Vascular Plant Composition and Diversity of a Coastal Hill Forest in Perak , Malaysia

Vascular plant species and diversity of a coastal hill forest in Sungai Pinang Permanent Forest Reserve in Pulau Pangkor at Perak were studied based on the data from five one hectare plots. All vascular plants were enumerated and identified. Importance value index (IVI) was computed to characterize the floristic composition. To capture different aspects of species diversity, we considered five different indices. The mean stem density was 7585 stems per ha. In total 36797 vascular plants representing 348 species belong to 227 genera in 89 families were identified within 5-ha of a coastal hill forest that is comprises 4.2% species, 10.7% genera and 34.7% families of the total taxa found in Peninsular Malaysia. Based on IVI, Agrostistachys longifolia (IVI 1245), Eugeissona tristis (IVI 890), Calophyllum wallichianum (IVI 807), followed by Taenitis blechnoides (IVI 784) were the most dominant species. The most speciose rich families were Rubiaceae having 27 species, followed by Dipterocarpaceae (21 species), Euphorbiaceae (20 species) and Palmae (14 species). According to growth forms, 57% of all species were trees, 13% shrubs, 10% herbs, 9% lianas, 4% palms, 3.5% climbers and 3% ferns. Diversity indices were higher along the stream side and species accumulation curve showed sampling area captured a high proportion of the species richness.


Introduction
South-east Asian tropical rainforest with its unique and high proportions of endemic plants need greater effort in studying biodiversity.This unique flora result largely from millions years of independence evolution during the Tertiary, when wide oceanic barriers made dispersal between regions (Morely 2003), and have survived the convergence of New Guinea with Southeast Asia (Primack and Corlett 2005).Cataloguing total species richness in any country or region special in tropical and subtropical region is highly demanding (Villasenor et al. 2005) to provide information for managers, environmental planners, nature reserve designers and ecologists (Sang 2009) and a global map of plant diversity will powerfully inform biogeographical and conservation work in many ways.Bidin and Latiff (1995) estimated about 12500 species of the seed plants in the flora of Malaysia and Turner (1997) enumerated 8198 species in Peninsular Malaysia including 632 fern species, 27 Gymnosperms, 5529 Dicotyledons, 2010 Monocotyledons within 248 families and 1651 genera.Based on recent updates, the flora has over 8300 species (Kamarudin and Turner 2004, Latiff and Turner 2002a, 2002b, 2003).Most attempts to explain the variation in floristic composition of hill and lowland forest in Peninsular Malaysia have focused on woody stems (≥1 cm) (Abdul Hayat et al. 2010, Okuda et al. 2003, Condit et al. 1996, Awang Noor and Faridah Hanum 2008) rather than small individuals.Factor causing variation in species richness may differ between life forms of plants.A comparison of various life forms allows a finer resolution of precise casual factors.Thus, in the present study, we analysed the richness of different life forms along elevation gradient (45-350 m a.s.l.), floristic composition and diversity of vascular plants in a coastal hill forest from Pangkor Island in Perak, Peninsular Malaysia.

Study area
This study was performed in Sungai Pinang Permanent Forest Reserve.Pulau Pangkor (Fig 1) is an island located on the west coast of Peninsular Malaysia between 04° 13.0'N latitude and 100° 33.0´E longitude.It is one of the famous and well known islands in Malaysia with area of eight square kilometres and classified as coastal hill fo (Meteorology 1820.23 mm minimum occ Lumpur).The mainly sandy  In addition, we tested two more indices, the Chao and Jackknife estimators of species richness that are based on the incidence (presence/absence) of species.

