Forest Vegetation Cover in Binh Chau-Phuoc Buu Nature Reserve in Southern Vietnam

Binh Chau Phuoc Buu Nature Reserve is located in the tropical rainforest zone of southeast Vietnam. The obtained results from the study undertaken on the composition of plant species and forest vegetation in Binh Chau Phuoc Buu Nature Reserve indicated a record of 743 species, 423 genera and 122 families that belongs to the three divisions of vascular plants. These includes: Polypodiophyta, Pinophyta and Magnoliophyta. Useful plants of 743 taxonomy species listed consists of 328 species of medicinal plants, 205 species of timber plants, 168 species of edible plants, 159 species of ornamental plants, 56 species of industrial plants, 10 species of fiber plants and 29 species of unknown use plants, respectively. During the duration of investigation, Nervilia aragoana Gaudich. was newly recorded in the forest vegetation of Binh Chau Phuoc Buu Reserve. A variety of forest vegetations in the area under study is described. In this study, two major vegetation types of forest were identified in Binh Chau Phuoc Buu Reserve.

BC-PB Reserve is the only remaining natural of deciduous dipterocarp forest, located on the coast of SouthernVietnam. Rare, valuable and endemic species of flora and fauna, listed in the Red Book of Vietnam and the International Union for Conservation of Nature (IUCN), live in BC-PB Reserve. However, in recent years, the structure of forest vegetation cover in BC-PB Reserve has changed. This led to a change in the habitat of plants and animals, the number of individuals decreased, and many rare and endangered species were threatened. Therefore, the issue of forest conservation in BC-PB Reserve plays an important role.

Materials
The objects for research were forest ecosystems on the territory of BC-PB Reserve. Ecological and geographical analysis of the species composition of forests in the reserve indicates certain links between regions and environmental conditions reveals their environmental specificity.

Methods
Geobotanical and floristic study was carried out on the 35 plots (20×20 м) [4], [9] ( Figure  1). We established 16 transects, which covered the whole surface area of BC-PB Reserve. The total length of these transects combined is about 20 km. In each transect we marked all species and collected specimens of plants which could not be identified in the field. We also collected many plants outside the plots and traverses, to make sure that our inventory was as representative of the entire area with species of the local flora [1].
Voucher species were sent to the Herbarium of the Vietnam National University of Forestry -Dong Nai campus and other specialists for identification. Plant species were identifed with reference to An Illustrated of Flora of Vietnam [5].
The vegetation types of BC-PB Reserve were classified according to Thai Van Trung [8]. Additionally, the human disturbance levels of the vegetation were determined by noting the number of tree stumps and number of foot paths in the plots [3].
From 2019-2020, the research team conducted many surveys in Binh Chau, Bung Rieng, Bong Trang and Phuoc Thuan villages in BC-PB Reserve. Field research was conducted to gain intensive understanding of people through discussions and interactions. Primary data was gathered initially through household interviews based on questionnaires, Rapid Rural Appraisal (RRA), and the "walk in the woods" method [2].

Vegetation types in BC-PB Reserve
The vegetation of BC-PB Reserve is dominantly lowland forest type with the highest peak level of about 160 m [8]. Among the natural vegetations of BC-PB Reserve there is a major dichotomy between the evergreen forests on lowland types and other types of formations. The composition of the vegetation in BC-PB Reserve is identified by 2 major types: tropical evergreen broad-leaved semi-deciduous and plantation forest.
Tropical evergreen broad-leaved semi-deciduous forest ( fig. 2  Plantation forest. This forest type covers about 1165 ha. The following species, such as: Acacia auriculiformis, Afzelia xylocarpa, Dipterocarpus condorensis, Shorea roxburghii, Anisoptera costata, Pterocarpus macrocarpus, etc… are planted in plantation forest of BC-PB Reserve. The structure of this forest type is simple; it includes the tree layer and a ground layer with mainly weedy species belonging to families Poaceae, Rubiaceae, Euphorbiaceae, Asteraceae.

Floristic diversity in BC-PB Reserve
During our investigations, 743 vascular plant species belong to 423 genera and 122 families were identified in BC-PB Reserve can be seen in Table 1. At the period time, two species of plants were newly recorded in literature devoted to the flora of Vietnam, named Stereospermum binhchauensis V.S. Dang [7] and Kaempferia champasakensis Pichean. & Koonterm [10]. The present study recorded one new species in BC-PB Reserve, named Nervilia aragoana Gaudich. in Orchidaceae. Among the investigated 743 species, 6 endemic species in Vietnam were also included. Many plant species are endemic to Vietnam (the species were first records in Vietnam and scientific names take the places of Vietnam) and endemic plants of local (the first records of species in BC-PB Reserve) such as Stereospermum binhchauensis (Table 2).   Table 3.   [11]. In the red book of IUCN (2020) [12], 7 species were classified as endangered species (EN), 6 species were classified as vulnerable species (VU) and 5 species were classified as least concern (Table 4).

Conclusions
BC-PB Reserve is characterized by two major vegetation types of forest: tropical evergreen broad-leaved semi-deciduous and plantation forest.
The diversity of plant species in BC-PB Reserve was studied to provide baseline information for conservation and sustainable management processes that will prolong the the life of the reserve. Besides this survey, the forest areas were explored, concentrating on the useful plants and it was recorded that BC-PB Reserve has 6 endemic species, 25 species subject to global-level and national-level conservation.