Variation of Soil Carbon, Nitrogen and Phosphorus and Ecological Stoichiometric Characteristics During Land Degradation in Coal Mining Subsidence Area

In order to explore the effects of land degradation on soil carbon, nitrogen and phosphorus and ecological stoichiometry in semi-arid coal mining subsidence area, the spatial pattern of soil carbon, nitrogen and phosphorus content, reserves and ecological stoichiometric ratio in the process of land degradation was studied by space-time substitution method with the soil in three stages of non-degradation, mild degradation and severe degradation as the research object. The results showed that :(1)Land degradation caused an average decrease of soil moisture content and porosity by 50.8% and 22.4%, respectively, resulting in an increase of soil pH and bulk density by 16.0% and 23.8%, respectively.(2)The soil organic carbon content and storage decreased by 55.6% and 50.7%, respectively, due to land degradation. The carbon loss in the surface soil was significant, and the nitrogen content and storage decreased by 21.8% and 13.9%, respectively. The soil nitrogen damage in the middle layer was the largest, and the phosphorus content and storage decreased by 37.9% and 31.8%, respectively.(3)Soil C/N decreased by 18.9%, C/P and N/P increased by 7.9% and 35.4%, respectively, after mild land degradation. Soil C/N and C/P decreased by 68.2% and 64.4%, respectively, while N/P increased by 16.1% after severe land degradation. (4) Soil water content and other environmental factors have different degrees of influence on soil carbon, nitrogen and phosphorus content, C/N and C/P, but no significant correlation with soil N/P. In summary, land degradation caused by multi-dynamic erosion damage in coal mining subsidence areas will significantly reduce soil environmental quality, cause soil drought, barrenness and salinization, and reduce the storage and supply capacity of ecosystem carbon, nitrogen and phosphorus.