Development of microbial properties and enzyme activities in copper mine wasteland during natural restoration

• Microbial biomass and enzyme activities increased during successional process.
• Microorganisms became increasingly efficient at carbon use.
• PCR-DGGE analysis showed no significant change in microbial diversity.
• Microbial biomass and enzyme activities were sensitive to heavy metal in wasteland.

A copper mine wasteland consists of a pedogenetic substrate, and regeneration of ecosystems on mine wasteland undergoes typical primary succession. In this study, microbial biomass, basic respiration, microbial diversity and enzyme activities were investigated during the natural successional process in two copper mine wastelands with different restoration development times. As the plant ecosystem progressed from bare land with cryptogamic crusts to vascular plant communities, organic matter, total nitrogen (N), available phosphorus (P) and water holding capacity increased, whereas pH and toxicity of heavy metals decreased. Along with the natural process of soil development resulting from the amelioration of substrate condition, microbial biomass C and N, and urease and alkaline phosphatase activities in surface layers increased, and the metabolic quotient decreased. Microbial biomass gradually exhibited strong spatial heterogeneity during succession. Microbial biomass and enzyme activities had positive correlations with organic matter and nutrient conditions (N and P), and negative correlations with pH and heavy metals. The concentrations of organic matter, N, P and available Cu significantly influenced microbial biomass and activity. The analysis of 16S rDNA fragments by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) showed no obvious trend in microbial diversity during succession. Phylogenetic analysis of 16S rDNA sequences generated from DGGE gels indicated that bacteria mainly included Proteobacteria (alpha-, beta- and gamma-Proteobacteria), Firmicutes (Bacillus and Clostridia), Actinobacteria, Nitrospirae, Deinococcus-Thermus and Bacteroidetes. The natural successional series consisted of species adapted to mine wastelands. Soil microbial biomass and enzyme activities tended to be more sensitive to heavy metals.