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ZAKARIA et al. 1 Comparison of plant communities at six study plots in Penang forestreserves, Malaysia RAHMAD ZAKARIA, ASYRAF MANSOR*, NIK FADZLY, NIK ROSELY & MASHHOR MANSOR School of Biological Science, Universiti Sains Malaysia, 11800 Minden, Pulau Pinan, Malaysia Abstract: An analysis of plant communities from six study plots within the Penang forestreserves, Malaysia, revealed 359 plant species with stems ≥ 2.0 cm diameter. More than 70percent of trees were below 10 cm diameter at breast height (DBH). Total Above GroundBiomass (TAGB) and Basal Area (BA) varied between sites, with the highest value (631.15 tha -1 ) at Bukit Panchor Forest Reserve (Land) and the lowest (112.83 t ha -1 ) at Bukit PanchorForest Reserve (Swamp). Based on the species list, the study plot could be divided into twogroups, the mainland and the island group. In general, intact forest haboured relatively highernumber of woody species than the disturbed forest. The species composition was clearlydifferent between island and mainland forests. Resumen: Un análisis de las comunidades vegetales de seis parcelas de estudio en lasreservas forestales Penang, Malasia, arrojó la cifra de 359 especies de plantas con tallos ≥ 2.0cm diámetro. Más de 70 por ciento de los árboles tuvieron diámetros a la altura del pecho(DBH) < 10 cm. La biomasa aérea total (BAT) y el área basal (AB) variaron entre sitios, siendoel valor más alto (631.15 t ha -1 ) el de la Reserva Forestal de Bukit Panchor (tierra) y el másbajo (112.83 t ha -1 ) el de la Reserva Forestal de Bukit Panchor (pantano). Con base en la listade especies, las parcelas de estudio se pueden dividir en dos grupos, el de tierra firme y elinsular. En general, el bosque intacto albergó un número relativamente mayor de especiesleñosas que el bosque perturbado. La composición de especies fue claramente diferente entrelos bosques insulares y los de tierra firme. Resumo: Uma análise das comunidades de plantas em seis parcelas de estudo no interiordas reservas florestais de Penang, Malásia, revelou 359 espécies de plantas com troncos ≥ 2,0cm de diâmetro. Mais de 70% das árvores apresentavam um diâmetro ao nível do DAP abaixodos 10 cm. A biomassa aérea total (TAGB) e a área basal (BA) variou entre estações, com ovalor mais alto (631,15 t ha -1 ) na Reserva Florestal de Bukit Panchor (terra firme) e a maisbaixa na Reserva Florestal de Bukit Panchor (Pântano). Com base na lista de espécies, aparcela estudada foi dividida em dois grupos: a continental e a insular. Em geral, a florestaintacta abrigava um número relativamente mais alto de espécies lenhosas do que a florestaperturbada. A composição das espécies era claramente diferente entre as florestas insulares eas continentais. Key words : Basal area, forest type, forest reserve, Penang island, speciescomposition, total aboveground biomass. * Corresponding Author; e-mail:
[email protected] Tropical Ecology 50 (2): 259-265, 2009© International Society for Tropical Ecologywww.tropecol.com ISSN 0564-3295 260 PENANG FOREST RESERVES Introduction Tropical forests are rated as among the world’simportant biodiversity hotspots due to theoccurrence of high number of species. Speciesrichness is one of the most important measures of community structure and is one of the most crucialquestions asked in the field of ecology. This isespecially true in the tropical regions, such asMalaysia, where biodiversity is high (Laurance2007).The correlations between causes and effects of species diversity intrigued since long bothnaturalists as well as ecologists such as Darwin(1859) and Hutchinson (1959). Many studies havebeen conducted to examine the patterns of diversity at temporal scales ranging from seasonalchanges to evolutionary time as well as spatialscales ranging from meter-square plots tolatitudinal gradients (e.g. Crimmins et al . 