NLMs should encourage an uptake in the usage of NLMs. NLMR and landscapetools are both generic frameworks that can be used in a variety of applications and are a further step to having a unified simulation environment in R for answering spatial research questions.},
  comment  = {public frontpage},
  doi      = {10.1111/2041-210X.13076},
  url      = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13076},
}

Neutral landscape models (NLMs) simulate landscape patterns based on theoretical distributions and can be used to systematically study the effect of landscape structure on ecological processes. NLMs are commonly used in landscape ecology to enhance the findings of field studies as well as in simulation studies to provide an underlying landscape. However, their creation so far has been limited to software that is platform dependent, does not allow a reproducible workflow or is not embedded in R, the prevailing programming language used by ecologists. Here, we present two complementary R packages NLMR and landscapetools, that allow users to generate and manipulate NLMs in a single environment. They grant the simulation of the widest collection of NLMs found in any single piece of software thus far while allowing for easy manipulation in a self‐contained and reproducible workflow. The combination of both packages should stimulate a wider usage of NLMs in ecology. NLMR is a comprehensive collection of algorithms with which to simulate NLMs. landscapetools provides a utility toolbox which facilitates an easy workflow with simulated neutral landscapes and other raster data. We show two example applications that illustrate potential use cases for NLMR and landscapetools: First, an agent‐based simulation study in which the effect of spatial structure on disease persistence was studied. The second example shows how increases in spatial scaling can introduce biases in calculated landscape metrics. Simplifying the workflow around generating and handling NLMs should encourage an uptake in the usage of NLMs. NLMR and landscapetools are both generic frameworks that can be used in a variety of applications and are a further step to having a unified simulation environment in R for answering spatial research questions.

@Article{Accatino2017,
  author   = {Accatino, F. and Ward, D. and Wiegand, K. and {De Michele}, C.},
  title    = {{Carrying capacity in arid rangelands during droughts: The role of temporal and spatial thresholds}},
  journal  = {Animal},
  year     = {2017},
  volume   = {11},
  number   = {2},
  pages    = {309--317},
  issn     = {1751732X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/9240d0a31d44181568563d98365bd06e.pdf/Accatino_et%20_al%20_2017_ANIMAL_carrying_capacity_arid_rangelands.pdf},
  abstract = {Assessing the carrying capacity is of primary importance in arid rangelands. This becomes even more important during droughts, when rangelands exhibit non-equilibrium dynamics, and the dynamics of livestock conditions and forage resource are decoupled. Carrying capacity is usually conceived as an equilibrium concept, that is, the consumer density that can co-exist in long-term equilibrium with the resource. As one of the first, here we address the concept of carrying capacity in systems, where there is no feedback between consumer and resource in a limited period of time. To this end, we developed an individual-based model describing the basic characteristics of a rangeland during a drought. The model represents a rangeland composed by a single water point and forage distributed all around, with livestock units moving from water to forage and vice versa, for eating and drinking. For each livestock unit we implemented an energy balance and we accounted for the gut-filling effect (i.e. only a limited amount of forage can be ingested per unit time). Our results showed that there is a temporal threshold above which livestock begin to experience energy deficit and burn fat reserves. We demonstrated that such a temporal threshold increases with the number of animals and decreases with the rangeland conditions (amount of forage). The temporal threshold corresponded to the time livestock take to consume all the forage within a certain distance from water, so that the livestock can return to water for drinking without spending more energy than they gain within a day. In this study, we highlight the importance of a time threshold in the assessment of carrying capacity in non-equilibrium conditions. Considering this time threshold could explain contrasting observations about the influence of livestock number on livestock conditions. In case of private rangelands, the herd size should be chosen so that the spatial threshold equals (or exceeds) the length of the drought.},
  comment  = {public},
  doi      = {10.1017/S1751731116001531},
  isbn     = {1751731116001},
  keywords = {drought,energy deficit,foraging,optimal herd size,water point},
  pmid     = {27452875},
}

Assessing the carrying capacity is of primary importance in arid rangelands. This becomes even more important during droughts, when rangelands exhibit non-equilibrium dynamics, and the dynamics of livestock conditions and forage resource are decoupled. Carrying capacity is usually conceived as an equilibrium concept, that is, the consumer density that can co-exist in long-term equilibrium with the resource. As one of the first, here we address the concept of carrying capacity in systems, where there is no feedback between consumer and resource in a limited period of time. To this end, we developed an individual-based model describing the basic characteristics of a rangeland during a drought. The model represents a rangeland composed by a single water point and forage distributed all around, with livestock units moving from water to forage and vice versa, for eating and drinking. For each livestock unit we implemented an energy balance and we accounted for the gut-filling effect (i.e. only a limited amount of forage can be ingested per unit time). Our results showed that there is a temporal threshold above which livestock begin to experience energy deficit and burn fat reserves. We demonstrated that such a temporal threshold increases with the number of animals and decreases with the rangeland conditions (amount of forage). The temporal threshold corresponded to the time livestock take to consume all the forage within a certain distance from water, so that the livestock can return to water for drinking without spending more energy than they gain within a day. In this study, we highlight the importance of a time threshold in the assessment of carrying capacity in non-equilibrium conditions. Considering this time threshold could explain contrasting observations about the influence of livestock number on livestock conditions. In case of private rangelands, the herd size should be chosen so that the spatial threshold equals (or exceeds) the length of the drought.

@Article{Botha2017,
  author    = {Botha, M. and Siebert, S.J. and {Van den Berg}, J. and Ellis, S.M. and Dreber, N.},
  title     = {{Plant functional types differ between the grassland and savanna biomes along an agro-ecosystem disturbance gradient in South Africa}},
  journal   = {South African Journal of Botany},
  year      = {2017},
  volume    = {113},
  pages     = {308--317},
  month     = {nov},
  issn      = {0254-6299},
  url_pdf   = {http://uni-goettingen.de/de/document/download/9a3c4e93661af6aa43d253d87d422588.pdf/Botha_et_al_2017_SAJB_plant_functional_types_agro-ecosystem_disturbance_gradient.pdf},
  abstract  = {Intensive, large-scale cultivation of food crops has led to major biodiversity loss worldwide due to fragmentation and degradation of remnant semi-natural habitat within agro-ecosystems. The response of vegetation to these disturbances is often measured in terms of taxonomic diversity loss. However, some plant groups may have more pronounced negative reactions to agricultural disturbance than others, which may not necessarily be expressed in the overall species diversity of the community. It is now widely accepted that the responses of plant taxa to environmental disturbances may be more directly linked to characteristics or traits that enable or hinder their persistence in disturbed environments. This highlights the need to assess the impacts of agricultural disturbance on the abundance patterns and diversity of specific plant traits and functional types. Maize agriculture is a common land-use feature in the grassy biomes of South Africa, but the effect that crop production has on surrounding semi-natural vegetation is still relatively unknown. In this study, we describe the specific functional trait patterns of plant communities associated with maize agro-ecosystems in six localities situated within the Grassland and Savanna biomes of South Africa. Although functional diversity was severely decreased in maize fields, marginal vegetation (30–100m from crop field edges) displayed no indication of functional diversity loss or major changes in trait composition. Chamaephytic and hemicryptophytic (perennial) life forms, nitrogen-fixing ability and spinescence were trait attributes that were most frequently found in semi-natural vegetation but were lost in the crop field environment. Inside the maize fields, these trait attributes were replaced by annual, low-growing individuals with clonal parts and long-range dispersal mechanisms that can establish in the ephemeral crop field environment. Observed patterns were different for grassland and savanna maize fields, indicating that maize fields situated in the Grassland and Savanna biomes favoured different plant trait assemblages.},
  comment   = {public},
  doi       = {10.1016/J.SAJB.2017.09.008},
  publisher = {Elsevier},
  url       = {https://www.sciencedirect.com/science/article/pii/S0254629917306956},
}

Intensive, large-scale cultivation of food crops has led to major biodiversity loss worldwide due to fragmentation and degradation of remnant semi-natural habitat within agro-ecosystems. The response of vegetation to these disturbances is often measured in terms of taxonomic diversity loss. However, some plant groups may have more pronounced negative reactions to agricultural disturbance than others, which may not necessarily be expressed in the overall species diversity of the community. It is now widely accepted that the responses of plant taxa to environmental disturbances may be more directly linked to characteristics or traits that enable or hinder their persistence in disturbed environments. This highlights the need to assess the impacts of agricultural disturbance on the abundance patterns and diversity of specific plant traits and functional types. Maize agriculture is a common land-use feature in the grassy biomes of South Africa, but the effect that crop production has on surrounding semi-natural vegetation is still relatively unknown. In this study, we describe the specific functional trait patterns of plant communities associated with maize agro-ecosystems in six localities situated within the Grassland and Savanna biomes of South Africa. Although functional diversity was severely decreased in maize fields, marginal vegetation (30–100m from crop field edges) displayed no indication of functional diversity loss or major changes in trait composition. Chamaephytic and hemicryptophytic (perennial) life forms, nitrogen-fixing ability and spinescence were trait attributes that were most frequently found in semi-natural vegetation but were lost in the crop field environment. Inside the maize fields, these trait attributes were replaced by annual, low-growing individuals with clonal parts and long-range dispersal mechanisms that can establish in the ephemeral crop field environment. Observed patterns were different for grassland and savanna maize fields, indicating that maize fields situated in the Grassland and Savanna biomes favoured different plant trait assemblages.

@Article{Dislich2017,
  author   = {Dislich, Claudia and Keyel, Alexander C. and Salecker, Jan and Kisel, Yael and Meyer, Katrin M. and Auliya, Mark and Barnes, Andrew D. and Corre, Marife D. and Darras, Kevin and Faust, Heiko and Hess, Bastian and Klasen, Stephan and Knohl, Alexander and Kreft, Holger and Meijide, Ana and Nurdiansyah, Fuad and Otten, Fenna and Pe'er, Guy and Steinebach, Stefanie and Tarigan, Suria and T{\"{o}}lle, Merja H. and Tscharntke, Teja and Wiegand, Kerstin},
  title    = {{A review of the ecosystem functions in oil palm plantations, using forests as a reference system}},
  journal  = {Biological Reviews},
  year     = {2017},
  volume   = {92},
  number   = {3},
  pages    = {1539--1569},
  issn     = {1469185X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/53135cfc82a2d81cf8b97e4cf12018cb.pdf/Dislich_et_al_2017_BIOLOGICAL_REVIEWS_ecosystem_functions_oil_palm_plantations.pdf},
  abstract = {ABSTRACT Oil palm plantations have expanded rapidly in recent decades. This large-scale land-use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pestmanagement, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The},
  comment  = {public},
  doi      = {10.1111/brv.12295},
  isbn     = {2015111646},
  keywords = {Elaeis guineensis,biodiversity,ecosystem functions,ecosystem services,land-use change,oil palm},
  pmid     = {27511961},
}

ABSTRACT Oil palm plantations have expanded rapidly in recent decades. This large-scale land-use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pestmanagement, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The

@Misc{Dreber2017,
  author    = {Dreber, Niels and van Rooyen, Salmon E. and Kellner, Klaus},
  title     = {{Relationship of plant diversity and bush cover in rangelands of a semi-arid Kalahari savannah, South Africa}},
  year      = {2017},
  url_pdf   = {http://uni-goettingen.de/de/document/download/4091f5a612b260762f295beee017931a.pdf/Dreber_et_al_2017_AFRICAN_J_ECOLOGY_relationship_plant_diversity_bush_cover_savannah.pdf},
  booktitle = {African Journal of Ecology},
  comment   = {public},
  doi       = {10.1111/aje.12425},
  issn      = {13652028},
}

@Article{Hudson2017,
  author   = {Hudson et al.,},
  title    = {{The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project}},
  journal  = {Ecology and Evolution},
  year     = {2017},
  volume   = {7},
  number   = {1},
  pages    = {145--188},
  month    = {jan},
  issn     = {20457758},
  url_pdf  = {http://uni-goettingen.de/de/document/download/86499b135e304d81675c401e71d72693.pdf/Hudson_et_al_2017_ECOLOGY_EVOLUTION_database_PREDICTS_project.pdf},
  comment  = {public},
  doi      = {10.1002/ece3.2579},
  keywords = {data sharing,global biodiversity modeling,global change,habitat destruction,land use},
  url      = {http://doi.wiley.com/10.1002/ece3.2579},
}

@Article{Li2017,
  author   = {Li, Yuanheng and Brose, Ulrich and Meyer, Katrin and Rall, Bj{\"{o}}rn C.},
  title    = {{How patch size and refuge availability change interaction strength and population dynamics: a combined individual- and population-based modeling experiment}},
  journal  = {PeerJ},
  year     = {2017},
  volume   = {5},
  pages    = {e2993},
  issn     = {2167-8359},
  url_pdf  = {http://uni-goettingen.de/de/document/download/166ea9578870c8661aea01ebc23eb310.pdf/Li_et_al_2017_PEERJ_patch_size_refuge_availability_change_interaction_strength_population_dynamics.pdf},
  abstract = {{\textless}p{\textgreater} Knowledge on how functional responses (a measurement of feeding interaction strength) are affected by patch size and habitat complexity (represented by refuge availability) is crucial for understanding food-web stability and subsequently biodiversity. Due to their laborious character, it is almost impossible to carry out systematic empirical experiments on functional responses across wide gradients of patch sizes and refuge availabilities. Here we overcame this issue by using an individual-based model (IBM) to simulate feeding experiments. The model is based on empirically measured traits such as body-mass dependent speed and capture success. We simulated these experiments in patches ranging from sizes of petri dishes to natural patches in the field. Moreover, we varied the refuge availability within the patch independently of patch size, allowing for independent analyses of both variables. The maximum feeding rate (the maximum number of prey a predator can consume in a given time frame) is independent of patch size and refuge availability, as it is the physiological upper limit of feeding rates. Moreover, the results of these simulations revealed that a type III functional response, which is known to have a stabilizing effect on population dynamics, fitted the data best. The half saturation density (the prey density where a predator consumes half of its maximum feeding rate) increased with refuge availability but was only marginally influenced by patch size. Subsequently, we investigated how patch size and refuge availability influenced stability and coexistence of predator-prey systems. Following common practice, we used an allometric scaled Rosenzweig–MacArthur predator-prey model based on results from our {\textless}italic{\textgreater}in silico{\textless}/italic{\textgreater} IBM experiments. The results suggested that densities of both populations are nearly constant across the range of patch sizes simulated, resulting from the constant interaction strength across the patch sizes. However, constant densities with decreasing patch sizes mean a decrease of absolute number of individuals, consequently leading to extinction of predators in the smallest patches. Moreover, increasing refuge availabilities also allowed predator and prey to coexist by decreased interaction strengths. Our results underline the need for protecting large patches with high habitat complexity to sustain biodiversity. {\textless}/p{\textgreater}},
  comment  = {public},
  doi      = {10.7717/peerj.2993},
  url      = {https://peerj.com/articles/2993},
}

\textlessp\textgreater Knowledge on how functional responses (a measurement of feeding interaction strength) are affected by patch size and habitat complexity (represented by refuge availability) is crucial for understanding food-web stability and subsequently biodiversity. Due to their laborious character, it is almost impossible to carry out systematic empirical experiments on functional responses across wide gradients of patch sizes and refuge availabilities. Here we overcame this issue by using an individual-based model (IBM) to simulate feeding experiments. The model is based on empirically measured traits such as body-mass dependent speed and capture success. We simulated these experiments in patches ranging from sizes of petri dishes to natural patches in the field. Moreover, we varied the refuge availability within the patch independently of patch size, allowing for independent analyses of both variables. The maximum feeding rate (the maximum number of prey a predator can consume in a given time frame) is independent of patch size and refuge availability, as it is the physiological upper limit of feeding rates. Moreover, the results of these simulations revealed that a type III functional response, which is known to have a stabilizing effect on population dynamics, fitted the data best. The half saturation density (the prey density where a predator consumes half of its maximum feeding rate) increased with refuge availability but was only marginally influenced by patch size. Subsequently, we investigated how patch size and refuge availability influenced stability and coexistence of predator-prey systems. Following common practice, we used an allometric scaled Rosenzweig–MacArthur predator-prey model based on results from our \textlessitalic\textgreaterin silico\textless/italic\textgreater IBM experiments. The results suggested that densities of both populations are nearly constant across the range of patch sizes simulated, resulting from the constant interaction strength across the patch sizes. However, constant densities with decreasing patch sizes mean a decrease of absolute number of individuals, consequently leading to extinction of predators in the smallest patches. Moreover, increasing refuge availabilities also allowed predator and prey to coexist by decreased interaction strengths. Our results underline the need for protecting large patches with high habitat complexity to sustain biodiversity. \textless/p\textgreater

@Conference{Salecker2017,
  author    = {Salecker, Jan and Dislich, Claudia and Hettig, Elisabeth and Heinonen, Johannes and Lay, Jann and Meyer, Katrin M. and Wiegand, Kerstin and Tarigan, Suria},
  booktitle = {Conference Talk, esa annual meeting 2017, Portland, USA},
  title     = {{Land-use change in oil palm dominated tropical landscapes—An agent-based model to explore ecological and socio-economic trade-offs}},
  year      = {2017},
  groups    = {Jana:1},
  owner     = {Jan},
  timestamp = {2018.01.25},
}

@Article{Accatino2016,
  author   = {Accatino, Francesco and Wiegand, Kerstin and Ward, David and {De Michele}, Carlo},
  title    = {{Trees, grass, and fire in humid savannas-The importance of life history traits and spatial processes}},
  journal  = {Ecological Modelling},
  year     = {2016},
  volume   = {320},
  pages    = {135--144},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/9a134a62292d9d2c223749a6500cf9ca.pdf/Accatino_et_al_2016_ECOLOGICAL_MODELLING_trees_grass_fire_humid_savannas.pdf},
  abstract = {We develop a model to investigate how trees can invade the grass stratum in humid savannas despite repeated fires. In the literature, it is clear that fire reduces tree canopy in savannas. However, fire alone may not be sufficient to prevent tree invasion because there are ecological mechanisms that hamper fire spread by undermining the continuity and density of the grass stratum, which is the means of fire propagation in savannas. Our model is spatially explicit and individual-based, and includes two important factors characterizing the interactions between fire, trees, and grass in savannas, viz. space and the strategies that trees use to cope with fire. The strategies that trees employ against fire emerge from life history traits. According to these strategies, we classify savanna trees into three categories: resprouters, which are able to resprout after their aboveground biomass is burned; resisters, which are able to resist fire due to a thick bark even in the juvenile stages; avoiders, which are very fire-vulnerable in the juvenile stages, but are able to grow fast in the absence of fire. Our results show that trees can invade the grass stratum and finally suppress fire spread because one of the following occurs: (1) trees may resprout and form a population that persists despite repeated effective fires; (2) trees may be fire-resistant; (3) if trees are fire-vulnerable they may cluster and grow in density until fire is prevented. Our results show that fire can be effective in preventing the initiation of the invasion process in the grass stratum. However, once the invasion process has begun, fire alone is not able to reverse this process because of the strategies employed by trees. Furthermore, when a high tree density is reached, grass density is insufficient to allow effective fire spread. From a management point of view, our results imply that fire must be coupled with other factors (browsing, mechanical thinning) to reduce tree density in encroached areas.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2015.09.014},
  isbn     = {0304-3800},
  keywords = {Fire-vegetation feedbacks,Individual-based model,Resprouting,Tree clustering,Woody plant encroachment},
}

We develop a model to investigate how trees can invade the grass stratum in humid savannas despite repeated fires. In the literature, it is clear that fire reduces tree canopy in savannas. However, fire alone may not be sufficient to prevent tree invasion because there are ecological mechanisms that hamper fire spread by undermining the continuity and density of the grass stratum, which is the means of fire propagation in savannas. Our model is spatially explicit and individual-based, and includes two important factors characterizing the interactions between fire, trees, and grass in savannas, viz. space and the strategies that trees use to cope with fire. The strategies that trees employ against fire emerge from life history traits. According to these strategies, we classify savanna trees into three categories: resprouters, which are able to resprout after their aboveground biomass is burned; resisters, which are able to resist fire due to a thick bark even in the juvenile stages; avoiders, which are very fire-vulnerable in the juvenile stages, but are able to grow fast in the absence of fire. Our results show that trees can invade the grass stratum and finally suppress fire spread because one of the following occurs: (1) trees may resprout and form a population that persists despite repeated effective fires; (2) trees may be fire-resistant; (3) if trees are fire-vulnerable they may cluster and grow in density until fire is prevented. Our results show that fire can be effective in preventing the initiation of the invasion process in the grass stratum. However, once the invasion process has begun, fire alone is not able to reverse this process because of the strategies employed by trees. Furthermore, when a high tree density is reached, grass density is insufficient to allow effective fire spread. From a management point of view, our results imply that fire must be coupled with other factors (browsing, mechanical thinning) to reduce tree density in encroached areas.

@Article{Dao2016,
  author   = {Dao, Thi Hoa Hong and Saborowski, Joachim and H{\"{o}}lscher, Dirk},
  title    = {{Patterns of tree community differences in the core and buffer zones of a nature reserve in north-western Vietnam}},
  journal  = {Global Ecology and Conservation},
  year     = {2016},
  volume   = {8},
  pages    = {220--229},
  issn     = {23519894},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2b1bdd493d8749bbe8e48ca967880bdc.pdf/Dao_et_al_2016_GLOBAL_ECOL_AND_CONS_patterns_tree_community_differences_nature_reserve_Vietnam.pdf},
  abstract = {In tropical forest conservation, areas with full statutory protection are often surrounded by buffer zones. Information on the patterns of tree community structure differences in these zones is helpful to evaluate the conservation efficacy. Our study was implemented within a biodiversity hotspot, in the Ta Xua Nature Reserve of north-western Vietnam, which has a statutorily protected core zone and a buffer zone, where local H'Mong people are permitted low intensity forest use. The forests are rich in tree species (249 observed). Many of these tree species provide non-timber forest products (NTFPs) (48{\%}) or valuable timber (22{\%}), and 18 species are red-listed. Overall tree density was not different in the two zones, but tree diameter and species richness were lower in the buffer zone. At the tree level, logistic regression analysis indicated that red-listed status, large diameter, and low density of conspecifics increased the probability of tree absence from the buffer zone but not the potential use as a NTFP. However, most NTFP species had different densities in the core and buffer zones, and this correlated with signs of human interference. At the species level, the density of species was the most important variable, and rarity strongly increased the probability of species absence. Our results also indicate that rare and red-listed trees were depleted in the buffer zone. In consideration of conservation goals, the future monitoring of these species at the Ta Xua Nature Reserve and other protected areas is needed, and conservation measures most likely need to be improved.},
  comment  = {public},
  doi      = {10.1016/j.gecco.2016.09.011},
  keywords = {Conservation,Diversity,Logistic model,Non-timber forest products,Rarity,Timber},
}

In tropical forest conservation, areas with full statutory protection are often surrounded by buffer zones. Information on the patterns of tree community structure differences in these zones is helpful to evaluate the conservation efficacy. Our study was implemented within a biodiversity hotspot, in the Ta Xua Nature Reserve of north-western Vietnam, which has a statutorily protected core zone and a buffer zone, where local H'Mong people are permitted low intensity forest use. The forests are rich in tree species (249 observed). Many of these tree species provide non-timber forest products (NTFPs) (48%) or valuable timber (22%), and 18 species are red-listed. Overall tree density was not different in the two zones, but tree diameter and species richness were lower in the buffer zone. At the tree level, logistic regression analysis indicated that red-listed status, large diameter, and low density of conspecifics increased the probability of tree absence from the buffer zone but not the potential use as a NTFP. However, most NTFP species had different densities in the core and buffer zones, and this correlated with signs of human interference. At the species level, the density of species was the most important variable, and rarity strongly increased the probability of species absence. Our results also indicate that rare and red-listed trees were depleted in the buffer zone. In consideration of conservation goals, the future monitoring of these species at the Ta Xua Nature Reserve and other protected areas is needed, and conservation measures most likely need to be improved.

@Article{Drescher2016,
  author   = {Drescher, Jochen and Rembold, Katja and Allen, Kara and Becksch{\"{a}}fer, Philip and Buchori, Damayanti and Clough, Yann and Faust, Heiko and Fauzi, Anas M. and Gunawan, Dodo and Hertel, Dietrich and Irawan, Bambang and Jaya, I. Nengah S. and Klarner, Bernhard and Kleinn, Christoph and Knohl, Alexander and Kotowska, Martyna M. and Krashevska, Valentyna and Krishna, Vijesh and Leuschner, Christoph and Lorenz, Wolfram and Meijide, Ana and Melati, Dian and Nomura, Miki and P{\'{e}}rez-Cruzado, C{\'{e}}sar and Qaim, Matin and Siregar, Iskandar Z. and Steinebach, Stefanie and Tjoa, Aiyen and Tscharntke, Teja and Wick, Barbara and Wiegand, Kerstin and Kreft, Holger and Scheu, Stefan},
  title    = {{Ecological and socio-economic functions across tropical land use systems after rainforest conversion}},
  journal  = {Philosophical Transactions of the Royal Society B: Biological Sciences},
  year     = {2016},
  volume   = {371},
  number   = {1694},
  pages    = {20150275},
  issn     = {0962-8436},
  url_pdf  = {http://uni-goettingen.de/de/document/download/0bc8efa0c4c9957a00d4712e27447ef9.pdf/Drescher_et_al_2016_RSTB_ecological_socio-economic_functions_after_rainforest_conversion.pdf},
  abstract = {Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and the extraction of natural resources. In Jambi Province, Indonesia, the interdisciplinary EFForTS project focuses on the ecological and socio-economic dimensions of rainforest conversion to jungle rubber agroforests and monoculture plantations of rubber and oil palm. Our data confirm that rainforest transformation and land use intensification lead to substantial losses in biodiversity and related ecosystem functions, such as decreased above- and below-ground carbon stocks. Owing to rapid step-wise transformation from forests to agroforests to monoculture plantations and renewal of each plantation type every few decades, the converted land use systems are continuously dynamic, thus hampering the adaptation of animal and plant communities. On the other hand, agricultural rainforest transformation systems provide increased income and access to education, especially for migrant smallholders. Jungle rubber and rubber monocultures are associated with higher financial land productivity but lower financial labour productivity compared to oil palm, which influences crop choice: smallholders that are labour-scarce would prefer oil palm while land-scarce smallholders would prefer rubber. Collecting long-term data in an interdisciplinary context enables us to provide decision-makers and stakeholders with scientific insights to facilitate the reconciliation between economic interests and ecological sustainability in tropical agricultural landscapes.},
  comment  = {public},
  doi      = {10.1098/rstb.2015.0275},
  isbn     = {0962-8436},
  pmid     = {27114577},
  url      = {http://rstb.royalsocietypublishing.org/lookup/doi/10.1098/rstb.2015.0275},
}

Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and the extraction of natural resources. In Jambi Province, Indonesia, the interdisciplinary EFForTS project focuses on the ecological and socio-economic dimensions of rainforest conversion to jungle rubber agroforests and monoculture plantations of rubber and oil palm. Our data confirm that rainforest transformation and land use intensification lead to substantial losses in biodiversity and related ecosystem functions, such as decreased above- and below-ground carbon stocks. Owing to rapid step-wise transformation from forests to agroforests to monoculture plantations and renewal of each plantation type every few decades, the converted land use systems are continuously dynamic, thus hampering the adaptation of animal and plant communities. On the other hand, agricultural rainforest transformation systems provide increased income and access to education, especially for migrant smallholders. Jungle rubber and rubber monocultures are associated with higher financial land productivity but lower financial labour productivity compared to oil palm, which influences crop choice: smallholders that are labour-scarce would prefer oil palm while land-scarce smallholders would prefer rubber. Collecting long-term data in an interdisciplinary context enables us to provide decision-makers and stakeholders with scientific insights to facilitate the reconciliation between economic interests and ecological sustainability in tropical agricultural landscapes.

@Article{Erfanifard2016,
  author   = {Erfanifard, Yousef and Saborowski, Joachim and Wiegand, Kerstin and Meyer, Katrin M.},
  title    = {{Efficiency of sample-based indices for spatial pattern recognition of wild pistachio (Pistacia atlantica) trees in semi-arid woodlands}},
  journal  = {Journal of Forestry Research},
  year     = {2016},
  volume   = {27},
  number   = {3},
  pages    = {583--594},
  issn     = {19930607},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d9965b15e03ba523b49ea7c3fdfd2b12.pdf/Erfanifard_etal_2015_Efficiency_of_sample-based_indices_for_spatial_pattern_recognition_ForRes_.pdf},
  abstract = {{\textcopyright} 2015, Northeast Forestry University and Springer-Verlag Berlin Heidelberg. The efficiency of sample-based indices proposed to quantify the spatial distribution of trees is influenced by the structure of tree stands, environmental heterogeneity and degree of aggregation. We evaluated 10 commonly used distance-based and 10 density-based indices using two structurally different stands of wild pistachio trees in the Zagros woodlands, Iran, to assess the reliability of each in revealing stand structure in woodlands. All trees were completely stem-mapped in a nearly pure (40 ha) and a mixed (45 ha) stand. First, the inhomogeneous pair correlation function [g(r)] and the Clark–Evans index (CEI) were used as references to reveal the true spatial arrangement of all trees in these stands. The sampled data were then evaluated using the 20 indices. Sampling was undertaken in a grid based on a square lattice using square plots (30 m × 30 m) and nearest neighbor distances at the sample points. The g(r) and CEI statistics showed that the wild pistachio trees were aggregated in both stands, although the degree of aggregation was markedly higher in the pure stand. Three distance- and six density-based indices statistically verified that the wild pistachio trees were aggregated in both stands. The distance-based Hines and Hines statistic (h t ) and the density-based standardised Morisita (I p ), patchiness (IP) and Cassie (C A ) indices revealed aggregation of the trees in the two structurally different stands in the Zagros woodlands and the higher clumping in the pure stand, whereas the other indices were not sensitive enough.},
  comment  = {public},
  doi      = {10.1007/s11676-015-0205-y},
  isbn     = {7144165186},
  keywords = {Density-based indices,Distance-based indices,Pattern recognition,Wild pistachio,Woodland},
}

© 2015, Northeast Forestry University and Springer-Verlag Berlin Heidelberg. The efficiency of sample-based indices proposed to quantify the spatial distribution of trees is influenced by the structure of tree stands, environmental heterogeneity and degree of aggregation. We evaluated 10 commonly used distance-based and 10 density-based indices using two structurally different stands of wild pistachio trees in the Zagros woodlands, Iran, to assess the reliability of each in revealing stand structure in woodlands. All trees were completely stem-mapped in a nearly pure (40 ha) and a mixed (45 ha) stand. First, the inhomogeneous pair correlation function [g(r)] and the Clark–Evans index (CEI) were used as references to reveal the true spatial arrangement of all trees in these stands. The sampled data were then evaluated using the 20 indices. Sampling was undertaken in a grid based on a square lattice using square plots (30 m × 30 m) and nearest neighbor distances at the sample points. The g(r) and CEI statistics showed that the wild pistachio trees were aggregated in both stands, although the degree of aggregation was markedly higher in the pure stand. Three distance- and six density-based indices statistically verified that the wild pistachio trees were aggregated in both stands. The distance-based Hines and Hines statistic (h t ) and the density-based standardised Morisita (I p ), patchiness (IP) and Cassie (C A ) indices revealed aggregation of the trees in the two structurally different stands in the Zagros woodlands and the higher clumping in the pure stand, whereas the other indices were not sensitive enough.

@Article{Getzin2016,
  author   = {Getzin, Stephan and Yizhaq, Hezi and Bell, Bronwyn and Erickson, Todd E. and Postle, Anthony C. and Katra, Itzhak and Tzuk, Omer and Zelnik, Yuval R. and Wiegand, Kerstin and Wiegand, Thorsten and Meron, Ehud},
  title    = {{Discovery of fairy circles in Australia supports self-organization theory}},
  journal  = {Proceedings of the National Academy of Sciences},
  year     = {2016},
  volume   = {113},
  number   = {13},
  pages    = {3551--3556},
  issn     = {0027-8424},
  url_pdf  = {http://uni-goettingen.de/de/document/download/30a084eb0898ed495873f6ae0cc7e157.pdf/Getzin_et_al_2016_PNAS_discovery_of_fairy_circles_in_Australia.pdf},
  abstract = {SignificancePattern-formation theory predicts that vegetation gap patterns, such as the fairy circles of Namibia, emerge through the action of pattern-forming biomass-water feedbacks and that such patterns should be found elsewhere in water-limited systems around the world. We report here the exciting discovery of fairy-circle patterns in the remote outback of Australia. Using fieldwork, remote sensing, spatial pattern analysis, mathematical modeling, and pattern-formation theory we show that the Australian gap patterns share with their Namibian counterparts the same characteristics but are driven by a different biomass-water feedback. These observations are in line with a central universality principle of pattern-formation theory and support the applicability of this theory to wider contexts of spatial self-organization in ecology. Vegetation gap patterns in arid grasslands, such as the "fairy circles" of Namibia, are one of natures greatest mysteries and subject to a lively debate on their origin. They are characterized by small-scale hexagonal ordering of circular bare-soil gaps that persists uniformly in the landscape scale to form a homogeneous distribution. Pattern-formation theory predicts that such highly ordered gap patterns should be found also in other water-limited systems across the globe, even if the mechanisms of their formation are different. Here we report that so far unknown fairy circles with the same spatial structure exist 10,000 km away from Namibia in the remote outback of Australia. Combining fieldwork, remote sensing, spatial pattern analysis, and process-based mathematical modeling, we demonstrate that these patterns emerge by self-organization, with no correlation with termite activity; the driving mechanism is a positive biomass-water feedback associated with water runoff and biomass-dependent infiltration rates. The remarkable match between the patterns of Australian and Namibian fairy circles and model results indicate that both patterns emerge from a nonuniform stationary instability, supporting a central universality principle of pattern-formation theory. Applied to the context of dryland vegetation, this principle predicts that different systems that go through the same instability type will show similar vegetation patterns even if the feedback mechanisms and resulting soil-water distributions are different, as we indeed found by comparing the Australian and the Namibian fairy-circle ecosystems. These results suggest that biomass-water feedbacks and resultant vegetation gap patterns are likely more common in remote drylands than is currently known.},
  comment  = {public},
  doi      = {10.1073/pnas.1522130113},
  pmid     = {26976567},
  url      = {http://www.pnas.org/lookup/doi/10.1073/pnas.1522130113},
}

SignificancePattern-formation theory predicts that vegetation gap patterns, such as the fairy circles of Namibia, emerge through the action of pattern-forming biomass-water feedbacks and that such patterns should be found elsewhere in water-limited systems around the world. We report here the exciting discovery of fairy-circle patterns in the remote outback of Australia. Using fieldwork, remote sensing, spatial pattern analysis, mathematical modeling, and pattern-formation theory we show that the Australian gap patterns share with their Namibian counterparts the same characteristics but are driven by a different biomass-water feedback. These observations are in line with a central universality principle of pattern-formation theory and support the applicability of this theory to wider contexts of spatial self-organization in ecology. Vegetation gap patterns in arid grasslands, such as the "fairy circles" of Namibia, are one of natures greatest mysteries and subject to a lively debate on their origin. They are characterized by small-scale hexagonal ordering of circular bare-soil gaps that persists uniformly in the landscape scale to form a homogeneous distribution. Pattern-formation theory predicts that such highly ordered gap patterns should be found also in other water-limited systems across the globe, even if the mechanisms of their formation are different. Here we report that so far unknown fairy circles with the same spatial structure exist 10,000 km away from Namibia in the remote outback of Australia. Combining fieldwork, remote sensing, spatial pattern analysis, and process-based mathematical modeling, we demonstrate that these patterns emerge by self-organization, with no correlation with termite activity; the driving mechanism is a positive biomass-water feedback associated with water runoff and biomass-dependent infiltration rates. The remarkable match between the patterns of Australian and Namibian fairy circles and model results indicate that both patterns emerge from a nonuniform stationary instability, supporting a central universality principle of pattern-formation theory. Applied to the context of dryland vegetation, this principle predicts that different systems that go through the same instability type will show similar vegetation patterns even if the feedback mechanisms and resulting soil-water distributions are different, as we indeed found by comparing the Australian and the Namibian fairy-circle ecosystems. These results suggest that biomass-water feedbacks and resultant vegetation gap patterns are likely more common in remote drylands than is currently known.

@Article{Getzin2016a,
  author    = {Getzin, Stephan and Yizhaq, Hezi and Bell, Bronwyn and Erickson, Todd E and Postle, Anthony C and Katra, Itzhak and Tzuk, Omer and Zelnik, Yuval R and Wiegand, Kerstin and Wiegand, Thorsten and Meron, Ehud},
  title     = {{Reply to Walsh et al.: Hexagonal patterns of Australian fairy circles develop without correlation to termitaria.}},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  year      = {2016},
  volume    = {113},
  number    = {37},
  pages     = {E5368--9},
  issn      = {1091-6490},
  url_pdf   = {http://uni-goettingen.de/de/document/download/f7a049460304609f33f93fa93598c6b4.pdf/Getzin_et_al_2016_PNAS_reply_to_Walsh_Australian_fairy_circles.pdf},
  comment   = {public},
  doi       = {10.1073/pnas.1611877113},
  pmid      = {27588904},
  publisher = {National Academy of Sciences},
  url       = {http://www.ncbi.nlm.nih.gov/pubmed/27588904 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC5027457},
}

@Article{Gossner2016,
  author   = {Gossner, Martin M. and Lewinsohn, Thomas M. and Kahl, Tiemo and Grassein, Fabrice and Boch, Steffen and Prati, Daniel and Birkhofer, Klaus and Renner, Swen C. and Sikorski, Johannes and Wubet, Tesfaye and Arndt, Hartmut and Baumgartner, Vanessa and Blaser, Stefan and Bl{\"{u}}thgen, Nico and B{\"{o}}rschig, Carmen and Buscot, Francois and DIek{\"{o}}tter, Tim and Jorge, Leonardo R{\'{e}} and Jung, Kirsten and Keyel, Alexander C. and Klein, Alexandra Maria and Klemmer, Sandra and Krauss, Jochen and Lange, Markus and M{\"{u}}ller, J{\"{o}}rg and Overmann, J{\"{o}}rg and Pa{\v{s}}ali, Esther and Penone, Caterina and Perovic, David J. and Purschke, Oliver and Schall, Peter and Socher, Stephanie A. and Sonnemann, Ilja and Tschapka, Marco and Tscharntke, Teja and T{\"{u}}rke, Manfred and Venter, Paul Christiaan and Weiner, Christiane N. and Werner, Michael and Wolters, Volkmar and Wurst, Susanne and Westphal, Catrin and Fischer, Markus and Weisser, Wolfgang W. and Allan, Eric},
  title    = {{Land-use intensification causes multitrophic homogenization of grassland communities}},
  journal  = {Nature},
  year     = {2016},
  volume   = {540},
  number   = {7632},
  pages    = {266--269},
  issn     = {14764687},
  url_pdf  = {http://uni-goettingen.de/de/document/download/bd5bf89a4db42bf100e61cd1ba7484c7.zip/Gossner_et_al_2016_NATURE_land-use_intensification_multitrophic_homogenization_grassland_communities.zip},
  abstract = {Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in $\beta$-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local ($\alpha$)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing $\beta$-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in $\alpha$-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on $\beta$-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in $\beta$-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local $\alpha$-diversity in aboveground groups, whereas the $\alpha$-diversity increased in belowground groups. Correlations between the $\beta$-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.},
  comment  = {public},
  doi      = {10.1038/nature20575},
  isbn     = {1476-4687},
  pmid     = {27919075},
}

Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in $β$-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local ($α$)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing $β$-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in $α$-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on $β$-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in $β$-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local $α$-diversity in aboveground groups, whereas the $α$-diversity increased in belowground groups. Correlations between the $β$-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

@Article{Harmse2016,
  author   = {Harmse, Christiaan J. and Kellner, Klaus and Dreber, Niels},
  title    = {{Restoring productive rangelands: A comparative assessment of selective and non-selective chemical bush control in a semi-arid Kalahari savanna}},
  journal  = {Journal of Arid Environments},
  year     = {2016},
  volume   = {135},
  pages    = {39--49},
  issn     = {1095922X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/8f35b8ac8e4cf34e04d5c064f44edba7.pdf/Harmse_et_al_2016_JOURNAL_ARID_ENVIRONMENTS_restoring_productive_rangelands_chemical_bush_control.pdf},
  abstract = {The chemical control of thickened woody savanna layers is a common practice applied in southern Africa to release the grass layer from competitive pressure and restore the economic viability of rangelands. We comparatively assessed the composition, density and production of the grass layer in relation to the woody vegetation structure following the selective control of increaser woody species (SC) and non-selective control of the whole woody layer (NSC) in a semi-arid Kalahari savanna. Vegetation states associated with bush-thickening preventative range management (PRM) served as a benchmark. The SC treatment created a well-structured woody layer and favored the development of a grassy savanna state with abundant valuable forage grasses, as found under PRM. Despite a high dry matter production and density of grasses, NSC rangelands appeared to be unstable. Results indicate that NSC facilitates the development of a dense woody recruitment layer that counteracts a favorable grass layer development. We conclude that SC is conditionally more effective in restoring a relatively stable and desirable bush-grass ratio for commercial farming purposes, whereas NSC increases the risk of vegetation transition back to a bush-dominated state. While essential in combination with both treatments, NSC demands an increased effort of follow-up control of woody recruits.},
  comment  = {public},
  doi      = {10.1016/j.jaridenv.2016.08.009},
  keywords = {Acacia mellifera,Arboricide,Bush encroachment,Rangeland management,Restoration,Tree-grass interactions},
}

The chemical control of thickened woody savanna layers is a common practice applied in southern Africa to release the grass layer from competitive pressure and restore the economic viability of rangelands. We comparatively assessed the composition, density and production of the grass layer in relation to the woody vegetation structure following the selective control of increaser woody species (SC) and non-selective control of the whole woody layer (NSC) in a semi-arid Kalahari savanna. Vegetation states associated with bush-thickening preventative range management (PRM) served as a benchmark. The SC treatment created a well-structured woody layer and favored the development of a grassy savanna state with abundant valuable forage grasses, as found under PRM. Despite a high dry matter production and density of grasses, NSC rangelands appeared to be unstable. Results indicate that NSC facilitates the development of a dense woody recruitment layer that counteracts a favorable grass layer development. We conclude that SC is conditionally more effective in restoring a relatively stable and desirable bush-grass ratio for commercial farming purposes, whereas NSC increases the risk of vegetation transition back to a bush-dominated state. While essential in combination with both treatments, NSC demands an increased effort of follow-up control of woody recruits.

@Article{Hol2016,
  author   = {Hol, W. H. G. and Raaijmakers, Ciska E. and Mons, Ilse and Meyer, Katrin M. and van Dam, Nicole M.},
  title    = {{Root-Lesion Nematodes Suppress Cabbage Aphid Population Development by Reducing Aphid Daily Reproduction}},
  journal  = {Frontiers in Plant Science},
  year     = {2016},
  volume   = {7},
  issn     = {1664-462X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d30043dd5c8a3ada1a04b7adec062fcb.pdf/Hol_etal_2016_Root-Lesion-Nematodes-Suppress-Cabbage-Aphid-Population-Development-by-Reducing-Aphid-Daily-Reproduction.pdf},
  abstract = {{\textcopyright} 2016 Hol, Raaijmakers, Mons, Meyer and van Dam. Empirical studies have shown that belowground feeding herbivores can affect the performance of aboveground herbivores in different ways. Often the critical life-history parameters underlying the observed performance effects remain unexplored. In order to better understand the cause for the observed effects on aboveground herbivores, these ecological mechanisms must be better understood. In this study we combined empirical experiments with a modeling approach to analyze the effect of two root feeding endoparasitic nematodes with different feeding strategies on the population growth of the aboveground feeding specialist aphid Brevicoryne brassicae on Brassica nigra. The aim was to test whether emerging differences in life history characteristics (days until reproduction, daily reproduction) would be sufficient to explain observed differences in aphid population development on plants with and without two species of nematodes. Aphid numbers were lower on plants with Pratylenchus penetrans in comparison to aphid numbers on plants with Meloidogyne spp. A dedicated experiment showed that aphid daily reproduction was lower on plants with P. penetrans (3.08 offspring female–1 day–1) in comparison to both uninfested plants and plants with Meloidogyne spp. (3.50 offspring female–1 day–1). The species-specific reduction of aphid reproduction appeared independent of changes in amino acids, soluble sugars or the glucosinolate sinigrin in the phloem. An individual-based model revealed that relatively small differences in reproduction rate per female were sufficient to yield a similar difference in aphid populations as was found in the empirical experiments.},
  comment  = {public},
  doi      = {10.3389/fpls.2016.00111},
  isbn     = {1664-462X},
  url      = {http://journal.frontiersin.org/Article/10.3389/fpls.2016.00111/abstract},
}

© 2016 Hol, Raaijmakers, Mons, Meyer and van Dam. Empirical studies have shown that belowground feeding herbivores can affect the performance of aboveground herbivores in different ways. Often the critical life-history parameters underlying the observed performance effects remain unexplored. In order to better understand the cause for the observed effects on aboveground herbivores, these ecological mechanisms must be better understood. In this study we combined empirical experiments with a modeling approach to analyze the effect of two root feeding endoparasitic nematodes with different feeding strategies on the population growth of the aboveground feeding specialist aphid Brevicoryne brassicae on Brassica nigra. The aim was to test whether emerging differences in life history characteristics (days until reproduction, daily reproduction) would be sufficient to explain observed differences in aphid population development on plants with and without two species of nematodes. Aphid numbers were lower on plants with Pratylenchus penetrans in comparison to aphid numbers on plants with Meloidogyne spp. A dedicated experiment showed that aphid daily reproduction was lower on plants with P. penetrans (3.08 offspring female–1 day–1) in comparison to both uninfested plants and plants with Meloidogyne spp. (3.50 offspring female–1 day–1). The species-specific reduction of aphid reproduction appeared independent of changes in amino acids, soluble sugars or the glucosinolate sinigrin in the phloem. An individual-based model revealed that relatively small differences in reproduction rate per female were sufficient to yield a similar difference in aphid populations as was found in the empirical experiments.

@Article{Keyel2016,
  author        = {Keyel, Alexander C. and Gerstenlauer, Jakob L.K. and Wiegand, Kerstin},
  title         = {{SpatialDemography: a spatially explicit, stage-structured, metacommunity model}},
  journal       = {Ecography},
  year          = {2016},
  volume        = {39},
  number        = {11},
  pages         = {1129--1137},
  issn          = {16000587},
  url_pdf       = {http://uni-goettingen.de/de/document/download/4e9cacb3737512ab04a5db17e859179b.pdf/Keyel_et_al_2016_ECOGRAPHY_spatialdemography_metacommunity_model.pdf},
  abstract      = {1. The responses of species and populations to changes in the environment (e.g., changes in climate and land use) are often complex and difficult to predict.2. We have created the SpatialDemography model (R package: spatialdemography). The model is a spatially explicit, stage-structured, matrix-based metacommunity model, with the potential for modeling species' and populations' potential responses to environmental heterogeneity and change.3. The SpatialDemography model assumes a cellular landscape populated by organisms with four life stages: a mobile dispersing stage, two sessile non-reproductive stages, and a reproductive adult stage. Individuals are assumed to originate at the center of a given cell and disperse according to a specified dispersal kernel (e.g., log-normal). All adult individuals are capable of producing offspring. The model approach and framework are described in the context of a hypothetical example with multiple competing species in a four cell landscape. In this example simulation, both spatial location and species interactions were important for understanding population dynamics.4. SpatialDemography can be applied to questions where an understanding of transient and long-term demographic responses to spatiotemporal changes is desired. It is primarily applicable to metapopulations and metacommunities of organisms with early dispersal and sessile adults (i.e. modular organisms such as plants and some marine organisms). SpatialDemography differs from other population models in that it is spatially explicit, can incorporate biotic interactions, and is implemented in R.This article is protected by copyright. All rights reserved.},
  archiveprefix = {arXiv},
  arxivid       = {10.1111/ecog.02097},
  comment       = {public},
  doi           = {10.1111/ecog.02295},
  eprint        = {ecog.02097},
  isbn          = {6503251521},
  primaryclass  = {10.1111},
}

1. The responses of species and populations to changes in the environment (e.g., changes in climate and land use) are often complex and difficult to predict.2. We have created the SpatialDemography model (R package: spatialdemography). The model is a spatially explicit, stage-structured, matrix-based metacommunity model, with the potential for modeling species' and populations' potential responses to environmental heterogeneity and change.3. The SpatialDemography model assumes a cellular landscape populated by organisms with four life stages: a mobile dispersing stage, two sessile non-reproductive stages, and a reproductive adult stage. Individuals are assumed to originate at the center of a given cell and disperse according to a specified dispersal kernel (e.g., log-normal). All adult individuals are capable of producing offspring. The model approach and framework are described in the context of a hypothetical example with multiple competing species in a four cell landscape. In this example simulation, both spatial location and species interactions were important for understanding population dynamics.4. SpatialDemography can be applied to questions where an understanding of transient and long-term demographic responses to spatiotemporal changes is desired. It is primarily applicable to metapopulations and metacommunities of organisms with early dispersal and sessile adults (i.e. modular organisms such as plants and some marine organisms). SpatialDemography differs from other population models in that it is spatially explicit, can incorporate biotic interactions, and is implemented in R.This article is protected by copyright. All rights reserved.

