Floristic composition and species diversity at Gunung Inas forest reserve, Kedah, Peninsular Malaysia

Monoculture plantations such as Musang King durian farms on a big scale become a controversial issue due to its potential devastating impact to the diversity of forest reserves at some areas in Kedah including Gunung Inas Forest Reserve. This study intended to determine the floristic composition and species diversity at Gunung Inas Forest Reserve (GIFR), Kedah. Three plots of 70 m x 25 m covering 0.53 ha were established at GIFR. Each tree with diameter at breast height of 5 cm and above in the study plots were tagged, measured and identified up to species level. Voucher specimens were then taken for further identification purposes. The floristic composition of GIFR consists of 53 individuals represented by 16 species from 12 families. Anacardiaceae was the most speciose family with four species recorded. The most dominant species was Swintonia schwenkii (Anacardiaceae) with 14 tree individuals. S. schwenkii (Anacardiaceae) was considered to have an absolute dominance at the study site with Important Value Index (IVi) of 12.48%, meanwhile Myrtaceae recorded 20.87% of IVi, reflecting this family to be relatively dominant than other families. GIFR recorded moderate Shannon-Weiner Diversity index of H’ = 2.66 (H’max = 2.77) and Margalef’s Richness Index of DMG = 8.7. High Evenness Index of 0.71 portrayed that the tree species are almost equally abundant at the study area. The total tree biomass in the GIFR was estimated at 76.26 t/ha, contributed by 66.04 t/ha of above ground biomass and 10.22 t/ha below ground biomass. Data and information from this study can serve as a guideline for future ecological research and particularly in planning conservation efforts to ensure the biodiversity and sustainability of forests for future generations.


Introduction
Bintang Hijau range is ranked as the third leading large mountain range in Malaysia and is situated on the westicoast of Peninsular Malaysia.Approximately 140 km of this range originate from Bukit Besar, Thailand and concludes at the central part of Perak state.Gunung Bintang (1,862im) is the highest summit in this mountain range, followed by Gunung Bintang Utara (1,835im) and Gunung Inas (1,801im), which is located in the state ofiKedah.Since the abiotic environment of montane forest ecosystems frequently varies dramatically over elevational gradients, these habitats are an excellent starting point for research on biogeographic diversity.Montane forests are frequently confined to constrained geographic regions that are inclined to topographical fragmentation, further endangering these ecosystems.However, research on tropical montane cloud forest ecosystems has accounted for only 5% of biodiversity studies in contrast to 74% for lowland forests in Southeast Asia throughout the past 20 years.
Gunung Inas Forest Reserve (GIFR) is based in the district of Baling, Kedah and is a part of Bintang Hijau range.This forest reserve is administered by the South Kedah Forest Department.GIFR covers 1316 (2024) 012005 IOP Publishing doi:10.1088/1755-1315/1316/1/012005 2 around 37,000 ha of lowland dipterocarp, hillidipterocarp, upper montane and lower montane forests [1] [2].However, 9,583 ha (2.80%) of total Gunung Inas Forest Reserve (GIFR) was developed for monoculture plantation, mainly for TLCs and Musang King durian in 2017.This plantation development is also located on the Ecological Network Area of the Central Forest Spine (Primary Linkage 5), as detailed in the Central Forest Spine (CFS) Masterplan and National Physical Plan.The CFS has crucial mountain basins and watersheds that serve about 90% of the Peninsular Malaysia's population water supply.It regulates the climate, protects the soil, sequesters the carbon, as well as provides a habitat to a variety of biota, including the Malayan tiger subspecies and Asian elephants which are critically at risk of extinction.Monoculture plantation can pose a threat towards the diverse species of flora and fauna as well as the ecosystem of the forest.
To date, a fair number of studies on species biodiversity have been conducted in the state of Kedah such as in Ulu Muda forest reserve [3], Sungai Merbok forest reserve [4] with Gunung Inas forest reserve unexcluded from the list.However, most studies conducted in Gunung Inas Forest Reserve were mainly focusing on reptiles and amphibians' diversity rather than tree species diversity.Inventories on tree species are employed in the forest management activities as a way to ascertain the biodiversity and distribution of tree individuals in the study area.The total number and the total basal area of trees represent the spatial distribution of tree individuals within the forest as well as the spatial distribution of distinct species in relation to one another.This data is beneficial to advance understanding of the forest diversity whilst supplementing conservation initiatives to prolong the sustainability of the forest for next generations.Therefore, this study was executed to determine the floristic composition and diversity of tree species at Gunung Inas Forest Reserve (GIFR), Kedah, as there were lack of tree species research from this study site.

