A pre-requisite to any revegetation plan, as well as restoration of degraded land is the knowledge of physicochemical characterization, which is crucial for prediction of ecological succession for mine overburden spoil, including soil texture, hydrological regimes, pH, organic carbon, nitrogen and extractable phosphorous. Effects of mining activities are markedly adverse, because many of the beneficial soil characteristics may require a long span of time to develop through pedogenic processes, in order to reach the native forest soil condition, which evaluates the degree of functional microbial processes for ecosystem recovery, and used as an index of the progress of soil genesis in mine overburden spoil. Mine spoil samples collected from six different age series overburdens showed progressive increase in clay (%) (r=0.982, p<0.001), water holding capacity and organic carbon, which indicates the development of soil structural stability, aggregation with the increase in age of overburden spoil. The pH of spoil samples was noted to be in acidic range (6.11-6.87). Approximately, 93.7% variability in clay (%) among different mine spoils can be explained due to the variation in organic carbon. The organic carbon, nitrogen and phosphorous content showed an improvement of 2 mg C/g spoil, 161 µg N/g spoil and 8 µg P/g spoil, respectively, over a period of 10 years. Thus, the net annual accumulation rate for carbon, nitrogen and phosphorous on hectare basis amounted to 255 kg C/ha/yr, 20 kg N/ha/ yr and 1 kg P/ha/yr, respectively. Further, it was estimated that the mine overburden spoil to attain the soil features of nearby native forest soil at study site through the process of reclamation, shall take approximately 28 years.

Mining activities lead to land degradation and alter ecosystem functions. Monitoring land degradation status is essential to take appropriate and timely conservation measures. Soil genesis during early years of mine spoil reclamation is critical and may help to predict reclamation success. The microbial activity is significantly influenced by the physicochemical properties, and hence, the assessment of these changes is essential for soil management practices. In the present investigation, the physico-chemical characterization and the activities of six different enzymes (amylase, invertase, protease, urease, phosphatase and dehydrogenase) were periodically analyzed with respect to different coal mine overburden spoil in chronosequence over a period of 10 yr, and compared with the native forest soil, in order to assess their effectiveness in reclaiming mine overburden spoil. Comparative analysis suggested that there was gradual increase in enzyme activities from a nutrient deficient situation (fresh mine spoil) to an enriched soil (native forest soil). Besides, the variation in enzyme activities was significantly attributable to differences in physico-chemical properties.Stepwise multiple regression analysis was performed in order to determine the contribution of different physico-chemical properties influencing the variability in enzyme activities. Further, principal component analysis was able to discriminate six coal mine overburden spoils and native forest soil into independent clusters on the basis of their physico-chemical properties and enzyme activities. The study clearly revealed that the change in microbial indices in terms of enzyme activities were more responsive and correlated very well with the extent of land degradation, and therefore, can serve as biomarker for reclamation studies.

Coal mine overburden spoil created aftermath of mining activities represents disequilibrated geomorphic system. The pedodiversity including its link with biodiversity and landscape ecology describe the spatial diversity has emerged as functional determinants of ecosystem processes. Being the driving force mediating soil processes, ecosystem restoration through mine spoil genesis is monitored based on the shift in microbial community structure in different age series coal mine spoil. Phospholipid fatty acid analysis is culture-independent approach, which provides a set of molecular markers to determine microbial community composition and discriminate microbial communities of different origin. PLFAs are synthesized during microbial growth, rapidly degraded following cell death and reliably reflect living microbial communities. Relative distribution of 51 PLFAs revealed significant variation in microbial community structure across the sites with Shannon diversity index varies from 1.5265 (OB0) to 2.0139 (OB15) and Pielous evenness index from 0.4110 (OB0) to 0.5260 (OB15). Fungal to bacterial ratio exhibited an increasing trend from OB0 (0.055) to OB15 (0.348) over time, which revealed the sign of mine spoil genesis. The principal component analysis and redundancy analysis discriminate different age series coal mine spoil into independent clusters, which evaluated the broad scale patterns of microbial community structure influencing the pace and progress of mine spoil genesis.

Mine spoil genesis mostly focuses on careful consideration of enzyme activities and kinetics parameters toelucidate microbial mediated biotransformation and nutrient cycling including their link with the variationin physicochemical properties, microbial community dynamics and landscape ecology as the functionaldeterminants of ecosystem function. The relative distribution of microbial populations exhibited progressiveincrease in different age series coal mine overburden spoil over time. The kinetic parameters of amylase,invertase, protease, urease, phosphates and dehydrogenase activities were determined to assess the metabolicresponse in different age series coal mine spoil. Gradual increase in Vmax and decline in Km of enzymeactivities representing the quality and affinity of enzymes correlated well with the shift in microbialcommunity composition over time. Besides, the shift in catalytic efficiency (Vmax/Km) has greatersignificance as early and sensitive indicators of the changes in soil properties influencing microbialcommunity dynamics across the sites. The enzyme activity and kinetic parameters correlated well the changesin physicochemical properties over time across the sites. PCA and RDA analysis can able to discriminatesix different age series coal mine overburden spoil and nearby NF soil into independent clusters based onthe variability in physicochemical properties, microbial community structure, enzyme activities and kineticparameters. The study suggested that the kinetic indices of enzyme activities can be used as reliable ecologicalbiomarkers to monitor the progress of mine spoil genesis.