Interactive Effects Of Grazing And Global Change Factors On Soil And Ecosystem Respiration In Grassland Ecosystems: A Global Synthesis

As the key carbon (C) fluxes between biosphere and atmosphere, soil respiration (R-s) and ecosystem respiration (R-e) play vital roles in regulating global C balance and climate-biosphere feedback in the Earth system. Despite the fact that numerous manipulative studies and a few meta-analyses have been conducted to examine the responses of R-s and its components (i.e. autotrophic [R-a] and heterotrophic respiration [R-h]) as well as R-e to grazing (G) or global change factors, the interactive effects between grazing and global change factors remain poorly understood. Here, we performed a comprehensive meta-analysis of manipulative experiments with both grazing and global change factors to quantify their individual and interactive effects on R-s and its components as well as R-e. Our results showed that grazing and drought significantly decreased R-s by 12.35% and 20.95%, respectively, whereas warming (W), nitrogen addition (N) and increased precipitation (P) stimulated it by 2.12%, 5.49% and 13.44%, respectively. Similarly, grazing, warming, nitrogen addition and increased precipitation increased R-e by 7.21%, 4.94%, 48.45% and 21.57%, respectively, while drought decreased it by 16.86%. However, the combinations of grazing with warming (GW), nitrogen addition (GN) and increased precipitation (GP) exhibited non-significant effects on R-s. More importantly, additive interactions between grazing and global change factors exhibited a substantial predominance on R-s, R-a, R-h and R-e rather than synergistic and antagonistic ones. Synthesis and applications. Our findings highlight the crucial importance of the interactive effects between grazing and global change factors on soil respiration (R-s) and ecosystem respiration (R-e). Therefore, incorporating this key influence on ecosystem processes into Earth system models (ESMs) could better improve the prediction of climate-biosphere feedbacks and develop sustainable strategies for grassland management in the Anthropocene.