2008;Halpern & Spies 1995; Leigh et al. 2004; Takyu etal. 2005). Global awareness on biodiversity alsohelps to guide the design, implementation andimprovising existing policy on natural resourcesmanagement (Harris 1984; Kessler et al . 1992),thus making the effort to quantify the speciesdiversity as a major task for many scientists.Enumerations of species richness provide the verybasis for research, conservation and managementof the forest, although it is usually restrictedrelatively only to small portion of the forest systemdue to logistic and time constraints.Forest studies on specific locations in Penang,Malaysia are limited (e.g. Raich & Turner 1990;Turner 1989, 1990), therefore, this study wasundertaken to gather information particularly onplant communities in the five forest reserves inPenang. This paper will provide a basic ecologicalinsight on the status of Penang forest reserves.Hopefully, this study would also initiate a morethorough and indepth study of these valuableforests. Materials and methods Study sites Six study sites have been established inJanuary 2004, in five forest reserves of PenangIsland and Seberang Perai, Malaysia (Table 1, Fig.1). Annual rainfall varies from 2000 to 2500 mmand mean daily temperature ranges between 21and 32ºC. A 20 x 20 m study plot was establishedin each site to census the vegetation. The samplingarea was marked with PVC pipes for futurereference. Plant censuses were conducted over aone year period between February 2004 andJanuary 2005. All the six forest areas are shown inFig. 1, and their locations, forest types, and mostabundant species are listed in Table 1. Table 1. Location details of six study plots distributed over five forest reserves in Penang, Malaysia. Names of the most abundant species, one for each site, are given in parantheses. Area Location Forest TypePantai Acheh Forest Reserve (PAFR)Penang Island100 º 11’ 35.44” N5 º 27’ 52.67” ECoastal hill forest( Shorea maxwelliana )Teluk Bahang Recreational Forest (TBFR)Penang Island100 ° 13’ 55.79” N5 ° 26’ 56.88” ELowland forest( Calophyllum wallichianum )Bukit Kerajaan Forest Reserve (BKFR)Penang Island100 ° 15’ 25.14” N5 ° 25’ 31.25” EHighland forest( Syzygium bernardi )Bukit Mertajam Forest Reserve (BMFR)Seberang Perai Tengah100 º 30’ 13.91” N5 º 22’ 10.19” ELowland forest( Garcinia atroviridis )Bukit Panchor Forest Reserve (BPFR-L)Seberang Perai Selatan100 ° 32’ 51.70” N5 ° 09’ 16.43” ELowland forest( Macaranga trichocarpa )Bukit Panchor Forest Reserve (BPFR-S)Seberang Perai Selatan100 ° 33’ 24.61” N5 º 08’ 54.50” ESwamp forest( Pyrenaria acuminate ) ZAKARIA et al. 261 Fig. 1. Map showing the location of research plots inPenang State. See Table 1 for site acronyms. Census method The most effective and acceptable method tostudy and quantify species diversity and richnessis plot sampling method (e.g. Condit et al. 1996;Shimida 1984). All free-standing woody plantspecies within the plots were sampled. All stems ≥ 2.0 cm diameter at breast height (DBH at 1.3meter) were measured, tagged and mapped topossible nearest 0.01 meter for DBH, 0.5 meter forheight (Condit et al. 1996; Hubbell & Foster 1983;Manokaran & Swaine 1994) and 0.1 meter forindividual location. Leaves, fruits, barks andspecial characters (sap, latex and smell) of individual trees were collected / recorded forfurther identification when needed. Identificationwas based on Whitmore (1983) and Ridley (1967). Voucher specimens are deposited at the herbariumof School of Biological Sciences, Universiti SainsMalaysia (USM), for further reference.Total above ground biomass (TAGB) was calculated from the formulae based on DBH (Kato et al . 