BIODIVERSITAS ISSN: 1412-033X Volume 19, Number 2, March 2018 E-ISSN: 2085-4722 Pages: 496-503 DOI: 10.13057/biodiv/d190217 Tree species composition and structure of dry forest in Mutis Timau Protected Forest Management Unit of East Nusa Tenggara, Indonesia AAHAAH AHMAD ALMULQU 1,2,♥ , NOULKAMOL ARPORNPONG 3 , JARUNTORN BOONYANUPHAP 3♥♥ 1 Graduate School of Naresuan University. 99 moo 9 Tapho, Phitsanulok-Nakornsawan Rd., Phitsanulok, 65000 Thailand. Tel.: +66-5596-8821, Fax.: +66-5596-8829, ♥ ahmadalmulqu@yahoo.com 2 Politeknik Pertanian Negeri Kupang. Kupang 85011, East Nusa Tenggara, Indonesia 3 Faculty of Agriculture Natural Resources and Environment, Naresuan University. Muang, Phitsanulok 65000, Thailand, ♥♥ email: charuntornb@nu.ac.th Manuscript received: 6 September 2017. Revision accepted: 27 February 2018. Abstract. Almulqu AA, Arpornpong N, Boonyanuphap J. 2018. Tree species composition and structure of dry forest in Mutis Timau Protected Forest Management Unit of East Nusa Tenggara, Indonesia. Biodiversitas 19: 496-503. Plots 10,000 m 2 were established in four sites of Mutis Timau Protected Forest Management Unit (Mutis Timau PFMU), in order to determine tree species density, basal area, importance value index, species richness and to identify the relationship betwen species richness and abundance of trees. A total of 94 species belonging to 72 genera and 45 families were recorded. Species richness and forest structure were different between sites. Moraceae was the dominant tree family at most sites, particulary for Eucalyptus urophylla. The results suggest controlling the number of species, level on species distribution pattern, silvicultural interventions to pioneer species through thinning liberation, seeding and planting (pioneer species) could accelerate the tree regeneration of Mutis Timau PFMU in Kupang District, East Nusa Tenggara Province, Indonesia. Keywords: Forest structure, Mutis Timau PFMU, silvicultural interventions, species diversity, species richness, species abundance INTRODUCTION Dry tropical forest communities are among the world's most threatened systems and urgent measures are required to protect and restore them in degraded landscapes (Sagar and Singh 2006). Tropical dry forests, the most endangered and probably the most fragmented lowland forest in the tropics (Janzen 1988), have relatively low species diversity (Gentry 1995) and the trees are particularly vulnerable compared with other plant forms because they take a long time to reach reproductive age. They are also associated with low productivity, high mortality rates, increasing demand for food and energy and declining land productivity (FAO 2009). For planning conservation strategies, there is a need to determine the few essential measurable properties, such as number of species and basal area, that best describe the dry forest vegetation and its environment, and to document quantitative relationships among them (Sagar and Singh 2006). According to Sagar et al. (2003), biodiversity inventories are used to determine the nature and distribution of biodiversity resources of the forests to be managed. Information from this quantitative inventory will provide a valuable reference for forest assessment and improve our knowledge by the identification of ecologically, useful species as well as species of special concern, thus identifying conservation efforts for sustainability of forest biodiversity (Naidu and Kumar 2016). Information on composition, diversity of tree species and species-rich communities is primary importance in the planning and implementation of biodiversity conservation efforts (Suratman 2012). For a good forest conservation plan, understanding tree species composition and knowledge of the forest stand structure is necessary (Farhadi et al. 2013). Because trees, an important component of vegetation, must be constantly monitored and managed in order to direct successional processes towards maintaining species and habitat diversity (Attua and Pabi 2013). Variables that influence the tree species diversity are climate, stand structure, species composition, and geomorphology. Forest stand structure is a key element in understanding forest ecosystems and also an important element of stand biodiversity (Ozcelik 2009). Until today, only little published scientific information on the tree species composition and structure in the dry forest of Mutis Timau Protected Forest Management Unit (Mutis Timau PFMU), although biodiversity conservation in Mutis Timau PFMU received attention from the central government, local government and international conservation agencies. Such surveys by the Food and Agriculture Organization of the United Nations, in collaboration with the Department of Forestry’s Directorate General of Forest Protection and Nature Conservation, identified priority areas for conservation in 1980 (MacKinnon et al. 1982). Only one detailed study on Eucalyptus urophylla forests, using floristic and structural data, was conducted at Mutis Timau dry forest (Robinson and Supriadi 1981). Here, we report on the tree species community and forest structure of dry forest in Mutis Timau PFMU. The study aims (i) to identify and inventory tree species in