ECOLOGICAL STUDIES OF LEGUMINOUS TREE SPECIES IN DRY DIPTEROCARP FOREST I. Species Composition, Occurrence and Abundance

Abstract

Species compositon, occurrence and abundance of the leguminous tree species in dry dipterocarp forest were investigated from available literature relating to this forest type studies together with permanent sample plots located in the northeastern region of Thailand. Tree sizes were limited to DBH 2 4.5 and 10 cm. In the 16 sub-types of dry dipterocarp forest there are 1 11 species of leguminous tree of which the number of species increases with increasing total number of tree species in each sub- type. Their occurrence ranges are 2- 26 % with 0.001 - 26 % of abundance. Xylia xylocarpa was found to be widely distributcd in 13 sub-types while Pterocarpus macrocarpus and Dalhergia cultrata are in 9 sub-types and Sindora siamensis in 7 sub-types. Other leguminous tree species are found only in some sub-types and 6 species are exceptionally rare in which only a single species occurs in each sub- type. Ecological indices relating to species diversity, eveness, concentration of dominance and richness of the dry dipterocarp forest are found to be closely related to the total number of species presented and the leguminous tree species contribute to these indices according to their number of species and abundances in each sub-type of this forest.