CC BY
57
DOI 10.18551/rjoas.2019-04.27
THE EFFECT OF MAIN CANALS ON CO2 EMISSIONS IN PALM OIL PLANTATIONS AT PEATLAND, CENTRAL KALIMANTAN OF INDONESIA
Darung Untung1, 2, Soemarno3, Dohong Salampak1, Prayogo Cahyo3
University of Palangka Raya & Postgraduate Program, Faculty of Agriculture, University of Brawijaya Faculty of Agriculture, University of Brawijaya, Malang, Indonesia
*E-mail: untdar@yahoo.com
ABSTRACT
The making of main canals in oil palm plantation areas, especially on peatlands, will affect changes in the physical, chemical and biological properties of peatlands, will affect the process of oxidation and reduction of peatland which affects the regulation of changes in gas emissions, especially the concentration of gases such as: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4). The research objective was to determine the effect of the making of main canals on the rate of CO2 emissions from peat soil surface for each difference in the measurement distance from the drainage channel (25, 50 and 100) m in the block of oil palm plant age (3, 4, 5 and 6) years after planting. The average rate of emissions in Palm Oil Plants Age 3 Years after Planting at a distance of 25 m equal to 147.87 mg C m2 Hour1 , the distance of 50 m is 156.17 mg C m2 Hour1 and a distance of 100 m amounted to 148.01 mg C m2 Hour1, Palm Oil Plants Age 4 Years after Planting at a distance of 25 m equal to 247.10 mg C m2 Hour1 , the distance of 50 m is 248.90 mg C m2 Hour1 and a distance of 100 m amounted to 257.10 mg C m2 Hour1, Palm Oil Plants Age 5 Years after Planting at a distance of 25 m equal to 147, 87 mg C m2 Hour1 , the distance of 50 m is 156, 17 mg C m2 Hour1 and a distance of 100 m amounted to 148, 01mg C m2 Hour1. Palm Oil Plants Age 6 Years after Planting at a distance of 25 m equal to 329, 95 mg C m2 Hour1 , the distance of 50 m is 335, 08 mg C m2 Hour1 and a distance of 100 m amounted to 347, 22 mg C m2 Hour1. The effect of distance from canal main on CO2 emissions does not significantly affect changes in CO2 emissions in the block of oil palm plant age (3, 4, 5 and 6) years after planting, but the farther away from main canals, CO2 emissions are increasing.
KEY WORDS
Peatlands, canals, CO2 emissions, palm oil.
The current environmental problem that becomes the concern to the international community is the phenomenon of climate change, namely the changing physical conditions of the Earth's atmosphere among other temperature and rainfall distribution, which have a wide impact on various sectors of human life. Global climate change occurs because of an increase in gas concentration such as: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and hydrocarbons such as (CFCs) in the atmosphere of the earth, which is called the greenhouse effect or greenhouse gases (Batjes and Bridges, 1992).
Along with the issue of global climate change on earth caused by increasing concentrations of greenhouse gases, one of which occurs due to unwise use of forests and peatlands, causing organic matter in peat to decompose aerobically or anaerobically, so the three gases above potentially release into the atmosphere (Jauhiainen et al, 2005). Hooijer et al, (2010) say decomposition on damaged peatlands in Indonesia is estimated to emit CO2 emissions of 632 Mton/year (range 355-874 Mton/year) and are likely to increase every year, unless peatland use practices change.
According to Page et al, (2008), tropical peat swamp forest ecosystem is the most efficient place to capture and store carbon (C) reserves, because in this ecosystem carbon is stored in the body of plants that are still alive (biomass) and on dead body parts of plants, whether they are still standing or fallen, including fallen branches and leaves.
The ecological function of tropical peatlands is as a storehouse of carbon, carbon balance, sediment retention, nutrient detention, and micro-climate stability (Maltby, 1997; Rieley et al, 2008). Peatlands are a place for carbon accumulation (carbon reservoir or carbon storage). The release of CO2 into the air from reclaimed natural peatlands for agricultural activities is a process of oxidation and reduction of organic matter. In a reductive environment, the rate of decomposition of peat is very slow and many toxic organic acids and methane (CH4) are produced, whereas in the oxidative state the release of C is increased more especially in the form of CO2. The type of land use affects the ability of soil to store CO2. This type of land use plays a very important role in controlling CO2 flux in the atmosphere (Jauhiainen et al, 2005).