@Article{Keyel2016a,
  author   = {Keyel, Alexander C. and Wiegand, Kerstin},
  title    = {{Validating the use of unique trait combinations for measuring multivariate functional richness}},
  journal  = {Methods in Ecology and Evolution},
  year     = {2016},
  volume   = {7},
  number   = {8},
  pages    = {929--936},
  issn     = {2041210X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/98d59c57b5b9bdc8cfd7d4f1c2f1ce46.pdf/Keyel_Wiegand_2016_METHODS_ECOLOGY_EVOLUTION_validating_unique_trait_combinations_measuring_multivariate_functional_richness.pdf},
  abstract = {1. Quantifying functional trait diversity has provided important new insights for understanding ecosystem processes and functioning. Functional diversity is often partitioned into three components, richness, evenness, and divergence. Currently, a convex hull is used as a measure of multivariate richness, but this approach has some serious limitations. 2. Consequently, we propose using the number of Unique Trait Combinations (UTC) as an approach to measure the filled trait space (the hypervolume containing all possible trait combinations), and propose a new index, sUTC as the amount of filled trait space divided by the trait space range. Like convex hull approaches, UTC can be partitioned into alpha and beta components when used across sites, and the beta component can be further partitioned into turnover and nestedness components. Unlike convex hull approaches, Accepted Article UTC can be used more intuitively with existing diversity measures as it can be used in conjunction with abundance information. We present the concepts these indices are based on and give examples of their use. The new index, sUTC, is compared to the existing indices on the basis of criteria specified in the literature and one novel criterion. We test and evaluate the approach using simulated data and field data. 3. We found that the UTC approach provided a more accurate assessment of functional richness than did the existing indices. 4. The UTC approach is a multivariate approach to measuring functional richness that can accommodate continuous and categorical traits and can account for holes in the trait space.},
  comment  = {public},
  doi      = {10.1111/2041-210X.12558},
  isbn     = {2041210X},
  keywords = {FRicindex,beta diversity,convex hull,coral reef fish,diversity partitioning,functional trait,functional unit,multidimensional,niche,richness},
}

1. Quantifying functional trait diversity has provided important new insights for understanding ecosystem processes and functioning. Functional diversity is often partitioned into three components, richness, evenness, and divergence. Currently, a convex hull is used as a measure of multivariate richness, but this approach has some serious limitations. 2. Consequently, we propose using the number of Unique Trait Combinations (UTC) as an approach to measure the filled trait space (the hypervolume containing all possible trait combinations), and propose a new index, sUTC as the amount of filled trait space divided by the trait space range. Like convex hull approaches, UTC can be partitioned into alpha and beta components when used across sites, and the beta component can be further partitioned into turnover and nestedness components. Unlike convex hull approaches, Accepted Article UTC can be used more intuitively with existing diversity measures as it can be used in conjunction with abundance information. We present the concepts these indices are based on and give examples of their use. The new index, sUTC, is compared to the existing indices on the basis of criteria specified in the literature and one novel criterion. We test and evaluate the approach using simulated data and field data. 3. We found that the UTC approach provided a more accurate assessment of functional richness than did the existing indices. 4. The UTC approach is a multivariate approach to measuring functional richness that can accommodate continuous and categorical traits and can account for holes in the trait space.

@Misc{Klasen2016,
  author    = {Klasen, Stephan and Meyer, Katrin M. and Dislich, Claudia and Euler, Michael and Faust, Heiko and Gatto, Marcel and Hettig, Elisabeth and Melati, Dian N. and Jaya, I. Nengah Surati and Otten, Fenna and P{\'{e}}rez-Cruzado, C{\'{e}}sar and Steinebach, Stefanie and Tarigan, Suria and Wiegand, Kerstin},
  title     = {{Economic and ecological trade-offs of agricultural specialization at different spatial scales}},
  year      = {2016},
  url_pdf   = {http://uni-goettingen.de/de/document/download/08f2c7a4cbc05964fd4814b6b0b6b9d0.pdf/Klasen_et_al_2016_Ecological_Economics_Economic_and_ecological_trade-offs_of_agricultural_specialization_at_different_spatial_scales.pdf},
  abstract  = {Specialization in agricultural systems can lead to trade-offs between economic gains and ecosystem functions. We suggest and explore a conceptual framework in which economic gains can be maximized when production activities are specialized at increasingly broader scales (from the household to the village, region or above), particularly when markets for outputs and inputs function well. Conversely, more specialization likely reduces biodiversity and significantly limits ecosystem functions. When agricultural specialization increases and moves to broader scales as a result of improved infrastructure and markets or other drivers, ecosystem functions can also be endangered at broader spatial scales. Policies to improve agricultural incomes may influence the level of specialization at different scales and thus affect the severity of the trade-offs. This paper takes Jambi province in Indonesia, a current hotspot of rubber and oil palm monoculture, as a case study to illustrate these issues. We empirically show that the level of specialization differs across scales with higher specialization at household and village levels and higher diversification towards the province level. We discuss ways to resolve trade-offs between economic gains and ecological costs, including landscape design, targeted policies, and adoption of long-term perspectives.},
  booktitle = {Ecological Economics},
  comment   = {public},
  doi       = {10.1016/j.ecolecon.2016.01.001},
  isbn      = {0921-8009},
  issn      = {09218009},
  keywords  = {Economies of Scale,Ecosystem Services,Indonesia,Monoculture,Oil Palm,Rubber},
  pages     = {111--120},
  volume    = {122},
}

Specialization in agricultural systems can lead to trade-offs between economic gains and ecosystem functions. We suggest and explore a conceptual framework in which economic gains can be maximized when production activities are specialized at increasingly broader scales (from the household to the village, region or above), particularly when markets for outputs and inputs function well. Conversely, more specialization likely reduces biodiversity and significantly limits ecosystem functions. When agricultural specialization increases and moves to broader scales as a result of improved infrastructure and markets or other drivers, ecosystem functions can also be endangered at broader spatial scales. Policies to improve agricultural incomes may influence the level of specialization at different scales and thus affect the severity of the trade-offs. This paper takes Jambi province in Indonesia, a current hotspot of rubber and oil palm monoculture, as a case study to illustrate these issues. We empirically show that the level of specialization differs across scales with higher specialization at household and village levels and higher diversification towards the province level. We discuss ways to resolve trade-offs between economic gains and ecological costs, including landscape design, targeted policies, and adoption of long-term perspectives.

@Article{Merten2016,
  author   = {Merten, Jennifer and R{\"{o}}ll, Alexander and Guillaume, Thomas and Meijide, Ana and Tarigan, Suria and Agusta, Herdhata and Dislich, Claudia and Dittrich, Christoph and Faust, Heiko and Gunawan, Dodo and Hein, Jonas and Hendrayanto, A. and Knohl, Alexander and Kuzyakov, Yakov and Wiegand, Kerstin and H{\"{o}}lscher, Dirk},
  title    = {{Water scarcity and oil palm expansion: Social views and environmental processes}},
  journal  = {Ecology and Society},
  year     = {2016},
  volume   = {21},
  number   = {2},
  issn     = {17083087},
  url_pdf  = {http://uni-goettingen.de/de/document/download/34d4b7c5208d04689b6c82a9909b2a0b.pdf/Merten_et_al_2016_ECOLOGY_SOCIETY_water_scarcity_oil_palm_expansion.pdf},
  abstract = {{\textcopyright} 2016 by the author(s).Conversions of natural ecosystems, e.g., from rain forests to managed plantations, result in significant changes in the hydrological cycle including periodic water scarcity. In Indonesia, large areas of forest were lost and extensive oil palm plantations were established over the last decades. We conducted a combined social and environmental study in a region of recent land-use change, the Jambi Province on Sumatra. The objective was to derive complementary lines of arguments to provide balanced insights into environmental perceptions and eco-hydrological processes accompanying land-use change. Interviews with villagers highlighted concerns regarding decreasing water levels in wells during dry periods and increasing fluctuations in stream flow between rainy and dry periods. Periodic water scarcity was found to severely impact livelihoods, which increased social polarization. Sap flux measurements on forest trees and oil palms indicate that oil palm plantations use as much water as forests for transpiration. Eddy covariance analyses of evapotranspiration over oil palm point to substantial additional sources of evaporation in oil palm plantations such as the soil and epiphytes. Stream base flow from a catchment dominated by oil palms was lower than from a catchment dominated by rubber plantations; both showed high peaks after rainfall. An estimate of erosion indicated approximately 30 cm of topsoil loss after forest conversion to both oil palm and rubber plantations. Analyses of climatic variables over the last 20 years and of a standardized precipitation evapotranspiration index for the last century suggested that droughts are recurrent in the area, but have not increased in frequency or intensity. Consequently, we assume that conversions of rain forest ecosystems to oil palm plantations lead to a redistribution of precipitated water by runoff, which leads to the reported periodic water scarcity. Our combined social and environmental approach points to significant and thus far neglected eco-hydrological consequences of oil palm expansion.},
  comment  = {public},
  doi      = {10.5751/ES-08214-210205},
  isbn     = {1708-3087},
  keywords = {Eco-hydrology,Environmental perception,Erosion,Evapotranspiration,Forest,Land-use change,Runoff,Rural water supply,Streamflow,Transpiration},
}

© 2016 by the author(s).Conversions of natural ecosystems, e.g., from rain forests to managed plantations, result in significant changes in the hydrological cycle including periodic water scarcity. In Indonesia, large areas of forest were lost and extensive oil palm plantations were established over the last decades. We conducted a combined social and environmental study in a region of recent land-use change, the Jambi Province on Sumatra. The objective was to derive complementary lines of arguments to provide balanced insights into environmental perceptions and eco-hydrological processes accompanying land-use change. Interviews with villagers highlighted concerns regarding decreasing water levels in wells during dry periods and increasing fluctuations in stream flow between rainy and dry periods. Periodic water scarcity was found to severely impact livelihoods, which increased social polarization. Sap flux measurements on forest trees and oil palms indicate that oil palm plantations use as much water as forests for transpiration. Eddy covariance analyses of evapotranspiration over oil palm point to substantial additional sources of evaporation in oil palm plantations such as the soil and epiphytes. Stream base flow from a catchment dominated by oil palms was lower than from a catchment dominated by rubber plantations; both showed high peaks after rainfall. An estimate of erosion indicated approximately 30 cm of topsoil loss after forest conversion to both oil palm and rubber plantations. Analyses of climatic variables over the last 20 years and of a standardized precipitation evapotranspiration index for the last century suggested that droughts are recurrent in the area, but have not increased in frequency or intensity. Consequently, we assume that conversions of rain forest ecosystems to oil palm plantations lead to a redistribution of precipitated water by runoff, which leads to the reported periodic water scarcity. Our combined social and environmental approach points to significant and thus far neglected eco-hydrological consequences of oil palm expansion.

@Article{Nguyen2016,
  author   = {Nguyen, Hong Hai and Uria-Diez, Jaime and Wiegand, Kerstin},
  title    = {{Spatial distribution and association patterns in a tropical evergreen broad-leaved forest of north-central Vietnam}},
  journal  = {Journal of Vegetation Science},
  year     = {2016},
  volume   = {27},
  number   = {2},
  pages    = {318--327},
  issn     = {16541103},
  url_pdf  = {http://uni-goettingen.de/de/document/download/202cc948069e28c2a213996cb0a01df3.pdf/JForestryResearch_2014.pdf},
  abstract = {$\backslash$n$\backslash$nQuestions$\backslash$n$\backslash$nWhat are the prevailing types of intraspecific spatial distributions and interspecific association patterns at species and life stage levels of trees in a tropical rain forest? Which ecological processes could structure these patterns? Possible processes include dispersal limitation, self-thinning, facilitation and competition between species and life stages.$\backslash$n$\backslash$n$\backslash$nLocation$\backslash$n$\backslash$nA tropical broad-leaved forest in north-central Vietnam.$\backslash$n$\backslash$n$\backslash$nMethods$\backslash$n$\backslash$nWe used univariate and bivariate pair-correlation functions to investigate the spatial distribution and association patterns of 18 abundant tree species. To disentangle first- and second-order effects, we used a scale separation approach with the heterogeneous Poisson process as null model.$\backslash$n$\backslash$n$\backslash$nResults$\backslash$n$\backslash$n(1) Sixteen of 18 species had aggregated patterns at various scales and regardless of their abundance. (2) Significant and aggregated patterns were found in 64{\%} of all specific life stages. (3) At scales up to 15 m, 12.4{\%} species pairs showed significant associations, among that 71{\%} were spatial attractions, 5{\%} were spatial repulsions and 24{\%} were non-essential interactions. (4) In different life stage associations, attractions (81{\%}) predominated over repulsions (19{\%}) at small scales of up to 15 m.$\backslash$n$\backslash$n$\backslash$nConclusions$\backslash$n$\backslash$nOur findings provide evidence that dispersal limitation may regulate the spatial patterns of tree species. Moreover, positive spatial associations between tree species and life stages suggest the presence of species herd protection and/or facilitation in this forest stand, while the persistence of intraspecific aggregation through life stages suggests a very late onset or even absence of self-thinning. Habitat heterogeneity plays an important role for species distribution patterns, and the spatial segregation occurs at a scale around 15 m in this forest.$\backslash$n},
  comment  = {public},
  doi      = {10.1111/jvs.12361},
  isbn     = {1654-1103},
  keywords = {Dispersal limitation,Neutral theory,Pair-correlation function,Point pattern analysis,Self-thinning,Spatial pattern,Species association,Species herd protection,Tropical evergreen forest,Vietnam},
}

$\$n$\$nQuestions$\$n$\$nWhat are the prevailing types of intraspecific spatial distributions and interspecific association patterns at species and life stage levels of trees in a tropical rain forest? Which ecological processes could structure these patterns? Possible processes include dispersal limitation, self-thinning, facilitation and competition between species and life stages.$\$n$\$n$\$nLocation$\$n$\$nA tropical broad-leaved forest in north-central Vietnam.$\$n$\$n$\$nMethods$\$n$\$nWe used univariate and bivariate pair-correlation functions to investigate the spatial distribution and association patterns of 18 abundant tree species. To disentangle first- and second-order effects, we used a scale separation approach with the heterogeneous Poisson process as null model.$\$n$\$n$\$nResults$\$n$\$n(1) Sixteen of 18 species had aggregated patterns at various scales and regardless of their abundance. (2) Significant and aggregated patterns were found in 64% of all specific life stages. (3) At scales up to 15 m, 12.4% species pairs showed significant associations, among that 71% were spatial attractions, 5% were spatial repulsions and 24% were non-essential interactions. (4) In different life stage associations, attractions (81%) predominated over repulsions (19%) at small scales of up to 15 m.$\$n$\$n$\$nConclusions$\$n$\$nOur findings provide evidence that dispersal limitation may regulate the spatial patterns of tree species. Moreover, positive spatial associations between tree species and life stages suggest the presence of species herd protection and/or facilitation in this forest stand, while the persistence of intraspecific aggregation through life stages suggests a very late onset or even absence of self-thinning. Habitat heterogeneity plays an important role for species distribution patterns, and the spatial segregation occurs at a scale around 15 m in this forest.$\$n

@Article{Nurdiansyah2016,
  author   = {Nurdiansyah, Fuad and Denmead, Lisa H. and Clough, Yann and Wiegand, Kerstin and Tscharntke, Teja},
  title    = {{Biological control in Indonesian oil palm potentially enhanced by landscape context}},
  journal  = {Agriculture, Ecosystems and Environment},
  year     = {2016},
  volume   = {232},
  pages    = {141--149},
  issn     = {01678809},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2f5c4a9f402de60f0b5fe40d49140507.pdf/Nurdiansyah_2016_DISS_local_landscape_management_biological_pest_control_in_oil_palm_plantations.pdf},
  abstract = {Oil palm plantation expansion is occurring at a rapid pace. However, substantial yield losses from pest attacks are becoming major threats to the oil palm industry, while the potential role of conservation biological control, a sustainable and environmentally friendly solution for pest control, is still largely unknown. The type of vegetation surrounding oil palm plantations is likely to influence pest predation, and we tested this in Indonesia (Sumatra), the world's largest palm oil producer. We studied six different vegetation types adjacent to oil palm plantations: another oil palm plantation (control), weedy oil palm, weedy rubber, scrub, jungle rubber, and secondary forest. Each border type was replicated eight times. We quantified predation rates and predator occurrences using dummy caterpillars and mealworms 20 m inside of the adjacent vegetation (OUT 20) as well as 20 m (IN 20) and 50 (IN 50) m inside the oil palm plantation. Ants and bush crickets were the most prominent predators in the plantations, whereas birds, bats, monkeys, beetles, and molluscs played a minor role. Mean percentage of ant and cricket predation rate in control border OUT 20 were 16.39{\%} and 7.16{\%} respectively, IN 20 were 16.03{\%} and 6.1{\%}, and IN 50 were 14.47{\%} and 7.48{\%}, while for other borders other than control, mean percentages OUT 20 m were 28.90{\%} and 12.26{\%} respectively, IN 20 m were 26.61{\%} and 12.40{\%}, and IN 50 m were 22.93{\%} and 10.58{\%}. Predation rates were ∼70{\%} higher in non-oil palm habitat, indicating the need for improved vegetation diversification inside plantations. Overall predation rates in oil palm decreased slightly but significantly with distance to the border. Our results suggest that maintaining non-oil palm vegetation in the areas adjacent to plantations and promoting weedy strips within the plantations are potentially effective management tools for conserving and developing biological control in oil palm in the future.},
  comment  = {public},
  doi      = {10.1016/j.agee.2016.08.006},
  isbn     = {0167-8809},
  keywords = {Ant,Biological control,Conservation,Pest management,Predation,Predatory crickets},
}

Oil palm plantation expansion is occurring at a rapid pace. However, substantial yield losses from pest attacks are becoming major threats to the oil palm industry, while the potential role of conservation biological control, a sustainable and environmentally friendly solution for pest control, is still largely unknown. The type of vegetation surrounding oil palm plantations is likely to influence pest predation, and we tested this in Indonesia (Sumatra), the world's largest palm oil producer. We studied six different vegetation types adjacent to oil palm plantations: another oil palm plantation (control), weedy oil palm, weedy rubber, scrub, jungle rubber, and secondary forest. Each border type was replicated eight times. We quantified predation rates and predator occurrences using dummy caterpillars and mealworms 20 m inside of the adjacent vegetation (OUT 20) as well as 20 m (IN 20) and 50 (IN 50) m inside the oil palm plantation. Ants and bush crickets were the most prominent predators in the plantations, whereas birds, bats, monkeys, beetles, and molluscs played a minor role. Mean percentage of ant and cricket predation rate in control border OUT 20 were 16.39% and 7.16% respectively, IN 20 were 16.03% and 6.1%, and IN 50 were 14.47% and 7.48%, while for other borders other than control, mean percentages OUT 20 m were 28.90% and 12.26% respectively, IN 20 m were 26.61% and 12.40%, and IN 50 m were 22.93% and 10.58%. Predation rates were ∼70% higher in non-oil palm habitat, indicating the need for improved vegetation diversification inside plantations. Overall predation rates in oil palm decreased slightly but significantly with distance to the border. Our results suggest that maintaining non-oil palm vegetation in the areas adjacent to plantations and promoting weedy strips within the plantations are potentially effective management tools for conserving and developing biological control in oil palm in the future.

@Article{Schoneberg2016,
  author  = {Schoneberg, S. and Nothdurft, A. and Nuske, Robert S. and Ackermann, J. and Nagel, J{\"{u}}rgen and Saborowski, Joachim},
  title   = {{Comparison of stand volume predictions based on airborne laser scanning data versus digital color infrared images}},
  journal = {Allgemeine Forst- und Jagdzeitung},
  year    = {2016},
  volume  = {187},
  pages   = {1--13},
  url_pdf = {http://uni-goettingen.de/de/document/download/35eb5ad7e5d486f2c34bd1a140e25613.pdf/Schoneberg_etal_volume_pred_2016_AFJZ.pdf},
  comment = {public},
}

@Article{Singer2016,
  author   = {Singer, Alexander and Johst, Karin and Banitz, Thomas and Fowler, Mike S. and Groeneveld, J{\"{u}}rgen and Guti{\'{e}}rrez, Alvaro G. and Hartig, Florian and Krug, Rainer M. and Liess, Matthias and Matlack, Glenn and Meyer, Katrin M. and Pe'er, Guy and Radchuk, Viktoriia and Voinopol-Sassu, Ana Johanna and Travis, Justin M.J.},
  title    = {{Community dynamics under environmental change: How can next generation mechanistic models improve projections of species distributions?}},
  journal  = {Ecological Modelling},
  year     = {2016},
  volume   = {326},
  pages    = {63--74},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d5e0375403f3f88f730b643228af70ca.pdf/Singer_etal_2016_EcolModel_Community_dynamics_under_environmental_change.pdf},
  abstract = {Environmental change is expected to shift the geographic range of species and communities. To estimate the consequences of these shifts for the functioning and stability of ecosystems, reliable predictions of alterations in species distributions are needed. Projections with correlative species distribution models, which correlate species' distributions to the abiotic environment, have become a standard approach. Criticism of this approach centres around the omission of relevant biotic feedbacks and triggered the search for alternatives. A new generation of mechanistic process-based species distribution models aims at implementing formulations of relevant biotic processes to cover species' life histories, physiology, dispersal abilities, evolution, and both intra- and interspecific interactions. Although this step towards more structural realism is considered important, it remains unclear whether the resulting projections are more reliable. Structural realism has the advantage that geographic range shifting emerges from the interplay of relevant abiotic and biotic processes. Having implemented the relevant response mechanisms, structural realistic models should better tackle the challenge of generating projections of species responses to (non-analogous) environmental change. However, reliable projections of future species ranges demand ecological information that is currently only available for few species. In this opinion paper, we discuss how the discrepancy between demand for structural realism on the one hand and the related knowledge gaps on the other hand affects the reliability of mechanistic species distribution models. We argue that omission of relevant processes potentially impairs projection accuracy (proximity of the mean outcome to the true value), particularly if species range shifts emerge from species and community dynamics. Yet, insufficient knowledge that limits model specification and parameterization, as well as process complexity, increases projection uncertainty (variance in the outcome of simulated model projections). The accuracy-uncertainty-relation reflects current limits to delivering reliable projections of range shifts. We propose a protocol to improve and communicate projection reliability. The protocol combines modelling and empirical research to efficiently fill critical knowledge gaps that currently limit the reliability of species and community projections.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2015.11.007},
  keywords = {Bias,Precision,Prediction,Protocol,SDM,Species interaction,Uncertainty},
}

Environmental change is expected to shift the geographic range of species and communities. To estimate the consequences of these shifts for the functioning and stability of ecosystems, reliable predictions of alterations in species distributions are needed. Projections with correlative species distribution models, which correlate species' distributions to the abiotic environment, have become a standard approach. Criticism of this approach centres around the omission of relevant biotic feedbacks and triggered the search for alternatives. A new generation of mechanistic process-based species distribution models aims at implementing formulations of relevant biotic processes to cover species' life histories, physiology, dispersal abilities, evolution, and both intra- and interspecific interactions. Although this step towards more structural realism is considered important, it remains unclear whether the resulting projections are more reliable. Structural realism has the advantage that geographic range shifting emerges from the interplay of relevant abiotic and biotic processes. Having implemented the relevant response mechanisms, structural realistic models should better tackle the challenge of generating projections of species responses to (non-analogous) environmental change. However, reliable projections of future species ranges demand ecological information that is currently only available for few species. In this opinion paper, we discuss how the discrepancy between demand for structural realism on the one hand and the related knowledge gaps on the other hand affects the reliability of mechanistic species distribution models. We argue that omission of relevant processes potentially impairs projection accuracy (proximity of the mean outcome to the true value), particularly if species range shifts emerge from species and community dynamics. Yet, insufficient knowledge that limits model specification and parameterization, as well as process complexity, increases projection uncertainty (variance in the outcome of simulated model projections). The accuracy-uncertainty-relation reflects current limits to delivering reliable projections of range shifts. We propose a protocol to improve and communicate projection reliability. The protocol combines modelling and empirical research to efficiently fill critical knowledge gaps that currently limit the reliability of species and community projections.

@Article{Tarigan2016,
  author   = {Tarigan, Suria Darma and Sunarti and Wiegand, Kerstin and Dislich, Claudia and Slamet, Bejo and Heinonen, Johannes and Meyer, Katrin},
  journal  = {Sustainability of Water Quality and Ecology},
  title    = {{Mitigation options for improving the ecosystem function of water flow regulation in a watershed with rapid expansion of oil palm plantations}},
  year     = {2016},
  issn     = {22126139},
  pages    = {4--13},
  volume   = {8},
  abstract = {The impact of continuing rainforest transformation on hydrological functioning and other ecosystem functions in South East Asia remains uncertain. The vast majority of the local residents in our study area believe that the expansion of oil palm reduced the flow regulation function of a watershed causing more frequent flooding in the rainy season and water scarcity problems during the dry season. The research aimed to characterize surface runoff as an indicator of water flow regulation and simulate effectiveness of different mitigation options for surface runoff management in a watershed with rapid expansion of oil palm plantations. Our study started with plot experiments to characterize surface runoff used to adapt curve number (CN) values of the different land-use types required for SWAT modeling. Further, we carried out small watershed experiments to adapt the CN values of different mitigation options. The SWAT model performance was in satisfactory agreement with the Nash–Sutcliff efficiency values of 0.88 and 0.82 for calibration and validation, respectively. After successful model calibration and validation, we simulated the effectiveness of the following mitigation options: (a) frond pile management, and (b) frond pile management and silt pit treatment with a density of 20 units per ha. Both options were chosen for their simple construction enhancing their adoption and sustainable application. Frond pile management and the combination of frond pile and silt pit treatment reduced total surface runoff in a watershed scale from 151 mm to 141 mm (10{\%}) and from 151 mm to 109 mm (31{\%}), respectively. The mitigation options which were evaluated in this study were ecologically effective in regulating water flow through reduction of surface runoff. They were also economically viable, because the mitigation options increased the availability of water which can increase oil palm production while the implementation costs are low due to the simple design using frond leaves residues abundantly available onsite. Due to the fulfillment of at least two sustainability pillars, these mitigation options should be adopted as one evaluation criterion in the certification process carried out by Indonesian certification body for sustainable palm oil (ISPO). Further research is still needed to study optimal design criteria for mitigation options including their dimension, density and spatial distribution in a watershed.},
  comment  = {public},
  doi      = {10.1016/j.swaqe.2016.05.001},
  groups   = {Jana:1},
  isbn     = {2212-6139},
  keywords = {Expansion of oil palm plantation,Mitigation option,SWAT model,Surface runoff management},
}

The impact of continuing rainforest transformation on hydrological functioning and other ecosystem functions in South East Asia remains uncertain. The vast majority of the local residents in our study area believe that the expansion of oil palm reduced the flow regulation function of a watershed causing more frequent flooding in the rainy season and water scarcity problems during the dry season. The research aimed to characterize surface runoff as an indicator of water flow regulation and simulate effectiveness of different mitigation options for surface runoff management in a watershed with rapid expansion of oil palm plantations. Our study started with plot experiments to characterize surface runoff used to adapt curve number (CN) values of the different land-use types required for SWAT modeling. Further, we carried out small watershed experiments to adapt the CN values of different mitigation options. The SWAT model performance was in satisfactory agreement with the Nash–Sutcliff efficiency values of 0.88 and 0.82 for calibration and validation, respectively. After successful model calibration and validation, we simulated the effectiveness of the following mitigation options: (a) frond pile management, and (b) frond pile management and silt pit treatment with a density of 20 units per ha. Both options were chosen for their simple construction enhancing their adoption and sustainable application. Frond pile management and the combination of frond pile and silt pit treatment reduced total surface runoff in a watershed scale from 151 mm to 141 mm (10%) and from 151 mm to 109 mm (31%), respectively. The mitigation options which were evaluated in this study were ecologically effective in regulating water flow through reduction of surface runoff. They were also economically viable, because the mitigation options increased the availability of water which can increase oil palm production while the implementation costs are low due to the simple design using frond leaves residues abundantly available onsite. Due to the fulfillment of at least two sustainability pillars, these mitigation options should be adopted as one evaluation criterion in the certification process carried out by Indonesian certification body for sustainable palm oil (ISPO). Further research is still needed to study optimal design criteria for mitigation options including their dimension, density and spatial distribution in a watershed.

@Article{Alexander2015,
  author   = {Alexander, Peter and Rounsevell, Mark D.A. and Dislich, Claudia and Dodson, Jennifer R. and Engstr{\"{o}}m, Kerstin and Moran, Dominic},
  title    = {{Drivers for global agricultural land use change: The nexus of diet, population, yield and bioenergy}},
  journal  = {Global Environmental Change},
  year     = {2015},
  volume   = {35},
  pages    = {138--147},
  issn     = {09593780},
  url_pdf  = {http://uni-goettingen.de/de/document/download/c804435a4188344d8b719f7238ba9709.pdf/Alexander_et_al_2015_Global_Environmental_Change_Drivers_for_global_agricultural_land_use_change_The_nexus_of_diet_population_yield_a.pdf},
  abstract = {The nexus of population growth and changing diets has increased the demands placed on agriculture to supply food for human consumption, animal feed and fuel. Rising incomes lead to dietary changes, from staple crops, towards commodities with greater land requirements, e.g. meat and dairy products. Despite yield improvements partially offsetting increases in demand, agricultural land has still been expanding, causing potential harm to ecosystems, e.g. through deforestation. We use country-level panel data (1961-2011) to allocate the land areas used to produce food for human consumption, waste and biofuels, and to attribute the food production area changes to diet, population and yields drivers. The results show that the production of animal products dominates agricultural land use and land use change over the 50-year period, accounting for 65{\%} of land use change. The rate of extensification of animal production was found to have reduced more recently, principally due to the smaller effect of population growth. The area used for bioenergy was shown to be relatively small, but formed a substantial contribution (36{\%}) to net agricultural expansion in the most recent period. Nevertheless, in comparison to dietary shifts in animal products, bioenergy accounted for less than a tenth of the increase in demand for agricultural land. Population expansion has been the largest driver for agricultural land use change, but dietary changes are a significant and growing driver. China was a notable exception, where dietary transitions dominate food consumption changes, due to rapidly rising incomes. This suggests that future dietary changes will become the principal driver for land use change, pointing to the potential need for demand-side measures to regulate agricultural expansion.},
  comment  = {public},
  doi      = {10.1016/j.gloenvcha.2015.08.011},
  isbn     = {0959-3780},
  keywords = {Dietary patterns,Food security,Land displacement,Land use},
}

The nexus of population growth and changing diets has increased the demands placed on agriculture to supply food for human consumption, animal feed and fuel. Rising incomes lead to dietary changes, from staple crops, towards commodities with greater land requirements, e.g. meat and dairy products. Despite yield improvements partially offsetting increases in demand, agricultural land has still been expanding, causing potential harm to ecosystems, e.g. through deforestation. We use country-level panel data (1961-2011) to allocate the land areas used to produce food for human consumption, waste and biofuels, and to attribute the food production area changes to diet, population and yields drivers. The results show that the production of animal products dominates agricultural land use and land use change over the 50-year period, accounting for 65% of land use change. The rate of extensification of animal production was found to have reduced more recently, principally due to the smaller effect of population growth. The area used for bioenergy was shown to be relatively small, but formed a substantial contribution (36%) to net agricultural expansion in the most recent period. Nevertheless, in comparison to dietary shifts in animal products, bioenergy accounted for less than a tenth of the increase in demand for agricultural land. Population expansion has been the largest driver for agricultural land use change, but dietary changes are a significant and growing driver. China was a notable exception, where dietary transitions dominate food consumption changes, due to rapidly rising incomes. This suggests that future dietary changes will become the principal driver for land use change, pointing to the potential need for demand-side measures to regulate agricultural expansion.

@Article{Badreldin2015,
  author   = {Badreldin, Nasem and Uria-Diez, J. and Mateu, J. and Youssef, Ali and Stal, Cornelis and El-Bana, Magdy and Magdy, Ahmed and Goossens, Rudi},
  title    = {{A spatial pattern analysis of the halophytic species distribution in an arid coastal environment}},
  journal  = {Environmental monitoring and assessment},
  year     = {2015},
  volume   = {187},
  number   = {5},
  pages    = {224},
  issn     = {15732959},
  url_pdf  = {http://uni-goettingen.de/de/document/download/1224631a09aa0d9f9c3019e377c726ad.pdf/Badreldin_et_al_2015_Environ_monit_assess_A_spatial_pattern_analysis_halophytic_species_distribution.pdf},
  abstract = {Obtaining information about the spatial distribution of desert plants is considered as a serious challenge for ecologists and environmental modeling due to the required intensive field work and infrastructures in harsh and remote arid environments. A new method was applied for assessing the spatial distribution of the halophytic species (HS) in an arid coastal environment. This method was based on the object-based image analysis for a high-resolution Google Earth satellite image. The integration of the image processing techniques and field work provided accurate information about the spatial distribution of HS. The extracted objects were based on assumptions that explained the plant-pixel relationship. Three different types of digital image processing techniques were implemented and validated to obtain an accurate HS spatial distribution. A total of 2703 individuals of the HS community were found in the case study, and approximately 82 {\%} were located above an elevation of 2 m. The micro-topography exhibited a significant negative relationship with pH and EC (r = -0.79 and -0.81, respectively, p {\textless} 0.001). The spatial structure was modeled using stochastic point processes, in particular a hybrid family of Gibbs processes. A new model is proposed that uses a hard-core structure at very short distances, together with a cluster structure in short-to-medium distances and a Poisson structure for larger distances. This model was found to fit the data perfectly well.},
  comment  = {public},
  doi      = {10.1007/s10661-015-4403-z},
  isbn     = {01676369 (ISSN)},
  pmid     = {25838060},
}

Obtaining information about the spatial distribution of desert plants is considered as a serious challenge for ecologists and environmental modeling due to the required intensive field work and infrastructures in harsh and remote arid environments. A new method was applied for assessing the spatial distribution of the halophytic species (HS) in an arid coastal environment. This method was based on the object-based image analysis for a high-resolution Google Earth satellite image. The integration of the image processing techniques and field work provided accurate information about the spatial distribution of HS. The extracted objects were based on assumptions that explained the plant-pixel relationship. Three different types of digital image processing techniques were implemented and validated to obtain an accurate HS spatial distribution. A total of 2703 individuals of the HS community were found in the case study, and approximately 82 % were located above an elevation of 2 m. The micro-topography exhibited a significant negative relationship with pH and EC (r = -0.79 and -0.81, respectively, p \textless 0.001). The spatial structure was modeled using stochastic point processes, in particular a hybrid family of Gibbs processes. A new model is proposed that uses a hard-core structure at very short distances, together with a cluster structure in short-to-medium distances and a Poisson structure for larger distances. This model was found to fit the data perfectly well.

@Article{Bauling2015,
  author  = {Bauling, S. and Saborowski, Joachim and R{\"{u}}he, F.},
  title   = {{Rotwild im Solling - Gleichung mit Unbekannten?}},
  journal = {Nieders{\"{a}}chsischer J{\"{a}}ger},
  year    = {2015},
  pages   = {28--33},
  url_pdf = {http://uni-goettingen.de/de/document/download/744f21c3f065eb12b6ec8692f8154d61.pdf/2015_Bauling_etal_Rotwild%20im%20Solling.pdf},
  comment = {public},
}

@Article{Esser2015,
  author   = {Esser, Daniel S. and Leveau, Johan H J and Meyer, Katrin M. and Wiegand, Kerstin},
  title    = {{Spatial scales of interactions among bacteria and between bacteria and the leaf surface}},
  journal  = {FEMS microbiology ecology},
  year     = {2015},
  volume   = {91},
  number   = {3},
  issn     = {15746941},
  url_pdf  = {http://uni-goettingen.de/de/document/download/261f8977ac41f3de35b7aedd468ca4fd.pdf/Esser_et_al_2015_MICROBIOLOGY_ECOLOGY_spatial_scales_bacterial_interactions.pdf},
  abstract = {Microbial life on plant leaves is characterized by a multitude of interactions between leaf colonizers and their environment. While the existence of many of these interactions has been confirmed, their spatial scale or reach often remained unknown. In this study, we applied spatial point pattern analysis to 244 distribution patterns of Pantoea agglomerans and Pseudomonas syringae on bean leaves. The results showed that bacterial colonizers of leaves interact with their environment at different spatial scales. Interactions among bacteria were often confined to small spatial scales up to 5-20 $\mu$m, compared to interactions between bacteria and leaf surface structures such as trichomes which could be observed in excess of 100 $\mu$m. Spatial point-pattern analyses prove a comprehensive tool to determine the different spatial scales of bacterial interactions on plant leaves and will help microbiologists to better understand the interplay between these interactions.},
  comment  = {public},
  doi      = {10.1093/femsec/fiu034},
  isbn     = {0168-6496},
  keywords = {K-function,Pantoea,Phaseolus vulgaris,Pseudomonas,pair correlation function,phyllosphere},
  pmid     = {25764562},
}

Microbial life on plant leaves is characterized by a multitude of interactions between leaf colonizers and their environment. While the existence of many of these interactions has been confirmed, their spatial scale or reach often remained unknown. In this study, we applied spatial point pattern analysis to 244 distribution patterns of Pantoea agglomerans and Pseudomonas syringae on bean leaves. The results showed that bacterial colonizers of leaves interact with their environment at different spatial scales. Interactions among bacteria were often confined to small spatial scales up to 5-20 $μ$m, compared to interactions between bacteria and leaf surface structures such as trichomes which could be observed in excess of 100 $μ$m. Spatial point-pattern analyses prove a comprehensive tool to determine the different spatial scales of bacterial interactions on plant leaves and will help microbiologists to better understand the interplay between these interactions.

@Article{Esser2015a,
  author   = {Esser, Daniel S. and Leveau, Johan H. J. and Meyer, Katrin M.},
  title    = {{Modeling microbial growth and dynamics}},
  journal  = {Applied Microbiology and Biotechnology},
  year     = {2015},
  volume   = {99},
  number   = {21},
  pages    = {8831--8846},
  issn     = {0175-7598},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e506917ec7e14ebfa7762a68de097a23.pdf/Esser%20et%20al.%20-%202015%20-%20Modeling%20microbial%20growth%20and%20dynamics.pdf},
  abstract = {Modeling has become an important tool for widening our understanding of microbial growth in the context of applied microbiology and related to such processes as safe food production, wastewater treatment, bioremediation, or microbe-mediated mining. Various modeling techniques, such as primary, secondary and tertiary mathematical models, phenomenological models, mechanistic or kinetic models, reactive transport models, Bayesian network models, artificial neural networks, as well as agent-, individual-, and particle-based models have been applied to model microbial growth and activity in many applied fields. In this mini-review, we summarize the basic concepts of these models using examples and applications from food safety and wastewater treatment systems. We further review recent developments in other applied fields focusing on models that explicitly include spatial relationships. Using these examples, we point out the conceptual similarities across fields of application and encourage the combined use of different modeling techniques in hybrid models as well as their cross-disciplinary exchange. For instance, pattern-oriented modeling has its origin in ecology but may be employed to parameterize microbial growth models when experimental data are scarce. Models could also be used as virtual laboratories to optimize experimental design analogous to the virtual ecologist approach. Future microbial growth models will likely become more complex to benefit from the rich toolbox that is now available to microbial growth modelers.},
  comment  = {public},
  doi      = {10.1007/s00253-015-6877-6},
  isbn     = {0025301568776},
  pmid     = {26298697},
  url      = {http://link.springer.com/10.1007/s00253-015-6877-6},
}

Modeling has become an important tool for widening our understanding of microbial growth in the context of applied microbiology and related to such processes as safe food production, wastewater treatment, bioremediation, or microbe-mediated mining. Various modeling techniques, such as primary, secondary and tertiary mathematical models, phenomenological models, mechanistic or kinetic models, reactive transport models, Bayesian network models, artificial neural networks, as well as agent-, individual-, and particle-based models have been applied to model microbial growth and activity in many applied fields. In this mini-review, we summarize the basic concepts of these models using examples and applications from food safety and wastewater treatment systems. We further review recent developments in other applied fields focusing on models that explicitly include spatial relationships. Using these examples, we point out the conceptual similarities across fields of application and encourage the combined use of different modeling techniques in hybrid models as well as their cross-disciplinary exchange. For instance, pattern-oriented modeling has its origin in ecology but may be employed to parameterize microbial growth models when experimental data are scarce. Models could also be used as virtual laboratories to optimize experimental design analogous to the virtual ecologist approach. Future microbial growth models will likely become more complex to benefit from the rich toolbox that is now available to microbial growth modelers.

@Article{Getzin2015a,
  author   = {Getzin, Stephan and Wiegand, Kerstin and Wiegand, Thorsten and Yizhaq, Hezi and von Hardenberg, Jost and Meron, Ehud},
  title    = {{Adopting a spatially explicit perspective to study the mysterious fairy circles of Namibia}},
  journal  = {Ecography},
  year     = {2015},
  volume   = {38},
  number   = {1},
  pages    = {1--11},
  issn     = {16000587},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2a6ae79ecc15c75345c8adc9aa888acc.pdf/Getzin%20et%20al_2014_Ecography_Adopting%20a%20spatially%20explicit%20perspective%20to%20study%20the%20mysterious%20fairy%20circles%20of%20Namibia.pdf},
  abstract = {The mysterious ‘fairy circles' are vegetation-free discs that cover vast areas along the pro-Namib Desert. Despite 30 yr of research their origin remains unknown. Here we adopt a novel approach that focuses on analysis of the spatial patterns of fairy circles obtained from representative 25-ha aerial images of north-west Namibia. We use spatial point pattern analysis to quantify different features of their spatial structures and then critically inspect existing hypotheses with respect to their ability to generate the observed circle patterns. Our working hypothesis is that fairy circles are a self-organized vegetation pattern. Finally, we test if an existing partial-differential-equation model, that was designed to describe vegetation pattern formation, is able to reproduce the characteristic features of the observed fairy circle patterns. The model is based on key-processes in arid areas such as plant competition for water and local resource-biomass feedbacks. The fairy circles showed at all three study areas the same regular spatial distribution patterns, characterized by Voronoi cells with mostly six corners, negative correlations in their size up to a distance of 13 m, and remarkable homogeneity over large spatial scales. These results cast doubts on abiotic gas-leakage along geological lines or social insects as causal agents of their origin. However, our mathematical model was able to generate spatial patterns that agreed quantitatively in all of these features with the observed patterns. This supports the hypothesis that fairy circles are self-organized vegetation patterns that emerge from positive biomass-water feedbacks involving water transport by extended root systems and soil-water diffusion. Future research should search for mechanisms that explain how the different hypotheses can generate the patterns observed here and test the ability of self-organization to match the birth- and death dynamics of fairy circles and their regional patterns in the density and size with respect to environmental gradients.},
  comment  = {public},
  doi      = {10.1111/ecog.00911},
  isbn     = {09067590},
}

The mysterious ‘fairy circles' are vegetation-free discs that cover vast areas along the pro-Namib Desert. Despite 30 yr of research their origin remains unknown. Here we adopt a novel approach that focuses on analysis of the spatial patterns of fairy circles obtained from representative 25-ha aerial images of north-west Namibia. We use spatial point pattern analysis to quantify different features of their spatial structures and then critically inspect existing hypotheses with respect to their ability to generate the observed circle patterns. Our working hypothesis is that fairy circles are a self-organized vegetation pattern. Finally, we test if an existing partial-differential-equation model, that was designed to describe vegetation pattern formation, is able to reproduce the characteristic features of the observed fairy circle patterns. The model is based on key-processes in arid areas such as plant competition for water and local resource-biomass feedbacks. The fairy circles showed at all three study areas the same regular spatial distribution patterns, characterized by Voronoi cells with mostly six corners, negative correlations in their size up to a distance of 13 m, and remarkable homogeneity over large spatial scales. These results cast doubts on abiotic gas-leakage along geological lines or social insects as causal agents of their origin. However, our mathematical model was able to generate spatial patterns that agreed quantitatively in all of these features with the observed patterns. This supports the hypothesis that fairy circles are self-organized vegetation patterns that emerge from positive biomass-water feedbacks involving water transport by extended root systems and soil-water diffusion. Future research should search for mechanisms that explain how the different hypotheses can generate the patterns observed here and test the ability of self-organization to match the birth- and death dynamics of fairy circles and their regional patterns in the density and size with respect to environmental gradients.

@Article{Getzin2015,
  author  = {Getzin, Stephan and Wiegand, Kerstin and Wiegand, Thorsten and Yizhaq, Hezi and {Von Hardenberg}, Jost and Meron, Ehud},
  title   = {{Clarifying misunderstandings regarding vegetation self-organisation and spatial patterns of fairy circles in Namibia: A response to recent termite hypotheses}},
  journal = {Ecological Entomology},
  year    = {2015},
  volume  = {40},
  number  = {6},
  pages   = {669--675},
  issn    = {13652311},
  url_pdf = {http://uni-goettingen.de/de/document/download/31d4de7486ccfce6a4ae2e02a52b4d75.pdf/Getzin_et_al_2015_ECOLOGICAL_ENTOMOLOGY_misunderstandings_vegetation_self-organisation_spatial_patterns_fairy_circles.pdf},
  comment = {public},
  doi     = {10.1111/een.12267},
}

@Article{Punchi-Manage2015,
  author   = {Punchi-Manage, Ruwan and Wiegand, Thorsten and Wiegand, Kerstin and Getzin, Stephan and Huth, Andreas and Gunatilleke, C. V.Savitri and Gunatilleke, I. A.U.Nimal and Metcalfe, D. B.},
  title    = {{Neighborhood diversity of large trees shows independent species patterns in a mixed dipterocarp forest in Sri Lanka}},
  journal  = {Ecology},
  year     = {2015},
  volume   = {96},
  number   = {7},
  pages    = {1823--1834},
  issn     = {00129658},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d6aa2f60b397f2db9e0d67b1e5c32da5.pdf/Punchi-Manage_et_al_2015_Ecology_Neighborhood_diversity_of_large_trees__independent_species_patterns__forest__Sri.pdf},
  abstract = {Interactions among neighbors influence plant performance and should create spatial patterns in local community structure. In order to assess the role of large trees in generating spatial patterns in local species richness we used the individual species-area relationship (ISAR) to evaluate the species richness of trees of different size classes (and dead trees) in neighborhoods with varying size around large trees of different focal species. To reveal signals of species interactions we compared the ISAR function of the individuals of focal species with that of randomly selected nearby locations. We expected that large trees should strongly affect the community structure of smaller trees in their neighborhood, but that these effects should fade away with increasing size class. Unexpectedly we found that only few focal species showed signals of species interactions with trees of the different size classes and that this was less likely for less abundant focal species. However, the few and relatively weak depa...},
  comment  = {public},
  doi      = {http://dx.doi.org/10.1890/14-1477.1},
  isbn     = {10.1890/14-1477.1},
  keywords = {Independence null model,Individual species-area relationship,Neighborhood diversity,Point pattern analysis,Sinharaja tropical forest,Spatial scale,Stochastic dilution},
}

Interactions among neighbors influence plant performance and should create spatial patterns in local community structure. In order to assess the role of large trees in generating spatial patterns in local species richness we used the individual species-area relationship (ISAR) to evaluate the species richness of trees of different size classes (and dead trees) in neighborhoods with varying size around large trees of different focal species. To reveal signals of species interactions we compared the ISAR function of the individuals of focal species with that of randomly selected nearby locations. We expected that large trees should strongly affect the community structure of smaller trees in their neighborhood, but that these effects should fade away with increasing size class. Unexpectedly we found that only few focal species showed signals of species interactions with trees of the different size classes and that this was less likely for less abundant focal species. However, the few and relatively weak depa...

