Characteristics and driving forces of the soil microbial community during 35 years of natural restoration in abandoned areas of the Daxin manganese mine, China.

The restoration of mining wastelands, particularly in karst regions contaminated by heavy metals, is an environmental challenge in need of urgent attention. Soil microbes play a vital role in nutrient cycling and ecosystem recovery, yet the long-term evolution of soil microbial communities in such settings remains poorly understood. This study explored the dynamics and influencing factors of soil microbial communities during 35 years of natural restoration in abandoned manganese (Mn) mine areas in Guangxi Province, China. The results revealed that the concentrations of Mn, Cd, Zn, and Cu were significantly (p < 0.05) reduced by 80.4-85.3%, 55.3-70.0%, 21.0-38.1%, and 29.4-49.4%, respectively, in the mid-late restoration periods (R19 and R35) compared with R1. The α diversities of the bacterial and fungal communities significantly increased in the middle-late restoration periods (R19 and R35), indicating increased microbial diversity as restoration progressed. The bacterial community structure exhibited more pronounced changes than did the fungal community structure, with significant shifts observed in dominant phyla such as Proteobacteria, Actinobacteria, Acidobacteriota, and Ascomycota. Notably, the relative abundances of Rhizobiales, Burkholderiales, and Hypocreales increased gradually with succession. Co-occurrence network analysis revealed that bacterial interactions became stronger over time, whereas interactions between bacteria and fungi weakened. Mantel tests and partial least squares path modeling (PLS‒PM) identified soil pH, heavy metals (Mn, Cd, Zn, and Cu), and nutrients (SOM and TN) as key drivers shaping the microbial community composition. These factors were more strongly correlated with bacterial communities than with fungal communities, underscoring the different responses of microbial groups to environmental changes during natural restoration. These findings enhance our understanding of the ecological processes governing microbial community succession in heavy metal-contaminated soils undergoing natural restoration.