The opening of peat swamp land for agriculture and plantations is always followed by the making of deep and wide main (canals), which will cause damage to the hydrological system due to oxidation of organic matter and subsidence of the peat surface (Wosten et al, 1997, Furukawa et al, 2005), further in the area where the tropical peat area has been drained it will cause sudden and permanent changes to the carbon ecosystem balance (Page et al. 2002, Canadell et al, 2007, Hirano et al, 2007).
The making of main canals in oil palm plantation areas, especially on peatlands, will affect the high-low level of the groundwater, The high and low of groundwater level will affect the oxidation and reduction process on peat so it affects the regulation of CO2 gas emissions.
The aim of the study was to determine the effect of the making of main canals on the rate of CO2 emissions from peat soil surface for each difference in measurement distance from the drainage channel (25, 50 and 100) m.
MATERIALS AND METHOD OF RESEARCH
This research was carried out in oil palm plantation companies on peat land, Kota Besi sub-district, East Kotawaringin Regency, Central Kalimantan Province, Indonesia, which was held from November 2016 to October 2017. Field surveys at company sites on the plots of oil palm plants with 3 years of planting age (S:02° 26' 20.45", E:112° 54' 03.70" ) , oil palm plants 4 years planting age (S:02° 24' 07.76" , E:112° 59' 43.47"), oil palm plants with 5 years planting age (S:02° 26' 14.76" , E:112° 54' 08.72"), and oil palm plants with 6 years planting age (S:02° 26' 22.11" , E:112° 54' 05.23"). Measurement of CO2 emissions for each oil palm plot from the main canals edge (25, 50 and 100) m, (Figure 1).
t t < - Slope direction —> t _i I_i_I I—
Average distance ->
->100 m
-> 50 m
^ 25 m
Sub-transect
6
BLOCK 1
CT: O O
3
BLOCK 3
•e aoo
i i
Transect
BLOCK 2
Field drains
BLOCK4
—i i-
Canal ! ! system
Figure 1 - Outline of CO2 emission monitoring location at average distance in the block of oil palm
plant age (3, 4, 5 and 6) years after planting
Measurement of CO2 emissions using the open closed chamber method for each research plot. Open closed chamber method with three replications. Gas fluxes were measured monthly from January 2017 to December 2017. Methods of sample retrieval and analysis of CO2 gas using the method by Takakai et al, (2006), Nakano et al, (2004), Toma and Hatano(2007), and Toma et al, (2011). Method of Chamber oven and close measurement of CO2 gas emissions. The laboratory using CO2 emission measuring devices (infrared CO2 analyzer Fuji type ZFP9GC11).
Tedlar bag
50 mL Syringe
Sampling pipe 2nd Tedlar bag
Pressure compensation bag
Figure 2 - Method of Chamber oven and close (Toma and Hatano, 2007)
Statistical analysis using a randomized block design with 3 replications, and 4 treatments namely the use of conservation forest land, grass land and oil palm plants with planting age (3, 4, 5 and 6 years). Analysis data was conducted using Genstat 18 Statistic program and Microsoft Office Excel program 2010.
RESULTS OF STUDY
The results of the effect of differences in the distance of measurement from the edge of the drainage channel to the average CO2 emissions in the block of oil palm plant age (3, 4.5 and 6) years after planting, are shown in Figures below.
Figure 3 shows the average emission rate at a distance of 25 m equal to 147.87 mg C m2 Hour1 , the distance of 50 m is 156.17 mg C m2 Hour1 and a distance of 100 m amounted to 148.01 mg C m2 Hour1 in Plots Location of Palm Oil Plant Age 3 Years after Planting.
