SPECIES-AREA RELATIONS OF DRY DIPTEROCARP FOREST VEGETATIONS

Abstract

The relationships between number of species with DBH 4.5 cm and quadrat area of dry dipterocarp forest in comparison with dry evergreen forest by enlarging the quadrat size contagiously from 100 m² up to I ha were investigated at Sakaerat.  The studies showed that using a modified logarithmic series model of Fisher et al (1943) did not satisfactorily explain this relationship in both forest types owing to their species diversity indices changed as quadrat size enlarged and spatial distributions were not uniform but rather clumping.  Five regression models and two asymptotic models resembling the growth function models were applied to trace this relationship for the four stands of dry dipterocarp forest individually and average for the four stands and compared with that used for the dry evergreen forest. It was found that the exponential function model was well fitted to this relationship in all stands of dry dipterocarp forest but it was fitted to that of dry evergreen forest similarly as the power function model.