Land use impacts on soil aggregate associated organic carbon in reclaimed coal mining subsidence areas: mechanisms and implications.

Under the background of ecological restoration and soil structure improvement in coal mining subsidence areas, understanding the impact of land use on soil organic carbon pools and aggregate characteristics is of great significance to evaluate the quality change and ecological effect of reclaimed soil and guide the improvement of reclaimed soil. Although the dynamics of soil organic carbon under land use changes have been studied, the mechanism of aggregate carbon protection in reclaimed mining soil is still unclear. Taking the reclaimed soils of farmland, woodland, and wasteland in the Dongtan mining area of Zoucheng City in Shandong Province as the research object, by comparing the particle size composition of soil aggregates, the distribution characteristics of organic carbon in 0-20 cm and 20-40 cm soil layers, and analyzing the differences of different organic carbon components, it was found that the organic carbon content of aggregates in the 0-20 cm soil layer was higher than that in the 20-40 cm soil layer; In topsoil, the contribution of fine aggregates to total organic carbon was the largest; the contents of free light fraction (free LF) organic carbon in fine aggregates, micro-aggregates, and total free light fraction organic carbon in forest soil were significantly higher than those in farmland and wasteland. These results suggest that fine aggregates may serve as primary carriers of reclaimed soil organic carbon. The study on the surface soil aggregate organic carbon helps reveal the transformation and accumulation process of reclaimed soil organic carbon. The study found that woodland reclamation may enhance microbial-driven soil organic carbon storage, suggesting that targeted land-use strategies have the potential to maximize the carbon sequestration capacity in degraded ecosystems. Findings are specific to the 7-year reclamation period and Dongtan mining area, requiring long-term regional validation.