Ecosystem‐scale methane flux in tropical peat swamp forest in Indonesia

Abstract

Abstract Data on ecosystem‐scale methane ( CH 4 ) fluxes in tropical peatlands are currently lacking in the global CH 4 budget. Although the waterlogged Indonesian peatlands contain the largest share of peat carbon in South‐East Asia, ecosystem‐scale CH 4 budgets have not yet been reported, although these peatlands have the potential to emit CH 4 . We observed 1‐year variations in the ecosystem‐scale CH 4 flux in an undrained secondary peat swamp forest in central Kalimantan, Indonesia, using the eddy covariance method. We found that the peat swamp forest switched from being a CH 4 sink during the dry season (as low as −8.9 mg C m −2 day −1 ) to a source of CH 4 during the wet season (up to 10.7 mg C m −2 day −1 ), and this was dependent on changes in the groundwater level ( GWL ). The high GWL during the wet season enhanced the anaerobic CH 4 production in the surface layer that had more labile organic matter. However, the CH 4 emission also increased when the GWL dropped during dry spells in the wet season. The annual CH 4 budget in the studied tropical peat swamp forest (0.09–0.17 g C m −2 year −1 ) was much lower than that in northern, temperate, and subtropical wetlands. We found that CH 4 fluxes had almost no effect on the global warming gas budget of the peat swamp forest, and values were only a few percent less than the CO 2 fluxes at the same site. In addition, we conducted anaerobic soil incubation experiments to examine the effect of land‐use change on CH 4 production. The results indicated much higher CH 4 production potential in undrained forest soil than in drained or drained and burned ex‐forest soils. However, although CH 4 production decreased in drained soils relative to undrained soils, conserving pristine peat swamp forests with high GWL s is important to suppress global warming because CO 2 emissions increase in drained peatlands.