@Article{Schaffler2015,
  author   = {Sch{\"{a}}ffler, Livia and Saborowski, Joachim and Kappeler, Peter M.},
  title    = {{Agent-mediated spatial storage effect in heterogeneous habitat stabilizes competitive mouse lemur coexistence in Menabe Central, Western Madagascar}},
  journal  = {BMC Ecology},
  year     = {2015},
  volume   = {15},
  number   = {1},
  issn     = {14726785},
  url_pdf  = {http://uni-goettingen.de/de/document/download/7332860cd10c220453346760a8f9c8f9.pdf/Schaeffler_et_al_(2015)_Agent_mediated_spatial_storage_effect_mouse_lemur_coexistence.pdf},
  abstract = {BACKGROUND: Spatio-temporal distribution patterns of species in response to natural and anthropogenic drivers provide insight into the ecological processes that determine community composition. We investigated determinants of ecological structure in a species assemblage of 4 closely related primate species of the family Cheirogaleidae (Microcebus berthae, Microcebus murinus, Cheirogaleus medius, Mirza coquereli) in western Madagascar by extensive line transect surveys across spatial and temporal heterogeneities with the specific goal of elucidating the mechanisms stabilizing competitive coexistence of the two mouse lemur species (Microcebus spp.).$\backslash$n$\backslash$nRESULTS: Interspecific competition between the mouse lemurs was indicated by negative spatial associations in degraded habitat and by habitat partitioning along anthropogenic disturbance gradients during dry seasons with resource scarcity. In non-degraded habitat, intraguild predator M. coquereli, but not C. medius, was negatively associated with M. murinus on the population level, whereas its regional distribution overlapped spatially with that of M. berthae. The species' interspecific distribution pattern across spatial and temporal heterogeneities corresponded to predictions for agent-mediated coexistence and thus confirmed M. coquereli's stabilizing impact on the coexistence of mouse lemurs.$\backslash$n$\backslash$nCONCLUSIONS: Interspecific interactions contribute to ecological structure in this cheirogaleid assemblage and determinants vary across spatio-temporal heterogeneities. Coexistence of Microcebus spp. is stabilized by an agent-mediated spatial storage effect: M. coquereli creates refuges from competition for M. berthae in intact habitat, whereas anthropogenic environments provide M. murinus with an escape from resource competition and intraguild predation. Species persistence in the assemblage therefore depends on the conservation of habitat content and context that stabilizing mechanisms rely on. Our large-scale population level approach did not allow for considering all potential functional and stochastic drivers of ecological structure, a key limitation that accounts for the large proportion of unexplained variance in our models.},
  comment  = {public},
  doi      = {10.1186/s12898-015-0040-1},
  keywords = {Agent-mediated coexistence,Competition,Ecological structure,Interspecific interactions,Intraguild predation,Lemurs,Spatial storage effect,Species assemblage},
  pmid     = {25888023},
}

BACKGROUND: Spatio-temporal distribution patterns of species in response to natural and anthropogenic drivers provide insight into the ecological processes that determine community composition. We investigated determinants of ecological structure in a species assemblage of 4 closely related primate species of the family Cheirogaleidae (Microcebus berthae, Microcebus murinus, Cheirogaleus medius, Mirza coquereli) in western Madagascar by extensive line transect surveys across spatial and temporal heterogeneities with the specific goal of elucidating the mechanisms stabilizing competitive coexistence of the two mouse lemur species (Microcebus spp.).$\$n$\$nRESULTS: Interspecific competition between the mouse lemurs was indicated by negative spatial associations in degraded habitat and by habitat partitioning along anthropogenic disturbance gradients during dry seasons with resource scarcity. In non-degraded habitat, intraguild predator M. coquereli, but not C. medius, was negatively associated with M. murinus on the population level, whereas its regional distribution overlapped spatially with that of M. berthae. The species' interspecific distribution pattern across spatial and temporal heterogeneities corresponded to predictions for agent-mediated coexistence and thus confirmed M. coquereli's stabilizing impact on the coexistence of mouse lemurs.$\$n$\$nCONCLUSIONS: Interspecific interactions contribute to ecological structure in this cheirogaleid assemblage and determinants vary across spatio-temporal heterogeneities. Coexistence of Microcebus spp. is stabilized by an agent-mediated spatial storage effect: M. coquereli creates refuges from competition for M. berthae in intact habitat, whereas anthropogenic environments provide M. murinus with an escape from resource competition and intraguild predation. Species persistence in the assemblage therefore depends on the conservation of habitat content and context that stabilizing mechanisms rely on. Our large-scale population level approach did not allow for considering all potential functional and stochastic drivers of ecological structure, a key limitation that accounts for the large proportion of unexplained variance in our models.

@Article{Accatino2014,
  author   = {Accatino, F. and Sabatier, R. and {De Michele}, C. and Ward, D. and Wiegand, K. and Meyer, K. M.},
  title    = {{Robustness and management adaptability in tropical rangelands: A viability-based assessment under the non-equilibrium paradigm}},
  journal  = {Animal},
  year     = {2014},
  volume   = {8},
  number   = {8},
  pages    = {1272--1281},
  issn     = {1751732X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2dd3b04f3b7053e7a7e3545e5c35c40e.pdf/AccatinoEtAlAnimal_(2014)_Animal_Robustness_and_management_adaptability_tropical_rangelands%20.pdf},
  abstract = {{\textless}p{\textgreater}Rangelands provide the main forage resource for livestock in many parts of the world, but maintaining long-term productivity and providing sufficient income for the rancher remains a challenge. One key issue is to maintain the rangeland in conditions where the rancher has the greatest possibility to adapt his/her management choices to a highly fluctuating and uncertain environment. In this study, we address management robustness and adaptability, which increase the resilience of a rangeland. After reviewing how the concept of resilience evolved in parallel to modelling views on rangelands, we present a dynamic model of rangelands to which we applied the mathematical framework of viability theory to quantify the management adaptability of the system in a stochastic environment. This quantification is based on an index that combines the robustness of the system to rainfall variability and the ability of the rancher to adjust his/her management through time. We evaluated the adaptability for four possible scenarios combining two rainfall regimes (high or low) with two herding strategies (grazers only or mixed herd). Results show that pure grazing is viable only for high-rainfall regimes, and that the use of mixed-feeder herds increases the adaptability of the management. The management is the most adaptive with mixed herds and in rangelands composed of an intermediate density of trees and grasses. In such situations, grass provides high quantities of biomass and woody plants ensure robustness to droughts. Beyond the implications for management, our results illustrate the relevance of viability theory for addressing the issue of robustness and adaptability in non-equilibrium environments.{\textless}/p{\textgreater}},
  comment  = {public},
  doi      = {10.1017/S1751731114000913},
  isbn     = {1751-732X},
  keywords = {adaptability,herding strategy,resilience,robustness,viability},
  pmid     = {24780528},
}

\textlessp\textgreaterRangelands provide the main forage resource for livestock in many parts of the world, but maintaining long-term productivity and providing sufficient income for the rancher remains a challenge. One key issue is to maintain the rangeland in conditions where the rancher has the greatest possibility to adapt his/her management choices to a highly fluctuating and uncertain environment. In this study, we address management robustness and adaptability, which increase the resilience of a rangeland. After reviewing how the concept of resilience evolved in parallel to modelling views on rangelands, we present a dynamic model of rangelands to which we applied the mathematical framework of viability theory to quantify the management adaptability of the system in a stochastic environment. This quantification is based on an index that combines the robustness of the system to rainfall variability and the ability of the rancher to adjust his/her management through time. We evaluated the adaptability for four possible scenarios combining two rainfall regimes (high or low) with two herding strategies (grazers only or mixed herd). Results show that pure grazing is viable only for high-rainfall regimes, and that the use of mixed-feeder herds increases the adaptability of the management. The management is the most adaptive with mixed herds and in rangelands composed of an intermediate density of trees and grasses. In such situations, grass provides high quantities of biomass and woody plants ensure robustness to droughts. Beyond the implications for management, our results illustrate the relevance of viability theory for addressing the issue of robustness and adaptability in non-equilibrium environments.\textless/p\textgreater

@Article{Chisholm2014,
  author   = {Chisholm, Ryan A. and Condit, Richard and Rahman, K. A. and Baker, Patrick J. and Bunyavejchewin, Sarayudh and Chen, Yu Yun and Chuyong, George and Dattaraja, H. S. and Davies, Stuart and Ewango, Corneille E N and Gunatilleke, C. V S and {Nimal Gunatilleke}, I. A U and Hubbell, Stephen and Kenfack, David and Kiratiprayoon, Somboon and Lin, Yiching and Makana, Jean Remy and Pongpattananurak, Nantachai and Pulla, Sandeep and Punchi-Manage, Ruwan and Sukumar, Raman and Su, Sheng Hsin and Sun, I. Fang and Suresh, H. S. and Tan, Sylvester and Thomas, Duncan and Yap, Sandra},
  title    = {{Temporal variability of forest communities: Empirical estimates of population change in 4000 tree species}},
  journal  = {Ecology Letters},
  year     = {2014},
  volume   = {17},
  number   = {7},
  pages    = {855--865},
  issn     = {14610248},
  url_pdf  = {http://uni-goettingen.de/de/document/download/897eb9b870e62d8de832707962fe96a6.pdf/Chisholm_et_al_2014_ECOLOGY_LETTERS_temporal_variability_forest_communities.pdf},
  abstract = {Long-term surveys of entire communities of species are needed to measure fluctuations in natural populations and elucidate the mechanisms driving population dynamics and community assembly. We analysed changes in abundance of over 4000 tree species in 12 forests across the world over periods of 6-28 years. Abundance fluctuations in all forests are large and consistent with population dynamics models in which temporal environmental variance plays a central role. At some sites we identify clear environmental drivers, such as fire and drought, that could underlie these patterns, but at other sites there is a need for further research to identify drivers. In addition, cross-site comparisons showed that abundance fluctuations were smaller at species-rich sites, consistent with the idea that stable environmental conditions promote higher diversity. Much community ecology theory emphasises demographic variance and niche stabilisation; we encourage the development of theory in which temporal environmental variance plays a central role.},
  comment  = {public},
  doi      = {10.1111/ele.12296},
  isbn     = {1461-0248},
  keywords = {Abundance fluctuations,Biodiversity,Demographic stochasticity,Environmental variance,Forest dynamics,Neutral theory,Niche stabilization},
  pmid     = {24805976},
}

Long-term surveys of entire communities of species are needed to measure fluctuations in natural populations and elucidate the mechanisms driving population dynamics and community assembly. We analysed changes in abundance of over 4000 tree species in 12 forests across the world over periods of 6-28 years. Abundance fluctuations in all forests are large and consistent with population dynamics models in which temporal environmental variance plays a central role. At some sites we identify clear environmental drivers, such as fire and drought, that could underlie these patterns, but at other sites there is a need for further research to identify drivers. In addition, cross-site comparisons showed that abundance fluctuations were smaller at species-rich sites, consistent with the idea that stable environmental conditions promote higher diversity. Much community ecology theory emphasises demographic variance and niche stabilisation; we encourage the development of theory in which temporal environmental variance plays a central role.

@Article{Getzin2014,
  author   = {Getzin, Stephan and Nuske, Robert S. and Wiegand, Kerstin},
  title    = {{Using unmanned aerial vehicles (UAV) to quantify spatial gap patterns in forests}},
  journal  = {Remote Sensing},
  year     = {2014},
  volume   = {6},
  number   = {8},
  pages    = {6988--7004},
  issn     = {20724292},
  url_pdf  = {http://uni-goettingen.de/de/document/download/0738eaf6721cfc69d07ef90c4041bb0f.pdf/GetzinEtAlRemoteSensing_(2014)_RemoteSens_UAV_to_Quantify_Spatial_Gap_Patterns.pdf},
  abstract = {Gap distributions in forests reflect the spatial impact of man-made tree harvesting or naturally-induced patterns of tree death being caused by windthrow, inter-tree competition, disease or senescence. Gap sizes can vary from large ({\textgreater}100 m2) to small $\backslash$r$\backslash$n({\textless}10 m2), and they may have contrasting spatial patterns, such as being aggregated or regularly distributed. However, very small gaps cannot easily be recorded with conventional aerial or satellite images, which calls for new and cost-effective methodologies of forest monitoring. Here, we used an unmanned aerial vehicle (UAV) and very high-resolution images to record the gaps in 10 temperate managed and unmanaged forests in two regions of Germany. All gaps were extracted for 1-ha study plots and subsequently analyzed with spatially-explicit statistics, such as the conventional $\backslash$r$\backslash$npair correlation function (PCF), the polygon-based PCF and the mark correlation function. Gap-size frequency was dominated by small gaps of an area {\textless}5 m2, which were particularly frequent in unmanaged forests. We found that gap distances showed a variety of patterns. However, the polygon-based PCF was a better descriptor of patterns than the conventional PCF, because it showed randomness or aggregation for cases when the conventional PCF showed small-scale regularity; albeit, the latter was only a mathematical artifact. The mark correlation function revealed that gap areas were in half of the cases negatively correlated and in the other half independent. Negative size correlations may likely be the result of single-tree harvesting or of repeated gap formation, which both lead to nearby small gaps. Here, we emphasize the usefulness of UAV to record forest gaps of a very small size. These small gaps may originate from repeated gap-creating disturbances, and their spatial patterns should be monitored with spatially-explicit statistics at recurring intervals in order to further insights into forest dynamics.},
  comment  = {public},
  doi      = {10.3390/rs6086988},
  isbn     = {2072-4292},
  keywords = {Autonomous flying,Biodiversity,Canopy gaps,Drone,Polygon-based pair correlation function,RPV,Remotely piloted vehicles,UAS,UAV,Unmanned aircraft systems},
}

Gap distributions in forests reflect the spatial impact of man-made tree harvesting or naturally-induced patterns of tree death being caused by windthrow, inter-tree competition, disease or senescence. Gap sizes can vary from large (\textgreater100 m2) to small $\$r$\$n(\textless10 m2), and they may have contrasting spatial patterns, such as being aggregated or regularly distributed. However, very small gaps cannot easily be recorded with conventional aerial or satellite images, which calls for new and cost-effective methodologies of forest monitoring. Here, we used an unmanned aerial vehicle (UAV) and very high-resolution images to record the gaps in 10 temperate managed and unmanaged forests in two regions of Germany. All gaps were extracted for 1-ha study plots and subsequently analyzed with spatially-explicit statistics, such as the conventional $\$r$\$npair correlation function (PCF), the polygon-based PCF and the mark correlation function. Gap-size frequency was dominated by small gaps of an area \textless5 m2, which were particularly frequent in unmanaged forests. We found that gap distances showed a variety of patterns. However, the polygon-based PCF was a better descriptor of patterns than the conventional PCF, because it showed randomness or aggregation for cases when the conventional PCF showed small-scale regularity; albeit, the latter was only a mathematical artifact. The mark correlation function revealed that gap areas were in half of the cases negatively correlated and in the other half independent. Negative size correlations may likely be the result of single-tree harvesting or of repeated gap formation, which both lead to nearby small gaps. Here, we emphasize the usefulness of UAV to record forest gaps of a very small size. These small gaps may originate from repeated gap-creating disturbances, and their spatial patterns should be monitored with spatially-explicit statistics at recurring intervals in order to further insights into forest dynamics.

@Article{Hai2014,
  author   = {Hai, Nguyen Hong and Wiegand, Kerstin and Getzin, Stephan},
  title    = {{Spatial distributions of tropical tree species in northern Vietnam under environmentally variable site conditions}},
  journal  = {Journal of Forestry Research},
  year     = {2014},
  volume   = {25},
  number   = {2},
  pages    = {257--268},
  issn     = {19930607},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a024732572c506ebbc55876f8bb634a5.pdf/Hai_et_al_2014_JOURNAL_OF_FORESTRY_spatial_distributions_tropical_tree_species_Vietnam.pdf},
  abstract = {Ecological interactions of species and thus their spatial patterns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that: environmental conditions were homogeneous at plot 1 but heterogeneous at plot 2; in both plots, all six dominant species were aggregated at various scales up to 30 m, and tree species were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia (homogeneous plot) and D. sylvatica, S. wightianum (heterogeneous plot), showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-Connell hypothesis. Overall, habitat heterogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.},
  comment  = {public},
  doi      = {10.1007/s11676-014-0457-y},
  isbn     = {1007-662X$\backslash$r1993-0607},
  keywords = {environmental heterogeneity,northern Vietnam,spatial point pattern analysis,tropical evergreen forest},
}

Ecological interactions of species and thus their spatial patterns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that: environmental conditions were homogeneous at plot 1 but heterogeneous at plot 2; in both plots, all six dominant species were aggregated at various scales up to 30 m, and tree species were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia (homogeneous plot) and D. sylvatica, S. wightianum (heterogeneous plot), showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-Connell hypothesis. Overall, habitat heterogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species.

@Article{Hartig2014,
  author        = {Hartig, F. and Dislich, C. and Wiegand, T. and Huth, A.},
  title         = {{Technical note: Approximate bayesian parameterization of a process-based tropical forest model}},
  journal       = {Biogeosciences},
  year          = {2014},
  volume        = {11},
  number        = {4},
  pages         = {1261--1272},
  issn          = {17264170},
  url_pdf       = {http://uni-goettingen.de/de/document/download/75be9018b99d01eeb211cc03563cc018.pdf/Hartig%20et%20al._2014_Biogeosciences_Technical%20Note%20Approximate%20Bayesian%20parameterization%20of%20a%20process-based%20tropical%20forest%20model.pdf},
  abstract      = {Inverse parameter estimation of process-based models is a long-standing problem in many scientific disciplines. A key question for inverse parameter estimation is how to define the metric that quantifies how well model predictions fit to the data. This metric can be expressed by general cost or objective functions, but statistical inversion methods require a particular metric, the probability of observing the data given the model parameters, known as the likelihood. For technical and computational reasons, likelihoods for process-based stochastic models are usually based on general assumptions about variability in the observed data, and not on the stochasticity generated by the model. Only in recent years have new methods become available that allow the generation of likelihoods directly from stochastic simulations. Previous applications of these approximate Bayesian methods have concentrated on relatively simple models. Here, we report on the application of a simulation-based likelihood approximation for FORMIND, a parameter-rich individual-based model of tropical forest dynamics. We show that approximate Bayesian inference, based on a parametric likelihood approximation placed in a conventional Markov chain Monte Carlo (MCMC) sampler, performs well in retrieving known parameter values from virtual inventory data generated by the forest model. We analyze the results of the parameter estimation, examine its sensitivity to the choice and aggregation of model outputs and observed data (summary statistics), and demonstrate the application of this method by fitting the FORMIND model to field data from an Ecuadorian tropical forest. Finally, we discuss how this approach differs from approximate Bayesian computation (ABC), another method commonly used to generate simulation-based likelihood approximations. Our results demonstrate that simulation-based inference, [...]},
  archiveprefix = {arXiv},
  arxivid       = {1401.8205},
  comment       = {public},
  doi           = {10.5194/bg-11-1261-2014},
  eprint        = {1401.8205},
  isbn          = {1726-4170},
}

Inverse parameter estimation of process-based models is a long-standing problem in many scientific disciplines. A key question for inverse parameter estimation is how to define the metric that quantifies how well model predictions fit to the data. This metric can be expressed by general cost or objective functions, but statistical inversion methods require a particular metric, the probability of observing the data given the model parameters, known as the likelihood. For technical and computational reasons, likelihoods for process-based stochastic models are usually based on general assumptions about variability in the observed data, and not on the stochasticity generated by the model. Only in recent years have new methods become available that allow the generation of likelihoods directly from stochastic simulations. Previous applications of these approximate Bayesian methods have concentrated on relatively simple models. Here, we report on the application of a simulation-based likelihood approximation for FORMIND, a parameter-rich individual-based model of tropical forest dynamics. We show that approximate Bayesian inference, based on a parametric likelihood approximation placed in a conventional Markov chain Monte Carlo (MCMC) sampler, performs well in retrieving known parameter values from virtual inventory data generated by the forest model. We analyze the results of the parameter estimation, examine its sensitivity to the choice and aggregation of model outputs and observed data (summary statistics), and demonstrate the application of this method by fitting the FORMIND model to field data from an Ecuadorian tropical forest. Finally, we discuss how this approach differs from approximate Bayesian computation (ABC), another method commonly used to generate simulation-based likelihood approximations. Our results demonstrate that simulation-based inference, [...]

@Article{Meyer2014,
  author   = {Meyer, Katrin M. and Soldaat, Leo L. and Auge, Harald and Thulke, Hans-Hermann},
  title    = {{Adaptive and Selective Seed Abortion Reveals Complex Conditional Decision Making in Plants}},
  journal  = {The American Naturalist},
  year     = {2014},
  volume   = {183},
  number   = {3},
  pages    = {376--383},
  issn     = {0003-0147},
  url_pdf  = {http://uni-goettingen.de/de/document/download/567cea6ece18c3d336fcca16f7a6bab8.pdf/Meyer_et_al_(2014)_AM_NAT_Decision_making_plants.pdf},
  abstract = {Abstract Behavior is traditionally attributed to animals only. Recently, evidence for plant behavior is accumulating, mostly from plant physiological studies. Here, we provide ecological evidence for complex plant behavior in the form of seed abortion decisions conditional on internal and external cues. We analyzed seed abortion patterns of barberry plants exposed to seed parasitism and different environmental conditions. Without abortion, parasite infestation of seeds can lead to loss of all seeds in a fruit. We statistically tested a series of null models with Monte Carlo simulations to establish selectivity and adaptiveness of the observed seed abortion patterns. Seed abortion was more frequent in parasitized fruits and fruits from dry habitats. Surprisingly, seed abortion occurred with significantly greater probability if there was a second intact seed in the fruit. This strategy provides a fitness benefit if abortion can prevent a sibling seed from coinfestation and if nonabortion of an infested but surviving single seed saves resources invested in the fruit coat. Ecological evidence for complex decision making in plants thus includes a structural memory (the second seed), simple reasoning (integration of inner and outer conditions), conditional behavior (abortion), and anticipation of future risks (seed predation).},
  comment  = {public},
  doi      = {10.1086/675063},
  isbn     = {00030147},
  pmid     = {24561600},
  url      = {http://www.journals.uchicago.edu/doi/10.1086/675063},
}

Abstract Behavior is traditionally attributed to animals only. Recently, evidence for plant behavior is accumulating, mostly from plant physiological studies. Here, we provide ecological evidence for complex plant behavior in the form of seed abortion decisions conditional on internal and external cues. We analyzed seed abortion patterns of barberry plants exposed to seed parasitism and different environmental conditions. Without abortion, parasite infestation of seeds can lead to loss of all seeds in a fruit. We statistically tested a series of null models with Monte Carlo simulations to establish selectivity and adaptiveness of the observed seed abortion patterns. Seed abortion was more frequent in parasitized fruits and fruits from dry habitats. Surprisingly, seed abortion occurred with significantly greater probability if there was a second intact seed in the fruit. This strategy provides a fitness benefit if abortion can prevent a sibling seed from coinfestation and if nonabortion of an infested but surviving single seed saves resources invested in the fruit coat. Ecological evidence for complex decision making in plants thus includes a structural memory (the second seed), simple reasoning (integration of inner and outer conditions), conditional behavior (abortion), and anticipation of future risks (seed predation).

@Article{Nguyen2014,
  author   = {Nguyen, H. and Wiegand, K. and Getzin, S.},
  title    = {{Spatial patterns and demographics of streblus macrophyllus trees in a tropical evergreen forest, Vietnam}},
  journal  = {Journal of Tropical Forest Science},
  year     = {2014},
  volume   = {26},
  number   = {3},
  pages    = {309--319},
  issn     = {01281283},
  url_pdf  = {http://uni-goettingen.de/de/document/download/daa9801a6d9fc15a84185f62e2deed45.pdf/Nguyen_et_al_(2014)_JTropicalForestScience_Spatial_Patterns_and_Demographics_Trees_in_Tropical_Evergreen_Forest.pdf},
  abstract = {Streblus macrophyllus is a shade-tolerant and subcanopy tree species common to tropical evergreen forests in northern Vietnam. However, its ecology is poorly known. We used spatial point pattern analysis to describe the spatial arrangement of tree individuals within a forest community dominated by S. macrophyllus. All individual trees with diameter at breast height larger than 2.5 cm in a 1-ha plot were mapped and measured. The overall pattern of this species was a regular distribution at scales up to 2 m. Its juveniles and subadults were strongly aggregated, but adult trees were regular at scales of up to 3 m, implying evidence of density dependent thinning. The spatial pattern of S. macrophyllus strongly affected the patterning of the whole plot. In S. macrophyUus y juveniles and subadults were similarly distributed relative to adults and showed additional clumping independent of the adults. The overall interspecific association between adults of other species and S. macrophyllus at different life-history stages also showed independence. We conclude that S. macrophyllus is a predominant competitor within the community and it follows a gap-phase regeneration mode.},
  comment  = {public},
  isbn     = {01281283},
  keywords = {Forest community,Gap-phase regeneration mode,Intra- and interspecific associations,Point pattern analysis},
}

Streblus macrophyllus is a shade-tolerant and subcanopy tree species common to tropical evergreen forests in northern Vietnam. However, its ecology is poorly known. We used spatial point pattern analysis to describe the spatial arrangement of tree individuals within a forest community dominated by S. macrophyllus. All individual trees with diameter at breast height larger than 2.5 cm in a 1-ha plot were mapped and measured. The overall pattern of this species was a regular distribution at scales up to 2 m. Its juveniles and subadults were strongly aggregated, but adult trees were regular at scales of up to 3 m, implying evidence of density dependent thinning. The spatial pattern of S. macrophyllus strongly affected the patterning of the whole plot. In S. macrophyUus y juveniles and subadults were similarly distributed relative to adults and showed additional clumping independent of the adults. The overall interspecific association between adults of other species and S. macrophyllus at different life-history stages also showed independence. We conclude that S. macrophyllus is a predominant competitor within the community and it follows a gap-phase regeneration mode.

@Article{Peer2014,
  author   = {Pe'er, Guy and Mihoub, Jean-Baptiste and Dislich, Claudia and Matsinos, Yiannis},
  title    = {{Towards a different attitude to uncertainty}},
  journal  = {Nature Conservation},
  year     = {2014},
  volume   = {8},
  pages    = {95--114},
  issn     = {1314-3301},
  url_pdf  = {http://uni-goettingen.de/de/document/download/68773dea6c714962f17de86b8936b01a.pdf/Peer%20et%20al._2014_Nature%20Conservation_Towards%20a%20different%20attitude%20to%20uncertainty.pdf},
  abstract = {The ecological literature deals with uncertainty primarily from the$\backslash$nperspective of how to reduce it to acceptable levels. However, the$\backslash$ncurrent rapid and ubiquitous environmental changes, as well as$\backslash$nanticipated rates of change, pose novel conditions and complex dynamics$\backslash$ndue to which many sources of uncertainty are difficult or even$\backslash$nimpossible to reduce. These include both uncertainty in knowledge$\backslash$n(epistemic uncertainty) and societal responses to it. Under these$\backslash$nconditions, an increasing number of studies ask how one can deal with$\backslash$nuncertainty as it is. Here, we explore the question how to adopt an$\backslash$noverall alternative attitude to uncertainty, which accepts or even$\backslash$nembraces it. First, we show that seeking to reduce uncertainty may be$\backslash$ncounterproductive under some circumstances. It may yield overconfidence,$\backslash$nignoring early warning signs, policy- and societal stagnation, or$\backslash$nirresponsible behaviour if personal certainty is offered by$\backslash$nexternalization of environmental costs. We then demonstrate that$\backslash$nuncertainty can have positive impacts by driving improvements in$\backslash$nknowledge, promoting cautious action, contributing to keeping societies$\backslash$nflexible and adaptable, enhancing awareness, support and involvement of$\backslash$nthe public in nature conservation, and enhancing cooperation and$\backslash$ncommunication. We discuss the risks of employing a certainty paradigm on$\backslash$nuncertain knowledge, the potential benefits of adopting an alternative$\backslash$nattitude to uncertainty, and the need to implement such an attitude$\backslash$nacross scales - from adaptive management at the local scale, to the$\backslash$nevolving Intergovernmental Science-Policy Platform on Biodiversity and$\backslash$nEcosystem Services (IPBES) at the global level.},
  comment  = {public},
  doi      = {10.3897/natureconservation.8.8388},
  isbn     = {1314-6947
1314-3301},
  url      = {http://natureconservation.pensoft.net/articles.php?id=4143},
}

The ecological literature deals with uncertainty primarily from the$\$nperspective of how to reduce it to acceptable levels. However, the$\$ncurrent rapid and ubiquitous environmental changes, as well as$\$nanticipated rates of change, pose novel conditions and complex dynamics$\$ndue to which many sources of uncertainty are difficult or even$\$nimpossible to reduce. These include both uncertainty in knowledge$\$n(epistemic uncertainty) and societal responses to it. Under these$\$nconditions, an increasing number of studies ask how one can deal with$\$nuncertainty as it is. Here, we explore the question how to adopt an$\$noverall alternative attitude to uncertainty, which accepts or even$\$nembraces it. First, we show that seeking to reduce uncertainty may be$\$ncounterproductive under some circumstances. It may yield overconfidence,$\$nignoring early warning signs, policy- and societal stagnation, or$\$nirresponsible behaviour if personal certainty is offered by$\$nexternalization of environmental costs. We then demonstrate that$\$nuncertainty can have positive impacts by driving improvements in$\$nknowledge, promoting cautious action, contributing to keeping societies$\$nflexible and adaptable, enhancing awareness, support and involvement of$\$nthe public in nature conservation, and enhancing cooperation and$\$ncommunication. We discuss the risks of employing a certainty paradigm on$\$nuncertain knowledge, the potential benefits of adopting an alternative$\$nattitude to uncertainty, and the need to implement such an attitude$\$nacross scales - from adaptive management at the local scale, to the$\$nevolving Intergovernmental Science-Policy Platform on Biodiversity and$\$nEcosystem Services (IPBES) at the global level.

@Article{Punchi-Manage2014,
  author   = {Punchi-Manage, Ruwan and Wiegand, Thorsten and Wiegand, Kerstin and Getzin, Stephan and Gunatilleke, C. V Savitri and Gunatilleke, I. A U Nimal},
  title    = {{Effect of spatial processes and topography on structuring species assemblages in a Sri Lankan dipterocarp forest}},
  journal  = {Ecology},
  year     = {2014},
  volume   = {95},
  number   = {2},
  pages    = {376--386},
  issn     = {00129658},
  url_pdf  = {http://uni-goettingen.de/de/document/download/395bdfa7a1b33b22d9b16f52a58ec1da.pdf/Punchi-Manage_et_al_(2014)_ECOLOGY_Species_assemblage_SriLankan_forest.pdf},
  abstract = {Niche and neutral theories emphasize different processes that contribute to the maintenance of species diversity and should leave different spatial structures in species assemblages. In this study we used variation partitioning in combination with distance-based Moran's eigenvector maps and habitat variables to determine the relative importance of the effects of pure habitat, pure spatial, and spatially structured habitat processes on the spatial distribution of tree species composition and richness in a 25-ha tropical rain forest of Sinharaja/Sri Lanka. We analyzed the contribution of those components at three spatial scales (10 m, 20 m, and 50 m) for all trees and the three life stages: recruits, juveniles, and adults. At the 10-m scale, 80{\%} of the variation in species composition remained unexplained for recruits and adults, but only 55{\%} for juveniles. With increasingly broader scales these figures were strongly reduced, mainly by an increasing contribution of the spatially structured habitat component, which explained 4-30{\%}, 20-47{\%}, and 8-35{\%} of variation in species composition for recruits, juveniles, and adults, respectively. The pure spatial component was most important at the 20-m scale and reached 20{\%}, 32{\%}, and 23{\%} for recruits, juveniles, and adults, respectively. The spatially structured habitat component described variability at broader scales than the pure spatial component. Our results suggest that stochastic processes and spatially structuring processes of community dynamics, such as dispersal limitation and habitat association, contributed jointly to explain species composition and richness at the Sinharaja forest, but their relative importance changed with scale and life stage. Species assembly at the local scale was more strongly impacted by stochasticity, whereas the signal of habitat was stronger at the 50-m scale where plant-scale stochasticity is averaged out. Recent research points to an emerging consensus on the relative contribution of stochasticity, habitat, and spatial processes in governing community assembly, but how these components change with life stage, and how this is influenced by sample size, remains to be explored.},
  comment  = {public},
  doi      = {10.1890/12-2102.1},
  isbn     = {0012-9658},
  keywords = {Distance-based Moran's eigenvector maps,Neutral theory,Niche theory,Sinharaja forest,Spatial scale,Species composition and richness,Sri Lanka,Variation partitioning},
  pmid     = {24669731},
}

Niche and neutral theories emphasize different processes that contribute to the maintenance of species diversity and should leave different spatial structures in species assemblages. In this study we used variation partitioning in combination with distance-based Moran's eigenvector maps and habitat variables to determine the relative importance of the effects of pure habitat, pure spatial, and spatially structured habitat processes on the spatial distribution of tree species composition and richness in a 25-ha tropical rain forest of Sinharaja/Sri Lanka. We analyzed the contribution of those components at three spatial scales (10 m, 20 m, and 50 m) for all trees and the three life stages: recruits, juveniles, and adults. At the 10-m scale, 80% of the variation in species composition remained unexplained for recruits and adults, but only 55% for juveniles. With increasingly broader scales these figures were strongly reduced, mainly by an increasing contribution of the spatially structured habitat component, which explained 4-30%, 20-47%, and 8-35% of variation in species composition for recruits, juveniles, and adults, respectively. The pure spatial component was most important at the 20-m scale and reached 20%, 32%, and 23% for recruits, juveniles, and adults, respectively. The spatially structured habitat component described variability at broader scales than the pure spatial component. Our results suggest that stochastic processes and spatially structuring processes of community dynamics, such as dispersal limitation and habitat association, contributed jointly to explain species composition and richness at the Sinharaja forest, but their relative importance changed with scale and life stage. Species assembly at the local scale was more strongly impacted by stochasticity, whereas the signal of habitat was stronger at the 50-m scale where plant-scale stochasticity is averaged out. Recent research points to an emerging consensus on the relative contribution of stochasticity, habitat, and spatial processes in governing community assembly, but how these components change with life stage, and how this is influenced by sample size, remains to be explored.

@Article{Rejou-Mechain2014,
  author   = {R{\'{e}}jou-M{\'{e}}chain, M. and Muller-Landau, H. C. and Detto, M. and Thomas, S. C. and {Le Toan}, T. and Saatchi, S. S. and Barreto-Silva, J. S. and Bourg, N. A. and Bunyavejchewin, S. and Butt, N. and Brockelman, W. Y. and Cao, M. and C{\'{a}}rdenas, D. and Chiang, J. M. and Chuyong, G. B. and Clay, K. and Condit, R. and Dattaraja, H. S. and Davies, S. J. and Duque, A. and Esufali, S. and Ewango, C. and Fernando, R. H.S. and Fletcher, C. D. and {N. Gunatilleke}, I. A.U. and Hao, Z. and Harms, K. E. and Hart, T. B. and H{\'{e}}rault, B. and Howe, R. W. and Hubbell, S. P. and Johnson, D. J. and Kenfack, D. and Larson, A. J. and Lin, L. and Lin, Y. and Lutz, J. A. and Makana, J. R. and Malhi, Y. and Marthews, T. R. and Mcewan, R. W. and Mcmahon, S. M. and Mcshea, W. J. and Muscarella, R. and Nathalang, A. and Noor, N. S.M. and Nytch, C. J. and Oliveira, A. A. and Phillips, R. P. and Pongpattananurak, N. and Punchi-Manage, R. and Salim, R. and Schurman, J. and Sukumar, R. and Suresh, H. S. and Suwanvecho, U. and Thomas, D. W. and Thompson, J. and Ur{\'{i}}arte, M. and Valencia, R. and Vicentini, A. and Wolf, A. T. and Yap, S. and Yuan, Z. and Zartman, C. E. and Zimmerman, J. K. and Chave, J.},
  journal  = {Biogeosciences},
  title    = {{Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks}},
  year     = {2014},
  issn     = {17264189},
  number   = {23},
  pages    = {6827--6840},
  volume   = {11},
  abstract = {Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation). Though broad-scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8–50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass density (AGBD in Mg ha–1) at spatial scales ranging from 5 to 250 m (0.025–6.25 ha), and to evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that local spatial variability in AGBD is large for standard plot sizes, averaging 46.3{\%} for replicate 0.1 ha subplots within a single large plot, and 16.6{\%} for 1 ha subplots. AGBD showed weak spatial autocorrelation at distances of 20–400 m, with autocorrelation higher in sites with higher topographic variability and statistically significant in half of the sites. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGBD leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with standard statistical methods. Our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.},
  comment  = {public},
  doi      = {10.5194/bg-11-6827-2014},
  groups   = {Jana:1},
  isbn     = {1726-4170},
}

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation). Though broad-scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8–50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass density (AGBD in Mg ha–1) at spatial scales ranging from 5 to 250 m (0.025–6.25 ha), and to evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that local spatial variability in AGBD is large for standard plot sizes, averaging 46.3% for replicate 0.1 ha subplots within a single large plot, and 16.6% for 1 ha subplots. AGBD showed weak spatial autocorrelation at distances of 20–400 m, with autocorrelation higher in sites with higher topographic variability and statistically significant in half of the sites. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGBD leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with standard statistical methods. Our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.

@Article{Ritter2014,
  author   = {Ritter, Tim and Saborowski, Joachim},
  title    = {{Efficient integration of a deadwood inventory into an existing forest inventory carried out as two-phase sampling for stratification}},
  journal  = {Forestry},
  year     = {2014},
  volume   = {87},
  number   = {4},
  pages    = {571--581},
  issn     = {14643626},
  url_pdf  = {http://uni-goettingen.de/de/document/download/49134189e3d50f9ab8b0f1f5ca3f9023.pdf/Ritter_Saborowski_2014_Forestry_Efficient_integration_deadwood_inventory.pdf},
  abstract = {Deadwood is an important component of many ecosystems and plays a major role for biodiversity, soil protection and carbon sequestration. Despite its high ecological value, deadwood is not included in the main focus of traditional forest inventories. The sampling designs of these inventories are therefore not optimal for deadwood sampling. However, in recent years, interest in non-timber aspects of forest structure and demand for multipurpose forest inventories has increased. Drawing on the example of a German state forest district inventory, we suggest an efficient integration of point transect and line intersect sampling of deadwood into an existing forest inventory, carried out as two-phase sampling for stratification. Compared with fixed area sampling, efficiency is tremendously increased using point transect sampling for standing deadwood and line intersect sampling for coarse woody debris.},
  comment  = {public},
  doi      = {10.1093/forestry/cpu016},
}

Deadwood is an important component of many ecosystems and plays a major role for biodiversity, soil protection and carbon sequestration. Despite its high ecological value, deadwood is not included in the main focus of traditional forest inventories. The sampling designs of these inventories are therefore not optimal for deadwood sampling. However, in recent years, interest in non-timber aspects of forest structure and demand for multipurpose forest inventories has increased. Drawing on the example of a German state forest district inventory, we suggest an efficient integration of point transect and line intersect sampling of deadwood into an existing forest inventory, carried out as two-phase sampling for stratification. Compared with fixed area sampling, efficiency is tremendously increased using point transect sampling for standing deadwood and line intersect sampling for coarse woody debris.

@Article{Saefken2014,
  author   = {Saefken, Benjamin and Kneib, Thomas and van Waveren, Clara-Sophie and Greven, Sonja},
  title    = {{A unifying approach to the estimation of the conditional Akaike information in generalized linear mixed models}},
  journal  = {Electronic Journal of Statistics},
  year     = {2014},
  volume   = {8},
  number   = {1},
  pages    = {201--225},
  issn     = {1935-7524},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ca721ac3ba1070babfd2a5ef486227bc.pdf/Saefken_et_al_2014_Electronic_Journal_Statistics_A_unifying_approach_to_the_estimation_of_the_conditional_Akaike_information_in%20GLMM.pdf},
  abstract = {The conditional Akaike information criterion, AIC, has been frequently used for model selection in linear mixed models. We develop a general framework for the calculation of the conditional AIC for different exponential family distributions. This unified framework incorporates the conditional AIC for the Gaussian case, gives a new justification for Poisson distributed data and yields a new conditional AIC for exponentially distributed responses but cannot be applied to the binomial and gamma distributions. The proposed conditional Akaike information criteria are unbiased for finite samples, do not rely on a particular estimation method and do not assume that the variance-covariance matrix of the random effects is known. The theoretical results are investigated in a simulation study. The practical use of the method is illustrated by application to a data set on tree growth.},
  comment  = {public},
  doi      = {10.1214/14-EJS881},
  isbn     = {1935-7524},
  url      = {http://projecteuclid.org/euclid.ejs/1393510264},
}

The conditional Akaike information criterion, AIC, has been frequently used for model selection in linear mixed models. We develop a general framework for the calculation of the conditional AIC for different exponential family distributions. This unified framework incorporates the conditional AIC for the Gaussian case, gives a new justification for Poisson distributed data and yields a new conditional AIC for exponentially distributed responses but cannot be applied to the binomial and gamma distributions. The proposed conditional Akaike information criteria are unbiased for finite samples, do not rely on a particular estimation method and do not assume that the variance-covariance matrix of the random effects is known. The theoretical results are investigated in a simulation study. The practical use of the method is illustrated by application to a data set on tree growth.

@Article{VonLupke2014,
  author   = {von L{\"{u}}pke, Nikolas and Saborowski, Joachim},
  title    = {{Combining double sampling for stratification and cluster sampling to a three-level sampling design for continuous forest inventories}},
  journal  = {European Journal of Forest Research},
  year     = {2014},
  volume   = {133},
  number   = {1},
  pages    = {89--100},
  issn     = {16124669},
  url_pdf  = {http://uni-goettingen.de/de/document/download/c5c6f0125f23977b2fcd67b18c2056bc.pdf/2014_EJFR_vLuepkeSab.pdf},
  abstract = {We extend the well-known double sampling for stratification sampling$\backslash$nscheme by cluster subsampling to a three-level design and present$\backslash$ncorresponding estimators based on the infinite population approach$\backslash$nin the first phase. After stratification of the sample points (phase$\backslash$nI), a second-phase sample is drawn independently among the first-phase$\backslash$npoints within each stratum. On level III, clusters are formed of$\backslash$nthose phase II points and a sample of clusters is finally drawn without$\backslash$nreplacement. We used the forest planning units compartment and subdistrict$\backslash$nas clusters and moreover formed clusters with a heuristic for the$\backslash$nvehicle routing problem. The precision of the new estimator was compared$\backslash$nto that achieved with classical double sampling for stratification$\backslash$nin a case study. The results indicate that the expected increase$\backslash$nin sampling errors caused by clustering cannot be compensated by$\backslash$nthe reduced inventory costs under the conditions given in the case$\backslash$nstudy.},
  comment  = {public},
  doi      = {10.1007/s10342-013-0743-9},
  keywords = {Cluster sampling,Continuous forest inventory,Double sampling for stratification,Infinite population approach},
}

We extend the well-known double sampling for stratification sampling$\$nscheme by cluster subsampling to a three-level design and present$\$ncorresponding estimators based on the infinite population approach$\$nin the first phase. After stratification of the sample points (phase$\$nI), a second-phase sample is drawn independently among the first-phase$\$npoints within each stratum. On level III, clusters are formed of$\$nthose phase II points and a sample of clusters is finally drawn without$\$nreplacement. We used the forest planning units compartment and subdistrict$\$nas clusters and moreover formed clusters with a heuristic for the$\$nvehicle routing problem. The precision of the new estimator was compared$\$nto that achieved with classical double sampling for stratification$\$nin a case study. The results indicate that the expected increase$\$nin sampling errors caused by clustering cannot be compensated by$\$nthe reduced inventory costs under the conditions given in the case$\$nstudy.

@Conference{Salecker2014,
  author    = {Salecker, Jan and Meyer, Katrin M and Wiegand, Kerstin},
  booktitle = {Poster at GfÖ annual meeting 2014, Hildesheim, Germany},
  title     = {{Black Poplar Population Persistence}},
  year      = {2014},
  groups    = {Jana:1},
  owner     = {Jan},
  timestamp = {2018.01.25},
}

@Article{Bauling2013,
  author  = {Bauling, S. and Saborowski, J. and R{\"{u}}he, F.},
  title   = {{Sch{\"{a}}tzung der Rotwilddichte (Cervus elaphus L.) im Solling mit der Age-at-Harvest-Methode}},
  journal = {Forstarchiv},
  year    = {2013},
  volume  = {84},
  pages   = {13--23},
  url_pdf = {http://uni-goettingen.de/de/document/download/27854ea80d5f62c9bd1d5d130ea0c20b.pdf/2013_Forstarchiv_Bauling_etal.pdf},
  comment = {public},
  doi     = {10.4432/0300-4112-84-13},
}

@Article{Bauling2013a,
  author  = {Bauling, S. and Saborowski, J. and R{\"{u}}he, F.},
  title   = {{Das Rotwild (Cervus elaphus L.) im Solling: Dynamik, Produktivit{\"{a}}t, Mortalit{\"{a}}t und Struktur von 1981 bis 1991}},
  journal = {Forstarchiv},
  year    = {2013},
  volume  = {84},
  pages   = {131--143},
  url_pdf = {http://uni-goettingen.de/de/document/download/1fdca72f633969b319d12c751fa39509.pdf/2013_Forstarchiv_Bauling%20et%20al%202.pdf},
  comment = {public},
  doi     = {10.4432/0300-4112-84-131},
}

@Article{Byun2013,
  author   = {Byun, Jae Gyun and Lee, Woo Kyun and Kim, Moonil and Kwak, Doo Ahn and Kwak, Hanbin and Park, Taejin and Byun, Woo Hyuk and Son, Yowhan and Choi, Jung Kee and Lee, Young Jin and Saborowski, Joachim and Chung, Dong Jun and Jung, Jin Hyun},
  title    = {{Radial growth response of Pinus densiflora and Quercus spp. to topographic and climatic factors in South Korea}},
  journal  = {Journal of Plant Ecology},
  year     = {2013},
  volume   = {6},
  number   = {5},
  pages    = {380--392},
  issn     = {17529921},
  url_pdf  = {http://uni-goettingen.de/de/document/download/c7786d9cbd499a69c9a27fd282fef0ef.pdf/2013_J%20Plant%20Ecol_Byun_etal.pdf},
  abstract = {This study aimed to develop radial growth models and to predict the$\backslash$npotential spatial distribution of Pinus densiflora (Japanese red pine)$\backslash$nand Quercus spp. (Oaks) in South Korea, considering topographic and$\backslash$nclimatic factors.$\backslash$nWe used a dataset of diameter at breast height and radial growth$\backslash$nestimates of individual trees, topographic and climatic factors in$\backslash$nsystematic sample plots distributed over the whole of South Korea. On$\backslash$nthe basis that radial growth is attributed primarily to tree age, we$\backslash$ndeveloped a radial growth model employing tree age as an explanatory$\backslash$nvariable. We estimated standard growth (SG), defined as radial growth of$\backslash$nthe tree at age 30, to eliminate the influence of tree age on radial$\backslash$ngrowth. In addition, SG estimates including the Topographic Wetness$\backslash$nIndex, temperature and precipitation were calculated by the Generalized$\backslash$nAdditive Model.$\backslash$nAs a result of variogram analysis of SG, we found spatial$\backslash$nautocorrelation between SG, topographic and climatic factors.$\backslash$nIncremental temperature had negative impacts on radial growth of P.$\backslash$ndensiflora and positive impacts on that of Quercus spp. Precipitation$\backslash$nwas associated with positive effects on both tree species. Based on the$\backslash$nmodel, we found that radial growth of P. densiflora would be more$\backslash$nvulnerable than that of Quercus spp. to climatic factors. Through$\backslash$nsimulation with the radial growth model, it was predicted that P.$\backslash$ndensiflora stands would be gradually replaced with Quercus spp. stands$\backslash$nin eastern coastal and southern regions of South Korea in the future.$\backslash$nThe models developed in this study will be helpful for understanding the$\backslash$nimpact of climatic factors on tree growth and for predicting changes in$\backslash$ndistribution of P. densiflora and Quercus spp. due to climate change in$\backslash$nSouth Korea.},
  comment  = {public},
  doi      = {10.1093/jpe/rtt001},
  isbn     = {1752-9921},
  keywords = {climate change,forest-cover change,general additive modelclimatic factors,standard radial growth},
}

This study aimed to develop radial growth models and to predict the$\$npotential spatial distribution of Pinus densiflora (Japanese red pine)$\$nand Quercus spp. (Oaks) in South Korea, considering topographic and$\$nclimatic factors.$\$nWe used a dataset of diameter at breast height and radial growth$\$nestimates of individual trees, topographic and climatic factors in$\$nsystematic sample plots distributed over the whole of South Korea. On$\$nthe basis that radial growth is attributed primarily to tree age, we$\$ndeveloped a radial growth model employing tree age as an explanatory$\$nvariable. We estimated standard growth (SG), defined as radial growth of$\$nthe tree at age 30, to eliminate the influence of tree age on radial$\$ngrowth. In addition, SG estimates including the Topographic Wetness$\$nIndex, temperature and precipitation were calculated by the Generalized$\$nAdditive Model.$\$nAs a result of variogram analysis of SG, we found spatial$\$nautocorrelation between SG, topographic and climatic factors.$\$nIncremental temperature had negative impacts on radial growth of P.$\$ndensiflora and positive impacts on that of Quercus spp. Precipitation$\$nwas associated with positive effects on both tree species. Based on the$\$nmodel, we found that radial growth of P. densiflora would be more$\$nvulnerable than that of Quercus spp. to climatic factors. Through$\$nsimulation with the radial growth model, it was predicted that P.$\$ndensiflora stands would be gradually replaced with Quercus spp. stands$\$nin eastern coastal and southern regions of South Korea in the future.$\$nThe models developed in this study will be helpful for understanding the$\$nimpact of climatic factors on tree growth and for predicting changes in$\$ndistribution of P. densiflora and Quercus spp. due to climate change in$\$nSouth Korea.

