Long term natural restoration creates soil‐like microbial communities in bauxite residue: a case for 50‐year field study

Ecological reconstruction on bauxite residue disposal areas is regarded as an effective approach to eliminate potential environmental risks. Establishment of microbial communities and associated functions may improve physical and chemical properties, and may stimulate soil formation in bauxite residue. Spontaneous colonization at a disposal area in Shandong Province, China, over 50 years, indicated that natural weathering can ameliorate residues, and in turn, support the establishment of vegetation communities. Residue samples were collected from unrestored, poorly restored and well restored areas to investigate the development of microbial communities and associated functions. Microbiota significantly developed after long term natural restoration. Microbial biomass, respiration and enzyme activities significantly increased in restored bauxite residue, whereas the metabolic quotient significantly decreased. In addition, the long‐term natural restoration significantly shaped the microbial structure from alkalophilic and halophilic assemblages (Firmicutes and Actinobacteria) to neutrophilic assemblages (Acidobacteria and Planctomycetes). Both microbial communities and associated functions in well restored residue had high similarity with that in natural soil, indicating that long term restoration created diverse soil‐like microbial communities and functions. Redundancy analysis (RDA) revealed that TN, followed by Na+, ESP, SOC, AP and pH were the major influence factors in the development of microbial communities in bauxite residue. These findings provide us a biogeochemical perspective to reveal soil formation in bauxite residue and suggest that nutrient supplement and regulation of salinity‐alkalinity may benefit for the establishment of microbial communities and functions in bauxite residue