Response of soil environment factors and microbial communities to phytoremediation with Robinia pseudoacacia in an open-cut magnesite mine

Overexploitation of magnesium has caused serious environmental pollution, and the ecological restoration of magnesite mines has attracted increasing attention in China. The aim of this study was to assess the effects of phytoremediation with Robinia pseudoacacia (RP) on soil quality and microbial communities in magnesite mines. Here, soil samples were collected from restored areas (R. pseudoacacia), natural forest (NF), and unrestored areas (CK), and the soil microbial communities were assessed by Illumina high-throughput sequencing. Phytoremediation with R. pseudoacacia could alleviate soil alkalization and contribute to the accumulation of soil nutrients. A total of 531,329 effective 16S rRNA and 596,344 valid Internal Transcribed Spacer rRNA gene sequences were obtained, which were classified into 30 bacterial and 12 fungal phyla. The predominant bacterial and fungal phyla were Proteobacteria and Ascomycota, respectively. Bacterial diversity indices of RP were higher than those of the CK, both of which were lower than those in the NF site. While, fungal Chao1 and ACE (abundance-based coverage estimator) indices of RP were higher than those of the CK and even surpassed those in the NF site. Soil microbial communities significantly differed among different treatments, and the effects of soil factors on microbial communities were comprehensive and not determined by a single factor. Generally, these results indicated that phytoremediation with R. pseudoacacia could effectively improve the soil environment of the abandoned magnesium mine, which provide useful insights and practical references for the suitable species that would be planted on magnesite mine for restoration.