Impacts of restoration mode on soil physicochemical properties and microbial community structure in an open-pit mining area

Objective Open-pit mining has seriously damaged soil structure and regional ecosystem health. It is imperative to recognize the pivotal role of soil in the process of ecological restoration in the context of reforestation following open-pit mining. It has therefore become imperative to recognize the effects of different restoration modes on the physicochemical properties and microbial community structure of soil which is important for exploring the ecological restoration measures of mining areas and evaluating the effectiveness of these measures. Methods In this study, we investigated the effects of three restoration methods (bare mining area, artificial restoration, and natural restoration) on the soils of abandoned open-pit mining area in Hangzhou, Zhejiang Province. The impacts of different restoration methods on soil physicochemical properties and soil microbial community structure were investigated through the investigation of the soil physicochemical properties, the soil enzyme activities, and the structure of the soil microbial community. Results The results showed that the contents of soil organic carbon, total nitrogen, and hydrolyzable nitrogen under both natural and artificial restoration increased significantly compared to that of bare mining areas, but remained lower than that of surrounding forest soils. Furthermore, the activities of soil acid phosphatase, N-acetyl-β-D-glucosidase, leucine aminopeptidase, and β-glucosidase were found to be significantly higher under artificial restoration. The Chao1 index and Shannon diversity index of soil fungi and bacteria indicated that natural restoration method exhibited greater efficacy than artificial restoration, with the lowest diversity observed in bare mining areas. The dominant phyla of bacterial were Proteobacteria, Actinobacteria, and Acidobacteria, while the dominant fungal phyla were Ascomycota and Basidiomycota. Soil effective phosphorus, pH and quick-acting potassium were the environmental factors that significantly affected the bacterial community structure. In addition, the soil fungal community structure was significantly negatively correlated with soil total phosphorus, effective phosphorus, pH, water content, total nitrogen and hydrolyzable nitrogen. Conclusions The process of soil recovery under artificial restoration is accelerated, and the soil physicochemical properties, enzyme activity and microbial community diversity demonstrate a more pronounced recovery effect. Conversely, soil recovery under natural restoration is gradual, yet it is conducive to the recovery of soil microbial community structure and diversity. The findings of the study provide a scientific foundation for the identification of effective methods for ecological function recovery in the context of mining re-greening and the optimisation of mining re-greening strategies.