Some threatened woody plant species recorded from forests over limestone of the Philippines

: This study was conducted to determine threatened woody plants in forests over limestone in Samar Natural Park (SINP), Guiuan Marine Resource Protected Landscapes and Seascapes (GMRPLS), and other areas in the Philippines, in order to design a strategic framework for sustainable conservation of threatened species. Combined fieldwork using standard vegetation techniques and comparative literature review were done. Results revealed a total of 196 woody plant species belonging to 48 families, with 60 (DAO 2017-11) and 182 (IUCN) threatened woody plant species in the forests over limestone. The top 10 important species noted include three Critically Endangered: Diospyros longiciliata Merr., Cynometra cebuensis Seidenschwarz, F., and Shorea astylosa Foxw; three Endangered: Cinnamomum cebuense Kosterm., Tectona philippinensis Benth. & Hook.f. and Vitex parviflora Juss.; and four Vulnerable species: Agathis philippinensis Warb., Aquilaria cumingiana (Decne) Ridley, Dipterocarpus gracilis Blume, and Shorea polysperma (Blanco) Merr. A framework for sustainable conservation has been designed to prevent the loss of these threatened botanical treasures.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print)  (Day & Urich 2000). Tropical forests over limestone occur in southern Mexico, central America, the Caribbean, and southeastern Asia including the Philippines, which have roughly 35,000 km 2 of karst forests (Piccini & Rossi 1994). Generally, plants experience more stress in this type of forest due to shallow soil substrates, high temperature, and other limiting factors. Hence, unique plants abound and are expected to possess secondary metabolites with high potential against stressors. Plants in forests over limestone are valuable sources of wood and non-wood products for nearby village communities. They also serve as food, medicine, shade plants and perching materials for local fauna and forest pollinators, sustaining life cycles, and ecosystem dynamics. Anthropogenic pressures can result in overharvesting, deforestation, and biodiversity loss.
Karst forests in the Philippines harbor rich biodiversity, but some are also threatened due to human pressures. These include Mount Lantoy in Cebu Island, one of the 117 terrestrial areas designated as Key Biodiversity Areas (KBA) based on vulnerability and irreplaceability criteria (Lillo et al. 2019(Lillo et al. , 2020(Lillo et al. , 2021. The area has two Critically Endangered, two Endangered, four Vulnerable, and 16 restricted-range species (CI/DENR-PAWB/Haribon 2006). In another site Cadiz & Buot (2009, 2010 assessed the native trees and woody plants in Cantipla and Tabunan forests in Cebu City. The Cantipla forest clusters were once a continuous forest cover that was part of the Central Cebu National Park (CCNP) and the Kotkot-Lusaran Watershed. On the other hand, the Tabunan forest covers at least 40 ha and is the only large patch of natural virgin forest left in Metro Cebu Watershed and the home to the endemic but threatened Cinnamomum cebuense (Quimio 2006). Another unique forest over limestone is found along Verde Island Passage, Batangas, Luzon Island where the endemic Philippine teak, Tectona philippinensis Benth. & Hook.f., is a dominant component (Caringal et al. 2019(Caringal et al. , 2021. One of the most extensive forests over limestone in the Philippines is in Samar Island Natural Park (SINP) and Guiuan Marine Resource Protected Landscapes and Seascapes (GMRPLS). A number of studies have shown that these areas are rich in biodiversity Tolentino et al. 2020;Madera et al. 2021;Obeña et al. 2021;Villanueva et al. 2021a,b;Tandang et al. 2022). In a series of biodiversity assessments conducted in various municipalities of Samar Island, it was revealed that the municipality of Paranas has been recorded to have 99 plant species from 63 genera and 44 families (Villanueva et al. 2021a). Furthermore, the municipality of Basey has a total of 67 plant species representing 54 genera and 38 families (Villanueva et al. 2021b), and 30 floral species representing 22 genera and 18 families were recorded in Taft, Eastern Samar (Obeña et al. 2021). Fernandez et al. (2020) recorded 41 floral species belonging to 17 families and 24 genera from Calicoan Island in Guiuan, eastern Samar.
Samar Island, specifically the SINP and the GMRPLS, have been severely degraded despite enforced protective policies such as the National Integrated Protected Areas System (NIPAS) Act of 1992. In the last 70 years, there has been significant logging and forest clearing for agricultural purposes in the area (UNDP-GEF 2014). Other threats (SEARCA 2004), include coal and chromite mining, unregulated limestone quarrying, charcoal production, over-harvesting of non-timber forest products (including rattans), pollution from industries, alien species invasion, and the proliferation of small-scale illegal logging. These activities contribute to forest destruction and pose a significant threat to the biodiversity of the island's forests over limestone ecosystem. If current trends continue, these activities could have serious consequences for both plant populations and the livelihoods of the people who rely on forest resources. Unfortunately, species decline from various locations throughout the country has not yet been documented for inclusion in the Philippine red list or the IUCN. Hence, the need to investigate the threatened woody plants in forests over limestone and their conservation status and catalyze additional actions and potentially save a species from extinction (Zahler & Rosen 2013), particularly in areas where future plant species endangerment is expected to be high (Giam et al. 2010). The study specifically aims to: 1) determine the threatened woody plants species in forests over limestone in Samar Island and in other parts of the Philippines and 2) design a strategic framework for sustainable conservation of forests over limestone threatened species.
Information on threatened woody species in limestone forests in the Philippines is critical because it can have a direct impact on human well-being and will help decision makers and stakeholders in better understanding the significance of this study in achieving the United Nations Sustainable Development Goals, J TT specifically, SDG 1 (no poverty), SDG 6 (clean water and sanitation), SDG 8 (decent work and economic growth), SDG 11 (sustainable cities and communities), SDG 12 (responsible consumption and production), SDG 13 (climate action), and SDG 17 (partnership to achieve the goal).

