BIODIVERSITAS ISSN: 1412-033X Volume 19, Number 6, November 2018 E-ISSN: 2085-4722 Pages: 2163-2174 DOI: 10.13057/biodiv/d190624 Vegetation analysis along the altitudinal gradient of Mt. Ilong, Halcon Range, Mindoro Island, Philippines ELAINE LOREEN C. VILLANUEVA 1,♥ , INOCENCIO E. BUOT, JR. 1,2,3 1 School of Environmental Science and Management, University of the Philippines Los Baños. College, Laguna 4031, Philippines. Tel.: +63-49-536 2836, ♥ email: ecvillanueva4@up.edu.ph 2 Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños. College, Laguna 4031, Philippines 3 Faculty of Management and Development Studies, University of the Philippines Los Baños. College, Laguna 4031, Philippines Manuscript received: 8 May 2018. Revision accepted: 3 November 2018. Abstract. Villanueva ELC, Buot, JrIE. 2018. Vegetation analysis along the altitudinal gradient of Mt. Ilong, Halcon Range, Mindoro Island, Philippines. Biodiversitas 19: 2163-2174. The vegetation of Halcon Range is diverse, unique, and culturally important; however, there is a very limited information on its altitudinal distribution and structure, leading to the formation of land uses that trigger problem in sustainable management decisions for the mountain. This study analyzed the vegetation in land use types distribution along the altitudinal gradient of Mt. Ilong, Halcon Range, Mindoro, Philippines. Fourteen plots of 10 x 10m were established along the slope from 100m-1400m elevation. The tree species that were sampled from the plots were subjected to classification and ordination analyses. The dendrogram showed three distinct vegetation zones corresponding land use types: Zone I (agroforest land use zone), Lansium- Artocarpus-Swietenia-Ficus-Nephelium-Mangifera zone; Zone II (forest land use zone), Cyathea-Astronia-Syzygium-Garcinia-Ficus- Psydrax-Diplodiscus zone; and Zone III (forest land use zone), Agathis-Suli-Alitugba-Ardisia zone. Canonical correspondence analysis (CCA) indicated that elevation, temperature and pH level are the environmental variables that strongly influenced the vegetation distribution in various land uses, a characteristic that is similar to other tropical mountains. Keywords: Canonical Correspondence Analysis (CCA), cluster analysis, dominance analysis, Halcon Range, Mt. Ilong INTRODUCTION Studying the structure of vegetation in tropical mountain areas has been of interest to many scientists, especially to conservationists, because of its fascinating shifts of vegetation along elevational gradients. In Mt. Halcon, a tropical mountain located in Mindoro Island, Philippines, some studies were previously conducted about its vegetation. The oldest and most comprehensive of which were conducted during an exploration study during the early 1900s (Ames 1907; Brotherus 1907; Copeland 1907; Merrill 1907a,b). In a more recent study (Mandia, 1998), the vegetation in the summit zone of Mt. Halcon was explored. These researches have proven the unique biodiversity of the mountain range, thus making it one of the Key Biodiversity Areas of the island (Ambal et al. 2012). Mt. Ilong is one of the peaks along the Halcon Range. Dutson et al. (1992) provided a description of the forests in Mt. Ilong. The lower edge of the forest begins at 750m. It was also recorded that there was an intensive pit-saw logging in the area (at 750-850 m), resulting to a severe damage in the forest at that time. The primary forest occurred at 850-1000 m and above, which is a lowland/mid-mountain transition type, with a canopy reaching at approximately 15m. It then reaches its plateau at its peak (1,310-1440 m), with a stunted and uneven canopy with needle-leaved trees. Aside from its rich biodiversity, this mountain is part of the ancestral domain of the Alangan Mangyan, one of the indigenous groups living in Mindoro Island. While it is evident that the flora in Halcon Range is diverse and unique, there is no information on a detailed vegetation distribution and structure along the altitudinal gradient of the Halcon range. Altitudinal zonation studies will be of great help to conservation managers, as these studies provide a more detailed understanding of the vegetation distribution as well as its interplay with the environmental factors. The vertical structure and distribution of vegetation has been studied in the tropical mountains of the Philippines: in Mt. Pulag (Buot and Okitsu 1998), Mt. Akiki (Buot 2007), Mt. Mayon (Buot 2008), Aborlan Guba System (Sopsop and Buot 2011), Mt. Tabunan (Cadiz and Buot 2011), Mt. Pangasugan (Belonias and Aguilar 2004). These studies emphasize the floristic characteristics of the Philippine tropical mountains, most of which were found to be similar with tropical mountains in the Malesian region (van Steenis 1964, Kitayama 1992, Aiba and Kitayama 1999). In another study in Mt. Makiling, the structure and distribution of vegetation has been applied to observe the land use type patterns (Buot and Osumi 2011). It has been seen in the studies in the Philippine tropical mountains that the anthropogenic disturbance can influence the vegetation distribution and structure, leading to variation in land use types. This study is an attempt to provide a comprehensive information on vegetation distribution plants in Mt. Ilong, Halcon Range, by analyzing the structure and dynamics of its tree species distribution. Specifically, the study