Spatiotemporal decoupling of CO₂ and warming effects in arid grasslands: Grazing-mediated vulnerabilities in Central Asia (2005–2050)

Abstract

Drylands, covering 40 % of the global terrestrial surface, play a critical role in carbon sequestration and ecological security but face escalating pressures from climate change and anthropogenic activities. Central Asia (CAS), a temperate dryland hotspot, is experiencing rapid warming, altered precipitation patterns, and intensifying grazing pressure, yet the combined impacts of these drivers on grassland carbon dynamics remain poorly quantified. Using an enhanced Arid Ecosystem Model (AEM) integrated with a dynamic grazing module, this study investigated the spatiotemporal responses of net primary productivity (NPP) in CAS grasslands to future climate scenarios (RCP4.5 and RCP8.5) and grazing intensification from 2005 to 2050. Our simulations revealed that regional NPP increased by 11 % (RCP4.5) and 14 % (RCP8.5), driven primarily by CO₂ fertilization (contributing 9–13 %) and precipitation variability. However, warming exhibited spatially heterogeneous effects, exacerbating NPP declines in arid lowlands while enhancing productivity in high-altitude meadows. Grazing reduced NPP by 26–34 %, with interactive effects between climatic and anthropogenic factors amplifying uncertainties. Notably, precipitation dominated interannual NPP variability (R = 0.64–0.65, p < 0.01), whereas temperature exhibited weak correlations (R = 0.10–0.20, p > 0.05). These findings underscore the vulnerability of CAS grasslands to compounded climatic and grazing pressures, emphasizing the need for adaptive management strategies to balance ecological resilience and pastoral livelihoods under global change.