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

Abstract

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.

Keywords: CO(2) flux; Carbon sequestration; Mine soil; Reclamation; Surface coal mining.