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.