Simulated livestock defoliation enhances plant diversity and productivity in China’s grasslands: A meta-analysis

Abstract Livestock grazing can alter plant productivity and diversity through defoliation, trampling and excretion. To isolate effects of defoliation, researchers commonly employ clipping experiments, although these effects of defoliation can vary considerably depending on the intensity and duration of grazing, as well as the type of ecosystem. Here, we compiled data from 1006 pairs of observations across 96 studies to assess the impacts of simulated livestock defoliation on various measures of plant diversity (including evenness) and productivity in China’s grasslands. Overall, simulated livestock defoliation resulted in greater species richness and evenness, along with elevated aboveground net primary productivity (ANPP) and belowground biomass (BGB), but lower aboveground biomass (AGB). Moderate levels of defoliation produced a stronger positive response in diversity compared to light or heavy defoliation, similar to later-season defoliation. Such effects were absent in alpine meadows, which leading to a negative association between responses of diversity and elevation. AGB was reduced by defoliation in all contexts, while BGB increased more when defoliation was light, later in the season, and with shorter experimental durations; these effects were stronger in drier areas. Simulated grazing’s effects on ANPP switched from positive to negative as intensity increased. Changes in diversity were positively correlated with changes in ANPP in response to defoliation. These findings highlight that the effects of defoliation are context-specific in China’s grasslands, with important implications for grassland management and conservation.