Tree sampling
Quadrat sampling was conducted devise tree inventory in which three plots measuring at 70 m x 25 m (0.53 ha) were randomlyaestablished at GIFR.Each tree possessing diameter at breast height (DBH) of 5 cm and above were tagged and quantified at 1.3 m above the ground [5].The specimens for all measured trees such as leaves and fruits were collected for the preparation of voucher specimens and for species identification.The morphological characteristics were also compared to herbarium specimens from Universiti Kebangsaan Malaysia and the nomenclature was obtained using keys described in Tree Flora of Malaya by [6].Besides, Keys in Malaya's Tree Flora [7] and The International Plant Name Index [8] was used as a reference for nomenclature of the tree species.

Data analysis
Data of all tree communities were tabulated and summarized to describe floristic composition of Gunung Inas Forest Reserve, Kedah.Species accumulation curve was constructed using Ecosim version 7 to represent the adequacy of the sampling effort in the study area.The abundance parameter includes density and basal area determination, while the Importance Value Index (IVi) was determined to estimate the species importance in the community.The IVi was derived by adding the values of each species or family relative density (RD), relative dominance, and relative frequency (RF) [IVi = RD + RB + RF)/3] [9].Three ecological indices which are Shannon-WeineraDiversity Index, Evenness Index and Margalef's Richness Index [10] were applied to compute the species diversity and richness of the study area by using Paleontological Statistic Software Package for Education and Data Analysis (PAST) Software version 2.17c [11].Total biomass of tree species was estimated by adding up the above ground biomass (AGB) [12] and below ground biomass (BGB) [13] using the allometric equations.

Floristic composition
A total of 53 trees with diameter of breast height (DBH) of 5.0 cm and above were recorded in the 0.53 ha of study plots at Gunung Inas Forest Reserve (GIFR).Identification of all samples showed that 53 trees belong to 16 species and 16 genera from 12 families (Table 1).Family consisting the most species number in this study site was Myrtaceae with four recorded species (25% of total species) namely Eugenia oleina, Gymnacranthera bancana, Palaquium burckii and Pometia pinnata.Myrtaceae also was recorded as the most abundant family with 14 tree individuals altogether whilst Swintonia schewenkii (Anacardiaceae) had the highest number of trees with 12 tree individuals, followed with P. burckii (Myrtaceae) and Eugenia stellata (Myrtaceae) with eight and six tree individuals recorded in GIFR, respectively.It is also worth noting that there are singleton families or families with single species and single individuals recorded in the study site which were Dipterocarpaceae, Hypericaceae Myristicaceae and Sapindaceae.Table 2 shows the comparison of tree species composition from various forest reserves in Peninsular Malaysia.[14] reported that a total of 63 families from 138 genus and 228 species were encountered in Lesong Forest Reserve, Pahang.In addition to that, Bukit Panchor State Park, Pulau Pinang [15] composed a total of 42 families, 112 genera and 171 species whilst [16] recorded 53 species and 47 genera from 25 families in a 0.98 ha Bukit Lagong Forest Reserve, Selangor.As a comparison to this study with a sample size of 0.53aha, GIFR shows the least total of tree species composition which might be caused by the smaller sampling size of the study area.This result and comparison also implied that a larger sampling size supports more species and tree individuals in a forest.

Species richness, diversity and evenness
Species richness is one of the important characteristics for tropical rainforests in which this parameter will be incorporated in the calculation of species diversity [17].Malaysian forests are rich in plant diversity attributable to Malaysia's geographically stable conditions which provide desirable living environment for vast array of plants to thrive [18].Biodiversity indices such as Shannon-Weiner Diversity Index is generated to quantify species diversity in different habitats to a similar scale of comparison.By using Shannon Diversity Index, there are also other indices that can be obtained such as maximum possible species diversity (H'max) and Evenness index (E).GIFR recorded the Shannon-Wiener Diversity Index (H') of 2.66 (H'maxa= 2.77) which was lower in comparison to other tropical rainforests (Tablea3).For instance, a study conducted by [21] revealed that Gunung Belumut Recreational Forest has a H' value of 4.82 (H' max = 5.66) whereas Redang Island with H' = 4.05 (H' max = 4.52) [20] and Kota Damansara Forest Reserve at H' = 3.43 (H'max = 4.54) [22].The low value of the diversity index indicates that GIFR has poor level of species diversity which correlates with the stature of GIFR as a secondary forest.The previous deforestation causes the forest to be less diverse than the primary forest.Low Shannon-Weiner Diversity index value obtained in the present study was also caused by the small sampling area (0.53 ha) compared to the other studies mentioned in Table 3.In addition to that, the abiotic components of GIFR could be less hospitable for variety of tree species and limiting them to inhabit the forest reserve.Different species inhabit different ecosystems according to their growth requirement [23] such as elevation and edaphic factor.
This study recorded Evenness index (E) of 0.71 and Margalef index (DMG) of 8.7 (Table 3).As of evenness index, the value is constrained from 0 to 1, with the value of 1 signifying a condition in which all species are distributed equally within the study area.Nonetheless, the value is considered low compared to the other tropical rainforests such as Gunung Belumut Recreational Forest with E = 0.85 and DMG = 21.37 and Bangi Permanent Forest Reserve (E = 0.85 and DMG = 18.8).It can be inferred that the low species richness is associated to the anthropogenicaactivities that occurred in the present study thus, impacting the abundance of tree species.According to [10], Margalef's richness index relies on the size of the sample which are the number of trees and number of species that are present at the study area.Thus, this explains low richness index obtained in GIFR because of the number of tree individuals at only 53 trees and 16 species encountered altogether in the study area in comparison to other study site such as Bukit Panchor State Park where higher Margalef index of DMG = 23.19 is recorded because of higher number of trees (n = 488) and species (n = 149).