@Article{Chisholm2013,
  author   = {Chisholm, Ryan A. and Muller-Landau, Helene C. and {Abdul Rahman}, Kassim and Bebber, Daniel P. and Bin, Yue and Bohlman, Stephanie A. and Bourg, Norman A. and Brinks, Joshua and Bunyavejchewin, Sarayudh and Butt, Nathalie and Cao, Honglin and Cao, Min and C{\'{a}}rdenas, Dairon and Chang, Li Wan and Chiang, Jyh Min and Chuyong, George and Condit, Richard and Dattaraja, Handanakere S. and Davies, Stuart and Duque, Alvaro and Fletcher, Christine and Gunatilleke, Nimal and Gunatilleke, Savitri and Hao, Zhanqing and Harrison, Rhett D. and Howe, Robert and Hsieh, Chang Fu and Hubbell, Stephen P. and Itoh, Akira and Kenfack, David and Kiratiprayoon, Somboon and Larson, Andrew J. and Lian, Juyu and Lin, Dunmei and Liu, Haifeng and Lutz, James A. and Ma, Keping and Malhi, Yadvinder and Mcmahon, Sean and Mcshea, William and Meegaskumbura, Madhava and {Mohd. Razman}, Salim and Morecroft, Michael D. and Nytch, Christopher J. and Oliveira, Alexandre and Parker, Geoffrey G. and Pulla, Sandeep and Punchi-Manage, Ruwan and Romero-Saltos, Hugo and Sang, Weiguo and Schurman, Jon and Su, Sheng Hsin and Sukumar, Raman and Sun, I. Fang and Suresh, Hebbalalu S. and Tan, Sylvester and Thomas, Duncan and Thomas, Sean and Thompson, Jill and Valencia, Renato and Wolf, Amy and Yap, Sandra and Ye, Wanhui and Yuan, Zuoqiang and Zimmerman, Jess K.},
  title    = {{Scale-dependent relationships between tree species richness and ecosystem function in forests}},
  journal  = {Journal of Ecology},
  year     = {2013},
  volume   = {101},
  number   = {5},
  pages    = {1214--1224},
  issn     = {00220477},
  url_pdf  = {http://uni-goettingen.de/de/document/download/02d119fc5ac7b2d7e0c2b6142d45eec8.pdf/Chisholm_et_al_2013_JOURNAL_OF_ECOLOGY_scale-dependent_relationships_tree_species_richness_ecosystem_function.pdf},
  abstract = {1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which repre- sent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8–50 ha from across the world. The data were collected using standardized protocols, obvi- ating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to pro- ductivity and biomass within plots, with a doubling of species richness corresponding to an average 48{\%} increase in productivity and 53{\%} increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corre- sponded to a 5{\%} increase in productivity and 7{\%} increase in biomass. Productivity and biomass were them- selves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productiv- ity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consis- tent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in forest conservation policy and management.},
  comment  = {public},
  doi      = {10.1111/1365-2745.12132},
  isbn     = {0022-0477},
  keywords = {Biodiversity,Biomass,Complementarity,Determinants of plant community diversity and stru,Productivity,Sampling effects,Species diversity,Trees},
}

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which repre- sent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8–50 ha from across the world. The data were collected using standardized protocols, obvi- ating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to pro- ductivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corre- sponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were them- selves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productiv- ity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consis- tent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in forest conservation policy and management.

@Article{Gossner2013,
  author   = {Gossner, Martin M. and Getzin, Stephan and Lange, Markus and Pa{\v{s}}ali{\'{c}}, Esther and T{\"{u}}rke, Manfred and Wiegand, Kerstin and Weisser, Wolfgang W.},
  title    = {{The importance of heterogeneity revisited from a multiscale and multitaxa approach}},
  journal  = {Biological Conservation},
  year     = {2013},
  volume   = {166},
  pages    = {212--220},
  issn     = {00063207},
  url_pdf  = {http://uni-goettingen.de/de/document/download/60b146a291c0565ea39d8ac5143ff05e.pdf/Gossner-2013-The%20importance%20of%20he.pdf},
  abstract = {The importance of spatial scale for ??-diversity has been shown in several studies, but it is unclear how spatial diversity patterns correlate among different organismic groups. We studied spatial diversity organization of plants and several trophic guilds of beetles in beech-dominated forests in two regions of Germany to test whether different trophic guilds are organized independently in space. We applied multiplicative diversity partitioning using a nested hierarchical design of four increasingly broader spatial levels (subplot, plot, forest class, region) and tested for correlations among trophic guilds by using Pearson product moment correlations and Mantel-tests. We observed similar general diversity patterns at different trophic guilds showing a high contribution of ??-diversity to total ??-diversity and found ??-diversity to be higher at different spatial scales and ??-diversity to be lower than expected by random distributions of individuals. Results, however, partly depended on the weighting of rare and abundant species. Beta-diversity in our study was caused mainly by species spatial turnover rather than by nestedness. Correlations of ??-diversity between trophic guilds were low whereas correlations of ??-diversity above subplot level were high. Importantly, more strongly connected trophic guilds revealed not generally stronger relationships than less strongly connected guilds. Three important implications for conservation can be deduced from our results: (1) heterogeneity of beech forests at different spatial scales should be supported in conservation strategies to enhance biodiversity and related functions; (2) the observed high importance of spatial turnover in relation to nestedness implies a concentration of conservation efforts to a large number of not necessarily the richest sites, and (3) recommendation for particular conservation strategies (e.g. selection of priority sites for conservation at regional scale) based on single indicator taxa or functional guild is difficult because of the varied response of the species in our study. ?? 2013 Elsevier Ltd.},
  comment  = {public},
  doi      = {10.1016/j.biocon.2013.06.033},
  isbn     = {00063207},
  keywords = {Beetles,Ecosystem function,Multiplicative diversity partitioning,Q-Metric,Spatial scale,Species turnover},
}

The importance of spatial scale for ??-diversity has been shown in several studies, but it is unclear how spatial diversity patterns correlate among different organismic groups. We studied spatial diversity organization of plants and several trophic guilds of beetles in beech-dominated forests in two regions of Germany to test whether different trophic guilds are organized independently in space. We applied multiplicative diversity partitioning using a nested hierarchical design of four increasingly broader spatial levels (subplot, plot, forest class, region) and tested for correlations among trophic guilds by using Pearson product moment correlations and Mantel-tests. We observed similar general diversity patterns at different trophic guilds showing a high contribution of ??-diversity to total ??-diversity and found ??-diversity to be higher at different spatial scales and ??-diversity to be lower than expected by random distributions of individuals. Results, however, partly depended on the weighting of rare and abundant species. Beta-diversity in our study was caused mainly by species spatial turnover rather than by nestedness. Correlations of ??-diversity between trophic guilds were low whereas correlations of ??-diversity above subplot level were high. Importantly, more strongly connected trophic guilds revealed not generally stronger relationships than less strongly connected guilds. Three important implications for conservation can be deduced from our results: (1) heterogeneity of beech forests at different spatial scales should be supported in conservation strategies to enhance biodiversity and related functions; (2) the observed high importance of spatial turnover in relation to nestedness implies a concentration of conservation efforts to a large number of not necessarily the richest sites, and (3) recommendation for particular conservation strategies (e.g. selection of priority sites for conservation at regional scale) based on single indicator taxa or functional guild is difficult because of the varied response of the species in our study. ?? 2013 Elsevier Ltd.

@Article{Hol2013,
  author   = {Hol, W. H. G. and {De Boer}, Wietse and Termorshuizen, Aad J. and Meyer, Katrin M. and Schneider, Johannes H.M. and van der Putten, Wim H. and van Dam, Nicole M.},
  title    = {{Heterodera schachtii Nematodes Interfere with Aphid-Plant Relations on Brassica oleracea}},
  journal  = {Journal of Chemical Ecology},
  year     = {2013},
  volume   = {39},
  number   = {9},
  pages    = {1193--1203},
  issn     = {00980331},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d37187604ee73bd1a0128bb7076df1d7.pdf/Hol_et_al_2013_JChemEcol.pdf},
  abstract = {Aboveground and belowground herbivore species modify plant defense responses differently. Simultaneous attack can lead to non-additive effects on primary and secondary metabolite composition in roots and shoots. We previously found that aphid (Brevicoryne brassicae) population growth on Brassica oleracea was reduced on plants that were infested with nematodes (Heterodera schachtii) prior (4 weeks) to aphid infestation. Here, we examined how infection with root-feeding nematodes affected primary and secondary metabolites in the host plant and whether this could explain the increase in aphid doubling time from 3.8 to 6.7 days. We hypothesized that the effects of herbivores on plant metabolites would depend on the presence of the other herbivore and that nematode-induced changes in primary metabolites would correlate with reduced aphid performance. Total glucosinolate concentration in the leaves was not affected by nematode presence, but the composition of glucosinolates shifted, as gluconapin concentrations were reduced, while gluconapoleiferin concentrations increased in plants exposed to nematodes. Aphid presence increased 4-methoxyglucobrassicin concentrations in leaves, which correlated positively with the number of aphids per plant. Nematodes decreased amino acid and sugar concentrations in the phloem. Aphid population doubling time correlated negatively with amino acids and glucosinolate levels in leaves, whereas these correlations were non-significant when nematodes were present. In conclusion, the effects of an herbivore on plant metabolites were independent of the presence of another herbivore. Nematode presence reduced aphid population growth and disturbed feeding relations between plants and aphids.},
  comment  = {public},
  doi      = {10.1007/s10886-013-0338-4},
  isbn     = {1573-1561 (Electronic)$\backslash$n0098-0331 (Linking)},
  keywords = {Brassica,Brevicoryne,EDTA,Glucosinolates,Heterodera,Phloem},
  pmid     = {24014097},
}

Aboveground and belowground herbivore species modify plant defense responses differently. Simultaneous attack can lead to non-additive effects on primary and secondary metabolite composition in roots and shoots. We previously found that aphid (Brevicoryne brassicae) population growth on Brassica oleracea was reduced on plants that were infested with nematodes (Heterodera schachtii) prior (4 weeks) to aphid infestation. Here, we examined how infection with root-feeding nematodes affected primary and secondary metabolites in the host plant and whether this could explain the increase in aphid doubling time from 3.8 to 6.7 days. We hypothesized that the effects of herbivores on plant metabolites would depend on the presence of the other herbivore and that nematode-induced changes in primary metabolites would correlate with reduced aphid performance. Total glucosinolate concentration in the leaves was not affected by nematode presence, but the composition of glucosinolates shifted, as gluconapin concentrations were reduced, while gluconapoleiferin concentrations increased in plants exposed to nematodes. Aphid presence increased 4-methoxyglucobrassicin concentrations in leaves, which correlated positively with the number of aphids per plant. Nematodes decreased amino acid and sugar concentrations in the phloem. Aphid population doubling time correlated negatively with amino acids and glucosinolate levels in leaves, whereas these correlations were non-significant when nematodes were present. In conclusion, the effects of an herbivore on plant metabolites were independent of the presence of another herbivore. Nematode presence reduced aphid population growth and disturbed feeding relations between plants and aphids.

@Article{Husmann2013,
  author  = {Husmann, K. and Saborowski, J. and Hapla, F.},
  title   = {{Ursachenanalyse der Ringsch{\"{a}}le bei Edelkastanie (Castanea sativa [Mill.]) in Rheinland-Pfalz}},
  journal = {Forstarchiv},
  year    = {2013},
  volume  = {84},
  pages   = {107--118},
  url_pdf = {http://uni-goettingen.de/de/document/download/0231f82daa55becb388fc1c8438318ec.pdf/2013_Forstarchiv_Husmann_etal.pdf},
  comment = {public},
  doi     = {10.4432/0300-4112-84-107},
}

@Article{Jeltsch2013,
  author   = {Jeltsch, Florian and Blaum, Niels and Brose, Ulrich and Chipperfield, Joseph D. and Clough, Yann and Farwig, Nina and Geissler, Katja and Graham, Catherine H. and Grimm, Volker and Hickler, Thomas and Huth, Andreas and May, Felix and Meyer, Katrin M. and Pagel, J{\"{o}}rn and Reineking, Bj{\"{o}}rn and Rillig, Matthias C. and Shea, Katriona and Schurr, Frank M. and Schr{\"{o}}der, Boris and Tielb{\"{o}}rger, Katja and Weiss, Lina and Wiegand, Kerstin and Wiegand, Thorsten and Wirth, Christian and Zurell, Damaris},
  title    = {{How can we bring together empiricists and modellers in functional biodiversity research?}},
  journal  = {Basic and Applied Ecology},
  year     = {2013},
  volume   = {14},
  number   = {2},
  pages    = {93--101},
  issn     = {14391791},
  url_pdf  = {http://uni-goettingen.de/de/document/download/aa5897d870058ae8a37dc36e5746bd70.pdf/Jeltsch_et_al_2013_BAE_bring_together_empiricists_modellers_functional_biodiversity_research.pdf},
  abstract = {Improving our understanding of biodiversity and ecosystem functioning and our capacity to inform ecosystem management requires an integrated framework for functional biodiversity research (FBR). However, adequate integration among empirical approaches (monitoring and experimental) and modelling has rarely been achieved in FBR. We offer an appraisal of the issues involved and chart a course towards enhanced integration. A major element of this path is the joint orientation towards the continuous refinement of a theoretical framework for FBR that links theory testing and generalization with applied research oriented towards the conservation of biodiversity and ecosystem functioning. We further emphasize existing decision-making frameworks as suitable instruments to practically merge these different aims of FBR and bring them into application. This integrated framework requires joint research planning, and should improve communication and stimulate collaboration between modellers and empiricists, thereby overcoming existing reservations and prejudices. The implementation of this integrative research agenda for FBR requires an adaptation in most national and international funding schemes in order to accommodate such joint teams and their more complex structures and data needs. {\textcopyright} 2013 Gesellschaft f{\"{u}}r {\"{O}}kologie.},
  comment  = {public},
  doi      = {10.1016/j.baae.2013.01.001},
  isbn     = {1439-1791},
  keywords = {Biodiversity experiments,Biodiversity theory,Conservation management,Decision-making,Ecosystem functions and services,Forecasting,Functional traits,Global change,Interdisciplinarity,Monitoring programmes},
}

Improving our understanding of biodiversity and ecosystem functioning and our capacity to inform ecosystem management requires an integrated framework for functional biodiversity research (FBR). However, adequate integration among empirical approaches (monitoring and experimental) and modelling has rarely been achieved in FBR. We offer an appraisal of the issues involved and chart a course towards enhanced integration. A major element of this path is the joint orientation towards the continuous refinement of a theoretical framework for FBR that links theory testing and generalization with applied research oriented towards the conservation of biodiversity and ecosystem functioning. We further emphasize existing decision-making frameworks as suitable instruments to practically merge these different aims of FBR and bring them into application. This integrated framework requires joint research planning, and should improve communication and stimulate collaboration between modellers and empiricists, thereby overcoming existing reservations and prejudices. The implementation of this integrative research agenda for FBR requires an adaptation in most national and international funding schemes in order to accommodate such joint teams and their more complex structures and data needs. © 2013 Gesellschaft für Ökologie.

@Article{Punchi-Manage2013,
  author   = {Punchi-Manage, Ruwan and Getzin, Stephan and Wiegand, Thorsten and Kanagaraj, Rajapandian and {Savitri Gunatilleke}, C. V. and {Nimal Gunatilleke}, I. A U and Wiegand, Kerstin and Huth, Andreas},
  title    = {{Effects of topography on structuring local species assemblages in a Sri Lankan mixed dipterocarp forest}},
  journal  = {Journal of Ecology},
  year     = {2013},
  volume   = {101},
  number   = {1},
  pages    = {149--160},
  issn     = {00220477},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d4a4a0ab0bde7bc595a316ed9e1f7b1b.pdf/Punchi-Manage_et_al_(2013)_J_OF_ECOL_Effects_of_topography.pdf},
  abstract = {* One of the primary goals in community ecology is to determine the relative importance of processes and mechanisms that control biodiversity. Here, we examined habitat-driven species assemblages and species distribution patterns as well as their temporal variations for three life stages of two censuses of a 25-ha mixed dipterocarp forest at Sinharaja (Sri Lanka). * Our general objective was to find out whether the species assemblages and associated habitat types changed with life stage, spatial scale and species attributes. We also analyse whether the habitat types were related to certain indicator species. Habitat types were determined with multivariate regression tree analyses driven by topographic variables. * We found species assemblages associated with five distinct habitat types that appeared consistently for all life stages of the two censuses. These habitats were related to ridge-valley gradients and a pronounced contrast in south-west versus north-east aspect. Habitat-driven structuring was weak at the recruit stage but strong in the juvenile and adult stages. The species assemblage variance explained by topographic variables for different life stages ranged between 10{\%} for recruits and 23{\%} for juveniles. * The species assemblages determined for different spatial scales (10, 20, 50 m) showed similar habitat partitioning, but the variance explained by the topographic variables increased in all life stages with spatial scale. This could be due to the homogenizing effect of topographic variables at the larger scales and unaccounted environmental variation at the smaller scales. The number of indicator species identified in the two censuses was higher in the juvenile stage than in the adult stage, and nearly all indicator species in the adult stage were also indicator species in the juvenile stage. * Synthesis. Our study showed that approximately 75{\%} of the variance in local species composition is unexplained. This may be due to spatially structured processes such as dispersal limitation, unaccounted biotic and abiotic environmental variables, and stochastic effects, but only 25{\%} were due to topographic habitat association. Although the pronounced ridge-valley gradient and contrast of south-west versus north-east aspect created consistent habitats, our results suggest that local species assemblages at Sinharaja forest are jointly shaped by neutral and niche processes.},
  comment  = {public},
  doi      = {10.1111/1365-2745.12017},
  isbn     = {1365-2745},
  keywords = {Determinants of plant community diversity and stru,Dispersal limitation,Habitat association,Indicator species,Multivariate regression tree,Neutral theory,Sinharaja forest,Spatial scale,Topography},
  pmid     = {24669731},
}

* One of the primary goals in community ecology is to determine the relative importance of processes and mechanisms that control biodiversity. Here, we examined habitat-driven species assemblages and species distribution patterns as well as their temporal variations for three life stages of two censuses of a 25-ha mixed dipterocarp forest at Sinharaja (Sri Lanka). * Our general objective was to find out whether the species assemblages and associated habitat types changed with life stage, spatial scale and species attributes. We also analyse whether the habitat types were related to certain indicator species. Habitat types were determined with multivariate regression tree analyses driven by topographic variables. * We found species assemblages associated with five distinct habitat types that appeared consistently for all life stages of the two censuses. These habitats were related to ridge-valley gradients and a pronounced contrast in south-west versus north-east aspect. Habitat-driven structuring was weak at the recruit stage but strong in the juvenile and adult stages. The species assemblage variance explained by topographic variables for different life stages ranged between 10% for recruits and 23% for juveniles. * The species assemblages determined for different spatial scales (10, 20, 50 m) showed similar habitat partitioning, but the variance explained by the topographic variables increased in all life stages with spatial scale. This could be due to the homogenizing effect of topographic variables at the larger scales and unaccounted environmental variation at the smaller scales. The number of indicator species identified in the two censuses was higher in the juvenile stage than in the adult stage, and nearly all indicator species in the adult stage were also indicator species in the juvenile stage. * Synthesis. Our study showed that approximately 75% of the variance in local species composition is unexplained. This may be due to spatially structured processes such as dispersal limitation, unaccounted biotic and abiotic environmental variables, and stochastic effects, but only 25% were due to topographic habitat association. Although the pronounced ridge-valley gradient and contrast of south-west versus north-east aspect created consistent habitats, our results suggest that local species assemblages at Sinharaja forest are jointly shaped by neutral and niche processes.

@Article{Ritter2013,
  author   = {Ritter, Tim and Nothdurft, Arne and Saborowski, Joachim},
  title    = {{Correcting the nondetection bias of angle count sampling}},
  journal  = {Canadian Journal of Forest Research},
  year     = {2013},
  volume   = {43},
  number   = {January},
  pages    = {344--354},
  issn     = {0045-5067},
  url_pdf  = {http://uni-goettingen.de/de/document/download/3c0188500934b105bca9661b33555343.pdf/2013_CanadJFR_Ritter_etal.pdf},
  abstract = {The well-known angle count sampling (ACS) has proved to be an efficient sampling technique and has been applied in forest inventories for many decades. However, ACS assumes total visibility of objects; any violation of this assumption leads to a nondetection bias. We present a novel approach, in which the theory of distance sampling is adapted to traditional ACS to correct for the nondetection bias. Two new estimators were developed based on expanding design-based inclusion probabilities by model-based estimates of the detection probabilities. The new estimators were evaluated in a simulation study as well as in a real forest inventory. It is shown that the nondetection bias of the traditional estimator is up to −52.5{\%}, whereas the new estimators are approximately unbiased},
  comment  = {public},
  doi      = {10.1139/cjfr-2012-0408},
}

The well-known angle count sampling (ACS) has proved to be an efficient sampling technique and has been applied in forest inventories for many decades. However, ACS assumes total visibility of objects; any violation of this assumption leads to a nondetection bias. We present a novel approach, in which the theory of distance sampling is adapted to traditional ACS to correct for the nondetection bias. Two new estimators were developed based on expanding design-based inclusion probabilities by model-based estimates of the detection probabilities. The new estimators were evaluated in a simulation study as well as in a real forest inventory. It is shown that the nondetection bias of the traditional estimator is up to −52.5%, whereas the new estimators are approximately unbiased

@Article{Ritter2013a,
  author  = {Ritter, Tim and Saborowski, Joachim},
  title   = {{Probleme der Pr{\"{a}}zisionssch{\"{a}}tzung beim Point Transect Sampling von Totholz}},
  journal = {Deutscher Verband Forstlicher Forschungsanstalten, Sektion Forstliche Biometrie und Informatik - Die Gr{\"{u}}ne Reihe (ISSN 1860-4064)},
  year    = {2013},
  volume  = {23},
  pages   = {107--122},
  url_pdf = {http://uni-goettingen.de/de/document/download/483c5422ee4b7b29de745bd0335a9863.pdf/2013_ritter_saboro_gruenereihe23.pdf},
  comment = {public},
}

@Article{Sabatier2013,
  author   = {Sabatier, Rodolphe and Meyer, Katrin and Wiegand, Kerstin and Clough, Yann},
  journal  = {Basic and Applied Ecology},
  title    = {{Non-linear effects of pesticide application on biodiversity-driven ecosystem services and disservices in a cacao agroecosystem: A modeling study}},
  year     = {2013},
  issn     = {14391791},
  number   = {2},
  pages    = {115--125},
  volume   = {14},
  abstract = {Growing concerns have been raised regarding the effects of disturbance due to agricultural practices on associate biodiversity and on the ecosystem services that biodiversity provides. Surprisingly little is known about the effects of such disturbances on complex agroecosystems with multiple interacting species. The aim of this study was to assess the effects of management by pesticide spraying on the productive outputs and the ecological functioning of a cacao agroecosystem. We built a mechanistic dynamic model including the dynamics of the crop, a pest (Cacao Pod Borer, Conopomorpha cramerella) and two beneficial insects: a hymenopteran egg-parasitoid and a ceratopogonid pollinator. Using this model, we tested the effects of a range of pesticide types characterized by their impacts on both the Cacao Pod Borer and the beneficial insects. Our results showed that yield strongly varies according to both pesticide type and timing of pesticide application. The type of pesticide had a strong influence on the flexibility of management. No simple spraying decision rule led to maximal yields for all types of pesticide. Although optimal spraying strategies differed with the type of pesticide used, they all showed a similar pattern, i.e. they limited and postponed the Cacao Pod Borer population peak while limiting the negative impacts on beneficial organisms. The results highlight the non-trivial effects of pesticide application in complex agroecosystems where associated biodiversity provides both ecosystem services and disservices. They illustrate the critical importance of providing good information to farmers on pesticide management because the use of pesticides can have a negative effect on production by decreasing ecosystem services such as pollination. {\textcopyright} 2013 Gesellschaft f{\"{u}}r {\"{O}}kologie.},
  comment  = {public},
  doi      = {10.1016/j.baae.2012.12.006},
  groups   = {Jana:1},
  isbn     = {1439-1791},
  keywords = {Agroecosystem,Cacao,Dynamic model,Ecosystem services,Pesticide,Pollination},
}

Growing concerns have been raised regarding the effects of disturbance due to agricultural practices on associate biodiversity and on the ecosystem services that biodiversity provides. Surprisingly little is known about the effects of such disturbances on complex agroecosystems with multiple interacting species. The aim of this study was to assess the effects of management by pesticide spraying on the productive outputs and the ecological functioning of a cacao agroecosystem. We built a mechanistic dynamic model including the dynamics of the crop, a pest (Cacao Pod Borer, Conopomorpha cramerella) and two beneficial insects: a hymenopteran egg-parasitoid and a ceratopogonid pollinator. Using this model, we tested the effects of a range of pesticide types characterized by their impacts on both the Cacao Pod Borer and the beneficial insects. Our results showed that yield strongly varies according to both pesticide type and timing of pesticide application. The type of pesticide had a strong influence on the flexibility of management. No simple spraying decision rule led to maximal yields for all types of pesticide. Although optimal spraying strategies differed with the type of pesticide used, they all showed a similar pattern, i.e. they limited and postponed the Cacao Pod Borer population peak while limiting the negative impacts on beneficial organisms. The results highlight the non-trivial effects of pesticide application in complex agroecosystems where associated biodiversity provides both ecosystem services and disservices. They illustrate the critical importance of providing good information to farmers on pesticide management because the use of pesticides can have a negative effect on production by decreasing ecosystem services such as pollination. © 2013 Gesellschaft für Ökologie.

@Article{Sabatier2013a,
  author   = {Sabatier, Rodolphe and Wiegand, Kerstin and Meyer, Katrin},
  title    = {{Production and robustness of a cacao agroecosystem: Effects of two contrasting types of management strategies}},
  journal  = {PLoS ONE},
  year     = {2013},
  volume   = {8},
  number   = {12},
  issn     = {19326203},
  url_pdf  = {http://uni-goettingen.de/de/document/download/7404b7b89fea630f967230034ad7ab05.pdf/SabatierEtAl_2013_Plos1.pdf},
  abstract = {Ecological intensification, i.e. relying on ecological processes to replace chemical inputs, is often presented as the ideal alternative to conventional farming based on an intensive use of chemicals. It is said to both maintain high yield and provide more robustness to the agroecosystem. However few studies compared the two types of management with respect to their consequences for production and robustness toward perturbation. In this study our aim is to assess productive performance and robustness toward diverse perturbations of a Cacao agroecosystem managed with two contrasting groups of strategies: one group of strategies relying on a high level of pesticides and a second relying on low levels of pesticides. We conducted this study using a dynamical model of a Cacao agroecosystem that includes Cacao production dynamics, and dynamics of three insects: a pest (the Cacao Pod Borer, Conopomorpha cramerella) and two characteristic but unspecified beneficial insects (a pollinator of Cacao and a parasitoid of the Cacao Pod Borer). Our results showed two opposite behaviors of the Cacao agroecosystem depending on its management, i.e. an agroecosystem relying on a high input of pesticides and showing low ecosystem functioning and an agroecosystem with low inputs, relying on a high functioning of the ecosystem. From the production point of view, no type of management clearly outclassed the other and their ranking depended on the type of pesticide used. From the robustness point of view, the two types of managements performed differently when subjected to different types of perturbations. Ecologically intensive systems were more robust to pest outbreaks and perturbations related to pesticide characteristics while chemically intensive systems were more robust to Cacao production and management-related perturbation.},
  comment  = {public},
  doi      = {10.1371/journal.pone.0080352},
  isbn     = {1932-6203},
  pmid     = {24312469},
}

Ecological intensification, i.e. relying on ecological processes to replace chemical inputs, is often presented as the ideal alternative to conventional farming based on an intensive use of chemicals. It is said to both maintain high yield and provide more robustness to the agroecosystem. However few studies compared the two types of management with respect to their consequences for production and robustness toward perturbation. In this study our aim is to assess productive performance and robustness toward diverse perturbations of a Cacao agroecosystem managed with two contrasting groups of strategies: one group of strategies relying on a high level of pesticides and a second relying on low levels of pesticides. We conducted this study using a dynamical model of a Cacao agroecosystem that includes Cacao production dynamics, and dynamics of three insects: a pest (the Cacao Pod Borer, Conopomorpha cramerella) and two characteristic but unspecified beneficial insects (a pollinator of Cacao and a parasitoid of the Cacao Pod Borer). Our results showed two opposite behaviors of the Cacao agroecosystem depending on its management, i.e. an agroecosystem relying on a high input of pesticides and showing low ecosystem functioning and an agroecosystem with low inputs, relying on a high functioning of the ecosystem. From the production point of view, no type of management clearly outclassed the other and their ranking depended on the type of pesticide used. From the robustness point of view, the two types of managements performed differently when subjected to different types of perturbations. Ecologically intensive systems were more robust to pest outbreaks and perturbations related to pesticide characteristics while chemically intensive systems were more robust to Cacao production and management-related perturbation.

@Article{Schumacher2013,
  author  = {Schumacher, W. and Trein, L. and Esser, Daniel S.},
  title   = {{Biodiversit{\"{a}}t von Magerrasen, Wiesen und Weiden am Beispiel der Eifel - Erhaltung und F{\"{o}}rderung durch integrative Nutzung}},
  journal = {Berichte der Reinhold-T{\"{u}}xen-Gesellschaft},
  year    = {2013},
  volume  = {25},
  pages   = {56--71},
  url_pdf = {http://uni-goettingen.de/de/document/download/9a029cb4e763c72fe5be7420200b571b.pdf/Schumacher_et_al_2013_Biodiversit%C3%A4t_Magerrasen_Wiesen_Weiden_Beispiel_Eifel.pdf},
  comment = {public},
}

@Misc{Ward2013,
  author    = {Ward, David and Wiegand, Kerstin and Getzin, Stephan},
  title     = {{Walter's two-layer hypothesis revisited: Back to the roots!}},
  year      = {2013},
  url_pdf   = {http://uni-goettingen.de/de/document/download/78587b82aecc9ae689ab8ea8da0b608b.pdf/Ward_et_al_(2013)_Oecologia.pdf},
  abstract  = {Walter (Jahrb Wiss Bot 87:750-860, 1939) proposed a two-layer hypothesis, an equilibrium explanation for coexistence of savanna trees and grasses. This hypothesis relies on vertical niche partitioning and assumed that grasses are more water-use efficient than trees and use subsurface water while trees also have access to deeper water sources. Thus, in open savannas, grasses were predicted to predominate because of their water use efficiency and access to subsurface water. This hypothesis has been a prominent part of the savanna literature since first proposed. We review the literature on Walter's hypothesis and reconsider his original intentions. Walter intended this hypothesis to be restricted to dry savannas. In his opinion, mesic and humid savannas were controlled by biotic factors and disturbances. We surveyed the global savanna literature for records of vertical niche partitioning by grasses and trees. We find that, within the scope of Walter's original intentions, this hypothesis works remarkably well, and in some cases is appropriate for deserts as well as for dry temperate systems and even some mesic savannas.},
  booktitle = {Oecologia},
  comment   = {public},
  doi       = {10.1007/s00442-012-2538-y},
  isbn      = {0029-8549},
  issn      = {00298549},
  keywords  = {Codominance,Equilibrium theory,Patch dynamics,Resource partitioning,Root distributions,Savanna,Spatial heterogeneity,Tree-grass coexistence,Water},
  number    = {3},
  pages     = {617--630},
  pmid      = {23266712},
  volume    = {172},
}

Walter (Jahrb Wiss Bot 87:750-860, 1939) proposed a two-layer hypothesis, an equilibrium explanation for coexistence of savanna trees and grasses. This hypothesis relies on vertical niche partitioning and assumed that grasses are more water-use efficient than trees and use subsurface water while trees also have access to deeper water sources. Thus, in open savannas, grasses were predicted to predominate because of their water use efficiency and access to subsurface water. This hypothesis has been a prominent part of the savanna literature since first proposed. We review the literature on Walter's hypothesis and reconsider his original intentions. Walter intended this hypothesis to be restricted to dry savannas. In his opinion, mesic and humid savannas were controlled by biotic factors and disturbances. We surveyed the global savanna literature for records of vertical niche partitioning by grasses and trees. We find that, within the scope of Walter's original intentions, this hypothesis works remarkably well, and in some cases is appropriate for deserts as well as for dry temperate systems and even some mesic savannas.

@Article{Getzin2012,
  author   = {Getzin, Stephan and Wiegand, Kerstin and Sch{\"{o}}ning, Ingo},
  title    = {{Assessing biodiversity in forests using very high-resolution images and unmanned aerial vehicles}},
  journal  = {Methods in Ecology and Evolution},
  year     = {2012},
  volume   = {3},
  number   = {2},
  pages    = {397--404},
  issn     = {2041210X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/b19a2d0c8ae475edc32cd1ddde9936a5.pdf/Getzin_et_al_MEE_2012_assessing_biodiversity_UAV.pdf},
  abstract = {1. Structural diversity and niche differences within habitats are important for stabilizing species coexistence. However, land-use change leading to environmental homogenization is a major cause for the dramatic decline of biodiversity under global change. The difficulty in assessing large-scale biodiversity losses urgently requires new technological advances to evaluate land-use impact on diversity timely andefficiently across space. 2. While cost-effective aerial images have been suggested for potential biodiversity assessments in forests, correlation of canopy object variables such as gaps with plant or animal diversity has so far not been demonstrated using these images. 3. Here,we show that aerial images of canopy gaps can be used to assess floristic biodiversity of the forest understorey. This approach is made possible because we employed cutting-edge unmanned aerial vehicles and very high-resolution images (7 cm pixel)1) of the canopy properties. Wedemon- strate that detailed, spatially implicit information on gap shape metrics is sufficient to reveal strong dependency between disturbance patterns and plant diversity (R2 up to 0{\AE}74). This is feasible because opposing disturbance patterns such as aggregated and dispersed tree retention directly cor- respond to different functional and dispersal traits of species and ultimately to different species diversities. 4. Our findings can be used as a coarse-filter approach to conservation in forests wherever light strongly limits regeneration and biodiversity.},
  comment  = {public},
  doi      = {10.1111/j.2041-210X.2011.00158.x},
  isbn     = {2041-210X},
  keywords = {Biodiversity,Coarse-filter approach,Forest understorey,Gap shape complexity index,Unmanned aerial vehicles},
}

1. Structural diversity and niche differences within habitats are important for stabilizing species coexistence. However, land-use change leading to environmental homogenization is a major cause for the dramatic decline of biodiversity under global change. The difficulty in assessing large-scale biodiversity losses urgently requires new technological advances to evaluate land-use impact on diversity timely andefficiently across space. 2. While cost-effective aerial images have been suggested for potential biodiversity assessments in forests, correlation of canopy object variables such as gaps with plant or animal diversity has so far not been demonstrated using these images. 3. Here,we show that aerial images of canopy gaps can be used to assess floristic biodiversity of the forest understorey. This approach is made possible because we employed cutting-edge unmanned aerial vehicles and very high-resolution images (7 cm pixel)1) of the canopy properties. Wedemon- strate that detailed, spatially implicit information on gap shape metrics is sufficient to reveal strong dependency between disturbance patterns and plant diversity (R2 up to 0Æ74). This is feasible because opposing disturbance patterns such as aggregated and dispersed tree retention directly cor- respond to different functional and dispersal traits of species and ultimately to different species diversities. 4. Our findings can be used as a coarse-filter approach to conservation in forests wherever light strongly limits regeneration and biodiversity.

@Article{Kwak2012,
  author   = {Kwak, Hanbin and Lee, Woo-Kyun and Saborowski, Joachim and Lee, Si-Young and Won, Myoung-Soo and Koo, Kyo-Sang and Lee, Myung-Bo and Kim, Su-Na},
  title    = {{Estimating the spatial pattern of human-caused forest fires using a generalized linear mixed model with spatial autocorrelation in South Korea}},
  journal  = {International Journal of Geographical Information Science},
  year     = {2012},
  volume   = {26},
  number   = {9},
  pages    = {1589--1602},
  issn     = {1365-8816},
  url_pdf  = {http://uni-goettingen.de/de/document/download/bf88d98f0356c9afe7e793c9832a9576.pdf/Kwak%20etal_(2012)_IJGIS_ForestFirePattern.pdf},
  abstract = {Most forest fires in Korea are spatially concentrated in certain areas and are highly related to human activities. These site-specific characteristics of forest fires are analyzed by spatial regression analysis using the R-module generalized linear mixed model (GLMM), which can consider spatial autocorrelation. We examined the quantitative effect of topology, human accessibility, and forest cover without and with spatial autocorrelation. Under the assumption that slope, elevation, aspect, population density, distance from road, and forest cover are related to forest fire occurrence, the explanatory variables of each of these factors were prepared using a Geographic Information System-based process. First, we tried to test the influence of fixed effects on the occurrence of forest fires using a generalized linear model (GLM) with Poisson distribution. In addition, the overdispersion of the response data was also detected, and variogram analysis was performed using the standardized residuals of GLM. Second, GLMM was applied to consider the obvious residual autocorrelation structure. The fitted models were validated and compared using the multiple correlation and root mean square error (RMSE). Results showed that slope, elevation, aspect index, population density, and distance from road were significant factors capable of explaining the forest fire occurrence. Positive spatial autocorrelation was estimated up to a distance of 32 km. The kriging predictions based on GLMM were smoother than those of the GLM. Finally, a forest fire occurrence map was prepared using the results from both models. The fire risk decreases with increasing distance to areas with high population densities, and increasing elevation showed a suppressing effect on fire occurrence. Both variables are in accordance with the significance tests. {\textcopyright} 2012 Copyright Taylor and Francis Group, LLC.},
  comment  = {public},
  doi      = {10.1080/13658816.2011.642799},
  isbn     = {1365-8816},
  url      = {http://www.tandfonline.com/doi/abs/10.1080/13658816.2011.642799},
}

Most forest fires in Korea are spatially concentrated in certain areas and are highly related to human activities. These site-specific characteristics of forest fires are analyzed by spatial regression analysis using the R-module generalized linear mixed model (GLMM), which can consider spatial autocorrelation. We examined the quantitative effect of topology, human accessibility, and forest cover without and with spatial autocorrelation. Under the assumption that slope, elevation, aspect, population density, distance from road, and forest cover are related to forest fire occurrence, the explanatory variables of each of these factors were prepared using a Geographic Information System-based process. First, we tried to test the influence of fixed effects on the occurrence of forest fires using a generalized linear model (GLM) with Poisson distribution. In addition, the overdispersion of the response data was also detected, and variogram analysis was performed using the standardized residuals of GLM. Second, GLMM was applied to consider the obvious residual autocorrelation structure. The fitted models were validated and compared using the multiple correlation and root mean square error (RMSE). Results showed that slope, elevation, aspect index, population density, and distance from road were significant factors capable of explaining the forest fire occurrence. Positive spatial autocorrelation was estimated up to a distance of 32 km. The kriging predictions based on GLMM were smoother than those of the GLM. Finally, a forest fire occurrence map was prepared using the results from both models. The fire risk decreases with increasing distance to areas with high population densities, and increasing elevation showed a suppressing effect on fire occurrence. Both variables are in accordance with the significance tests. © 2012 Copyright Taylor and Francis Group, LLC.

@Misc{Meyer2012,
  author    = {Meyer, Katrin M. and Leveau, Johan H.J.},
  title     = {{Microbiology of the phyllosphere: A playground for testing ecological concepts}},
  year      = {2012},
  url_pdf   = {http://uni-goettingen.de/de/document/download/33bb31843a04bb504486470974a5c003.pdf/MeyerLeveau_(2012)_OECOLOGIA_ecological_concepts_phyllosphere.pdf},
  abstract  = {Many concepts and theories in ecology are highly debated, because it is often difficult to design decisive tests with sufficient replicates. Examples include biodiversity theories, succession concepts, invasion theories, coexistence theories, and concepts of life history strategies. Microbiological tests of ecological concepts are rapidly accumulating, but have yet to tap into their full potential to complement traditional macroecological theories. Taking the example of microbial communities on leaf surfaces (i.e. the phyllosphere), we show that most explorations of ecological concepts in this field of microbiology focus on autecology and population ecology, while community ecology remains understudied. Notable exceptions are first tests of the island biogeography theory and of biodiversity theories. Here, the phyllosphere provides the unique opportunity to set up replicated experiments, potentially moving fields such as biogeography, macroecology, and landscape ecology beyond theoretical and observational evidence. Future approaches should take advantage of the great range of spatial scales offered by the leaf surface by iteratively linking laboratory experiments with spatial simulation models.},
  booktitle = {Oecologia},
  comment   = {public},
  doi       = {10.1007/s00442-011-2138-2},
  isbn      = {1432-1939 (Electronic)$\backslash$r0029-8549 (Linking)},
  issn      = {00298549},
  keywords  = {Biogeography,Diversity,Ecological theories,Leaf surface,Niche},
  number    = {3},
  pages     = {621--629},
  pmid      = {21983641},
  volume    = {168},
}

Many concepts and theories in ecology are highly debated, because it is often difficult to design decisive tests with sufficient replicates. Examples include biodiversity theories, succession concepts, invasion theories, coexistence theories, and concepts of life history strategies. Microbiological tests of ecological concepts are rapidly accumulating, but have yet to tap into their full potential to complement traditional macroecological theories. Taking the example of microbial communities on leaf surfaces (i.e. the phyllosphere), we show that most explorations of ecological concepts in this field of microbiology focus on autecology and population ecology, while community ecology remains understudied. Notable exceptions are first tests of the island biogeography theory and of biodiversity theories. Here, the phyllosphere provides the unique opportunity to set up replicated experiments, potentially moving fields such as biogeography, macroecology, and landscape ecology beyond theoretical and observational evidence. Future approaches should take advantage of the great range of spatial scales offered by the leaf surface by iteratively linking laboratory experiments with spatial simulation models.

@Article{Meyer2012a,
  author   = {Meyer, Katrin M. and Vos, Matthijs and Mooij, Wolf M. and Hol, W. H Gera and Termorshuizen, Aad J. and van der Putten, Wim H.},
  title    = {{Testing the Paradox of Enrichment along a Land Use Gradient in a Multitrophic Aboveground and Belowground Community}},
  journal  = {PLoS ONE},
  year     = {2012},
  volume   = {7},
  number   = {11},
  issn     = {19326203},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e1b70dcba449b281aba46bb8af008ca4.PDF/Meyer_et_al_2012_PLOS_paradox_enrichment_along_land-use_gradient.PDF},
  abstract = {In the light of ongoing land use changes, it is important to understand how multitrophic communities perform at different land use intensities. The paradox of enrichment predicts that fertilization leads to destabilization and extinction of predator-prey systems. We tested this prediction for a land use intensity gradient from natural to highly fertilized agricultural ecosystems. We included multiple aboveground and belowground trophic levels and land use-dependent searching efficiencies of insects. To overcome logistic constraints of field experiments, we used a successfully validated simulation model to investigate plant responses to removal of herbivores and their enemies. Consistent with our predictions, instability measured by herbivore-induced plant mortality increased with increasing land use intensity. Simultaneously, the balance between herbivores and natural enemies turned increasingly towards herbivore dominance and natural enemy failure. Under natural conditions, there were more frequently significant effects of belowground herbivores and their natural enemies on plant performance, whereas there were more aboveground effects in agroecosystems. This result was partly due to the "boom-bust" behavior of the shoot herbivore population. Plant responses to herbivore or natural enemy removal were much more abrupt than the imposed smooth land use intensity gradient. This may be due to the presence of multiple trophic levels aboveground and belowground. Our model suggests that destabilization and extinction are more likely to occur in agroecosystems than in natural communities, but the shape of the relationship is nonlinear under the influence of multiple trophic interactions.},
  comment  = {public},
  doi      = {10.1371/journal.pone.0049034},
  isbn     = {1932-6203},
  pmid     = {23145055},
}

In the light of ongoing land use changes, it is important to understand how multitrophic communities perform at different land use intensities. The paradox of enrichment predicts that fertilization leads to destabilization and extinction of predator-prey systems. We tested this prediction for a land use intensity gradient from natural to highly fertilized agricultural ecosystems. We included multiple aboveground and belowground trophic levels and land use-dependent searching efficiencies of insects. To overcome logistic constraints of field experiments, we used a successfully validated simulation model to investigate plant responses to removal of herbivores and their enemies. Consistent with our predictions, instability measured by herbivore-induced plant mortality increased with increasing land use intensity. Simultaneously, the balance between herbivores and natural enemies turned increasingly towards herbivore dominance and natural enemy failure. Under natural conditions, there were more frequently significant effects of belowground herbivores and their natural enemies on plant performance, whereas there were more aboveground effects in agroecosystems. This result was partly due to the "boom-bust" behavior of the shoot herbivore population. Plant responses to herbivore or natural enemy removal were much more abrupt than the imposed smooth land use intensity gradient. This may be due to the presence of multiple trophic levels aboveground and belowground. Our model suggests that destabilization and extinction are more likely to occur in agroecosystems than in natural communities, but the shape of the relationship is nonlinear under the influence of multiple trophic interactions.

@Article{Nothdurft2012,
  author   = {Nothdurft, Arne and Wolf, Thilo and Ringeler, Andre and B{\"{o}}hner, J{\"{u}}rgen and Saborowski, Joachim},
  title    = {{Spatio-temporal prediction of site index based on forest inventories and climate change scenarios}},
  journal  = {Forest Ecology and Management},
  year     = {2012},
  volume   = {279},
  pages    = {97--111},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a85d2916f15ac107d4dccd596a9a06b5.pdf/2012_FORECO_Nothdurft_etal.pdf},
  abstract = {A methodological framework is provided for the quantification of climate change effects on site index. Spatio-temporal predictions of site index are derived for six major tree species in the German state of Baden-W{\"{u}}rttemberg using simplified universal kriging (UK) based on large data sets from forest inventories and a climate sensitive site-index model. It is shown by a simulation study that, with the underlying large sample size, residual kriging using ordinary least squares (OLS) estimates of the mean function leads to an approximately unbiased spatial predictor. Moreover, the simulated coverage probabilities of resulting prediction intervals are quite close to the required level. B-spline regression techniques are applied to model nonlinear cause-and-effect curves for estimating site indexes at existing inventory plots dependent on retrospective climate covariates. The spatially structured error is modeled by exponential covariance functions. The mean model is then applied to downscaled climate projection data to spatially predict the relative changes of site index under perturbed climate conditions.Applying climate projections of an existing regional climate model based on IPCC emission scenarios A1B and A2, it is found that site index of all tree species would be decreased in lowland areas, and may increase in mountainous regions. Silver fir and common oak stands would also show increased site indexes in mountainous regions, but further extended to lower elevation levels. Site conditions in the Alpine foothills may remain highly productive for growth of Norway spruce, Baden-W{\"{u}}rttemberg's most dominant tree species. Whereas site index of common beech and Douglas-fir may decrease to almost the same relative amount and on nearly the same sites as Norway spruce, site index of Scots pine may be less affected by future climate change. {\textcopyright} 2012 Elsevier B.V.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2012.05.018},
  isbn     = {0378-1127},
  keywords = {Climate change,Forest inventory,Site-index prediction},
}

A methodological framework is provided for the quantification of climate change effects on site index. Spatio-temporal predictions of site index are derived for six major tree species in the German state of Baden-Württemberg using simplified universal kriging (UK) based on large data sets from forest inventories and a climate sensitive site-index model. It is shown by a simulation study that, with the underlying large sample size, residual kriging using ordinary least squares (OLS) estimates of the mean function leads to an approximately unbiased spatial predictor. Moreover, the simulated coverage probabilities of resulting prediction intervals are quite close to the required level. B-spline regression techniques are applied to model nonlinear cause-and-effect curves for estimating site indexes at existing inventory plots dependent on retrospective climate covariates. The spatially structured error is modeled by exponential covariance functions. The mean model is then applied to downscaled climate projection data to spatially predict the relative changes of site index under perturbed climate conditions.Applying climate projections of an existing regional climate model based on IPCC emission scenarios A1B and A2, it is found that site index of all tree species would be decreased in lowland areas, and may increase in mountainous regions. Silver fir and common oak stands would also show increased site indexes in mountainous regions, but further extended to lower elevation levels. Site conditions in the Alpine foothills may remain highly productive for growth of Norway spruce, Baden-Württemberg's most dominant tree species. Whereas site index of common beech and Douglas-fir may decrease to almost the same relative amount and on nearly the same sites as Norway spruce, site index of Scots pine may be less affected by future climate change. © 2012 Elsevier B.V.

@Article{Ritter2012,
  author   = {Ritter, Tim and Saborowski, Joachim},
  title    = {{Point transect sampling of deadwood: A comparison with well-established sampling techniques for the estimation of volume and carbon storage in managed forests}},
  journal  = {European Journal of Forest Research},
  year     = {2012},
  volume   = {131},
  number   = {6},
  pages    = {1845--1856},
  issn     = {16124669},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2e2d0af521d7d5976b0f5eda6232ba77.pdf/2012_EJFR_RitterSab.pdf},
  abstract = {In managed forests, the occurrence of deadwood (DW) can be regarded as a stochastically rare event with strong clumping and high local variability (Meyer in Forstwissenschaftliches Centralblatt 118:167–180, 1999 ). Traditional sampling techniques, such as Fixed Area Sampling, Angle Count Sampling and Line Intersect Sampling, do not regard this fact and may be inefficient for surveys of DW, because of limited search areas. A sampling technique that should remedy this shortcoming is Point Transect Sampling (Buckland et al. in Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2001 ; Advanced distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2004 ), where as a matter of principle, all objects that are sighted from a fixed location are counted. We compare Point Transect Sampling with the other well-established sampling approaches for the estimation of volume, necromass and carbon storage in terms of precision and sampling effort. It is shown that Point Transect Sampling is the superior method for sampling standing DW regarding efficiency, whereas for sampling downed DW, it is clearly outperformed by Line Intersect Sampling.},
  comment  = {public},
  doi      = {10.1007/s10342-012-0637-2},
  isbn     = {1612-4669},
  keywords = {Carbon sequestration,Carbon storage,Deadwood,Distance sampling,Point transect sampling,Woody debris},
}

In managed forests, the occurrence of deadwood (DW) can be regarded as a stochastically rare event with strong clumping and high local variability (Meyer in Forstwissenschaftliches Centralblatt 118:167–180, 1999 ). Traditional sampling techniques, such as Fixed Area Sampling, Angle Count Sampling and Line Intersect Sampling, do not regard this fact and may be inefficient for surveys of DW, because of limited search areas. A sampling technique that should remedy this shortcoming is Point Transect Sampling (Buckland et al. in Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2001 ; Advanced distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2004 ), where as a matter of principle, all objects that are sighted from a fixed location are counted. We compare Point Transect Sampling with the other well-established sampling approaches for the estimation of volume, necromass and carbon storage in terms of precision and sampling effort. It is shown that Point Transect Sampling is the superior method for sampling standing DW regarding efficiency, whereas for sampling downed DW, it is clearly outperformed by Line Intersect Sampling.