The study sites
The primary study area inventoried. Samar Island is the third-largest island in the Philippines archipelago, covering an area of 13,107 km 2 and extending between 10. 75-12.75 °N & 124.25-124.75 °E (PhilGIS 2016). The island is considered a botanical diversity hotspot in both the country and the Malesian region (Madulid 2000).
SINP ( Figure 1) contains 333,300 ha of the protected area and 125,400 ha of buffer zone, making it the Philippines' largest terrestrial protected area (UNDP-GEF 2014). The park was designated as a forest reserve in 1996, but it was elevated to the status of a natural park in 2003 by Presidential Proclamation No. 442 in accordance with Republic Act No. 7586 (NIPAS Act of 1992). The SINP is situated in Samar island's low rugged central mountain range, which is shared by all three provinces on the island. SINP is made up of 13 municipalities and one city in the province of Samar, 19 municipalities in the province of Eastern Samar, and five municipalities in northern Samar. The interior natural habitats of Samar Island are dominated by lowland evergreen rainforests and limestone forests (UNDP 2007;Taylor et al. 2015). It also has an interior highland with distinct accordant peaks and a surrounding limestone or karst terrain. The landscape in the southern part is made up of junglecovered limestone ridges. Its geology is predominantly Miocene and Holocene, with a sedimentary formation composed of basement rocks and overlying clastic rocks or limestone (Patindol 2016). It has high biodiversity and is a center of plant and animal diversity and endemism in the Philippines, home to several threatened species from the Eastern Visayas and Mindanao biogeographic regions (Madulid 2000).
GMRPLS (Figure 1), is a protected area located off the coast of the municipality of Guiuan situated in the Province of Eastern Samar, Philippines. It was designated as a protected area by virtue of Presidential Proclamation No. 469 in 1994 and consists of the following islands: Calicoan, Manicani, Suluaan, Tubabao, Victory, Homonhon, and other smaller islands and their surrounding reefs. It also includes the coastal area of mainland Guiuan, which totals 60,448 ha. The land that is now part of the conservation area was previously designated as a Marine Reserve and Tourist Zone in 1978, and it was placed under the administration and control of the Philippine Tourism Authority. It was reproclaimed and re-classified as a protected landscape/ seascape in 1994 under the National Integrated Protected Areas System Act of 1992.
Based on Modified Corona's Climate Classification, Samar Island is divided into two regions. The northeastern part manifests the Type II climate which has no dry season and has a pronounced rain period, particularly during December and January. The southeastern region has a Type IV climate, with rainfall distributed fairly evenly throughout the year. Throughout the year, the island has a humid climate (Kintanar 1984).
Other forests over limestone cited. Other forests over limestone were cited in available literature and included in the analysis ( Figure 2). These are Cantipla forest (Cadiz & Buot 2009) and Mount Tabunan (Cadiz & Buot 2010) of Cebu City, Mount Lantoy of southern Cebu (Lillo et al. 2019(Lillo et al. , 2020(Lillo et al. , 2021, and the coastal landscapes and seascapes of the Verde Island Passage, Batangas, southern Luzon (Caringal et al. 2019(Caringal et al. , 2021. Like the SINP and the GMRPLS, these other forests over limestone were threatened. Mount Lantoy forests declined significantly during the Spanish colonial period to provide lumber for the construction of Spanish galleons (Asia Magazine 1984). Recently, Bensel (2008) reported that agricultural expansion and fuelwood gathering are still increasing -putting pressure on this Cebu's last remaining forests. Respondents also reported illegal logging, hunting, and widespread conversion of forests to agriculture. Despite these, Mount Lantoy KBA is rated moderately disturbed according to the Beynen & Townsend (2005) scoring system. This means that the recorded disturbances and threats in the area do not have critical effects yet on species diversity for the time being. It could not, however, deny the deterioration of native trees that affects the biodiversity, the ecosystem, and the community surrounding Mount Lantoy KBA.
Similarly, even though Cantipla forest was part of the CCNP and Tabunan forest is in the strict protection zone, their forest resources are still being exploited by the local residents. On its first botanical survey in May 1970, most of the dipterocarp forests in Cantipla had already been destroyed (Colina & Jumalon 1974), and the destruction was accelerated due to the widespread practice of swidden agriculture. Similarly, there is occasional tree cutting and rattan harvesting within the Tabunan forest, and its forest exterior is dominated by J TT

