DIVERSITY OF SHRUBS AND TREES IN THE ISLAND TOWNS OF NORTHERN SAMAR, PHILIPPINES

This study aimed to identify the shrubs and trees in the five island towns of Northern Samar, Philippines; determine their abundance, community structure; and economic uses to the locals. Four barangays in every island town represented the north, south, east, and west sides. Line Intercept Transect (LIT) at intervals of 100m and plot method with an area of 10m x 10m were used in gathering the data. Transect walks, field plots, and transects were also used in gathering data. There were 207 species of shrubs and trees belonging to 152 genera and 64 families. Shrubs constituted 55.33% and trees 44.67% of the total number of species. Mangifera indica (Anacardiaceae) ranked first in relative density (25.50%), relative frequency (25.30%), and importance value (59.15%). Plots in the island of Laoang were observed to have the highest Shannon Diversity Index (3.25%) and Simpson’s Dominance Index (1.86%). The most abundant shrub and tree species in the island towns were Citrus microcarpa (Cucurbitaceae) and Mangifera indica (Anacardiaceae) respectively. The least abundant shrub and tree species were Gardenia jasminoides (Rubiaceae) and Cananga odorata (Annonaceae) respectively. There were more species of shrubs and trees in the island town of Laoang than in the other four island towns.


Introduction
Shrubs are woody perennial plants that possess multiple stems arising from a common point known as the crown. Trees are woody perennial plants, such as shrubs, by the presence of usually but not always, a single woody stem known as the trunk. Both shrubs and trees inhabit virtually all climates and soil types, with a large variation in form, adaptability and stress tolerance from species to species [1].
The Philippines is one of the megadiversity countries of the world. It has also a large population, which exerts tremendous pressure to transform these biodiversity resources into material wealth Http://www.granthaalayah.com ©International Journal of Research -GRANTHAALAYAH [209] that will lift the people out of poverty [2], [3]. Awareness of the people about the rich biodiversity and the role of education should be emphasized. Attempts to identify methods of maintaining and using biodiversity in ways that can benefit the human population is the major role of conservation biology [4]. Systematics plays a vital role in conservation biology in determining the limits of species; only if these taxonomic entities are clearly defined can they be evaluated for rarity and the threat of extinction. In addition, floristic studies and phylogenetic analyses may have an impact on which species or biogeographic regions are most worthy of protection, given limited resources [5]. Naturalists, scientists, researchers, and conservationists predict that at 1% extinction rate, these resources will be gone by 2050 [6]. Organisms in small restricted areas, such as islands, are more prone to extinction because an environmental change in their locale can eliminate the entire species at once [7].
Living organisms provide us with many useful drugs. The United Nations Development Programme (UNDP) estimates the value of pharmaceutical products derived from developing world. Plants, animals, and microbes are estimated to be more than 30 billion dollars per year [8].
Because we don't fully understand the complex interrelationships between organisms, we often are surprised and dismayed at the effects of removing seemingly insignificant members of biological communities. Maintaining biodiversity is essential to preserving these biological and ecological services [9].
Thus, this study of shrubs and trees may open for more conservation and preservation practices for these woody plants for now and the future generations of island folks in the country.

Objectives
The objectives of this study are: 1) To identify the shrubs and trees in the island towns of Northern Samar, Philippines; 2) To determine their community structure; and 3) To determine the most abundant shrubs and trees in the island towns.

Methodology
The province of Northern Samar consists of 24 municipalities, i.e. 15 coastal towns, 5 island towns, and 4 interior towns. Catarman is the capital town of the province of Northern Samar.
Sampling areas included the five island towns of the province; i.e. Laoang, Biri, Capul, San Antonio, and San Vicente. The study was conducted during the summer months of April and May 2012-2014. Four barangays in every island town represented the north, south, east, and west sides. Line Intercept Transect (LIT) at intervals of 100m and Plot Method with an area of 10m x 10m were used in gathering the data. The preliminary identification was done on-site in the study area through personal communication with the foresters and local residents (local names). Further identification and verification were done at the College of Science Laboratory. Simpson's Dominance and Shannon-Wiener indices were used to verify the diversity status of shrubs and trees.