@Article{Sabatier2012,
  author   = {Sabatier, Rodolphe and Doyen, Luc and Tichit, Muriel},
  title    = {{Action versus result-oriented schemes in a Grassland agroecosystem: A dynamic modelling approach}},
  journal  = {PLoS ONE},
  year     = {2012},
  volume   = {7},
  number   = {4},
  issn     = {19326203},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ab375eea96459046fa9193bd3574642b.pdf/journal.pone.0033257.pdf},
  abstract = {Effects of agri-environment schemes (AES) on biodiversity remain controversial. While most AES are action-oriented, result-oriented and habitat-oriented schemes have recently been proposed as a solution to improve AES efficiency. The objective of this study was to compare action-oriented, habitat-oriented and result-oriented schemes in terms of ecological and productive performance as well as in terms of management flexibility. We developed a dynamic modelling approach based on the viable control framework to carry out a long term assessment of the three schemes in a grassland agroecosystem. The model explicitly links grazed grassland dynamics to bird population dynamics. It is applied to lapwing conservation in wet grasslands in France. We ran the model to assess the three AES scenarios. The model revealed the grazing strategies respecting ecological and productive constraints specific to each scheme. Grazing strategies were assessed by both their ecological and productive performance. The viable control approach made it possible to obtain the whole set of viable grazing strategies and therefore to quantify the management flexibility of the grassland agroecosystem. Our results showed that habitat and result-oriented scenarios led to much higher ecological performance than the action-oriented one. Differences in both ecological and productive performance between the habitat and result-oriented scenarios were limited. Flexibility of the grassland agroecosystem in the result-oriented scenario was much higher than in that of habitat-oriented scenario. Our model confirms the higher flexibility as well as the better ecological and productive performance of result-oriented schemes. A larger use of result-oriented schemes in conservation may also allow farmers to adapt their management to local conditions and to climatic variations.},
  comment  = {public},
  doi      = {10.1371/journal.pone.0033257},
  isbn     = {1932-6203},
  pmid     = {22496746},
}

Effects of agri-environment schemes (AES) on biodiversity remain controversial. While most AES are action-oriented, result-oriented and habitat-oriented schemes have recently been proposed as a solution to improve AES efficiency. The objective of this study was to compare action-oriented, habitat-oriented and result-oriented schemes in terms of ecological and productive performance as well as in terms of management flexibility. We developed a dynamic modelling approach based on the viable control framework to carry out a long term assessment of the three schemes in a grassland agroecosystem. The model explicitly links grazed grassland dynamics to bird population dynamics. It is applied to lapwing conservation in wet grasslands in France. We ran the model to assess the three AES scenarios. The model revealed the grazing strategies respecting ecological and productive constraints specific to each scheme. Grazing strategies were assessed by both their ecological and productive performance. The viable control approach made it possible to obtain the whole set of viable grazing strategies and therefore to quantify the management flexibility of the grassland agroecosystem. Our results showed that habitat and result-oriented scenarios led to much higher ecological performance than the action-oriented one. Differences in both ecological and productive performance between the habitat and result-oriented scenarios were limited. Flexibility of the grassland agroecosystem in the result-oriented scenario was much higher than in that of habitat-oriented scenario. Our model confirms the higher flexibility as well as the better ecological and productive performance of result-oriented schemes. A larger use of result-oriented schemes in conservation may also allow farmers to adapt their management to local conditions and to climatic variations.

@Incollection{Scherber2012,
  author    = {Scherber, Christoph and Lavandero, Blas and Meyer, Katrin M. and Perovic, David and Visser, Ute and Wiegand, Kerstin and Tscharntke, Teja},
  title     = {{Scale Effects in Biodiversity and Biological Control: Methods and Statistical Analysis}},
  booktitle = {Biodiversity and Insect Pests: Key Issues for Sustainable Management},
  year      = {2012},
  pages     = {121--138},
  isbn      = {9780470656860},
  url_pdf   = {http://uni-goettingen.de/de/document/download/25662919fef570e395e195f8f143c069.pdf/Scherber_etal_2012_ScaleEffectsBioControl.pdf},
  comment   = {public},
  doi       = {10.1002/9781118231838.ch8},
  keywords  = {Biological control, different spatial scales,Field methods, landscape-scale patterns,Grid-based landscape sampling, for modelling,Laboratory to field, upscaling problems,Landscape scale, biological control study,Observational, experimental approaches,Rare-earth labeling, spatial population dynamics,Scale effects in biodiversity and biological contr,Tracking insects, in agricultural landscapes},
}

@Article{VonLupke2012,
  author   = {von L{\"{u}}pke, Nikolas and Hansen, Jan and Saborowski, Joachim},
  title    = {{A three-phase sampling procedure for continuous forest inventory with partial re-measurement and updating of terrestrial sample plots}},
  journal  = {European Journal of Forest Research},
  year     = {2012},
  volume   = {131},
  number   = {6},
  pages    = {1979--1990},
  issn     = {16124669},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d16ac01230ede2ebe41330a1728f6c99.pdf/2012_EJFR_vLuepke_etal.pdf},
  abstract = {For a current inventory using double sampling for stratification with a reduced second-phase sample size, compared with a previous inventory, we develop a three-phase sampling procedure that exploits plot data from the previous inventory or their updates based on a growth model to increase precision. The three-phase procedure combines double sampling for stratification with a two-phase regression estimator within strata. We consider sampling from an infinite population in the first phase. The combined estimator is tested in a case study using data from two consecutive inventories in four State Forest Districts in Lower Saxony, Germany. Data from a reduced number of sample plots from the second occasion are combined with (1) volumes from the first occasion or (2) growth simulations on the sample plots from the first occasion. The data from the previous inventory or their updates serve as the auxiliary variable for the regression estimator of the strata means of the target variable. This case study indicates a remarkable increase in precision and thereby an enormous cost-saving potential for reduced intermediate inventories in a periodic inventory design with both types of auxiliary variables.},
  comment  = {public},
  doi      = {10.1007/s10342-012-0648-z},
  keywords = {Continuous forest inventory,Double sampling for regression,Double sampling for stratification,Forest growth models},
}

For a current inventory using double sampling for stratification with a reduced second-phase sample size, compared with a previous inventory, we develop a three-phase sampling procedure that exploits plot data from the previous inventory or their updates based on a growth model to increase precision. The three-phase procedure combines double sampling for stratification with a two-phase regression estimator within strata. We consider sampling from an infinite population in the first phase. The combined estimator is tested in a case study using data from two consecutive inventories in four State Forest Districts in Lower Saxony, Germany. Data from a reduced number of sample plots from the second occasion are combined with (1) volumes from the first occasion or (2) growth simulations on the sample plots from the first occasion. The data from the previous inventory or their updates serve as the auxiliary variable for the regression estimator of the strata means of the target variable. This case study indicates a remarkable increase in precision and thereby an enormous cost-saving potential for reduced intermediate inventories in a periodic inventory design with both types of auxiliary variables.

@Article{Choi2011,
  author   = {Choi, S and Lee, WK and Kwak, DA and Lee, S and Son, Y and Lim, JH and Saborowski, J},
  title    = {{Predicting forest cover changes in future climate using hydrological and thermal indices in South Korea}},
  journal  = {Climate Research},
  year     = {2011},
  volume   = {49},
  number   = {3},
  pages    = {229--245},
  issn     = {0936-577X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/4506288bcd0ee84fb584ae91ead54bbe.pdf/Choi%20etal_(2011)_ClimateResearch_ForestCoverChanges.pdf},
  abstract = {We studied the potential responses of forest vegetation to climate change in South Korea using a Korea-specific forest cover distribution model based on hydrological and thermal indices. The past and future climatic parameters were converted to hydrological and thermal indices that have been reported as climatic controllers of forest vegetation distribution: (1) the Precipitation Effectiveness Index (PEI), (2) Warmth Index (WI), and (3) Minimum Temperature of the Coldest Month Index (MTCI). The vegetation map from the Ministry of Environment was applied to determine the optimal habitat PEI, WI, and MTCI ranges for major tree species in Korea. Then, 8 plant functional types (PFTs) were defined according to the analogies in the optimal habitat PEI, WI, and MTCI ranges, and the result was named the Hydrological and Thermal Analogy Groups (HyTAGs). The HyTAG model was used to simulate the potential forest cover distribution of Korea in the past (1971 to 2000), near future (2045 to 2065), and far future (2080 to 2099) with 3 IPCC climate change scenarios (B1, A1B, and A2). The potential forest cover distribution changes of the HyTAGs resulted in the shrinking of the cool temperate forests and the expansion of the warm temperate and subtropical forests, with different rates in each climate change scenario. The classification accuracy (CA) and prediction probability (PrP) values of 32.4 and 35.0{\%}, respectively, validated the accuracy of HyTAGs as being relatively predictive of overall distributions of cool-temperate (HyTAG-A), temperate (HyTAG-B), and warm-temperate (HyTAG-C) mixed forests.},
  comment  = {public},
  doi      = {10.3354/cr01026},
  isbn     = {0936-577X},
  url      = {http://www.int-res.com/abstracts/cr/v49/n3/p229-245/},
}

We studied the potential responses of forest vegetation to climate change in South Korea using a Korea-specific forest cover distribution model based on hydrological and thermal indices. The past and future climatic parameters were converted to hydrological and thermal indices that have been reported as climatic controllers of forest vegetation distribution: (1) the Precipitation Effectiveness Index (PEI), (2) Warmth Index (WI), and (3) Minimum Temperature of the Coldest Month Index (MTCI). The vegetation map from the Ministry of Environment was applied to determine the optimal habitat PEI, WI, and MTCI ranges for major tree species in Korea. Then, 8 plant functional types (PFTs) were defined according to the analogies in the optimal habitat PEI, WI, and MTCI ranges, and the result was named the Hydrological and Thermal Analogy Groups (HyTAGs). The HyTAG model was used to simulate the potential forest cover distribution of Korea in the past (1971 to 2000), near future (2045 to 2065), and far future (2080 to 2099) with 3 IPCC climate change scenarios (B1, A1B, and A2). The potential forest cover distribution changes of the HyTAGs resulted in the shrinking of the cool temperate forests and the expansion of the warm temperate and subtropical forests, with different rates in each climate change scenario. The classification accuracy (CA) and prediction probability (PrP) values of 32.4 and 35.0%, respectively, validated the accuracy of HyTAGs as being relatively predictive of overall distributions of cool-temperate (HyTAG-A), temperate (HyTAG-B), and warm-temperate (HyTAG-C) mixed forests.

@Misc{GeraHol2011,
  author    = {{Gera Hol}, W. H. and Meyer, Katrin M. and {Van Der Putten}, Wim H.},
  title     = {{Idiosyncrasy in ecology - What's in a word?}},
  year      = {2011},
  url_pdf   = {http://uni-goettingen.de/de/document/download/3e4df9f9d3c158562ad6cde9b16cce14.pdf/HolMeyerVdPutten_(2011)_FRONTECENV_idiosyncrasy.pdf},
  abstract  = {no abstract},
  booktitle = {Frontiers in Ecology and the Environment},
  comment   = {public},
  doi       = {10.1890/11.WB.024},
  isbn      = {1540-9295},
  issn      = {15409295},
  number    = {8},
  pages     = {431--433},
  volume    = {9},
}

no abstract

@Article{Getzin2011,
  author   = {Getzin, Stephan and Worbes, Martin and Wiegand, Thorsten and Wiegand, Kerstin},
  title    = {{Size dominance regulates tree spacing more than competition within height classes in tropical Cameroon}},
  journal  = {Journal of Tropical Ecology},
  year     = {2011},
  volume   = {27},
  number   = {1},
  pages    = {93--102},
  issn     = {02664674},
  url_pdf  = {http://uni-goettingen.de/de/document/download/8ab6935acb5b4ea116921a38e7d4b262.pdf/Getzin_et_al_(2011)_J_Tropical_Ecology_Size_dominance_regulates_tree_spacing.pdf},
  abstract = {{\textless}p{\textgreater}Does competition prevail in large size classes of trees in tropical forests? This question is fundamental to our understanding of the demography and dynamics occurring in rain forests. We investigated this question based on an undisturbed late-secondary forest on a 1-ha plot in central Cameroon. Trees were stem-mapped and classified into three size classes: understorey, midstorey and overstorey. The diameter at breast height and yearly biomass increment were determined as measures of plant growth and performance. Spatial statistics such as pair- and mark-correlation functions were used to detect scale-dependent patterns that could be caused by competition within and between the three size classes. The results revealed a random pattern and spatially uncorrelated measures of plant growth of overstorey trees. This suggests that competitive effects are of minor importance in the large size class of overstorey trees. Likewise, only weak evidence for competition between trees was found within the two lower size classes. However, negative distance correlations were found between the different size classes. We suggest that competition within height classes was relatively low due to the diversity of species with their variable niche differentiations and phenotypic plasticity that may compensate for competitive effects.{\textless}/p{\textgreater}},
  comment  = {public},
  doi      = {10.1017/S0266467410000453},
  isbn     = {0266-4674},
  keywords = {Cameroon,diversity,mark-correlation function,pair-correlation function,spatial patterns,tropical forest},
}

\textlessp\textgreaterDoes competition prevail in large size classes of trees in tropical forests? This question is fundamental to our understanding of the demography and dynamics occurring in rain forests. We investigated this question based on an undisturbed late-secondary forest on a 1-ha plot in central Cameroon. Trees were stem-mapped and classified into three size classes: understorey, midstorey and overstorey. The diameter at breast height and yearly biomass increment were determined as measures of plant growth and performance. Spatial statistics such as pair- and mark-correlation functions were used to detect scale-dependent patterns that could be caused by competition within and between the three size classes. The results revealed a random pattern and spatially uncorrelated measures of plant growth of overstorey trees. This suggests that competitive effects are of minor importance in the large size class of overstorey trees. Likewise, only weak evidence for competition between trees was found within the two lower size classes. However, negative distance correlations were found between the different size classes. We suggest that competition within height classes was relatively low due to the diversity of species with their variable niche differentiations and phenotypic plasticity that may compensate for competitive effects.\textless/p\textgreater

@Article{Rodriguez-Perez2011,
  author   = {Rodr{\'{i}}guez-P{\'{e}}rez, Javier and Wiegand, Kerstin and Ward, David},
  title    = {{Interaction between ungulates and bruchid beetles and its effect on Acacia trees: Modeling the costs and benefits of seed dispersal to plant demography}},
  journal  = {Oecologia},
  year     = {2011},
  volume   = {167},
  number   = {1},
  pages    = {97--105},
  issn     = {00298549},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e037c8fc5642d926e966229592cbd05c.pdf/Rodriguez_et_al_(2011)_Oecologica_seed_dispersal.pdf},
  abstract = {Integrative studies of plant-animal interactions that incorporate the multiple effects of interactions are important for discerning the importance of each factor within the population dynamics of a plant species. The low regeneration capacity of many Acacia species in arid savannas is a consequence of a combination of reduction in seed dispersal and high seed predation. Here we studied how ungulates (acting as both seed dispersers and herbivores) and bruchid beetles (post-dispersal seed predators) modulate the population dynamics of A. raddiana, a keystone species in the Middle East. We developed two simulation models of plant demography: the first included seed ingestion by ungulates and seed predation by bruchids, whereas the second model additionally incorporated herbivory by ungulates. We also included the interacting effects of seed removal and body mass, because larger ungulates destroy proportionally fewer seeds and enhance seed germination. Simulations showed that the negative effect of seed predation on acacia population size was compensated for by the positive effect of seed ingestion at 50 and 30{\%} seed removal under scenarios with and without herbivory, respectively. Smaller ungulates (e.g., {\textless}35 kg) must necessarily remove tenfold more seeds than larger ungulates (e.g., {\textgreater}250 kg) to compensate for the negative effect of seed predation. Seedling proportion increased with seed removal in the model with herbivory. Managing and restoring acacia seed dispersers is key to conserving acacia populations, because low-to-medium seed removal could quickly restore their regeneration capacity.},
  comment  = {public},
  doi      = {10.1007/s00442-011-1964-6},
  isbn     = {0029-8549},
  keywords = {Herbivory,Population growth rate,Seed predation,Seed removal,Simulation models},
  pmid     = {21442280},
}

Integrative studies of plant-animal interactions that incorporate the multiple effects of interactions are important for discerning the importance of each factor within the population dynamics of a plant species. The low regeneration capacity of many Acacia species in arid savannas is a consequence of a combination of reduction in seed dispersal and high seed predation. Here we studied how ungulates (acting as both seed dispersers and herbivores) and bruchid beetles (post-dispersal seed predators) modulate the population dynamics of A. raddiana, a keystone species in the Middle East. We developed two simulation models of plant demography: the first included seed ingestion by ungulates and seed predation by bruchids, whereas the second model additionally incorporated herbivory by ungulates. We also included the interacting effects of seed removal and body mass, because larger ungulates destroy proportionally fewer seeds and enhance seed germination. Simulations showed that the negative effect of seed predation on acacia population size was compensated for by the positive effect of seed ingestion at 50 and 30% seed removal under scenarios with and without herbivory, respectively. Smaller ungulates (e.g., \textless35 kg) must necessarily remove tenfold more seeds than larger ungulates (e.g., \textgreater250 kg) to compensate for the negative effect of seed predation. Seedling proportion increased with seed removal in the model with herbivory. Managing and restoring acacia seed dispersers is key to conserving acacia populations, because low-to-medium seed removal could quickly restore their regeneration capacity.

@Article{Schleicher2011,
  author   = {Schleicher, J. and Wiegand, K. and Ward, D.},
  title    = {{Changes of woody plant interaction and spatial distribution between rocky and sandy soil areas in a semi-arid savanna, South Africa}},
  journal  = {Journal of Arid Environments},
  year     = {2011},
  volume   = {75},
  number   = {3},
  pages    = {270--278},
  issn     = {01401963},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a11ecc362f62c37eb71f32a347caf044.pdf/Schleicher_et_al_(2011)_JAENVIRON_woody_plant_interactions.pdf},
  abstract = {We examined the impact of shrub-shrub interactions and soil type (rocky or sandy) on growth and spatial distribution of the two savanna shrub species Tarchonanthus camphoratus and Acacia mellifera. To explore plant interactions, we compared the size of juvenile and mature T. camphoratus shrubs between different locations (under the subcanopy of A. mellifera and in the open). Juvenile T. camphoratus shrubs had similar sizes regardless of location; however, in rocky soil, mature shrubs in the open were larger than those near A. mellifera, implying an inter-specific competitive effect of A. mellifera on T. camphoratus. Juvenile T. camphoratus shrubs grew faster in the sandy than in the rocky area. Furthermore, we used the Wiegand-Moloney O-ring statistics to explore the spatial distribution of T. camphoratus. T. camphoratus showed spatial aggregation, but in the rocky area T. camphoratus juveniles were positively associated with A. mellifera (indicating facilitation as the pattern-creating process), whereas in the sandy area they were positively associated with mature T. camphoratus shrubs (indicating seed dispersal as the pattern-creating process). T. camphoratus exhibited encroachment potential in the sandy area. We showed how spatial pattern analysis can help to explore processes determining woody plant spacing and recommend its further use. {\textcopyright} 2010 Elsevier Ltd.},
  comment  = {public},
  doi      = {10.1016/j.jaridenv.2010.10.003},
  isbn     = {0140-1963},
  keywords = {O-ring function,Plant-plant interactions,Savanna shrubs,Spatial ecology,Tarchonanthus camphoratus,Toroidal shift},
}

We examined the impact of shrub-shrub interactions and soil type (rocky or sandy) on growth and spatial distribution of the two savanna shrub species Tarchonanthus camphoratus and Acacia mellifera. To explore plant interactions, we compared the size of juvenile and mature T. camphoratus shrubs between different locations (under the subcanopy of A. mellifera and in the open). Juvenile T. camphoratus shrubs had similar sizes regardless of location; however, in rocky soil, mature shrubs in the open were larger than those near A. mellifera, implying an inter-specific competitive effect of A. mellifera on T. camphoratus. Juvenile T. camphoratus shrubs grew faster in the sandy than in the rocky area. Furthermore, we used the Wiegand-Moloney O-ring statistics to explore the spatial distribution of T. camphoratus. T. camphoratus showed spatial aggregation, but in the rocky area T. camphoratus juveniles were positively associated with A. mellifera (indicating facilitation as the pattern-creating process), whereas in the sandy area they were positively associated with mature T. camphoratus shrubs (indicating seed dispersal as the pattern-creating process). T. camphoratus exhibited encroachment potential in the sandy area. We showed how spatial pattern analysis can help to explore processes determining woody plant spacing and recommend its further use. © 2010 Elsevier Ltd.

@Article{Schleicher2011a,
  author   = {Schleicher, Jana and Meyer, Katrin M. and Wiegand, Kerstin and Schurr, Frank M. and Ward, David},
  title    = {{Disentangling facilitation and seed dispersal from environmental heterogeneity as mechanisms generating associations between savanna plants}},
  journal  = {Journal of Vegetation Science},
  year     = {2011},
  volume   = {22},
  number   = {6},
  pages    = {1038--1048},
  issn     = {11009233},
  url_pdf  = {http://uni-goettingen.de/de/document/download/88c9eedd83a3359832674dd8387c1ebe.pdf/SchleicherMeyerWiegandSchurrWard_(2011)_JVEGSCI_savanna_facilitation.pdf},
  abstract = {Question: How can we disentangle facilitation and seed dispersal from environmental heterogeneity as mechanisms causing spatial associations of plant species? Location: Semi-arid savanna in the Kimberley Thorn Bushveld, South Africa. Methods: We developed a two-step protocol for the statistical differentiation of association-promoting mechanisms in plants based on the Acacia erioloba-Grewia flava association. Individuals of the savanna shrub G. flava and the tree A. erioloba were mapped on four study plots. Disentangling the mechanism causing the association of G. flava and A. erioloba involved tests of three spatial and one non-spatial null model. The spatial null models include homogeneous and heterogeneous Poisson processes for spatial randomness based on the bivariate spatial point patterns of the four plots. With the non-spatial analysis, we determined the relationship between the canopy diameter of A. erioloba trees and presence or absence of G. flava shrubs in the tree understorey to find whether shrub presence requires a minimum tree canopy diameter. Results: We first showed a significant positive spatial association of the two species. Thereafter, the non-spatial analysis supported an exclusion of environmental heterogeneity as the sole cause of this positive association. We found a minimum tree size under which no G. flava shrubs occurred. Conclusions: Our two-step analysis showed that it is unlikely that heterogeneous environmental conditions caused the spatial association of A. erioloba and G. flava. Instead, this association may have been caused by seed dispersal and/or facilitation (e.g. caused by hydraulic lift and/or nitrogen fixation by the host tree).},
  comment  = {public},
  doi      = {10.1111/j.1654-1103.2011.01310.x},
  isbn     = {1654-1103},
  keywords = {Acacia erioloba,Grewia flava,Plant interactions,Spatial association,Wiegand-Moloney O-ring statistics},
}

Question: How can we disentangle facilitation and seed dispersal from environmental heterogeneity as mechanisms causing spatial associations of plant species? Location: Semi-arid savanna in the Kimberley Thorn Bushveld, South Africa. Methods: We developed a two-step protocol for the statistical differentiation of association-promoting mechanisms in plants based on the Acacia erioloba-Grewia flava association. Individuals of the savanna shrub G. flava and the tree A. erioloba were mapped on four study plots. Disentangling the mechanism causing the association of G. flava and A. erioloba involved tests of three spatial and one non-spatial null model. The spatial null models include homogeneous and heterogeneous Poisson processes for spatial randomness based on the bivariate spatial point patterns of the four plots. With the non-spatial analysis, we determined the relationship between the canopy diameter of A. erioloba trees and presence or absence of G. flava shrubs in the tree understorey to find whether shrub presence requires a minimum tree canopy diameter. Results: We first showed a significant positive spatial association of the two species. Thereafter, the non-spatial analysis supported an exclusion of environmental heterogeneity as the sole cause of this positive association. We found a minimum tree size under which no G. flava shrubs occurred. Conclusions: Our two-step analysis showed that it is unlikely that heterogeneous environmental conditions caused the spatial association of A. erioloba and G. flava. Instead, this association may have been caused by seed dispersal and/or facilitation (e.g. caused by hydraulic lift and/or nitrogen fixation by the host tree).

@InProceedings{VonLupke2011,
  author    = {von L{\"{u}}pke, Nikolas and Nagel, J{\"{u}}rgen and Saborowski, Joachim},
  booktitle = {Deutscher Verband Forstlicher Forschungsanstalten, Sektion Forstliche Biometrie und Informatik - 22.Tagung},
  title     = {{Zusammengesetzte Sch{\"{a}}tzer f{\"{u}}r periodische Waldinventuren}},
  year      = {2011},
  pages     = {13--21},
  comment   = {public},
  groups    = {Jana:1},
}

@Article{Brinker2010,
  author   = {Brinker, M. and Brosche, M. and Vinocur, B. and Abo-Ogiala, A. and Fayyaz, P. and Janz, D. and Ottow, E. A. and Cullmann, A. D. and Saborowski, J. and Kangasjarvi, J. and Altman, A. and Polle, A.},
  title    = {{Linking the Salt Transcriptome with Physiological Responses of a Salt-Resistant Populus Species as a Strategy to Identify Genes Important for Stress Acclimation}},
  journal  = {PLANT PHYSIOLOGY},
  year     = {2010},
  volume   = {154},
  number   = {4},
  pages    = {1697--1709},
  issn     = {0032-0889},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e39ccdc83b5019bcab0fcf7b6d12ec11.pdf/Brinker%20etal_(2010)_PlantPhys_StressAcclimation.pdf},
  abstract = {To investigate early salt acclimation mechanisms in a salt-tolerant poplar species (Populus euphratica), the kinetics of molecular, metabolic, and physiological changes during a 24-h salt exposure were measured. Three distinct phases of salt stress were identified by analyses of the osmotic pressure and the shoot water potential: dehydration, salt accumulation, and osmotic restoration associated with ionic stress. The duration and intensity of these phases differed between leaves and roots. Transcriptome analysis using P. euphratica-specific microarrays revealed clusters of coexpressed genes in these phases, with only 3{\%} overlapping salt-responsive genes in leaves and roots. Acclimation of cellular metabolism to high salt concentrations involved remodeling of amino acid and protein biosynthesis and increased expression of molecular chaperones (dehydrins, osmotin). Leaves suffered initially from dehydration, which resulted in changes in transcript levels of mitochondrial and photosynthetic genes, indicating adjustment of energy metabolism. Initially, decreases in stress-related genes were found, whereas increases occurred only when leaves had restored the osmotic balance by salt accumulation. Comparative in silico analysis of the poplar stress regulon with Arabidopsis (Arabidopsis thaliana) orthologs was used as a strategy to reduce the number of candidate genes for functional analysis. Analysis of Arabidopsis knockout lines identified a lipocalin-like gene (AtTIL) and a gene encoding a protein with previously unknown functions (AtSIS) to play roles in salt tolerance. In conclusion, by dissecting the stress transcriptome of tolerant species, novel genes important for salt endurance can be identified},
  comment  = {public},
  doi      = {10.1104/pp.110.164152},
  isbn     = {0032-0889},
  pmid     = {20959419},
  url      = {http://www.plantphysiol.org/cgi/doi/10.1104/pp.110.164152},
}

To investigate early salt acclimation mechanisms in a salt-tolerant poplar species (Populus euphratica), the kinetics of molecular, metabolic, and physiological changes during a 24-h salt exposure were measured. Three distinct phases of salt stress were identified by analyses of the osmotic pressure and the shoot water potential: dehydration, salt accumulation, and osmotic restoration associated with ionic stress. The duration and intensity of these phases differed between leaves and roots. Transcriptome analysis using P. euphratica-specific microarrays revealed clusters of coexpressed genes in these phases, with only 3% overlapping salt-responsive genes in leaves and roots. Acclimation of cellular metabolism to high salt concentrations involved remodeling of amino acid and protein biosynthesis and increased expression of molecular chaperones (dehydrins, osmotin). Leaves suffered initially from dehydration, which resulted in changes in transcript levels of mitochondrial and photosynthetic genes, indicating adjustment of energy metabolism. Initially, decreases in stress-related genes were found, whereas increases occurred only when leaves had restored the osmotic balance by salt accumulation. Comparative in silico analysis of the poplar stress regulon with Arabidopsis (Arabidopsis thaliana) orthologs was used as a strategy to reduce the number of candidate genes for functional analysis. Analysis of Arabidopsis knockout lines identified a lipocalin-like gene (AtTIL) and a gene encoding a protein with previously unknown functions (AtSIS) to play roles in salt tolerance. In conclusion, by dissecting the stress transcriptome of tolerant species, novel genes important for salt endurance can be identified

@Article{Cullmann2010,
  author   = {Cullmann, Andreas Dominik and Saborowski, Joachim},
  title    = {{Conditional versus unconditional mean-squared prediction errors for Gaussian processes with constant but unknown mean}},
  journal  = {Environmetrics},
  year     = {2010},
  volume   = {21},
  number   = {5},
  pages    = {541--548},
  issn     = {11804009},
  url_pdf  = {http://uni-goettingen.de/de/document/download/6358747c10f3cbc3b3fc0010bc86f667.pdf/Cullmann_Saborowski_(2010)_ENVIRONMETRICS_mean_squared_predictions.pdf},
  comment  = {public},
  doi      = {10.1002/env.1015},
  keywords = {Conditional mean squared prediction error,Gaussian random field,Ordinary kriging},
}

@Article{Djomo2010,
  author   = {Djomo, Adrien N. and Ibrahima, Adamou and Saborowski, Joachim and Gravenhorst, Gode},
  title    = {{Allometric equations for biomass estimations in Cameroon and pan moist tropical equations including biomass data from Africa}},
  journal  = {Forest Ecology and Management},
  year     = {2010},
  volume   = {260},
  number   = {10},
  pages    = {1873--1885},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/4df40c701547ab5773871feade802dc2.pdf/Djomo_et_al_(2010)_FORECOLMANAG_allometric_equations.pdf},
  abstract = {Moist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa. Mixed-species regression equations with 71 sample trees using different input variables such as diameter, diameter and height, product of diameter and height, and wood density were developed to estimate total aboveground biomass and biomass of leaves and branches for a Cameroon forest. Our biomass data was added to 372 biomass data collected across different moist tropical forests in Asia and South America to develop new pan moist tropical allometric regressions. Species-specific and mixed-species height diameter regression models were also developed to estimate heights using 3833 trees. Using only diameter as input variable, the mixed-species regression model estimates the aboveground biomass of the study site with an average error of 7.4{\%}. Adding height or wood density did not improve significantly the estimations. Using the three variables together improved the precision with an average error of 3.4{\%}. For general allometric equations tree height was a good predictor variable. The best pan moist tropical equation was obtained when the three variables were added together followed by the one which includes diameter and height. This study provides height diameter relationships and wood density of 31 species. The pan moist tropical equation developed by Chave et al. (2005), estimates total aboveground biomass across different sites with an average error of 20.3{\%} followed by equations developed in the present study with an average error of 29.5{\%}. {\textcopyright} 2010 Elsevier B.V.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2010.08.034},
  isbn     = {0378-1127},
  keywords = {Biomass,Cameroon,Moist tropical forests,Tree allometry},
}

Moist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa. Mixed-species regression equations with 71 sample trees using different input variables such as diameter, diameter and height, product of diameter and height, and wood density were developed to estimate total aboveground biomass and biomass of leaves and branches for a Cameroon forest. Our biomass data was added to 372 biomass data collected across different moist tropical forests in Asia and South America to develop new pan moist tropical allometric regressions. Species-specific and mixed-species height diameter regression models were also developed to estimate heights using 3833 trees. Using only diameter as input variable, the mixed-species regression model estimates the aboveground biomass of the study site with an average error of 7.4%. Adding height or wood density did not improve significantly the estimations. Using the three variables together improved the precision with an average error of 3.4%. For general allometric equations tree height was a good predictor variable. The best pan moist tropical equation was obtained when the three variables were added together followed by the one which includes diameter and height. This study provides height diameter relationships and wood density of 31 species. The pan moist tropical equation developed by Chave et al. (2005), estimates total aboveground biomass across different sites with an average error of 20.3% followed by equations developed in the present study with an average error of 29.5%. © 2010 Elsevier B.V.

@Article{Hol2010,
  author   = {Hol, W. H. G. and de Boer, Wietse and Termorshuizen, Aad J. and Meyer, Katrin M. and Schneider, Johannes H M and van Dam, Nicole M. and van Veen, Johannes A. and van der Putten, Wim H.},
  title    = {{Reduction of rare soil microbes modifies plant-herbivore interactions}},
  journal  = {Ecology Letters},
  year     = {2010},
  volume   = {13},
  number   = {3},
  pages    = {292--301},
  issn     = {14610248},
  url_pdf  = {http://uni-goettingen.de/de/document/download/9588ebec1f9adcd96d0670ecb74e6ea9.pdf/Hol_et_al_(2010)_ECOLLETTERS_plant_herbivore_interactions.pdf},
  abstract = {Rare species are assumed to have little impact on community interactions and ecosystem processes. However, very few studies have actually attempted to quantify the role of rare species in ecosystems. Here we compare effects of soil community assemblages on plant-herbivore interactions and show that reduction of rare soil microbes increases both plant biomass and plant nutritional quality. Two crop plant species growing in soil where rare microbes were reduced, had tissues of higher nutritional quality, which theoretically makes them more susceptible to pest organisms such as shoot-feeding aphids and root-feeding nematodes. Reduction of rare microbes increased aphid body size in the absence of nematodes; nematodes always reduced aphid body size independent of the soil microbial community. This study is the first to show that rare soil microbes are not redundant but may play a role in crop protection by enhancing aboveground and belowground plant defence. It remains to be tested whether these are direct effects of rare soil microbes on plants and herbivores, or indirect effects via shifts in the microbial soil community assemblages.},
  comment  = {public},
  doi      = {10.1111/j.1461-0248.2009.01424.x},
  isbn     = {1461-023X},
  keywords = {Biodiversity,Dominant,Species interactions},
  pmid     = {20070364},
}

Rare species are assumed to have little impact on community interactions and ecosystem processes. However, very few studies have actually attempted to quantify the role of rare species in ecosystems. Here we compare effects of soil community assemblages on plant-herbivore interactions and show that reduction of rare soil microbes increases both plant biomass and plant nutritional quality. Two crop plant species growing in soil where rare microbes were reduced, had tissues of higher nutritional quality, which theoretically makes them more susceptible to pest organisms such as shoot-feeding aphids and root-feeding nematodes. Reduction of rare microbes increased aphid body size in the absence of nematodes; nematodes always reduced aphid body size independent of the soil microbial community. This study is the first to show that rare soil microbes are not redundant but may play a role in crop protection by enhancing aboveground and belowground plant defence. It remains to be tested whether these are direct effects of rare soil microbes on plants and herbivores, or indirect effects via shifts in the microbial soil community assemblages.

@Article{Meyer2010,
  author   = {Meyer, Katrin M. and Jopp, Fred and M{\"{u}}nkem{\"{u}}ller, Tamara and Reuter, Hauke and Schiffers, Katja},
  title    = {{Crossing scales in ecology}},
  journal  = {Basic and Applied Ecology},
  year     = {2010},
  volume   = {11},
  number   = {7},
  pages    = {561--562},
  issn     = {14391791},
  url_pdf  = {http://uni-goettingen.de/de/document/download/86602df5a6a896d105d6347665a4d402.pdf/Meyer_et_al_(2010)_BAPPLECOL_crossing_scales.pdf},
  abstract = {Export Date: 29 December 2010},
  comment  = {public},
  doi      = {10.1016/j.baae.2010.08.003},
  isbn     = {1439-1791},
}

Export Date: 29 December 2010

@Article{Meyer2010a,
  author   = {Meyer, Katrin M. and Schiffers, Katja and M{\"{u}}nkem{\"{u}}ller, Tamara and Sch{\"{a}}dler, Martin and Calabrese, Justin M. and Basset, Alberto and Breulmann, Marc and Duquesne, Sabine and Hidding, Bert and Huth, Andreas and Sch{\"{o}}b, Christian and van de Voorde, Tess F J},
  title    = {{Predicting population and community dynamics: The type of aggregation matters}},
  journal  = {Basic and Applied Ecology},
  year     = {2010},
  volume   = {11},
  number   = {7},
  pages    = {563--571},
  issn     = {14391791},
  url_pdf  = {http://uni-goettingen.de/de/document/download/51793020363d4f587c022ffe04f6c377.pdf/Meyer_et_al_(2010)_ECOLMODEL_predicting_dynamics.pdf},
  abstract = {When investigating complex ecological dynamics at the population or community level, we necessarily need to abstract and aggregate ecological information. The way in which information is aggregated may be crucial for the outcome of the study. In this paper, we suggest that in addition to the traditional spatial, temporal and organizational levels, we need a more flexible framework linking ecological processes, study objects and types of aggregation. We develop such a framework and exemplify the most commonly used types of aggregation and their potential influence on identifiable drivers of community dynamics. We also illustrate strategies to narrow down the range of possible aggregation types for a particular study. With this approach, we hope (i) to clarify the function of aggregation types as related to traditional ecological levels and (ii) to raise the awareness of how important a deliberate way of aggregating ecological information is for a sound and reliable outcome of any empirical or theoretical ecological study. {\textcopyright} 2010 Gesellschaft f{\"{u}}r {\"{O}}kologie.},
  comment  = {public},
  doi      = {10.1016/j.baae.2010.08.001},
  isbn     = {1439-1791},
  keywords = {Body size class,Functional type,Genotype,Organizational level,Pattern-process relationship,Phenotype,Scales,Species,Study design,Trophic guild},
}

When investigating complex ecological dynamics at the population or community level, we necessarily need to abstract and aggregate ecological information. The way in which information is aggregated may be crucial for the outcome of the study. In this paper, we suggest that in addition to the traditional spatial, temporal and organizational levels, we need a more flexible framework linking ecological processes, study objects and types of aggregation. We develop such a framework and exemplify the most commonly used types of aggregation and their potential influence on identifiable drivers of community dynamics. We also illustrate strategies to narrow down the range of possible aggregation types for a particular study. With this approach, we hope (i) to clarify the function of aggregation types as related to traditional ecological levels and (ii) to raise the awareness of how important a deliberate way of aggregating ecological information is for a sound and reliable outcome of any empirical or theoretical ecological study. © 2010 Gesellschaft für Ökologie.

@Incollection{Meyer2010b,
  author    = {Meyer, Katrin M. and Wiegand, Kerstin and Ward, David},
  title     = {{Spatially explicit modelling of savanna processes}},
  booktitle = {Ecosystem Function in Savannas: Measurement and Modeling at Landscape to Global Scales},
  publisher = {Taylor {\&} Francis},
  year      = {2010},
  editor    = {{Hill, M.J. {\&} Hanan}, M.P.},
  url_pdf   = {http://uni-goettingen.de/de/document/download/d4fb84ed27aeef528208423f9e39e04a.pdf/Meyer_et_al_(2007)_BOOK_spatially_explicit_modelling.pdf},
  comment   = {public},
}

@Article{Moustakas2010,
  author  = {Moustakas, Aristides and Wiegand, Kerstin and Meyer, Katrin M. and Ward, David and Sankaran, M.},
  title   = {{Learning new tricks from old trees: revisiting the savanna question}},
  journal = {Frontiers of Biogeography},
  year    = {2010},
  volume  = {2},
  pages   = {47--53},
  url_pdf = {http://uni-goettingen.de/de/document/download/d851c317c346b6adc145b6bfcfa2bc2e.pdf/Moustakas_et_al_(2010)_FRONTBIOGEO_new_tricks_from_old_trees.pdf},
  comment = {public},
}

@Article{Nothdurft2010,
  author   = {Nothdurft, Arne and Saborowski, Joachim and Nuske, Robert S. and Stoyan, Dietrich},
  title    = {{Density estimation based on k-tree sampling and point pattern reconstruction}},
  journal  = {Canadian Journal of Forest Research},
  year     = {2010},
  volume   = {40},
  number   = {5},
  pages    = {953--967},
  issn     = {00455067},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e28a2172e292fc39496e3bb72011abaf.pdf/Nothdurft_et_al_(2010)_CanadJFR_density_estimation.pdf},
  abstract = {In k-tree sampling, also referred to as point-to-tree distance sampling, the k nearest trees are measured. The problem associated with k-tree sampling is its lack of unbiased density estimators. The presented density estimator based on point pattern reconstruction remedies that shortcoming. It requires the coordinates of all k trees. These coordinates are translated into a simulation window where they remain unchanged. Empirical cumulative distribution functions of intertree and location-to-tree distances estimated from the sample plots are set as target characteristics. Using the idea of simulated annealing, an optimal new tree pattern is constructed in the simulation window outside the k-tree samples. The reconstruction of the point pattern minimizes the contrast between the empirical cumulative distribution functions and their analogs for the simulated pattern. The density estimator is simply the tree density of the optimum pattern in the simulation window. The performance of the reconstruction-based density estimator is assessed for k = 6 and k = 4 based on systematic sampling grids regarding its potential application in forest inventories. Simulations are carried out using real stem maps (covering different stand densities and different types of spatial point patterns, such as regular, clustered, and random) as well as completely random patterns. The new density estimator proves to be empirically superior in terms of bias and root mean squared error compared with commonly used estimators. The reconstruction-based density estimator has biases smaller than 2{\%}. En {\'{e}}chantillonnage de k arbres, aussi appel{\'{e}} {\'{e}}chantillonnage de k arbres selon leur distance, on mesure les k arbres les plus proches. Le probl{\`{e}}me li{\'{e}} {\`{a}} l'{\'{e}}chantillonnage de k arbres est son incapacit{\'{e}} {\`{a}} fournir des estimateurs de densit{\'{e}} sans biais. L'estimateur de densit{\'{e}} bas{\'{e}} sur la reconstruction du patron des points comble cette lacune. Il requiert les coordonn{\'{e}}es de tous les k arbres. Ces coordonn{\'{e}}es sont traduites dans une fen{\^{e}}tre de simulation o{\`{u}} elles demeurent inchang{\'{e}}es. Les fonctions empiriques de distribution cumulative de distances entre les arbres et entre un point et les arbres estim{\'{e}}es {\`{a}} partir des placettes {\'{e}}chantillons sont les caract{\'{e}}ristiques cibles. En utilisant le recuit simul{\'{e}}, un nouveau patron optimal des arbres est construit dans la fen{\^{e}}tre de simulation en dehors des k arbres {\'{e}}chantillons. La reconstruction du patron de points minimise le contraste entre les fonctions empiriques et leurs analogues d{\'{e}}riv{\'{e}}s du patron simul{\'{e}}. L'estimateur de densit{\'{e}} est tout simplement la densit{\'{e}} des arbres de la structure optimale dans la fen{\^{e}}tre de simulation. La performance de l'estimateur de densit{\'{e}} bas{\'{e}} sur la reconstruction est {\'{e}}valu{\'{e}}e pour k = 6 et k = 4 sur la base des grilles d'{\'{e}}chantillonnage syst{\'{e}}matique quant {\`{a}} son application potentielle dans les inventaires forestiers. Des simulations sont effectu{\'{e}}es en utilisant les cartes r{\'{e}}elles des tiges (couvrant diff{\'{e}}rentes densit{\'{e}}s de peuplement et diff{\'{e}}rents types de patrons spatiaux de points, tels que r{\'{e}}gulier, en grappe et al{\'{e}}atoire) aussi bien que des patrons compl{\`{e}}tement al{\'{e}}atoires. Le nouvel estimateur de densit{\'{e}} s'av{\`{e}}re empiriquement sup{\'{e}}rieur en termes de biais et d'erreur quadratique moyenne par rapport aux estimateurs fr{\'{e}}quemment utilis{\'{e}}s. Son biais est inf{\'{e}}rieur {\`{a}} 2{\%}.},
  comment  = {public},
  doi      = {10.1139/X10-046},
  url      = {http://content.ebscohost.com/ContentServer.asp?T=P{\&}P=AN{\&}K=50395587{\&}S=R{\&}D=afh{\&}EbscoContent=dGJyMNXb4kSep644v+bwOLCmr0ueprFSs624SrCWxWXS{\&}ContentCustomer=dGJyMPGqtku2rbZKuePfgeyx44Dt6fIA{\%}5Cnhttp://content.ebscohost.com/ContentServer.asp?T=P{\&}P=AN{\&}K=50395587{\&}S},
}

In k-tree sampling, also referred to as point-to-tree distance sampling, the k nearest trees are measured. The problem associated with k-tree sampling is its lack of unbiased density estimators. The presented density estimator based on point pattern reconstruction remedies that shortcoming. It requires the coordinates of all k trees. These coordinates are translated into a simulation window where they remain unchanged. Empirical cumulative distribution functions of intertree and location-to-tree distances estimated from the sample plots are set as target characteristics. Using the idea of simulated annealing, an optimal new tree pattern is constructed in the simulation window outside the k-tree samples. The reconstruction of the point pattern minimizes the contrast between the empirical cumulative distribution functions and their analogs for the simulated pattern. The density estimator is simply the tree density of the optimum pattern in the simulation window. The performance of the reconstruction-based density estimator is assessed for k = 6 and k = 4 based on systematic sampling grids regarding its potential application in forest inventories. Simulations are carried out using real stem maps (covering different stand densities and different types of spatial point patterns, such as regular, clustered, and random) as well as completely random patterns. The new density estimator proves to be empirically superior in terms of bias and root mean squared error compared with commonly used estimators. The reconstruction-based density estimator has biases smaller than 2%. En échantillonnage de k arbres, aussi appelé échantillonnage de k arbres selon leur distance, on mesure les k arbres les plus proches. Le problème lié à l'échantillonnage de k arbres est son incapacité à fournir des estimateurs de densité sans biais. L'estimateur de densité basé sur la reconstruction du patron des points comble cette lacune. Il requiert les coordonnées de tous les k arbres. Ces coordonnées sont traduites dans une fenêtre de simulation où elles demeurent inchangées. Les fonctions empiriques de distribution cumulative de distances entre les arbres et entre un point et les arbres estimées à partir des placettes échantillons sont les caractéristiques cibles. En utilisant le recuit simulé, un nouveau patron optimal des arbres est construit dans la fenêtre de simulation en dehors des k arbres échantillons. La reconstruction du patron de points minimise le contraste entre les fonctions empiriques et leurs analogues dérivés du patron simulé. L'estimateur de densité est tout simplement la densité des arbres de la structure optimale dans la fenêtre de simulation. La performance de l'estimateur de densité basé sur la reconstruction est évaluée pour k = 6 et k = 4 sur la base des grilles d'échantillonnage systématique quant à son application potentielle dans les inventaires forestiers. Des simulations sont effectuées en utilisant les cartes réelles des tiges (couvrant différentes densités de peuplement et différents types de patrons spatiaux de points, tels que régulier, en grappe et aléatoire) aussi bien que des patrons complètement aléatoires. Le nouvel estimateur de densité s'avère empiriquement supérieur en termes de biais et d'erreur quadratique moyenne par rapport aux estimateurs fréquemment utilisés. Son biais est inférieur à 2%.

@Inproceedings{Ritter2010,
  author    = {Ritter, T. and Saborowski, J.},
  title     = {{Effiziente Totholzinventuren mit Point Transect Sampling - Projektvorstellung, Methodenvergleich und erste Zwischenergebnisse}},
  booktitle = {Deutscher Verband Forstlicher Forschungsanstalten, Sektion Forstliche Biometrie und Informatik - 21. Tagung},
  year      = {2010},
  pages     = {23--30},
  url_pdf   = {http://uni-goettingen.de/de/document/download/a13d38b45b83875afee00d645e046b96.pdf/ritter_saborowski_(2010)_DVFF_effiziente_Totholzinventuren.pdf},
  comment   = {public},
}

@Article{Saborowski2010,
  author   = {Saborowski, Joachim and Marx, Almuth and Nagel, J{\"{u}}rgen and B{\"{o}}ckmann, Thomas},
  title    = {{Double sampling for stratification in periodic inventories-Infinite population approach}},
  journal  = {Forest Ecology and Management},
  year     = {2010},
  volume   = {260},
  number   = {10},
  pages    = {1886--1895},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ae305f10b0cfb62a0580a11cbf699954.pdf/Saborowski_et_al_(2010)_FORECOLMANAG_infinite_population_approach.pdf},
  abstract = {Double sampling for stratification is a sampling design that is widely used for forest and other resource inventories in forest ecosystems. It is shown that this sampling design can be adapted to repeated inventories including estimators of net change, even for non-proportional allocation of second-phase units and periodically updated stratification. The method accounts for the transition of sampling units among strata. Moreover, it may outperform classical single phase designs if sample plots are appropriately allocated to strata with respect to predefined target variables, here: volume per ha of bigger trees of the main tree species. The latter requires a clear definition of predominant aims of the inventory and an appropriate optimization method. Access to inventory data of a state forest district from two occasions allowed for an optimization of the design based on the first occasion, which proved to be still advantageous on the following occasion. Estimators are developed under the infinite population approach, which is generally deemed more appropriate for forest inventories. {\textcopyright} 2010 Elsevier B.V.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2010.08.035},
  isbn     = {0304-4076},
  keywords = {Continuous forest inventory,Infinite population approach,Multi-purpose optimization,Two-phase sampling for stratification},
  pmid     = {22059587},
}

Double sampling for stratification is a sampling design that is widely used for forest and other resource inventories in forest ecosystems. It is shown that this sampling design can be adapted to repeated inventories including estimators of net change, even for non-proportional allocation of second-phase units and periodically updated stratification. The method accounts for the transition of sampling units among strata. Moreover, it may outperform classical single phase designs if sample plots are appropriately allocated to strata with respect to predefined target variables, here: volume per ha of bigger trees of the main tree species. The latter requires a clear definition of predominant aims of the inventory and an appropriate optimization method. Access to inventory data of a state forest district from two occasions allowed for an optimization of the design based on the first occasion, which proved to be still advantageous on the following occasion. Estimators are developed under the infinite population approach, which is generally deemed more appropriate for forest inventories. © 2010 Elsevier B.V.

