Impacts of Land Use Changes on Carbon Stock in the Upper 200 cm Depth of Tropical Peats in West Kalimantan Province, Indonesia

Transcription

1 Impacts of Land Use Changes on Carbon Stock in the Upper 200 cm Depth of Tropical Peats in West Kalimantan Province, Indonesia Gusti Anshari 1, 2, Evi Gusmayanti 1,2, M. Nuriman 1, Tri. A. Putri 2, A. Elfiandi 2, and M. Yasir 2 [1] Centre for Wetlands People and Biodiversity (CWPB), Universitas Tanjungpura, Pontianak, West Kalimantan, Indonesia [2] Agroteknologi Department, Faculty of Agriculture, Universitas Tanjungpura, Pontianak, West Kalimantan, Indonesia This paper is presented on Workshop on Tropical Wetland Ecosystems of Indonesia: Science Need to Address Climate Change Adaptation and Mitigation. Sanur Beach Hotel, Bali, April Organized and Sponsored by CIFOR,USDA Forest Service, FORDA, and USAID

2 Errata (Table 1 in the Abstract) Errata (in red) Land Use Oil Palm < 5 Yr (OP < 5 Yr) Subsam ples (n) Peat layer (cm) ± 0.11 Corrected ± DBD LOI TOC TN ± ± ± ± ± ± 0.129

3 Introduction Our temporary knowledge and facts: Peats store lots of Carbon: Temperate Peats : 450 Gt (Gorham, 1991) Tropical Peats : Gt, with an average value of 88.6 Gt (Page et al. 2011) Indonesia has the largest tropical peats ( Km 2 ): Estimated Carbon stock : 55 ± 10 Gt (Jaenicke et al. 2008); 57 Gt; and an average 5.5. m peat depth (Page et al. 2011)

4 Introduction(cont.) Our major issues of concerns regarding Peat Carbon Stock Peat accumulation and decomposition occur at an extremely slow rate, These processes are dependent upon high rainfall, persistent inundation, and steady inputs of organic matters resulting from forest growths, tropical peats belong to most fragile ecosystems. The present land uses cause clearances of tropical peat forests and drawdown of water table depths. All forms of disturbances, i.e. logging, drainage and fires, threat the quality and stability of Carbon stock, and promote Carbon emissions to water and atmosphere

5 Research Aim We aim to assess differences in Total Organic Carbon (TOC), Dry Bulk Density (DBD), Loss on Ignition (LOI), C:N ratio, and Carbon Stocks (CS) in the upper 200 cm layers of several tropical peats which are currently different in land uses.

6 Method These consist of : - three oil palm plantation at different ages (i.e. less than 5 years old (OP < 5 Yr); 5-10 years old (OP 5-10 Yr), and more than 10 years old (OP > 10 Yr), - one plantation of exotic and fast growing timber species for pulp and paper industry (TP), - logged over peat forest (LOF), - coastal peat forest (SPF), and - inland peat forests (DSF). The research was conducted in West Kalimantan Province

7 Method (cont) Peat samples were collected with a Russian type peat auger (Eijkelkamp, Holland) Only in the upper part of 200 cm depth was analyzed for DBD, LOI, TOC, and TN at 50 cm increment A total of 254 samples were analyzed. Carbon stock (CS) is a product of DBD, TOC and peat depth. We calculated CS with this formula below (Pearson et al., 2007): CS=DBD x TOC x D x 100 Where: CS = Carbon Stock (t C Ha -1 ) DBD = Dry Bulk Density (g cm -3 ) TOC = Total Organic Carbon (%) D = Peat Depth (cm)

8 Results Gysnostoma Formation on Kerangas Peat Bazzania spp on the surface of inland peat forest

9 Peat Clearing Peat Fire (April 2011, Foto: AHA, Kompas)

10 Cummulative Carbon Stock

11 Low C:N Ratio in Oil Palm

12 Natural Variability of C:N ratio A lake in the middle of peat forest Coastal Peat Forest Inland Peat Forest Natural water channel

13 Anthropogenic Variability of C:N ratio

14 Discussions and Conclusions Land Use DBD LOI TOC TN Disturbed Oil Palm Forest Undisturbed SPF DSF

15 Discussions and Conclusions It is obvious that high DBD values in oil palms establish large CS, and high TOC values in DSF also determine high CS. However, CS values neither mean Carbon preservation nor accumulation. In addition to CS, we thought there is also important to analyse stability of Carbon stocks. A decline of C:N ratio may indicate some instability of Carbon stocks (Anshari et al., 2010), which would lead to Carbon source. In addition to N addition and decline of TOC resulting from drainage, it is also important to look at hydrological changes. Morris and Waddington (2011) argue that rapid turnover of pore water in peatland ecosystem supports high decay rates. I In a closed and undrained system, long residence time of pore water helps accumulations of by-products of peat decays, i.e. phenols and inorganic carbon, which play an important role in halting biological decomposition. In addition, organic matters have different physical and chemical properties which also determine both quality and stability of Carbon stock preservation.

16 Interlinked Factors Affect the Quality and Stability of Carbon Stock In addition to peat depth, bulk density and Carbon concentration, there is a need to look at the factors below: Climatic Factors: - Rainfall - Seasonal drought - Temperature Hydrological Factors: - water flow rate - water table depth - pore water residence time - nutrient contents in river water Ecosystem Characters: - peat age - peat type - litter input rates - peat decay rates - subsidence rate - Chemical and biological compositions - mineral substrate type Anthropogenic Disturbances: - Vegetation removals - Drainage - Peat Fire

17 Acknowledgements This research is funded by Kementerian Pendidikan National according to Contract No:437/SP2N/PP/DP2M/VI/2010 on 11 June 2010.We also thank you Fauna Flora International-Indonesia Program (FFI-IP) for assisting data collection from Sungai Putri and Danau Siawan Peat Forests. This presentation is supported by CIFOR