Coal mining is the world's primary means of coping with an increasing energy demand. However, with the mining of coal, the regional ecosystem has been damaged to varying degrees, resulting in a decrease in the "carbon sink" capacity. Vegetation restoration is the basis for the restoration of degraded ecosystems and carbon sequestration functions in mining areas. However, no systematic studies have been conducted on the effects of vegetation restoration on soil organic carbon in coal mining areas on a global scale. Therefore, it is not possible to accurately predict the response of the global SOC pool to vegetation restoration. In this study, soil physicochemical properties of vegetation restoration were collected from 112 peer-reviewed articles to assess the effects of vegetation restoration type, soil depth, restoration year, mean annual temperature, annual precipitation, and elevation on soil organic carbon in coal mining areas and to identify relevant key drivers. The results showed that the damaged coal mine area could significantly improve the physicochemical properties of the soil through vegetation restoration. The restored soils had 39.02% higher SOC reserves compared to that in unrestored or naturally restored soils. When environmental factors were not considered, the vegetation restoration types that were favorable for SOC stock accumulation were cropland > woodland > grassland > shrubland. All four types of vegetation restoration significantly increased the SOC storage in the surface layer (0-20 cm). Grassland and shrubs significantly increased SOC storage at depth (>40 cm), whereas SOC storage at depth under woodland and farmland types was not significantly different from SOC storage after unrestored or natural restoration. The increasing trend of SOC storage after vegetation restoration decreased with increasing soil depth. The specific vegetation restoration strategy should select the appropriate vegetation type according to the climatic conditions. The types of vegetation restoration with higher carbon sequestration effects in damaged coal mining areas with mean annual temperature <0℃ and mean annual precipitation <500 mm were grassland or shrubland. In contrast, woodland and cropland restoration types could better increase SOC storage in environments with mean annual temperature >15℃ and annual precipitation >800 mm. TN, BD, AN, and AK were the main factors influencing the ability to affect soil carbon sequestration. This study can provide a theoretical reference for quantifying the carbon sequestration effects of different vegetation restoration measures in damaged coal mining areas and the restoration and reconstruction of degraded ecosystems.
Keywords: coal mine; cropland; grassland; shrubland; soil organic carbon stocks; soil properties; vegetation restoration; woodland.