Carbon Dioxide and Methane Emissions from Peat Soil in an Undrained Tropical Peat Swamp Forest

This study investigates the factors controlling the soil CO 2 and CH 4 fluxes and quantifies annual cumulative soil respiration ( R S ), heterotrophic respiration ( R H ), and soil CH 4 emission in an undrained forest on tropical peat by continuous measurement using an automated chamber system for 2 years. Daily mean soil CO 2 flux was increased by lowering groundwater level (GWL), which indicates oxidative peat decomposition is promoted by the enhancement of aeration. On the other hand, soil CH 4 flux showed a bell-shaped relationship with GWL, which suggested that the development of anaerobic conditions promoted CH 4 production by the rise in GWL, whereas hydrostatic pressure suppressed CH 4 diffusion when the GWL was above the peat surface. Mean annual gap-filled CO 2 emissions were 926 ± 610 and 891 ± 476 g C m −2 y −1 (mean ± 1 SD) for R S ( n = 10) and R H ( n = 6), respectively, and were not significantly different from each other. The annual R H in this study was similar to that of previous studies despite the higher annual mean GWL in this study, possibly due to the inclusion of litter decomposition in contrast to most of the previous studies in tropical peatland. Mean annual gap-filled CH 4 emission was 4.32 ± 3.95 g C m −2 y −1 ( n = 9), which was the high end of the previous studies in tropical peatland due to higher annual mean GWL in this study. In conclusion, R S was lower and CH 4 emission was higher in the undrained peat swamp forest than those previously reported for drained and disturbed forests on tropical peat.