Comparison between reduced impact logging and conventional logging in peat swamp forests in Indonesia

Transcription

1 Sepilok Bulletin 10: (2009) Comparison between reduced impact logging and conventional logging in peat swamp forests in Indonesia S. Suhartana*, Yuniawati & Rahmat Centre for Forest Product Research and Development, Bogor, Indonesia. or *Author for correspondence Abstract. Taking into account the functions, services and benefits of the tropical swamp forest ecosystem, this ecologically unique wetland, if well-managed, may contribute to the economic development of tropical developing countries such as Indonesia. Reducing forest damage during harvesting and using efficient harvesting techniques can actually provide more productive harvests. The aim of this study is to compare the impact of implementing reduced impact logging technique (RIL) and conventional logging technique (CLT) in terms of residual stand damage, ground exposure and logging/harvesting cost aspects. Measurements were made on damages, productivity rates, and productivity costs. The results show that RIL practice gives low forest damage impact, higher productivity, and low production cost. At present, CLT is more commonly practised. It is recommended that forest concession holders practise RIL for timber harvesting to sustain forest productivity. Further measures should be aimed towards promoting RIL at the operational level. Keywords: conventional logging, ground exposure, productivity, reduced impact logging, residual stand damage INTRODUCTION Indonesian tropical swamp forests have an important and strategic role in the management of forest ecosystems due to their unique forest characteristics. Their integrity and sustainable management are crucial for maintaining the regional as well as global environment (MacKinnon et al. 1996). The area of Indonesian tropical swamp forests accounts for about half of the world's total or 22 million ha (Rieley 2005). Of the world's peat swamp forests, Indonesia's are known to be of one of the highest biodiversity (Bellamy 1997, Lazuardi 2004). The Kalimantan tropical peat forests, for instance, are rich in highly commercial species such as Ramin (Gonystylus bancanus), Meranti (Shorea spp.), Jelutong (Dyera lowii), Nyatoh (Palaquium cochlearia), Bintangor (Calophyllum spp.) and Gluta renghas (Daryono 2000). In Indonesia, logging in peat swamp forests is still an important economic activity and operations are run by private logging companies. Since the Law No. 1, 1967 and Law No. 6, 1968 on foreign investment and domestic investment were passed, and followed by the government decision on promoting investment in logging, forest activities especially in Jambi, Riau, West Kalimantan and Central Kalimantan increased significantly and therefore play an important role 35

2 in supporting national development (Soebiato 1990). The legacy of the ambitious Mega Rice Project (MRP) relegated much of Kalimantan's peat swamp forests to treeless, non-productive, and degraded landscapes (Rieley 2005). Based on the TPTID system, the timber harvesting operations have to comply with approved felling practices in order to minimize environmental impacts. For this reason, developing appropriate methods of timber harvesting and extraction is highly required to promote good logging practices. The techniques used for felling and skidding may affect the log quality. Felling is a logging activity that involves tree cutting, branch cleaning, and bucking to required lengths. Felling is done by full mechanical, semi-mechanical or manual ways using chainsaw, axe handsaw (Staaf & Wiksten 1984). The use of chainsaws must be based on work standard implemented for reducing material, time and energy waste (Suparto & Elias 1983). Skidding is log extraction from felling site to temporary log yard (TPn) at the edge of transportation road. Skidding on tropical swamp forest is different from that on dry land forest. Log extraction is usually carried using "ongkak"2) for log skidding and logs are transported using lorries (Idris & Suhartana 1997, Suhartana 2000, Suhartana 2004). In general, mechanical logging results in the highest harvest rates (Suhartana et al. 2006, Suhartana 2000, Idris & Suhartana 1997, Loehnertz et al. 1996). However, this technique often causes serious forest damages (residual stand damage and ground exposure) due to mechanical tool operation, hasty work and inappropriate methods (Suhartana et al. 2006, Suhartana 2000, Idris & Suhartana 1997). In addition, timber harvesting results in negative impact on wildlife habitat as hunting and forest fragmentation increase (Meijaard et al. 2005). To avoid the unintended result, techniques that accommodate the economic and ecological requirements have to be implemented, because inappropriate techniques used in natural forest can lead to inefficient activity (Holmes et al. 1999, Grulois 2000, Seng et al. 2004). Applying reduced impact logging technique (RIL) in East Kalimantan, Indonesia and Malaysia can reduce stand damage by 30-50% (Pinard & Putz 1996, Bertault & Sist 1997). The two most important factors that need to be evaluated regarding damage to the forest environment are residual stand damage and ground exposure. This paper reports the results of a study on felling and skidding impacts using RIL and CLT on residual stand damage, ground exposure and logging cost in tropical swamp forests in Indonesia. 1) TPTI is a system where commercial trees with diameter of 50 cm and up in permanent production forest and diameter of 60 cm and up in limited production forest are removed, leaving a minimum of 25 young commercial and healthy trees with diameter of 20 cm and up per hectare and distributed in the area. The cutting cycle of the TPTI system is 35 years. This system is based on decree issued by the Directorate General of Forest Management No. 564/ Kpts/IV-BPHH/89 on silviculture system in natural forest. Ongkak is a wood tool for log skidding through a wood construction road at swamp forest. 36