@Article{Sher2010,
  author   = {Sher, A. A. and Wiegand, K. and Ward, D.},
  title    = {{Do Acacia and Tamarix trees compete for water in the Negev desert?}},
  journal  = {Journal of Arid Environments},
  year     = {2010},
  volume   = {74},
  number   = {3},
  pages    = {338--343},
  issn     = {01401963},
  url_pdf  = {http://uni-goettingen.de/de/document/download/8bf3566ebc93034b22995c56dad94cbe.pdf/Sher_et_al_(2010)_JAENVIRON_Acacia_water_compete.pdf},
  abstract = {We investigated the spatial distribution of the three Acacia and two Tamarix tree species and related the spatial distribution of these two genera to their 18O value, i.e. their 18O/16O isotopic ratio in the Negev desert, Israel. At the regional spatial scale, there was a significant difference in the overall distributions of these two genera, although there was considerable overlap. At the 1 km2 scale, there was no deviation from homogeneity. At a finer scale, no deviation from a random distribution was found in three ephemeral rivers between the two largest trees in these two genera, Acacia raddiana and Tamarix nilotica. We found that Tamarix used deep water from aquifers while Acacia trees used an alternate source, most likely surface water. Spatial segregation of Tamarix and Acacia occurs at the large spatial scale but not at the small scale, perhaps because of the high tolerance of Tamarix species for salinity and the low tolerance of Acacia species for saline conditions. It appears that the trees are not spatially segregated on the small scale because they use different water sources. {\textcopyright} 2009 Elsevier Ltd. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.jaridenv.2009.09.007},
  isbn     = {0140-1963},
  keywords = {Acacia gerrardii,Acacia raddiana,Acacia tortilis,Coexistence,Israel,Spatial ecology,Tamarix aphylla,Tamarix nilotica},
}

We investigated the spatial distribution of the three Acacia and two Tamarix tree species and related the spatial distribution of these two genera to their 18O value, i.e. their 18O/16O isotopic ratio in the Negev desert, Israel. At the regional spatial scale, there was a significant difference in the overall distributions of these two genera, although there was considerable overlap. At the 1 km2 scale, there was no deviation from homogeneity. At a finer scale, no deviation from a random distribution was found in three ephemeral rivers between the two largest trees in these two genera, Acacia raddiana and Tamarix nilotica. We found that Tamarix used deep water from aquifers while Acacia trees used an alternate source, most likely surface water. Spatial segregation of Tamarix and Acacia occurs at the large spatial scale but not at the small scale, perhaps because of the high tolerance of Tamarix species for salinity and the low tolerance of Acacia species for saline conditions. It appears that the trees are not spatially segregated on the small scale because they use different water sources. © 2009 Elsevier Ltd. All rights reserved.

@Article{Meyer2009,
  author   = {Meyer, Katrin M. and Mooij, Wolf M. and Vos, Matthijs and Hol, W. H Gera and van der Putten, Wim H.},
  title    = {{The power of simulating experiments}},
  journal  = {Ecological Modelling},
  year     = {2009},
  volume   = {220},
  number   = {19},
  pages    = {2594--2597},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/053bec199c7c0ae4dd5efcd2fb346795.pdf/Meyer_et_al_(2009)_EcolModel_Simulating_experiments.pdf},
  abstract = {Addressing complex ecological research questions often requires complex empirical experiments. However, due to the logistic constraints of empirical studies there is a trade-off between the complexity of experimental designs and sample size. Here, we explore if the simulation of complex ecological experiments including stochasticity-induced variation can aid in alleviating the sample size limitation of empirical studies. One area where sample size limitations constrain empirical approaches is in studies of the above- and belowground controls of trophic structure. Based on a rule- and individual-based simulation model on the effect of above- and belowground herbivores and their enemies on plant biomass, we evaluate the reliability of biomass estimates, the probability of experimental failure in terms of missing values, and the statistical power of biomass comparisons for a range of sample sizes. As expected, we observed superior performance of setups with sample sizes typical of simulations (n = 1000) as compared to empirical experiments (n = 10). At low sample sizes, simulated standard errors were smaller than expected from statistical theory, indicating that stochastic simulation models may be required in those cases where it is not possible to perform pilot studies for determining sample sizes. To avoid experimental failure, a sample size of n = 30 was required. In conclusion, we propose that the standard tool box of any ecologist should comprise a combination of simulation and empirical approaches to benefit from the realism of empirical experiments as well as the statistical power of simulations. {\textcopyright} 2009 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2009.06.001},
  isbn     = {0304-3800},
  keywords = {Experimental design,Individual-based simulation model,Replication,Sample size,Statistical power,Stochasticity},
}

Addressing complex ecological research questions often requires complex empirical experiments. However, due to the logistic constraints of empirical studies there is a trade-off between the complexity of experimental designs and sample size. Here, we explore if the simulation of complex ecological experiments including stochasticity-induced variation can aid in alleviating the sample size limitation of empirical studies. One area where sample size limitations constrain empirical approaches is in studies of the above- and belowground controls of trophic structure. Based on a rule- and individual-based simulation model on the effect of above- and belowground herbivores and their enemies on plant biomass, we evaluate the reliability of biomass estimates, the probability of experimental failure in terms of missing values, and the statistical power of biomass comparisons for a range of sample sizes. As expected, we observed superior performance of setups with sample sizes typical of simulations (n = 1000) as compared to empirical experiments (n = 10). At low sample sizes, simulated standard errors were smaller than expected from statistical theory, indicating that stochastic simulation models may be required in those cases where it is not possible to perform pilot studies for determining sample sizes. To avoid experimental failure, a sample size of n = 30 was required. In conclusion, we propose that the standard tool box of any ecologist should comprise a combination of simulation and empirical approaches to benefit from the realism of empirical experiments as well as the statistical power of simulations. © 2009 Elsevier B.V. All rights reserved.

@Article{Meyer2009a,
  author   = {Meyer, Katrin M. and Vos, Matthijs and Mooij, Wolf M. and {Gera Hol}, W. H. and Termorshuizen, Aad J. and Vet, Louise E M and {Van Der Putten}, Wim H.},
  title    = {{Quantifying the impact of above- and belowground higher trophic levels on plant and herbivore performance by modeling}},
  journal  = {Oikos},
  year     = {2009},
  volume   = {118},
  number   = {7},
  pages    = {981--990},
  issn     = {00301299},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e6d95646194b57c11fca6c1696eb8ec8.pdf/Meyer_et_al_(2009)_OIKOS_impact_of_trophic_levels.pdf},
  abstract = {Growing empirical evidence suggests that aboveground and belowground multitrophic communities interact. However, investigations that comprehensively explore the impacts of above- and belowground third and higher trophic level organisms on plant and herbivore performance are thus far lacking. We tested the hypotheses that above- and belowground higher trophic level organisms as well as decomposers affect plant and herbivore performance and that these effects cross the soilsurface boundary. We used a well-validated simulation model that is individual-based for aboveground trophic levels such as shoot herbivores, parasitoids, and hyperparasitoids while considering belowground herbivores and their antagonists at the population level. We simulated greenhouse experiments by removing trophic levels and decomposers from the simulations in a factorial design. Decomposers and above- and belowground third trophic levels affected plant and herbivore mortality, root biomass, and to a lesser extent shoot biomass. We also tested the effect of gradual modifications of the interactions between different trophic level organisms with a sensitivity analysis. Shoot and root biomass were highly sensitive to the impact of the fourth trophic level. We found effects that cross the soil surface, such as aboveground herbivores and parasitoids affecting root biomass and belowground herbivores influencing aboveground herbivore mortality. We conclude that higher trophic level organisms and decomposers can strongly influence plant and herbivore performance. We propose that our modelling framework can be used in future applications to quantitatively explore the possible outcomes of complex above- and belowground multitrophic interactions under a range of environmental conditions and species compositions.},
  comment  = {public},
  doi      = {10.1111/j.1600-0706.2009.17220.x},
  isbn     = {0030-1299},
}

Growing empirical evidence suggests that aboveground and belowground multitrophic communities interact. However, investigations that comprehensively explore the impacts of above- and belowground third and higher trophic level organisms on plant and herbivore performance are thus far lacking. We tested the hypotheses that above- and belowground higher trophic level organisms as well as decomposers affect plant and herbivore performance and that these effects cross the soilsurface boundary. We used a well-validated simulation model that is individual-based for aboveground trophic levels such as shoot herbivores, parasitoids, and hyperparasitoids while considering belowground herbivores and their antagonists at the population level. We simulated greenhouse experiments by removing trophic levels and decomposers from the simulations in a factorial design. Decomposers and above- and belowground third trophic levels affected plant and herbivore mortality, root biomass, and to a lesser extent shoot biomass. We also tested the effect of gradual modifications of the interactions between different trophic level organisms with a sensitivity analysis. Shoot and root biomass were highly sensitive to the impact of the fourth trophic level. We found effects that cross the soil surface, such as aboveground herbivores and parasitoids affecting root biomass and belowground herbivores influencing aboveground herbivore mortality. We conclude that higher trophic level organisms and decomposers can strongly influence plant and herbivore performance. We propose that our modelling framework can be used in future applications to quantitatively explore the possible outcomes of complex above- and belowground multitrophic interactions under a range of environmental conditions and species compositions.

@Article{Meyer2009b,
  author   = {Meyer, Katrin M. and Wiegand, Kerstin and Ward, David},
  title    = {{Patch dynamics integrate mechanisms for savanna tree-grass coexistence}},
  journal  = {Basic and Applied Ecology},
  year     = {2009},
  volume   = {10},
  number   = {6},
  pages    = {491--499},
  issn     = {14391791},
  url_pdf  = {http://uni-goettingen.de/de/document/download/14eec0483759f65739d75d58276ee225.pdf/Meyer_et_al_(2009)_BAPPLECOL_Patch_dynamics.pdf},
  abstract = {Many mechanisms have been suggested to explain the coexistence of woody species and grasses in savannas. However, evidence from field studies and simulation models has been mixed. Patch dynamics is a potentially unifying mechanism explaining tree-grass coexistence and the natural occurrence of shrub encroachment in arid and semi-arid savannas. A patch-dynamic savanna consists of a spatial mosaic of patches. Each patch maintains a cyclical succession between dominance of woody species and grasses, and the succession of neighbouring patches is temporally asynchronous. Evidence from empirical field studies supports the patch dynamics view of savannas. As a basis for future tests of patch dynamics in savannas, several hypotheses are presented and one is exemplarily examined: at the patch scale, realistically parameterized simulation models have generated cyclical succession between woody and grass dominance. In semi-arid savannas, cyclical successions are driven by precipitation conditions that lead to mass recruitment of shrubs in favourable years and to simultaneous collapse of shrub cohorts in drought years. The spatiotemporal pattern of precipitation events determines the scale of the savanna vegetation mosaic in space and time. In a patch-dynamic savanna, shrub encroachment is a natural, transient phase corresponding to the shrub-dominated phase during the successional cycle. Hence, the most promising management strategy for encroached areas is a large-scale rotation system of rangelands. In conclusion, patch dynamics is a possible scale-explicit mechanism for the explanation of tree-grass coexistence in savannas that integrates most of the coexistence mechanisms proposed thus far for savannas. {\textcopyright} 2009 Gesellschaft f{\"{u}}r {\"{O}}kologie.},
  comment  = {public},
  doi      = {10.1016/j.baae.2008.12.003},
  isbn     = {1439-1791},
  keywords = {Competition,Cyclical succession,Grasses,Mosaic cycles,Shrub encroachment,Shrubs,Simulation models,Spatiotemporal scales,Woody species},
}

Many mechanisms have been suggested to explain the coexistence of woody species and grasses in savannas. However, evidence from field studies and simulation models has been mixed. Patch dynamics is a potentially unifying mechanism explaining tree-grass coexistence and the natural occurrence of shrub encroachment in arid and semi-arid savannas. A patch-dynamic savanna consists of a spatial mosaic of patches. Each patch maintains a cyclical succession between dominance of woody species and grasses, and the succession of neighbouring patches is temporally asynchronous. Evidence from empirical field studies supports the patch dynamics view of savannas. As a basis for future tests of patch dynamics in savannas, several hypotheses are presented and one is exemplarily examined: at the patch scale, realistically parameterized simulation models have generated cyclical succession between woody and grass dominance. In semi-arid savannas, cyclical successions are driven by precipitation conditions that lead to mass recruitment of shrubs in favourable years and to simultaneous collapse of shrub cohorts in drought years. The spatiotemporal pattern of precipitation events determines the scale of the savanna vegetation mosaic in space and time. In a patch-dynamic savanna, shrub encroachment is a natural, transient phase corresponding to the shrub-dominated phase during the successional cycle. Hence, the most promising management strategy for encroached areas is a large-scale rotation system of rangelands. In conclusion, patch dynamics is a possible scale-explicit mechanism for the explanation of tree-grass coexistence in savannas that integrates most of the coexistence mechanisms proposed thus far for savannas. © 2009 Gesellschaft für Ökologie.

@Article{Moustakas2009,
  author   = {Moustakas, Aristides and Sakkos, Konstantinos and Wiegand, Kerstin and Ward, David and Meyer, Katrin M. and Eisinger, Dirk},
  title    = {{Are savannas patch-dynamic systems? A landscape model}},
  journal  = {Ecological Modelling},
  year     = {2009},
  volume   = {220},
  number   = {24},
  pages    = {3576--3588},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/5486ec2bee00f7bcfe8773f99b29cf79.pdf/Moustakas_et_al_(2009)_ECOLMODEL_landscape_model.pdf},
  abstract = {Savannas are ecosystems characterized by the coexistence of woody species (trees and bushes) and grasses. Given that savanna characteristics are mainly formed from competition, herbivory, fire, woodcutting, and patchy soil and precipitation characteristics, we propose a spatially explicit model to examine the effects of the above-mentioned parameters on savanna vegetation dynamics in space and time. Furthermore, we investigate the effects of the above-mentioned parameters on tree-bush-grass ratios, as well as the degrees of aggregation of tree-bush-grass biomass. We parameterized our model for an arid savanna with shallow soil depth as well as a mesic one with generally deeper and more variable soil depths. Our model was able to reproduce savanna vegetation characteristics for periods of time over 2000 years with daily updated time steps. According to our results, tree biomass was higher than bush biomass in the arid savanna but bush biomass exceeded tree and grass biomass in the simulated mesic savanna. Woody biomass increased in our simulations when the soil's porosity values were increased (mesic savanna), in combination with higher precipitation. Savanna vegetation varied from open savanna to woodland and back to open savanna again. Vegetation cycles varied over ∼300-year cycles in the arid and ∼220-year cycles in the mesic-simulated savanna. Autocorrelation values indicated that there are both temporal and spatial vegetation cycles. Our model indicated cycling savanna vegetation at the landscape scale, cycles in cells, and patchiness, i.e. patch dynamics. {\textcopyright} 2009 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2009.06.036},
  isbn     = {0304-3800},
  keywords = {Arid,Bush,Cyclical transition,Grass,Mesic,Shrub invasion,Soil moisture,Spatial autocorrelation,Spatially explicit,Tree,Vegetation cycles},
}

Savannas are ecosystems characterized by the coexistence of woody species (trees and bushes) and grasses. Given that savanna characteristics are mainly formed from competition, herbivory, fire, woodcutting, and patchy soil and precipitation characteristics, we propose a spatially explicit model to examine the effects of the above-mentioned parameters on savanna vegetation dynamics in space and time. Furthermore, we investigate the effects of the above-mentioned parameters on tree-bush-grass ratios, as well as the degrees of aggregation of tree-bush-grass biomass. We parameterized our model for an arid savanna with shallow soil depth as well as a mesic one with generally deeper and more variable soil depths. Our model was able to reproduce savanna vegetation characteristics for periods of time over 2000 years with daily updated time steps. According to our results, tree biomass was higher than bush biomass in the arid savanna but bush biomass exceeded tree and grass biomass in the simulated mesic savanna. Woody biomass increased in our simulations when the soil's porosity values were increased (mesic savanna), in combination with higher precipitation. Savanna vegetation varied from open savanna to woodland and back to open savanna again. Vegetation cycles varied over ∼300-year cycles in the arid and ∼220-year cycles in the mesic-simulated savanna. Autocorrelation values indicated that there are both temporal and spatial vegetation cycles. Our model indicated cycling savanna vegetation at the landscape scale, cycles in cells, and patchiness, i.e. patch dynamics. © 2009 Elsevier B.V. All rights reserved.

@Article{Nothdurft2009,
  author   = {Nothdurft, A. and Borchers, J. and Niggemeyer, P. and Saborowksi, J. and K{\"{a}}ndler, G.},
  title    = {{Eine Folgeaufnahme einer Betriebsinventur als zweiphasige Stichprobe zur Stratifizierung}},
  journal  = {Allgemeine Forst- und Jagdzeitung},
  year     = {2009},
  volume   = {180},
  number   = {7-8},
  pages    = {133--140},
  issn     = {00025852},
  url_pdf  = {http://uni-goettingen.de/de/document/download/cb5ab92921929c257ed34509aceba3fd.pdf/Nothdurft_et_al_(2009)_AFJZ_Folgeaufnahme_einer_Betriebsinventur.pdf},
  comment  = {public},
  keywords = {Double sampling for stratification,Forest inventory,Optimised sampling scheme},
}

@InProceedings{Nothdurft2009a,
  author    = {Nothdurft, Arne and Hradetzky, J. and Sch{\"{o}}pfer, W. and Saborowski, Joachim and Nuske, Robert S.},
  booktitle = {Deutscher Verband Forstlicher Forschungsanstalten, Sektion Forstliche Biometrie und Informatik - 20. Tagung},
  title     = {{Dichtesch{\"{a}}tzung f{\"{u}}r N-Baum-Stichproben durch Reproduktion von Baumartenverteilungsmustern}},
  year      = {2009},
  pages     = {117--121},
  comment   = {public},
  groups    = {Jana:1},
}

@Article{Nothdurft2009b,
  author   = {Nothdurft, Arne and Saborowski, Joachim and Breidenbach, Johannes},
  title    = {{Spatial prediction of forest stand variables}},
  journal  = {European Journal of Forest Research},
  year     = {2009},
  volume   = {128},
  number   = {3},
  pages    = {241--251},
  issn     = {16124669},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d0dfc32d320cac011fd26aadb48172cc.pdf/Nothdurft_et_al_(2009)_EURJFORRES_spatial_prediction_of_forest_stand_variables.pdf},
  abstract = {This study aims at the development of a model to predict forest stand variables in management units (stands) from sample plot inventory data. For this purpose we apply a non-parametric most similar neighbour (MSN) approach. The study area is the municipal forest of Waldkirch, 13 km north-east of Freiburg, Germany, which comprises 328 forest stands and 834 sample plots. Low- resolution laser scanning data, classification variables as well rough estimations from the forest management plan- ning serve as auxiliary variables. In order to avoid common problems of k-NN-approaches caused by asymmetry at the boundaries of the regression spaces and distorted distri- butions, forest stands are tessellated into subunits with an area approximately equivalent to an inventory sample plot. For each subunit only the one nearest neighbour is con- sulted. Predictions for target variables in stands are obtained by averaging the predictions for all subunits. After formulating a random parameter model with variance components, we calibrate the prior predictions by means of sample plot data within the forest stands via BLUPs (best linear unbiased predictors). Based on bootstrap simula- tions, prediction errors for most management units finally prove to be smaller than the design-based sampling error of the mean. The calibration approach shows superiority compared with pure non-parametric MSN predictions.},
  comment  = {public},
  doi      = {10.1007/s10342-009-0260-z},
  keywords = {BLUP,Calibration method,Forest inventory,Imputation,Laser data,Lidar,k-NN},
}

This study aims at the development of a model to predict forest stand variables in management units (stands) from sample plot inventory data. For this purpose we apply a non-parametric most similar neighbour (MSN) approach. The study area is the municipal forest of Waldkirch, 13 km north-east of Freiburg, Germany, which comprises 328 forest stands and 834 sample plots. Low- resolution laser scanning data, classification variables as well rough estimations from the forest management plan- ning serve as auxiliary variables. In order to avoid common problems of k-NN-approaches caused by asymmetry at the boundaries of the regression spaces and distorted distri- butions, forest stands are tessellated into subunits with an area approximately equivalent to an inventory sample plot. For each subunit only the one nearest neighbour is con- sulted. Predictions for target variables in stands are obtained by averaging the predictions for all subunits. After formulating a random parameter model with variance components, we calibrate the prior predictions by means of sample plot data within the forest stands via BLUPs (best linear unbiased predictors). Based on bootstrap simula- tions, prediction errors for most management units finally prove to be smaller than the design-based sampling error of the mean. The calibration approach shows superiority compared with pure non-parametric MSN predictions.

@Article{Nuske2009,
  author   = {Nuske, Robert S. and Sprauer, Susanne and Saborowski, Joachim},
  title    = {{Adapting the pair-correlation function for analysing the spatial distribution of canopy gaps}},
  journal  = {Forest Ecology and Management},
  year     = {2009},
  volume   = {259},
  number   = {1},
  pages    = {107--116},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/776c4ec7c4eb0deeedcf7e3e31e022ba.pdf/Nuske_et_al_(2009)_FECOLMAN_canopy_gaps.pdf},
  abstract = {Forestry around the world has been experiencing a paradigm shift towards more nature-oriented forest management leading foresters to emulate natural disturbances by their silvicultural treatments. Important characteristics of all disturbances are their size, severity, temporal and spatial distribution. This study focuses on the spatial distribution of gaps in the forest canopy which are typically caused by small-scale, low intensity disturbances. The considerable spatial extent and irregular shape of canopy gaps are obvious obstacles to the application of classical point pattern analysis. The approximation of objects by their centroids does not lead to reasonable results, since the objects are at the same scale as the expected effects. By dividing the study area in grid cells and analysing all cells covered by an object, the size and the shape of the objects is accounted for. Nevertheless, both methods show undesirable effects. Thus we propose a new approach using the boundary polygons of the objects and construct the adapted pair-correlation function from the shortest distances between polygons. The adapted pair-correlation function is presented using simulated data and mapped canopy gaps of a near natural forest reserve. The results of our proposed method are compared to the grid-based approach and the classical point pattern analysis. The presented method provides meaningful results and even reveals the relationship of objects at short distances, which is not possible using the classical point pattern analysis or the grid-based approach. With regard to the analysis of the spatial distribution of canopy gaps, the adapted pair-correlation function proves to be a useful analytical tool. {\textcopyright} 2009 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2009.09.050},
  isbn     = {0378-1127},
  keywords = {Canopy gaps,Disturbances,Pair-correlation function,Point pattern,Spatial statistics},
}

Forestry around the world has been experiencing a paradigm shift towards more nature-oriented forest management leading foresters to emulate natural disturbances by their silvicultural treatments. Important characteristics of all disturbances are their size, severity, temporal and spatial distribution. This study focuses on the spatial distribution of gaps in the forest canopy which are typically caused by small-scale, low intensity disturbances. The considerable spatial extent and irregular shape of canopy gaps are obvious obstacles to the application of classical point pattern analysis. The approximation of objects by their centroids does not lead to reasonable results, since the objects are at the same scale as the expected effects. By dividing the study area in grid cells and analysing all cells covered by an object, the size and the shape of the objects is accounted for. Nevertheless, both methods show undesirable effects. Thus we propose a new approach using the boundary polygons of the objects and construct the adapted pair-correlation function from the shortest distances between polygons. The adapted pair-correlation function is presented using simulated data and mapped canopy gaps of a near natural forest reserve. The results of our proposed method are compared to the grid-based approach and the classical point pattern analysis. The presented method provides meaningful results and even reveals the relationship of objects at short distances, which is not possible using the classical point pattern analysis or the grid-based approach. With regard to the analysis of the spatial distribution of canopy gaps, the adapted pair-correlation function proves to be a useful analytical tool. © 2009 Elsevier B.V. All rights reserved.

@Article{Plasil2009,
  author  = {Pla{\v{s}}il, P. and Ksinsik, M. and Seelig, J. and Lanwert, D. and Saborowski, J. and Sch{\"{u}}tz, S.},
  title   = {{Computer-based online identification programme for forest relevant insects}},
  journal = {Mitteilungen Deutsche Gesellschaft f{\"{u}}r allgemeine und angewandte Entomologie},
  year    = {2009},
  volume  = {17},
  pages   = {167--171},
  url_pdf = {http://uni-goettingen.de/de/document/download/ccc9118428c92d0be6c3321423e4af7c.pdf/Plasil_et_al_(2009)_DGaaEntomol_online_identification_insects.pdf},
  comment = {public},
}

@Article{Rodriguez2009,
  author   = {Rodr{\'{i}}guez, Carlos and Wiegand, Kerstin},
  title    = {{Evaluating the trade-off between machinery efficiency and loss of biodiversity-friendly habitats in arable landscapes: The role of field size}},
  journal  = {Agriculture, Ecosystems and Environment},
  year     = {2009},
  volume   = {129},
  number   = {4},
  pages    = {361--366},
  issn     = {01678809},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a796f4291b62ceeb4b78848d67b20990.pdf/Rodriguez_&_Wiegand_(2008)_AGEE_machinery_biodiversity_tradeoffs.pdf},
  abstract = {Agricultural intensification has occurred in much of Europe since the middle of the 20th century implying profound changes in arable landscapes, and being the main cause of biodiversity erosion in farmed ecosystems. Because current public demands also include non-market goods such as biodiversity, landscape, historic environment, and natural resources, it is necessary to evaluate the trade-off between agriculture production and biodiversity conservation associated to agricultural practices. In this paper we examine one of the most important structural changes in arable landscapes: field enlargement. We evaluate its contribution to increase machinery efficiency, but also the associated erosion of biodiversity-friendly habitats such as field margins. We found a threshold in field size around 1-2 ha above which machinery efficiency increases very little, indicating that there is no need for bigger fields from the production point of view. We suggest to use this threshold as criterion for sowing in-field strips and restoring field margins, which are measures thought to enhance biodiversity in arable landscapes. ?? 2008 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.agee.2008.10.010},
  isbn     = {0167-8809},
  keywords = {Agri-environmental schemes,Agriculture intensification,Field margins,Machinery efficiency},
}

Agricultural intensification has occurred in much of Europe since the middle of the 20th century implying profound changes in arable landscapes, and being the main cause of biodiversity erosion in farmed ecosystems. Because current public demands also include non-market goods such as biodiversity, landscape, historic environment, and natural resources, it is necessary to evaluate the trade-off between agriculture production and biodiversity conservation associated to agricultural practices. In this paper we examine one of the most important structural changes in arable landscapes: field enlargement. We evaluate its contribution to increase machinery efficiency, but also the associated erosion of biodiversity-friendly habitats such as field margins. We found a threshold in field size around 1-2 ha above which machinery efficiency increases very little, indicating that there is no need for bigger fields from the production point of view. We suggest to use this threshold as criterion for sowing in-field strips and restoring field margins, which are measures thought to enhance biodiversity in arable landscapes. ?? 2008 Elsevier B.V. All rights reserved.

@Incollection{Thiele2009,
  author    = {Thiele, J. C. and Nuske, Robert S. and Ahrends, B. and Saborowski, J.},
  title     = {{Entwicklung eines Entscheidungsunterst{\"{u}}tzungssystems f{\"{u}}r die Waldbewirtschaftung unter sich {\"{a}}ndernden Klimabedingungen}},
  booktitle = {Klimaschutz und Anpassung an die Klimafolgen},
  publisher = {Institut der deutschen Wirtschaft K{\"{o}}ln Medien GmbH},
  year      = {2009},
  editor    = {{M. Mahammadzadeh, H. Biebeler}, H. Bardt},
  pages     = {303--310},
  url_pdf   = {http://uni-goettingen.de/de/document/download/79822015613442b8f4de9242556a8162.pdf/Thiele_et_al_(2009)_InstDeuWirtsch_Entscheidungsunterstuetzungsszstem.pdf},
  comment   = {public},
}

@Misc{VanDerPutten2009,
  author    = {{Van Der Putten}, Wim H. and Bardgett, R. D. and {De Ruiter}, P. C. and Hol, W. H.G. and Meyer, K. M. and Bezemer, T. M. and Bradford, M. A. and Christensen, S. and Eppinga, M. B. and Fukami, T. and Hemerik, L. and Molofsky, J. and Sch{\"{a}}dler, M. and Scherber, C. and Strauss, S. Y. and Vos, M. and Wardle, D. A.},
  title     = {{Empirical and theoretical challenges in aboveground-belowground ecology}},
  year      = {2009},
  url_pdf   = {http://uni-goettingen.de/de/document/download/31aa6b1595fdbe3359b2fba8820af745.pdf/van_der_Putten_(2009)_OECOLOGIA_empirical_and_theoretical_challenges.pdf},
  abstract  = {A growing body of evidence shows that aboveground and belowground communities and processes are intrinsically linked, and that feedbacks between these subsystems have important implications for community structure and ecosystem functioning. Almost all studies on this topic have been carried out from an empirical perspective and in specific ecological settings or contexts. Belowground interactions operate at different spatial and temporal scales. Due to the relatively low mobility and high survival of organisms in the soil, plants have longer lasting legacy effects belowground than aboveground. Our current challenge is to understand how aboveground-belowground biotic interactions operate across spatial and temporal scales, and how they depend on, as well as influence, the abiotic environment. Because empirical capacities are too limited to explore all possible combinations of interactions and environmental settings, we explore where and how they can be supported by theoretical approaches to develop testable predictions and to generalise empirical results. We review four key areas where a combined aboveground-belowground approach offers perspectives for enhancing ecological understanding, namely succession, agro-ecosystems, biological invasions and global change impacts on ecosystems. In plant succession, differences in scales between aboveground and belowground biota, as well as between species interactions and ecosystem processes, have important implications for the rate and direction of community change. Aboveground as well as belowground interactions either enhance or reduce rates of plant species replacement. Moreover, the outcomes of the interactions depend on abiotic conditions and plant life history characteristics, which may vary with successional position. We exemplify where translation of the current conceptual succession models into more predictive models can help targeting empirical studies and generalising their results. Then, we discuss how understanding succession may help to enhance managing arable crops, grasslands and invasive plants, as well as provide insights into the effects of global change on community re-organisation and ecosystem processes.},
  booktitle = {Oecologia},
  comment   = {public},
  doi       = {10.1007/s00442-009-1351-8},
  isbn      = {1432-1939 (Electronic)$\backslash$r0029-8549 (Linking)},
  issn      = {00298549},
  keywords  = {Global change,Invasion,Succession,Sustainable crop protection,Temporal and spatial models},
  number    = {1},
  pages     = {1--14},
  pmid      = {19412705},
  volume    = {161},
}

A growing body of evidence shows that aboveground and belowground communities and processes are intrinsically linked, and that feedbacks between these subsystems have important implications for community structure and ecosystem functioning. Almost all studies on this topic have been carried out from an empirical perspective and in specific ecological settings or contexts. Belowground interactions operate at different spatial and temporal scales. Due to the relatively low mobility and high survival of organisms in the soil, plants have longer lasting legacy effects belowground than aboveground. Our current challenge is to understand how aboveground-belowground biotic interactions operate across spatial and temporal scales, and how they depend on, as well as influence, the abiotic environment. Because empirical capacities are too limited to explore all possible combinations of interactions and environmental settings, we explore where and how they can be supported by theoretical approaches to develop testable predictions and to generalise empirical results. We review four key areas where a combined aboveground-belowground approach offers perspectives for enhancing ecological understanding, namely succession, agro-ecosystems, biological invasions and global change impacts on ecosystems. In plant succession, differences in scales between aboveground and belowground biota, as well as between species interactions and ecosystem processes, have important implications for the rate and direction of community change. Aboveground as well as belowground interactions either enhance or reduce rates of plant species replacement. Moreover, the outcomes of the interactions depend on abiotic conditions and plant life history characteristics, which may vary with successional position. We exemplify where translation of the current conceptual succession models into more predictive models can help targeting empirical studies and generalising their results. Then, we discuss how understanding succession may help to enhance managing arable crops, grasslands and invasive plants, as well as provide insights into the effects of global change on community re-organisation and ecosystem processes.

@Article{Visser2009,
  author   = {Visser, Ute and Wiegand, Kerstin and Grimm, Volker and Johst, Karin},
  title    = {{Conservation Biocontrol in Fragmented Landscapes: Persistence and Parasitation in a Host-Parasitoid Model}},
  journal  = {The Open Ecology Journal},
  year     = {2009},
  volume   = {2},
  number   = {1},
  pages    = {52--61},
  issn     = {18742130},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2f886a1df1ad93ec691f2f4e21c3aac8.pdf/Visser_et_al_(2009)_OPEN_ECOL_J_ConservationBiocontrol.pdf},
  abstract = {In the context of agricultural landscapes, conservation biocontrol practitioners attempt to secure and enhance the presence and effectiveness of natural enemies of insect pest species, for example parasitoids. Conservation biocontrol aims at maximizing both parasitoid persistence and parasitation rate. It is, however, still poorly understood how the amount, fragmentation and isolation of non-crop habitat of the host and its parasitoid affect persistence and parasitation rate. We developed a spatially explicit simulation model of a host and its specialized parasitoid and simulated thei3 spatiotemporal population dynamics in virtual landscapes. We found that the total habitat amount in the landscape modulates the impact of fragmentation on parasitoid persistence. If habitat is abundant, parasitoid persistence decreases with fragmentation, whereas if habitat is scarce, persistence is highest at intermediate levels of fragmentation. In any case, persistence is best for intermediate levels of isolation. Parasitation rate, on the other hand, is negatively influenced by fragmentation and isolation regardless of the habitat amount. Our results suggest that in landscapes with abundant habitat, both parasitation rates and parasitoid persistence can be increased by arranging habitat to be as clumped as possible. However, if habitat is scarce, landscape management can optimize either parasitation rates or parasitoid persistence but not both simultaneously.},
  comment  = {public},
  doi      = {10.2174/1874213000902010052},
  keywords = {agricultural landscape,conservation biological control,fragmentation,habitat isolation,heterogeneous landscape,insect pest species,landscape management,parasitation rate,parasitoid persistence,parasitoids},
}

In the context of agricultural landscapes, conservation biocontrol practitioners attempt to secure and enhance the presence and effectiveness of natural enemies of insect pest species, for example parasitoids. Conservation biocontrol aims at maximizing both parasitoid persistence and parasitation rate. It is, however, still poorly understood how the amount, fragmentation and isolation of non-crop habitat of the host and its parasitoid affect persistence and parasitation rate. We developed a spatially explicit simulation model of a host and its specialized parasitoid and simulated thei3 spatiotemporal population dynamics in virtual landscapes. We found that the total habitat amount in the landscape modulates the impact of fragmentation on parasitoid persistence. If habitat is abundant, parasitoid persistence decreases with fragmentation, whereas if habitat is scarce, persistence is highest at intermediate levels of fragmentation. In any case, persistence is best for intermediate levels of isolation. Parasitation rate, on the other hand, is negatively influenced by fragmentation and isolation regardless of the habitat amount. Our results suggest that in landscapes with abundant habitat, both parasitation rates and parasitoid persistence can be increased by arranging habitat to be as clumped as possible. However, if habitat is scarce, landscape management can optimize either parasitation rates or parasitoid persistence but not both simultaneously.

@Article{Eisinger2008,
  author   = {Eisinger, Dirk and Wiegand, Kerstin},
  title    = {{SERGE: A spatially explicit generator of local rainfall in southern Africa}},
  journal  = {South African Journal of Science},
  year     = {2008},
  volume   = {104},
  number   = {1-2},
  pages    = {37--42},
  issn     = {00382353},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2cfd2c87ea37db8cf499754967318c2e.pdf/Eisinger_&_Wiegand_(2008)_S_AFR_J_SCI_SERGE.pdf},
  abstract = {This article describes the features of SERGE, a stochastic, spatially explicit tool for the simulation of daily rainfall in arid environ- ments. Rainfall data (either raw or produced by a rainfall generator) are frequently available on a daily basis but at low spatial resolu- tion. Furthermore, although the rainfall characteristics of a given small area may vary little when averaged over the long term, rainfall does vary substantially on a daily time scale. It is exactly this short-term, small-scale variation that is of interest to modellers in many applications. A tool is needed therefore that generates spatio-temporal rainfall estimates based on only temporal data. To fill this gap, we developed SERGE using an ad hoc approach. Based on known characteristics of rainfall at a point, SERGE projects spatially homogeneous daily rainfall produced by a rainfall generator into spatially heterogeneous estimates by distributing clouds of fixed size and random position. Our algorithm preserves the long- term rainfall characteristics at each point, but introduces spatial autocorrelation of variable length. SERGE provides a simple and flexible tool for the simulation of spatio-temporal rainfall to be integrated into other models. SERGE is intended for modellers wanting to investigate the effect of spatially variable rainfall in their system. Given the importance of spatial variability in arid environments, this should be of interest to scientists in the fields of ecology, range management, agriculture, climate change, and hydrology.},
  comment  = {public},
}

This article describes the features of SERGE, a stochastic, spatially explicit tool for the simulation of daily rainfall in arid environ- ments. Rainfall data (either raw or produced by a rainfall generator) are frequently available on a daily basis but at low spatial resolu- tion. Furthermore, although the rainfall characteristics of a given small area may vary little when averaged over the long term, rainfall does vary substantially on a daily time scale. It is exactly this short-term, small-scale variation that is of interest to modellers in many applications. A tool is needed therefore that generates spatio-temporal rainfall estimates based on only temporal data. To fill this gap, we developed SERGE using an ad hoc approach. Based on known characteristics of rainfall at a point, SERGE projects spatially homogeneous daily rainfall produced by a rainfall generator into spatially heterogeneous estimates by distributing clouds of fixed size and random position. Our algorithm preserves the long- term rainfall characteristics at each point, but introduces spatial autocorrelation of variable length. SERGE provides a simple and flexible tool for the simulation of spatio-temporal rainfall to be integrated into other models. SERGE is intended for modellers wanting to investigate the effect of spatially variable rainfall in their system. Given the importance of spatial variability in arid environments, this should be of interest to scientists in the fields of ecology, range management, agriculture, climate change, and hydrology.

@Article{Getzin2008,
  author   = {Getzin, Stephan and Wiegand, Kerstin and Schumacher, Jens and Gougeon, Fran{\c{c}}ois A.},
  title    = {{Scale-dependent competition at the stand level assessed from crown areas}},
  journal  = {Forest Ecology and Management},
  year     = {2008},
  volume   = {255},
  number   = {7},
  pages    = {2478--2485},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/c2f1a8a3c77e4da0227f5c1596c29c11.PDF/Getzin_et_al_(2008)_FOREST_ECOC_MANAG_Scale-dependent_competition.PDF},
  abstract = {The detection and quantification of competition at the stand level is important in forest management because competition reduces growth and increases the risk of mortality. This is of interest for timber production where efficient tools of forest inventory are increasingly demanded. Especially modern planning of thinning based on aerial or satellite images requires a deeper and spatially explicit understanding of the growth dynamics of tree crowns relative to the dynamics of stems. Past studies have evaluated competition in forests with scale-dependent correlation functions applied to tree-size attributes (continuous marks) such as diameter at breast height (DBH) or tree height. Despite the fast reaction of foliage to changes of neighborhood density in the canopy, horizontal crown extent has apparently not been used in such competition analyses of marked point patterns. Here we investigated in a spatially explicit approach the formation of crown-size patterns under neighborhood competition. We also compared how mutual growth reduction in reaction to competition differs between crown extent and stem diameters. This response of tree-size attributes to competition was analyzed with the scale-dependent mark-correlation function (MCF) applied to the marks 'DBH', 'crown area' of all live trees, and 'upper crown area' of overstory trees. These analyses were conducted for two deciduous and two coniferous forests in central Germany. Unlike stem diameters, crown areas were very sensitive for the detection of competition in stands. In relation to 'crown area' of all trees in a plot, this sensitivity was greater when only the mark 'upper crown area' of overstory trees was analyzed because both the strength and the spatial range of negative size correlation increased. Upper crown areas showed a finite range of negative interaction of about 6 m. These results demonstrate that (1) the 'functional growing space' of large and light-exposed canopy trees is highly suitable to detect competition and (2) the spatial range and strength of competition can be assessed and differentiated between stands in a spatially explicit manner. Our application may have practical value for monitoring competition based on remotely sensed forest inventory because upper crown areas as seen by the 'bird-eye's view' were most sensitive for detecting competition in stands. {\textcopyright} 2008 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2008.01.007},
  isbn     = {0378-1127},
  keywords = {Competition,Crown area,Douglas-fir,Mark-correlation function,Remote sensing,Spatial scale},
}

The detection and quantification of competition at the stand level is important in forest management because competition reduces growth and increases the risk of mortality. This is of interest for timber production where efficient tools of forest inventory are increasingly demanded. Especially modern planning of thinning based on aerial or satellite images requires a deeper and spatially explicit understanding of the growth dynamics of tree crowns relative to the dynamics of stems. Past studies have evaluated competition in forests with scale-dependent correlation functions applied to tree-size attributes (continuous marks) such as diameter at breast height (DBH) or tree height. Despite the fast reaction of foliage to changes of neighborhood density in the canopy, horizontal crown extent has apparently not been used in such competition analyses of marked point patterns. Here we investigated in a spatially explicit approach the formation of crown-size patterns under neighborhood competition. We also compared how mutual growth reduction in reaction to competition differs between crown extent and stem diameters. This response of tree-size attributes to competition was analyzed with the scale-dependent mark-correlation function (MCF) applied to the marks 'DBH', 'crown area' of all live trees, and 'upper crown area' of overstory trees. These analyses were conducted for two deciduous and two coniferous forests in central Germany. Unlike stem diameters, crown areas were very sensitive for the detection of competition in stands. In relation to 'crown area' of all trees in a plot, this sensitivity was greater when only the mark 'upper crown area' of overstory trees was analyzed because both the strength and the spatial range of negative size correlation increased. Upper crown areas showed a finite range of negative interaction of about 6 m. These results demonstrate that (1) the 'functional growing space' of large and light-exposed canopy trees is highly suitable to detect competition and (2) the spatial range and strength of competition can be assessed and differentiated between stands in a spatially explicit manner. Our application may have practical value for monitoring competition based on remotely sensed forest inventory because upper crown areas as seen by the 'bird-eye's view' were most sensitive for detecting competition in stands. © 2008 Elsevier B.V. All rights reserved.

@Article{Getzin2008a,
  author   = {Getzin, Stephan and Wiegand, Thorsten and Wiegand, Kerstin and He, Fangliang},
  title    = {{Heterogeneity influences spatial patterns and demographics in forest stands}},
  journal  = {Journal of Ecology},
  year     = {2008},
  volume   = {96},
  number   = {4},
  pages    = {807--820},
  issn     = {00220477},
  url_pdf  = {http://uni-goettingen.de/de/document/download/6797c8775913320b9f09fb063e5913b0.pdf/Getzin_et_al_(2008)_JECOL_spatial_patterns_in_forest_stands.pdf},
  abstract = {1. The spatial pattern of tree species retains signatures of factors and processes such as dispersal, available resource patches for establishment, competition and demographics. Comparison of the spatial pattern of different size classes can thus help to reveal the importance and characteristics of the underlying processes. However, tree dynamics may be masked by large-scale heterogeneous site conditions, e.g. when the restricting size of regeneration sites superimposes emergent patterns. $\backslash$n$\backslash$n2. Here we ask how environmental heterogeneity may influence the spatial dynamics of plant communities. We compared the spatial patterns and demographics of western hemlock in a homogeneous and a heterogeneous site of old-growth Douglas-fir forests on Vancouver Island using recent techniques of point pattern analysis. We used homogeneous and inhomogeneous K- and pair-correlation functions, and case-control studies to quantify the change in spatial distribution for different size classes of western hemlock. $\backslash$n$\backslash$n3. Our comparative analyses show that biological processes interacted with spatial heterogeneity, leading to qualitatively different population dynamics at the two sites. Population structure, survival and size structure of western hemlock were different in the heterogeneous stand in such a way that, compared to the homogeneous stand, seedlings were more clustered, seedling densities higher, seedling mortality lower, adult growth faster and adult mortality higher. Under homogeneous site conditions, seedling survival was mainly abiotically determined by random arrival in small gaps with limiting light. At the heterogeneous site, seedling densities and initial survival were much higher, leading to strong density-dependent mortality and selection for faster growing individuals in larger size classes. We hypothesise that the dynamics of the heterogeneous stand were faster due to asymmetric competition with disproportionate benefit to taller plants. $\backslash$n$\backslash$n4. Synthesis. Our study supports the hypothesis that successional dynamics are intensified in heterogeneous forest stands with strong spatial structures and outlines the importance of spatial heterogeneity as a determinant of plant population dynamics and pattern formation.},
  comment  = {public},
  doi      = {10.1111/j.1365-2745.2008.01377.x},
  isbn     = {0022-0477},
  keywords = {Case-control,Dispersal strategies,Inhomogeneous pair-correlation function,Large-scale heterogeneity,Point pattern analysis,Succession,Western hemlock},
  pmid     = {18784797},
}

1. The spatial pattern of tree species retains signatures of factors and processes such as dispersal, available resource patches for establishment, competition and demographics. Comparison of the spatial pattern of different size classes can thus help to reveal the importance and characteristics of the underlying processes. However, tree dynamics may be masked by large-scale heterogeneous site conditions, e.g. when the restricting size of regeneration sites superimposes emergent patterns. $\$n$\$n2. Here we ask how environmental heterogeneity may influence the spatial dynamics of plant communities. We compared the spatial patterns and demographics of western hemlock in a homogeneous and a heterogeneous site of old-growth Douglas-fir forests on Vancouver Island using recent techniques of point pattern analysis. We used homogeneous and inhomogeneous K- and pair-correlation functions, and case-control studies to quantify the change in spatial distribution for different size classes of western hemlock. $\$n$\$n3. Our comparative analyses show that biological processes interacted with spatial heterogeneity, leading to qualitatively different population dynamics at the two sites. Population structure, survival and size structure of western hemlock were different in the heterogeneous stand in such a way that, compared to the homogeneous stand, seedlings were more clustered, seedling densities higher, seedling mortality lower, adult growth faster and adult mortality higher. Under homogeneous site conditions, seedling survival was mainly abiotically determined by random arrival in small gaps with limiting light. At the heterogeneous site, seedling densities and initial survival were much higher, leading to strong density-dependent mortality and selection for faster growing individuals in larger size classes. We hypothesise that the dynamics of the heterogeneous stand were faster due to asymmetric competition with disproportionate benefit to taller plants. $\$n$\$n4. Synthesis. Our study supports the hypothesis that successional dynamics are intensified in heterogeneous forest stands with strong spatial structures and outlines the importance of spatial heterogeneity as a determinant of plant population dynamics and pattern formation.

