Quantifying Arborescent Flora Diversity in a Secondary Forest Ecosystem: A Comprehensive Assessment in Nambalan, Mayantoc, Tarlac, Philippines

Forest plays a crucial role in providing essential ecosystem services, including water supply, climate regulation, and biodiversity conservation. This study aimed to assess the current state of the forest in Barangay Nambalan, Mayan-toc, Tarlac. The specific objectives were to identify tree species in the area and determine the tree diversity index, with a focus on endemism and conservation status. Two transect lines, each spanning one kilometer, were established and a total of 10 sampling quadrats were surveyed. Ecological parameters (relative frequency, relative density, relative dominance, and importance value index) and diversity indices (Shannon-Weiner index, Simpson’s index) were computed using the Paleontological Statistic Software Package for Educational Analysis (PAST 4.03). A comprehensive inventory revealed a total of 756 individuals representing 52 species, 46 genera, and 25 families. Among the recorded species, 10 (17.2%) were endemic and 11 (21.6%) were classified as threatened. The Fabaceae (20.8%), Moraceae (14.6%), and Euphorbiaceae (8.3%) were identified as the most abundant families. The computed diversity indices indicated that Barangay Nambalan retains a diverse forest cover; however, species composition was found to be relatively low. Based on the finding, this study recommends the strict enforcement of protective measures and legislation to mitigate further degradation of the remaining forest in Ba-rangay


Introduction
Arborescent flora, comprising trees, plays a crucial role in forest ecosystems, serving as a key component for resource conservation and management in both rural and urban areas [1]. Forest provide a wide range of valuable services, including water supply and rainfall maintenance, security and nutrition, climate control, and biodiveristy conservation [2], which are essential for meeting immediate human needs. However, the future of global forests and trees is confronted by significant environmental and development challenges on a global scale [3].
The Philippines is recognized as one of the world's megadiverse countries, harboring a rich diversity of life forms in both aquatic and terrestrial ecosystems [4]. Nevertheless, biodiversity is currently under critical threat as human activities contribution to the degradation of natural resources, particularly forests [5]. According to the DENR-FMB [6], the Philippines has witnessed a staggering 70 percent decline in forest cover from 1900 to 2007, with forest area decreasing from 21 million hectares to a mere 6.5 million hectares due to extensive logging activities.
Central Luzon, a significant contribution to the country's economic growth, has witnessed the ongoing degradation of its remaining forestlands and watersheds due to rapid urbanization and development [7]. In Tarlac, located in Central Luzon, a substantial decrease in closed forest area has been observed, declining from 5407 hectares in 2010 to a mere 4.0 percent of the total tree cover by 2020. This decline can be primarily attributed to forest fires and extensive logging activities [6] [8]. Notably, Mayantoc, one of the municipalities in Tarlac, has experienced considerable tree cover loss compared to other regions [9]. Consequently, there exists an urgent imperative to undertake a comprehensive inventory and assessment aimed at identifying the trees species in the area, evaluation their conservation status, and formulating informed plans to safeguard the remaining forest cover. Hence, the main objective of this research was to assess the diversity of tree species in Barangay Nambalan, Mayantoc, Tarlac. Specifically, the study aimed to 1) Identify and Quantify tree species in the area; 2) Determine the tree diversity index and ecological parameters of forest communities; 3) Determine the endemism and conservation status of the tree species present in the area; and 4) To provide a recommendation regarding the present condition of forest in Barangay Nambalan, Mayantoc.
significant biomass accumulation and carbon storage in a tropical rainforest.
In addition to species richness, tree diversity studies often examine species composition and evenness. Species composition refers to the specific combination of tree species present in an area, while evenness refers to the relative abundance of different species. Both factors are crucial in understanding community dynamics and ecosystem processes [12]. For instance, a study by Baraloto et al. [13] in a neotropical forest revealed that changes in species composition and evenness influenced the functional diversity of tree communities, affecting key ecosystem processes such as nutrient cycling and productivity.
Furthermore, research into the factors that influence tree diversity has provided insights into the mechanisms that shape forest ecosystems. Climate, topography, and soil characteristics have all been shown to influence tree species distribution and diversity [14]. Quesada et al. [15] found that tree species composition and diversity varied with soil fertility and hydrological conditions in the Amazon rainforest, highlighting the importance of edaphic factors in shaping forest communities.
Human activities and land-use changes also significantly impact tree diversity. Deforestation, habitat fragmentation, and conversion of forests to agricultural or urban areas have led to the loss of tree species and the homogenization of tree communities [16]. Studies have shown that human disturbances can decrease tree diversity and alter community dynamics, disrupting ecosystem functions [17]. For instance, a study by Laurance et al. [18] revealed that selective logging reduced tree species diversity and altered community composition in a tropical forest, affecting carbon storage and nutrient cycling.
Overall, research on tree diversity has emphasized its importance for ecosystem functioning and conservation. Understanding the patterns, drivers, and ecological implications of tree diversity is crucial for effective forest management, conservation strategies, and the sustainable use of forest resources.

