Wetlands present a paradox in N₂O research: they can be both sources and sinks depending on hydrological conditions. Understanding this variability is critical for accurately quantifying natural N₂O fluxes and predicting how changing land use and climate will affect these emissions.
Redox Controls
Wetland N₂O dynamics are controlled primarily by soil redox conditions. In continuously waterlogged soils, complete denitrification to N₂ tends to dominate, making these environments N₂O sinks or negligible sources. In partially drained or fluctuating water table wetlands, incomplete denitrification and active nitrification in oxic surface layers combine to produce significant N₂O emissions.
Permanently flooded: often near-zero or negative
Seasonally flooded: 0.1–2.5 mg N₂O-N/m²/day
Drained peatlands: 1–10+ mg N₂O-N/m²/day
Rewetted peatlands: variable, often decreasing
Peatland Drainage
When peatlands are drained for agriculture — as has occurred extensively in Southeast Asia, Europe, and North America — N₂O emissions increase dramatically. Drained tropical peatlands in Indonesia and Malaysia emit among the highest N₂O fluxes ever measured in terrestrial ecosystems. Rewetting these systems is a high-priority mitigation option, though N₂O emissions may temporarily increase during the rewetting transition.