Tree species diversity of logged and unlogged compartments of lowland dipterocarp forest in the central Western Ghats

Tropical forests worldwide are disappearing at alarming rates due to anthropogenic pressure and environmental change. Logging is one of the main drivers of tropical forest degradation, and it can disrupt forest structure, reduce biomass and even cause local extinction. The French Institute of Pondicherry in collaboration with the Karnataka Forest Department, installed permanent sampling plots in selectively logged (ca. 8.5 trees/ha during 1980s) and unlogged forests near Uppangala village in the central Western Ghats, with the main objective of comparing the demographic processes and structural composition of tree species across spatio-temporal scales between the logged and unlogged forests. The results of monitoring these samples revealed that the composition of the logged forest is not greatly altered, and the growing stock (i.e., stand density and basal area) gradually recovers and tends to become similar to that of unlogged forest within 20 years. The present study investigates whether the logged forest compartments recovered from its state after 25 years of logging by assessing the difference in species richness, diversity, density and basal area at 1 ha and 0.1 ha scales. This study was carried out in six 1-ha plots (4 plots in selectively logged and 2 in unlogged compartments) between November 2010 and November 2011. Difference in species composition was analyzed between logged and unlogged forests based on the proportion of species in primary and secondary category, each storey and size-class. The species richness was higher in the logged forest than in the unlogged forest but the difference are not statistically significant. The number as well as the stem density of secondary and deciduous species was also higher in the logged forest. Structural features such as number of trees and basal area were lower in the logged plots when compared to the unlogged forest. One way ANOVA and post-hoc Tukey test of species richness, density and basal area between logged and unlogged plots at 0.1 ha scale revealed that only a few pairs are statistically different. Species-area curves at 1 ha scale, species-individuals curves for 490 trees drawn randomly of each plot and cumulative species-area curves for logged and unlogged plots are compared. Floristic similarity between plots was analyzed using Sorensen similarity index and it displayed the lower index value for all the logged plots. Relative species abundance of each plot was obtained to understand the species compositional differences between the plots. Contribution of dipterocarps and non-dipterocarps trees for the density and basal area for small, medium and large trees between plots displayed a higher value for unlogged plots. The preliminary results of the present study indicated that the logged compartments are not yet recovered its status and it needs a greater recovery time.

Speaker

S. Jeyakumar, PhD student, IFP

Organisers

Department of Ecology, French Institute of Pondicherry.

Venue

Indology Hall (in front of Manuscript room), French Institute of Pondicherry, 11, Saint Louis Street, Pondicherry - 605 001.