Structural and compositional variations in undisturbed and disturbed tropical forests of Bhuban hills in south Assam, India

Abstract

The present study describes the structure, composition and regeneration of tree species in undisturbed and disturbed tropical forests in Bhuban hills in southern Assam, India. The study area is part of one of the globally recognized biodiversity hot spots and in spite of the increasing human activities in these forests, so far no information is available on their impacts on plant assemblages in the area. In each forest, the vegetation was analysed through 50 quadrats (10 m × 10 m) in a belt transect of 500 m × 10 m. A total of 49, 47 and 42 tree species were recorded in disturbed forests and 62, 61 and 60 species in undisturbed forests. The average tree density and basal area were significantly higher in undisturbed forests (708.67 and 42.01 m2 ha−1, respectively) than disturbed forests (443.33 and 18.44 m2 ha−1, respectively). The population structure of tree species in disturbed forests showed a fluctuating curve, and in undisturbed forests, it was a reversed J-shaped curve. The present study reveals that the species richness, diversity, density and basal area have significantly declined (P < 0.01) due to anthropogenic disturbances. As reflected from the population structure, most of the tree species in disturbed forests showed poor regeneration status. If degradation of these forests continues at the present pace, several of these species which are providing various ecosystem services to the local human communities may disappear in the very near future.