The phyllosphere microbiota greatly affects ecosystem carbon and nitrogen cycles, plant productivity and stress tolerance. However, the microbial composition and underlying mechanisms in alpine grasslands of the Qinghai-Tibetan Plateau (QTP) remain unclear. Here, geographic patterns in the abundance, diversity and community composition of phyllosphere microbiota and their functions were explored. We found that both phyllosphere bacterial and fungal community composition displayed a geographical dependence. Climate, especially mean annual precipitation (MAP), played important role in shaping phyllosphere microbial communities over broad geographic scales. The MAP explained 4%-34% of the variation in the phyllosphere microbial community. A distinctive feature of the QTP phyllosphere microbiota was the prevalence of positive correlations in microbial co-occurrence networks, contrasting with patterns observed in other ecosystems. Further analysis revealed that ecosystem multifunctionality was strongly associated with microbial abundance and interspecies interactions, with bacterial communities exerting a disproportionately large influence compared to fungi. These findings provide a solid understanding of patterns and drivers of phyllosphere microbial community and function across alpine grasslands on the QTP, which offer new perspectives for sustainable alpine grassland management. Traditional grassland restoration practices often prioritize target species selection, overlooking the critical role of root networks. This study, conducted across a grazing-exclusion chronosequence in semi-arid grasslands, reveals that the regulatory effect of plant community root traits on soil carbon and nitrogen accumulation significantly surpasses that of target species. This conclusion provides a scientific basis for optimizing restoration strategies and enhancing ecological functions in arid and semi-arid grasslands. (sic)(sic): (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic):1)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)4%-34%(sic)(sic)(sic)(sic)(sic).2)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).3)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).