Dec Nov Oct Sept Aug July June May April March Feb Jan
75 m 50 m 25 m
50 100 150
CO2 (mg C m2 Jam1 )
200
0
Figure 3 - The pattern of CO2 emissions at a distance of 25, 50 and 100 m in the Plots Location
of Palm Oil Plant Age 3 years after planting
Nov Sept July May March Jan
75 m 50 m 25 m
50 100 150 200 250 CO2 (mg C m2 Jam1)
300
350
Figure 4 - The pattern of CO2 emissions at a distance of 25, 50 and 100 m in the Plots Location
of Palm Oil Plant Age 4 years after planting
Figure 4 shows the average emission rate at a distance of 25 m at 247.10 mg C m2 Hour1 , the distance of 50 m is 248.90 mg C m2 Hour1 and a distance of 100 m amounted to 257.10 mg C m2 Hour1 in Plots Location of Palm Oil Plant Age 4 Years after Planting.
Nov Sept July May March Jan
75 m 50 m 25 m
0,00 100,00 200,00 300,00
CO2 (mg C m2 Jam1)
400,00
Figure 5 - The pattern of CO2 emissions at a distance of 25, 50 and 100 m in the Plots Location
of Palm Oil Plant Age 5 years after planting
Figure 5, Shows the average emission rate at a distance of 25 m equal to 147, 87 mg C m2 Hour1 , the distance of 50 m is 156, 17 mg C m2 Hour1 and a distance of 100 m amounted to 148, 01mg C m2 Hour1 in Plots Location of Palm Oil Plant Age 5 Years after Planting.
Nov Sept July May March Jan
75 m 50 m 25 m
0,00 100,00 200,00 300,00
CO2 (mg C m2 Jam1)
400,00
0
Figure 6 - The pattern of CO2 emissions at a distance of 25, 50 and 100 m in the Plots Location
of Palm Oil Plant Age 6 years after planting Figure 6 shows the average emission rate at a distance of 25 m equal to 329, 95 mg C m2 Hour1 , the distance of 50 m is 335, 08 mg C m2 Hour1 and a distance of 100 m amounted to 347, 22 mg C m2 Hour1 in Plots Location of Palm Oil Plant Age 6 Years after Planting. The results of the variance analysis showed that there was no interaction of treatment on the CO2 emissions at the error level of 5% (P>0.05), but there is a major influence, namely, the age of oil palm plants is significantly different on the CO2 emissions, but the effect of the distance of measurement from the drainage channel is not significantly different on the CO2 emissions shown in Appendix Table 8. Effect of Palm Oil Plant Age and Distance on the Average of CO2 Emissions can be seen in Table 1.
Table 1 - Effect of Palm Oil Plant Age and Distance on the Average of CO2 Emissions
Treatment CO2( mg C m2 Hour1 )
3 years palm oil plant 150.7 a
4 years palm oil plant 251.0 b
5 years palm oil plant 307.8 c
6 years palm oil plant 337.4 d
Distance from canal main
25 meter 259.7 a
50 meter 260.9 a
100 meter 264.7 a
Note: Numbers accompanied by the same letter on the same row and column are not significantly different from Duncan's test 5%.
Table 1, shows that the average of CO2 emissions according to the age of oil palm plants and the distance of measurement from the edge of the drainage canal on the 6 years oil palm plants is higher and significantly different from the age of other oil palm plants with an average of CO2 emission equal to 337.4 mg C m2 Hour1 while the lowest average of CO2 was found in the age of 3 years of oil palm plants amounted to 150.7 mg C m2 Hour1.
The average of CO2 emissions based on distance indicate a distance of 100 m with the higher average of CO2 namely 264, 7 150, 7 mg C m2 Hour1 but not significantly different from the distance of 25 m and 50 m. Variations in the value of CO2 emissions according to distance indicate that the farther away from the canal channel, the CO2 increases.
