Assessing nitrous oxide emissions from European peatlands at variable degradation status and land use to improve national GHG inventories

Nitrous oxide (N₂O) is 300 times more potent than carbon dioxide in atmospheric warming and it is the main driver of stratospheric ozone depletion. The N₂O emissions from peatlands are often estimated by applying published IPCC default emission factors, neglecting the stages of peat degradation. Here, we introduce soil bulk density (BD) as a proxy for peat degradation to estimate N₂O emissions. A synthesis of soil physical and geochemical data from global boreal and temperate peatlands revealed a strong relationship between BD and annual N₂O emissions (R2=0.56, p<0.001), and the BD was superior to other parameters (C/N, pH) in estimating annual N₂O emissions. The results indicate that the more a peat soil is degraded, and the larger the values for BD are the larger the risk of N₂O emission in peaty landscapes. Even after rewetting, highly degraded soils may exhibit large N₂O release rates. A BD distribution map of European peatlands was generated and the estimated annual N₂O-N emissions from European peatlands sum up to approximately 46.9 Gg. In conclusion, this research shows that explicitly accounting for the stage of peat degradation as expressed in measured BD values gives reliable N₂O emission estimates from peatlands on a national scale.