Plant diversity, net primary productivity and soil nutrient contents of a humid subtropical grassland remained low even after 50 years of post-disturbance recovery from coal mining

Assessment of environmental impact of coal mining on natural ecosystems and monitoring of subsequent ecological restoration process of mined areas are essential for devising reclamation strategies for mining-affected landscapes. The present study was designed to assess the post-disturbance recovery of vegetation, primary productivity and soil nutrient build-up of a humid subtropical grassland ecosystem following coal mining activities. Two replicate sites each for the undisturbed grasslands (UG), mining-affected (MG) and recovering grasslands of 15 (RG15) and 50 (RG50) years old were selected. There was a distinct pattern of species colonization and replacement during different years of recovery. Species richness, biomass, net primary productivity and soil pH declined following disturbance but increased with recovery age. Soil organic C and total N were high in the MG sites but significantly declined with recovery age. Soil total P and exchangeable K and Mg were low even at the 50th year of recovery indicating extremely slow recovery rate of these nutrients. Considering the extremely slow natural recovery of vegetation and soil nutrients, it is recommended to carry out artificial or aided vegetation restoration using native grass species tolerant to disturbance. Six species which are well-adapted to the mining environment and were present in both undisturbed and mining-affected recovering grasslands, viz. Arundinella khaseana, Cyanotis vaga, Eragrostis nigra, Polygonum bistorta and Fimbristylis hookeriana, are recommended for aided vegetation regeneration.