Influence of reclamation management practices on microbial biomass carbon and soil organic carbon accumulation in semiarid mined lands of Wyoming

In recent years, interest has been generated in the ability of disturbed soils to accumulate organic carbon (C), thereby sequestering C from the atmosphere as well as improving their edaphic characteristics. Responses and recovery of soil microbial populations and processes, including C cycling, to disturbance caused by surface mining and subsequent reclamation are not well understood. This study was conducted to determine the long-term influence (>10 years) of a number of reclamation management practices on the concentration and amounts of soil organic C (SOC) and microbial biomass C (MBC) in reclaimed soils at five surface coal mines located in semiarid regions of Wyoming. Comparisons were made across a number of commonly used reclamation management practices (grazing, topsoil handling, seed mixes, and mulching) as well as between paired treatments within each management practice (i.e., grazed vs. ungrazed; stockpiled topsoil vs. direct hauled topsoil; grass vs. shrub seed mix; hay crimped mulch vs. stubble mulched). There were no significant differences in SOC concentrations between paired treatments for a given practice but there were some differences between management practices. In the majority of cases, undisturbed, native soils had significantly greater SOC concentrations than reclaimed soils. In contrast, there were significant differences in MBC between paired treatments and between management practices, as well as between management practices and undisturbed soils. Across all mines, half of the mines reclaimed soils had masses of SOC that were similar to, or greater than, undisturbed soil reflecting their ability to accumulate C.