Nitrous Oxide Emissions from Permafrost Regions: Progresses and Prospects

Climate warming promotes the emission of greenhouse gases (GHGs), such as nitrous oxide (N₂O) from soils while exacerbating non-carbon-climate feedbacks in the permafrost zone. Although nearly 1/4 of the land surface in the Northern Hemisphere is covered by permafrost, current research remains constrained in its understanding of the production, accumulation, diffusion and release processes of N₂O from permafrost-affected soils, along with the associated regulatory mechanisms. In this sammary, the mechanisms of the N₂O generation process were thoroughly examined by synthesizing previous research findings. The differentiated observational schemes, including N₂O analysis methods (surface flux and profile concentration), were systematically evaluated. Additionally, this sammary addressed the controversy surrounding N₂O pulse emissions during the thawing period, the patterns of daily changes in N₂O flux and their driving factors, the characteristics of variations in N₂O concentration in the soil profile and its sources, and the effects of plant growth on soil N₂O emissions. In the future, we should strengthen the error assessment of N₂O flux observation methods, increase the observation frequency of surface flux and profile concentration during the non-growing season, and make effective use of new techniques such as isotopic analysis and molecular biology to elucidate the mechanisms underlying N₂O emissions triggered by soil freezing and thawing. Additionally, we should assess the contribution of pulsed emissions to the annual cumulative fluxes during freezing and thawing periods, to provide theoretical support for optimizing the specifications of observation methods and investigating the biological and physical mechanisms of N₂O emissions during these critical periods.