COMPOSITION, POPULATION STRUCTURE AND DISTRIBUTION OF DIPTEROCARPS IN A TROPICAL EVERGREEN FOREST AT VARAGALAIAR, ANAMALAIS, WESTERN GHATS, SOUTH INDIA
Keywords:Dipterocarpaceae, permanent plot, Western Ghats, evergreen forest, stand structure, tree dispersion, dipterocarp domain
The diversity, density, basal area, population structure and spatial distribution of all dipterocarps (≥ 10 cm dbh) was investigated in a 30-ha permanent plot
of tropical evergreen forest at Varagalaiar, Anamalais, Western Ghats, south India. Dipterocarpaceae in our site was represented by three species, Dipterocarpus indicus, Hopea parviflora and Valeria indica. These contributed 2% of tree species richness, 6.8% of stand density and 18.3% of stand basal area. The density of dipterocarps in each hectare of the present study site varied greatly, ranging from 7 to 62 trees with a mean density of 31 trees ha-1. Dipterocarpus indicus was the most abundant species accounting for 59% of dipterocarp density. Of the 51 tree families encountered in the 30-ha plot, dipterocarp species ranked first in basal area because of their greater girth frequency in the larger girth classes. Population structures of the three dipterocarp species obtained based on the number of individuals in each diameter class displayed a greater proportion of individuals in the lower
size class. Spatial patterns of all dipterocarp species and their three stem sizes analysed at 1 ha, 0.5 ha and 0.25 ha scales revealed that individuals were dispersed both in clumped and uniform patterns, except V. indica which was randomly distributed in one subplot at the 1-ha scale.