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agricultural activities of the local residents. In fact, these activities contributed significantly to the reduction of the forested area by approximately 0.3% of its original forest cover (SSC 1988), which is mostly confined to rocky limestone cliffs.
Tectona philippinensis in the forests over limestone along Verde Island Passage, Batangas is an endangered species that has long been regarded as one of the most important floristic elements of this coastal forests over limestone (Madulid & Agoo 1990;DENR-UNEP 1997;Cordon et al. 2004). The tree is also an iconic species, a living witness to the Filipino people's economic and political history, as its wood was once used to repair galleon ships that plied the Manila-Acapulco route during the Spanish colonial era (ERDB 1998). Meanwhile, the number of remaining Philippine teak populations is decreasing due to rapid and continuous destructive human disturbances in the area. Land conversion (from forest to sugar apple plantation and coastal area to resorts), habitat destruction, ecotourism projects, quarry operation, development of road networks and lateral expansion of urban settlements, kaingin (slash and burn farming), accidental fire during summer months, and natural threats such as prolonged droughts caused by the El Nino phenomenon and pests and diseases are threats documented by Caringal (2004) and RDC-CALABARZON (2006).

Inventory of the woody species composition
The study was carried out through a combination of fieldwork using standard vegetation techniques in Samar Island, and extensive literature review of papers in forests over limestone in the Philippines. Two sets of field sampling methods were used to determine the plant composition. The quadrat or plot method (Mueller-Dombois & Ellenberg 1974) was used to assess trees (≤1 m) while the line intercept technique was used for understory species. The plots were purposely selected based on the heterogeneity of the plants and the presence and absence of human-related disturbances in the area. To assess the woody plant species, 27 20 x 20 m plots were established in SINP and GMRPLS last October 2019. Generally, 20 m is the longest distance that can be accurately surveyed in a dense forest (Dallmeier 1992). Two line transects, 5 m in length and subdivided with 1 m intervals, were established inside each sampling plot. Altitude and geographic location of each plot and plant species were determined using a geographic positioning system (GPS) device.

