Tree Species Composition and Diversity in Calatrava–San Andres–San Agustin (CALSANAG) Watershed Forest Reserve, Tablas Island, Philippines

The complex geological and biogeographical history of Tablas Island, which belongs to the Romblon Island Group, and the ongoing illegal activities in the area, may have influenced the present condition of the island’s floral diversity. However, information about the flora of Tablas, particularly trees, is less common compared with the other plant groups/growth forms. Here the tree species composition and diversity in CALSANAG Watershed Forest Reserve on Tablas Island were assessed to provide implications for conservation. A 2-hectare permanent biodiversity monitoring area (PBMA) was established on the island, and further divided into 200 plots, from which twelve plots were randomly selected. Ninety-four tree species belonging to 76 genera and 44 families were identified. Tablas Island has an average computed diversity value of 3.12 (i.e., high species diversity). Thirty species are Philippine tree endemics, of which eight species are potential new province record and six species were threatened. Our study should serve as baseline information which is important for the creation and implementation of conservation programs on the island. However, regular vegetation monitoring is highly recommended for better understanding of the floral resources on the island using the established PBMA.

Keywords: tree diversity; CALSANAG Watershed, Shorea polysperma, Tablas Island