3 MATERIALS & METHODS This study was conducted in tropical swamp forests in Sumatra (Jambi and Riau) and Kalimantan (West Kalimantan and Central Kalimantan), Indonesia in Data were obtained from both published and unpublished sources. RIL and CLT were compared with parameters of residual stand damage, ground exposure, and harvesting cost. T-test was used to analyze the differences between treatments. RIL is a well-planned logging technique covering all aspects of land-clearing (for forest road construction), felling (felling direction, felling cut, back cut), skidding (skidding operation is done after skidding road is ready), loading and unloading, and transportation. CLT is a logging practice in which all the operations are authorized to be done by the local operators. Terminology Tree damage in this study is defined as damage caused by logging, including injury to standing and uprooted trees, broken stem or crown, as well as damage to soil and environment. The level of tree damage is based on the ratio between the number of trees damaged and the number of trees in that area prior to logging minus felled trees. Forest ground exposure caused by felling is the open area caused by felled trees, while the ground exposure caused by skidding in swamp forest is the open area caused by "ongkak" road development. The factors which affect the ground exposure area are: (i) felling intensity; (ii) felling technique and cut direction; (iii) canopy throw-down area; (iv) felled trees distribution (diameter of 40 cm up); (v) length and width of skidding road; (vi) liana; and (vii) logging system (Kurniawan 2002). Tree damage RESULTS Tree damage caused by felling and skidding are influenced by the number of felled trees and tree density (Table 1). The higher the density, the greater the tree damage, especially in CLT. It can be seen from "B" and "C" for which tree density is 50.5 trees/ha and 100 trees/ha respectively, average tree damage is 24.9% and 28.54%. These damages were caused by felling and skidding activities that did not follow the RIL guidelines. 37

4 Table 1. The average tree damage (%). Activity Felling Skidding Details RIL CLT RIL CLT Average tree 4.96A 8.12A 19.8B 24.9B damage (%) 15.79c 28.54c Average number 5.67A 6.33A 8.75B 8B of felled trees 5.2c 5.6c (trees/ha) Average stand na na 76.5E 50.5E density (trees/ha) 123.2c 100c Remarks: A = Suhartana et al. (2006), N (number of observations) = 3; B = Suhartana (2004), N = 4; C = Suhartana et al. (2000), N = 5; RIL = reduced impact logging; CLT = conventional logging technique; na = not available. Ground exposure Results about ground exposure caused by felling and skidding are presented in Table 2, showing RIL causing less soil disturbance. For example, felling and skidding using RIL resulted in the average ground exposure of about 16.79% ("B") and 16.06% ("D") respectively. The average ground exposure caused by CLT is 19.84% ("C"). Based on these results, it can be seen that implementation of RIL on felling and skidding resulted in less ground exposure than CLT. Table 2. The average ground exposure (%). Activity Felling Skidding Details RIL CLT RIL CLT Average ground 8.75A na c exposure (%) 16.79B 16.06D 24.9D 5.72E Average number na na 5.2c 5.6c of felled trees 8.75D 8D (trees/ha) Average stand na na 123.2c 100c density (trees/ha) 76.5D 50.5D Remarks: A = Soerianegara (1995); B & E = Kurniawan (2002); C = Suhartana et al. (2000); D = Suhartana (2004); RIL = reduced impact logging; CLT = conventional logging technique; na = not available. 38