@Article{Meyer2008,
  author   = {Meyer, Katrin M. and Ward, David and Wiegand, Kerstin and Moustakas, Aristides},
  title    = {{Multi-proxy evidence for competition between savanna woody species}},
  journal  = {Perspectives in Plant Ecology, Evolution and Systematics},
  year     = {2008},
  volume   = {10},
  number   = {1},
  pages    = {63--72},
  issn     = {16180437},
  url_pdf  = {http://uni-goettingen.de/de/document/download/625fc241a57b84efd9425c4e80049b23.PDF/Meyer_et_al_(2008)_PERSP_ECOL_EVOL_SYSTEM_Multi-proxy_evidence.PDF},
  abstract = {Coexistence of trees and grasses in savannas should be possible if competition between the woody and the grassy components is less intense than the competition within each component. Although several studies have investigated competition between trees and grasses, little is known about tree-tree interactions. We used a multi-proxy approach to examine the spatial pattern of Acacia mellifera and other savanna woody species in a semi-arid savanna in South Africa. Spatial analysis of the point patterns of young and reproductively mature shrubs detected decreasing aggregation with size/age over all spatial scales. This indicated the prevalence of competition although the overall spatial shrub pattern was aggregated. In contrast to point pattern statistics that detect changes only when competition has led to the death of the inferior competitor, we also applied methods identifying the competitive effect on sizes of individual trees. Competition should lead to a negative spatial autocorrelation in size, which we observed in half of the studied cases. Quantile regressions show that nearest-neighbour distance increased steeply with combined size of the target shrub and its neighbours indicating strong competitive effects. The medians of the distributions of maximum root lengths of A. mellifera, of the scale of regular patterns, and of negative autocorrelations were not significantly different, suggesting that overlapping root systems mediate competitive interactions. A competitor removal experiment did not lead to increased shrub sizes, which may be due to the limited duration of the experiment. From the nearest neighbour and autocorrelation analyses, we conclude that competition had a strong impact on growth rates of savanna woody species. Competition-induced mortality only becomes obvious when analysing the shift towards less aggregated spatial patterns when shrubs become reproductively mature. As the overall clustered spatial pattern masks the perceptible effect of competition, a time component should always be included in spatial pattern-based inference of competition. {\textcopyright} 2007 R{\"{u}}bel Foundation, ETH Z{\"{u}}rich.},
  comment  = {public},
  doi      = {10.1016/j.ppees.2007.09.002},
  isbn     = {1433-8319},
  keywords = {Acacia mellifera,Competitor removal experiment,Nearest-neighbour distance,Quantile regression,Spatial autocorrelation,Spatial point pattern analysis},
}

Coexistence of trees and grasses in savannas should be possible if competition between the woody and the grassy components is less intense than the competition within each component. Although several studies have investigated competition between trees and grasses, little is known about tree-tree interactions. We used a multi-proxy approach to examine the spatial pattern of Acacia mellifera and other savanna woody species in a semi-arid savanna in South Africa. Spatial analysis of the point patterns of young and reproductively mature shrubs detected decreasing aggregation with size/age over all spatial scales. This indicated the prevalence of competition although the overall spatial shrub pattern was aggregated. In contrast to point pattern statistics that detect changes only when competition has led to the death of the inferior competitor, we also applied methods identifying the competitive effect on sizes of individual trees. Competition should lead to a negative spatial autocorrelation in size, which we observed in half of the studied cases. Quantile regressions show that nearest-neighbour distance increased steeply with combined size of the target shrub and its neighbours indicating strong competitive effects. The medians of the distributions of maximum root lengths of A. mellifera, of the scale of regular patterns, and of negative autocorrelations were not significantly different, suggesting that overlapping root systems mediate competitive interactions. A competitor removal experiment did not lead to increased shrub sizes, which may be due to the limited duration of the experiment. From the nearest neighbour and autocorrelation analyses, we conclude that competition had a strong impact on growth rates of savanna woody species. Competition-induced mortality only becomes obvious when analysing the shift towards less aggregated spatial patterns when shrubs become reproductively mature. As the overall clustered spatial pattern masks the perceptible effect of competition, a time component should always be included in spatial pattern-based inference of competition. © 2007 Rübel Foundation, ETH Zürich.

@Article{Meyer2008a,
  author   = {Meyer, Katrin M. and Wiegand, Kerstin and Ward, David and Moustakas, Aristides},
  title    = {{Determining patch size}},
  journal  = {African Journal of Ecology},
  year     = {2008},
  volume   = {46},
  number   = {3},
  pages    = {440--442},
  issn     = {01416707},
  url_pdf  = {http://uni-goettingen.de/de/document/download/2e44e1150238055bc16fe9866be2c6c1.pdf/Meyer_et_al_(2007)_AfrJEcol_determining_patch_size.pdf},
  abstract = {Shrub encroachment, i.e. the increase in density of woody species, is threatening tree-grass coexistence in savannas worldwide (see e.g. Smit, 2004; Wiegand, Ward {\&} Saltz, 2005; Wiegand, Saltz {\&} Ward, 2006). In addition to ecological problems, shrub encroachment creates economic problems, because it reduces the extent of areas suitable for grazing of livestock. In recognition of the importance of spatial and temporal scales for savannas, Wiegand et al. (2005, 2006) proposed patch-dynamics as the driving mechanism of tree-grass coexistence in savannas including a naturally shrub encroached phase. In patch-dynamic landscapes, patches are asynchronously cycling between woody and grassy dominance. Evidence for patch-dynamic savannas is accumulating (e.g. Gillson, 2004; Wiegand et al., 2006), but simple methods for the determination of the spatial scale of patches are still lacking. In the present study, we propose a method for estimating patch sizes based on the canopy diameter and the spatial location of individuals and apply it to an example data set from a semi-arid savanna in South Africa.},
  comment  = {public},
  doi      = {10.1111/j.1365-2028.2007.00834.x},
  isbn     = {0141-6707},
}

Shrub encroachment, i.e. the increase in density of woody species, is threatening tree-grass coexistence in savannas worldwide (see e.g. Smit, 2004; Wiegand, Ward & Saltz, 2005; Wiegand, Saltz & Ward, 2006). In addition to ecological problems, shrub encroachment creates economic problems, because it reduces the extent of areas suitable for grazing of livestock. In recognition of the importance of spatial and temporal scales for savannas, Wiegand et al. (2005, 2006) proposed patch-dynamics as the driving mechanism of tree-grass coexistence in savannas including a naturally shrub encroached phase. In patch-dynamic landscapes, patches are asynchronously cycling between woody and grassy dominance. Evidence for patch-dynamic savannas is accumulating (e.g. Gillson, 2004; Wiegand et al., 2006), but simple methods for the determination of the spatial scale of patches are still lacking. In the present study, we propose a method for estimating patch sizes based on the canopy diameter and the spatial location of individuals and apply it to an example data set from a semi-arid savanna in South Africa.

@Article{Moustakas2008,
  author   = {Moustakas, Aristides and Wiegand, Kerstin and Getzin, Stephan and Ward, David and Meyer, Katrin M. and Guenther, Matthias and Mueller, Karl Heinz},
  title    = {{Spacing patterns of an Acacia tree in the Kalahari over a 61-year period: How clumped becomes regular and vice versa}},
  journal  = {Acta Oecologica},
  year     = {2008},
  volume   = {33},
  number   = {3},
  pages    = {355--364},
  issn     = {1146609X},
  url_pdf  = {http://uni-goettingen.de/de/document/download/9024bb91a09195582b52c334ef55a1d2.PDF/Moustakas_et_al_(2008)_ACTA_OECOL_Spacing_patterns_Acacia%20tree.PDF},
  abstract = {Nearest tree neighbour distances and the tree spatial formation on a large scale over time and space replicates were examined. The study was conducted in a natural savanna ecosystem in the Southern Kalahari, South Africa. Nearest tree neighbour and point pattern analysis methods were used to investigate changes in the spatial pattern of trees in two plots. Trees larger than 2 m canopy diameter were mapped. We used aerial photographs of the study area from 1940, 1964, 1984, 1993, and a satellite image from 2001 to follow two plots over time. Field work was carried out too for classification accuracy. We were able to identify and individually follow over 2400 individual trees from 1940 until 2001. Nearest neighbour analysis results indicate that dead trees were on average closer to their nearest neighbouring trees than living trees were to their neighbours. Most dead trees were on average 6 m from their nearest neighbours, while most living trees were about 20 m apart. Point pattern analysis results show a cyclical transition from clumped to random and sequentially to regular tree spacing. These transitions were not correlated across two plots. Generally, decreases in small-scale clumping coincided with periods of high mortality. Our findings show that regular, clumped, and random tree pattern can occur, pending on time, location, and scale within the location. {\textcopyright} 2008 Elsevier Masson SAS. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.actao.2008.01.008},
  isbn     = {1146-609X},
  keywords = {Acacia erioloba,Long-term study,Nearest neighbour analysis,Point pattern analysis,Savanna,Spatial patterns,Tree mortality,Tree size,Tree-tree competition},
}

Nearest tree neighbour distances and the tree spatial formation on a large scale over time and space replicates were examined. The study was conducted in a natural savanna ecosystem in the Southern Kalahari, South Africa. Nearest tree neighbour and point pattern analysis methods were used to investigate changes in the spatial pattern of trees in two plots. Trees larger than 2 m canopy diameter were mapped. We used aerial photographs of the study area from 1940, 1964, 1984, 1993, and a satellite image from 2001 to follow two plots over time. Field work was carried out too for classification accuracy. We were able to identify and individually follow over 2400 individual trees from 1940 until 2001. Nearest neighbour analysis results indicate that dead trees were on average closer to their nearest neighbouring trees than living trees were to their neighbours. Most dead trees were on average 6 m from their nearest neighbours, while most living trees were about 20 m apart. Point pattern analysis results show a cyclical transition from clumped to random and sequentially to regular tree spacing. These transitions were not correlated across two plots. Generally, decreases in small-scale clumping coincided with periods of high mortality. Our findings show that regular, clumped, and random tree pattern can occur, pending on time, location, and scale within the location. © 2008 Elsevier Masson SAS. All rights reserved.

@Article{Rodriguez2008,
  author   = {Rodr{\'{i}}guez, Carlos and Johst, Karin and Bustamante, Javier},
  title    = {{Parental versus offspring control on food division within the brood: The role of hatching asynchrony}},
  journal  = {Oikos},
  year     = {2008},
  volume   = {117},
  number   = {5},
  pages    = {719--728},
  issn     = {00301299},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a1a4ef53e57bb2e05e247298c439dd85.pdf/Rodrigue_et_al_(2008)_OIKOS_parental_vs_offspring_control.pdf},
  abstract = {Using an individual-based simulation model we study how different mechanisms of food division among multiple offspring influence nestling number and quality, as well as parental effort. We consider the combination of different scenarios of food availability (feeding conditions), hatching asynchrony and food division. If parents have full control on how to divide food among offspring, asynchronous broods have higher breeding performance than synchronous ones in a wide range of feeding conditions, giving theoretical support to empirically proved benefits of hatching asynchrony. If parents accept the outcome of sibling competition there is a threshold in feeding conditions below which asynchronous broods produced more fledglings and the reverse was true above the threshold. Interestingly, parents relying on the outcome of nestling competition do not necessarily differ in breeding performance from those which have full control over food allocation. Our study combines hatching asynchrony, provisioning behaviour of parents, jostling behaviour of nestlings and feeding conditions as a network of interacting processes of enormous interest to fully understand the parent-offspring conflict.},
  comment  = {public},
  doi      = {10.1111/j.0030-1299.2008.16404.x},
  isbn     = {0030-1299},
}

Using an individual-based simulation model we study how different mechanisms of food division among multiple offspring influence nestling number and quality, as well as parental effort. We consider the combination of different scenarios of food availability (feeding conditions), hatching asynchrony and food division. If parents have full control on how to divide food among offspring, asynchronous broods have higher breeding performance than synchronous ones in a wide range of feeding conditions, giving theoretical support to empirically proved benefits of hatching asynchrony. If parents accept the outcome of sibling competition there is a threshold in feeding conditions below which asynchronous broods produced more fledglings and the reverse was true above the threshold. Interestingly, parents relying on the outcome of nestling competition do not necessarily differ in breeding performance from those which have full control over food allocation. Our study combines hatching asynchrony, provisioning behaviour of parents, jostling behaviour of nestlings and feeding conditions as a network of interacting processes of enormous interest to fully understand the parent-offspring conflict.

@Article{Wiegand2008,
  author   = {Wiegand, Kerstin and Saltz, David and Ward, David and Levin, Simon A.},
  title    = {{The role of size inequality in self-thinning: A pattern-oriented simulation model for arid savannas}},
  journal  = {Ecological Modelling},
  year     = {2008},
  volume   = {210},
  number   = {4},
  pages    = {431--445},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/67c049ff0c6457b1c3f2f19ab324ffa5.PDF/Wiegand_et_al_(2008)_ECOL_MODEL_inequality_in_self-thinning.PDF},
  abstract = {The self-thinning line is a very robust pattern, which can be obtained in modeling studies by a variety of different mechanistic assumptions. Our opinion is that we can only advance in our understanding of mechanisms leading to the self-thinning relationship if we demand that the model also reproduces several other characteristic features (patterns) of the self-thinning process such as the degree of size inequality and the average size. We use a pattern-oriented modeling approach to develop a model of self-thinning under size inequality in overcrowded, even-aged stands, which reproduces these three patterns simultaneously. Our approach is to first develop an initial model based on our current ecological knowledge and then to refine the model by modifying the initial model to derive the model that reproduces all patterns of interest. The initial model is as simple as possible while avoiding incidental, ecologically unjustified, assumptions. It is a further development of zone of influence-simulation models: each plant is described by two circles, one describing a minimum-domain-area and one describing the zone of influence. In the initial model, mortality is "death-by-contact" of minimum-domain-areas and growth is a function of inter-tree competition, i.e. overlapping zones of influence. Model parameterization is based on field data on Acacia reficiens in southern Africa. Simulations follow patches of initially small trees through time for up to 1000 years with five parameters, three describing growth and two describing inter-tree competition. A sensitivity analysis shows that all parameters of the initial model contribute significantly to the number and size of plants through time. The two competition parameters, which describe competitive asymmetry and the size of the zone of influence relative to canopy size, are both important for generating size inequality. Thus, both competitive asymmetry and spatial pattern contribute to size inequality, and their relative importance may vary greatly. The sensitivity analysis suggests that all processes included in the initial model are essential to the evolution of size inequality. However, size inequality under the initial model is below field values, meaning that additional, as yet unconsidered processes, contribute to size inequality. Our best-fit model additionally contains details on growth stochasticity. This study establishes the often-proposed direct link between mortality driven by local competition and self-thinning and highlights the importance of stochasticity in ecological processes. ?? 2007 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2007.08.027},
  isbn     = {0304-3800},
  keywords = {Acacia reficiens,Arid savanna,Competitive asymmetry,Namibia,Parsimony,Pattern-oriented modeling,Size inequality,Zone of influence model},
}

The self-thinning line is a very robust pattern, which can be obtained in modeling studies by a variety of different mechanistic assumptions. Our opinion is that we can only advance in our understanding of mechanisms leading to the self-thinning relationship if we demand that the model also reproduces several other characteristic features (patterns) of the self-thinning process such as the degree of size inequality and the average size. We use a pattern-oriented modeling approach to develop a model of self-thinning under size inequality in overcrowded, even-aged stands, which reproduces these three patterns simultaneously. Our approach is to first develop an initial model based on our current ecological knowledge and then to refine the model by modifying the initial model to derive the model that reproduces all patterns of interest. The initial model is as simple as possible while avoiding incidental, ecologically unjustified, assumptions. It is a further development of zone of influence-simulation models: each plant is described by two circles, one describing a minimum-domain-area and one describing the zone of influence. In the initial model, mortality is "death-by-contact" of minimum-domain-areas and growth is a function of inter-tree competition, i.e. overlapping zones of influence. Model parameterization is based on field data on Acacia reficiens in southern Africa. Simulations follow patches of initially small trees through time for up to 1000 years with five parameters, three describing growth and two describing inter-tree competition. A sensitivity analysis shows that all parameters of the initial model contribute significantly to the number and size of plants through time. The two competition parameters, which describe competitive asymmetry and the size of the zone of influence relative to canopy size, are both important for generating size inequality. Thus, both competitive asymmetry and spatial pattern contribute to size inequality, and their relative importance may vary greatly. The sensitivity analysis suggests that all processes included in the initial model are essential to the evolution of size inequality. However, size inequality under the initial model is below field values, meaning that additional, as yet unconsidered processes, contribute to size inequality. Our best-fit model additionally contains details on growth stochasticity. This study establishes the often-proposed direct link between mortality driven by local competition and self-thinning and highlights the importance of stochasticity in ecological processes. ?? 2007 Elsevier B.V. All rights reserved.

@Incollection{Wiegand2008a,
  author    = {Wiegand, Thorsten and Wiegand, Kerstin and P{\"{u}}tz, S.},
  title     = {{Ecological models: Grassland models}},
  booktitle = {Encyclopedia of Ecology},
  publisher = {Elsevier},
  year      = {2008},
  editor    = {Jorgenson, S.E. and Fath, B.D.},
  pages     = {1754--1765},
  address   = {Oxford},
  url_pdf   = {http://uni-goettingen.de/de/document/download/713b68c824c4d0166693b9cfbb90b183.pdf/Wiegand_et_al_(2008)_EncyclopEcol_grassland_models.pdf},
  comment   = {public},
}

@Incollection{Wiegand2008b,
  author    = {Wiegand, Thorsten and Wiegand, Kerstin and P{\"{u}}tz, S.},
  title     = {{Ecological models: Grazing}},
  booktitle = {Encyclopedia of Ecology},
  publisher = {Elsevier},
  year      = {2008},
  editor    = {Jorgenson, S. E. and Fath, B. D.},
  pages     = {1773--1782},
  address   = {Oxford},
  url_pdf   = {http://uni-goettingen.de/de/document/download/35cb344e40e833f9d209e88c95a4bb39.pdf/Wiegand_et_al_(2008)_EncyclopEcol_grazing.pdf},
  comment   = {public},
}

@Article{Aguayo2007,
  author   = {Aguayo, Mauricio and Wiegand, Thorsten and Az{\'{o}}car, Gerardo and Wiegand, Kerstin and Vega, Claudia},
  title    = {{Revealing the Driving Forces of Mid-Cities Urban Growth Patterns Using Spatial Modeling : a Case Study of Los {\'{A}}ngeles , Chile}},
  journal  = {Ecology And Society},
  year     = {2007},
  volume   = {12},
  number   = {1},
  pages    = {13},
  issn     = {1708-3087},
  url_pdf  = {http://uni-goettingen.de/de/document/download/7afb68338802f06a125344ac7c29843b.pdf/Aguayo_et_al_(2007)_ECOLSOC_cities_urban_grpwth_patterns.pdf},
  abstract = {City growth and changes in land-use patterns cause various important social and environmental impacts. To understand the spatial and temporal dynamics of these processes, the factors that drive urban development must be identified and analyzed, especially those factors that can be used to predict future changes and their potential environmental effects. Our objectives were to quantify the relationship between urban growth and its driving forces and to predict the spatial growth pattern based on historical land-use changes for the city of Los {\'{A}}ngeles in central Chile. This involved the analysis of images from 1978, 1992, and 1998 and characterization of the spatial pattern of land-use change; the construction of digital coverage in GIS; the selection of predictive variables through univariate analysis; the construction of logistic regression models using growth vs. nongrowth for 19781992 as the dependent variable; and the prediction of the probability of land-use change by applying the regression model to the 19921998 period. To investigate the influence of spatial scale, we constructed several sets of models that contained (1) only distance variables, e.g., distance to highways; (2) only scale-dependent density variables, e.g., density of urban area within a 600-m radius; (3) both distance and density variables; and (4) both distance and density variables at several spatial scales. The environmental variables were included in all models. The combination of distance and density variables at several scales is required to appropriately capture the multiscale urban growth process. The best models correctly predict {\~{}}90{\%} of the observed land-use changes for 19921998. The distance to access roads, densities of the urban road system and urbanized area at various scales, and soil type were the strongest predictors of the growth pattern. Other variables were less important or not significant in explaining the urban growth process. Our approach, which combines spatial modeling tools and GIS, significantly advances the understanding of urban growth patterns, provides an important contribution to urban planning and management, and can be applied widely.},
  comment  = {public},
  doi      = {10.5751/ES-01970-120113},
  isbn     = {1708-3087},
  keywords = {chile,land use change,logistic regression,los {\'{a}}ngeles,mid cities,modeling,spatially explicit,spatially explicit modeling,urban growth patterns},
  url      = {http://www.programita.de/pdf/AguayoEtAll2007EcologySociety.pdf},
}

City growth and changes in land-use patterns cause various important social and environmental impacts. To understand the spatial and temporal dynamics of these processes, the factors that drive urban development must be identified and analyzed, especially those factors that can be used to predict future changes and their potential environmental effects. Our objectives were to quantify the relationship between urban growth and its driving forces and to predict the spatial growth pattern based on historical land-use changes for the city of Los Ángeles in central Chile. This involved the analysis of images from 1978, 1992, and 1998 and characterization of the spatial pattern of land-use change; the construction of digital coverage in GIS; the selection of predictive variables through univariate analysis; the construction of logistic regression models using growth vs. nongrowth for 19781992 as the dependent variable; and the prediction of the probability of land-use change by applying the regression model to the 19921998 period. To investigate the influence of spatial scale, we constructed several sets of models that contained (1) only distance variables, e.g., distance to highways; (2) only scale-dependent density variables, e.g., density of urban area within a 600-m radius; (3) both distance and density variables; and (4) both distance and density variables at several spatial scales. The environmental variables were included in all models. The combination of distance and density variables at several scales is required to appropriately capture the multiscale urban growth process. The best models correctly predict \ 90% of the observed land-use changes for 19921998. The distance to access roads, densities of the urban road system and urbanized area at various scales, and soil type were the strongest predictors of the growth pattern. Other variables were less important or not significant in explaining the urban growth process. Our approach, which combines spatial modeling tools and GIS, significantly advances the understanding of urban growth patterns, provides an important contribution to urban planning and management, and can be applied widely.

@Book{Getzin2007,
  title     = {{Structural Fire Effects in the World's Savannas. A Synthesis for Biodiversity and Land-Use Managers}},
  publisher = {VDM Verlag},
  year      = {2007},
  author    = {Getzin, Stephan},
  address   = {Saarbr{\"{u}}cken},
  isbn      = {978-3-8364-3664-9},
  comment   = {public},
}

@Article{Getzin2007a,
  author   = {Getzin, Stephan and Wiegand, Kerstin},
  title    = {{Asymmetric tree growth at the stand level: Random crown patterns and the response to slope}},
  journal  = {Forest Ecology and Management},
  year     = {2007},
  volume   = {242},
  number   = {2-3},
  pages    = {165--174},
  issn     = {03781127},
  url_pdf  = {http://uni-goettingen.de/de/document/download/285712100ef2c85e0ed10700386dc737.PDF/Getzin_&_Wiegnad_(2007)_FOREST_ECOL_MANAG%20Asymmetric_tree_growth.PDF},
  abstract = {Asymmetric tree growth is an adaptation to maximise photosynthesis by growing in response to gaps and neighbours, topographical site conditions or incoming solar radiation. Whereas spatial statistics have been widely used to study the distribution of trunk locations, less research has been undertaken to analyse the distribution of crown centres and asymmetric growth at the stand level. It is generally assumed that trees optimise light harvesting via more regular crown patterns. In this study, we primarily ask whether random crown patterns can be found in deciduous and coniferous forests located in continental Europe. Here, we analysed the spatial patterns of trunks, crowns and crowns of overstory trees in different deciduous and coniferous stands, using the scale-dependent g-function and Monte Carlo simulations. We also tested whether the extent of asymmetric growth, that is the crown vector length between the stem-base position and the centroid of the projected crown area, would be greater in angiosperms than in gymnosperms. Finally, we applied circular statistics to test whether trees preferentially bend in slope direction or towards incoming solar radiation. In the deciduous stands, patterns of crowns and upper crowns were random. Response to large-scale heterogeneity in light was strong, because trees bent significantly in downward direction of the slopes. The extent of asymmetric growth was significantly greater in angiosperms than in gymnosperms. The patterns of crowns and upper crowns were regular in a mixed coniferous stand but random in a dense stand with regularly planted Douglas-fir. Mechanical instability caused mutual crown support and attraction between the crowns in this dense stand. The even-aged, slender Douglas-fir clustered significantly in downward direction of the slope. In none of the four stands, trees clustered in southerly direction towards incoming solar radiation. {\textcopyright} 2007 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.foreco.2007.01.009},
  isbn     = {0378-1127},
  keywords = {Coniferous/deciduous stands,Crown vector,Douglas-fir,Light heterogeneity,Slope,g-Function},
}

Asymmetric tree growth is an adaptation to maximise photosynthesis by growing in response to gaps and neighbours, topographical site conditions or incoming solar radiation. Whereas spatial statistics have been widely used to study the distribution of trunk locations, less research has been undertaken to analyse the distribution of crown centres and asymmetric growth at the stand level. It is generally assumed that trees optimise light harvesting via more regular crown patterns. In this study, we primarily ask whether random crown patterns can be found in deciduous and coniferous forests located in continental Europe. Here, we analysed the spatial patterns of trunks, crowns and crowns of overstory trees in different deciduous and coniferous stands, using the scale-dependent g-function and Monte Carlo simulations. We also tested whether the extent of asymmetric growth, that is the crown vector length between the stem-base position and the centroid of the projected crown area, would be greater in angiosperms than in gymnosperms. Finally, we applied circular statistics to test whether trees preferentially bend in slope direction or towards incoming solar radiation. In the deciduous stands, patterns of crowns and upper crowns were random. Response to large-scale heterogeneity in light was strong, because trees bent significantly in downward direction of the slopes. The extent of asymmetric growth was significantly greater in angiosperms than in gymnosperms. The patterns of crowns and upper crowns were regular in a mixed coniferous stand but random in a dense stand with regularly planted Douglas-fir. Mechanical instability caused mutual crown support and attraction between the crowns in this dense stand. The even-aged, slender Douglas-fir clustered significantly in downward direction of the slope. In none of the four stands, trees clustered in southerly direction towards incoming solar radiation. © 2007 Elsevier B.V. All rights reserved.

@Article{Meyer2007,
  author   = {Meyer, Katrin M. and Wiegand, Kerstin and Ward, David and Moustakas, Aristides},
  title    = {{SATCHMO: A spatial simulation model of growth, competition, and mortality in cycling savanna patches}},
  journal  = {Ecological Modelling},
  year     = {2007},
  volume   = {209},
  number   = {2-4},
  pages    = {377--391},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/4a763178b00f98efc035573a13e4f80f.PDF/Meyer_et_al_(2007)_ECOL_MODEL_SATCHMO.PDF},
  abstract = {Many mechanisms have been suggested to explain the coexistence of woody species and grasses in savannas, yet, evidence from field studies and simulation models has been mixed. Shrub encroachment is an ecological and economic problem in savannas worldwide which generally is attributed to overgrazing. Patch-dynamics is a new mechanism explaining tree-grass coexistence and the natural occurrence of shrub encroachment in savannas. A patch-dynamic savanna consists of patches in which cyclical succession between grassy and woody dominance proceeds spatially asynchronously. The spatially explicit, individual-based patch-scale simulation model SATCHMO was developed to investigate cyclical succession in the paradigm of patch-dynamics for arid and semi-arid savannas. SATCHMO is designed to capture within-patch shrub population dynamics based on a grid of 51 m side length and a resolution of 10 cm. The model shrub characteristics were derived from Acacia mellifera, the main encroaching species in African savannas. The aim of SATCHMO is to give a detailed small-scale understanding of above- and belowground growth, competition, and mortality of savanna woody plants and the influence of precipitation and fire on patch transition frequencies, shrub growth rates, and shrub size frequencies. With SATCHMO, we want to identify the conditions leading to cyclical successions in general and shrub encroachment in particular. Soil moisture is the most important parameter in SATCHMO influencing growth, reproduction, and mortality of shrubs and grass tufts, and that mediates competition. To acknowledge the importance of belowground interactions in savannas, shrub root growth and competition are modelled spatially explicitly. The model output was successfully validated with morphometrical and spatial data from the field site in the South African Kalahari thornveld and with recent literature data on savanna woody species cover. Global sensitivity analysis with Latin hypercube sampling shows that soil moisture is the most important driver of shrub cover dynamics in semi-arid savannas. {\textcopyright} 2007 Elsevier B.V. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.ecolmodel.2007.07.001},
  isbn     = {0304-3800},
  keywords = {Acacia mellifera,Computer simulation model,Cyclical succession,Latin Hypercube sensitivity analysis,Patch-dynamics,Shrub encroachment,Spatially explicit root growth,Validation},
}

Many mechanisms have been suggested to explain the coexistence of woody species and grasses in savannas, yet, evidence from field studies and simulation models has been mixed. Shrub encroachment is an ecological and economic problem in savannas worldwide which generally is attributed to overgrazing. Patch-dynamics is a new mechanism explaining tree-grass coexistence and the natural occurrence of shrub encroachment in savannas. A patch-dynamic savanna consists of patches in which cyclical succession between grassy and woody dominance proceeds spatially asynchronously. The spatially explicit, individual-based patch-scale simulation model SATCHMO was developed to investigate cyclical succession in the paradigm of patch-dynamics for arid and semi-arid savannas. SATCHMO is designed to capture within-patch shrub population dynamics based on a grid of 51 m side length and a resolution of 10 cm. The model shrub characteristics were derived from Acacia mellifera, the main encroaching species in African savannas. The aim of SATCHMO is to give a detailed small-scale understanding of above- and belowground growth, competition, and mortality of savanna woody plants and the influence of precipitation and fire on patch transition frequencies, shrub growth rates, and shrub size frequencies. With SATCHMO, we want to identify the conditions leading to cyclical successions in general and shrub encroachment in particular. Soil moisture is the most important parameter in SATCHMO influencing growth, reproduction, and mortality of shrubs and grass tufts, and that mediates competition. To acknowledge the importance of belowground interactions in savannas, shrub root growth and competition are modelled spatially explicitly. The model output was successfully validated with morphometrical and spatial data from the field site in the South African Kalahari thornveld and with recent literature data on savanna woody species cover. Global sensitivity analysis with Latin hypercube sampling shows that soil moisture is the most important driver of shrub cover dynamics in semi-arid savannas. © 2007 Elsevier B.V. All rights reserved.

@Article{Meyer2007a,
  author   = {Meyer, Katrin M. and Wiegand, Kerstin and Ward, David and Moustakas, Aristides},
  title    = {{The rhythm of savanna patch dynamics}},
  journal  = {Journal of Ecology},
  year     = {2007},
  volume   = {95},
  number   = {6},
  pages    = {1306--1315},
  issn     = {00220477},
  url_pdf  = {http://uni-goettingen.de/de/document/download/82119dfd3f6d4240e851d3ad12500dae.PDF/Meyer_et_al_(2007)_J_ECOL_rythem_of_savanna_patch_dynamics.PDF},
  abstract = {1. Patch dynamics is a new, potentially unifying mechanism for the explanation of tree-grass coexistence in savannas. In this scale-explicit paradigm, savannas consist of patches in which a cyclical succession between woody and grassy dominance proceeds spatially asynchronously. The growing ecological and economic problem of shrub encroachment is a natural transient phase in this cycle. 2. An important step towards understanding patterns at the landscape scale is achieved by investigating mechanisms at a smaller scale. We developed the spatially explicit individual-based simulation model SATCHMO to test the null hypothesis that cyclical succession cannot emerge from a realistic patch scale simulation model of the population dynamics of savanna woody species. 3. We calculated the partial temporal autocorrelation coefficient for 100 simulated time series of shrub cover over 500 years for time lags of up to 200 years to establish the existence and duration of successional cycles. We found a significant positive autocorrelation indicating the existence of cycles with a typical duration of about 33 years. 4. The shrub size frequency distributions over the course of a cycle showed shifts from dominance of small shrub sizes towards larger sizes during the increasing phase of a cycle and the reverse in the declining phase. This supports the three phase explanation as follows: (i) an initial phase when spatially and temporally overlapping favourable conditions lead to mass recruitment of shrubs; (ii) a build-up phase when the shrub cohort grows; and (iii) a break-down phase when increased competition due to crowding and unfavourable conditions lead to the break-down of the shrub cohort. The frequency distribution of shrub age at death over 10 simulations was also in agreement with this explanation. 5. We investigated the relationship between shrub cover, annual precipitation and time-lagged shrub cover to identify the driver of the cyclical successions. More than 90{\%} of the variation in shrub cover was explained by shrub cover of the previous year, precipitation, and their interaction. 6. With the demonstration of precipitation-driven cyclical succession at the patch scale, we show that the mechanistic, temporal component of patch dynamics can be used to explain tree-grass coexistence in semi-arid savannas.},
  comment  = {public},
  doi      = {10.1111/j.1365-2745.2007.01289.x},
  isbn     = {0022-0477},
  keywords = {Acacia mellifera,Cyclical succession,Individual-based simulation model,Patch scale,Scale,Shrub encroachment,Size-frequency distributions,Temporal autocorrelation,Tree-grass coexistence},
}

1. Patch dynamics is a new, potentially unifying mechanism for the explanation of tree-grass coexistence in savannas. In this scale-explicit paradigm, savannas consist of patches in which a cyclical succession between woody and grassy dominance proceeds spatially asynchronously. The growing ecological and economic problem of shrub encroachment is a natural transient phase in this cycle. 2. An important step towards understanding patterns at the landscape scale is achieved by investigating mechanisms at a smaller scale. We developed the spatially explicit individual-based simulation model SATCHMO to test the null hypothesis that cyclical succession cannot emerge from a realistic patch scale simulation model of the population dynamics of savanna woody species. 3. We calculated the partial temporal autocorrelation coefficient for 100 simulated time series of shrub cover over 500 years for time lags of up to 200 years to establish the existence and duration of successional cycles. We found a significant positive autocorrelation indicating the existence of cycles with a typical duration of about 33 years. 4. The shrub size frequency distributions over the course of a cycle showed shifts from dominance of small shrub sizes towards larger sizes during the increasing phase of a cycle and the reverse in the declining phase. This supports the three phase explanation as follows: (i) an initial phase when spatially and temporally overlapping favourable conditions lead to mass recruitment of shrubs; (ii) a build-up phase when the shrub cohort grows; and (iii) a break-down phase when increased competition due to crowding and unfavourable conditions lead to the break-down of the shrub cohort. The frequency distribution of shrub age at death over 10 simulations was also in agreement with this explanation. 5. We investigated the relationship between shrub cover, annual precipitation and time-lagged shrub cover to identify the driver of the cyclical successions. More than 90% of the variation in shrub cover was explained by shrub cover of the previous year, precipitation, and their interaction. 6. With the demonstration of precipitation-driven cyclical succession at the patch scale, we show that the mechanistic, temporal component of patch dynamics can be used to explain tree-grass coexistence in semi-arid savannas.

@Article{Ordiz2007,
  author   = {Ordiz, Andr{\'{e}}s and Rodr{\'{i}}guez, Carlos and Naves, Javier and Fern{\'{a}}ndez, Alberto and Huber, Djuro and Kaczensky, Petra and Mertens, Annette and Mertzanis, Georgios and Mustoni, Andrea and Palaz{\'{o}}n, Santiago and Quenette, Pierre Y. and Rauer, Georg and Swenson, Jon E.},
  title    = {{Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe}},
  journal  = {Ursus},
  year     = {2007},
  volume   = {18},
  pages    = {158--167},
  issn     = {1537-6176},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ab42507a6315e034304d480142c8185a.pdf/Ordiz_et_al_(2007)_URSUS_criteria_to_identify_number_of_brown_bear.pdf},
  abstract = {Counts of females with cubs-of-the-year (FWC) have been used as an index for monitoring brown bear (Ursus arctos) populations or estimating a minimum number of adult females in several small and medium-sized populations. Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straightline distances traveled by each FWC using intervals of 1-180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. Differences among FWC in southern and central Europe may be related to habitat characteristics and to the origin (native or released) of the bears we studied. For example, based on the upper 95{\%} prediction interval of the curve fitted of the 80 percentile in the early spring-June period, 2 observations 30 days apart are unlikely to be of the same individual if {\textgreater}13 km apart for FWC in the boreal forest, {\textgreater}15 km and {\textgreater}7 km, respectively, for released and native FWC in southern and central Europe. Our findings may be useful for biologists and managers to help differentiate FWC and thereby estimate the minimum number of family groups present, particularly in areas with low densities of FWC.},
  comment  = {public},
  doi      = {10.2192/1537-6176(2007)18[158:DCTIMN]2.0.CO;2},
  isbn     = {1537-6176},
  pmid     = {9312},
}

Counts of females with cubs-of-the-year (FWC) have been used as an index for monitoring brown bear (Ursus arctos) populations or estimating a minimum number of adult females in several small and medium-sized populations. Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straightline distances traveled by each FWC using intervals of 1-180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. Differences among FWC in southern and central Europe may be related to habitat characteristics and to the origin (native or released) of the bears we studied. For example, based on the upper 95% prediction interval of the curve fitted of the 80 percentile in the early spring-June period, 2 observations 30 days apart are unlikely to be of the same individual if \textgreater13 km apart for FWC in the boreal forest, \textgreater15 km and \textgreater7 km, respectively, for released and native FWC in southern and central Europe. Our findings may be useful for biologists and managers to help differentiate FWC and thereby estimate the minimum number of family groups present, particularly in areas with low densities of FWC.

@Article{Rodriguez2007,
  author   = {Rodriguez, C and Naves, J and Fernandez-Gil, A and Obeso, J R and Delibes, M},
  title    = {{Long-term trends in food habits of a relict brown bear population in northern Spain: The influence of climate and local factors}},
  journal  = {Environmental Conservation},
  year     = {2007},
  volume   = {34},
  number   = {1},
  pages    = {36--44},
  issn     = {03768929},
  url_pdf  = {http://uni-goettingen.de/de/document/download/4692876e9888c2215f20d78dbf4d8d1a.pdf/Rodriguez_et_al_(2007)_ENVIRON_CONSERV_trends_in_food_habits_of_brown_bear.pdf},
  abstract = {Relict endangered populations may be especially vulnerable to the effects of climate change. A data series for the period 1974-2003 was used to examine shifts in brown bear Ursus arctos food habits in its south-westernmost European population. This focused on the hyperphagic season, when bears gain the fat that is essential for winter dormancy and reproduction. General climatic indicators were predictors of diet trends. Other variables potentially able to modify brown bear food habits at the local scale were accounted for by considering two areas where local conditions changed in different ways during the study period. General climatic indicators such as temperature and the winter North Atlantic Oscillation index were good predictors of some diet trends, although local factors seemed to modulate the potential response of food habits to recent climate change. Boreal and temperate food items decreasingly contributed to brown bear diet, replaced by increasing contributions of southern foods, which suggested that warmer temperatures might determine the occurrence of some food items in the diet of Cantabrian brown bears through effects on plant distribution and phenology. At the local scale, high cattle density in one of the study areas limited food sources available for brown bears. Important food sources for brown bears, such as heath-like Vaccinium formations and old-growth oak forest in the Cantabrian Mountains, require increased levels of protection. ¬¨¬{\textcopyright} 2007 Foundation for Environmental Conservation.},
  comment  = {public},
  doi      = {10.1017/S0376892906003535},
  isbn     = {0376-8929},
  keywords = {brown bear,cantabrian mountains,global,interspecific competition,nutritional balance,quercus petraea,ursus arctos,vaccinium myrtillus,warming},
  pmid     = {9062},
}

Relict endangered populations may be especially vulnerable to the effects of climate change. A data series for the period 1974-2003 was used to examine shifts in brown bear Ursus arctos food habits in its south-westernmost European population. This focused on the hyperphagic season, when bears gain the fat that is essential for winter dormancy and reproduction. General climatic indicators were predictors of diet trends. Other variables potentially able to modify brown bear food habits at the local scale were accounted for by considering two areas where local conditions changed in different ways during the study period. General climatic indicators such as temperature and the winter North Atlantic Oscillation index were good predictors of some diet trends, although local factors seemed to modulate the potential response of food habits to recent climate change. Boreal and temperate food items decreasingly contributed to brown bear diet, replaced by increasing contributions of southern foods, which suggested that warmer temperatures might determine the occurrence of some food items in the diet of Cantabrian brown bears through effects on plant distribution and phenology. At the local scale, high cattle density in one of the study areas limited food sources available for brown bears. Important food sources for brown bears, such as heath-like Vaccinium formations and old-growth oak forest in the Cantabrian Mountains, require increased levels of protection. © 2007 Foundation for Environmental Conservation.

@Article{Rodriguez2007a,
  author   = {Rodr{\'{i}}guez, Carlos and Peris, Salvador J.},
  title    = {{Habitat associations of small mammals in farmed landscapes: Implications for agri-environmental schemes}},
  journal  = {Animal Biology},
  year     = {2007},
  volume   = {57},
  number   = {3},
  pages    = {301--314},
  issn     = {15707555},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ae96f3d0e068b09ed985c0ee24947067.pdf/Rodriguez_Peris_2007_ANIMAL_BIOLOGY_habitat_associations_small_mammals_in_farmed_landscapes.pdf},
  abstract = {The small mammal community in 21 localities of north-western Spain was evaluated in the light of land use composition. The two geomorphologic categories characterising the study area, the main use of the land (arable/pastoral) and main crop types of each sampling locality were used as potential predictors of the relative abundance of five common small mammal species. The Common vole, Microtus arvalis showed a weak relationship with land uses, probably due to the recent colonisation process this species experienced in the study area. The relative abundance of the Algerian mouse, Mus spretus and the Lusitanian pine vole, Microtus lusitanicus was best explained by models built at the broadest regional scale, the former being more abundant in the eastern area, the latter in the western area. The Greater white-toothed shrew, Crocidura russula showed a positive relationship with grassland coverage, whilst the Wood mouse, Apodemus sylvaticus benefited from increasing proportions of fallow lands within the landscape. These two species are then expected to respond positively to those agri-environmental schemes including the increase of fallows and grassy vegetation within the arable landscape (EU recommendations). However, further efforts are needed to predict, at least qualitatively, the response of other small mammal species to the changing farmed landscape. This is especially true for two endemic species occurring at this area: the Cabrera vole, Microtus cabrerae and the Lusitanian pine vole, and for which this kind of information is almost absent.},
  comment  = {public},
  doi      = {10.1163/157075607781753092},
  isbn     = {1570-7555},
  keywords = {Agri-environment schemes,Biodiversity,Habitat Preferences,Mediterranean,Small mammals},
}

The small mammal community in 21 localities of north-western Spain was evaluated in the light of land use composition. The two geomorphologic categories characterising the study area, the main use of the land (arable/pastoral) and main crop types of each sampling locality were used as potential predictors of the relative abundance of five common small mammal species. The Common vole, Microtus arvalis showed a weak relationship with land uses, probably due to the recent colonisation process this species experienced in the study area. The relative abundance of the Algerian mouse, Mus spretus and the Lusitanian pine vole, Microtus lusitanicus was best explained by models built at the broadest regional scale, the former being more abundant in the eastern area, the latter in the western area. The Greater white-toothed shrew, Crocidura russula showed a positive relationship with grassland coverage, whilst the Wood mouse, Apodemus sylvaticus benefited from increasing proportions of fallow lands within the landscape. These two species are then expected to respond positively to those agri-environmental schemes including the increase of fallows and grassy vegetation within the arable landscape (EU recommendations). However, further efforts are needed to predict, at least qualitatively, the response of other small mammal species to the changing farmed landscape. This is especially true for two endemic species occurring at this area: the Cabrera vole, Microtus cabrerae and the Lusitanian pine vole, and for which this kind of information is almost absent.

@Phdthesis{Getzin2006,
  author  = {Getzin, Stephan},
  title   = {{Analysis of hierarchical structures in forest stands using detailed spatial statistics}},
  year    = {2006},
  url_pdf = {http://uni-goettingen.de/de/document/download/77893e401cc0efe821cad4d616463948.PDF/Getzin_(2006)_DISS_Analysis_of_hierarchical_structures.PDF},
  comment = {public},
}

@Article{Getzin2006a,
  author   = {Getzin, Stephan and Dean, Charmaine and He, Fangliang and {A. Trofymow}, John and Wiegand, Kerstin and Wiegand, Thorsten},
  title    = {{Spatial patterns and competition of tree species in a Douglas-fir chronosequence on Vancouver Island}},
  journal  = {Ecography},
  year     = {2006},
  volume   = {29},
  number   = {5},
  pages    = {671--682},
  issn     = {09067590},
  url_pdf  = {http://uni-goettingen.de/de/document/download/97fa0ee3036165e1aaf303bfc30ee56c.PDF/Getzin_et_al_(2006)_ECOGRAPHY_%20Spatial_patterns_and_competition.PDF},
  abstract = {While the successional dynamics and large-scale structure of Douglas-fir forest in the Pacific Northwest region is well studied, the fine-scale spatial characteristics at the stand level are still poorly understood. Here we investigated the fine-scale spatial structure of forest on Vancouver Island, in order to understand how the three dominant species, Douglas-fir, western hemlock, and western redcedar, coexist and partition space along a chronosequence comprised of immature, mature, and old-growth stands. We quantified the changes in spatial distribution and association of the species along the chronosequence using the scale-dependent point pattern analyses pair-correlation function g(r) and Ripley's L-function. Evidence on intra- and inter-specific competition was also inferred from correlations between nearest-neighbor distances and tree size. Our results show that 1) the aggregation of Douglas-fir in old-growth was primarily caused by variation in local site characteristics, 2) only surviving hemlock were more regular than their pre-mortality patterns, a result consistent with strong intra-specific competition, 3) inter-specific competition declined rapidly with stand age due to spatial resource partitioning, and (4) tree death was spatially randomly distributed among larger overstory trees. The study highlights the importance of spatial heterogeneity for the long-term coexistence of shade-intolerant pioneer Douglas-fir and shade-tolerant western hemlock and western redcedar},
  comment  = {public},
  doi      = {10.1111/j.2006.0906-7590.04675.x},
  isbn     = {0906-7590},
  pmid     = {2013},
}

While the successional dynamics and large-scale structure of Douglas-fir forest in the Pacific Northwest region is well studied, the fine-scale spatial characteristics at the stand level are still poorly understood. Here we investigated the fine-scale spatial structure of forest on Vancouver Island, in order to understand how the three dominant species, Douglas-fir, western hemlock, and western redcedar, coexist and partition space along a chronosequence comprised of immature, mature, and old-growth stands. We quantified the changes in spatial distribution and association of the species along the chronosequence using the scale-dependent point pattern analyses pair-correlation function g(r) and Ripley's L-function. Evidence on intra- and inter-specific competition was also inferred from correlations between nearest-neighbor distances and tree size. Our results show that 1) the aggregation of Douglas-fir in old-growth was primarily caused by variation in local site characteristics, 2) only surviving hemlock were more regular than their pre-mortality patterns, a result consistent with strong intra-specific competition, 3) inter-specific competition declined rapidly with stand age due to spatial resource partitioning, and (4) tree death was spatially randomly distributed among larger overstory trees. The study highlights the importance of spatial heterogeneity for the long-term coexistence of shade-intolerant pioneer Douglas-fir and shade-tolerant western hemlock and western redcedar

@Phdthesis{Meyer2006,
  author  = {Meyer, Katrin M.},
  title   = {{Cyclical succession in semi-arid savannas revealed with a spatial simulation model}},
  year    = {2006},
  url_pdf = {http://uni-goettingen.de/de/document/download/3324f16f6a3ed787fc04d3514cf87e42.PDF/Meyer_(2006)_DISS_Cyclical_succession.PDF},
  comment = {public},
}

@Phdthesis{Moustakas2006,
  author  = {Moustakas, Aristides},
  title   = {{Long-term vegetation dynamics of African savannas at a landscape level}},
  year    = {2006},
  url_pdf = {http://uni-goettingen.de/de/document/download/44b46bf40a94772386ccf43078178bc3.PDF/Moustakas_(2006)_DISS_Long-term_vegetation_dynamics.PDF},
  comment = {public},
}

@Article{Moustakas2006a,
  author   = {Moustakas, Aristides and Guenther, Matthias and Wiegand, Kerstin and Mueller, Karl-Heinz and Ward, David and Meyer, Katrin M and Jeltsch, Florian},
  title    = {{Long-term mortality patterns of the deep-rooted Acacia erioloba : The middle class shall die !}},
  journal  = {Journal of Vegetation Science},
  year     = {2006},
  volume   = {17},
  pages    = {473--480},
  issn     = {1100-9233},
  url_pdf  = {http://uni-goettingen.de/de/document/download/f9469c643624fe2e9a371ae291b78819.PDF/Moustakas_et_al_(2006)_J_VEG_SCI_Long-term_mortality_patterns.PDF},
  abstract = {Question: Is there a relationship between size and death in the long-lived, deep-rooted tree, Acacia erioloba, in a semi-arid savanna? What is the size-class distribution of A.erioloba mortality? Does the mortality distribution differ from total tree size distribution? Does A. erioloba mortality distribution match the mortality distributions recorded thus far in other environments? Location: Dronfield Ranch, near Kimberley, Kalahari, South Africa. Methods: A combination of aerial photographs and a satellite image covering 61 years was used to provide long-term spatial data on mortality. We used aerial photographs of the study area from 1940, 1964, 1993 and a satellite image from 2001 to follow three plots covering 510 ha. We were able to identify and individually follow ca. 3000 individual trees from 1940 till 2001. Results: The total number of trees increased over time. No relationship between total number of trees and mean tree size was detected. There were no trends over time in total number of deaths per plot or in the size distributions of dead trees. Kolmogorov-Smirnov tests showed no differences in size class distributions for living trees through time. The size distribution of dead trees was significantly different from the size distribution of all trees present on the plots. Overall, the number of dead trees was low in small size classes, reached a peak value when canopy area was 20-30m2, and declined in larger size-classes. Mortality as a ratio of dead vs. total trees peaked at intermediate canopy sizes too. Conclusion: A.erioloba mortality was size-dependent, peaking at intermediate sizes. THe mortality distribution differs from all other tree mortality distributions recorded thus far. We suggest that a possible mechanism for this unusual mortality distribution is intraspecific competition for water in this semi-arid environment.},
  comment  = {public},
  doi      = {10.1111/j.1654-1103.2006.tb02468.x},
  isbn     = {1100-9233},
  keywords = {competition,long-term data,remote sensing,savanna,size dependent mortality,size distribution,tree},
}

Question: Is there a relationship between size and death in the long-lived, deep-rooted tree, Acacia erioloba, in a semi-arid savanna? What is the size-class distribution of A.erioloba mortality? Does the mortality distribution differ from total tree size distribution? Does A. erioloba mortality distribution match the mortality distributions recorded thus far in other environments? Location: Dronfield Ranch, near Kimberley, Kalahari, South Africa. Methods: A combination of aerial photographs and a satellite image covering 61 years was used to provide long-term spatial data on mortality. We used aerial photographs of the study area from 1940, 1964, 1993 and a satellite image from 2001 to follow three plots covering 510 ha. We were able to identify and individually follow ca. 3000 individual trees from 1940 till 2001. Results: The total number of trees increased over time. No relationship between total number of trees and mean tree size was detected. There were no trends over time in total number of deaths per plot or in the size distributions of dead trees. Kolmogorov-Smirnov tests showed no differences in size class distributions for living trees through time. The size distribution of dead trees was significantly different from the size distribution of all trees present on the plots. Overall, the number of dead trees was low in small size classes, reached a peak value when canopy area was 20-30m2, and declined in larger size-classes. Mortality as a ratio of dead vs. total trees peaked at intermediate canopy sizes too. Conclusion: A.erioloba mortality was size-dependent, peaking at intermediate sizes. THe mortality distribution differs from all other tree mortality distributions recorded thus far. We suggest that a possible mechanism for this unusual mortality distribution is intraspecific competition for water in this semi-arid environment.

