Soil microbial community assembly drives ecosystem multifunctionality under grazing disturbance by regulating diversity and network structure

In the context of global climate change, overgrazing has impacted ecosystem multifunctionality (EMF). However, the influence of different characteristics of microbial communities on EMF under grazing pressures remains unclear. In this study, we examined how microbial community diversity, co-occurrence network structure, and assembly processes influence ecosystem function and multifunctionality under three grazing pressures: light grazing, heavy grazing, and grazing exclusion. Our results show that light grazing significantly increased microbial community diversity, richness, network complexity, and stability compared to heavy grazing. Soil bacterial and fungal communities were predominantly shaped by stochastic processes. As grazing pressure increased, the proportion of deterministic processes in both bacterial and fungal communities also grew. Furthermore, light grazing significantly reduced both ecosystem functions and multifunctionality compared to heavy grazing. We observed that microbial community assembly processes under grazing disturbance can directly or indirectly regulate EMF by shaping community diversity and network structure. The relationship with EMF appears to depend more on diversity than on network structure. Moreover, we emphasize that the complexity and stability of community networks are stronger predictors of EMF changes than diversity alone. In conclusion, the protection and careful management of microbial communities are crucial for enhancing ecosystem resilience and supporting sustainable development.