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

Abstract

Mineral nitrogen (MN), belowground (root) biomass (BGB), soil nitrogen (N) mineralization (NM), microbial biomass N (MBN) and mine dump stability of a revegetated mine spoil were studied after 2, 6, 10 and 12 years of re-vegetation on coal mine spoil site. MN in revegetated mine spoil ranged from 7.4 to 11.6 kg ha(-1), NM from 38.4 to 252 kg ha(-1) year(-1), MBN from 86 to 426 kg ha(-1), and BGB from 380 to 3,750 kg ha(-1). Mining caused decline of physico-chemical characteristics of soil like MN by 46 %, N-mineralization by 92 %, MBN values by 91 %, respectively compared to forest ecosystems and reduction of total plant biomass (above ground and below ground). Revegetation of mine spoil caused increase in MN values by 12, 36 and 76 %, BGB values by 380, 1770 and 3750 times, NM values by 0.6, 3.58 and 9.5 times and MBN values by 0.43, 2.77, and 6.07 times in 2, 6 and 12 years, respectively. BGB was highly correlated with MN and MBN. Clay content was positively correlated to MN, NM, and the age of revegetation (P < 0.01). Numerical modelling indicated that revegetation increased the dump slope stability with a factor of safety from 1.2 to 1.4, 1.7, 1.9 and 2.1 after 2, 6, 10 and 12 years, respectively. Thus, long-term revegetation was found to enhance the dump stability and the soil fertility status in mine spoil, where plant biomass and microbial biomass provide major contributions in ecological redevelopment of the mine spoil.