Deciphering Soil Bacterial Community Structure in Subsidence by Underground Coal Mining in Arid and Semi-Arid Area

Subsidence caused by underground coal mining results in nutrient leakage and soil degradation. However, bacterial community and its response to subsidence after 1 year are unknown in arid and semi-arid areas northwest China. Soil samples from 5 unexplored areas (MC, RC, YC, LC and ZC) and one subsidence area after 1 year of mining above a coal working face were collected to determine soil biogeochemical properties and bacterial community. Results showed soil biogeochemical properties decreased with depth and were significantly higher in MC and RC than in YC, LC and ZC. The dissolved organic carbon (DOC), available nitrogen (AN), available phosphorus (AP), available potassium (AK), B-1, 4-glucosidase (BG), alkaline phosphatase (PP) and microbial biomass carbon (MBC) in subsidence of marginal zone of a coal working face were significantly lower than those in control, while activities of B-1,4-N-acetylglucosaminidase (NAG) and catalase (CAT) were higher, suggesting subsidence led to a loss in nutrients and a reduction in microbial biomass. High-throughput sequencing revealed Sphingomonas, Gemmatimonas, Pseudomonas and Gp6, involved in nutrient cycles, were dominant in this region. Relative abundances of Sphingomonas, Pseudomonas, and Arthrobacter were decreased in subsidence, whereas that of Gemmatimonas was increased. The predicted abundances of genes for metabolisms of xenobiotics via cytochrome P450 pathways and nitrogen were low in ZP, while peroxidase was high, indicating low levels of N cycling and capacities for degradating of xenobiotics and polycyclic aromatic hydrocarbons (PAHs) occurred in marginal zone, while resistance to hydrogen peroxide was strengthened. Redundancy analysis (RDA) revealed electrical conductivity (EC), soil water content (SWC) and soil depth governed bacterial community structure. Overall, subsidence caused losses in soil water and nutrients, alteration of bacterial community structure, and ultimately reduced soil nutrient conversion. Soil quality was significantly reduced, and artificial remediation involving filling of cracks after mining might be necessary, especially in marginal zone.