DISCUSSION OF RESULTS
The difference in the average pattern of CO2 emissions in the area of oil palm plantations is thought to be influenced by changes in environmental factors due to the conversion of peatlands into oil palm plantations. Some researchers say that the factors that affect the high and low average of CO2 emissions that released to the atmosphere are environmental factors, especially groundwater, soil temperature and soil moisture, This is in accordance, that the average value of CO2 emissions released by peatlands is influenced by environmental factors, including groundwater depth, air temperature, soil temperature, peat properties such as peat pH, CEC, C-organic content and microorganisms. Vegetation type (land cover / canopy) will affect the average temperature under the canopy which will automatically affect cO2 emissions in different vegetation types.
Darung et al. (2018), Changing of the land use conversion of tropical peat land for oil palm plantation activities plays a very important role in the pattern of changes in the rate of emissions from the surface of peatlands, controlling the rate of CO2 emissions in the atmosphere, means controlling global warming. Changes in peat land use in oil palm plantations, the findings obtained the rate of CO2 emissions vary widely depending on changes in vegetation types.
Based on the results of the analysis of variance, there is a major influence, namely, the age of oil palm plants is significantly different on the CO2 emissions, but the influence of the
measurement distance from the drainage channel is not significantly different on the CO2 emissions. The average of CO2 emissions according to the age of oil palm plants and the measurement distance from the edge of the drainage canal in 6 years oil palm plants is higher and significantly different from the age of other oil palm plants. The average of CO2 emission in 6 years palm oil plants is 337.4 m C m2 Hour1 then a 5 years oil palm plant equal to 307.8 mg C m2 Hour1, 4 years oil palm plantations amounting to 251.0 mg C m2 Hour1, The lowest oil palm plants found at the age of 3 years for oil palm plants equal to 150, 7 mg C m2 Hour1, while the average of CO2 emissions based on distance show a distance of 100 m with the higher average CO2 namely 264, 7 150, 7 mg C m2 Hour1 but not significantly different from the distance of 25 m and 50 m. Variation in the value of CO2 emissions according to the distance measurement of CO2 emissions shows that the farther away from the canal channel then CO2 increases to a distance of 100 m from the drainage channel.
The results of measurements on CO2 emissions released in the area of oil palm plantations on peatlands show that there are differences where the older the plant ages, the greater the CO2 emissions released into the atmosphere. According to Melling et al.(2005), that the differences in the age of oil palm plants have an important role in the value of CO2 emissions on peatlands. Mature oil palm plants have more plant roots (rhizosphere) compared to young plants and simultaneously that the microbial community of the rhizosphere region is higher than non rhizosphere so that in addition to plant root respiration, microbial activity is possible to contribute a number of emissions around plant roots so that the CO2 emissions produced are also higher.
The part of the plant that has the most role in the respiration of plant roots is the root area. The root area as the rhizosphere is a place where concentrated root hairs which play a role in plant root respiration. In oil palm plants with the age of 6 years have more rhizosphere compared to the age of 3 years. The process of root respiration of oil palm plants is the second largest emitter after the process of decomposition by microbes on peatlands (Melling et al.2005).
This is in line with the opinion from Ekberg et al.(2007), that the process of respiration produced by plants is one of the contributors to carbon emissions in oil palm agroecosystem land. Soil respiration is a joint process between autotrophic respiration (root respiration) and heterotrophic respiration (peat decomposition), root respiration activity; is one component that plays an important role in determining the value of CO 2 emissions released into the atmosphere (Tian et al. 2010).
Main canals in oil palm agroecosystems are one of the important factors in the process of carbon emissions. The research results showed variations in the value of CO2 emissions according to the distance of measurements from the drainage channel. At a distance of 25 m from the drainage channel the CO2 emissions equal to 259.7 mg C m2 Hour1 at groundwater level of 33.24 cm, measurement distance of 50 m from the drainage channel the CO2 emissions equal to 260.9 mg C m2 Hour1 at groundwater level of 34.58 cm, and the measurement distance of 100 m from drainage channel the CO2 emission equal to 264.7 mg C m2 Hour1 at groundwater level of 35.42 cm, this shows that the farther away from the canal channel, then the average of CO2 emission increases, as well as the groundwater level, gets deeper to 100 m distance.