1978) as below: W S (stem) = 0.313(D 2 H) 0.9733 W B (branch) = 0.136(W S ) 1.070 W L (leave) = 1.25(0.124W S º .794 )0.124W S º .794 + 125TAGB = W S + W B + W L where, D = Diameter at breast height (DBH) incm, H = Total height in m. Basal area (BA) and tree density were alsocalculated for the most dominant species for eachsampling plot. From the data collected, a speciesdiversity analysis using statistical software MVSP(Multi Variate Statistical Programme) ver 13.3d byKovach Computing Services (2002) was conducted.The Simpson’s unbiased index, Shannon’sdiversity and evenness indices were also calculatedfrom the species diversity results using the sameMVSP software. To increase normality, data forspecies occurrences were log transformed (Krebs1989). Results A total of 729 individuals from 359 differentspecies have been sampled with mean density of standing trees calculated at 3051 stems ha -1 .Based on species occurrence, thirteen mostcommon plant families were recorded from all sixplots although the number varied from one plot toanother. In terms of family occurrence, mostcommon is Euphorbiaceae whilst Lauraceae,Fagaceae, Polygalaceae are among the leastcommon families. Anacardiaceae is a major family,though relatively confined to coastal forestsnamely PAFR and TBFR (Table 2) . The highest number of species per plot wasrecorded in BKFR (74 species), and the lowest (40species) in BMFR. Number of species per plot forthe remaining study sites ranged from 57 to 66species (Fig. 2). As for the number of standingtrees, we recorded the highest number (161 treesper plot) in BKFR and the lowest in BMFR (56trees per plot). Table 2. Three most important plant families from each of the research plots. Site names as in Table 1. Research sites FamiliesBKFR Myrtaceae, Lauraceae and FagaceaeBMFR Euphorbiaceae, Clusiaceae and RubiaceaeBPFR(L) Euphorbiaceae, Fabaceae and MyristicaceaeBPFR(S) Theaceae, Euphorbiaceae and PolygalaceaePAFR Anacardiaceae, Dipterocarpaceae and MoraceaeTBFR Anacardiaceae, Clusiaceae and Myrtaceae 262 PENANG FOREST RESERVES Smaller sized plants (< 10 cm DBH) were moreabundant in all study sites (Fig. 3) than the biggersized trees, reaching to almost 95% of total treepopulation in BKFR. The TAGB for BPFR-L washighest (Fig. 4) despite the small number of biggersized trees (> 10 cm DBH) recorded at this site.The proportion of standing trees under 10 cm DBHfor all the study plots was more than 70% andtheir contribution to overall TAGB was very low.In addition, the BA was also highest for trees > 10cm DBH (Fig. 5) suggesting that for some reasons,timber trees in BPFR were not logged in the past. Fig. 2. Relation between species number and familycount for the study plots. Individual tree count ishighest in Bukit Kerajaan Forest Reserve (BKFR),located on the Penang Island, than Bukit MertajamForest Reserve (BMFR) in the mainland. In general,number of families across all study sites fluctuatesbetween 17 to 27 . See Table 1 for site acronyms. Fig. 3. Percentage of trees in different dbh classes.The impact of previous logging activities is clearlyshown in Bukit Kerajaan Forest Reserve study plot.The percentage of bigger size trees (dbh>10 cm) atthis forest reserve is the lowest in comparison withother forest reserves. See Table 1 for site acronyms. Fig. 4. Comparison of total above ground biomass(TAGB) for six study plots of five forest reserves inPenang, Malaysia. Data suggested that standingtrees in lowland forest of Bukit Panchor ForestReserve (BPFR(L)) are bigger in size than other studyplots. See Table 1 for site acronyms. Fig. 5. Comparison of basal area (BA) for the studysites. Data from study plots in both Bukit KerajaanForest Reserve (BKFR) and Teluk Bahang ForestReserve (TBFR) suggested that basal area forstanding trees is comparatively the same. See Table 1for site acronyms. Two distinct groups could be identified usingthe UPGMA dendogram (Fig. 6) differentiating themainland and the island forests. Sorensen’scoefficients for species similarities are less than0.2 for all study plots suggesting that these plotscontain many different species as shown in Fig. 6.Unlike the species similarity coefficients, thefamily clusters are separated into 3 groups, andBPFR-S and BPFR-L show the