Experiments on ecological restoration of coal mine spoil using native trees in a dry tropical environment, India: A synthesis

A series of experiments was conducted on the rehabilitation of mine spoil in a dry tropical region of India for determining the suitability of tree species for plantation, growth performance of selected indigenous species in monoculture and impact of the plantations on the restoration of biological fertility of soil. All of the 17 indigenous species examined could grow in the mine spoil and the growth of a majority of them could be improved by amending the mine spoil with NPK fertilizer. Direct seeding showed greatest height of Zizyphus jujuba and Pongamia pinnata on flat surface, and of Azadirachta indica on slope. In terms of diameter, Syzygium cumini performed best on flat surface and Terminalia arjuna on slope. Total biomass in plantations of selected native tree species on mine spoil at 5-yr age varied from 7.2 to 74.7 t ha(-1), being minimum for Shorea robusta and maximum for Dendrocalamus strictus. Total net production ranged from 3.5 (for Shorea robusta) to 32.0 t ha(-1) yr(-1) (for Dendrocalamus strictus), respectively. Microbial biomass in the redeveloping soil was lower compared to that in natural forest soil but immobilization of soil C in microbial biomass was greater in the mine spoil than in the natural forest. The study indicated that net primary production of the plantations was a function of the amount of foliage, soil C was a function of the amount of litter fall and biomass C was a function of soil C. Plantation of trees significantly accelerated the soil redevelopment process on the mine spoil.