Oil Palm Bulletin 81 (November 2020) p. 1-8 Floristic Composition and Carbon Stock Assessment of the Tinbarap Conservation Forest Kho Lip Khoon*; Elisa Rumpang* and Ivan Chiron Yaman** ABSTRACT berdekatan dengan kawasan penanaman sawit. Dua plot berkeluasan 1 ha (Tinbarap Conservation Conserving carbon density of tropical peat swamp Forest: TCF1 and TCF2) disediakan untuk bancian forest is an important indicator of environmental and pokok hutan (dengan diameter ≥10 cm ketinggian agronomical impact of oil palm. Understanding the paras dada). Purata biomass pokok hutan bagi carbon stock contribution from management within kedua-dua plot kajian TCF tersebut adalah sebanyak oil palm areas to retain forest patches and other 92.6 mg ha-1. TCF mempunyai kepelbagaian flora set-asides containing natural forest may become sebanyak 27 famili dan 69 spesies. Pemeliharaan increasingly important in the context of assessing kawasan hutan untuk konservasi dalam kawasan the potential contribution to the global carbon cycle penanaman sawit terutamanya di ekosistem gambut and one of the most critical strategies for sustainable adalah kritikal bagi pemuliharaan hutan dan plantation. However, quantification of carbon stock kelestarian industri sawit. of tropical peat swamp forest patches for conservation within oil palm plantations is poorly studied. Here, INTRODUCTION we aim to assess the above-ground biomass and flora diversity in a remnant forest patch of approximately Tropical peatlands contain around 3% of the global 210.63 ha adjacent to oil palm plantation. Two 1 ha soil carbon stocks and about 20% of global peat Tinbarap Conservation Forest (TCF1 and TCF2) carbon (Page et al., 2010; 2004). The largest area study sites were established to conduct census on of tropical peatlands occurs in Southeast Asia, all trees (≥10 cm diameter breast height). The total where they are found in Indonesia (predominantly carbon stock of both TCF sites was 92.6 mg ha-1. The Sumatra, Kalimantan and West Papua), Malaysia TCF contains flora from 27 families comprising 69 (Peninsular Malaysia, Sarawak and Sabah), Brunei species. Conserving forest patches, particularly in and Thailand (Rieley and Ahmad-Shah, 1996). peatlands, is important for conservation goals and The most pervasive threat to such carbon- and sustainable palm oil industry. biodiversity-rich peatland is the conversion of tropical peat swamp ecosystems to agricultural ABSTRAK crops (Sodhi et al., 2004; Carlson et al., 2013). With world food demand expected to more than double Pemuliharaan kandungan karbon hutan paya by 2050 (Tilman et al., 2002), agriculture is likely to gambut tropika adalah faktor penting terhadap continue to drive declines in natural ecosystems and the species they contain for the foreseeable future kesan persekitaran dan agronomi penanaman sawit. (Edwards et al., 2010). Responsible management of Pemahaman tentang peranan stok karbon dari aspek existing agricultural land and where to create new pengurusan penanaman sawit bagi pemeliharaan croplands, particularly on tropical peatland will hutan adalah semakin penting bagi potensi subangan therefore have profound effects on the conservation terhadap kitaran karbon global dan merupakan salah of biodiversity, including socio-ecnonomic satu strategi penting untuk penanaman lestari. development in Southeast Asian region (Sachs et al., Walau bagaimanapun, kajian untuk pemuliharaan 2009). dan pengukuran stok karbon kawasan hutan paya gambut tropika dalam kawasan penanaman sawit There is a critical need to protect forests masih kurang. Objektif kajian ini adalah untuk within agricultural development and responsibly menilai kandungan biomas dan kepelbagaian develop plantations in tropical forest landscapes, flora di hutan paya gambut seluas 210.63 ha yang particularly peat swamp forests. Considerable leading companies in the oil palm industry have taken the initiative to protect High Conservation * Malaysian Palm Oil Board, Value (HCV) area. HCV concept is a standard to 6, Persiaran Institusi, Bandar Baru Bangi, ensure the maintenance of significant or critical 43000 Kajang, Selangor, Malaysia. environmental and social values as part of E-mail: [email protected] responsible management (Brown et al., 2013). ** Sarawak Oil Palms Berhad, No. 124 126, Jalan Bendahara, This study aims to assess the biomass and flora 98007 Miri, Sarawak, Malaysia. diversity in a remnant forest patch set aside for 1 Oil Palm Bulletin 81 conservation (hereafter regarded as the Tinbarap RESULTS AND DISCUSSION Conservation Forest or TCF) in Tinbarap Estate of Sarawak Oil Palms Berhad (SOPB). The assessment The TCF area can generally be categorised as logged- will provide essential information on carbon stocks over mixed peat swamp forest. The original forest and species diversity in a conserved area of mixed type was dominated by Padang Paya forest based peat swamp