highest similaritiesat about 0.7 even though the sites are situated in adifferent area (Fig. 7). Two coastal forest reserves, 16058111107107119744066645857251727252723020406080100120140160180BKFRBMFRBPFR-LBPFR-SPAFRTBFRPlot N u m b e r IndividualsSpeciesFamily ZAKARIA et al. 263 namely TBRF and PAFR are distinctively groupedtogether implying possible unique characteristicsof these forests to harbour trees of certain families. Fig. 6. Dendrogram showing the species similaritiesbetween the study sites. Two separate groups can bedistinguished, group (a) BPFR (S & L) and BMFR,and (b) PAFR, TBFR and BKFR, as lowland-mainland forest and coastal-island forest, respecti-vely. See Table 1 for site acronyms. Fig. 7. Dendrogram showing the family comparisonbetween the study sites based on Sorensen’scoeffiecients. Three groups can be distinguished; (a)TBFR and PAFR, (b) BPFR (L) and BPFR (S), and (c)BMFR and BKFR. Discussion This study provides a comprehensive estimateof presently available TAGB of Penang ForestReserves. The key conclusion is that the biomass of these forests, ranging from 112.83 t ha -1 to 637.15t ha -1 , is considered a high value for such a smallarea, compared to the other tropical areas (Ng &Low 1982). Our result is similar to the findingsreported by Aiken & Leigh (1992) and Turner(1989) from their studies. In Malaysia, manyspecies of trees can occur within a relatively smallarea. The lowest number of species recorded in aforest reserve (i.e. BMFR) can be related togeographical condition of the study plot orevidence of anthropogenic activities (e.g. logging).We strongly suggest that the human intrusionfactor has played a major role leading to the lowspecies count of this research plot rather thangeographical condition. Although the TAGB for BPFR-L wascomparatively high, results from the six researchplots are still within the range of TAGB valuesreported by Kato et al . (1978) in their studies of Malaysian forests. This suggests that mostMalaysian forests contain almost the same rangeof TAGB. Between the study sites, we found thatthe TAGB varied and did not show any specificpattern. The high number of smaller treessuggests that these forests are indeed rich in juvenile trees, which is a good sign of a healthyand a continuously growing forest, becausematured forests usually contain a low number of small trees (Aiken & Leigh 1992; Shuttleworth1981).The BA for the study plots is related to theTAGB, hence any changes in individual tree datawill result in the change of overall BA and TAGB.The lowest BA and TAGB recorded from BPFR (S)could be due to the location, as the site is situatedin swampy area and is often submerged underwater in the rainy season. It is very likely that dueto this constant waterlogged condition, overalltrees here are smaller in size (see Fig. 3) andshorter in height due to poor nutrient supply.Furthermore, the substrate structure here is notsuitable for the growth of big trees, as it is boggyand consists mainly of decomposed organic matterand plants can easily be uprooted by strong wind(Zimmerman et al. 1994).Distinct grouping of study plots (Fig. 7)indicates that, plants in Malaysian tropical forestsare more or less concentrated around a few mainand big families such as Dipterocarpaceae,Fabaceae, Anacardiaceae and Sapotaceae (Corner1988). BMFR and BKFR are examples of asituation where species similarity is low but theyshare a high family similarity.Referring to the Shannon’s index value(species count), we can imply that all the six plotshave uniformally high diversity and evenness (allthe values ranged from 0.9 to 1.0 for Evenness andfrom 1.6 to 1.8 for Diversity index) (Table 3). Thereare two possible reasons as to why Bukit Kerajaanecological plot shows a higher diversity index UPGMA Sorensen's Coefficient BKFRTBFRPAFRBMFRBPFR(L)BPFR(S) 0.040.20.360.520.680.841 UPGMA Sorensen's Coefficient BKFRBMFRBPFR(L)BPFR(S)PAFRTBFR 0.520.60.680.760.840.921
