Nitrous oxide fluxes from tropical peat with different disturbance history and management

Abstract

Tropical peatlands are one of the most important terrestrial ecosystems in terms of impact on the atmospheric greenhouse gas composition. Currently, greenhouse gas emissions from tropical peatlands following disturbances due to deforestation, drainage or wildfire are substantial. We quantified in situ nitrous oxide (N₂O) fluxes during both dry and wet seasons using a closed chamber method at sites that represented differing land uses and land use change intensities in Central Kalimantan, Indonesia. Cumulative N₂O fluxes were compared with carbon dioxide (CO₂) and methane (CH₄) fluxes. <br><br> The mean N₂O flux rates (N₂O-N &plusmn: SD, mg m⁻² h^&minus;1) varied as follows: drained forest (0.112 ± 0.293) > agricultural peat at the Kalampangan site (0.012 ± 0.026) > drained burned peat (0.011 ± 0.018) > agricultural peat at the Marang site (0.0072 ± 0.028) > undrained forest (0.0025 &plusmn; 0.053) > clear-felled, drained, recovering forest (0.0022 &plusmn; 0.021). The widest N₂O flux range was detected in the drained forest (max. 2.312 and min. −0.043 mg N₂O-N m⁻² h^&minus;1). At the other flux monitoring sites the flux ranges remained at about one tenth that of the drained forest site. The highest N₂O emission rates were observed at water tables close to the peat surface where also the flux range was widest. Annual cumulative peat surface N₂O emissions (expressed in CO₂ equivalents as a percentage of the total greenhouse gas (N₂O, CO₂ and CH₄) emissions) were 9.2 % at highest, but typically ~1 %. Average N₂O fluxes and also the total of monitored GHG emissions were highest in drainage-affected forest which is characterized by continuous labile nitrogen availability from vegetation, and water tables typically below the surface.