The interaction between vegetation types and intensities of freeze-thaw cycles during the autumn freezing affected in-situ soil N2O emissions in the permafrost peatlands of the Great Hinggan Mountains, Northeastern China

Soil freeze-thaw cycles are associated with nitrous oxide (N2O) emissions, and climate warming changes the freeze-thaw process of permafrost and delays the starting period of soil freezing. However, it remains unclear how freeze-thaw cycles of the autumn freezing period (AFT) affect in-situ soil N2O emissions in permafrost peatlands. Therefore, we used static chamber-GC techniques to measure N2O emissions in the three permafrost peatlands [Calamagrostis angustifolia peatland (CAP), Larix gmelina-Sphagnum peatland (LGS), and Eriophorum vaginatum peatland (EVP)] during the AFT of 2019. Results showed that the three types of permafrost peatlands presented the conversion of in-situ soil N2O source/sink process during the mild, moderate, and severe intensities of AFT. The intensities of AFT significantly affected N2O fluxes, and vegetation types showed no significant effect. However, the interaction between vegetation types and intensities of AFT significantly influenced the N2O fluxes in the three permafrost peatlands. During the mild intensity, N2O fluxes were driven by surface temperature and NO3−-N content in the shallow peat layer; during the moderate intensity, N2O fluxes were driven by soil moisture content in the shallow peat layer; during the severe intensity, N2O fluxes were driven by the soil NH4+-N content and DOC content. These results demonstrated that the interaction of vegetation types and intensities of AFT affected in-situ N2O emissions in the permafrost peatlands. This work could make up for the study blank of in-situ N2O emissions during the AFT in the permafrost peatlands of the Great Hinggan Mountains, Northeast China.