Species Diversity of Trees in Dry Dipterocarp Forest at Sakearat, Nakornratchasima II. Species Number and Species Diversity Expectations from Tree Individuals

Abstract

Species number expectation {E_(s)) using a rarefaction technique for the 4 stands of dry dipterocarp forest at Sakaerat Environmental Research Station Nakornratchasima, province separately and average for the 4 stands as compared to 1 stand of dry evergreen forest of the same locality and 2 stands of secondary and primary (shrine) dry dipterocarp forests at Don Pu Ta Somdet province was investigated by using standard sample size (n) of 10, 30, 50, 100, 300, 500, 700, and more tree individuals except for those stands with lesser abundant trees in which n was reduced to an appropriate size in the two periods of tree censuses in the permanent study plots. E_(s)) of each stand was further correlated with n and the two species diversity indices, Fisher (α) and Shannon and Weiner (H) then estimated. The study showed that E_(s) increased differently until attaining a ceiling at different n and both variables were well correlated in forms of logisitic, Gompertz and power function models for the 4 stands of different dominant species and 2 stands of secondary and primary forests during the two periods respectively. For the dry evergreen forest which a considerable large species number was expected during the two periods, it was well fitted by a logistic function model These E_(s) and a fixed standard sample size of 500 individuals per plot (n = 500) was then used to estimate the α and then the H indirectly and also changes of H of each stand according to time changes were further discussed.