Ecological study of revegetated coal mine spoil of an Indian dry tropical ecosystem along an age gradient

Distribution of soil organic carbon and glomalin related soil protein in reclaimed coal mine-land chronosequence under tropical condition

The revegetation on mine spoiled lands has potential to improve the status of reclaimed mine-soil quality. However, to date the temporal dynamics of labile and stable fractions of soil organic carbon (SOC) and glomalin related soil protein (GRSP) have not been satisfactorily demonstrated. We investigated SOC and GRSP fractions including labile particulate OC (POC) and easily extractable GRSP (EE-GRSP) and stable non-particulate OC (NPOC) and difficulty extractable GRSP (DE-GRSP) along with other important soil properties in six reclaimed mine lands chronosequence (1 to 26 years old) and a reference forest site in Raniganj Coalfield, India. Our results demonstrated that the accumulation of SOC and GRSP significantly increased with increasing age of the sites, with greater extent of increment after 26 years were seen in labile POC (6.6×) and EE-GRSP (11.5×) compared to stable NPOC (1.8×) and DE-GRSP (6.2×). The higher contribution of GRSP-C in NPOC compared to TOC across the sites, indicate the proximate role of GRSP in accumulation and stabilization of SOC during the pedogenesis. The multivariate analysis revealed strong association among arbuscular mycorrhizal fungi (AMF) spore density, microbial biomass carbon, SOCs and GRSPs, suggesting the factors involved in SOC accumulation likely contributed to AMF proliferation and GRSP enrichment during the reclamation process. Moreover, strong correlation of GRSP and SOC with soil's bulk density, pH, total N and C/N ratio, suggest increasing GRSP and SOC content resulted in multi-level improvement in soil properties. Our results highlight the importance of using GRSP and SOC as indicator during mine land reclamation.

Influence of different revegetation choices on plant community and soil development nine years after initial planting on a reclaimed coal gob pile in the Shanxi mining area, China

In order to identify suitable pioneer plant species for future revegetation of coal gob piles, a field survey was conducted to assess the success of different revegetation species and their influence on soil development nine years after initial planting on a reclaimed coal gob pile in the Yangquan mining area of Shanxi province, China. Data were analyzed using a quantitative classification method (TWINSPAN), ordination techniques (DCA and DCCA), Principal Component Analysis (PCA) and a geo-accumulation index (Igeo). The results revealed that the low levels of soil moisture and available N were the major limiting factors affecting plant community development on the coal gob pile, not metal toxicity. The plant communities that developed had significantly improved the topsoil (0-10cm) quality on the reclaimed coal gob pile nine years after initial planting (p<0.05), but the degree of improvement varied greatly with different planted species. Revegetation types comprised of the planted leguminous species, Medicago sativa and Amorpha fruticosa, and the non-leguminous species, Populus tomentosa and Salix babylonica had the best ecological restoration effects on the reclaimed coal gob pile. Revegetation using these species is therefore recommended for future reclamation of abandoned coal gob piles in this region.

Assessment of carbon sequestration potential of revegetated coal mine overburden dumps: A chronosequence study from dry tropical climate

Development of secondary forest as post-mining land use in the surface coal mining degraded sites is of high research interest due to its potential to sequester atmospheric carbon (C). The objectives of this study were to assess the improvement in mine soil quality and C sequestration potential of the post-mining reclaimed land with time. Hence, this study was conducted in reclaimed chronosequence sites (young, intermediate and old) of a large open cast coal project (Central Coal Fields Limited, Jharkhand, India) and results were compared to a reference forest site (Sal forest, Shorea robusta). Mine soil quality was assessed in terms of accretion of soil organic carbon (SOC), available nitrogen (N) and soil CO₂ flux along with the age of revegetation. After 14 years of revegetation, SOC and N concentrations increased three and five-fold, respectively and found equivalent to the reference site. Accretion of SOC stock was estimated to be 1.9 Mg C ha^-1year^-1. Total ecosystem C sequestered after 2-14 years of revegetation increased from 8 Mg C ha^-1 to 90 Mg C ha^-1 (30-333 Mg CO₂ ha^-1) with an average rate of 6.4 Mg C ha^-1year^-1. Above ground biomass contributes maximum C sequestrate (50%) in revegetated site. CO₂ flux increased with age of revegetation and found 11, 33 and 42 Mg CO₂ ha^-1year^-1 in younger, intermediate and older dumps, respectively. Soil respiration in revegetated site is more influenced by the temperature than soil moisture. Results of the study also showed that trees like, Dalbergia sissoo and Heterophragma adenophyllum should be preferred for revegetation of mine degraded sites.

