Plant diversity enhances soil fungal network stability indirectly through the increase of soil carbon and fungal keystone taxa richness.

Plant diversity is critical to the stability of ecosystems. However, our knowledge about the plant diversity effect on the stability of belowground communities is limited. Here, we characterized soil fungal diversity and co-occurrence network across a plant diversity gradient in a diversity manipulation experiment. We found that higher plant diversity resulted in higher fungal diversity, network complexity and stability. The positive plant diversity effect on fungal network stability was indirect via the increase of soil carbon and fungal keystone taxa richness based on structural equation modeling analysis. The model explained 44% variations of network stability when combining soil carbon and fungal keystone taxa richness, but explained approximate 30% variations of network stability when considering either one of the two factors, indicating that environmental filtering and biotic interaction processes play comparable roles in mediating the plant diversity effect on soil fungal network stability. The plant diversity-induced fungal network stability was significantly correlated with community-level functions including community resistance and enzyme activities. This study, from the view of networks, provides new insights into the plant diversity effect on the stability of soil microbial communities, which have implications for biodiversity conservation and policy development.