@Article{Pfeifer2006,
  author   = {Pfeifer, Marion and Wiegand, Kerstin and Heinrich, Wolfgang and Jetschke, Gottfried},
  title    = {{Long-term demographic fluctuations in an orchid species driven by weather: Implications for conservation planning}},
  journal  = {Journal of Applied Ecology},
  year     = {2006},
  volume   = {43},
  number   = {2},
  pages    = {313--324},
  issn     = {00218901},
  url_pdf  = {http://uni-goettingen.de/de/document/download/1b366b41fd67bed0dc16dbc459f764a3.PDF/Pfeifer_et_al_(2006)_J_APPL_ECOL_Long-term_demographic_fluctuations.PDF},
  abstract = {1. Management decisions are increasingly based on matrix models intended to predict the long-term fate of endangered species. However, certain elements of these models, such as life-state transition probabilities (vital rates), are difficult to parameterize and their values may vary depending on external conditions such as weather. Details of how weather might influence population performance are rare, yet necessary to assess the effects of global climate change on a species' distribution. 2. Based on a 26-year data set of a population of Himantoglossum hircinum in a nature reserve in Germany, variations of life-history traits and vital rates were studied. Matrix analysis was used to identify the most important life-state transitions for population growth. Multiple linear regression was used to quantify the response of population traits and vital rates to changing weather conditions. 3. Population size increased exponentially and density effects could not be observed. Flowering plants and large plants had the highest and second highest reproductive value, respectively. The population's finite rate of increase fluctuated strongly among years; life-history traits varied strongly and were interlinked, thereby violating the assumptions of matrix modelling in a population viability analysis. 4. Some vital rates and the population growth rate showed a trend over the total period. A certain and sometimes large amount of that variability could be attributed to variability of weather conditions, with warmer winter conditions favouring population performance. Prediction of population size was fairly accurate within a time frame of 10 years, but size class structure was not. 5. Synthesis and applications. Matrix modelling proved to be unreliable for predicting long-term population dynamics, despite the long-term data set used for matrix construction. This can be explained by weather-dependent variability of vital rates driving population dynamics. A minimum study period of 4 years is necessary to produce relevant information for model development. Our study emphasizes the need for critical evaluation of management decisions based only on single short-term studies and for studies covering longer time intervals than 2-3 years.},
  comment  = {public},
  doi      = {10.1111/j.1365-2664.2006.01148.x},
  isbn     = {0021-8901},
  keywords = {Climate change,Conservation,Long-term predictions,PVA,Protected species},
}

1. Management decisions are increasingly based on matrix models intended to predict the long-term fate of endangered species. However, certain elements of these models, such as life-state transition probabilities (vital rates), are difficult to parameterize and their values may vary depending on external conditions such as weather. Details of how weather might influence population performance are rare, yet necessary to assess the effects of global climate change on a species' distribution. 2. Based on a 26-year data set of a population of Himantoglossum hircinum in a nature reserve in Germany, variations of life-history traits and vital rates were studied. Matrix analysis was used to identify the most important life-state transitions for population growth. Multiple linear regression was used to quantify the response of population traits and vital rates to changing weather conditions. 3. Population size increased exponentially and density effects could not be observed. Flowering plants and large plants had the highest and second highest reproductive value, respectively. The population's finite rate of increase fluctuated strongly among years; life-history traits varied strongly and were interlinked, thereby violating the assumptions of matrix modelling in a population viability analysis. 4. Some vital rates and the population growth rate showed a trend over the total period. A certain and sometimes large amount of that variability could be attributed to variability of weather conditions, with warmer winter conditions favouring population performance. Prediction of population size was fairly accurate within a time frame of 10 years, but size class structure was not. 5. Synthesis and applications. Matrix modelling proved to be unreliable for predicting long-term population dynamics, despite the long-term data set used for matrix construction. This can be explained by weather-dependent variability of vital rates driving population dynamics. A minimum study period of 4 years is necessary to produce relevant information for model development. Our study emphasizes the need for critical evaluation of management decisions based only on single short-term studies and for studies covering longer time intervals than 2-3 years.

@Article{Wiegand2006,
  author   = {Wiegand, Kerstin and Saltz, David and Ward, David},
  title    = {{A patch-dynamics approach to savanna dynamics and woody plant encroachment - Insights from an arid savanna}},
  journal  = {Perspectives in Plant Ecology, Evolution and Systematics},
  year     = {2006},
  volume   = {7},
  number   = {4},
  pages    = {229--242},
  issn     = {16180437},
  url_pdf  = {http://uni-goettingen.de/de/document/download/a593852992e5a62f6003d8bd6e5ac176.PDF/Wiegand_et_al_(2006)_PERSP_ECOL_EVOL_SYSTEM_A_patch_dynamics_approach.PDF},
  abstract = {The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in 'two-layer systems'. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment. We present an alternative hypothesis explaining both tree-grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity. We conclude that field studies are more likely to contribute to a general understanding of tree-grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas. {\textcopyright} 2005 R{\"{u}}bel Foundation, ETH Z{\"{u}}rich. Published by Elsevier GmbH. All rights reserved.},
  comment  = {public},
  doi      = {10.1016/j.ppees.2005.10.001},
  isbn     = {1433-8319},
  keywords = {Fire,Grazing,Honeycomb rippling model,Inter-tree competition,Spatio-temporal rainfall variation,Tree-grass coexistence},
  pmid     = {515},
}

The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in 'two-layer systems'. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment. We present an alternative hypothesis explaining both tree-grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity. We conclude that field studies are more likely to contribute to a general understanding of tree-grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas. © 2005 Rübel Foundation, ETH Zürich. Published by Elsevier GmbH. All rights reserved.

@Inproceedings{Getzin2005,
  author    = {Getzin, Stephan},
  title     = {{The suitability of the degradation gradient method in arid Namibia}},
  booktitle = {African Journal of Ecology},
  year      = {2005},
  volume    = {43},
  number    = {4},
  pages     = {340--351},
  url_pdf   = {http://uni-goettingen.de/de/document/download/7f97943fe2f648f8e5b07ca643b2ff9c.PDF/Getzin_(2005)_AFR_J_ECOL_degradation_gradient_method_in_arid_Namibia.PDF},
  abstract  = {The Degradation Gradient Method (DGM) is a sophisticated technique for the assessment of range condition. It applies multivariate analyses of herbaceous species data to detect subtle degrees of overgrazing. The suitability of this multivariate method was tested in the central Highland Savanna of Namibia by comparing its results against a univariate analysis of herbaceous data in a simple but robust Range-Unit Model. Despite aridity and topographical heterogeneity, the DGM performed unexpectedly well under these conditions. The relative instability of this dry savanna system favoured the applicability of the DGM by promoting a clear grazing gradient. Using species density data only resulted in an incorrect outcome of the multivariate analysis. The sensitivity of the DGM could be improved by combining density and cover data.},
  comment   = {public},
  doi       = {10.1111/j.1365-2028.2005.00589.x},
  isbn      = {0141-6707},
  issn      = {01416707},
  keywords  = {Aridity,Cover and density data,Grazing gradient,Ordinations,Species response curves,Topographical heterogeneity},
}

The Degradation Gradient Method (DGM) is a sophisticated technique for the assessment of range condition. It applies multivariate analyses of herbaceous species data to detect subtle degrees of overgrazing. The suitability of this multivariate method was tested in the central Highland Savanna of Namibia by comparing its results against a univariate analysis of herbaceous data in a simple but robust Range-Unit Model. Despite aridity and topographical heterogeneity, the DGM performed unexpectedly well under these conditions. The relative instability of this dry savanna system favoured the applicability of the DGM by promoting a clear grazing gradient. Using species density data only resulted in an incorrect outcome of the multivariate analysis. The sensitivity of the DGM could be improved by combining density and cover data.

@Article{Meyer2005,
  author   = {Meyer, Katrin M. and Ward, David and Moustakas, Aristides and Wiegand, Kerstin},
  title    = {{Big is not better: Small Acacia mellifera shrubs are more vital after fire}},
  journal  = {African Journal of Ecology},
  year     = {2005},
  volume   = {43},
  number   = {2},
  pages    = {131--136},
  issn     = {01416707},
  url_pdf  = {http://uni-goettingen.de/de/document/download/913f6bea21e312a85cade13234233b53.PDF/Meyer_et_al_(2005)_AFR_J_ECOL_%20Big_is_not_better.PDF},
  abstract = {Fire and acacias are vital components in savanna dynamics but little is known about the relationship between postfire mortality and size of Acacia species. We determined mortality, height, and height of resprouts of the encroaching shrub species Acacia mellifera in a semi-arid South African savanna 2 years after fire. As expected, resprouting ability after topkill was high, only 9{\%} of the studied shrubs died completely. Surprisingly, shrubs that died in the fire were significantly taller than their resprouting conspecifics. Results from quantile regression show that the height of regrowth relative to the total height of taller shrubs is less than in smaller shrubs, despite taller shrubs having more access to below-ground resources. We offer two possible explanations for these unexpected results: in taller shrubs, the maximum longitudinal growth rate of resprouts may be reached and therefore, resources may be invested in a greater number of resprouts or stored as reserves. Alternatively, resprouting ability may be impaired in old age by a senescence effect caused by the accumulation of physiological dysfunctions.},
  comment  = {public},
  doi      = {10.1111/j.1365-2028.2005.00559.x},
  isbn     = {0141-6707},
  keywords = {Below-ground traits,Flame zone,Kalahari thornveld,Limiting factors,Roots,Size},
}

Fire and acacias are vital components in savanna dynamics but little is known about the relationship between postfire mortality and size of Acacia species. We determined mortality, height, and height of resprouts of the encroaching shrub species Acacia mellifera in a semi-arid South African savanna 2 years after fire. As expected, resprouting ability after topkill was high, only 9% of the studied shrubs died completely. Surprisingly, shrubs that died in the fire were significantly taller than their resprouting conspecifics. Results from quantile regression show that the height of regrowth relative to the total height of taller shrubs is less than in smaller shrubs, despite taller shrubs having more access to below-ground resources. We offer two possible explanations for these unexpected results: in taller shrubs, the maximum longitudinal growth rate of resprouts may be reached and therefore, resources may be invested in a greater number of resprouts or stored as reserves. Alternatively, resprouting ability may be impaired in old age by a senescence effect caused by the accumulation of physiological dysfunctions.

@Article{Wiegand2005,
  author   = {Wiegand, Kerstin and Ward, David and Saltz, David},
  title    = {{Multi-scale patterns and bush encroachment in an arid savanna with a shallow soil layer}},
  journal  = {Journal of Vegetation Science},
  year     = {2005},
  volume   = {16},
  number   = {3},
  pages    = {311--320},
  issn     = {11009233},
  url_pdf  = {http://uni-goettingen.de/de/document/download/e0004c615e46089132001a2b61b608cf.PDF/Wiegand_et_al_(2005)_J_VEG_SCI_Multi-scale_patterns_and_bush_encroachment.PDF},
  abstract = {Question: Bush encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and threatens the livelihood of many pastoralists. Can we derive a better understanding of the factors causing bush encroachment by investigating the scale dependency of patterns and processes in savannas? Location: An and savanna in the Khomas Hochland, Namibia. Methods: Patterns of bush, grass, and soil nutrient distribution were surveyed on several scales along a rainfall gradient, with emphasis on intraspecific interactions within the dominant woody species, Acacia reficiens. Results: Savannas can be interpreted as patch-dynamic systems where landscapes are composed of many patches (a few ha in size) in different states of transition between grassy and woody dominance. Conclusions: In and savannas, this patchiness is driven both by rainfall that is highly variable in space and time and by inter-tree competition. Within the paradigm of patch-dynamic savannas, bush encroachment is part of a cyclical succession between open savanna and woody dominance. The conversion from a patch of open savanna to a bush-encroached area is initiated by the spatial and temporal overlap of several (localized) rainfall events sufficient for Acacia germination and establishment. With time, growth and self-thinning will transform the bush-encroached area into a mature Acacia stand and eventually into open savanna again. Patchiness is sustained due to the local rarity (and patchiness) of rainfall sufficient for germination of woody plants as well as by plant-soil interactions.},
  comment  = {public},
  doi      = {10.1111/j.1654-1103.2005.tb02369.x},
  isbn     = {1100-9233},
  pmid     = {4054},
  url      = {http://doi.wiley.com/10.1111/j.1654-1103.2005.tb02369.x},
}

Question: Bush encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and threatens the livelihood of many pastoralists. Can we derive a better understanding of the factors causing bush encroachment by investigating the scale dependency of patterns and processes in savannas? Location: An and savanna in the Khomas Hochland, Namibia. Methods: Patterns of bush, grass, and soil nutrient distribution were surveyed on several scales along a rainfall gradient, with emphasis on intraspecific interactions within the dominant woody species, Acacia reficiens. Results: Savannas can be interpreted as patch-dynamic systems where landscapes are composed of many patches (a few ha in size) in different states of transition between grassy and woody dominance. Conclusions: In and savannas, this patchiness is driven both by rainfall that is highly variable in space and time and by inter-tree competition. Within the paradigm of patch-dynamic savannas, bush encroachment is part of a cyclical succession between open savanna and woody dominance. The conversion from a patch of open savanna to a bush-encroached area is initiated by the spatial and temporal overlap of several (localized) rainfall events sufficient for Acacia germination and establishment. With time, growth and self-thinning will transform the bush-encroached area into a mature Acacia stand and eventually into open savanna again. Patchiness is sustained due to the local rarity (and patchiness) of rainfall sufficient for germination of woody plants as well as by plant-soil interactions.

@Misc{Chesson2004,
  author    = {Chesson, Peter and Gebauer, Renate L.E. and Schwinning, Susan and Huntly, Nancy and Wiegand, Kerstin and Ernest, Morgan S.K. and Sher, Anna and Novoplansky, Ariel and Weltzin, Jake F.},
  title     = {{Resource pulses, species interactions, and diversity maintenance in arid and semi-arid environments}},
  year      = {2004},
  url_pdf   = {http://uni-goettingen.de/de/document/download/c93ad2048ac7b56052882d45015365c0.pdf/Chesson_et_al_(2004)_OECOLOGICA_resource_pulses_species_interactions_and_diversity_maintenance.pdf},
  abstract  = {Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.},
  booktitle = {Oecologia},
  comment   = {public},
  doi       = {10.1007/s00442-004-1551-1},
  isbn      = {00298549},
  issn      = {00298549},
  keywords  = {Coexistence,Environmental variability,Precipitation,Relative nonlinearity,Storage effect},
  number    = {2},
  pages     = {236--253},
  pmid      = {15069635},
  volume    = {141},
}

Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.

@Misc{Henle2004,
  author        = {Henle, Klaus and Sarre, Stephen and Wiegand, Kerstin},
  title         = {{The role of density regulation in extinction processes and population viability analysis}},
  year          = {2004},
  url_pdf       = {http://uni-goettingen.de/de/document/download/d9e594720187bbe3ffcf2cb51cf1a0f8.PDF/Henle_et_al_(2004)_BIODIVERS_CONSERV_density_regulation.PDF},
  abstract      = {We review the role of density dependence in the stochastic extinction of populations and the role density dependence has played in population viability analysis (PVA) case studies. In total, 32 approaches have been used to model density regulation in theoretical or applied extinction models, 29 of them are mathematical functions of density dependence, and one approach uses empirical relationships between density and survival, reproduction, or growth rates. In addition, quasi-extinction levels are sometimes applied as a substitute for density dependence at low population size. Density dependence further has been modelled via explicit individual spacing behaviour and/or dispersal. We briefly summarise the features of density dependence available in standard PVA software, provide summary statistics about the use of density dependence in PVA case studies, and discuss the effects of density dependence on extinction probability. The introduction of an upper limit for population size has the effect that the probability of ultimate extinction becomes 1. Mean time to extinction increases with carrying capacity if populations start at high density, but carrying capacity often does not have any effect if populations start at low numbers. In contrast, the Allee effect is usually strong when populations start at low densities but has only a limited influence on persistence when populations start at high numbers. Contrary to previous opinions, other forms of density dependence may lead to increased or decreased persistence, depending on the type and strength of density dependence, the degree of environmental variability, and the growth rate. Furthermore, effects may be reversed for different quasi-extinction levels, making the use of arbitrary quasi-extinction levels problematic. Few systematic comparisons of the effects on persistence between different models of density dependence are available. These effects can be strikingly different among models. Our understanding of the effects of density dependence on extinction of metapopulations is rudimentary, but even opposite effects of density dependence can occur when metapopulations and single populations are contrasted. We argue that spatially explicit models hold particular promise for analysing the effects of density dependence on population viability provided a good knowledge of the biology of the species under consideration exists. Since the results of PVAs may critically depend on the way density dependence is modelled, combined efforts to advance statistical methods, field sampling, and modelling are urgently needed to elucidate the relationships between density, vital rates, and extinction probability.},
  archiveprefix = {arXiv},
  arxivid       = {arXiv:1112.2903v1},
  booktitle     = {Biodiversity and Conservation},
  comment       = {public},
  doi           = {10.1023/B:BIOC.0000004312.41575.83},
  eprint        = {arXiv:1112.2903v1},
  isbn          = {0960-3115},
  issn          = {09603115},
  keywords      = {Allee effect,Ceiling carrying capacity,Density dependence,Extinction,Population viability analysis,Software,Spatially explicit models,Stochastic population models},
  number        = {1},
  pages         = {9--52},
  pmid          = {1052},
  volume        = {13},
}

We review the role of density dependence in the stochastic extinction of populations and the role density dependence has played in population viability analysis (PVA) case studies. In total, 32 approaches have been used to model density regulation in theoretical or applied extinction models, 29 of them are mathematical functions of density dependence, and one approach uses empirical relationships between density and survival, reproduction, or growth rates. In addition, quasi-extinction levels are sometimes applied as a substitute for density dependence at low population size. Density dependence further has been modelled via explicit individual spacing behaviour and/or dispersal. We briefly summarise the features of density dependence available in standard PVA software, provide summary statistics about the use of density dependence in PVA case studies, and discuss the effects of density dependence on extinction probability. The introduction of an upper limit for population size has the effect that the probability of ultimate extinction becomes 1. Mean time to extinction increases with carrying capacity if populations start at high density, but carrying capacity often does not have any effect if populations start at low numbers. In contrast, the Allee effect is usually strong when populations start at low densities but has only a limited influence on persistence when populations start at high numbers. Contrary to previous opinions, other forms of density dependence may lead to increased or decreased persistence, depending on the type and strength of density dependence, the degree of environmental variability, and the growth rate. Furthermore, effects may be reversed for different quasi-extinction levels, making the use of arbitrary quasi-extinction levels problematic. Few systematic comparisons of the effects on persistence between different models of density dependence are available. These effects can be strikingly different among models. Our understanding of the effects of density dependence on extinction of metapopulations is rudimentary, but even opposite effects of density dependence can occur when metapopulations and single populations are contrasted. We argue that spatially explicit models hold particular promise for analysing the effects of density dependence on population viability provided a good knowledge of the biology of the species under consideration exists. Since the results of PVAs may critically depend on the way density dependence is modelled, combined efforts to advance statistical methods, field sampling, and modelling are urgently needed to elucidate the relationships between density, vital rates, and extinction probability.

@Article{Wiegand2004,
  author   = {Wiegand, Kerstin and Jeltsch, Florian and Ward, David},
  title    = {{Minimum recruitment frequency in plants with episodic recruitment}},
  journal  = {Oecologia},
  year     = {2004},
  volume   = {141},
  number   = {2},
  pages    = {363--372},
  issn     = {00298549},
  url_pdf  = {http://uni-goettingen.de/de/document/download/f0aa343eaf96db8f9e71253958877e77.PDF/Wiegand_et_al_(2004)_OECOLOGIA_Minimum_recruitment.PDF},
  abstract = {There is concern about the lack of recruitment of Acacia trees in the Negev desert of Israel. We have developed three models to estimate the frequency of recruitment necessary for long-term population survival (i.e. positive average population growth for 1,000 years and {\textless} 10{\%} probability of extinction). Two models assume purely episodic recruitment based on the general notion that recruitment in arid environments is highly episodic. They differ in that the deterministic model investigates average dynamics while the stochastic model does not. Studies indicating that recruitment episodes in arid environments have been overemphasized motivated the development of the third model. This semi-stochastic model simulates a mixture of continuous and episodic recruitment. Model analysis was done analytically for the deterministic model and via running model simulations for the stochastic and semi-stochastic models. The deterministic and stochastic models predict that, on average, 2.2 and 3.7 recruitment events per century, respectively, are necessary to sustain the population. According to the semi-stochastic model, 1.6 large recruitment events per century and an annual probability of 50{\%} that a small recruitment event occurs are needed. A consequence of purely episodic recruitment is that all recruitment episodes produce extremely large numbers of recruits (i.e. at odds with field observations), an evaluation that holds even when considering that rare events must be large. Thus, the semi-stochastic model appears to be the most realistic model. Comparing the prediction of the semi-stochastic model to field observations in the Negev desert shows that the absence of observations of extremely large recruitment events is no reason for concern. However, the almost complete absence of small recruitment events is a serious reason for concern. The lack of recruitment may be due to decreased densities of large mammalian herbivores and might be further exacerbated by possible changes in climate, both in terms of average precipitation and the temporal distribution of rain.},
  comment  = {public},
  doi      = {10.1007/s00442-003-1439-5},
  isbn     = {4936419494},
  keywords = {Acacia,Arid environments,Extinction,Simulation models},
  pmid     = {14666416},
}

There is concern about the lack of recruitment of Acacia trees in the Negev desert of Israel. We have developed three models to estimate the frequency of recruitment necessary for long-term population survival (i.e. positive average population growth for 1,000 years and \textless 10% probability of extinction). Two models assume purely episodic recruitment based on the general notion that recruitment in arid environments is highly episodic. They differ in that the deterministic model investigates average dynamics while the stochastic model does not. Studies indicating that recruitment episodes in arid environments have been overemphasized motivated the development of the third model. This semi-stochastic model simulates a mixture of continuous and episodic recruitment. Model analysis was done analytically for the deterministic model and via running model simulations for the stochastic and semi-stochastic models. The deterministic and stochastic models predict that, on average, 2.2 and 3.7 recruitment events per century, respectively, are necessary to sustain the population. According to the semi-stochastic model, 1.6 large recruitment events per century and an annual probability of 50% that a small recruitment event occurs are needed. A consequence of purely episodic recruitment is that all recruitment episodes produce extremely large numbers of recruits (i.e. at odds with field observations), an evaluation that holds even when considering that rare events must be large. Thus, the semi-stochastic model appears to be the most realistic model. Comparing the prediction of the semi-stochastic model to field observations in the Negev desert shows that the absence of observations of extremely large recruitment events is no reason for concern. However, the almost complete absence of small recruitment events is a serious reason for concern. The lack of recruitment may be due to decreased densities of large mammalian herbivores and might be further exacerbated by possible changes in climate, both in terms of average precipitation and the temporal distribution of rain.

@Article{Chave2002,
  author   = {Chave, Jerome and Wiegand, Kerstin and Levin, Simon},
  title    = {{Spatial and biological aspects of reserve design}},
  journal  = {Environmental Modeling and Assessment},
  year     = {2002},
  volume   = {7},
  number   = {2},
  pages    = {115--122},
  issn     = {14202026},
  url_pdf  = {http://uni-goettingen.de/de/document/download/15ee1c016d7d36ca6bf059e51fd129ef.PDF/Chave_et_al_(2002)_ENVIRON_MODEL_ASSESS_Spatial_and_biological_aspects_of_reserve_design.PDF},
  abstract = {The optimal spatial design of protected reserves requires attention to the biological mechanisms underlying community organization, and sustaining ecosystem services. Identifying the key mechanisms is especially difficult in species-rich ecosystems. We investigate the example of the tropical rainforest, a biome that is under threat of continuing fragmentation, yet which shelters the majority of living species on Earth. Simple dynamic and spatially explicit simulations, which model the dynamics of plant communities, allow us to elucidate the interplay between patterns of fragmentation and seed dispersal mechanisms in maintaining biodiversity.},
  comment  = {public},
  doi      = {10.1023/A:1015601800181},
  isbn     = {1420-2026},
  pmid     = {175806000008},
}

The optimal spatial design of protected reserves requires attention to the biological mechanisms underlying community organization, and sustaining ecosystem services. Identifying the key mechanisms is especially difficult in species-rich ecosystems. We investigate the example of the tropical rainforest, a biome that is under threat of continuing fragmentation, yet which shelters the majority of living species on Earth. Simple dynamic and spatially explicit simulations, which model the dynamics of plant communities, allow us to elucidate the interplay between patterns of fragmentation and seed dispersal mechanisms in maintaining biodiversity.

@Article{Wiegand2002,
  author   = {Wiegand, Kerstin and Henle, Klaus and Sarre, Stephen D.},
  title    = {{Extinction and spatial structure in simulation models}},
  journal  = {Conservation Biology},
  year     = {2002},
  volume   = {16},
  number   = {1},
  pages    = {117--128},
  issn     = {08888892},
  url_pdf  = {http://uni-goettingen.de/de/document/download/d554c7fd9ba2ea988087519f25fca902.pdf/Wiegand_et_al_(2002)_CONS_BIOL_extinction_and_spatial_structure.pdf},
  abstract = {Aspects of within-population spatial structure are often neglected in the modeling of population viability. To analyze the relevance of the spatial structure of single populations to population persistence, we compared the results of three models developed for the territorial, arboreal gecko Oedura reticulata., (1) a spatially structured model in which both low and high densities incur mortality costs due to increased movement, (2) a spatially structured model in which the Allee effect is removed, and (3) a spatially unstructured model in which there are no effects of density on mortality. Compared with nonspatial model populations, spatially structured populations exhibited reduced persistence. The Allee effect contributed only a small amount to the reduction in persistence. Increased mortality at high densities caused by difficulties in finding territories markedly reduced persistence in the spatially structured models compared with the density-independent nonspatial model, TV,e argue that the inclusion of elements of spatial structure may considerably influence the estimation of extinction risk in population viability analyses.},
  comment  = {public},
  doi      = {10.1046/j.1523-1739.2002.99552.x},
  isbn     = {0888-8892},
  pmid     = {7746},
}

Aspects of within-population spatial structure are often neglected in the modeling of population viability. To analyze the relevance of the spatial structure of single populations to population persistence, we compared the results of three models developed for the territorial, arboreal gecko Oedura reticulata., (1) a spatially structured model in which both low and high densities incur mortality costs due to increased movement, (2) a spatially structured model in which the Allee effect is removed, and (3) a spatially unstructured model in which there are no effects of density on mortality. Compared with nonspatial model populations, spatially structured populations exhibited reduced persistence. The Allee effect contributed only a small amount to the reduction in persistence. Increased mortality at high densities caused by difficulties in finding territories markedly reduced persistence in the spatially structured models compared with the density-independent nonspatial model, TV,e argue that the inclusion of elements of spatial structure may considerably influence the estimation of extinction risk in population viability analyses.

@Article{Wiegand2001,
  author   = {Wiegand, Kerstin and Sarre, Stephen D. and Henle, Klaus and Stephan, Thomas and Wissel, Christian and Brandl, Roland},
  title    = {{Demographic stochasticity does not predict persistence of gecko populations}},
  journal  = {Ecological Applications},
  year     = {2001},
  volume   = {11},
  number   = {6},
  pages    = {1738--1749},
  issn     = {10510761},
  url_pdf  = {http://uni-goettingen.de/de/document/download/024c46417717d3b5e40ddca80794768a.PDF/Wiegand_et_al_(2001)_ECOL_APP_Demographic_stochasticity.PDF},
  abstract = {We present a population viability model for an arboreal gecko (Oedura reticulata). This gecko needs a habitat of smooth-barked Eucalyptus woodlands. In Western Australia its distribution has declined dramatically, largely through clearance of woodlands, but populations persist within woodland remnants. Evidence from extensive field data suggests that the gecko was formerly distributed through much of the original eucalypt woodlands, and that geckos show little movement between patches. The populations in all woodland remnants seem to be isolated. We ask whether the present distribution of the gecko across remnants could have been produced solely by the extinction of populations through demographic stochasticity.To test this possibility, we developed a stochastic, individual-based model including environmental stochasticity and estimated the percentage of extinct populations of different size from known field characteristics and the time span since the clearing of the woodland. The model predicted a relationship between remnant size and gecko persistence, driven by demographic stochasticity, that is qualitatively similar to the observed pattern. Despite extensive testing, however, we found that the model predicted an incidence function much too optimistic for the observed distribution of populations in small remnants. This discrepancy between field data and our model is due to a series of implicit assumptions. Thus, our modeling exercise sheds light on the procedures commonly applied to population viability analyses of single populations of endangered species. The implicit assumptions involved in such models make many predictions vague. We suggest that for the study of declining species like O. reticulata it is essential to adequately test extinction models and therefore population viability analyses},
  comment  = {public},
  doi      = {10.1890/1051-0761(2001)011[1738:DSDNPP]2.0.CO;2},
  isbn     = {1051-0761},
  keywords = {Extinction,Gecko,Incidence function,Modeling,Oedura reticulata,Population viability analysis,Western Australian wheatbelt},
}

We present a population viability model for an arboreal gecko (Oedura reticulata). This gecko needs a habitat of smooth-barked Eucalyptus woodlands. In Western Australia its distribution has declined dramatically, largely through clearance of woodlands, but populations persist within woodland remnants. Evidence from extensive field data suggests that the gecko was formerly distributed through much of the original eucalypt woodlands, and that geckos show little movement between patches. The populations in all woodland remnants seem to be isolated. We ask whether the present distribution of the gecko across remnants could have been produced solely by the extinction of populations through demographic stochasticity.To test this possibility, we developed a stochastic, individual-based model including environmental stochasticity and estimated the percentage of extinct populations of different size from known field characteristics and the time span since the clearing of the woodland. The model predicted a relationship between remnant size and gecko persistence, driven by demographic stochasticity, that is qualitatively similar to the observed pattern. Despite extensive testing, however, we found that the model predicted an incidence function much too optimistic for the observed distribution of populations in small remnants. This discrepancy between field data and our model is due to a series of implicit assumptions. Thus, our modeling exercise sheds light on the procedures commonly applied to population viability analyses of single populations of endangered species. The implicit assumptions involved in such models make many predictions vague. We suggest that for the study of declining species like O. reticulata it is essential to adequately test extinction models and therefore population viability analyses

@Article{Becker2000,
  author   = {Becker, Thorsten and Getzin, Stephan},
  title    = {{The fairy circles of Kaokoland (North-West Namibia) - Origin, distribution, and characteristics}},
  journal  = {Basic and Applied Ecology},
  year     = {2000},
  volume   = {1},
  number   = {2},
  pages    = {149--159},
  issn     = {14391791},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ecadde3a02265f535ddce45114c860ca.PDF/Becker_&_Getzin_(2000)_BAS_APP_ECOL%20_The_%20fairy_circles_of_Kaokoland.PDF},
  abstract = {Embedded in species-poor grasslands, fairy circles are circular or sub-circular patches devoid of any vegetation. Characteristically, the circumference of each circle shows a band of more densely packed taller tussocks within a shorter, more sparse grassland matrix. The average diameter of the circles is between 5-8 m. Restricted to sites showing deep sandy deposits, in Namibia, fairy circles occur in a broken belt in the pro-Namib from southern Angola to the Orange River (Republic of South Africa). The distribution of fairy circles is significantly limited to areas with an average of 50-100 mm of annual precipitation. Based on remote sensing methods and expeditions, a map of the distribution area of fairy circles in Kaokoland (NW Namibia) was drawn up. The map indicates that fairy circles are more widely spread over the western parts of Kaokoland than previously reported. The two different active biological hypotheses of the fairy circles' origin comprise 1. the allelopathic interaction between Euphorbia damarana and the contemporary herbaceous vegetation (Theron 1979) and 2. the involvement of harvester termites (Moll 1994). Both hypotheses are discussed and a model about the origin and dynamic of fairy circles is presented. This model includes the foraging behaviour of the harvester termite Hodotermes mossambicus which is the prime causal factor in forming the fairy circles of Kaokoland.},
  comment  = {public},
  doi      = {10.1078/1439-1791-00021},
  isbn     = {14391791},
  keywords = {Harvester termites,Pro-Namib,Sandy deposits,Species-poor ephemeral grassland},
}

Embedded in species-poor grasslands, fairy circles are circular or sub-circular patches devoid of any vegetation. Characteristically, the circumference of each circle shows a band of more densely packed taller tussocks within a shorter, more sparse grassland matrix. The average diameter of the circles is between 5-8 m. Restricted to sites showing deep sandy deposits, in Namibia, fairy circles occur in a broken belt in the pro-Namib from southern Angola to the Orange River (Republic of South Africa). The distribution of fairy circles is significantly limited to areas with an average of 50-100 mm of annual precipitation. Based on remote sensing methods and expeditions, a map of the distribution area of fairy circles in Kaokoland (NW Namibia) was drawn up. The map indicates that fairy circles are more widely spread over the western parts of Kaokoland than previously reported. The two different active biological hypotheses of the fairy circles' origin comprise 1. the allelopathic interaction between Euphorbia damarana and the contemporary herbaceous vegetation (Theron 1979) and 2. the involvement of harvester termites (Moll 1994). Both hypotheses are discussed and a model about the origin and dynamic of fairy circles is presented. This model includes the foraging behaviour of the harvester termite Hodotermes mossambicus which is the prime causal factor in forming the fairy circles of Kaokoland.

@Article{Wiegand2000,
  author   = {Wiegand, Kerstin and Jeltsch, Florian and Ward, David},
  title    = {{Do spatial effects play a role in the spatial distribution of desert-dwelling Acacia raddiana?}},
  journal  = {Journal of Vegetation Science},
  year     = {2000},
  volume   = {11},
  pages    = {473--484},
  issn     = {1100-9233},
  url_pdf  = {http://uni-goettingen.de/de/document/download/da61376641a81fcedb82ddc81847c023.pdf/Wiegand_et_al_(2000)_J_VEG_SCI_spatial_distribution_of_desert_dwelling_Acacia_raddiana.pdf},
  abstract = {We investigated the spatial pattern of A. raddiana in the Negev desert of Israel in order to gain insights into the factors and processes driving the dynamics of this species. Using a scale-dependent measure, the ring statistic, we analysed both patterns observed in the field and time series of spatial tree distributions produced by a simulation model. In the field, random spacing was the predominant pattern observed. However seedlings were clumped on small scales. We ran the model under two contrasting scenarios representing hypotheses that explain the clumping of seedlings and the random distribution of trees. One hypothesis is that there is spatial heterogeneity in seed distribution, germination and seedling mortality, but that these heterogeneities are not correlated with each other in space. The second hypothesis assumes a correlation between these heterogeneities leading to areas suitable for establishment. However, the suitability of the sites is temporally variable. Furthermore, the second hypothesis assumes density-dependent tree mortality due to competition. Both hypotheses lead to spatial distributions that are in qualitative agreement with the patterns observed in the field. Therefore, the classical view that a clumped seedling distribution and a random pattern of older trees is due to clumped regeneration and density-dependent mortality may not hold for Acacia trees in the Negev.},
  comment  = {public},
  doi      = {10.2307/3246577},
  isbn     = {1100-9233},
  keywords = {Acacia raddiana,Negev,point pattern analysis,simulation model,spatio-temporal population dynamics},
  pmid     = {7744},
  url      = {http://dx.doi.org/10.2307/3246577},
}

We investigated the spatial pattern of A. raddiana in the Negev desert of Israel in order to gain insights into the factors and processes driving the dynamics of this species. Using a scale-dependent measure, the ring statistic, we analysed both patterns observed in the field and time series of spatial tree distributions produced by a simulation model. In the field, random spacing was the predominant pattern observed. However seedlings were clumped on small scales. We ran the model under two contrasting scenarios representing hypotheses that explain the clumping of seedlings and the random distribution of trees. One hypothesis is that there is spatial heterogeneity in seed distribution, germination and seedling mortality, but that these heterogeneities are not correlated with each other in space. The second hypothesis assumes a correlation between these heterogeneities leading to areas suitable for establishment. However, the suitability of the sites is temporally variable. Furthermore, the second hypothesis assumes density-dependent tree mortality due to competition. Both hypotheses lead to spatial distributions that are in qualitative agreement with the patterns observed in the field. Therefore, the classical view that a clumped seedling distribution and a random pattern of older trees is due to clumped regeneration and density-dependent mortality may not hold for Acacia trees in the Negev.

@Article{Wiegand2000a,
  author   = {Wiegand, Kerstin and Schmidt, Heike and Jeltsch, Florian and Ward, David},
  title    = {{Linking a spatially-explicit model of acacias to GIS and remotely-sensed data}},
  journal  = {Folia Geobotanica},
  year     = {2000},
  volume   = {35},
  number   = {2},
  pages    = {211--230},
  issn     = {12119520},
  url_pdf  = {http://uni-goettingen.de/de/document/download/7178dbb735f5ad044b1c6b5c9ef56210.pdf/Wiegand_et_al_(2000)_F_GEOBOTANICA_linking_a_spatially_explicit_model_to_GIS.pdf},
  abstract = {Spatially-explicit and landscape-related simulation models are increasingly used in ecology, but are often criticized because their parameterization has high data requirements. A frequently suggested approach to overcome this difficulty is the linkage of spatially-explicit or landscape-related models with GIS (geographic information system) and remote-sensing technology. GIS can provide data on relevant landscape features, such as topography, and satellite images can be used to identify spatial vegetation distribution. In this paper, we use these techniques for simple, cost-inexpensive (in both time and money) parameterization based on readily-available GIS and remotely-sensed data. We use a previously developed, spatially-explicit model of the population dynamics of an Acacia species in the Negev desert of Israel (SAM, spatial Acacia model) to investigate if model initialization (measurement of current tree distribution) can be obtained from readily-available satellite images using a radiometric vegetation index (NDVI, normalized difference vegetation index). Furthermore, we investigate the applicability and the advantages of using an explicit consideration of landscape features in the model based on topographic data from a GIS. Using a DEM (digital elevation model), we compare the wadi topography to the current tree distribution observed in the field. We found that the readily-available GIS and remotely-sensed data are not sufficient to significantly support the parameterization and further development of the model. We conclude that despite the possible benefit of linking spatially-explicit models with other techniques the advantage compared to data sampling in the field is limited by a possible mismatch of scales and the dominant role of stochasticity that may override the relevance of certain spatially-explicit information.},
  comment  = {public},
  doi      = {10.1007/BF02803099},
  isbn     = {1211-9520},
  keywords = {Acacia raddiana,Landscape related models,NDVI,Simulation model,Spatially-explicit,Wadi morphology},
  pmid     = {7745},
}

Spatially-explicit and landscape-related simulation models are increasingly used in ecology, but are often criticized because their parameterization has high data requirements. A frequently suggested approach to overcome this difficulty is the linkage of spatially-explicit or landscape-related models with GIS (geographic information system) and remote-sensing technology. GIS can provide data on relevant landscape features, such as topography, and satellite images can be used to identify spatial vegetation distribution. In this paper, we use these techniques for simple, cost-inexpensive (in both time and money) parameterization based on readily-available GIS and remotely-sensed data. We use a previously developed, spatially-explicit model of the population dynamics of an Acacia species in the Negev desert of Israel (SAM, spatial Acacia model) to investigate if model initialization (measurement of current tree distribution) can be obtained from readily-available satellite images using a radiometric vegetation index (NDVI, normalized difference vegetation index). Furthermore, we investigate the applicability and the advantages of using an explicit consideration of landscape features in the model based on topographic data from a GIS. Using a DEM (digital elevation model), we compare the wadi topography to the current tree distribution observed in the field. We found that the readily-available GIS and remotely-sensed data are not sufficient to significantly support the parameterization and further development of the model. We conclude that despite the possible benefit of linking spatially-explicit models with other techniques the advantage compared to data sampling in the field is limited by a possible mismatch of scales and the dominant role of stochasticity that may override the relevance of certain spatially-explicit information.

@Inproceedings{Wiegand2000b,
  author    = {Wiegand, Kerstin and Ward, David and Thulke, Hans Herman and Jeltsch, Florian},
  title     = {{From snapshot information to long-term population dynamics of Acacias by a simulation model}},
  booktitle = {Plant Ecology},
  year      = {2000},
  volume    = {150},
  number    = {1-2},
  pages     = {97--114},
  url_pdf   = {http://uni-goettingen.de/de/document/download/98638eef225f0c1d146e1511a2ef0afd.PDF/Wiegand_et_al_(2000)_PLANT_ECOL_snap-shot_information_to_long-term_population_dynamics.PDF},
  abstract  = {The African Acacia species A. raddiana is believed to be endangered in the Negev desert of Israel. The ecology of this species is not well understood. The main idea of our study is to learn more about the long-term population dynamics of these trees using snapshot information in the form of size frequency distributions. These distributions are highly condensed indices of population dynamics acting over many years. In this paper, we analyse field data on recruitment, growth, and mortality and use an existing simulation model of the population dynamics of A. raddiana (SAM) to produce contrasting scenarios of these live history processes that are based on the analysed field evidence. The main properties of simulated as well as observed tree size frequency distributions are characterised with Simpson's index of dominance and a new permutation index. Finally, by running the SAM model under the different scenarios, we study the effect of these different processes on simulated size frequency distributions (pattern) and we compare them to size distributions observed in the field, in order to identify the processes acting in the field. Our study confirms rare recruitment events as a major factor shaping tree size frequency distributions and shows that the paucity of recruitment has been a normal feature of A. raddiana in the Negev over many years. Irregular growth, e.g., due to episodic rainfall, showed a moderate influence on size distributions. Finally, the size frequency distributions observed in the Negev reveal the information that, in this harsh environment, mortality of adult A. raddiana is independent of tree size (age).},
  comment   = {public},
  doi       = {10.1023/A:1026574303048},
  isbn      = {13850237},
  issn      = {13850237},
  keywords  = {Acacia raddiana,Individual-based,Negev desert,Pattern and process,Permutation index,Rare recruitment,SAM,Size frequency distributions,Spatially-explicit simulation model},
  pmid      = {8159644288406061092},
}

The African Acacia species A. raddiana is believed to be endangered in the Negev desert of Israel. The ecology of this species is not well understood. The main idea of our study is to learn more about the long-term population dynamics of these trees using snapshot information in the form of size frequency distributions. These distributions are highly condensed indices of population dynamics acting over many years. In this paper, we analyse field data on recruitment, growth, and mortality and use an existing simulation model of the population dynamics of A. raddiana (SAM) to produce contrasting scenarios of these live history processes that are based on the analysed field evidence. The main properties of simulated as well as observed tree size frequency distributions are characterised with Simpson's index of dominance and a new permutation index. Finally, by running the SAM model under the different scenarios, we study the effect of these different processes on simulated size frequency distributions (pattern) and we compare them to size distributions observed in the field, in order to identify the processes acting in the field. Our study confirms rare recruitment events as a major factor shaping tree size frequency distributions and shows that the paucity of recruitment has been a normal feature of A. raddiana in the Negev over many years. Irregular growth, e.g., due to episodic rainfall, showed a moderate influence on size distributions. Finally, the size frequency distributions observed in the Negev reveal the information that, in this harsh environment, mortality of adult A. raddiana is independent of tree size (age).

@Article{Wiegand1999,
  author   = {Wiegand, Kerstin and Jeltsch, Florian and Ward, David},
  title    = {{Analysis of the population dynamics of Acacia trees in the Negev desert, Israel with a spatially-explicit computer simulation model}},
  journal  = {Ecological Modelling},
  year     = {1999},
  volume   = {117},
  number   = {2-3},
  pages    = {203--224},
  issn     = {03043800},
  url_pdf  = {http://uni-goettingen.de/de/document/download/31adaba114dccd2b07beb5b12e235305.PDF/Wiegand_et_al_(1999)_ECOL_MODEL_population_dynamics_of_Acacia_trees.PDF},
  abstract = {Most trees in the Negev desert, Israel, are either Acacia raddiana, A. tortilis or A. negevensis. They provide food and shelter for many desert animals and are a major source of livestock feed and firewood for the native Bedouin people. High mortality and low recruitment of these trees have been reported. To develop sustainable conservation strategies it is necessary to understand the population dynamics of the Acacia trees. Therefore, on the basis of demographic data gained by field studies, a spatially-explicit, individual-based computer simulation model of the population dynamics of A. raddiana has been developed. We evaluate the relative importance of different processes such as seed production and seed infestation by parasites, germination, mortality, and mistletoe infestation to the survival and recruitment of Acacia trees in the Negev. Mortality rates at different life stages, the production of uninfested seeds and the weather regime were most influential. The infection of trees by semi-parasitic mistletoes proved to be of minor importance. The most important result is that an increase in the germination rate of Acacia seeds, such as may result from passage through the digestive tract of large mammalian herbivores, is capable of counteracting the detrimental effect of unfavourable climatic conditions. Consequently, we discuss the use of increased large mammalian herbivore densities as a possible management option for enhancing the survival of Acacia populations in the Negev.},
  comment  = {public},
  doi      = {10.1016/S0304-3800(98)00199-9},
  isbn     = {0304-3800},
  keywords = {Acacia raddiana,Indirect parameter estimation,Individual-based simulation model,Population dynamics,Sensitivity analysis},
  pmid     = {7743},
}

Most trees in the Negev desert, Israel, are either Acacia raddiana, A. tortilis or A. negevensis. They provide food and shelter for many desert animals and are a major source of livestock feed and firewood for the native Bedouin people. High mortality and low recruitment of these trees have been reported. To develop sustainable conservation strategies it is necessary to understand the population dynamics of the Acacia trees. Therefore, on the basis of demographic data gained by field studies, a spatially-explicit, individual-based computer simulation model of the population dynamics of A. raddiana has been developed. We evaluate the relative importance of different processes such as seed production and seed infestation by parasites, germination, mortality, and mistletoe infestation to the survival and recruitment of Acacia trees in the Negev. Mortality rates at different life stages, the production of uninfested seeds and the weather regime were most influential. The infection of trees by semi-parasitic mistletoes proved to be of minor importance. The most important result is that an increase in the germination rate of Acacia seeds, such as may result from passage through the digestive tract of large mammalian herbivores, is capable of counteracting the detrimental effect of unfavourable climatic conditions. Consequently, we discuss the use of increased large mammalian herbivore densities as a possible management option for enhancing the survival of Acacia populations in the Negev.

@Article{Wiegand1997,
  author   = {Wiegand, K. and Jeltsch, F. and Ward, D.},
  journal  = {Verhandlungen der Gesellschaft fur Okologie},
  title    = {{Untersuchungen zur Auswirkung von Strassen auf das Uberleben der Akazien im Negev}},
  year     = {1997},
  issn     = {01711113},
  pages    = {499--506},
  volume   = {28},
  comment  = {public},
  groups   = {Jana:1},
  keywords = {Acacia,Acacia raddiana,Anthropogenic disturbances,Arid,Environmental impact,Ephemeral river,Event-driven system,Herbivores,Israel,Modeling,Negev,Negev Desert,Population dynamics,Road,Simulation model,Tree},
}

@Article{Wiegand1996,
  author   = {Wiegand, K. and Brandl, R. and Henle, K. and Sarre, S. and Stephan, T. and Wissel, C.},
  journal  = {Verhandlungen der Gesellschaft fuer Oekologie},
  title    = {{Extinctions in habitat remnants: lessons from a specialised gecko species}},
  year     = {1996},
  pages    = {489--494},
  volume   = {26},
  abstract = {Oedura reticulata - O. reticulata may survive even in very small patches, and stochastic extinction with recolonisation is NOT the reason for its persistence - the model produced over-predicted the occurrence of O. reticulata for several reasons - basically, some of the assumptions were overly simplistic (assuemd constant habitat quality, limited env. variability, didn't consider edge effects)},
  comment  = {public},
  groups   = {Jana:1},
  keywords = {fragmentation,spatial ecology, fragmentation},
}

Oedura reticulata - O. reticulata may survive even in very small patches, and stochastic extinction with recolonisation is NOT the reason for its persistence - the model produced over-predicted the occurrence of O. reticulata for several reasons - basically, some of the assumptions were overly simplistic (assuemd constant habitat quality, limited env. variability, didn't consider edge effects)