Soil Properties and Bacterial Community Dynamics in a Coal Mining Subsidence Area: Active Versus Passive Revegetation

Vegetation restoration in disturbed areas can be achieved by passive (spontaneous succession, PR) and active (human-induced, AR) approaches. However, the contributions of different restoration strategies to the soil physicochemical properties and the bacterial community dynamics remain unclear in semiarid coal mining-disturbed areas. We compared the soil properties and bacterial communities in coal mining subsidence areas with AR and PR approaches after 0-15 years of restoration and evaluated the relationships among the vegetation, soil properties, and bacterial communities. Soil bulk density, moisture, organic carbon, available N/P/K, enzymes, and bacterial community diversities decreased in the initial revegetation stage (< 5 years) compared with those in nonsubsidence areas (NS) and then increased during succession at both the AR and PR sites. AR accelerated the recovery of the soil variables relative to passive restoration. The levels of the soil physicochemical properties at AR and PR sites did not recover to NS levels except for soil moisture. Furthermore, the abundance of the dominant bacterial groups did not exhibit good stability, but the bacterial community diversity was restored to the level before surface subsidence after 15 years of revegetation. Plant community biomass, soil bulk density, moisture, organic carbon, available N/P, and enzymes were the most important factors affecting soil microbial communities, while total N, available K, and soil pH showed the absence of a significant relationship. AR can speed up the recovery of the soil variables relative to passive restoration because artificial intervention is important for establishing sustainable soil ecosystems in semiarid disturbed areas.