BIODIVERSITAS ISSN: 1412-033X Volume 21, Number 9, September 2020 E-ISSN: 2085-4722 Pages: 3969-3981 DOI: 10.13057/biodiv/d210907 A checklist and conservation status of vascular plants in the Limestone forest of Metropolitan Ilocos Norte Watershed Forest Reserve, Northwestern Luzon, Philippines MAE ANN R. BATUYONG1,4,, MICHAEL A. CALARAMO2, GRECEBIO JONATHAN D. ALEJANDRO1,3 1The Graduate School, University of Santo Tomas, España Blvd., 1015 Manila, Philippines. email: [email protected] 2Northwestern University Ecological Park & Botanic Gardens. Airport Avenue, Bengcag, Laoag City, 2900, Ilocos Norte, Philippines 3College of Science and Research Centre for the Natural & Applied Sciences, University of Santo Tomas, España Blvd., 1015 Manila, Philippines 4Department of Biological Sciences, College of Arts and Sciences, Mariano Marcos State University, City of Batac, 2906, Ilocos Norte, Philippines Manuscript received: 8 June 2020. Revision accepted: 6 August 2020. Abstract. Batuyong MAR, Calaramo MA, Alejandro GJD. 2020. A checklist and conservation status of vascular plants in the Limestone forest of Metropolitan Ilocos Norte Watershed Forest Reserve, Northwestern Luzon, Philippines. Biodiversitas 21: 3969-3981. The Metropolitan Ilocos Norte Watershed Forest Reserve (MINWFR) is among the remaining intact limestone formations and a critical protected area in northwestern Luzon. There have been few published floristic studies despite its undeniable rich biological importance. Therefore, this paper primarily aims to provide a preliminary checklist of vascular plants in MINWFR and their conservation status. Consequent field visits and surveys were made from April 2019 to March 2020. Results revealed a total of 173 species distributed in 140 genera belonging to 59 families. The most represented families are Rubiaceae, Fabaceae, Orchidaceae, and Malvaceae. This forest supports 49% or 28.65 % local endemics, five of which are narrow endemics, namely Cyanometra warburgii, Pyrostria triflora, Syzygium ilocanum, Thrixspermum nicolasiorum, and Antirhea microphylla. The latter, however, extends up to Ilocos Sur. Based on IUCN criteria and DENR (Department of Environment and Natural Resources of Philippines) records, a total of 18 species are threatened, one species is recorded as critically endangered, five endangered, nine vulnerable, three other threatened, two near threatened, 55 as least concern, and the rest are not evaluated. Other noteworthy species present in the area are the two dominant endangered species, Podocarpus costalis, and Podocarpus polystachyus. An interesting spinescent Rubiaceae species were recorded and currently under examination to establish its identity. This checklist serves as a basis to effectively manage this vulnerable area surrounded by human-induced disturbances and threats. Keywords: Biodiversity, conservation, Ilocos Norte, Limestone forest INTRODUCTION biodiversity research and urgent consideration for protection is limestone ecosystem. It is identified as a The Philippines supports many endemic and various conservation focus for sustainability, especially that natural species from different ecosystems owing to its highly and anthropogenic disturbances are increasing (Sodhi et al. diverse topography, climate patterns, and complex 2010). The Philippines is endowed with about 11.7% or geological history (Myers et al. 2000; Yap 2010; Brown et extensive 35,000 km2 karst total land (DENR-BMB 2019), al. 2013; Dapar et al. 2020). It is listed as one of the but a large portion of this is still unknown to science. The megadiverse countries (DENR-BMB 2015; CI 2020). Philippines' Biodiversity Management Bureau recognized However, it is reported as one of the top countries affected the need for a strategic action plan to save and sustainably by biodiversity loss, thus making it one of the global managed this unique ecosystem as it hosts diverse flora and conservation priority areas (Rockstrom et al. 2009; fauna. The growing interest in this type of forest formation Mittermeier et al. 2011; CBD 2020). is because of its panoramic view, ecotourism and In the past years, there have been increased government recreational value, the potential discovery of new flora and initiatives recompensed by conservation successes such as fauna, the utilization of its mineral and aquifer resources, the establishments and declarations of Key Biodiversity and cultural importance. Areas (KBAs) and Protected Areas (PAs) as cornerstones Among the considered remaining intact and important to ensure biodiversity conservation in the face of threats limestone areas found in Luzon (Tolentino et al. 2020), is and pandemic we are experiencing (Sinsin 2012; DENR- the Metropolitan Ilocos Norte Watershed Forest Reserve BMB 