Characteristics of soil organic carbon fractions of different vegetation types in coal mining subsidence areas and their influencing factors

Coal mining causes surface subsidence and also leads to the loss of soil carbon pools. As a key link of ecological restoration in subsidence areas, vegetation restoration can effectively reduce soil carbon loss. In order to clarify the function of ecological carbon bank in coal mining subsidence area, arbor-shrub-grass mixed forest, arbor-grass mixed forest, arbor-shrub mixed forest, arbor forest, grass-shrub mixed forest, grassland, and shrub forest soils of the Huaibei Central Lake coal mining subsidence area were used as the research objects. The total organic carbon (TOC), dissolved organic carbon (DOC), easily oxidized organic carbon (EOC), microbial biomass carbon (MBC), and recalcitrant organic carbon (ROC) contents in different soil layers (0—20, 20—40, 40—60 cm) were measured to analyze the distribution differences of soil organic carbon (SOC) components among different vegetation types and soil layers, and explore the influence of soil physicochemical properties on the accumulation of soil SOC components.The results are as follows: (1) The distribution of soil SOC components varies significantly among different vegetation types, with the overall highest component contents found in arbor forests and the lowest in arbor-shrub mixed forests.The soil organic carbon density was highest in the arbor-grass mixed forest (1.98 kg·m−2) and lowest in the shrub forest (1.31 kg·m−2). The soil SOC components and organic carbon density exhibited surface aggregation in the soil profile. (2) The correlation analysis indicates that total soil nitrogen, bulk density, and electrical conductivity are key factors influencing the accumulation of soil SOC components. Total soil nitrogen has a promoting effect, bulk density has an inhibiting effect, and electrical conductivity exhibits varying effects across different vegetation types. (3) The redundancy analysis further indicates that total soil nitrogen is the primary environmental factor affecting the accumulation of SOC components in the upper and middle soil layers.The research results can provide theoretical support and scientific basis for promoting the protection and management of soil carbon stocks in the subsidence area of Central Lake, as well as for enhancing the carbon sequestration capacity during ecological restoration in the Huaihe mining area and other mining subsidence areas.