SPATIAL PATTERNS OF COMMON TREE SPECIES RELATING TO TOPOGRAPHY, CANOPY GAPS AND UNDERSTOREY VEGETATION IN A HILL DIPTEROCARP FOREST AT SEMANGKOK FOREST RESERVE, PENINSULAR MALAYSIA

Abstract

The spatial patterns of the 30 most common tree species and their associations with topography (ridge, slope and valley), canopy gaps, and understorey vegetation (bertam palm, Eugeissona tristis, and a common bamboo, Gigantochloa scortechinii) were analysed in a hill dipterocarp forest at Semangkok Forest Reserve, Peninsular Malaysia. We enumerated all trees ≥ 5 cm dbh and performed a census on the distribution of gaps, palm and bamboo in a 6-ha permanent plot. Most species showed significant aggregated patterns and only two species, Payena lucida and Scaphium macropodum, were randomly distributed through all quadrat sizes. Thirteen species showed significant positive association with topography; two species were associated with valley, ten species with ridge, and one species with slope. The 30 most common tree species were separated into three groups by a cluster analysis based on the dissimilarity index: D= (1-ω) /2, where ω is Iwao's co-index which reflects the degree of inter-species spatial association. Species group A (7 species) contained two randomly distributed valley species (Vitex longisepala and Crypteronia griffithit). Group (11 species) consisted of ridge species. Shorea curtisii, Lithocarpus wallichianus, Eurycoma longifolia and others were positively associated with typical ridge sites and/or the distribution of the palm. Group (12 species) consisted of slope species (Pimelodendron griffithianum), gap-associated species, (Macaranga triloba, Millettia atropurpurea and Knema conferta) and others. Gap species were also associated with bamboo. Distinctive habitat guild was recognised only on the ridge species.