THE MALAYSIAN FORESTER 72 (1): 117-133 (2009) COMMUNITY STRUCTURE, DIVERSITY AND BIOMASS OF TREES IN TWO FOREST SUBTYPES OF PEKAN FOREST RESERVE, PAHANG, MALAYSIA ISMAIL, P., 1 * NIZAM, M.S., 2 FARIDAH-HANUM, I., 3 1 1 1 KHALI AZIZ, H. , SHAMSUDIN, I., SAMSUDIN, M. AND A. LATIFF 2 1 Forest Research Institute Malaysia (FRIM), Kepong 52109 Selangor, Malaysia. 2 School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia. 3 Faculty of Forestry, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. * Corresponding author: [email protected] Abstract: Two one-ha ecological plots representing Kempas-Ramin-Durian and Durian-Nyatoh forest subtypes were established in Compartment 156 and Compartment 200, respectively at Pekan Forest Reserve, Pahang to determine community structure, diversity and biomass of trees. All trees of 10 cm diameter at breast height and above were enumerated in the plots. Results showed that although tree stocking was almost similar in the two forest subtypes, the basal area, volume and total tree biomass were higher in the Kempas-Ramin-Durian subtype. Shannon-Weiner diversity index, H’ obtained in the Durian-Nyatoh subtype was however, significantly higher (p<0.05) than Kempas-Ramin Durian subtype. Morisita’s Index of Dispersion (Id) showed a random distribution pattern for both forest subtypes. Key words: Forest subtypes, taxonomic composition, community structure, INTRODUCTION The peat swamp forests (PSF) of the Pekan District, Pahang, which included the Pekan Forest Reserve (FR) was first classified using the photo-interpretation method (Chong 1965). A more comprehensive work in the South-East Pahang Peat Swamp Forest (SEPPSF) by Blackett and Wollensen (2005) recognized 13 forest subtypes; these subtypes were further refined by UNDP/GEF (2006) based on species distribution and dominance. Khali Aziz et al. (2007) described stand characteristics of tree communities in a Ramin-Bintangor forest subtype of SEPPSF as rich with commercial timber species such as Gonystylus bancanus (Ramin melawis) , Calophyllum ferrugineum (Bintangor) , Shorea platycarpa (Meranti Paya) , Tetramerista glabra (Punah), Koompassia malaccensis (Kempas) and Durio carinatus (Durian paya) . However, a detailed description on community structure of the remaining forest subtypes are still lacking, especially those with less economic values. It is deemed essential to obtain more ecological information on other forest subtypes in order to give a better picture of the Pekan FR for the relevant authorities to take significant management actions for achieving sustainable forest management. 117 P. Ismail et al. MATERIALS AND METHODS Plot Establishment The ecological plots were established in Compartment 156 for Kempas-Ramin- Durian subtype and Compartment 200 for Durian-Nyatoh subtype in Pekan FR (Figures 1 and 2). A one-hectare plot of 100 x 100 m was established; these plots were further divided into 25 contiguous subplots of 20 m x 20 m. All trees of 10 cm diameter at breast height (dbh) and above were identified, tagged, mapped and measured using a diameter tape at 1.3 m above the ground. Figure 1 . Location of Pekan FR in the South-East Pahang Peat Swamp Forest (SEPPSF). Data Analysis All trees enumerated in the ecological plots were summarized for overall taxonomic composition and quantitative data were analysed to determine abundance. These include determination of basal area, as well as calculating the density and frequency of occurrence of each species. Tree basal area ( BA ) was calculated using the equation as follows: BA = [ π x ( d2)/40000] (unit: m 2), where d is the diameter at breast height and π=3.142. The tree volume was calculated using an equation as follows: volume = BA x mht x 0.65 (unit: m 3), where mht is the merchantable bole height in meter. The 0.65 is a presumed factor applies to all trees (JPSM 1997). 118 THE MALAYSIAN FORESTER Zone Forest subtype RAM Ramin-Bintangor ( Gonystylus-Calophyllum ) MDX2 Mixed Kempas-Ramin-Durian ( Koompassia-Gonystylus- Durio ) BTG Bintangor ( Calophyllum ) BTGD Bintangor ( Calophyllum ) and Kelat ( Syzygium ) MERANTI Meranti paya ( Shorea ) D/N Durian-Nyatoh ( Durio-Madhuca ) MAH Kempas-Mahang-Durian (Koompassia-Macaranga-Durio ) DSB Logged-over and open areas RIV Riverine and open areas Figure 2. Location of the one-ha ecological plots in Compartments 156 and 200 of Pekan FR , and the forest suptypes based on UNDP/GEF (2006). Distribution analyses were carried out using Morisita’s Dispersion Index (Morisita 1959), while two indices, Importance Value Index ( IV i) (Brower et al. 1997) and Shannon-Weiner Diversity Index ( H’ ) (Shannon & Weaver 1949) were also calculated to determine species importance and species diversity of the forest subtypes, respectively. The IV i was calculated by summing up the values of relative density ( RD ), relative dominance (based on basal area) ( RB ), and relative frequency 119 P. Ismail et