Importance of Biodiversity
Biodiversity, the variety of life on Earth, is critical component of our planet's ecosystems and plays a fundamental role in sustaining the functioning and resilience of natural systems. According to Kanieski et al. [19], biodiversity is considered a key indicator of ecosystem well-being and directly reflects the conservation status of a particular area. A diverse and healthy biodiversity provides numerous natural services that are essential for human well-being. People living in rural areas near forests rely on a wide range of forest products for their subsistence, and the income generated from trees and forests is crucial for both rural and urban populations. Biodiversity conservation offers significant benefits in meeting immediate human needs, such as ensuring clean and reliable water resources, protection against floods and storms, and maintaining a stable climate. It also provides social benefits, including education, monitoring, recreation, tourism, and cultural values [20].
In the study conducted by Ludwig and Reynolds [21], several steps were iden-DOI: 10.4236/oje.2023.136024 390 Open Journal of Ecology tified in the investigation of biodiversity, including defining study objectives, delineating the study area, determining sampling methods, collecting and organizing data, measuring species similarity, and characterizing biotic factors. Inventory studies serve as the foundation for biodiversity conservation efforts, as they provide essential information for the sustainable use and protection of biodiversity components. Biodiversity assessments are globally recognized as fundamental activities in achieving sustainable biodiversity conservation [22].
Aureo et al. [23] emphasized the importance of understanding biogeographical patterns, species richness variations, and endemic trends in elevationally diverse areas for effective conservation strategies. By comprehending these patterns, conservation efforts can be targeted towards protecting and managing areas of high species richness and endemism. Ganivet and Blomberg [24] highlighted the need for assessing both tree species diversity and forest structure at local and regional levels to gain insights into the current state of tropical forests and develop effective management strategies for their conservation. While assessments at local scales provide accurate estimates of species richness and forest structure, it is important to extrapolate these findings to regional scales to understand the broader picture of tree species diversity and forest structure.

Biodiversity Conservation
Biodiversity conservation is a crucial aspect of environmental management and sustainable development. One key aspect of biodiversity conservation is the recognition of the intrinsic value of biodiversity. Biodiversity encompasses a variety of life forms, including genes, species, and ecosystems, and its conservation is essential for maintaining ecological balance and resilience [17]. Biodiversity conservation efforts aim to prevent the loss of species and ecosystems and ensure their long-term survival.
The benefits of biodiversity conservation extend beyond ecological considerations. Biodiversity provides numerous ecosystem services that are vital for human well-being. For instance, intact ecosystems with high biodiversity can enhance water quality, regulate climate, and provide various industries with natural resources such as food, medicines, and materials [25]. Biodiversity conservation also plays a crucial role in supporting livelihoods, particularly for communities that rely on natural resources for their sustenance and income [26].
Biodiversity preservation is critical for ecosystems' continued functioning and resilience. Studies have shown that higher levels of biodiversity contribute to increased ecosystem productivity, stability, and resistance to disturbances [27]. Biodiversity conservation helps protect and restore vital ecological processes, such as pollination, nutrient cycling, and pest regulation, which are essential for maintaining the health and productivity of ecosystems [28].
Various strategies and approaches guide biodiversity conservation efforts. National parks and nature reserves are established to protect critical habitats and species [29]. Additionally, habitat restoration and rewilding initiatives aim to

Conceptual Framework
The INPUT-PROCESS-OUTPUT Model was used by the researcher to provide a general structure and direction for the study. Figure 1 depicts the study's conceptual framework, in which the input consists of data collection through field inventory, transect and quadrat establishment, and specimen collection and preservation. For diversity indices, the Shannon Diversity Index formula was used as follows from the studies of Coracero et al., [4].

Data Collection Instruments
The instruments used in data collection were as follows: Procedural activities and formulas were obtained from references, such as previous studies by various researchers, specifically the study conducted [4]. Primary data gathering was through fieldwork activities, mapping and on-site observations, geotagging and tracking using locus map and GeoCam were used to document the activities within the research area.