Shrubs and Trees in the Island Towns of Northern Samar
There were 207 species of shrubs and trees belonging to 152 genera and 64 families. Trees constituted 55.33% of the total number of species; while the shrubs 44.67%.

Community Structure of Shrubs and Trees
There were 207 species of shrubs and trees with average DBH (Diameter Breast Height) of ≥ 10cm. The density, relative density, frequency, relative frequency, dominance in terms of basal area, relative dominance, and importance value were calculated for each of the species of shrubs and trees. The results were: Relative Density (RD) -Mangifera indica (Anacardiaceae) had the highest relative density at 25.50%, followed by Tamarindus indica (Leguminosae) at 12.10%, and Chrysophyllum cainito (Sapotaceae) at 10.82%. The other shrub and tree species accounted for 51.58% total relative density.
Relative Frequency (RF) -Among the shrubs and trees, the most frequently seen in all of the five island towns is the presence of Mangifera indica, (Anacardiaceae) which is a fruit tree, and favorite fruit among the islander folks since the fruit tree is seen everywhere, i.e. in the farms, at house front and back yards, in schools, churches, markets, and seashores. Mangifera indica (Anacardiaceae) had the highest relative frequency at 25.30%, followed by Tamarindus indica (Leguminosae) at 12.78%, and Chrysophyllum cainito (Sapotaceae) at 10.36. The other shrub and tree species accounted for 51.56% total relative frequency.
Importance Value (IV) -For the 207species of shrubs and trees, importance value was calculated by adding the relative density (RD), relative frequency (RF), and relative dominance (RD). The species with the highest importance value was the fruit tree Mangifera indica, (Anacardiaceae) with 59.15%.
Diversity Status -Among the five island towns being surveyed, Laoang had the most number of species. This was also reflected by Shannon Index of 4.75 and Simpson's Dominance of 1.86. The high value for the island town of Laoang was attributed to its favorable location -it is near the mainland; i.e. Samar Island-considered as third largest island in the Philippines; only 5-10 minutes motorboat ride compared to the other island towns whereby, they can be reached from 30-90 minutes motorboat ride.

Abundant Shrubs and Trees
The most abundant shrub and tree species in the island towns were Citrus microcarpa (Cucurbitaceae) and Mangifera indica (Anacardiaceae) respectively. The least abundant shrub and tree species were Gardenia jasminoides (Rubiaceae) and Cananga odorata (Annonaceae) respectively. There were more species of shrubs and trees in the island town of Laoang than in the other four island towns; i.e. Biri, Capul, San Antonio, and San Vicente. Plots in the island of Laoang was observed to have the highest Shannon Diversity Index (3.25%) and Simpson's Dominance Index (1.86%). Fifty-three percent (53%) of the species were endemic to the island towns.
Families Caesalpiniaceae and Meliaceae respectively had the largest number of species which is 13; followed by Family Leguminosae which had 12 species; followed by Family Rhizophoraceae which had 11 species; and Families Palmae and Myrtaceae had both 9 species.
Other abundant species of shrubs in the island towns were: Avicennia marina (Avicenniaceae), Rhizophora mucronata ( It is observed that food requirement is the main reason of the abundance of trees in the island towns. Island folks plant them to provide nourishment, and store/preserve them during times of need. On the other hand, the abundant shrubs are used for construction purposes, for fuel, and for other uses. Some are ornamental flowering plants, which provide aesthetic value to the surroundings, especially for island people seeking for inspiration and adventure. 3) The most abundant shrub and tree species in the island towns were Citrus microcarpa (Cucurbitaceae) and Mangifera indica (Anacardiaceae) respectively. The least abundant shrub and tree species were Gardenia jasminoides (Rubiaceae) and Cananga odorata (Annonaceae) respectively. There were more species of shrubs and trees in the island town of Laoang than in the other four island towns; i.e. Biri, Capul, San Antonio, and San Vicente. Plots in the island of Laoang was observed to have the highest Shannon Diversity Index (4.75%) and Simpson's Dominance Index (1.075%). Fifty-three percent (53%) of the species were endemic to the island towns.
Families Caesalpiniaceae and Meliaceae respectively had the largest number of species which is 13; followed by Family Leguminosae which had 12 species; followed by Family Rhizophoraceae which had 11 species; and Families Palmae and Myrtaceae had both 9 species.