Functional trait reorganization buffers the negative effects of grazing on plant species turnover in alpine grasslands

Livestock grazing is the most pervasive biological filter in global grasslands and is central to local livelihoods. A trait-based perspective is crucial for understanding plant strategies and species turnover under grazing pressure, yet current theories struggle to reconcile species turnover with often weak changes in functional diversity. Moreover, little attention has been given to the distinct filtering roles of different herbivores and their influence on trait coordination. We conducted a controlled grazing experiment in the alpine meadows of the northeastern Qinghai–Tibetan Plateau, in which moderate grazing with yaks, Tibetan sheep, and their combination was applied. We assessed how these grazing assemblages shaped community-weighted mean traits (CWMs), functional trait networks, and functional diversity and how such changes mediated species turnover. Livestock types exerted contrasting filtering effects on the CWMs. Grazing consistently reduced reproductive branch height, with the smallest decrease occurring under yak–sheep mixed grazing. Sheep alone and sheep-dominated grazing resulted in the greatest increase in vegetative and reproductive branch weights, revealing adaptive strategies that coupled reduced stature with compensatory biomass allocation. Grazing also reshaped trait networks, enhancing integration and coordination while leaving functional richness largely unchanged. Structural equation modeling revealed that grazing strongly negatively affected species turnover, which was partly offset by grazing-induced shifts in CWMs. Our findings establish a multilevel framework that links traits, diversity, networks, and species turnover under grazing. We show that plant communities respond primarily through trait coordination and CWM restructuring rather than functional diversity loss, offering new insights for biodiversity conservation and sustainable management of alpine grasslands. • Livestock types differentially shape plant CWMs in alpine grasslands. • Grazing reorganizes trait networks, enhancing coordination, not richness. • Functional trait shifts buffer negative grazing effects on species replacement.