J. Bio. & Env. Sci. 2019 Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 14, No. 5, p. 135-141, 2019 http://www.innspub.net RESEARCH PAPER OPEN ACCESS Richness, endemism and conservation status of woody plants in the lowland forest over limestone of Northern Sierra Madre Natural Park, Northeast Luzon, Philippines MA. Visitacion*, D. Guingab Faculty of the College of Forestry and Environmental Management, Isabela State University, Garita, Cabagan, Isabela, Philippines Article published on May 30, 2019 Key words: NSMNP, Limestone forest, Species richness, Philippine endemics, Threathened species. Abstract The study was carried out to assess the woody species of the lowland forest over limestone in the Northern Sierra Madre Natural Park (NSMNP) in Palanan, Isabela, Northeast Luzon, Philippines in order to provide information of its floral diversity, endemism and conservation status. An updated species list was provided based on the recent field survey and analysis of herbarium records. A total of 138 woody species in 92 genera and 42 families were recorded consisting of three lianas, 34 shrubs and 101 small to large trees. The ten most speciose families were Meliaceae (13 spp.) Rubiaceae (8 spp.), Annonaceae (7 spp.), Ebenaceae (7 spp.), Fabaceae (7 spp.), Dipterocarpaceae (7 spp.), Myrtaceae (6 spp.), Primulaceae (5 spp.), Rutaceae (5 spp.), and Vitaceae (5 spp.). Genus Diospyros of the family Ebenaceae had the highest number of species (7) followed by genera Ficus (6), Shorea (5), Syzygium (5), and Leea (5). The most important species was Diospyros pyrrhocarpa Miq. Species endemism is very high, 41% (56) of the total number of species, nine (9) of which are single-island endemics known only to Luzon Island. Twenty-two (22) were threatened species, one being critically endangered, two are endangered, 15 are vulnerable and four are near threatened. The information provided is crucial in the management of the natural park, which requires serious monitoring and protection. *Corresponding Author: MA. Visitacion [email protected] 135 | Visitacion and Guingab J. Bio. & Env. Sci. 2019 Introduction Rainfall is more or less evenly distributed throughout The Northern Sierra Madre Natural Park (NSMNP) is the year with mean annual rainfall of 3,218mm and considered as the largest protected area in the annual totals ranging from 1,347 to 6,841mm and all Philippines and one of the least biologically explored months exceeding 100mm of rain. Seasonality is areas in the country with an approximate area of defined by the northeast monsoonal winds from 359,486 hectares. Reference to various vegetation November to June and the southeast monsoon from maps indicates that these forests probably form the June to November. Typhoons frequently come from largest remaining tract of tropical rainforest in the the northeast border with wind gusts up to 200kph. Philippines. The NSMNP is a composite of all major which have significant effects on the Palanan forest habitat types found in the country, from the marine through direct crown damage. and wetland habitat to the lowland dipterocarp forests and upper montane forests. Being exposed to the Pacific Ocean and subjected to the direct and adverse impacts of frequent tropical storms, the vegetation has distinct character and structure that makes it a home to a number of endemic and rare plants. Unfortunately, its rich biodiversity is under severe threat from extreme poverty of the local population which is directly influencing its degradation. At the present rate of exploitation of the commercial forest areas the virgin forest will be logged-over within several years. Botanically, this basically means these forested areas will be destroyed Fig. 1. Location map of the study area in NSMNP, before any inventory has been made of its Palanan, Isabela. biodiversity. Floristic assessment of the woody species of the NSMNP is extremely useful to The lowland forest over limestone commonly known strengthen biodiversity conservation and sustainable as Molave Forest occupies low limestone hills, either use of biological resources in the area. Moreover it coastal or bordering large uplifted river valleys which provides a basis for the present botanical knowledge are mainly composed of crystalline limestone covered which underpins further studies of the ecology and by a shallow or very thin soil. This formation is botany of the region. generally open, characterized by few scattered large trees often short-boled, irregular in form and with The study was conducted to assess the woody plants of wide-spreading crowns (Fernando, 1998). The NSMNP in Isabela Province as basis for its conservation. intervening spaces are often filled with small trees Specifically it aims to: a) describe