Data Collection Procedure
Preliminary procedures were carried out before the conduct of the study. Secondary data such as area, climatic data, soil, elevation, and other related information were gathered from the Barangay Nambalan Forest Land Use Plan and other online references. The study's mapping activity was created using Quantum GIS (QGIS 2.18) and data generated from the National Imagery and Mapping Agency (NIMA) database, which is accessible online through Diva GIS.

Transect and Quadrats Establishment
Two (2) transect lines were established with a length of one (1) kilometer each and with ten (10) sampling quadrats having a size of 20 × 20 meters ( Figure 3).
The sampling plots were established in alternating directions on the transect line with 250 meters regular interval.

Sampling and Data Collection
Biodiversity Assessment A total of ten (10) 20 × 20-meter sampling plots were established for the identification of trees with at least 5 centimeter in diameter at breast height (DBH). Lillo et al. [34]. Elevation and trees with flowers and fruits were also observed.

Data Analysis
The process of vegetation analysis, including the assessment of tree diversity, computation of diversity indices, identification of tree species, determination of conservation status, and evaluation of species endemism, in this comprehensive discussion. The methods and references cited are based on the research of Coracero and Malabrigo [4], Aureo et al. [23], and Lillo et al. [34], as well as the use of various botanical resources. The data collected for the study were utilized for vegetation analysis, specifically focusing on tree species. The evaluation of tree diversity involved the implementation of species abundance measures, such as density, frequency, and dominance. These measures are essential for determining the importance value of each species, which is a standard measurement in forest ecology to establish the rank relationship among different species [34].
The importance value was computed as the cumulative value of relative density, relative frequency, and relative dominance combined into a single metric [23]. This metric provides a comprehensive assessment of the significance of each species within the ecosystem.
Furthermore, diversity indices were computed using the Paleontological Statistics Software Package for Education and Data Analysis (PAST v.4.03). The interpretation of these diversity indices was based on the Fernando Biodiversity Scale (Table 1), as outlined in the study conducted by Coracero and Malabrigo [4]. This scale enables the researchers to understand the level of biodiversity present in the studied area.
To accurately identify tree species, a combination of resources was employed. Local experts, instructors, and knowledgeable locals were consulted to aid in species identification. Additionally, flora databases such as Co's Digital Flora of the Philippines [35] [38], were also consulted. Furthermore, open-access websites of digital herbaria were referenced to access relevant information. The methodologies for species identification and the utilization of these resources were based on the studies conducted by Coracero and Malabrigo [4].
In order to determine the conservation status of each tree species in the Philippines, the researchers relied on the DENR Administrative Order 2017-11. This administrative order provides guidelines and regulations for the conservation of species in the Philippines. Additionally, the conservation status of the species worldwide was determined based on the IUCN Red List, which is maintained by the International Union for Conservation of Nature (IUCN) and provides a comprehensive assessment of the threatened species globally [39].
Furthermore, species endemism was determined using the plant species archive available in the Philippines, namely Co's Digital Flora of the Philippines [35], which is accessible online. This archive provides valuable information on the distribution and endemism of plant species within the Philippines.
The formulas for the computation of various parameters, including importance values, diversity indices, and other relevant metrics, were based on the studies conducted by Coracero and Malabrigo [4]. These studies provided the necessary mathematical frameworks for calculating these parameters accurately and effectively.

Tree Species Diversity
The study identified a total of 756 individual trees belonging to 26  with five identified species. This finding suggests that these families play a critical role in influencing the growth and survival of other species in the area [41].
Additionally, Fabaceae species were found to be easily germinating due to their nitrogen-fixing capability [42]. Moraceae and Euphorbiaceae were identified as important food sources for bats and birds, leading to high rates of seed dispersal and successful recolonization [43]. A similar study conducted by Cruz et al. [44] in   ability to capture more resources, resulting in the proliferation of their population over time compared to others [46]. Moreover, the density of species per area influences the development of stem diameter, but other factors such as edaphic and climatic factors may also influence the secondary growth of tree species [47].
Plant species identification was very much dependent on reproductive structures [48]. As a result, in order to perform a more accurate and convenient identification, the reproductive parts of the species must be collected in the field [4].
Furthermore, it could be a source of native species seeds for landscaping and seedling production in the area.
Out of the 52 tree species documented, 13 species were observed with reproductive parts within the sampling sites, as shown in Figure 5. It is noteworthy that all the recorded flowering plant species, like Pittosporum pentandrum has the ability to suppress and inhibit the growth of Cogon (Imperata cylindrica) and Talahib (Saccharum spontaneum); it also produces good soil cover in denuded areas, which is useful for vegetative rehabilitation of degraded areas [49]. This emphasizes the rich native floral diversity present within the study area and highlights the importance of conserving these native plant species to maintain the ecological balance and support local ecosystems.
In the study area, the presence of reproductive parts in a subset of tree species  The predominance of native flowering plant species among the individuals recorded emphasizes the importance of native plant conservation. Native species are frequently better adapted to local environmental conditions and play critical roles in sustaining local biodiversity, ecosystem functions, and overall ecosystem stability.

