TY - JOUR A1 - Marquart, Arnim A1 - Eldridge, David J. A1 - Geissler, Katja A1 - Lobas, Christoph A1 - Blaum, Niels T1 - Interconnected effects of shrubs, invertebrate-derived macropores and soil texture on water infiltration in a semi-arid savanna rangeland JF - Land degradation & development N2 - Many semi arid savannas are prone to degradation, caused for example, by overgrazing or extreme climatic events, which often lead to shrub encroachment. Overgrazing by livestock affects vegetation and infiltration processes by directly altering plant composition (selective grazing) or by impacting soil physical properties (trampling). Water infiltration is controlled by several parameters, such as macropores (created by soil-burrowing animals or plant roots) and soil texture, but their effects have mostly been studied in isolation. Here we report on a study, in which we conducted infiltration experiments to analyze the interconnected effects of invertebrate-created macropores, shrubs and soil texture (sandy soil and loamy sand) on infiltration in two Namibian rangelands. Using structural equation modeling, we found a direct positive effect of shrub size on infiltration and indirectly via invertebrate macropores on both soil types. On loamy sands this effect was even stronger, but additionally, invertebrate-created macropores became relevant as a direct driver of infiltration. Our results provide new insights into the effects of vegetation and invertebrates on infiltration under different soil textures. Pastoralists should use management strategies that maintain a heterogeneous plant community that supports soil fauna to sustain healthy soil water dynamics, particularly on soils with higher loam content. Understanding the fundamental functioning of soil water dynamics in drylands is critical because these ecosystems are water-limited and support the livelihoods of many cultures worldwide. KW - hydrology KW - infiltration KW - invertebrate macropores KW - shrub-encroachment KW - soil function KW - soil texture Y1 - 2020 U6 - https://doi.org/10.1002/ldr.3598 SN - 1085-3278 SN - 1099-145X VL - 31 IS - 16 SP - 2307 EP - 2318 PB - Wiley CY - Chichester, Sussex ER - TY - JOUR A1 - Reinhard, Johanna E. A1 - Geissler, Katja A1 - Blaum, Niels T1 - Short-term responses of darkling beetles (Coleoptera:Tenebrionidae) to the effects of fire and grazing in savannah rangeland JF - Insect Conservation and Diversity N2 - Fire and grazing shape biodiversity in savannah landscapes. In land use management, knowing the effects of fire and grazing on biodiversity are important in order to ensure environmental sustainability. Beetles specifically are indicators of the biodiversity response to fire and grazing. A grazing exclusion and burning experiment in a split-plot design was used in order to investigate the interacting effects of fire and wildlife grazing on biomass, diversity, and species composition of darkling beetles (Coleoptera, Tenebrionidae) over time after fire. Darkling beetle species richness and diversity were responding in a three-way-interaction to fire, grazing, and time after fire, whereby biomass of darkling beetles remained unaffected and species compositional changes were attributed to seasonal changes of time only. Fire on ungrazed plots had a negative effect on species diversity and richness 2 weeks and 6 months post fire, whereas fire on grazed plots had no impact on species diversity and richness. Grazing only lowered species diversity and richness 6 months after fire treatments. Results suggest that grazing overrides the effects of fire and that the similar effects caused by fire and grazing are due to niche and assemblage simplification of the habitat. KW - Arid ecosystems KW - arid rangeland KW - beetles KW - herbivory KW - insect diversity KW - land use KW - management Y1 - 2018 U6 - https://doi.org/10.1111/icad.12324 SN - 1752-458X SN - 1752-4598 VL - 12 IS - 1 SP - 39 EP - 48 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Hering, Robert A1 - Hauptfleisch, Morgan A1 - Geissler, Katja A1 - Marquart, Arnim A1 - Schoenen, Maria A1 - Blaum, Niels T1 - Shrub encroachment is not always land degradation BT - Insights from ground‐dwelling beetle species niches along a shrub cover gradient in a semi‐arid Namibian savanna JF - Land degradation & development N2 - Shrub encroachment in semi-arid savannas is induced by interacting effects of climate, fire suppression, and unsustainable livestock farming; it carries a severe risk of land degradation and strongly influences natural communities that provide key ecosystem functions. However, species-specific effects of shrub cover on many animal groups that act as indicators of degradation remain largely