Determining threatened taxa
The conservation status of woody plant species was determined using the list of threatened species identified by the Philippines' DENR Administrative Order No. 11 series of 2017 (DAO 2017) and the International Union for Conservation of Nature (IUCN) (IUCN 2022). DAO No. 2017-11 (DAO 2017 is the national reference for threatened species of the Philippines. This is being used by researchers and planners as basis in decision-making related to forest management and conservation. IUCN (IUCN 2022), on the other hand, is the global reference for threatened species of various countries. So, in this study, we made use of these two relevant documents as bases in determining the threatened status of the woody species in forests over limestone.

Designing a framework for conservation
The study proposes a framework for sustainable conservation of threatened species to put a stop to the current and continuing loss of woody plant species in the country. The framework was developed in response to conservation gaps identified in scientific publications, existing policies, reports, and measures that must be taken seriously towards protection and conservation of floral species in forests over limestone. It highlights the practicality and locally doable in situ and ex situ strategies and the extent and dedicated engagement of the government and the community as well as the stakeholders towards the conservation of the threatened woody taxa.

Threatened woody plant species in forests over limestone
The study found 196 woody plant species belonging to 48 families in the forest over limestone in the J TT Philippines (Table 1). About half (40%) of the recorded species are endemic to the Philippines (DAO 2017-11; Pelser et al. 2011 onwards). Additionally, Moraceae family is the most represented family, having 16 documented species, followed by Fabaceae (16 species), Euphorbiaceae and Dipterocarpaceae, having 15 species each, and Rubiaceae and Sapindaceae, with 10 species each.
Meanwhile, for SINP and GMRPLS alone, a total of 85 (out of 196) woody plant species, including 37 families, were recorded, including the flora checklist in the municipality of Basey, Samar.
As shown in Table 1 In contrast to the DAO 2017-11 assessment, many of the species found in limestone forests were classified in the IUCN conservation status assessment, as shown in Figure 3. Samar Island has 43 species classified by DAO 2017-11, with seven CR, five EN, 22 VU, and nine OTS, and 80 species classified by IUCN, with six CR, 13 EN, 17 VU, nine NT, and 35 LC. Mt. Tabunan has four species classified by DAO 2017-11 (one CR and three VU), and 41 species classified by IUCN (one CR, two EN, one VU, three NT, 33 LC, and one DD). Mangifera altissima Blanco is the only DD species found on Mt. Tabunan. This species was, however, classified as vulnerable in DAO 2017-11. Additionally, Mt. Cantipla has three species classified by DAO 2017-11 (two CR and one EN), while 23 species classified by IUCN (seven EN, three VU, two NT, and 11 LC). Mt. Lantoy has 17 species classified by DAO 2017-11 (two CR, three EN, nine VU, and three OTS), and 12 species classified by IUCN (two EN, three VU, one NT and six LC). Verde Island Passage has three species classified by DAO 2017-11, with two EN and one VU, and 50 species classified by IUCN, with two EN, three VU, and 45 LC, respectively (see Table 1; Figure 3, 4). Based on DAO 2017-11 and IUCN assessments, Samar Island has the highest number of CR, EN, VU, OTS, and NT species, while Verde Island Passage in Batangas has the highest number of Least Concern (LC) species (see Figure 2,3). The low number of species classified by DAO 2017-11 could be attributed to the fact that the Philippine red list was out of date, as the listing was made in 2017. This figure may change if the assessment and listing of threatened species in the Philippines are completely   The island of Samar, where SINP and GMRPLS are located, has been subjected to anthropogenic pressures such as timber cutting due to extensive logging, rattan extraction, and kaingin extraction (clearing of land through slash-and-burn agriculture) Obeña et al. 2021;Villanueva et al. 2021a). Mount Cantipla (Cadiz & Buot 2009), Mount Tabunan (Cadiz & Buot 2010), Mount Lantoy (Lillo et al. 2019(Lillo et al. , 2021 forest in Cebu and Verde Island Passage in Batangas (Caringal et al. 2021) have been harmed by illegal logging and land use change activities. This is indeed true as also reported in several studies (Dirzo & Raven 2003;Rodrigues et al. 2006;Wright 2010;Croteau & Mott 2011). A variety of human activities, including habitat destruction, logging operations, shifting cultivation, fragmentation and degradation, pollution, the introduction of nonnative species, and over-exploitation resulting from the conversion of natural vegetation such as forests into other uses amidst aggravating climate change issues, contribute to species endangerment and eventual local plant extinctions in the tropics. Many dipterocarp species, for instance, are particularly vulnerable in Southeast Asia because they play a unique role in forest ecology and are highly valued for their timber (Ashton & Kettle 2012;Maycock et al. 2012), and hence, are prone to exploitation through overharvesting Fernando et al. 2015;McKinney 1997). If these anthropogenic threats are not mitigated and prevented, the number of woody plant species will decline and likely become extinct in the future. In fact, Koh et al. (2004) predicted that 6,300 species would become endangered if their host species become extinct. This is critical in the context of our forests over limestone not only those in Samar Island and the entire Philippines, but throughout the tropics. The ecosystem is already in severe stress due to microhabitat agroclimatic challenges, thus, if other J TT anthropogenic disturbances occur, growth and survival of indigenous and endemic flora as well as fauna will be negatively affected. Also, these activities could have serious consequences on the livelihood of the local people who rely on them.
Unfortunately, the decline in number of some threatened woody plant species from various locations throughout the country has not yet been documented for inclusion in the Philippine red list or the IUCN. With 95% of plant species yet to be assessed on a global scale, new approaches to conservation assessment are urgently needed (Lughadha et al. 2005;Krupnick et al. 2009;Schatz 2009;Miller et al. 2012).

