Impacts of selective logging on diversity, species compostion and biomass of residual lowland dipterocarp forest in central Western Ghats, India
Résumé
Studies on the residual impact of logging on the diversity and composition of tropical forests are scarce in India. We examined the impact of selective logging on tree species richness, composition and structure prevalent after 27 years. Trees ≥ 30 cm girth at breast height were inventoried in four 1 ha plots in selectively logged patches and two 1 ha plots in an adjacent unlogged patch of lowland dipterocarp forest continuum, Uppangala, central Western Ghats, India. We enumerated 2343 trees (598 trees ha–1) belonging to 116 species (63 species ha–1) and 1345 trees (672 trees ha–1) belonging to 68 species (55 species ha–1) in logged and unlogged plots, respectively. The species richness in logged plots as compared to unlogged plots varied with spatial scale of sampling: at 1 ha scale two logged plots had higher species richness whereas it was high in only one plot at 400 m2 scale. Logged plots had low floristic similarity between them and also with the unlogged plots. Mantel and partial Mantel tests proved that logging was the main driver for the species composition rather than the elevation and spatial distance. Higher abundance of species belonging to canopy, intermediate and light wood categories and lower density of emergent, understory and medium wood types were recorded in the logged plots. As compared to unlogged plots, logged plots had 20–59% less above ground biomass (AGB) due to paucity of larger trees, especially in the emergent and medium wood types but higher AGB in canopy and hardwood categories. Our study shows the residual impact of logging even after 27 years and suggests that the recovery process may depend on the resurgence of emergent and medium wood categories.