Integrating field, mesocosms, and laboratory approaches to characterise denitrification-driven nitrous oxide hot moments in European wetlands

A substantial part of terrestrial nitrous oxide (N2O) emissions originates from denitrification in wetlands, and this contribution is expected to rise with ongoing land-use changes, such as wetland drainage, agricultural conversion, and peatland degradation, as well as under global warming. Capturing the spatial and temporal dynamics of N2O emissions through measurements and numerical modelling remains challenging, as extreme N2O peaks occur during short-lived transient events (hot moments). In this study, we combined three experimental approaches (in situ field monitoring, mesocosm experiments, and slurry soil incubations in the laboratory) to characterise N2O hot moments of denitrification across 21 diverse European wetlands. Each approach captured different aspects of N2O emission dynamics, and their combination revealed additional features, including the timing and magnitude of N2O fluxes, denitrification efficiency (ratio of N2O to N2O + N2 emitted), and an estimate of the proportion of soil actively undergoing denitrification. We encourage the use of these key determinants to improve and parametrise future denitrification models that aim to quantify transient N2O hot moments.