Microbial Biomass in Reclaimed Soils following Coal Mining in Virginia1

It is well known that soil microbial communities reestablish following disturbance, but limited research has been done on how long this takes in eastern reclaimed coal mine soils. The objective of this study was to track the development of total microbial biomass in reclaimed mine soils following coal mining in southwestern Virginia. A chronosequence of sites was established based on locally documented shifts in vegetation species with succession (0-2, 5-7, 18-20, and 38-42 yr old) on reclaimed sites with undisturbed adjacent sites used as a reference. The 0-2 yr old sites were covered with annual and perennial grasses and forbs, the 5-7 yr sites by thick stands of Lespedeza cuneata, the 18-20 yr sites predominately with Festuca arundinaceae and patches of deciduous trees, and the 38-42 yr old sites with a mix of planted conifers and native Appalachian hardwoods with a grass understory. Undisturbed sites predominately supported mixed Appalachian hardwoods with a mixed forb/grass understory. Four samples were taken from each site age (3 replicates) at the 0-5 cm depth. Chloroform-fumigationextraction was used to determine total organic carbon from lysed microbial cells as a proxy for microbial biomass. Microbial biomass carbon (MBC) did not vary significantly among any of the site ages sampled; however, a general trend of increasing MBC from a low level in the more recently reclaimed sites (131-138 g microbial C kg -1 soil) to a higher level of MBC in the 16-20 and 38-42 yr sites (280 and 244 g microbial C kg -1 soil, respectively) was observed. This indicated a recovery of soil microbial communities with time; possibly well within the 5-year vegetation liability release period mandated by the Surface Mining Control and Reclamation Act (SMCRA). Additional