This is thought that the further away from the drainage channel there is a decrease in groundwater level causing changes in anaerobic conditions to be aerobic in the layer above the groundwater level thereby increasing O2 availability and can accelerate the process of reforming organic matter further, it will further spur C-organic mineralization to produce CO2 gas, so that CO2 emissions increase the further from the edge of the drainage channel.
According to Hooijer et al. (2009 and 2012), fluctuations in the depth of peat soil water have a positive relationship to changes in the value of CO2 emissions in the rhizosphere and non rhizosphere, n line with the findings of Hirano et al. (2014) that there is a significant relationship between groundwater level and soil CO2 emissions on tropical peatland in Palangkaraya, Central Kalimantan.
Jauhiainen et al, (2012) said that if groundwater is close to the surface for a long time then heterotropic carbon emissions will occur so rapidly along with changes in groundwater
depth, at this time there will also be a non-linear relationship between groundwater and humidity. Hirano et al, (2012) also said that the increase in carbon flow or decomposition of oxidative peat in low groundwater conditions was due to thickening of the unsaturated soil zone and the result of increased aeration.
Research by Hirano et al. (2012) suggests that the relationship of groundwater and carbon flow is a linear relationship. Jauhiainen, et al, (2012) also said, when measuring the relationship between CO2 emissions and the depth of groundwater, it must be remembered that the depth of groundwater does not control the oxidation of peat. Conversely, it is used to measure moisture from peatland above groundwater, which has a direct effect on peat oxidation by affecting the availability of oxygen in porous space. Also added that on peatlands which have high groundwater depth and no good drainage control, had a strong relationship with soil moisture.
CONCLUSION
Effect of distance from canal main on CO2 emissions does not significantly affect changes in CO2 emissions in the blocks of oil palm plant age (3, 4, 5 and 6) years after planting, but the farther away from canal main CO2 emissions are increasing
ACKNOWLEDGEMENTS
Thank you to Professor Ryusuke Hatano (Hokkudai-Japan University), and Mr. Teguh Patriawan as President Director of the Palm Oil Plantation Company PT.Nusantara Sawit Perdana and also colleagues staff at Center for International Cooperation in Sustainable Management of Tropical Peatland (CIMTROP) Palangka Raya University for cooperation and assistance during research activities on CO2 emissions from changes in convertion land use in oil palm plantations running well.
REFERENCES
1. Batjes, N. H, & Bridges, E. M. (1992). A review of soil factors and processes that control fluxes of heat, moisture and greenhouse gases. International Soil Reference and Information Centre.
2. Canadell, . J.D.E. Pataki, R. Gifford, R.A. Houghton, Y.Luo, M.R. Raupach, P. Smith, and W. Steffen. 2007. Saturation of terrestrial carbon sink. Dalam: Cannadel, J.G, D.E.Patak, and L, Pitelka (eds) Terrestrial Ecosystems in a Changing World, Sringer Verlag, Berlin. 59-78.
3. Darung, U, Soemarno, Dohong, S, & Prayogo, C. (2018). Controlling factor of carbon dioxide flux from tropical peat soil in palm oil at central Kalimantan, Indonesia. Bioscience Research, 15(4), 3809-3820.
4. Furukawa Y, Inubushi K, Ali M, Itang AM, Tsuruta H. (2005): Effect of changing groundwater levels caused by land-use changes on greenhouse gas fluxes from tropical peat lands. Nutrient Cycling in Agroecosystems, 71, 81-91.
5. Hirano T, Segah H, Harada T, Limin S, June T, Hirata R, Osaki M .(2007): Carbon dioxide balance of a tropical peat swamp forest in Kalimantan, Indonesia. Glob. Change Biol, 13, 412-425.
6. Hirano T, Segah H, Limin S, June T, Tuah SJ, Kusin K, Hirata R, Osaki M. (2005): Energy balance of a tropical peat swamp forest in Central Kalimantan, Indonesia. Phyton, 45, 67-71.
7. Hirano, T, Kusin K, Limin S, Osaki M. (2012). Carbon dioxide emissions through oxidative peat decomposition on a burnt tropical peatland. Global Change Biology: 130 - 121.
