Rehabilitation of an Abandoned Limestone Mine in the Lower Western Himalayas - Impact Assessment on Vegetation Development and Floristic Diversity

Rehabilitation of mine spoiled areas through suitable bioengineering measures and allowing natural succession of vegetation to progress is an essential step towards ecosystem recovery. In this paper, the effect of such measures accompanied with protection of an abandoned limestone mine have been described. Development of vegetation and its phytosociological characteristics were compared with an adjoining but slightly disturbed natural forest situated in the lower sub-humid Himalayan region. In the rehabilitated area, an introduced species Leucaena leucocephala, had the highest Importance Value Index (IVI) of 66.05, followed by a sedge species Eriophorum cosmosum (lVI 58.85) and Acacia catechu (IVI 51.85). The area also supported a significant growth of Thysaloena maxima and Saccharum spontaneum. In the adjoining non-mined forest, the highest IVI value was recorded for Corcorus laurifolius (55.98), followed by Mallotus phillipensis (47.55), Murraya koenigii (38.71) and Bauhinia retusa (37.02). These species, which are associates of Shorea robusta forests, are valuable fodder species in the region specially during the winters, and were, therefore, not harvested while timber yielding species like Shorea robusta and Toona ciliata are now totally absent from the area. Cluster analysis and ordination by Principal Component Analysis (PCA) revealed distinct loading of plots along different axis due to an underlying edaphic gradient, external seeding and soil moisture availability. Diversity (H') of tree species in the natural forest was higher than the rehabilitated area, which otherwise had higher diversity values for shrubs and grasses. It is suggested that existing levels of biotic disturbances be restricted for some more time to provide an opportunity for late colonizers to establish themselves in the area.