Microbial community in the Leymus chinensis rhizosphere associates with its high production in mild saline-alkaline grassland

Leymus chinensis is a dominant grass widely distributed in Central Asia, in both saline-alkaline and non-saline-alkaline grasslands. However, the mechanisms underlying its saline-alkaline tolerance have not been explored from the perspective of rhizosphere microbial communities. We investigated L. chinensis rhizosphere microbial communities in both saline-alkaline and non-saline-alkaline grasslands. It was found that the biomass of L. chinensis was remarkably higher in saline-alkaline than in non-saline-alkaline habitat and that changes in the rhizosphere bacterial and arbuscular mycorrhizal fungi (AMF) communities had a greater effect on biomass than climate, soil moisture, nutrients, and salinity. We demonstrated that the bacteria and AMF in the rhizosphere of L. chinensis grown in saline-alkaline grassland differed from those in non-saline-alkaline grassland, and the differences were associated with soil salinity or alkalinity. The co-occurrence networks of bacteria and AMF and bacteria-AMF interaction networks in rhizosphere were complex and connected, with more nodes and edges and a higher average degree of nodes and modularity in the saline-alkaline grassland. More complex networks promoted plant tolerance and growth under salt-alkali stress. High number of microbial keystone taxa was related to the nutrient concentration in the soil and L. chinensis leaves, and more remarkable direct effects of the bacterial and AMF keystone communities on plant nutrient concentrations were demonstrated in saline-alkaline grassland. This indicates that bacterial and AMF communities in saline-alkaline grasslands are favorable for plant growth and nutrient uptake. This study provides an accurate and beneficial source of soil microbial assemblages for future plant-microbial joint remediation of the saline-alkaline ecosystems.