Microbial respiration and organic carbon indicate nutrient cycling recovery in reclaimed soils

Soil quality and the ability of soil to sustain nutrient cycling in drastically disturbed ecosystems will influence the establishment and maintenance of a permanent and stable plant community. We undertook research to evaluate a recently developed method to assess soil quality and nutrient cycling potential in a series of reclaimed soils. The method involves correlating the 3-d flush of microbial respiration after a soil is rewetted against a range of soil biological parameters. Soils were sampled from a number of reclaimed coal mines, a reclaimed uranium mine, and native, undisturbed prairie. All sites were located in semiarid Wyoming. Soils were dried at 55 degrees C, rewetted, and microbial respiration measured at 3 d (Cmin(0-3d)) and 21 d (Cmin(0-21d)). In addition, microbial biomass C (MBC), N mineralization (Nmin(0-21d)), soil organic C (SOC), and total N were also measured. Correlations between Cmin(0-3d) and the measured soil parameters in reclaimed and native soils were generally strong (r2 greater than or equal to 0.45) and highly significant (P = 0.0001). Differences between reclaimed and native soils were observed, with native soils exhibiting more variability, possibly due to: differences in soil homogeneity/heterogeneity, the relative lability of the substrates present; different microbial communities; and differences in soil structural properties. Correlations between Cmin(0-3d) and the measured soil parameters in spoil material, while significant, were less well correlated. We believe this method is a relatively fast, accurate, and economical means by which soil quality and nutrient cycling can be ascertained. We estimated that a minimum concentration of 0.52% SOC or 0.89% soil organic matter (SOM) is necessary to sustain an adequate level of nutrient cycling in these reclaimed soils.