Habitat Differentiation and Trait Variation Across Disturbance Gradients in Coastal Plant Communities of the Andaman Coast, Thailand

Coastal sand dune ecosystems play a crucial role in ecological functions and biodiversity support. These ecosystems are shaped by complex environmental gradients and disturbance regimes that are difficult to quantify directly. However, tree communities in tropical Asian dunes remain poorly understood. Here, we examined tree community composition and functional traits as integrative responses to underlying drivers across 24 plots arranged along transects extending inland from the shoreline at Hat Thai Mueang Coastal Sand Dune, Thailand. We measured structural attributes, diversity metrics, and community-weighted mean (CWM) functional traits and analyzed community composition using Bray-Curtis dissimilarity. Four distinct habitat types were identified, with distance from the sea emerging as the primary axis of community differentiation. Differences among habitats were consistent with inferred variation in hydrological regimes, particularly in an inland swamp subject to seasonal flooding. This inland swamp exhibited high wood density and low species diversity, suggesting strong environmental filtering under seasonally inundated conditions. In contrast, habitats outside the seasonally flooded swamp supported higher species diversity and lower wood density. Our findings indicate that coastal dune tree communities are structured by interacting disturbance regimes across environmental gradients, with wood density emerging as an important indicator of community assembly. These patterns can inform management strategies to maintain biodiversity and ecosystem resilience in protected coastal landscapes.