Diversity Indices
In the case of Barangay Nambalan, the computed diversity index classifies it as a high diversity area based on the Fernando Biodiversity Scale, with a Shannon diversity index of 3.486 and an evenness index of 0.7098. This indicates a wide variety of species and an even distribution of individuals among them. According to Lillo et al. [34], high species diversity in an area contributes to a more stable and productive ecosystem, as diversity is associated with stability, productivity, and trophic structure [50].
Further analysis reveals that six quadrats, specifically two from Transect 1 and four from Transect 2 (Table 3), were classified as having high diversity per quadrat. This suggests that these specific areas within Barangay Nambalan contain a considerable number of different species. However, it is important to note that the diversity in Barangay Nambalan is primarily driven by the number of individual species rather than species composition. This finding aligns with the assertion made by Guiang [51] that a forest community with a higher number of individual species is considered to have high diversity. Additionally, it is known that certain tree species develop specific adaptations that allow them to thrive better than others in a given area [52].   Figure 6. Quadrat with the highest species distributions in the study area.
The diversity observed in this particular plot can be attributed to various factors, including the type of soil, the presence of specific species, and the ground cover. As noted by Cordova et al. [53], the role of leaf litter in facilitating plant growth depends on the species. In the case of quadrat 4, which was characterized by a forest floor covered with leaf litter from dominant species, particularly the Fabaceae family, the high diversity observed was expected. Leaf litter promotes soil fertility through microbial activities that are essential for plant growth [53].  Based on the observations made during the establishment of the transect, this area was dominated by Cogon grass (Imperata cylindrica), which affects the species diversity in the ground cover because cogon commonly over-dominates the vegetation that is prone to burning or fire [53], as well as in areas that are overgrazed and intensively cultivated [54]. These findings demonstrated that forest structure varies from lowest to highest elevation in terms of tree diameter, height, and species composition. The type of soil in the area, ground cover, species types, elevation, and climatic conditions all had an impact on these findings. This result confirmed Amoroso et al. [55] finding that elevation influences species composition by providing complex environmental gradients such as temperature, rainfall, and relative humidity, as well as different nutrient requirements of the tree species in the area.
These results indicate that these plants were the most common and the most dominant species in the area [56]. It confirmed that the relative density of each species contributed most to their IV and the floristic composition and vegetation Open Journal of Ecology structure of this area were dependent from these species [53]. In addition, species with high importance value index as shown in Figure 9, indicates that the species was well-represented due to a large number of individuals observed compared with other species [57] at the same time it provides an overall estimate of the influence of these species in the community [53].

Species Endemism and Conservation Status
As shown in Table 5 species endemicity assessment revealed nine (9) Table 5. This result confirmed that endemic species in the area should be given priority in conservation planning because these species are more vulnerable to threats due to their narrow range [58]. In addition, information on the geographic distribution of plant species in the area helps avoid species extinction and, at the same time, it plays an integral basis for the formulation of conservation and management strategies [53].
The conservation assessment was based on the International Union for the Conservation of Nature (2021-3) and DENR Administrative Order No. 2017-11. The assessment result showed that of the 52 species collected, only 11 (21.6%) of the total species were threatened as shown in Table 6.
This result showed that there were eleven species recorded in this inventory that should be given priority for conservation because the ecological significance of any land formation relies not only on species richness but also on the number of native, endemic, and even threatened species present in the area [59].

Conclusion and Recommendation
Based on the results, Barangay Nambalan is dominated by families Fabaceae, Moraceae, and Euphorbiaceae. There were 10 (17.2%) endemic species and 11 (21.6%) threatened species recorded in the area out of 52 species. From low to high elevation, the forest structure varies in terms of tree diameter, height, and species composition. These findings were influenced by the type of soil in the area, ground cover, types of species, elevation, and climatic conditions. The sur- studies in other parts of the forest would be preferable to better assess its diversity so that the initial information gathered can be supplemented by additional survey data to create a good reference document for conservation and management in the area.