Species accumulation curve
Species accumulation curve (SAC) can be defined as the graph recording the cumulativeanumber of species of living things recorded in a particular environment [24].Species accumulation curve depicts how species richness increase until eventually the curve levels off with increasing sample size and the number of individuals inventoried.The SACs displayed a positive correlation between species richness and sampling effort (Figure 2), signifying that additional species discoveries are probable with increased sampling intensity.Notably, the curves did not plateau within the 0.53 ha area encompassed by our plots.This outcome suggests that the current sampling effort might not have been sufficient to capture the complete spectrum of tree species residing within GIFR.Moreover, tropical ecologist believed that tree species richness in some area can reach an asymptote at 1-3 ha [25].This fact is in line with previous study of 1.0 ha of Ulu Muda Forest Reserve, Kedah which had reach an asymptotic condition indicating that the sampling size had captured maximum proposition of species richness [14].4 shows the DBH classes for number of tree individuals including all study plot at GIFR.DBH of trees at GIFR ranges between 5.0 cm to 65.0 cm.Most of the tree recorded in this study falls into DBH class II (15.0-24.9cm) which was represented by 20 individuals from eight families, eight genus and ten species.The second most tree individuals were recorded in DBH class I (5.0-14.9cm) at 16 trees belonging to seven seven genus and 11 species.Meanwhile, only one individual represented DBH class VI (55.0-64.9cm) which can be classified as large tree.S. schwenkii was the leading large tree species in the present study at a recorded DBH of 58.2 cm.According to [26], the changes in population structure and species composition of forest ecosystem can be indicated by the tree size.Figure 3 shows the stand structure of trees in all study plots at GIFR and it results in an inverse J-shaped pattern of DBH classes.The inverse J-shaped reveals negative exponential relation in population size between DBH classes.In this study, the distribution of trees clearly displays the characteristic of the inverse J-shaped distribution in which the number of tree individual decreases as the DBH of tree increases.This generally indicates that stands are developing and regeneration in the forest is present.Natural regeneration is dependent on the availability of mother trees, fruiting pattern and favourable conditions [27].J-shaped pattern indicates smaller tress are dominating the forest compared to large trees in relation to DBH.Although it is not a perfectly inverse J-shape, the pattern was similar and in line with several studies conducted in various types of forest such as Pulau Timun Forest Reserve [28], Pulau Langkawi Forest Reserve [28], Bukit Nanas Forest Reserve, Kuala Lumpur [29] and Bangi Permanent Forest Reserve [19].Thus, it is proved that the inverse J-shape is common in tropical forest as a lot number of juvenile tree growing and a smaller number of old trees in tropical forest.

Figure 3.
Stand structure in all study plots at GIFR.

