| The objective of this study was to determine the distribution of species and species composition in relation to topographic factors and soil properties of dry dipterocarp forest in Doi Suthep-Pui national park, Chiangmai, Thailand. The data collections were conducted during two periods, June–July 1998 and March–August 1999. A total of 76 sample sites were selected, 45 and 31 of them were selected purposively and systematically, respectively. At each sample site a sample plot of 20m x 50m was established, and divided into ten of 10m x 10m subplots. Species and diameter at breast height (DBH) of all trees with DBH 4.5 cm and over were recorded separately in each subplot. Importance Values (IV) of species found in the sample plot were determined on the basis of their relative frequency, density, and dominance within the plot. Chemical and physical properties of soil samples were analyzed at Forest Soil Laboratory, Royal Forest Department in Bangkok, Thailand.; Purposive sampling provided more extensive variations in species composition. A total of 102 species was found in all sample plots. Ninety-four and seventy-seven species were identified from the purposively and systematically selected sample plots, respectively. Only sixty-nine of them were found by both sampling techniques. Based upon the contribution of IV more than 50% of the species having highest IV in the sample plot listed as dominant species, all thirteen dominant species were listed from purposively selected sample plots, while only six species were listed from systematically selected sample plots.; Most of one hundred and two species found in this study were minor stand components. Only ten species were found in more than 50% of the plots studied. However, some of these rarely found species were dominant in some particular sites, such as P. merkusii Jungh. & de Vriese, P. kesiya Royle ex Gordon which were found in the particularly high elevation.; Cluster analysis resulted in two major groups: five clusters of single dominant species and three clusters of multiple dominant species. Lithocarpus polystachyus Rehd., Dipterocarpus obtusifolius Teijsm. ex Miq., D. tuberculatus Roxb., Shorea siamensis Roxb., and S. obtusa Wall. dominated exclusively in the single dominant species group. Two or more species dominated about evenly in multiple dominant species clusters. By using General Linear Model; soil reaction (pH), potassium content (K), percentage of base saturation (BS), percentage of clay particles, and elevation were tested as being sensitive to the grouping. (Abstract shortened by UMI.)... |
