Carbon Emissions From Oil Palm Plantations on Peat Soil

Abstract

Southeast Asian peatlands have undergone recent land use change with an increase in industrial agricultural plantations, including oil palm. Cultivating peatlands requires creating drainage ditches and other surface microforms (i.e., harvest paths, frond piles, cover plants, and next to the palm). However, it is currently unclear how these management actions affect rates of carbon losses from the peat. Here we report carbon fluxes from each of the different surface microforms measured monthly (soil CO 2 [total soil respiration-R tot ] and stem CH 4) and bimonthly (soil CH 4 , drain CO 2 and drain CH 4). We calculated annual carbon fluxes and partitioned heterotrophic (R h) and root-rhizosphere respiration by sampling rhizosphere and root-free soil. Linear mixed effect models were used to determine which environmental factors best-predicted carbon fluxes, and to develop recommendations for management solutions that could reduce carbon losses. Carbon fluxes varied significantly between the different microforms; the greatest CO 2 fluxes were measured next to the palm and the greatest CH 4 fluxes were measured from the drainage ditches. Annual estimates of R tot , R h and drain CO 2 were 22.08 ± 0.50, 17.75 ± 1.54, and 1.5 ± 0.10 Mg CO 2-C ha −1 yr −1 , respectively. R h varied between the two plantations: Sebungan averaged 11.43 ± 1.37 Mg CO 2-C ha −1 yr −1 and Sabaju averaged 24.08 ± 1.42 Mg CO 2-C ha −1 yr −1. Net ecosystem CH 4 fluxes averaged 61.02 ± 17.78 kg CH 4-C ha −1 yr −1-similar to unmanaged swamp forests. The two plantations did not vary in overall CH 4 flux, but did vary in transport pathway. CH 4 fluxes from the soil, drains and stems followed a ratio of 50:50:0 from Sabaju (water table depth [WTD]: −0.49 ± 0.004 m) and 11:98:0 from Sebungan (WTD: −0.77 ± 0.007 m). R h dominated the peat carbon losses. WTD controlled variation in R h from Sebungan where the WTD was deeper. Air and soil temperature controlled variation in Sabaju, with greater fluxes from the harvest path, attributed to the absence of shade. These results suggest that shading the soil (e.g., through addition of frond piles) and raising the water table may be the most effective ways to reduce peat carbon loss from drained peat soils.

Impact of forest plantation on methane emissions from tropical peatland

“…However, our measurements over the Acacia plantation do not show a diurnal variation in NEE‐CH 4 , and this may confirm that the root system remained above the GWL. Finally, it is likely that a substantial fraction of CH 4 emission from the Acacia plantation area could be occurring from the open water surface of the ditch and canal network (Evans, Renou‐Wilson, & Strack, ; Jauhiainen & Silvennoinen, ; Manning et al, ), and therefore subject to different environmental controls (Deshmukh et al, ). The CH 4 uptake rates in the Acacia plantation are similar to those previously reported over tropical peatlands during the dry season (Sakabe et al, ).…”

“…Thus, GWL seems to be the key indirect control on CH 4 emissions via diffusion from soil surfaces (Winton, Flanagan, & Richardson, ). Overall, the lack of a difference between nighttime NEE‐CH 4 over the natural forest and the Acacia plantation can be attributed to the high GWL at the natural forest and to the potential presence of emissions from the water surfaces of ditches and canals in the Acacia plantation (Jauhiainen & Silvennoinen, ; Manning, Kho, Hill, Cornulier, & Teh, ). In addition, the higher soil temperature at the Acacia plantation might have increased CH 4 production (Sjögersten et al, ), while the higher peat bulk density and the absence of a hollow‐hummock microtopography at the Acacia plantation might have lowered CH 4 oxidation by increasing soil moisture content and lowering oxygen diffusion in the peat (Estop‐Aragones, Knorr, & Blodau, ).…”

Is Intercropping an Environmentally-Wise Alternative to Established Oil Palm Monoculture in Tropical Peatlands?

“…However, CH 4 emissions in intercropping sites are still lower than 2 mg m −2 hr −1 fluxes observed in primary peat swamp forest in Peninsular Malaysia (Dhandapani et al, 2019c). Considering these agricultural peatlands are drained, with oil palm monocropping having more severe drainage, there is a potential for greater methane emissions from drainage canals (Manning et al, 2019).…”

Effects of Understory Vegetation Management on Plant Communities in Oil Palm Plantations in Sumatra, Indonesia

“…Plantation establishment exposes soil and can make it vulnerable to compaction, erosion, and leaching (as described for land immediately after logging, in Clarke and Walsh, 2006). In peat soils there are also high levels of subsidence and peat oxidation when soils are exposed (Hooijer et al, 2012;Manning et al, 2019). In addition, chemical fertilisers and pesticides are frequently applied during the cultivation process (Corley and Tinker, 2003a).…”