Importance value index
Importance value index (IVi) is a metric used in ecology to quantify the relative dominance of a particular tree species or family within a specific forest area [30].This index will be calculated to find out the dominanceaof a family or species at this study site.According to [9], in order for an individual to be considered to have absolute dominant over the other the rest of other individuals (strongly influence the community), the value of IVi is required to exceed 40% on the family level whilst the IVi must exceed 10% on species level.Species with highest IVi in the present study was S. schwenkii with 12.48%, followed by E. oleina with species importance value index (SIVi) of 8.09%, Parashorea stellata with SIVi at 1.73%, P. burckii with SIVi at 1.0% and Cinnamomum camphora with SIVi of 0.88% (Table 5).From the findings, we can conclude that S. schwenkii strongly influenced the community with SIVi more than 10% while the other species such as E. oleina, Cynometra malaccensis, Palaquium burkii and Artocarpus schortecinni has no absolute dominance but they are just relatively dominant compared to other species in the present study.Family-wise, Myrtaceae has the highest family importance value index (FIVi) at 20.87%, followed by Anacardiceae (24.78%),Fabaceae (10.36%),Annonaceae (7.30 %) and the last but not least, Lauraceae at 6.57% (Table 5).The result shows that none of the families in the study plots can be considered to have absolute dominance because the FIVi obtained is less than 40%.Nonetheless, these five leading families can be considered relatively dominant as compared to other families in the study plot.[14] revealed, Euphorbiaceae as the most important family in Bukit Bauk Virgin JungleaForest (BBVJR), Lesong ForestaReserve (LFR) and Gunung Belumut RecreationalaForest (GBRF) with FIVi of 27.95% (BBVJR), 26.09% (LFR) and 27.16% (GBRF).In addition, the predominant species based on the highest SIVi for all of the study plots was Dryobalanops aromatica with IVi of 17.81%, 23.01% and 16.25% in BBVJR, LFR and GBRF, respectively.Obviously, D. aromatica could be considered to have an absolute dominance among the tree communities of the study plot.

Biomass estimation
The total biomass of trees in the present study was estimated at 76.3 t/ha.From this amount, a total of 66.04 t/ha was contributed by the above ground biomass (AGB) and 10.22 t/ha was contributed by the below ground biomass (BGB).Estimating biomass of a tree typically requires the use ofaallometric equations.The value was formerly derived from destructive sampling of trees to measure their biomass directly, after which biomass is correlated with non-destructive measurements, such as diameter and height [31].Based on Table 6, Anacardiaceae contributed the highest biomass in GIFR with 31.28 t/ha (41%), followed by Myrtaceae at 12.93 t/ha (17%), Dipterocarpaceae at 9.95 t/ha (13%).Anacardiaceae also recorded as the highest contributor of biomass in a forests of other studies such as Bukit Panchor State Park with 250.7 t/ha (36.5%) [15] and also Redang Island with a total of 141.36 t/ha of estimated biomass (39%) [20].

Conclusion
This study displayed that GIFR has a small size of floristic composition and supports low tree species diversity.The floristic composition and species diversity of trees in GIFR could also be influenced by various abiotic factors such as edaphic factor and topography.This study is only at its preliminary stage, thus, to gain more accurate results and more understanding on the abiotic factor impacting the distribution of trees, it is recommended to further conduct this study in a larger sample size.GIFR have a little scarcity of information in floristic composition of tree species, thus a larger sampling area will contribute to more discovery of tree species that inhabit the forest reserve.In future, it is recommended to take into account the soil parameter as one of the factors that might influence tree species distribution.This study has potential to support the conservation and preservation of any species of interest in GIFR.

Figure 2 . 6 3. 4
Figure 2. Species accumulation curve plotted for each tree plots in GIFR Note: Total is the combination of all individuals in three plots of GIFR.

Table 1 .
Number of genera, species and individuals for all families encountered in the study plots of Gunung Inas Forest Reserve, Kedah.

Table 2 .
Comparison of floristic composition from previous study on various forest types in Peninsular Malaysia.

Table 3 .
Shannon-Wiener Diversity Index (H'), H'max, Evenness (E) and Margalef Index (DMG) values from this study and other studies from various forest types in Malaysia.

Table 4 .
DBH classes of number of tree individuals of all study plot at GIFR.

Table 5 .
Importance value index of three leading species in the study plots at GIFR.

Table 6 .
Total biomass of three leading families in the study plots at GIFR.At species level, the highest value for total biomass was dominated by S. schwenkii with 31.29 t/ha (43.1%), followed by E. oleina with 19.39 t/ha (25.4%), C. malaccencis with 3.28 t/ha (4.26%), P. burkii and Artocarpus scortechinii with 3.28 t/ha (4.26%) and 2.59 t/ha (3.39%), respectively.For total biomass of trees at DBH of 5 cm and above in the Bukit Bauk Virgin Jungle Reserve (BBVJR) plot was estimated at 701.30 t/ha, whilst the Lesong Forest Reserve plot value was estimated at 739.44 t/ha and GBRF plot value was estimated at 606.29 t/ha.D. aromatica had the highest tree biomass in all of the study plots with a value of 292.88 t/ha at BBVJR plot, 421.85 t/ha at the LFR plot and 273.01 t/ha at the Gunung Berumut Reserve Forest plot.This shows that different forest habitats support different forest structure that resulted in variation of biomass.