ECOLOGICAL STUDIES OF LEGUMINOUS TREE SPECIES IN DRY DIPTEROCARP FOREST II. Species Abundance Distribution Pattern in the Growing Habitat

Abstract

Investigations on species abundance pattern of leguminous and other tree species in 16 sub community types of dry dipterocarp forest (DDF) were carried out by applying the goodness of fit test (X²-test) of the logarithmic series (LS) and / or geometric series (GS) to each stand after calculating the Fisher's index of species diversity (α). It was found that 46 stands were well fitted to the LS with 38 stands for trees with DBH ≥ 10 cm and 8 stands for trees with DBH ≥ 4.5 cm while 16 stands were clearly fitted to the GS with 13 and 3 stands for the former and latter size classes respectively showing the corresponding well to the niche pre-emption hypothesis with unseparated clear cut of habitat requirement among the leading component tree species except for stands containing trees in other family rather than the Dipterocarpaceae distributed on the relatively high altitudes. The 21 leguminous tree species growing in dry dipterocarp forest were found to distribute with low-moderate abundance classes in the LS and GS patterns for both size classes. Only two leguminous tree species, Plerocarpus macrocarpus and Xvlia xylocarpa were found particularly in high abundance class for both sizes. The findings suggested that in overall, leguminous tree species in DDF are moderately rare and may require some specific habitat with moderate resource allocation.