Methods a
The Chao index (Chao 1984

Floristic composition
In total 36797 vascular plants representing 348 species belong to 227 genera in 89 families were identified (Appendix 1), two could only be identified to genus, one climber and three herbs were remained unknown within five 1-ha of a coastal hill forest that comprises 4.2% species, 10.7% genera and 34.7% families of the total taxa found in Peninsular Malaysia.Plant density was 7358 individuals per ha.Agrostistachys longifolia (IVI 1245), Eugeissona tristis (IVI 890), Calophyllum wallichianum (IVI 807), followed by Taenitis blechnoides (IVI 784) were dominant species (Table 1, 2).The most speciose rich families were Rubiaceae having 27 species, followed by Dipterocarpaceae (21 species), Euphorbiaceae (20 species) and Palmae (14 species), while more than 23 families were singletons (represented by only one species).Euphorbiaceae had the largest number of individuals (5.5% of plants), followed by Guttiferae (5%), and Dracaenaceae (4.8%).Table 3 shows the number of species and individuals according to growth form.Plants were distributed according to growth forms as follows: 57% of all species were trees, 13% shrubs, 10% herbs, 9% lianas, 4% palms, 3.5% climbers and 3% ferns.Evidently, trees show more equitable distribution of species across plots and most of them are economically important.Tree species like Agrostistachys longifolia, Calophyllum wallichianum, Xanthophyllum affine and Swintonia floribunda were the most populated species.
This island harbours 122 medicinal species (Burkill 1935) in 98 genus and 57 families; Rubiaceae (12 species), Guttiferae (10 species), Dracaenaceae (7 species), Euphorbiaceae (6 Sspecies), Araceae and Zingiberaceae (4 species each) were the most speciose medicinal families (Appendix 1).The dominant climber and liana species were Scindapsus scortechinii representing 35% of climbers (74% of individuals) and Dalbergia parviflora representing 26% of lianas (1.3% of individuals), respectively.Leguminosae, Connaraceae and Araceae were the most species rich climber families (woody and non-woody).Lianas are dependent on trees for their support, and thus the availability of suitably sized support is a major factor controlling the abundance and distribution of lianas (Putz and Holbrook 1991).The common species in herbaceous layer were Globba variabilis and Etlingera metriocheilos.Eugeissona tristis was a dominant palm, Dracaena pendula a dominant shrub, and Taenitis blechnoides was a dominant fern.
Table 4 also shows the percentage of medicinal and endemic species according to growth -forms.In Malaysia there is over 1000 medicinal species (Latiff et al. 1980) and about 13% of these species are found in this forest.
Species composition and number of individuals differed between plots (Figure 2).Distribution of plant species in natural vegetation is usually not stochastic.It occurs in patterns that are present at several spatial and temporal scales.Each species is expected to be most abundant where the environmental conditions are most favorable for it.In this study variation in plant community structure and composition were attributed to the characteristics of physical environment.The number of herbs in the first plot were higher than the other plots, simply the presence of stream was a factor that favoured higher values of diversity (Gazol and Ibanez 2010) and some species located in streamside environments.
Altitude is a factor which is correlated with resources and regulators of plant growth (Kazakis et al. 2007).In this study linear regression of plant richness against altitude was significant (Figure 3).Third plot showed a trend of decreasing richness for most growth forms with increasing altitude and the main reason is altitude.The negative influence of elevation on diversity has been widely reported in studies (Gazol and Ibanez 2010, Odland and Birks 1999, Körner 2002, Pickering et al. 2008, Wang 2006).Overall, elevation showed significant linear regression with herb, liana, fern and tree (Table 5).Although the number of trees reduced with increasing elevation, the number of trees with dbh ≥5 cm in higher altitude was noteworthy (the details on distribution of trees species will be published soon in a different paper).
Regression of elevation and palm, climber, epiphyte and shrub richness showed no significant relationship (Table 5).Daque et al. (2002), Ruokolainen and Vormisto (2000) and Ruokolainen et al. (2002) indicated that palms are less sensitive to environmental effect and more wide-spread than smaller plants.
Orchidaceae is the most speciose family in the flora of Malay Peninsula with 853 species (Turner 1997).In our study, however, this family was poorly represented (only 5 species) and most of them appeared in the second and third plots in upper canopy crowns to get maximum sea breeze.

