The influencing factors and control strategies of soil labile organic carbon in opencast coal mine reclamation

Abstract

In order to reveal the spatiotemporal distribution patterns and influencing mechanisms of soil labile organic carbon (LOC) in the reclamation area of opencast coal mines, we selected nine different vegetation combinations and sample plots spanning four reclamation years from the soil dumping grounds in the Pingshuo opencast mining area, using an undisturbed elm forest as a control area. We employed one-way ANOVA to investigate the distribution patterns of soil LOC within the sample plots. Furthermore, we explored the influencing factors of soil LOC using Structural Equation Modeling and Redundancy analysis methods. and further examined the functional relationship between soil physicochemical properties and soil LOC through regression analysis. The results indicate that: (1) Soil LOC in various areas has obvious surface aggregation characteristics and the trend decreases with the increase of soil depth. (2) Land reclamation can significantly increase soil LOC content, but significant differences in soil LOC exist under various reclamation modes, with mixed forests>original landforms>pure forests, and the Pinus tabulaeformis×Robinia pseudoacacia×Elm tree combination demonstrating the most effective restoration compared to other soil LOC. (3) Soil LOC significantly increases with reclamation time, and the recovery rate of soil LOC is higher than that of soil organic carbon, but even after 26 years, LOC/SOC levels do not reach those of the original landform. (4) Direct factors affecting soil LOC are soil physicochemical properties>soil depth>reclamation time>reclamation mode. (5) The overall explanatory power of soil environmental factors for soil LOC is 68.52%. The order of explanatory power is clay>available potassium>soil moisture content>sand>pH>powder>alkaline nitrogen>bulk density>available phosphorus. The explanatory power of clay particles, available potassium, and water content for LOC is higher than other factors. The above results indicate that multilevel and diversified vegetation planting strategies should be adopted during vegetation reconstruction, with an appropriate increase in the proportion of local advantageous vegetation and attention paid to protecting the original microbial community of the reclaimed land. At the same time, improving soil texture and strengthening water and fertilizer management are key to promoting ecological restoration in mining areas. The above research can provide carbon sequestration and sink enhancement proposals and corresponding theoretical support for the reclamation of opencast mining areas.