Microbial properties of mine spoil materials in the initial stages of soil development

The early years of soil genesis during mine spoil reclamation are critical for vegetative establishment and may help predict reclamation success. Mine spoils in the Halle-Leipzig region of Germany were analyzed for microbial changes following a hay mulch-seeding treatment without topsoil or fertilizer application. Microbial biomass carbon (C_mic) and dehydrogenase activity (DHA) of spoils were measured each year in the first 3 yr after treatment. In the third year, bacterial community DNA fingerprints were compared with those from a reference soil. Microbial indicators were measured at three depths in the upper 10 cm of spoils at three sites with contrasting parent materials: glacial till (sandy loam), limnic tertiary sediments (high-lignite sandy clay loam), and quaternary sand and gravel (loamy sand). Before reclamation, C_mic means and standard deviations of surface spoils (0-1 cm) were 9 ± 6, 39 ± 11, and 38 ± 16 mg kg ^-1 for the loamy sand, high-lignite sandy clay loam, and sandy loam spoils, respectively. Within one year, mean C_mic at the surface increased to 148 ± 70, 229 ± 64, and 497 ± 167 mg kg ^-1, respectively, and was significantly higher at 0 to 1 cm than at lower depths. Highest DHA and DNA yields were obtained in the 0- to 1-cm depth of the sandy loam spoils. Microbial biomass C values exhibited significant correlations with DHA, DNA yield, and extractable C for all three mine spoils. Soil microbial indices were more responsive than plant measurements to differences in parent materials.