Preliminary Study on Tree Species Composition, Diversity and Biomass of Dipterocarpus and Hopea genera of Bukit Bakar Forest Eco Park, Machang, Kelantan

A study on species composition, diversity and biomass of genera Dipterocarpus and Hopea at Bukit Bakar Forest Eco Park, Machang, Kelantan was conducted. A total of 5 ecological plots with measurement of 20 m x 20 m were established. All trees with diameter at breast height (dbh) less than 5.0 cm were tagged, measured and collected for specimen identifications and voucher specimen’s preparations. The floristic composition of Bukit Bakar Eco Park consists of 135 individuals represented by 1 family, 2 genera and 17 species. The most abundance species recorded was Dipterocarpus crinitus Dyer with 23 individuals were recorded. Dipterocarpus crinitus (Dipterocarpaceae) was the most important species according to Important Value index (IVi) calculated at IVi = 17.73%. Dipterocarpaceae was the most high species diversity according to Shannon Wiener Index, H’=2.02 (H’ max =2.30) for Dipterocarpus spp. and H’=1.90 (H’ max =1.94) for Hopea spp. and Simpson’s Index of Diversity for Dipterocarpus spp. is 0.85 and 0.86 for Hopea spp.. Whilst Hopea had a slightly higher Species Evenness Index (EH=0.98) compared to Dipterocarpus (EH=0.87). Total tree biomass estimation in the study area was at 145.18 t/ha.


Introduction
In Malaysia, Dipterocarpaceae is known as economical timber trees and they serve as proxy to the forest such as preserving the biodiversity and absorbing CO2 concentration. Out of all vegetation type in Malaysia rainforest, lowland rainforest is the most highly diverse vegetation compared to others [1,2]. Dipterocarpaceae dominates the tropical over 30% of the basal area or over 40% in emergent area [3].
In plant community ecosystem, there are two critical parameters in plant community ecosystem which are biodiversity and biomass [4]. The biodiversity-biomass relationship has become a major ecological focus worldwide over recent decades [5,6]. Tropical rainforest plays vital roles in maintaining human life by providing water resources, food, medicine, oxygen and also absorb the carbon dioxide in the atmosphere which can reduce the amount of pollution that can effects in global warming, thus disturbing our biodiversity in the forest. It is very crucial to maintain the diversity 2nd International Conference on Tropical Resources and Sustainable Sciences IOP Conf. Series: Earth and Environmental Science 549 (2020) 012037 IOP Publishing doi:10.1088/1755-1315/549/1/012037 2 contain in our forest but they are now becoming smaller and fragmented due to human activities such as uncontrollable logging and shifting cultivation which leads to forest degradation thus, bring to the loss of habitat for flora and fauna.
For instance, Ulu Sat Forest Reserve (USFR) has been gazetted as protection forest for water reservoir by Kelantan State in 2019. While Bukit Bakar Forest Eco Park, is one of three eco park in Kelantan; i.e. Jeram Linang and Telaga Tujuh. As recreational forest, the stress put onto these forests in terms of conservation increases in conjunction with tourism activities. It has led to pollution like littering, solid waste dumping and water pollution. Thus, it is crucial to document the species composition, diversity and tree biomass of these recreational forest to show whether the implementation of PRFs in Peninsular Malaysia helps to mitigate species loss or otherwise. However, there are just few studies done in Bukit Bakar Forest Eco Park. The data of this study will help to value the important of this forest.

Study area and tree enumeration
Bukit Bakar Forest Eco Park, Machang is located in the Bukit Bakar Forest Reserve ( Figure 1). It is situated at 5.7182°N, 102.2598°E and covers an area of 3.14 hectares that managed under Forestry Department Kelantan. A total of five plots of 20 m x 20 m were established and trees with diameter at breast height (dbh) with ≤ 5 cm were enumerated and identified. Each plot locations details such as coordinate and altitudes are summarised in Table 1. Bukit Bakar Forest Eco Park is lowland dipterocarps forest with ranging altitudes between 300-700 m above sea level (a.s.l). In each plot, all trees with diameter at breast height (dbh) with ≤ 5 cm were measured and tagged. Leaves specimens of each measured tree were collected for preparation of voucher specimens and for species identification. Species identification was based on keys in Tree Flora of Sabah and Sarawak Volume 5 [7], Malaysia Plant Red List: Peninsular Malaysian Dipterocarpaceae [8] and with assistance of experienced botanists.