5 Harvest rates, efficiency and cost Table 3 shows the productivity of RIL felling and skidding is higher than CLT. "A" shows that RIL felling could increase the productivity by about m3/hour, while the RIL skidding could increase the productivity by about 6.16 m3.hm/hour ("C"). Table 3. Felling productivity (m3/hour) and skidding productivity (m3.hm/hour). Activity RIL CLT Felling Productivity (m3/hour) A A B B Log volume (m3) 3.140A 2.993A 2.818E 2.540B Felling time (hour) 0.104A 0.115' 0.095B 0.107B Skidding Productivity (m3.hm/hour) 20.51c 14.35c Log volume (m3) 3.38c 2.01c Skidding time (hour) 0.31c 0.228c Skidding distance (hm) 1.96c 1.61c Remarks: A = Suhartana et al. (2006); B = this study; C = Suhartana (2000); RIL = reduced impact logging; CLT = conventional logging technique. The high productivity could increase the timber utilization efficiency (TUE) presented in Table 4. Table 4 shows that implementation of RIL could increase the TUE. The TUE of RIL is higher than that of CLT of which for "A", the difference is 11%. The increase of TUE is followed by lower waste volume. This can be seen in "B" where RIL produced waste volume of about m3. Table 4 also shows that production cost of RIL is less than that of CLT. Table 4. Timber utilization efficiency (TUE) (%) and felling cost (Rp/m3). Study A B Aspect RIL CLT RIL CLT Efficiency (%) Stump height (cm) Waste volume (m3) Production cost (Rp/m3) Remarks: A = Suhartana et al. (2006); B = Suhartana & Yuniawati (2006); RIL = reduced impact logging; CLT = conventional logging technique. 39

6 DISCUSSION Felling and skidding operations will cause damage, even though it is done carefully. However, controlled felling and skidding according to RIL guidelines will minimize the damage. In RIL, the safety of fellers is given serious consideration. The felling direction is predetermined before field operation, taking into account tree architecture and characteristics. The length of back cuts of felled trees with diameter of less than 60 cm are 5-10 cm above the felling cut, while for diameter of more than 60 cm, the horizontal back cuts are cm above the felling cut (Anonymous 1993). Skidding, especially for road development, often damages trees which are mainly caused by tractor operations. Muhdi (2001) reported that tree damage caused by skidding rarely happens, since skidding roads are planned before development. However, if the skidding road is too curved until 90, the tractor manoeuvre will have to be extraordinary. Manan (1995) in Muhdi (2001) observed that lower ground exposure is directly related to lower tree damage. Ground exposure affects the susceptibility of soil to erosion due to the high rainfall in tropical areas. Based on Table 2, it can be said that implementation of felling and skidding using RIL could minimize ground exposure. Based on the study results, especially from residual stand damage, ground exposure and production cost, it is recommended that forest concession holders practise RIL. However, in actual fact forest concession holders have yet to apply RIL. It is assumed that RIL has not been fully understood by the companies or their operators. So, it is suggested that RIL training be provided to the operators. The government (Ministry of Forestry) should be strict in monitoring and evaluating the implementation of RIL. If both (companies and government) are committed to RIL, forest damage caused by logging could be minimized. CONCLUSION Although at present, CLT is more commonly practised, RIL does less damage to the forest. RIL also shows higher productivity, and low production cost. It is recommended that forest concession holders practise RIL in timber harvesting in order to sustain forest productivity. ACKNOWLEDGEMENTS We express gratitude to the Indonesian government for financial support. We would like to thank Dr Jeanine Pfeiffer and Dr Mochamad Indrawan for reviewing this manuscript. We also thank Dr Rufi'i, M.Z. Muttaqin and Harri Setjono for their support, especially in proof-reading. 40

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