Ecosystem-scale measurements of CO2 and CH4 fluxes from a tropical peatland in Sarawak, Malaysia

Tropical peatlands of Southeast Asia are a globally important carbon reservoir, storing an enormous amount of soil organic carbon as peat. These ecosystems are complex and poorly understood with large unknown biogeochemical processes. Despite the huge carbon stocks in these ecosystems, data on ecosystem-scale carbon dioxide (CO₂) and methane (CH₄) fluxes are still limited in comparison with mid- and high-latitude peatland ecosystems. The recent increase in the intensity of climate anomaly such as El Niño may alter the hydrological regime of this ecosystem, thus affects its carbon cycling. It is crucial to quantify the CO₂ and CH₄ fluxes of the ecosystem and understand their responses to environmental changes to predict the role of peat swamp forest in global carbon cycles. To date, the application of the eddy covariance technique to measure the ecosystem-scale CO₂ and CH₄ fluxes in tropical peatlands is still limited to few studies in Malaysia and Indonesia.

In 2010, we established a long-term greenhouse gas fluxes monitoring using the eddy covariance technique over a peat swamp forest in Sarawak, Malaysia. Here, we present the net ecosystem exchange of CO₂ (NEE) and CH₄ (F_CH4) from February 2014 to January 2017 (3 years). We had quantified the NEE and F_CH4, the diurnal and seasonal variations of NEE and F_CH4, and the response of NEE and F_CH4 to GWL. The F_CH4 was determined half-hourly as the sum of eddy CH₄ flux and CH₄ storage change in an air column below the flux measurement height. We had determined the global warming potential of this ecosystem from annual NEE and F_CH4 using sustained-flux global warming potential (SGWP).  The annual F_CH4 was converted into a CO₂ equivalent unit using an SGWP factor of 45 which represents the SGWP for CH₄ over a timescale of 100 years. Our preliminary result showed that the CH₄ emission potentially offset the CO₂ sequestration, which was higher than those reported in other regions in the world.