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

Abstract

Soil freeze-thaw cycles are associated with nitrous oxide (N 2 O) 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 N 2 O emissions in permafrost peatlands. Therefore, we used static chamber-GC techniques to measure N 2 O 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 N 2 O source/sink process during the mild, moderate, and severe intensities of AFT . The intensities of AFT significantly affected N 2 O fluxes, and vegetation types showed no significant effect. However, the interaction between vegetation types and intensities of AFT significantly influenced the N 2 O fluxes in the three permafrost peatlands. During the mild intensity, N 2 O fluxes were driven by surface temperature and NO 3 − -N content in the shallow peat layer; during the moderate intensity, N 2 O fluxes were driven by soil moisture content in the shallow peat layer; during the severe intensity, N 2 O fluxes were driven by the soil NH 4 + -N content and DOC content. These results demonstrated that the interaction of vegetation types and intensities of AFT affected in-situ N 2 O emissions in the permafrost peatlands. This work could make up for the study blank of in-situ N 2 O emissions during the AFT in the permafrost peatlands of the Great Hinggan Mountains, Northeast China. • The intensities of autumn freeze-thaw cycles significantly affected N 2 O fluxes. • Vegetation types of permafrost peatland has no significant effect on N 2 O fluxes. • Interaction of vegetation types and freeze-thaw intensities affected N 2 O emissions. • N 2 O fluxes were driven by temperature, NO 3 − -N, moisture, NH 4 + -N and DOC content.