CO₂ Balance of Tropical Peat Ecosystems

Abstract

We reanalyzed long-term field data of CO₂ flux, including net ecosystem CO₂ exchange (NEE), ecosystem respiration (RE)_, and soil CO₂ efflux (RS) to examine their seasonal and interannual variations for three conditions of disturbance (almost undrained peat swamp forest (PSF), drained PSF, and drained burnt ex-PSF) in a tropical peat area in Central Kalimantan, Indonesia. In addition, we simulated the CO₂ flux on a monthly basis using empirical equations shown by our previous studies under four scenarios of seasonal variations in groundwater levels (GWL). The GWL has a large interannual variation in October and November. The rainy season usually begins in October, but the onset is delayed until November in El Niño years, making the interannual variation in CO₂ fluxes the largest in these 2 months owing to the large GWL variations. On an annual basis, minimum monthly-mean GWL explained 82 % of interannual variations in NEE for the two PSFs. The linearity suggests that 10-cm drawdown of minimum monthly-mean GWL increases NEE or net ecosystem CO₂ emission by 48.5 gC m⁻² year⁻¹ from PSF, independently of drainage degree. It can be said that minimum monthly-mean GWL is a practical measure to assess annual NEE of PSF.