Above Ground Biomass and Tree Species Diversity in Anap Sustainable Development Unit, with the Focus on the High Conservation Value Forest (HCVF)
[Hiromitsu Samejima, Malcom Demies, Miyako Koizumi]

Above Ground Biomass and Tree Species Diversity in Anap Sustainable Development Unit, with the Focus on the High Conservation Value Forest (HCVF)
Hiromitsu Samejima(Center for Southeast Asian Studies, Kyoto University)
Malcom Demies(Sarawak Forestry Cooperation)
Miyako Koizumi(Graduate School of Agriculture, Kyoto University)

 Maintenance of biomass or carbon stock and biodiversity are among the targets of sustainable forest management (SFM) and establishing a high conservation value forest (HCVF) is one of the measures of SFM to achieve these targets. However, the performance of HCVF management has not been well studied.
 Inside the Anap Sustainable Development Unit (ASDU), Sarawak, Malaysia, four HCVFs and three water catchment areas (WCs) have been established. WCs in ASDU were originally listed as a part of HCVFs in the Forest Management Plan for Anap-Muput Year 2006–2025, and accordingly can be considered part of HCVFs in ASDU.  In ASDU, we established 70 vegetation plots to evaluate the aboveground biomass (AGB) and tree species diversity in the management area. Using these data, we evaluated the contribution of HCVFs in sustaining the high biomass and rich biodiversity of ASDU.

Materials and Methods
Study site
 ASDU is located in Tatau District, Bintulu Division, Sarawak, Malaysia. It is managed by a private company, Zedtee Sdn Bhd. ASDU covers an area of 106,820 ha, and its forests can be classified into three types: lowland/hill mixed dipterocarp forest (MDF), Kerangas forest, and riparian forest. MDF is the major forest type in lowland Borneo and ASDU. Kerangas forest is a heath forest on sandy nutrient-poor soil, distributed in the southeast part of ASDU. Riparian forest is a type of MDF distributed along rivers but generally more degraded and with lower densities of large trees than normal MDF on the slopes and ridges, probably because the riparian area is more vulnerable to logging disturbance.
 The management system of ASDU is divided into three parts: Anap-Muput Forest Management Unit (FMU: T/4317), which forms the main part; an area with License for Planted Forest (LPF/0039) in the northern part; and Anap-Belawit state land in the south (Fig. 1). The Anap- Muput FMU is divided into coupes and managed in a 25- year cutting cycle for sustainable timber production of indigenous tree species such as meranti (Shorea spp.) and kapur (Dryobalanops spp.). Logging activity in ASDU started in 1977, all the coupes have been harvested at least once, and coupes 1–12 have been harvested again in the last 12 years. LPF is allocated for intensive planting of fast-growing species, and the original vegetation has been repeatedly harvested, but most of the area has not been planted to date.

Table 1: List of plots. Numbers in parentheses show numbers of plots established by Koizumi.

Table 1: List of plots. Numbers in parentheses show numbers of plots established by Koizumi.

Figure 1: Locations of plot areas.

Figure 1: Locations of plot areas.

Figure 2 : Measuring DBH and marking Figure 3 : For a tree with high buttress, DBH was
measured at above the buttress. Figure 4  : Metal number tag, attached on all trees. Figure 5 : SFC staff collected the tree specimens
for identification in Kuching. Table 2: The number of trees and species, and amount of above ground biomass (ton / hector) in each plot. Table 3: The number of genera, species and trees
in each family recorded in the 70 plots in ASDU.
 In ASDU, H. Samejima and J. Hon established eight plots to conduct camera-trapping surveys for grounddwelling, middle, and large-sized mammals from 2011 to 2013 (Samejima & Hon 2014). One plot is a circle with 1-km diameter and eight cameras are set inside at randomly selected points. Hon also established a 2-km line transect along each of the three rivers where natural salt licks were present and conducted a camera trap survey from 2010 to 2011 (Hon 2011; 2013; Hon & Shibata 2013).
 In ASDU, Zedtee established four HCVFs, HCVF1–4. Demies and Sang (2008) established six quadrats in HCVF1, three in HCVF2, nine in HCVF3, and five in HCVF4 in 2008. Each quadrat was of 50 × 50 m. They recorded all trees belonging to three genera of Dipterocarpaceae, Dipterocarpus, Dryobalanops, and Shorea with diameter at breast height (DBH) of ≥10 cm.

Vegetation plots
 From 2011 to 2013, H. Samejima and M. Demies established 61 circle plots with radius 20 m (0.126 ha) and M. Koizumi established 9 circle plots with radius 15 m (0.071 ha) distributed in 19 areas (Table 1, Fig. 1, Koizumi 2012). The distances between the neighboring plots within an area were approximately 100 m. A total of 18 plots were positioned in three HCVFs and two WCs. HCVF3 and WC_Ayam are covered by primary forests, and theother two HCVFs and one WC are covered by old-growth forest that was harvested during the 1980’s. Four plots in HCVF1 and two plots in HCVF3 overlap the quadrates established by Demies and Sang (2008). 11 areas were set up the eight plots and along the three transects for the camera trap study. The other four areas were selected to include the other vegetation types. C06b is a swampy area where trees were harvested 7 years ago, and C06c is mostly primary forest remaining along a steep ridge in coupe 6.
 Inside each plot, we measured DBH and heights of all trees with DBH (at 130 cm above ground) of ≥10 cm. We painted a red line at the height where DBH was measured (Figs. 2, 3) and attached a metal number plate (Fig. 4) for future re-census. All trees were identified by staffs of Botanical Research Center, Sarawak Forestry Corporation and Koizumi, referring to the herbarium of Sarawak Forest Research Center, Kuching (Fig. 5). The classification followed the Angiosperm Phylogeny Group III system.
 There are three formulas for estimating AGB of tropical moist forest (FAO 1997, Chave et al. 2005):

