Niche differentiation of Dipterocarpaceae and Fagaceae-a study in Asian rain forest-

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1. Research on Dipterocarpaceae at a tropical lowland rainforest of SarawakDistribution of 73 species and 9 subspecies of dipterocarps were analyzed in a 52 ha plot, and 73% of the examined species had distribution pattern depending on the topography. The fact suggest tht the topographical niche differentiation might contribute to enable the coexistence of dipterocarps in the plot. This analysis was also made for non-dipterocarp taxon, and same results were achieved. Canopy gap formation rate and recovery rate were estimated by using aerial photographs and by the land survey. There werer two types of gaps : one type was formed by the land slide associated with heavy rain and the other was formed by the tree falls. Two types of gap formation differed the frequency and recovery process and the various regeneration niches for the tree species were provided through two gap formation process. The contribution of the diversity of regeneration niche to the coexistence of tree species will be analyzed near future. Genetic analyzes were made for two species of genus Dryobalanops. Both of the species showed high genetic differentiation among the local populations located in 52 ha, indicating the high genetic diversity of the species. On the contrary, genetic distance between two sympatric species was quite small indicating niche differentiation and speciation of the two species had occurred recently.2. Research on Fagaceae at a montane rainforest of ThailandA research plot of 15 hapiot was established and the tree census in 7.5 ha area and identification in 3.0 ha area were completed. Gaps in 3.0 ha area was also mapped. Preliminary data analysis clarified that many Fagaceae species showed the distribution pattern associated with special topography or gaps. The niche differentiation among Fagaceae species will be analyzed qualitatively near future.