Methane and carbon dioxide production and emission pathways in the belowground and draining water bodies of a tropical peatland plantation forest

Peatlands are crucial yet vulnerable carbon stores. Here, we investigated carbon biogeochemical processes in tropical peatlands converted to plantations. We measured carbon dioxide (CO2) and methane (CH4) concentrations, stable isotope ratios and radiocarbon content in an experimental Acacia crassicarpa plantation in Sumatra, Indonesia. We found exceptionally high levels of dissolved organic carbon (DOC), CO2, and CH4 in porewater and drainage networks, indicating that Acacia plantations are carbon hotspots due to their high productivity and exposed carbon-dense substrates. Stable isotope models revealed that while CO2 and CH4 are produced belowground, CH4 contribution was lower than in natural undrained peatlands. Radiocarbon analysis suggested that remobilized carbon contributed to the carbon pool, with a median age of ∼470 years before present. These findings constrain the links between land-use, water table levels, and carbon dynamics, with implications for carbon management in plantation peatlands.