Yue et al.zip

It has been widely reported that appropriate grazing can promotes grassland biodiversity and productivity, thereby ensuring rangeland sustainability. Yet, experimental testing of the grazing advantage is still rare, especially considering how little we know about the underlying mechanisms. We hypothesized that appropriate grazing can promote biomass production in a plant community through increasing resource acquisition and/or utilization by extending functional trait space of the plant community.To test this hypothesis, we conducted a grazing experiment (i.e., control = no grazing, light, moderate, and heavy grazing) in Tibetan alpine meadows. We measured 13 functional traits in each plot for each of the 22 species commonly occurred in all plots to quantify the functional trait space of the plant community, and to identify which species positively (i.e., grazing increasers), negatively (i.e., decreasers), or insignificantly (i.e., generalists) responds to grazing in term of changes in species relative abundance.Comparing to control, the biomass production was significantly increased in all three grazed treatments, while the moderate and heavy grazing also significantly increased functional trait space of the plant community. Across plots, the increase in biomass production was significantly associated with the extension of functional trait space. The grazing-induced extensions of trait space were likely attributed to an increase leaf trait variation of composing species to enhance photosynthesis, especially on sedges and legumes and for grazers increasers and generalists.The study not only provides robust evidence for the advantage of appropriate grazing, but it also provides the first evidence to unveil a mechanistic linkage from trait variation and species performance to community functional space and productivity in response to grazing. Hence the study offers a new insight into understanding the functional space mediated linkages from grazing-induced plant response upon dynamics of grassland function.