Diversity and growth-promoting characteristics of rhizosphere bacteria of three naturally growing plants at the sand iron ore restoration area in Qinghe County

It is a great challenge to restore northern mines after mining and achieve optimal results due to the extremely harsh environment and climate, as in Qinghe County of Xinjiang Province, China. Qinghe County has a climate of drought, cold, strong winds, and high altitude. After sand and iron mining, the soil in this area contains a large amount of sand and gravel with extremely low organic matter, nitrogen deficiency, and a high pH of 9.26. Our preliminary studies disclosed that only three plants, including Caligonum junceum, Atraphaxis virgata, and Melilotus albus Medic, can grow naturally in this environment without any artificial management. For effective ecology restoration, this study explored the mechanism of plant-microbial interaction and stress resistance in this environment. It was found that although the soil condition in the sand iron ore landfill area is extreme, the bacterial diversity remained high, with Shannon and Simpson indices reaching 9.135 and 0.994, respectively. The planting of three types of remediation plants did not significantly improve, or even decreased, the soil bacterial diversity index, but greatly changed the composition of dominant bacterial genera. Significant differences in the composition of rhizosphere soil bacterial communities among these three remediation plants were observed. Potential new bacterial species accounted for 9.8 %, and the proportion of unique genera reached 30 % or 50 %, respectively. Among all the isolated strains, 74 % had nitrogen fixation and other growth-promoting properties. In summary, the soil microbial community structure in this extreme environment is unique and diverse. The types of remediation plants play a major role in the composition of the rhizosphere bacterial community structure, and the recruited growth-promoting bacteria are diverse and functional. This study may offer valuable information for further studies in vegetation restoration and aid in ecology restoration, especially under extreme conditions.