unknown. We analysed the consequences of shrub encroachment for ground-dwelling beetles in a semi-arid Namibian savanna rangeland, where beetles and vegetation were recorded along a shrub cover gradient (30%). Focusing on species niche breadths and optima, we identified two crucial shrub cover thresholds (2.9% and 10.0%), corresponding to major changes in the beetle communities with implications for savanna ecosystem functioning. Niche optima of most species were between the first and second thresholds; beyond the second threshold, saprophagous, coprophagous, and rare predatory beetles declined in numbers and diversity. This is problematic because beetles provide important ecosystem functions, such as decomposition and nutrient cycling. However, we also found that certain species were adapted to high shrub cover, thus providing examples of niche differentiation. Despite the predominantly negative effects of heavy shrub encroachment on beetle communities, shrubs in their early life stages apparently provide essential structures, which enhance habitat quality for ground-dwelling beetles. Our results demonstrate that shrub encroachment can have mixed effects on ground-dwelling beetle communities and hence on savanna ecosystem functioning. We, therefore, conclude that rangeland management and restoration should consider the complex trade-offs between species-specific effects and the level of encroachment for sustainable land use. KW - Coleoptera KW - rangeland KW - semi-arid savanna KW - shrub encroachment KW - species niche KW - threshold Y1 - 2018 U6 - https://doi.org/10.1002/ldr.3197 SN - 1085-3278 SN - 1099-145X VL - 30 IS - 1 SP - 14 EP - 24 PB - Wiley CY - Chichester ER - TY - JOUR A1 - Lohmann, Dirk A1 - Falk, Thomas A1 - Geissler, Katja A1 - Blaum, Niels A1 - Jeltsch, Florian T1 - Determinants of semi-arid rangeland management in a land reform setting in Namibia JF - Journal of arid environments N2 - To assess the ecological and economic implications of the redistributive land reform in semi-arid Namibia, we investigated to what extent land reform beneficiaries adjust herd size and herd composition according to environmental (rainfall, vegetation) and economic variables (herd size, financial assets, running costs). We performed model-based role-plays with Namibian land reform beneficiaries, simulating 10 years of rangeland management. Our study revealed that the farmers surveyed mainly manage their herds according to their economic situation (herd size and account balance) but do not take environmental variability (rainfall and vegetation) into account. Further, our results indicate that, due to financial pressure, farmers are not able to apply their desired management strategies, and that owners of small farms face a higher risk of economic failure. However, farmers apply rather conservative and constant stocking rates and will thus, given the current economic limitations, likely not contribute to semi-arid savanna degradation. We conclude that land reform beneficiaries need support to be able to apply straightforward and efficient management strategies. This could be achieved by facilitating cooperation between small farming businesses and by supporting initial investment in productive cattle herds at the time of redistribution of the land. KW - Dry land degradation KW - Semi-arid savanna KW - Land reform KW - Rangeland management KW - Simulation model KW - Role-play Y1 - 2014 U6 - https://doi.org/10.1016/j.jaridenv.2013.10.005 SN - 0140-1963 SN - 1095-922X VL - 100 SP - 23 EP - 30 PB - Elsevier CY - London ER - TY - JOUR A1 - Jeltsch, Florian A1 - Blaum, Niels A1 - Brose, Ulrich A1 - Chipperfield, Joseph D. A1 - Clough, Yann A1 - Farwig, Nina A1 - Geissler, Katja A1 - Graham, Catherine H. A1 - Grimm, Volker A1 - Hickler, Thomas A1 - Huth, Andreas A1 - May, Felix A1 - Meyer, Katrin M. A1 - Pagel, Jörn A1 - Reineking, Björn A1 - Rillig, Matthias C. A1 - Shea, Katriona A1 - Schurr, Frank Martin A1 - Schroeder, Boris A1 - Tielbörger, Katja A1 - Weiss, Lina A1 - Wiegand, Kerstin A1 - Wiegand, Thorsten A1 - Wirth, Christian A1 - Zurell, Damaris T1 - How can we bring together empiricists and modellers in functional biodiversity research? JF - Basic and applied ecology : Journal of the Gesellschaft für Ökologie N2 - 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. KW - Biodiversity theory KW - Biodiversity experiments KW - Conservation management KW - Decision-making KW - Ecosystem functions and services KW - Forecasting KW - Functional traits KW - Global change KW - Monitoring programmes KW - Interdisciplinarity Y1 - 2013 U6 - https://doi.org/10.1016/j.baae.2013.01.001 SN - 1439-1791 VL - 14 IS - 2 SP - 93 EP - 101 PB - Elsevier CY - Jena ER -