Tree Species Composition and Spatial Distribution in a Primary Lowland Forest of Sitio Inadan, San Miguel, Surigao del Sur, Philippines

This study assessed tree species composition and spatial distribution patterns within a 0.32-ha lowland dipterocarp forest in the Philippines. Eight 20 m × 20 m plots were established to document tree species meeting the minimum diameter criterion. Species richness, relative abundance, and selected structural attributes were calculated, and a chi-square test was applied to assess plot-level distribution patterns. A total of 14 tree species were recorded, including dipterocarps and other canopy-associated taxa, as well as shade-tolerant understory species and several light-demanding pioneer species. The presence of shade-tolerant families such as Fagaceae and Lauraceae indicates ongoing recruitment under closed-canopy conditions, while the occurrence of pioneer species suggests localized canopy openings within the sampled area. Distribution analysis showed that some species exhibited aggregated patterns, whereas others did not significantly deviate from random distribution. This indicates that certain species tend to cluster in areas with favorable environmental conditions or resources, while others are more evenly dispersed across the habitat. Given the limited sampling extent and number of plots, the findings are interpreted only at the scale of the study area and do not imply broader forest-level structural conditions. Although species richness was lower than typically reported for larger lowland dipterocarp forest inventories in the Philippines, the results provide preliminary insights into local stand composition and small-scale spatial structure.