Coal mining practices reduce the microbial biomass, richness and diversity of soil

• Post-mined soils have low microbial diversity, biomass, and enzymatic activity.
• Thiobacillus, Sphingomonas, and Novosphingobiumwere abundant in post-mined soils.
• Bradyrhizobium was the most abundant genus in forest site and Bacillus in grassland.
• Microbial diversity and abundance of studied post mined soils decrease irreversibly.

Changes within the environment by mining processes include increased soil acidification, compaction, erosion, and air and water pollution. As it affects directly the soil microbial community, it may trigger severe impact on the biogeochemical cycles. The objectives of this study were to evaluate how the soil microbial community changes over time after mining and soil reconstruction at the largest coal mine in Latin America. To address this question, we compared soils from undisturbed native forest and grassland to five different sites at various stages of recovery post coal mining. We compared and correlated the soils' chemical features to the soil microbial biomass, soil enzyme activity, and prokaryotic phylogeny and diversity. 42 samples were collected from the seven sites and the V4 region of the 16S rRNA gene was sequenced on the Illumina HiSeq platform. Reads were classified to identify 525 genera from Bacteria and Archaea domains. The composition of the microbial community of post-mined sites was significantly different from the undisturbed sites. Soil from the reconstructed sites showed a significantly lower microbial diversity and biomass, and lower activity of the dehydrogenase and β-glucosidase enzymes when compared to undisturbed soils. The most abundant genera found in the reconstructed soils were Thiobacillus, Sphingomonas, Novosphingobium, Acinetobacter, and Variovorax. Bradyrhizobium was the most abundant genus in the undisturbed forest site, and Bacillus in the undisturbed grassland site. Microbial diversity increased as sites recuperated, but the microbial composition and abundance of post mined soils remained changed.