Woody plant community and distribution in a tropical coastal sand dune in southern Thailand

In this study, we aimed to clarify the forest structure and species composition of a coastal sand dune and the relationship between topographical factors and woody plant distribution at the Bang Boet coastal sand dune, Southern Thailand. Three permanent transect plots (10 × 100 m) covering both windward and leeward aspects were established 300 m apart. In subplots (10 × 10 m) of each transect, all woody plants with a diameter at breast height larger than 1 cm were tagged, measured, and identified. The topographic factors were recorded for each subplot. Non-multidimensional scaling was employed to analyse the woody plant distribution, which was tested for statistical significance. We identified 36 species from 32 genera and 23 families. Species diversity was moderate based on the Shannon–Wiener index (2.81). The density and basal area of all woody plants was 3110 ± 361 stem·ha⁻¹ and 7.34 ± 0.87 m²·ha⁻¹, respectively. The dominant trees species based on the importance value index were Pandanus odorifer, Syzygium antisepticum and Syzygium grande. The forest structure could be classified into two canopy layers, with an open and closed crown canopy on the windward and leeward aspects, respectively. Overall, the distribution of woody plants was significantly correlated with aspect. Species diversity, tree abundance, and basal area differed significantly between the windward and leeward aspects and quantitative values were low on the windward aspect. Due to strong winds and salt spray on the windward side, the woody plant community and distribution favoured the leeward side.