Factors influencing methane emission from peat soils: Comparison of tropical and temperate wetlands

Methane (CH4) emissions from peat soils in tropical and temperate wetlands were compared. Annual CH4 emission rates in Ozegahara, the largest wetland on Honshu main island, Japan, were higher than in drained forest wetland areas examined in Indonesia. Methane emissions from the lowland paddy fields examined in Indonesia were higher than those of peaty paddy fields in Japan. There was generally a positive correlation (r(2) = 0.09; P < 0.1) between CH4 emissions and CH4 production activities in wetland soils. In Ozegahara, there was a positive relationship (r(2) = 0.80; P < 0.01) between CH4 production activities and soil pH, but there was no such relationship in Indonesia. The range of soil pH in Ozegahara was 5-7, while pH values in the Indonesian sites were lower than 5. There was a positive response of CH4 emission with respect to groundwater level in all of these areas. In Indonesia, land-use change from swamp and drained forest to cassava or coconut field lowered groundwater levels and decreased CH4 emission, while change to lowland paddy raised the groundwater level and increased CH, emission. Addition of acetate generally inhibited CH4 production during the early period (until 2 weeks) of incubation, then enhanced it afterward in both Ozegahara and Indonesian wetland soils. Addition of hydrogen mostly enhanced CH4 production. From the results of this study, CH4 fluxes from peat soil to the atmosphere were positively correlated with CH4 production activities, and CH4 production activity in peat soil was regulated by soil pH, while land-use change from wetland to upland crop lowered groundwater level and thus reduced CH4 production and enhanced CH4 oxidation.