Notes on some threatened species in forests over limestone with economic importance Agathis philippinensis Warb.
Agathis philippinensis, commonly known as almaciga, can be found in the Philippines, Moluccas and Sulawesi. It is tapped and produces high quality of resin commercially known as Manila copal, which is used as raw material for varnish, lacquer, paper paint driers, linoleum, and ink, among others (Brown 1921;Samiano & Ella 2014). Due to the current high market demand for resin, sustained pressure from logging and resin collection, as well as unsustainable tapping methods, has contributed to declining populations of A. philippinensis in the Philippines (Jose 2018).

Antirhea livida Elmer
Antirhea livida is an endemic found in Luzon and Mindanao. Based on the IUCN (2022) assessment, this species will continue to decline due to the habitatthreatening effects of commodity-driven deforestation, shifting agriculture, urbanization, and losses from forest plantations and natural forest harvesting. Despite having a relatively large distribution, the species is still classified as Vulnerable due to its limited number of locations, small area of occupancy (AOO) value, and current threats to population and habitat quality. As such, immediate and active conservation measures must be considered to prevent the species from being pushed into a more threatened category in the future (IUCN 2022).

Aquilaria cumingiana (Decne.) Ridl.
Aquilaria cumingiana is a shrub or small tree which is found in the Philippines and Indonesia. A. cumingiana most famous product is agarwood, a resin containing heartwood produced from old and diseased trees (Tawan 2003) that is used for ornamentation, perfume and aromatic purposes (Swee 2008). Anthropogenic pressure on lowland primary forest within the range is reducing the amount of available habitat across its range (Lemmens & Bunyapraphatsara 2003).

Camptostemon philippinensis
According to the IUCN (2022) assessment, this species is extremely rare and has a limited and patchy distribution in Indonesia and the Philippines. Throughout its range, it is severely threatened by the removal of mangrove areas for fish and shrimp aquaculture, as well as coastal development. It is estimated that there are less than 2,500 mature individuals left and there has been a least 30% decline in mangrove area within this species range since 1980 (one generation length).

Cinnamomum cebuense Kosterm.
Cinnamomum cebuense is an endemic tree species in the Philippines. Based on the assessment of IUCN (2022), the population of this species is expected to continuing declining due to the habitat threatening effects of commodity-driven deforestation, urbanization, unsustainable farming practices, and large-scale forestry operations. The species occurs naturally in Cebu Protected Landscape, providing some passive conservation. However, more proactive measures (e.g., artificial propagation, reintroduction to various arboreta in the country) should be implemented to prevent the species from becoming more threatened in the future.

