Revegetation significantly increased the bacterial-fungal interactions in different successional stages of alpine grasslands on the Qinghai-Tibetan Plateau

Numerous restoration measures have been implemented to rebuild degraded alpine grasslands on the Qinghai-Tibetan Plateau, one of the most fragile regions in the world. Understanding the responses of soil microbes to restoration activities is critical to predict restoration direction and trajectories, as soil microbes play a key role in ecosystem functioning and nutrients cycling. In this study, we identified the effects of revegetation on soil microbial community composition and diversity, and the interaction between bacterial and fungal taxa in different successional stages (early stage, middle stage, late stage) by using a severely degraded grassland as the baseline, and healthy grassland as the target. Our results show that the composition of bacteria at phylum level and fungi at class level were significantly changed between successional stages. The diversity of bacteria at OTU level was significantly decreased, while the diversity of fungal OTUs were not significantly changed with successional stages. Plant and soil properties explained 53.15% variation of bacterial structure and 46.16% variation of fungal structure. Plant community, soil organic carbon, total nitrogen, and soil pH mainly influence microbial community during recovery process. Bacteria towards more copiotrophic and functional groups of bacteria and fungi were more similar to healthy grassland along successional stage due to plant and soil restoration. Total links and negative links of bacteria-fungi interaction networks increased along successional stages of revegetated grasslands. Keystone species in each network also changed with successional stages. These findings verified that revegetation could be effective to restore the microbial community of severely degraded grassland on the Qinghai-Tibetan Plateau.