Modelling terrestrial nitrous oxide emissions and implications for climate feedback.

Ecosystem nitrous oxide (N₂O) emissions respond to changes in climate and CO₂ concentration as well as anthropogenic nitrogen ( N) enhancements. Here, we aimed to quantify the responses of natural ecosystem N₂O emissions to multiple environmental drivers using a process-based global vegetation model (DyN- LPJ)., We checked that modelled annual N₂O emissions from nonagricultural ecosystems could reproduce field measurements worldwide, and experimentally observed responses to step changes in environmental factors. We then simulated global N₂O emissions throughout the 20th century and analysed the effects of environmental changes., The model reproduced well the global pattern of N₂O emissions and the observed responses of N cycle components to changes in environmental factors. Simulated 20th century global decadal-average soil emissions were c. 8.2-9.5 Tg N yr⁻¹ (or 8.3-10.3 Tg N yr⁻¹ with N deposition). Warming and N deposition contributed 0.85 ± 0.41 and 0.80 ± 0.14 Tg N yr⁻¹, respectively, to an overall upward trend. Rising CO₂ also contributed, in part, through a positive interaction with warming., The modelled temperature dependence of N₂O emission ( c. 1 Tg N yr⁻¹ K⁻¹) implies a positive climate feedback which, over the lifetime of N₂O (114 yr), could become as important as the climate-carbon cycle feedback caused by soil CO₂ release. [ABSTRACT FROM AUTHOR]