Dipterocarpus gracilis Blume
Dipterocarpus gracilisis is native to the Philippines. The wood of this species is used for general building construction, particularly for house posts and frames, planking in lighters and ships, flooring, piling, bridge construction, wharves, and railroad ties (NRMC 1986). Due to continued deforestation and overexploitation, the DAO 2017-11 and IUCN (2022) classified this species as Vulnerable. The IUCN (2022) recommended that species harvest and trade be monitored, that remaining

Guioa discolor Radlk.
Guioa discolor is an endemic tree. Based on the assessment of IUCN (2022), this species will continue to decline due to the habitat-threatening effects of commodity-driven deforestation, shifting agriculture, urbanization, and losses from forest plantation and natural forest harvesting. Immediate and active conservation measures are needed to keep the species from becoming more threatened in the future.

Hopea foxworthyi Elmer
Hopea foxworthyi is endemic. Its wood is used for general house construction, posts, bridge timber, and other wood applications that require strength and durability (NRMC 1986).

Hopea philippinensis Dyer
Hopea philippinensis is endemic to the Philippines. Based on NRMC (1986), this species is used locally for house posts and temporary railroad ties, but it is not widely used in construction due to its small size. However, H. philippinensis is depleted as a result of logging and kaingin making.

Kibatalia puberula Merr.
Kibatalia puberula is endemic to the Philippines. Based on IUCN (2022) information, K. puberla is restricted only in Samar and Leyte where it is known from dipterocarp forests or riverbanks, at elevation ranging from 100 to 250 meters asl. The species has a small area of occupancy and extent of occurrence, and it is declining due to threats to its habitat such as unlawful logging, poaching, charcoal making and firewood collection in Mt. Nacolod. These factors contribute to population decline of this species.

Litchi chinensis Sonn.
Litchi chinensis is native to the Philippines and New Guinea. According to Pareek (2016), this species is cultivated commercially in more than 20 countries. It is a high-value tropical fruit on the international fruit market (Miranda-Castro 2016). Because it is the best source of gutta-percha in the Philippines, destructive harvesting of the trees for gutta-percha in the past has severely eroded population levels (Brown 1920

Palaquium luzoniense (Fern.-Villar) S. Vidal
Palaquium luzoniense is a native species in the Philippines and Sulawesi. The timber constitutes the majority of red nato in the Philippines. It is used to make furniture and cabinets, cigar boxes, and ship planking, as well as veneer and plywood. The latex of this species is used to make gutta-percha (Lemmens 1993

Shorea almon Foxw.
Shorea almon is native to the Philippines and Borneo. The wood of S. almon is used for furniture and interior work of all kinds, boat planking and decking patterns, and for uses requiring a moderately hard and comparatively light wood with a beautiful ribbon figure. This species is in great demand for plywood both of rotary and sliced veneer. However, S. almon is now depleted due to logging and kaingin making (NRMC 1986).

Shorea negrosensis Foxw.
Shorea negrosensis is an endemic tree. It is commonly used for furniture and cabinet work of all kinds, veneer, hardboard and plywood, sash and millwork, boat planking and decking, and general building construction. However, the ecological status of this species is depleted due to logging and kaingin making (NRMC 1986).

Tectona philippinensis Benth. & Hook.f.
Tectona philippinensis is endemic to the Philippines. It is restricted only in coastal forests, littoral cliffs, and inland limestone ridges. This species is highly threatened due to its habitat preference, which is vulnerable to land conversion and development. It is also harvested for its timber and used to make fuelwood and charcoal (IUCN 2022).

Vitex parviflora Juss.
Vitex parviflora can be found throughout the Philippines. This wood of this species is used for construction work that requires strength and durability, such as railroad ties, bridge posts, etc. Its ecological status is depleted due to logging and kaingin making (NRMC 1986).

