Multiple global changes drive grassland productivity and stability: A meta‐analysis

Abstract Temporal stability of primary productivity is the key to stable provisioning of ecosystem services to human beings. Yet, the effects of various global changes on grassland stability remain ambiguous. Here, we conducted a comprehensive meta‐analysis based on 1070 multi‐year paired observations from 173 studies, to examine the impacts of various global changes on productivity, community stability and plant diversity of grasslands on a global scale. The global change drivers include nitrogen (N) addition, phosphorus (P) addition, N and P addition, precipitation increase, precipitation decrease, elevated CO 2 and warming. Global change drivers generally had stronger impacts on grassland productivity than on temporal stability, except for precipitation changes. Community temporal stability was reduced by N addition, N and P addition and precipitation decrease, but was increased by precipitation increase and remained unchanged under P addition, elevated CO 2 and warming. In addition, species richness decreased under N addition, N and P addition and precipitation decrease. At the plant functional group level, N and P addition reduced grasses' stability and precipitation increase enhanced forbs' stability. Nutrient additions decreased community stability via increasing the inter‐annual variation more than the mean of primary productivity, while precipitation changes mainly affected community temporal stability via changing mean productivity. The negative impacts of global change drivers (i.e. N and P addition, warming) on community temporal stability increased with the degree of species loss but decreased with increasing stability of grasses. Moreover, the negative impacts of nutrient addition and precipitation decrease on community stability was lessened while the positive effect of precipitation increase on community stability was enhanced in grasslands with higher historical precipitation variability, greater soil fertility and longer experimental duration. Synthesis . Our findings demonstrate that N‐based nutrient additions and drought destabilise grassland productivity, while precipitation increase enhances community stability. Impacts of global changes on community productivity and stability are mediated by species richness, plant functional group, site‐specific environmental conditions (i.e. climate, soil) and experimental duration, which deserve more attention in grassland management practices under future global change scenarios.