1) AGB = exp ( -2.977 + ln (ρD 2H ) )
2) AGB = ρ × exp ( -1.499 + 2.148 ln (D ) + 0.207( ln (D ) )2 – 0.0281( ln (D ) )3 )
3) AGB = exp ( -2.134 + 2.53 ln (D ) )
ρ : Wood specific gravity D : Diameter at breast height H : Total tree height

 Following these formulas, we obtained three estimates, AGB1, AGB2, and AGB3, of the AGBs of all trees. Wood specific gravity data were based on Lemmens et al. (1995), Oey (1951), Soerianegara and Lemmens (1993), and Sosef et al. (1998) following Imai et al. (2012). In case wood specific gravity of a genus was unknown, we used AGB3 as a substitute for AGB1 and AGB2 for the tree. As Koizumi did not measure the tree heights, we calculated only AGB2 and AGB3 for her data.

 In total, we recorded 6,302 trees in the 70 plots (Table 2), including 968 species of 223 genera and 70 families (Table 3). Dipterocarpaceae was the most dominant family, representing 31.6 % of all trees (1,989 trees and 131 species). HCVFs and WCs had a large stock of AGB (Fig. 6). The mean and standard deviation of AGB2 of all plots were 338.8 ± 197.1 t/ha, whereas those of plots inside HCVFs and WCs were 595.0 ± 157.1.  Species richness was not very different between HCVFs and WCs and normal logging areas. The average numbers of species were 137–170 in four plots (approximately 0.5 ha) of HCVFs and WCs and 159–176 in C16, C12, and C11 (Fig. 7).

Figure 6: Estimated above ground biomass of 19 areas.

Figure 6: Estimated above ground biomass of 19 areas.

Figure 7: Species rarefaction curve with number of species
against total area (hectare) of plots for 12 areas where more
than three 20-m radius vegetation plots wereestablished.
The number of species are average number of number of species in
1000 times randomly selected plots in each area.

Figure 7: Species rarefaction curve with number of species against total area (hectare) of plots for 12 areas where more than three 20-m radius vegetation plots wereestablished. The number of species are average number of number of species in 1000 times randomly selected plots in each area.

 HCVFs and WCs had higher biomass or carbon stock than normal areas that were subjected to logging operations. AGB remained low even 22 or 24 years after the last logging (C16 and C14). Whereas AGB2 in C12, just after harvest, was 227.8 ± 28.0 t/ha, only 280.2 ± 115.6 and 221.2 in C16 and C14, respectively. Although one of the reason of the low biomass stocks in C16 and C14 may be due to the slow speed of biomass recovery under the specific environmental conditions in the two areas (e.g., soil), our results indicated that the biomass of logged-over forests does not recover to the state of unlogged forests during the standard logging cycle of 25 years in ASDU. Thus, HCVFs and WC areas are valuable for showing the original and potential status of standing volume or carbon stock in ASDU.
 However, the species richness in HCVFs and WCs was not obviously higher than that in normal logging areas. Even areas harvested recently, for example C12 and C11, had many species as HCVFs and WCs. The current logging system is considered not too harmful in reducing the species richness of the original forest.
 In this study, metal number tags were attached to all enumerated trees. As these metal tags can remain intact for a long time, future surveys such as measuring DBH can be performed and will allow the determination the growth rate of these trees. Among potential uses of such information is the calculation of annual growing speed, which in turn can be used to revise the annual allowable cutting volume for sustainable timber production.
 The presence of the primary forests in HCVFs and WCs inside ASDU is of high advantage for the management of FMU, given that few existing FMUs in Sarawak retain such original habitats to show the original forest conditions inside FMU.

 We thank the staff of Sarawak Forestry Corporation, Rantai Jawa, Tinjan Kuda, and Shalih bin Rebi, who helped in conducting the fieldwork and the identification of tree species. We also thank the managing director of Zedtee Sdn Bhd, Wong Ing Yong; his staff, John Tasan and Wong Toh Meo; and the other staff in Sekawie Camp and Ayam Camp for their support during the field work. We also thank our local assistants who helped in our field work. We thank Jason Hon, WWF Malaysia, who introduced us to ASDU, helped conduct this study, and also edited this report. This study was financially supported by a Grant-in-Aid for Scientific Research (S) 22221010 from the Japan Society for the Promotion of Sciences and permitted by Forest Department of Sarawak (NCCD.907.4.4 (Jld.7) -67).

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1:E-mail: lahang.lejau@gmail.com

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