We investigated and compared the tree species composition and diversity of different forest types in Setiu Wetlands and on the three major islands of Terengganu. A total of 24 plots of 25 m × 25 m with four plots in each study site were established, viz. Melaleuca swamp forest in Kampung Fikri, freshwater swamp forest in Kampung Gong Batu, mangrove forest in UMT Setiu research station, and the islands, namely Pulau Bidong, Pulau Redang, and Pulau Perhentian. We calculated the basal area, stand density, Importance Value Index, species diversity, and above-ground biomass in the designated study areas. We assessed 139 tree species from 96 genera and 50 families based on a total of 2608 tree samples of 5 cm DBH and above. The freshwater swamp forest harbored the highest number of species with 20 species in Setiu Wetlands, and among the islands, Pulau Redang had the highest with 56 species. Melaleuca cajuputi was the most dominant species in the Melaleuca swamp forest, while Alstonia spatulata and Rhizophora apiculata are expected in the freshwater swamp and mangrove forest, respectively. Pulau Bidong, Pulau Redang, and Pulau Perhentian are mostly represented by Licania splendens, Shorea glauca, and Vatica sp., respectively. All the dominant species but Licania splendens contributed to the highest amount of above-ground biomass. Our current study indicated that different forest types vary in composition and structure, which may contribute to their unique ecological roles within their specific environment.

Forest structure, diversity and above-ground biomass assessment are important to understand the structural and floristic dynamics of a mangrove forest ecosystem. Our study provides valuable comparative analysis between two areas of disturbed mangroves at Kisap Forest Reserve, Langkawi Island. The two study sites were swamp forest at C5 which was disrupted by harvesting activities for charcoal production and C7 was disturbed by lightning strikes. A total of 1,217 and 390 trees measuring 1 cm diameter and above were enumerated in 0.25 ha plots at both sites. Seven mangrove plant species in C5 and eight in C7 were recorded. Ceriops tagal and Rhizophora apiculata were the most prominent species in the C5 and C7, respectively, whereby the Rhizophoraceae was the densest family at both sites. The major contributor of total basal area at C5 and C7 were C. tagal (5.02 m 2 /ha) and R. apiculata (11.14 m 2 /ha). Similarly, C. tagal (22.41 t/ ha) and R. apiculata (111.75 t/ha) also contributed the highest biomass in C5 and C7, respectively. Diversity and species richness were higher at C7 H'=1.22; R'=1.17 compared to C5 H'= 0.76; R'=0.85 and low evenness at both sites. High similarity was indicated between the two sites by 93%. The distribution of individuals in C7 was homogenous than that of C5, which had more saplings. In conclusion, anthropogenic activities resulted in lower productivity of forest compared to natural disturbances.

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