关键词: 土壤温室气体通量, 土壤冻融, 温带森林, 定位观测, 箱式法

Abstract: Soil greenhouse gas emissions are a critical component in assessing the function of ecosystems as carbon sources and sinks. Soil freeze-thaw cycles influence these emissions by altering soil carbon (C) and nitrogen (N) cycling. However, there remains a limited understanding about the temporal variations in soil greenhouse gas fluxes during freeze-thaw periods and the regulating factors. We conducted in-situ observations of soil greenhouse gas fluxes with the method of static chambers in a temperate broadleaf Korean pine forest in Changbai Mountain, and analyzed the impact of soil variables on greenhouse gas emissions. The results showed that soils acted as a CO₂ and N₂O source and a CH₄ sink during 2019-2021. The annual cumulative fluxes of soil CO₂, CH₄, and N₂O were 107.96±8.32, -50.99±7.41, and 10.17±2.41 mmol·m^-2·a^-1, respectively. Soil CO₂ emission and CH₄ uptake during the spring freeze-thaw period were significantly lower than those in the growing season, while N₂O emission was much higher. The cumulative fluxes of soil CO₂ and CH₄ during the spring freeze-thaw period contributed 5.51% and 8.44% to the annual total fluxes respectively, while the contribution of N₂O flux reached 51.43%. Multivariate regression analysis revealed that during the spring freeze-thaw period, CO₂ fluxes increased with rising soil temperature, and that soil temperature had minimal effects on CH₄ and N₂O fluxes. In the growing season, CO₂ fluxes were primarily influenced by soil temperature and soil NO₃^- content in surface layer. CH₄ fluxes were mainly regulated by soil moisture, while N₂O fluxes were weakly affected by soil pH. Soil freeze-thaw exerts a remarkable effect on the temporal variations of greenhouse gas emissions. Considering the complexity of soil C and N cycling and soil heterogeneity, more observations are required on greenhouse gas emissions and control mechanisms to accurately assess the role of soil in ecosystem C sequestration.

Key words: soil greenhouse gas flux, soil freeze-thaw, temperate forest, position observation, static chamber method