Species accumulation curve
Hill and Hamer ( 2002) believed communities should be sampled adequately (usually assessed with species accumulation curve).Species accumulation curve shows how species richness increases until eventually the curve levels off with increasing sample size and the number of individuals inventoried.The graph suggests that our sampling area captured a high proportion of the species richness; the point at which the curve flattens indicates a minimum viable sample size on which a diversity or richness index should be based (Magurran 1988).
Figure 4 shows the curve based on the area sampled stabilized in third plot.Tropical ecologists believe species richness reaches an asymptote at 1-3 ha (Gentry 1988, Tuomisto et al. 1995, McLaren, et al. 2005).Faridah Hanum et al. (2008) in a case study in a logged-over forest in Ayer Hitam Forest found out increasing the size of study area more than five hectare did not have any increment on species richness.

Species Diversity
A variety of diversity measures were computed to describe the heterogeneity of the plots.All diversity indices, including non-parametric estimators, increased with the number of individuals in a sample (Table 6).The majority of the 300 species (82% of total species) inventoried appeared in the first plot, and therefore this plot is characterized by high diversity (215, 146, 182, 154 species found in plots 2 to 5, respectively).The Fisher's alpha is low when the number of species is low.This index is less affected by the abundance rarest or commonest species diversity (α) range from 25.46 to 51.38 and the average for all plots is 35.23.The Shannon-Winner's index measures the average degree of ''uncertainty'' in predicting to what species individuals chosen at random will belong (Ludwig and Reynolds 1988).Uncertainty may be visualized as being synonymous with diversity (Krebs 1999), therefore, the higher the degree of uncertainty, the higher the diversity.Diversity index fell within high range (3.54 to 4.98) while the average for all plots gave H'= 3.99.Simpson index proposes that diversity is inversely related to the probability that two individuals picked at random from a sample belong to the same species.Simply stated, if the probability is high the diversity is low.Simpson's index varies from 18.09 to 45.43 and the average is 27.62.According to this index the first plot was more diverse than the others; this could be related to the relatively large number of abundant species.The evenness is considered high when it varies near value of 1.When all species are abundant, an evenness index would be maximum and decrease towards zero as the relative abundances increase.In this study area the average of Simpson's measure of evenness is low.

Conclusion
The quantitative inventory of a coastal hill forest helps to complete the description of biodiversity and plant composition.Our results indicate this forest with 55 endemics and 13% of medicinal species found in Malaysia is unique and offer numerous non-tangible benefits such as invaluable storehouse of genetic resources useful for indigenous species.Diversity indices are still widely used in plant ecology to evaluate survey and conserve ecosystems and using richness estimators can improve our evaluation of diversity.Plant diversity is influenced by a multitude of environmental factors, but in this study area streamside was the main factor in determining diversity and majority of herb species were found near the stream.
Monitoring studies such as the current one are of utmost importance and provide insights into the responses of coastal hill forest to climate change and also because this island is a tourist's attraction place, the future inspection need to see the changes according to number of species.

Five
the total number of species represented by a single individual S 2 = the total number of species represented by two individuals And the jackknife index (Chao 1984the total number of species represented by a single individual S 2 = the total number of species represented by two individuals

Table 1 .
The 20 most abundant species in Sungai Pinang Permanent Forest Reserve in Pulau Pangkor, Perak according to increasing order of IVI

Table 2 .
The 20 least abundant species in Sungai Pinang Permanent Forest Reserve in Pulau Pangkor, Perak according to increasing order of IVI RDE=relative density, RF= Relative frequency, IVI=Importance Value Index

Table 3 .
The number of species and individuals according to growth form in five 1-ha plot in Sungai Pinang Permanent Forest Reserve in Pulau Pangkor, Perak

Table 4 .
The percentage of medicinal and endemic species between growth-forms in five 1-ha plot in Sungai

Table 5 .
The result of ANOVA and linear regression of growth-forms against elevation

of species Subplots species accumulation curve
Appendix 1.Total list of species in five 1-ha plots in Sungai Pinang Permanent Forest Reserve in Pulau Pangkor,