Microbial population dynamics influence basal soil respiration and it’s impact on mine spoil genesis in chronosequence iron mine overburden spoil

Abstract

Assessment of microbial biomass pool and microbial respiration have been used as sensitive soil quality indicators of mine spoil genesis and served as useful criteria for successful rehabilitation of ecologically disturbed mining areas. The variation in moisture, organic C and microbial biomass C in different age series iron mine overburden spoil and nearby NF soil were analyzed. The analysis showed consistent increase in moisture (6.643-11.329)%, organic C (0.142-2.228)% and microbial biomass C (51.324-648.719) mg/g spoil from IB₀ to IB₂₅ with increase in age of iron mine overburden spoil. Gradual improvement in organic C was found to be correlated with moisture (r = 0.996; p < 0.01) and microbial biomass C (0.999; p < 0.01). Besides, MBC:OC and BSR:OC ratio can be used as sensitive indicators of mine spoil reclamation, which were found to be relatively higher in IB₀ compared to NF soil. Wide variation in microbial community composition, basal soil respiration (0.158-0.463) mg CO₂-C/g spoil/hr and microbial metabolic quotients was observed across the sites over time. Stepwise multiple regression analysis was performed to quantify the contribution of microbial communities, moisture, organic C, microbial biomass C explaining the variability in microbial soil respiration. Principal component analysis was able to discriminate seven iron mine overburden spoil and NF soil into independent clusters, which correlated well with mine spoil genesis and reclamation progress. Redundancy analysis illustrated the contribution of moisture content, organic C, microbial biomass C and microbial community dynamics towards the shift in basal soil respiration useful for monitoring mine spoil restoration.