Ecosystem-Scale Carbon Balance to Improve the Emission Factors for Acacia Plantations on Tropical Peatlands 

Peatlands are among the most carbon‑rich terrestrial ecosystems and play a key role in the global carbon cycle. However, managed peatlands for agriculture and silviculture emits significant carbon. Southeast Asia hosts approximately one third of tropical peatlands with around half of it are managed for agriculture and silviculture to support economic and population growth.Substantial uncertainties remain in existing estimates with a large range. Partially, such uncertainties can be attributed to both limited field measurements from major land uses and also lack of direct measurements of carbon loss when using short‑term chamber and subsidence approaches. Despite strong interests from scientific community and policy makers, current Intergovernmental Panel on Climate Change (IPCC) Tier 1 emission factors (EFs) for tropical peatlands are derived from short‑term chamber and subsidence measurements, which may not fully capture total ecosystem carbon dynamics and introduce potential uncertainty into emission estimates.Using continuous 30-minutes eddy covariance measurements, we quantified comprehensive greenhouse gas (GHG) balance of an Acacia crassicarpa plantation on tropical peatland in Sumatra, Indonesia. Net ecosystem carbon dioxide (CO₂), methane (CH₄), and soil nitrous oxide (N₂O) exchange to estimate the GHG exchange.Considering carbon export from harvested wood over a complete plantation rotation as emissions, the Acacia plantation exhibited net CO2 emissions of 30.0 ± 4.6 tCO₂-eq ha⁻¹ yr⁻¹, approximately 50% lower than IPCC Tier 1 EFs. Emissions were also ~20% lower than degraded peatlands in the same landscape, and the partial use of harvested biomass for bioenergy potentially further reduces the plantation’s overall climate impact.These findings indicate that current emission factors by IPCC may not fully represent GHG dynamics in existing Acacia plantations on tropical peatlands. Incorporating ecosystem-scale observations and full plantation rotation assessment into Tier 3 EFs estimation improved the accuracy in GHG emissions from managed tropical peatland ecosystems.