Framework for sustainable conservation of threatened taxa
We developed and are proposing a framework for sustainable conservation of forests over limestone threatened species ( Figure 5) to arrest their continuous decline. The framework illustrates an integrated practice of in situ and ex situ conservation strategies supportive of enhanced onsite protection and plant reintroduction (Buot 2008a,b,c;Kawelo et al. 2012;Miller et al. 2016;Tobias et al. 2021). If implemented with the aid of community participation, localized and national policy implementation, this could help save the species from extinction.
The framework emphasizes the enhancement of the ecosystem structure, function, and processes through practical and locally doable in situ and ex situ strategies. The integrity of the ecosystems rests in having a rich species composition and diversity (structure) and stable and dynamic ecosystem function and processes (Sulistiyowati & Buot 2013, 2020Sulistiyowati et al. 2017). In situ strategy via the protected area systems, remain the country's best hope for preserving plant biodiversity and genetic resources onsite (Fernando et al. 2015), such as those found in some areas in Samar Island forests over limestone and many other types of forests in the country (e.g., Cebu's Mounts Tabunan, Cantipla, Lantoy) and in other parts of the world. There are still large tracts of forests over limestone which are not yet covered by national or even local protection (e.g., in GMRPLS).
Ex situ strategy, on the other hand, can be used to preserve groups of species that have experienced rapid declines as a result of anthropogenic activities, especially land use conversion. This conservation strategy can take the form of cultivation in botanic gardens and gene banks, nursery propagation, backyard gardening (Tobias et al. 2021), and establishment of forest groves and patches, to name a few. These forms of ex situ strategy will ensure the preservation of the species gene pool and can be used in reforestation and reintroduction in the natural habitat.

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Some enabling mechanisms are critical for the framework to be a success. In Figure 8, enabling mechanisms are divided into two columns. The left side enumerates the usual enabling strategies which have failed in many instances in the past. In this proposed framework, we included a PLUS (+) sign to illustrate the importance of the second column. As usual, there should be livelihood opportunities for the community (DENR-PAWB et al. 2003). The economic currency is of utmost importance for the community to understand the ecological contexts of conservation of the forests over limestone. Then, local community motivation is essential to participate in conservation strategies because success and failure of any task, is largely dependent on local people (Toit 2002), the empowered local people (Mathur 1997). Alongside this, there should be sustained forest conservation advocacy and the availability of appropriate community education and public awareness (CEPA) materials (Tolentino et al. 2019;Buot 2020;Buot & Buhay 2022). Additionally, coupled with localized conservation policies ) and national executive orders (Chanthavong & Buot 2019;Betts et al. 2020;Buot & Buhay 2022), we are positive to have a good enabling mechanism for conservation of threatened taxa.
The aforementioned had been done in the past and yet, we still are struggling to stop escalating depletion of plant resources leading to extinction. Hence, we thought of adding the second column of the Enabling Mechanism in Figure 5. We emphasize the PLUS sign (+). We envision the need for passionate leadership examples, sincere efforts of the local government units and a highly motivated local community to attain success in our conservation efforts. The success of these conservation strategies and initiatives is dependent on the extent and dedicated engagement of the innovator with the local government unit and the community members, themselves. The change agent/innovator should have the passion and sincere intentions to earn community's trust and attention.

CONCLUSION AND RECOMMENDATION
The findings of the study revealed that 40.81% of the threatened species found in forests over limestone in SINP, GMRPLS, Mt. Lantoy, Tabunan, Cantipla forest, and Verde Island Passage are indigenous and endemic to the Philippines. These species are primarily threatened by natural (typhoons, landslides, climate change) and anthropogenic activities such as unlawful logging and land conversion. There is an urgent need to address the steady increase in the number of these endangered species in recognition of their critical role in ecosystem structure and processes that would keep the integrity of the forests over limestone ecosystems in the country and in the world. A framework has been suggested in this paper to stop the continued species loss by integrating in situ and ex situ conservation strategies along with enabling mechanisms like enhancing livelihood, community awareness and participation to name a few, in order to stabilize species richness and diversity and hence, ecosystem function, processes, and dynamics. These will lead to the overall conservation of forests over limestone ecosystems, and hence, sustaining the life of the community in the vicinities through the sustained provision of ecosystem services.
The findings of this study will help achieve the