High Species Diversity of the Family Dipterocarpaceae in Mursala Island, Indonesia

Abstract

Known to have a long history of timber extraction, Mursala Island on the west coast of North Sumatra Province is a small island home to the endemic tree Dipterocarpus cinereus and many other Dipterocarpaceae species. In the present study, distance sampling using line-transect was used to assess the species diversity and population status of Dipterocarpaceae species on the Island. A total of 26 Dipterocarpaceae species from 6 genera was identified from Mursala Island. The genus that was represented by the highest number of species was Shorea (13 species), followed by Vatica (5), Dipterocarpus (4), Hopea (2), Cotylelobium (1) and Dryobalanops (1). Among these, two Mursala Island endemic were identified: D. cinereus and H. bancana. Furthermore, according to IUCN Red List category, 11 species (42.3%) were classified as critically endangered, four species (15.4%) were of endangered, 5 species (15.2%) were of vulnerable, one species was of near threatened, 2 species were of least concern and 3 species were not assessed yet. Based on distance analysis, the species with the highest individual density was S. multiflora (21.72±10.96 individual/ha), whereas species with the lowest density was S. johorensis (0.06±0.01 individual/ha). Two main threats for Dipterocarpaceae species in Mursala Island were observed during the survey: illegal logging and habitat conversion. Increasing the protection level of the island was recommended to conserve all the species of Dipterocarpaceae. Besides, providing alternative sources of living for the illegal logger through commercialization of non-timber forest products, ecotourism, and the sustainable fishery was recommended so that they could stop illegal logging activity.