Effect of changing groundwater levels caused by land-use changes on greenhouse gas fluxes from tropical peat lands

Abstract

Monthly measurements of carbon dioxide ͑CO 2 ͒, methane ͑CH 4 ͒ and nitrous oxide ͑N 2 O͒ fluxes in peat soils were carried out and compared with groundwater level over a year at four sites ͑drained forest, upland cassava, upland and lowland paddy fields͒ located in Jambi province, Indonesia. Fluxes from swamp forest soils were also measured once per year as the native state of this investigated area. Land-use change from drained forest to lowland paddy field significantly decreased the CO 2 ͑from 266 to 30 mg C m -2 h -1 ͒ and N 2 O fluxes ͑from 25.4 to 3.8 g N m -2 h -1 ͒, but increased the CH 4 flux ͑from 0.1 to 4.2 mg C m -2 h -1 ͒ in the soils. Change from drained forest to cassava field significantly increased N 2 O flux ͑from 25.4 to 62.2 g N m -2 h -1 ͒, but had no significant influence on CO 2 ͑from 266 to 200 mg C m -2 h -1 ͒ and CH 4 fluxes ͑from 0.1 to 0.3 mg C m -2 h -1 ͒ in the soils. Averaged CO 2 fluxes in the swamp forests ͑94 mg C m -2 h -1 ͒ were estimated to be one-third of that in the drained forest. Groundwater levels of drained forest and upland crop fields had been lowered by drainage ditches while swamp forest and lowland paddy field were flooded, although groundwater levels were also affected by precipitation. Groundwater levels were negatively related to CO 2 flux but positively related to CH 4 flux at all investigation sites. The peak of the N 2 O flux was observed at Ϫ 20 cm of groundwater level. Lowering the groundwater level by 10 cm from the soil surface resulted in a 50% increase in CO 2 emission ͑from 109.1 to 162.4 mg C m -2 h -1 ͒ and a 25% decrease in CH 4 emission ͑from 0.440 to 0.325 mg C m -2 h -1 ͒ in this study. These results suggest that lowering of groundwater level by the drainage ditches in the peat lands contributes to global warming and devastation of fields. Swamp forest was probably the best land-use management in peat lands to suppress the carbon loss and greenhouse gas emission. Lowland paddy field was a better agricultural system in the peat lands in terms of C sequestration and greenhouse gas emission. Carbon loss from lowland paddy field was one-eighth of that of the other upland crop systems, although the Global Warming Potential was almost the same level as that of the other upland crop systems because of CH 4 emission through rice plants.

Biogeochemical processes along a nutrient gradient in a tropical ombrotrophic peatland

“…Methane fluxes measured here were several orders of magnitude lower than CO 2 fluxes and varied markedly among sites. The highest CH 4 fluxes from site 1 (R. taedigera) and site 5 (sawgrass swamp) are comparable to fluxes reported in the literature from Kalimantan(e.g., 0.35-2 mg CH 4 m -2 h 1 ; Furukawa et al 2005;Hadi et al 2005;Jauhiainen et al 2005), while the lowest CH 4 fluxes at the three intermediate sites in the current study (C. panamensis and mixed forest) are comparable to those reported for Sarawak wetlands (maximum rates of 11.2 lg CO 2 m -2 h -1 ; Melling et al 2005a, b). Our results suggest that CH 4 fluxes have high spatial variability in peatland systems and vary in response to differences in the water table Hadi et al 2005;Jauhiainen et al 2005) and substrate availability (Bachoon and Jones 1992) to a greater extent than CO 2 fluxes.…”

Methane fluxes from waterlogged and drained Histosols of highland areas

“…In general, the results of CH 4 emission reduction followed by methane consumption fully agree with those of other studies that evaluated the effect of lowering the water-table level by draining in flooded soils in several parts of the world Nykanen et al, 1995;Maljanen et al, 2004;von Arnold et al, 2005;Furukawa et al, 2005;Bridgham et al, 2006;Elder & Lal, 2008;Jauhiainen et al, 2008;Jiang et al, 2009;Huang et al, 2010;Page & Dalal, 2011). All these authors showed that small water-table decreases cause drastic reductions in methane emissions, demonstrating the strong effect of drainage on CH 4 fluxes.…”

“…Some studies report positive effects of both temperature and pluvial precipitation (Jiang et al, 2009), others only of precipitation but not of temperature (Inubushi et al, 2003;Furukawa et al, 2005) In paddy rice fields, emissions reached 489 kg ha -1 yr -1 CH 4 in a Histosol in Indonesia and 586 kg ha -1 yr -1 CH 4 in a Planosol (Sousa, 2013) and 623 kg ha -1 yr -1 CH 4 in a Gleysol, the latter two in Rio Grande do Sul, Brazil (Zschornack, 2011). These values indicate that methane emission is much higher from paddy rice soils than from the natural Histosol in this study.…”

“…Huang et al (2010) estimated that soils of wetlands converted to cropland between 1950 and 2000 lost about 50 % C. Other authors also reported an increase in CO 2 emissions from Histosols (Lohila et al, 2003;Maljanen et al, 2002Maljanen et al, , 2004von Arnold et al, 2005;Furukawa et al, 2005;Yamulki et al, 2012), and Joosten & Couwenberg (2008) In view of the functions Histosols fulfill in the ecosystem, they should be preserved and not drained. Strategies for mitigating CH 4 emissions should be concentrated on the modification of human activities and on no account on interventions in the areas of occurrence of Histosols.…”

“…Methane production reaches a maximum near 20 cm below the water-table, while oxidation occurs to a depth of 10 cm (Kettunen et al, 1999). However, CH 4 emissions decrease logarithmically with the lowering of the water-table (Moore & Dalva, 1993;Furukawa et al, 2005), which can occur with drainage. On the other hand, the drainage of these soils may affect its capability of fixing C and storing water.…”