On the early warning signal of degradation in drylands: Patches or plants?

作者：Gastón R. Oñatibia, Martı́n R. Aguiar · 发表于：Journal of Ecology · 年份：2022 · DOI：10.1111/1365-2745.14034 · 被引用次数：13 · 研究领域：Ecosystem dynamics and resilience、Ecology and Vegetation Dynamics Studies、Animal Ecology and Behavior Studies

Abstract Global drylands are threatened by grazing pressure intensification and climate change, which act as major drivers of land degradation. Detecting this process at an early stage is essential for predicting losses of ecological functions and for restoration management. Vegetation patch‐size distribution is an indicator of dryland multifunctionality and has been proposed as a warning signal for the onset of degradation processes. However, we proposed and tested a general model that stresses that patchiness may fail to detect degradation of the forage provision, depending on plant community species composition. This is a key aspect since forage provision is strongly associated with human well‐being in drylands. We hypothesized that grazing‐induced changes in patchiness and forage provision converge in drylands dominated by forage species but are decoupled in those dominated or co‐dominated by non‐forage species. We tested the conceptual model in a unique regional‐scale gradient with strong ecological differences but a common biogeographical and human impact history to reduce local contingencies effects. We compared datasets of grazing intensification impacts on (i) plant cover and patch‐size distribution and (ii) plant density and plant‐size distribution of dominant forage grasses (a proxy of forage provisioning). We showed that there is a decoupling between grazing‐induced changes in vegetation patchiness and forage provisioning, particularly in drylands where non‐forage...