forest. Specifically, the objectives are to on the vegetation sub-type or phasic communities i) provide estimates of carbon stocks, and ii) assess described by Andersen (1963). The TCF contains floristic composition. flora from 27 families comprising 69 species. Families and species found in the TCF are listed in METHODOLOGY Table 1. The most abundant families were Lauraceae and Dipterocarpaceae while the most abundant Study Site species were Dryobanalops rappa and Litsea crassifolia (Figure 3). The forest has generally not The study was conducted in the TCF area fully recovered as there is still a strong dominance (4°3’N, 114°13’E) of Tinbarap Estate in the Marudi of pioneer species reflecting past disturbance to the District of the Miri Division, between Sg. Karap and forest stand. Batang Tinjar-Batang Baram (Figure 1). The TCF is a logged mixed peat swamp forest of approximately The common tree height classes found in both 210 ha (Figure 2). The peat swamp is basically flat TCF1 and TCF2 were between 10 cm and 20 cm and low-lying, with elevation varies from about (Figure 4). The mean height of trees (≥10 cm DBH) +2.0 m mean sea level (msl) to +9.0 m msl at the estimated following the most recent census (2008) central part of the peat swamp. The soils mainly was 11.9 ± 0.2 m (mean ± SE) on TCF1 and 11.7 ± 0.2 comprise of peat soil of the Anderson series. The m on TCF2. The mean height of canopy trees (≥40 soils of TCF and estates have been previously cm DBH) across 10-ha plot was 26.3 ± 1.7 m. described in detail by ECOSOL (2007) and Param Agricultural Soil Surveys (2010). The mean annual The above-ground woody biomass (trees ≥ 10 –1 rainfall of the region is around 2863 mm. cm DBH) assessed in 2016 was 100.6 mg ha on TCF1 and 84.6 mg ha–1 on TCF2. For larger trees (≥40 cm DBH), the above-ground woody biomass We established a 10-ha study plot in the TCF, in was 24.6 mg ha–1 on TCF1 and 11.3 mg ha–1 on which were two 1-ha plots of TCF1 (4°3’N, 114°13’E) TCF2. Across 10-ha plot, biomass of larger trees was and TCF2 (4° 3’N, 114°13’E) as representative sites relatively similar to TCF1 with biomass of 27.6 mg and future monitoring. The 1-ha plot was further –1 ha . The number of trees (>10 cm DBH) on clay (529 divided into 25 subplots measuring 20 x 20 m. –1 stems ha ) was substantially lower than on TCF2 (535 stems ha–1). Estimation of Above-ground Biomass Endangered and Threatened Species Tree census was conducted in two phases: Phase 1 was on 19-26 September 2014, Phase 2 was on 12- The identification of endangered (EN), or 21 November 2014. Prior to the surveys, two recce threatened species of flora was referred based on trips were made; 25 February 2014 and 26-29 August the IUCN Red List (IUCN, 2019) and combined 2014. A census was conducted on all trees with a together with reference to Sarawak Plant Red List diameter of more than 10 cm breast height (DBH) to (Julia et al., 2014) that covers the dipterocarps of determine the height, growth rate, and recruitment Sarawak as well as Turner (1995) on the listing of of new trees. We mainly follow the methodology vascular plants. and protocol developed by the RAINFOR-GEM network, which are described in detail in the Based on the IUCN and Sarawak Plant Red manual (GEM, 2012). It has been tested and refined List, the Gonystylus bancanus was the only critically in previous studies (Kho et al., 2013; Malhi et al., endangered species found in the TCF during the 2013; Malhi, 2012). Above-ground woody biomass survey. The Table [redlist] shows the conservation of each free was estimated as a function of DBH status according to the IUCN and Sarawak Plant and height using an allometric equation for mixed Red List. The Gonystylus forbesii Gilg. is the only species peat swamp forest by Manuri et al., (2014): species classified as critically endangered under the IUCN classification. The Dryobalanops rappa AGB = 0.081 x DBH2.049 x H0.672 (1) Beccari of dipterocarps family has been classified as endangered under IUCN and should be conserved. where AGB is above-ground dry biomass (kg), DBH (cm) is diameter at breast height of 1.3 m, and Environmental Impacts on Flora H is height (m). Biomass values were converted by assuming that dry-stem biomass has a carbon The peat swamp forest ecosystem is an content of 47.4% (Martin and Thomas, 2011). extraordinarily complex ecosystem that is rich in 2 Floristic Composition and Carbon Stock Assessment of the Tinbarap Conservation Forest Figure 1. The location of Tinbarap Estate (shaded yellow) in the Marudi District of Miri Division. Figure 2. 10-ha plot (shaded orange) established in the Tinbarap Conservation Forest (TCF) area (shaded green) in Tinbarap 4 Estate, Miri, Sarawak. 3 Oil Palm Bulletin 81 TABLE 1. LIST OF FAMILIES AND SPECIES FOUND IN THE PROJECT SITE Family Species Prefered vernacular name Anacardiaceae Campnosperma coriaceum (Jack) Hall.