The influence mechanism of soil pore structure on spatial variability of soil water and nutrients in the mining-induced subsidence area of China northwest

The surface subsidence caused by coal mining in the aeolian sand area of China northwest has seriously affected the soil pore structure and distribution of water and nutrients. In this study, three sample areas (one unexploited area RF, one edge subsidence area MF, and one dynamic subsidence area DF) were set at Dafanpu Coal Mine. The soil moisture content (SMC) and soil organic matter (SOM) content were measured at depths of 0–60 cm for each sampling point. The spatial variability of SMC and SOM in both vertical and horizontal dimensions was examined. Based on computed tomography (CT) technology, the true pore structure of typical soil samples at different depths was scanned, and three-dimensional reconstruction and analysis of soil pores were carried out using Amira Avizo software. The correlation between SMC, SOM content and soil pore parameters was presented, and the influence mechanism of soil pore change on water and nutrient variation in subsidence area was revealed. The results show that the SMC and SOM contents in the subsidence area at a depth of 0–60 cm are lower than those in the unexploited area. The mining-induced subsidence exacerbates the spatial heterogeneity of the horizontal distribution of SMC and SOM content. The variation coefficients of SMC and SOM content increase by 35.77% to 39.56% and 33.29% to 42.74%. The mining-induced subsidence increases the number and porosity of soil pores, particularly the number and porosity of macropores. The connectivity of soil pores in subsidence areas MF and DF is increased by 61.57% and 18.51%, respectively. The SMC and SOM content exhibit significant negative correlations with soil porosity and pore connectivity (P ≤ 0.05). The augmentation of soil porosity and pore connectivity in subsidence areas caused by coal mining are significant factors contributing to the variations in SMC and SOM content.