Grazing intensity alters soil microbial diversity and network complexity in alpine meadow on the Qinghai-Tibet Plateau

Livestock grazing can alter biodiversity and ecosystem functions. However, how long-term and continuous grazing intensity affect belowground biodiversity remains unclear, especially for soil microbial diversity. Here, through a well-controlled 5-year field experiment in a Tibetan alpine meadow, the responses of soil bacterial and fungal communities to yak grazing intensity were examined. Our results showed that grazing intensity signifi-cantly changed soil bacterial and fungal community compositions, rather than microbial alpha-diversity. The co-occurrence network analysis indicated that both soil bacterial and fungal network complexity gradually decreased with increasing grazing intensities. Meanwhile, soil C/N ratio, soil moisture, dissolved organic ni-trogen (DON), NH4+-N, and aboveground biomass (AGB) were related to soil bacterial community, and AGB, NO3-- N, NH4+-N, and DON and were associated with soil fungal community. Taken together, our manipulative experiment provides empirical evidence that grazing intensity-induced alterations of aboveground vegetation and nitrogen availability primarily trigger the shift of soil microbial community and structure. These results can support grassland management and ecological restoration in alpine ecosystems.