Relation between edaphic factors and vegetation development on copper mine wastes: a case study from Bor (Serbia, SE Europe)

The relationship between edaphic characteristics and vegetation growing on mine wastes in the Bor region (East Serbia, SE Europe) was studied using multivariate statistical analysis. The influence of edaphic factors on the composition of plant life-forms was also investigated, since it could reflect strategies for the avoidance of or tolerance to disturbances of ecosystems. The goal was to provide potential models for the restoration and management of this and similar mine waste areas. The results of this study imply that soil textures, nitrogen contents, reclamation technology and the presence of hydrothermally altered andesite as the type of bedrock significantly influenced plant colonization and vegetation composition of the Bor mine wastes. These edaphic factors explained 30.3 % of the total variation in the vegetation data set. It was also revealed that the pattern of plant life-forms found on the considered site groups corresponded to the soil texture. Based on their relative abundance on the investigated sites and relationships with soil properties it is concluded that therophytes and geophytes are unsuccessful primary colonizers of the Bor mine wastes. Hemicryptophytes of psammophytic character were the most successful primary colonizers and therefore potential candidates for anthropogenically-assisted natural recovery. This study suggested that an assessment of edaphic factors should be widely used in the characterization of mine wastes prior to reclamation. Estimation of their role in the development of existing mine vegetation should predate reclamation procedures. Thus, approaches based on adequate plant life-forms should have a more prominent role in future mine reclamation schemes.

Mine spoil acts as a sink of carbon dioxide in Indian dry tropical environment

Economically important mining operations have adverse environmental impacts: top soil, subsoil and overburden are relocated; resulting mine spoils constitute an unaesthetic landscape and biologically sterile or compromised habitat, and act as source of pollutants with respect to air dust, heavy metal contamination to soil and water bodies. Where such spoils are revegetated, however, they can act as a significant sink for atmospheric carbon dioxide (CO2) through combined plant succession and soil formation. Revegetation, drainage, reprofiling and proper long term management practices help recapture carbon, improve soil quality and restore the soil organic matter content. A survey along an age gradient of revegetated mine spoils of 19 years in Singrauli, India by the authors showed an accumulation of total C in total plant biomass, mine soil and soil microbial biomass by 44.5, 22.9 and 1.8 t/ha, respectively. There was an increase in total sequestered C by 712% in revegetated mine spoils after 19 years, which can be translated into annual C sequestration potential of 3.64 t Cha(-1) yr(-1). Carbon sequestered in revegetated mine spoil is equivalent to 253.96 tonnes/ha capture of atmospheric carbon dioxide (CO2). This indicates that mine spoil can act as a significant sink for atmospheric CO2. Annual C budget indicated 8.40 t Cha(-1) yr(-1) accumulation in which 2.14 t/ha was allocated to above ground biomass, 0.31 t/ha in belowground biomass, 2.88 t/ha in litter mass and 1.35 t/ha in mine soil. This shows that litter mass allocation is much important in the revegetated site. Decomposition of root and litter mass contributes C storage in the mine soil. Therefore, revegetation of mine soils is an important management option for mitigation of the negative impacts of mining and enhancing carbon sequestration in mine spoils.