Arbuscular mycorrhizal fungi serve as keystone taxa for revegetation on the Tibetan Plateau.

Revegetation is widely used to enhance degraded topsoil recovery with the enhancements of soil nutrient accumulation and soil structure stabilization. Arbuscular mycorrhizal fungi (AMF) are important for the allocation of carbon into the soil and the formation of soil aggregates. Thus, we hypothesized that AMF could construct more niches for other microbes during revegetation, making AMF keystone taxa of soil. Soil fungal and bacterial communities were investigated under a revegetation experiment and correlation networks between soil fungi and bacteria were constructed. Simultaneously, the plant growth level, soil properties and structure, and soil microbial carbon decomposition abilities were measured. The results revealed that AMF were the most central fungi at the phylum (degree = 3), class (degree = 11), and family (degree = 15) levels. The reads number of AMF were positively correlated with both fungal (R2  = 0.431, P < 0.001) and bacterial (R2  = 0.106, P = 0.044) richness. Higher colonization of AMF in roots and/or more AMF extraradical mycelium and spores in soil indicated a better plant growth, more stable soil aggregates, and a higher carbon decomposition ratio. Our results highlight that AMF are keystone taxa in revegetation, as they play significant roles in enhancing the recovery of the belowground microbiome diversity, soil structure stability, and nutrients cycling. The positive roles of AMF in revegetation support the application of AMF in ecosystem recovery.