Composition and stand structure of riparian forests of Kuala Keniam, Pahang National Park, Malaysia

Riparian forests are riverbank ecosystems that contain water-dependent woody plants. The forests are diverse in species, structure, regeneration process, and have important ecological functions in maintaining landscape and biodiversity. We assessed the species composition and stand structure of two riparian forests of differing distance from river edges (abbreviated as zone 1 and zone 2, respectively) in Kuala Keniam of Pahang National Park, Malaysia. Our objectives were to study the species composition and describe the stand structure of the forests. All trees with diameter at breast height (DBH) ≥ 10 cm were identified and measured in twelve 10 × 20 m plots in each study site. The species diversity, richness, evenness, abundance and important value index (IVI) were determined for each type of community. A student's t-test was used to examine differences in these variables between riparian zones. All species diversity indices measured did not differ significantly between the two study zones (P≥0.05). The dominant and co-dominant species present in zone 1 were Elateriospermum tapos and Lagerstroemia speciosa, respectively, whereas in zone 2 the dominant and co-dominant species were Durio zibethinus and Pterocymbium javanicum, respectively. There were no major differences in forest structure across the riparian study sites. The distribution of trees in both sites clearly displays the characteristic of De iocourt's factor procedure (inverse J distribution) where stem frequencies decrease with the increase in DBH. This generally indicates that stands in both riparian sites are developing and regeneration in the forests is present.