2015). Sadly, due to incessant deforestation and (MINWFR). It is part of the Ilocos Mountains and exploitations of several crucial habitats, this has led the described as one of the critical ecosystems by Calaramo et country to be on the edge of ecological degradation and al. (2016). It has numerous cavern systems, and most of biodiversity collapse (Posa et al. 2008; Amoroso 2011; them contain subterranean rivers (DENR-MINWFR CBD 2020). One of the diverse types of forest ecosystems Management Plan 2018). Initially, it is established as a in the country that is gaining the need for top priority component by the National Integrated Protected Area 3970 BIODIVERSITAS 21 (9): 3969-3981, September 2020 System (NIPAS) through Presidential Proclamation No. MATERIALS AND METHODS 731, dated September 27, 1934, but currently, proposed to be a regular component. Study site Unfortunately, like any other area, its ecological aspects The study site is positioned geographically in the are also the most vulnerable and fragile (Brinkmann & Metropolitan Ilocos Norte Watershed Forest Reserve Parise 2012) and under immense pressure because of the (MINWFR), Municipality of Pasuquin, Province of Ilocos observed disturbances in all corners of the PA brought by Norte, Philippines (Figure 1). Based on the DENR human exploitation and numerous infrastructure (Department of Environment and Natural Resources of developments, aggravated by the harsh climatic condition. Philippines) cadastral survey, it has an estimated land area Meager information is also available about the richness and of 2,075 hectares with a buffer zone of 412 hectares. It lies status of plants existing in this area. Hence, this suggests an between geographical coordinates of 120° 37'00" -120° imminent need to perform a floristic survey to increase the 41'00" North and 18° 21'00" -18° 24'00" East. It covers plant diversity knowledge on this limestone forest. As Barangays Sapat, Tadao, Salpad, Sulbec, Sulongan, underscored by Ong et al. (2002), the conduct of floristic Susugaen, and Estancia. inventories through and mapping of habitat types must be The climate of MINWFR sits in the type 1 climate with undertaken, since these areas contain specific vegetation pronounced dry and wet season based on the Corona assemblages and may be very useful in predicting and Classification. There is a severe dryness during the summer validating plant distribution. Moreover, Stockli et al. months from January to May, which reaches a very high (2011) emphasized that they are crucial elements in the temperature (390C). The wet months from June to October monitoring of programs directed at looking into the effects transform the vegetation into greenery, where trees create a of climate change. thick canopy, and numerous seasonal herbs grow on its Further, they will serve as essential guides necessary rocky ecosystems. Tropical cyclones and storms for creating conservation plans and programs directed for occasionally visit the Municipality of Pasuquin during the policy formulation (Bacudo et al. 2006; UNEP 2012; southwest monsoon season (May to October), and it is most PCARRD 2017) and the practical management of the area dominant during July. Exposed to Southeast monsoon and in a way where potentially invasive species may be cyclonic rains, this area experiences prevailing wind efficiently identified, accordingly monitored, and properly blowing from north to south and sometimes west to east, contained. Thus, this study provides a preliminary checklist primarily when rainfall occurs. However, the area is of vascular plants, including their conservation status in the shielded from the northeast and trade winds by the limestone forest of MIWFR, Northwestern Luzon, Northern Cordillera Ranges. Philippines. Figure 1. Map of the study sites in Metropolitan Ilocos Norte Watershed Forest Reserve (MINWFR), Northwestern Luzon, Municipality of Pasuquin, Province of Ilocos Norte, Philippines. Surveyed areas are marked in green and red BATUYONG et al. – Checklist of vascular plants in MINWFR, Northwestern Luzon, Philippines 3971 MINWFR is generally mountainous with rugged Index, IPNI (https://www.ipni.org/). Online databases such terrain. Terrain ranges from 0-8% level to undulating, 8 - as The Global Biodiversity Information Facility 18% undulating to rolling, 18-30% rolling to hilly, 30-50% ((http://www.gbif.org/)) and Co's Digital Flora (Pelser et hilly to mountainous, and 50% very steep. The highest al. 2011 onwards) of the Philippines were used to identify elevation of the protected area is 539 meters above sea the occurrence and distribution of the plants collected. The level (asl). The highest altitude in the Municipality is 564 classification of the conservation status was based on the meters located