Data Analysis
All identified trees were tabulated according to family, genus and species. Ecological parameters considered in this study were species composition, basal area, relative abundance and species diversity indices. Formula proposed by [9] were used in this study: The importance of family and species in the community were determined by calculating the Importance Value Index (IVi) and summing parameters, such as relative density (Rd), relative dominance (RD) and relative frequency (Rf) [10]. = IVi = RF + Rd + RD (3.3) d) Tree species diversity at the study area was determined using Shannon-Wiener's Index (H') [11].
s = number of species pi = the proportion of individuals or the abundance of the its species expressed as proportion of total abundance ln = log base n  [12]. EH = H' / H'max = H' / log S (3.5) Where: S = Total number of species in the sample H' = Shannon-Weiner diversity index f) Simpson's Index (D) [13].

Floristic Composition
A total 135 trees with diameter at breast height of less than 5 cm were censused in five plots at Bukit Bakar Forest Eco Park, Machang comprising of 17 species, two genera and one family. The distributions of each species corresponded with their natural habitat where some species were found at the elevation below from 400 m while some species can be found up to 800 m. Table 2 shows the total number of individuals for all species found in Bukit Bakar Forest Eco Park and its natural habitat as mentioned by [8]. Thus, it proves the statement from [14], where the natural territory of most of the Dipterocarpus spp. and Hopea spp. was at wet lowland evergreen rainforest. According to [15], species abundance is related to the species richness. Table 2 shows the data analysis of species abundance of genera Dipterocarpus and Hopea in the study area. In that table, it demonstrates that Dipterocarpus crinitus Dyer has the highest abundance followed by Dipterocarpus baudii Korth and Dipterocarpus cornutus Dyer. This is because most of the area in Bukit Bakar Forest Eco Park was sandy clay soil, which it was suitable habitat for this species to be occurred.
Therefore, during the data collection, most of the species presence was D.baudii, D.crinitus and D.cornutus. However, Dipterocarpus caudatus Foxw. ssp. Penangianus (Foxw.) P.S.Ashton had the lowest value of species abundance in that study area. This is because the optimum habitat for this species was on the area that has type of soil which is flooded sandy clay alluvium. Bukit Bakar Forest Eco Park probably was not suitable for the growing of D.caudatus Foxw. ssp. Penangianus (Foxw.) P.S.Ashton. However, species distributions are also strongly aggregated with respect to variation in topography, soil water and soil nutrient status [16,17,18,19].
Trees with dbh ≤ 5 cm were censused because most of trees in the study area are observed in small dbh. Whilst, Hopea spp. of which had lower abundance compared to Dipterocarpus spp., these values was divergent for each species because of few factors, it may due to the gap formation. There were various amount of gap can be found in the Bukit Bakar Forest Eco Park, one of the example for gap formation was lightning gap. These gaps have influences or interference the presence of species frequency by develop species heterogeneity [20].

Importance Value Index (IVi)
The Importance Value Index (IVi) is one of the importance calculations for this study. The IVi values frequently applied in the ecological studies to determine the value of any species toward the ecological significance. Based on Table 2, it shows that Dipterocarpus crinitus Dyer has the highest IVi=17.73 while Dipterocarpus sublamellatus Foxw. and Hopea beccariana Burck both have the lowest value IVi=4.89.
Species that have the highest important value index indicate that they have higher relative dominance than other species that were found in the study area. According to Dash et al. [21], the highest IVi value in the study area represent an absolute dominance in the tree layering. Species that have low IVi may be influenced by few factors such as poor distribution in the study area or the competition that exist between that species with other species from different families [22].

Species Diversity
The value of all diversity indices used to calculate the diversity is summarised in Dipterocarpaceae was not only was demonstrated high species diversity in this study but also in previous studies in Peninsular Malaysia. For instance, at Bangi Permanent Forest Reserve, the species diversity recorded for one ha study plot was 6.99 (H'max=7.45) with the evenness of 0.85 [24]. The value was higher compared to this study. However, the diversity of trees sampled in different ecosystems may vary. At a Redang Island from two plots of 0.1 ha showed the Shannon-Weiner   Hopea. This is may consider because one factor that may influence the biomass content is dbh [25].

Conclusion
Based on the floristic pattern and species diversity calculation two genera Dipterocarpus and Hopea showed that Bukit Bakar Eco Park had a high diversity and density of tree species. Even though the study area was small, it proved that both genera Dipterocarpus and Hopea contains high floristic composition that consist of high frequency, density and abundance. As one of the main eco park sites in Kelantan, the habitat disruption has a higher tendency to be happened especially contributed by human activities. The above ground biomass showed Dipterocarpus spp. had high above ground biomass although the dbh of trees ≤ 5 cm. These data would be useful to a proper management and conservation strategy for this area and to maintain its function as water reservoir for several districts in Kelantan. The results from this study can be used as a basic guideline for other ecological studies on the whole Ulu Sat Forest Reserve (USFR), especially the study of the involving a larger landscape in the future.