BioSMART ISSN: 1411-321X Volume 6, Nomor 1 April 2004 Halaman: 33-38  2004 Jurusan Biologi FMIPA UNS Surakarta ♥ Correspondence address: UPT Balai Konservasi Tumbuhan Kebun Raya “Eka Karya” Bali – LIPI. Candikuning, Baturiti, Tabanan, Bali 82191. Tel. & Fax.: +62-368-21273. e-mail: direkbg@singaraja.wasantara.net.id Flora of Alas River Bank, Ketambe, Gunung Leuser National Park EDY NASRIADI SAMBAS 1 , MUSTAID SIREGAR 1,2,♥ 1 Botany Division, Research Center for Biology-LIPI, Bogor 16002 2 “Eka Karya” Botanic Garden-LIPI, Tabanan-Bali 82191. Received: 3 November 2003. Accepted: 15 December 2003 ABSTRACT Flora of Alas River Bank Forest, Ketambe, Gunung Leuser National Park was studied by using plot method. Number of species of tree more than 10 cm in dbh (diameter at breast height) within 1 ha plot was 111 species belonging to 60 genera and 34 families. The density and basal area was 546 trees/ha and 30,76 m 2 /ha. Five most important species were Dendrocnide stimulans, Paranephelium nitidum, Pometia pinnata, Bombax ceiba, and Aglaia odoratissima, whereas five most important families were Meliaceae, Sapindaceae, Euphorbiaceae, Urticaceae, and Myrtaceae. Only Dendrocnide stimulans and Paranephelium nitidum have good regeneration, while the regeneration of emergent trees species (Pometia pinnata and Bombax ceiba) was not good. The forest regeneration was dominated by secondary species. Key words: Flora, Alas River, Ketambe, Gunung Leuser. INTRODUCTION Gunung Leuser National Park with the area of 862,975 ha (Decree of Minister of Forestry No. 096/Kpts/II/1984) and expanding to become the Leuser Ecosystem with the area of 1.8 million Ha (Decree of Minister of Forestry No. 227, Year 1998) is one of the largest conservation area in Sumatra. The Leuser Ecosystem perhaps the only area inhabited by rhinos, elephants, Sumatran tigers, and orang utans in the amount of able to guarantee their survival, but the current population is becoming critical (Leuser Development Program, 1996). Administratively, Gunung Leuser National Park, which crosses along 1,292 km, belongs to Aceh and North Sumatra Provinces. The area is on 96°30’- 98°30’ East Longitude and 2°55’- 4°05’ North Latitude with a flat, hilly to mountainous topography, and has altitude between 0-3,500 m asl. (Anonymous, 1997). Presently, Gunung Leuser National Park has been under heavy pressure from logging and encroachment, as well as forest opening for agriculture and settlement. There must be great efforts on forest inventory and ecological studies before this biodiversity resource extinct. The purpose of this study was to describe the structure and composition of a riverine forest within the Ketambe Research and Conservation Education Station, adding to the study of Abdulhadi (1991), Abdulhadi and Yusuf (1991), and Abdulhadi et al. (1989, 1990, 1991, 1996), and perhaps it will provide a contribution for a sound management of this National Park with the latest floristic data especially on the knowledge and information about the phytosociology of the riverine forest. Figure 1. Map of Ketambe Research and Conservation Education Station, Southeast Aceh.