Vegetation structure, composition and species diversity in an age series of coal mine overburden dumps.
This paper reports on the vegetation composition and diversity of herb, shrub and tree layers developing on an age series of overburden dumps (1, 3, 9, 12, 18 and 21yr) in Bansra and Sonepur Bazari colliery of Raniganj Coalfields. An adjacent native forest Garhjungle was also studied to compare the vegetation development. Total 69, 20, and 30 species of herbs, shrubs including climbers, and trees, respectively, were recorded from the overburden dumps, whereas 10 species of trees, 7 of shrubs and 20 herbaceous species were recorded from the natural forest Garhjungle. Four indices of species diversity estimated the richness, heterogeneity, evenness and dominance of species. Herbs appeared from 1yr dump while shrubs and trees appeared from 3yr onwards. Herb layer was most diverse in the early successional stage while shrub layer was most diverse in the intermediate stage. Density of herbs and shrubs decreased, whereas density, basal area and diversity of tree increased with increase in dump age. Herb layer was dominated by invasive species in the initial phase of succession and gradually replaced by higher successional herbs. Shrub layer was dominated by invasive species throughout the succession. Importance of, only invasive tree species recorded, increased in the late successional stage. Leucaena leucocephala Generic Coefficient indicated the possibility of ecological restoration.