Relationship between soil water content and vegetation distribution in a small area before and after coal seam mining: a case study of coal mining subsidence area in Northwest China

Soil water content and vegetation are two key factors in the ecological recovery of coal mining subsidence areas, and the distribution of vegetation both above- and belowground has an impact on soil water content. In this study, ground penetrating radar (GPR) was used to detect the soil water content of vegetation roots and soil in the arid and semi-arid coal mining subsidence boundary area of western China in a small scale (50 x 50 m). The results show that the accuracy of soil water content obtained by GPR is similar to that measured, and the correlation coefficient can reach 0.97. The average error between the root depth detected by GPR and the measured root depth was 0.03 m, and the correlation coefficient was 0.89. Compared with before mining, surface soil water content decreased by about 1.87% after mining, and the average water content of strata within 1 m decreased by about 1.12%. Radar detection results before coal mining show that the stratum with high soil water content (> 10%) has an obvious correlation with the buried depth of plant roots, which is between 0.2 and 0.6 m. Vegetation roots have an important effect on soil water content distribution in shallow strata of coal mining subsidence area. After coal mining, the distribution relationship between surface soil water and vegetation, shallow stratum water and plant roots is destroyed.