the plant community and small erect bamboos. It occurs in regions where composition of the lowland forest over limestone; b) the dry season is very pronounced. The forest has determine the plant richness of taxa by family, genera deciduous foliage especially on rough topography. and species; c) determine plant endemism; and d) assess the conservation status of the species. The most extensive karst formation is found in the Materials and methods vicinity on the Three-Knobs-Kanaipang Area. To the Study Area north of this formation are minor patches that The study is located within the Northern Sierra interdigitate with the ultrabasic south of Palanan Point. Madre Natural Park in Isabela Province, Luzon, West of the Sierra Madre along the Disabungan River in Philippines (17º07' N and 122º32"E) near Palanan San Mariano is another extensive limestone formation Point (Fig. 1). The terrain is relatively rolling to hilly. but with largely degraded forest cover (Co et al., 2006). 136 | Visitacion and Guingab J. Bio. & Env. Sci. 2019 Plant composition is mixed with species of Diospyros, from the National List of Threatened Philippine Plants Shorea, Terminalia, Celtis, Syzygium, Mangifera, Ficus issued by the Department of Environment and Natural and a large number of herbaceous plants. Resources (DENR-DAO 2017-11). Floristic Inventory Results and discussion Floristic inventory was conducted by repeated transect Floristic Composition and Richness walks in Palanan, Isabela near Palanan Point. Ten A total of 138 woody species in 92 genera and 42 transect plots of 10 x 100m equivalent to 0.1ha per plot families were recorded in the NSMNP’s lowland forest were established. All plots were surveyed giving a total over limestone, consisting of three (3) lianas, 34 sample area of one ha. All the woody plants (lianas, shrubs and 101 small to large trees (Table 1). trees and shrubs) with girth at breast height (GBH) Likewise, the ground is rich with herbaceous flora above 2.5cm for trees and over one cm GBH for lianas suggesting that the area is rich in plant species within the plots were counted, numbered, pre- considering the very thin soil and crystalline identified and taken for sample. Voucher specimens limestone that holds the vegetation. Studies by Co et were deposited at the Isabela State University al. (2006) on other limestone forest in different sites Herbarium (ISUH) and duplicates were sent to the of the same area, revealed almost the same number of Philippine National Herbarium (PNH) and Naturalis genera and families (95 and 41, respectively) Biodiversity Center (NBC) in the Nethrlands. However, it is relatively lower in terms of number of species. The location of the study site which is Qualitative floristic measures of data were used to exposed to the direct hit of destructive typhoons may determine the species composition and level of plant account for the lower plant diversity when compared richness at species, genera and family levels. to other forest types in the same area such as in mixed Importance value index for each species was dipterocarp forest and the ultrabasic forest. calculated by determining the relative frequency, relative density and relative basal area of the species. Table 1. Species composition in the lowland forest over limestone of the Northern Sierra Madre Natural Collection, Processing and Identification of Specimens Park. Legend: t=tree, st=small tree, lt=large tree, Ten fertile samples and a minimum of three sterile s=shrub, l=liana). Common samples per species were collected and processed Name of Species Family Name Name using the wet method. Plants were dried at the 1. Aglaia argentea Blume Meliaceae Ilo-ilo (t) 2. Aglaia cumingiana Turcz. Meliaceae Alauihau (t) College of Forestry and Environmental Management. 3. Aglaia edulis (Roxb.) Wall. Meliaceae Malasaging (t) 4. Aglaia tomentosa Teijsm. & Binn. Meliaceae Karamiras (t) Herbarium specimens were deposited at the ISUH 5. Alangium villosum subsp. Cornaceae Malabulau (t) pilosum (Merr.) Bloemb. with duplicates at the PNH. 6. Albizia butarek sp. nov. nom. Fabaceae Butarek (t) 7. Allophylus cobbe (L.) Sapindaceae Mala-lagundi Raeusch. (t) All species were identified and verified using various 8. Antidesma ghaesembilla Phyllanthaceae Binayuyo (t) Gaernt. floral keys. Identification of specimens was confirmed 9. Antidesma tomentosum var. Phyllanthaceae Bignai-kalaw tomentosum Blume (t) by taxonomists at the Naturalis Biodiversity Center in 10. Archidendron scutiferum Fabaceae Anagap (t) (Blanco) I.C.Nielsen the Netherlands. Digitized voucher specimens are 11. Ardisia darlingii Merr. Primulaceae Barasingag (s) 12. Ardisia elliptica Thunb. Primulaceae Tagpo (s) available in Global Plants on JSTOR. 13. Ardisia