8. Hirano, T, J. Jauhiainen, T. Inoue, H. Takahashi. (2009). Controls on carbon balance of tropical peatlans. Ecosystem 12: 873 - 887.
9. Hooijer A, Page S, Canadell JG, Silvius M, Kwadijk J, Wösten H, Jauhiainen J. (2010): Current and future CO2 emissions from drained peatlands in Southeastern Asia. Biosciences, 7, 1505-1514.
10. Hooijer A, Page SE, Jauhiainen J, Lee WA, Idris A, Anshari G, (2012): Subsidence and carcon loss in Hooijer A, Page S, Canadell JG, Silvius M, Kwadijk J, Wosten H, Jauhiainen J 2010: Current and future CO2 emissions from drained peatlands in Southeastern Asia. Biosciences, 7, 1505-1514.
11. Hooijer, A, M. Silvius, H. Wosten, and S. Page.(2006). PEATCO2, Assessment of CO2 emissions from drained peatlands in SE Asia. Report Q3943. Delft Hydraulics, Delft, The Netherlands.
12. Jauhiainen J, Hooijer A, Page SE. (2012): Carbon dioxide emissions from Acacia plantation on peatland in Sumatra, Indonesia. Biogeosciences, 9, 617-630.
13. Jauhiainen J, Limin S, Silvennoinen H, Vasander H. (2008): Carbon dioxide and methane fluxes in drained tropical peat before and after hydrological restoration. Ecology, 89, 3503-3514.
14. Jauhiainen J, Silvennoinen H, Hämäläinen R, Kusin K, Limin S, Raison RJ, Vasander H. (2012a). Nitrous oxide fluxes from tropical peat with different disturbance history and management. Biogeosciences, 9, 1337-1350.
15. Jauhiainen J, Vasander H, Rieley J, Page SE. (2010): Tropical Peat Carbon Gas Interaction: Technical report 2. Leicester, United Kingdom: University of Leicester.
16. Jauhiainen, J, H.Takahashi, J.E.P. Heikkinen, P.J.Martikainen, and H. Vasander. (2005). Carbon fluxes from a tropical peat swamp forest floor. Global Change Biology. 11:17881797.
17. Jauhiainen, J, Heikkinen, J, Martikainen, P.J. and Vasander, H. (2001. CO2 and CH4 fluxes in pristine peat swamp forest and peatland converted to agriculture in Central Kalimantan, Indonesia. International Peat Journal. 11: Hal: 43-50.
18. Jauhiainen, J, Takahashi, H, Heikkinen, J. E, Martikainen, P. J, & Vasander, H. (2005). Carbon fluxes from a tropical peat swamp forest floor. Global Change Biology, 11(10), 1788-1797.
19. Jauhiainen, J, Vasander, H, Jaya, A, Takashi, I, Heikkinen, J, Martikinen, (2004). Carbon balance in managed tropical peat in Central Kalimantan, Indonesia. In WiseUse of Peatlands - Proceedings of the 12th International Peat Congress, 06.11.06.2004, Tampere, volume 1, Päivänen, J. (ed.), International Peat Society, Jyväskylä, pp. 653659.
20. Maltby, E. (1997). Developing guidelines for the integrated management and sustainable utilisation of tropical lowland peatlands. in: Rieley, J.Oand S.E.Page.(eds.), Biodiversityand Sustainability of TropicalPeatland.Proceeding of the International Symposium on TropicalPeatlands. Palangka Raya, Indonesia. Samara Publisher, Cardigan, UK. 9-18.
21. Melling L, Hatano R, Goh KJ (2005): Soil CO2 flux from three ecosystems in tropical peatland of Sarawak, Malaysia, Tellus, 57B, 1-11.
22. Nakano T, Sawamoto T, Morishita T, Inoue G, Hatano R. (2004): A comparison of regression methods for estimating soil-atmosphere diffusion gas fluxes by a closed-chamber technique. Soil Biol. Biochem, 36, 107-113.
