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. VILLANUEVA1,♥, INOCENCIO E. BUOT, JR.1,2,3 1School of Environmental Science and Management, University of the Philippines Los Baños. College, Laguna 4031, Philippines. Tel.: +63-49-536 2836, ♥email: [email protected] 2Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños. College, Laguna 4031, Philippines 3Faculty 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 living in Mindoro Island. While it is evident that the flora in Halcon Range is Studying the structure of vegetation in tropical diverse and unique, there is no information on a detailed mountain areas has been of interest to many scientists, vegetation distribution and structure along the altitudinal especially to conservationists, because of its fascinating gradient of the Halcon range. Altitudinal zonation studies shifts of vegetation along elevational gradients. In Mt. will be of great help to conservation managers, as these Halcon, a tropical mountain located in Mindoro Island, studies provide a more detailed understanding of the Philippines, some studies were previously conducted about vegetation distribution as well as its interplay with the its vegetation. The oldest and most comprehensive of environmental factors. which were conducted during an exploration study during The vertical structure and distribution of vegetation has the early 1900s (Ames 1907; Brotherus 1907; Copeland been studied in the tropical mountains of the Philippines: in 1907; Merrill 1907a,b). In a more recent study (Mandia, Mt. Pulag (Buot and Okitsu 1998), Mt. Akiki (Buot 2007), 1998), the vegetation in the summit zone of Mt. Halcon Mt. Mayon (Buot 2008), Aborlan Guba System (Sopsop was explored. These researches have proven the unique and Buot 2011), Mt. Tabunan (Cadiz and Buot 2011), Mt. biodiversity of the mountain range, thus making it one of Pangasugan (Belonias and Aguilar 2004). These studies the Key Biodiversity Areas of the island (Ambal et al. emphasize the floristic characteristics of the Philippine 2012). tropical mountains, most of which were found to be similar Mt. Ilong is one of the peaks along the Halcon Range. with tropical mountains in the Malesian region (van Steenis Dutson et al. (1992) provided a description of the forests in 1964, Kitayama 1992, Aiba and Kitayama 1999). In Mt. Ilong. The lower edge of the forest begins at 750m. It another study in Mt. Makiling, the structure and was also recorded that there was an intensive pit-saw distribution of vegetation has been applied to observe the logging in the area (at 750-850 m), resulting to a severe land use type patterns (Buot and Osumi 2011). It has been damage in the forest at that time. The primary forest seen in the studies in the Philippine tropical mountains that occurred at 850-1000 m and above, which is a the anthropogenic disturbance can influence the vegetation lowland/mid-mountain transition type, with a canopy distribution and structure, leading to variation in land use reaching at approximately 15m. It then reaches its plateau types. at its peak (1,310-1440 m), with a stunted and uneven This study is an attempt to provide a comprehensive canopy with needle-leaved trees. Aside from its rich information on vegetation distribution plants in Mt. Ilong, biodiversity, this mountain is part of the ancestral domain Halcon Range, by analyzing the structure and dynamics of of the Alangan Mangyan, one of the indigenous groups its tree species distribution. Specifically, the study 2164 BIODIVERSITAS 19 (6): 2163-2174, November 2018 identified plant communities along the 100-1,400m communities in Paitan were described as more acculturated elevation through cluster analysis. Furthermore, selected than the other Alangan communities in Mindoro Island, environmental variables that influence species distribution these people have been working as swidden cultivators in were also investigated through canonical correspondence the lower slopes; while in the upper slopes towards its analysis (CCA). peak, they have retained their natural forests. From the higher to the lower elevations of Mt. Ilong, the Alangans obtain various valuable plant resources for their everyday MATERIALS AND METHODS living. Thus, the studying distribution of plants can be a valuable information to both the locals and conservation Study area managers. Moreover, plants can also serve as identifiers of This study was conducted along the altitudinal gradient community types across the elevational gradient of Mt. of Mt. Ilong, one of the peaks of the Halcon Range with an Ilong. elevation of approximately 1,440 masl (Dutson et al. 1992). Mindoro Island experiences two weather types under The highest peak in Mindoro Island is Mount Halcon the modified Corona’s classification: Type I and Type III. (2,582 m). It is situated near the middle of the island Type I, which is identified on the western side of the separating two geopolitical areas, namely the provinces of island, has two pronounced seasons: dry from November to Oriental and Occidental Mindoro (Figure 1). The foothold April and wet for the rest of the year. Type III, which is the of the mountain range is inhabited by the Alangan people, climate type on the eastern side, has no pronounced the local people of the area. maximum rain period, with a short dry season ranging from Mt. Ilong is part of Barangay Paitan, Municipality of one to three months, either during December to February or Naujan, Oriental Mindoro, Philippines. Paitan is considered from March to May. as the little town of the Alangan (Mandia 2004). While the Figure 1. The study area. The Philippine map is shown in the lower left with Mindoro Island emphasized in red box. Photo on the upper left shows a map of Mindoro Island with a more detailed location of Mt. Halcon and Mt. Ilong (marked as ▲). The positions of the sampling points are shown on the right, marked as red dots. Maps are generated using QGIS v.2.18.13. VILLANUEVA & BUOT – Vegetation analysis of Mt. Ilong, Mindoro Island, Philippines 2165 There is no available meteorological record monitoring The basal area was derived from the diameter at breast specifically for Halcon Range; however, some accounts by height (DBH) data of the trees using the formula: previous explorers have emphasized the very high humidity of the mountain, just like in other tropical mountains in the Philippines like Mt. Makiling and Mt. Pulag. Merrill (1907a,b) described Mt. Halcon as probably the most Where, d is equal to DBH (at 1.5m). For the herbs and humid mountain in the Philippines, with rains occurring for shrubs, the dominance was measured using cover, which is nine months every year (May to January). Because of this the percent area covered by each species in a quadrat. condition, the abundance of ferns, mosses, and epiphytes Instead of relative dominance, the relative cover was used are very remarkable, especially in the forest zones. The for herbs. summit zone, on the other hand, has a drier climate having All vascular plants were identified using keys and a temperature of around 16 °C, with mostly stunted botanical literature, except for epiphytes and lianas. The vegetation interspersed with patches of tall shrubberies and nomenclature follows that of Merrill (1923-1926), Pancho forested areas (Mandia 1999). (1983), Backer and Bakhuizen v.d Brink (1963-1968), Huang et al. (1993-2003), and Pelser et al. (2011-onwards). Field data collection The scientific names were also validated through the Field data collection was done during the first week of International Plant Names Index (IPNI 2015). May 2016. The vegetation sampling was conducted along