al. (RF ) of each species or family [ IV i = RD + RB + RF )/3]; whilst the Shannon-Wiener Diversity Index ( H’ ) was calculated using formula as follows: s H '= −∑ pi ln pi , where i=1 s = the number of species; pi = the proportion of individuals or the abundance of the ith species expressed as a proportion of total abundance; ln = log base n In addition, species richness index was also calculated using the Margalef’s Index (Margalef 1958), to determine species richness of the community, which is mainly based on the number of species occurring in the particular community as follows: s −1 D = ; where D = Margalef’s Index; s = total species number; and N = total log N number of individuals. Estimation of Tree Biomass In this study, total tree biomass was estimated using equations introduced by Istomo (2006) who developed the equations from a study at peat swamp forests in Sumatera, Indonesia. The equations used are as follows: Biomass (above-ground) = 0.0145 (dbh 3) - 0.4659 (dbh 2) + 30.64 (dbh) - 263.32 Biomass (below-ground) = 20.1% of Biomass (above-ground) Total plant biomass = Biomass (above-ground) + Biomass (below-ground) RESULTS AND DISCUSSION Taxonomic Composition A total of 557 trees of 10 cm dbh and above were enumerated in the plot at Compartment 156 which comprised of 68 species in 49 genera and 26 families (Appendix 1). Four families, i.e. Annonaceae, Guttiferae, Burseraceae and Myrtaceae were the most speciose families in which all of them were represented by six species (Table 1). The first two families contained three genera whilst the third and fourth family, i.e. Burseraceae and Myrtaceae were composed of two genera and one genus, respectively. Meanwhile, the study plot in Compartment 200 recorded a composition of 100 tree species in 76 genera and 37 families from 555 enumerated trees. The most speciose family was indicated by the Lauraceae and Myrtaceae that were represented by eight species, of which the former contained four genera whilst the latter had only one genus. As a comparison, Khali Aziz et al. (2007) revealed a composition of 67 tree species in 49 genera from 26 families. It is apparent that their findings were very similar to the results from this study at Compartment 156, and prior to their survey, Grippin (2005) conducted a post-felling inventory in a large area of Pekan FR that covered an area of 2,156 ha, where he reported 67 tree species occurring in the surveyed area. Nevertheless, Compartment 200 that was located near the Sungai Bebar, showed a higher species number compared to the Compartment 156 and reports of Khali-Aziz et al. (2007) and Grippin (2005). Preliminary survey on tree communities along the Sungai Bebar by Nizam et al. (2005) also highlighted a high number of tree species with a composition of 113 species in 66 genera from 35 families. Appanah (1997) reported as many as 84 tree species in their study at forested areas of Sungai Bebar. The high species number from this study in this 120 THE MALAYSIAN FORESTER compartment might be due to the difference in soil properties between compartments. Adzmi and Suhaimi (2005) stated that the peat swamp forests of the Sungai Bebar area was not purely of characteristics of a peat swamp forest. They concluded that the Sungai Bebar contributed significant influence to this factor, whereby the river deposited mineral soils along the river, which allows more species to occupy the area. Moreover, Che Aziz and Kamal (2005) mentioned that the Sungai Bebar area was very poor in peat development, and thus resulting of less characteristics of a peat swamp area. Table 1. Ten leading families with the highest number of species in both compartments at Pekan FR. Compartment 156 Compartment 200 Family No. of No. of No. of Family No. of No. of No. of species genus stands species genus stands Annonaceae 6 3 46 Lauraceae 8 4 32 Guttiferae 6 3 42 Myrtaceae 8 1 41 Burseraceae 6 2 47 Euphorbiaceae 7 6 66 Myrtaceae 6 1 43 Guttiferae 7 2 42 Lauraceae 5 3 20 Burseraceae 6 2 67 Myristicaceae 5 4 71 Leguminosae 5 5 19 Euphorbiaceae 4 4 94 Anacardiaceae 5 5 12 Leguminosae 4 4 12 Myristicaceae 5 4 37 Rosaceae 3 2 7 Annonaceae 5 2 20 Ebenaceae 3 1 14 Rubiaceae 4 4 6 Table 2. Abundance parameters of trees according to diameter classes in plots at Compartment 156 (C156) and Compartment 200 (C200), Pekan FR. Diameter Density (stem/ha) Basal area (m 2/ha) Volume (m 3/ha) Class (cm) C156 C200 C156 C200 C156 C200 10.0-24.9 358 425 7.56 7.84 40.79 45.25 (64.3%) (76.6%) (22.6%) (29.5%) (14.0%) (17.0%) 25.0-39.9 138 84 10.36 6.15 80.68 55.84 (24.8%) (15.1%) (31.0%) (23.2%) (27.8%) (21.0%) 40.0-54.9 41 32 7.27 5.30 74.29 68.57 (7.4%) (5.8%) (21.7%) (20.0%) (25.6%) (25.8%) 55.0-69.9 14 5 3.91 1.52 41.28 15.13 (2.5%) (0.9%) (11.7%) (5.7%) (14.2%) (5.7%) >70.0 6 9 4.34 5.73 53.29 80.75 (1.1%) (1.6%) (13.0%) (21.6%) (18.4%) (30.4%) Total 557 555 33.44 26.54 290.33 265.54 (100%) (100%) (100%) (100%) (100%) (100%) 121 P.