23. Page SE, Slegert F, Rieley JO, Boehm HDV, Zaya A, Limin S. (2002): The amount of carbon released from peat and forest fires in Indonesia during 1997. Nature, 420, 61-65.
24. Page, S. E, Rieley, J.O, Doody, K, Jenkins, P, Monrogh, H, Bernand-Otway, S. and Wilshwa, S. (1997). Biodiversity of peat swamp forest: A case study of animal diversity in the sungai Sebangau Catchments of Central Kalimantan, Indonesia. Dalam: Tropical Peatland. Editor: Rieley. J.O. and Page, S.E. Samara Publishing Limited, Cardigan. Hal: 231-242.
25. Page, S.E, Hoscilo, A, Wösten, H, Jauhiainen, J.Silvius, M, Rieley, J, Ritzema, H, Tansey, K, Graham, L, Vasander, H, and Limin, S, (2009). Restoration Ecology of Lowland Tropical Peatlands in Southeast Asia: Current Knowledge and Future Research Directions.Ecosystems, 12:888-905.
26. Page, S.E, J.O. Rieley, R, Wust. (2006). Lowland tropical peatland of Southeast Asia. Dalam: Martini, L.P, A.M. Cortizas, and W. Chesworth (eds.) Peatland: Evolution and Records of Environmental and Climate Changes. Elsevier. Amsterdam-Boston-Heidelberg-London-New York-Paris-San Diego-SanFrancisco-Singapore-Sydney-Tokyo. 145-172.
27. Rieley, J.O, and Page, S.E, (2008). Carbon Budget under Different Land Uses on Tropical Peatland, dalam Future of Tropical Peatlands in Southeast Asia as Carbon Pools and Sinks. Rieley, J.O, Banks, C.J, and Page, S.E. (eds.).
28. Takakai F, Morishita T, Hashidoko Y, Darung U, Kuramochi K, Dohong S, Limin SH, Hatano R. (2006): Effects of agricultural land-use change and forest fire on N2O emission from tropical peatlands, Central Kalimantan, Indonesia. Soil Sci. Plant Nutr, 52, 662-674.
29. Tian, D, G.Wang, Y.Peng, W.Yan, X. Fang, F.Zhu, and X.Chen. (2011). Contribution of autotrophic and heterotrophic respiration to Soil CO2 effluxin Chinese fir plantations. Australian Journal of Botany. 59: 26-31.
30. Toma Y, Hatano R 2007: Effect of crop residue C:N ratio on N2O emissions from Gray Lowland soil in Mikasa, Hokkaido, Japan. Soil Sci. Plant Nutr, 53, 198-205.
31. Toma Y, Kimura SD, Yamada H, Hirose Y, Fujiwara K, Kusa K, Hatano R. (2010): Effects of environmental factors on temporal variation in annual carbon dioxide and nitrous oxide emissions from an unfertilized bare field on Gray Lowland soil in Mikasa, Hokkaido, Japan. Soil Sci. Plant Nutr, 56, 663-675.
32. Toma Y, Takakai F, Darung U, Kuramochi K, Limin SH, Dohong S, Hatano R. (2011): Nitrous oxide emission derived from soil organic matter decomposition from tropical agricultural peat soil in central Kalimantan, Indonesia. Soil Sci. Plant Nutr, 57, 436-451.
33. Wahyunto, A. Dariah, and F. Ags. (2010). Distribution, properties, and carbon stock of Indonesia peatland. Dalam: Proceeding of International Workshop on Evaluation and sustainable Management og soil Carbon sequestration in Asian Countries. Bogor-Indonesia. September 28 - 29, 2010.
34. Wosten, J. H. M, A. B. Ismail, and A. L. M. van Wijk. (1997). Peat subsidence and its practical implications: a case study in Malaysia. Geoderma 78:25-36.
35. Wösten, J.H.M, Clyman, S.E, Page, S.E, Rieley, J.O. and Limin S.H, (2008). Peat-Water Interrelation in Tropical Peatland Ecosystem in Southeast Asia. Catena, 73:201-217.
