Monthly Diurnal Variations in Soil N₂O Fluxes and Their Environmental Drivers in a Temperate Forest in Northeastern China: Insights from Continuous Automated Monitoring

Global warming, driven by increased greenhouse gas emissions, is a critical global concern. However, long-term trends in emissions remain poorly understood due to limited year-round data. The automated chamber method was used for continuous monitoring of soil N₂O fluxes in a mixed forest in Northeast China’s Changbai Mountains, analyzing monthly diurnal patterns and their relationships with soil temperature (Ts) and soil volumetric water content (VWC). The results revealed significant diurnal and seasonal variations, with peak emissions at 11:00 during the growing season (May–October) and elevated nighttime fluxes in winter (March, April, November, and December). The optimal sampling time was 14:00, closely reflecting daily mean fluxes. Soil Ts and VWC were key drivers, with seasonal variability in their effects: N₂O fluxes showed no significant relationship with Ts in January but strong correlations in February and March. The growing season Q₁₀ values ranged from 0.4 to 7.2 (mean = 2.5), indicating high-temperature sensitivity. Soil VWC effects were complex, with moderate VWC promoting denitrification and excessive VWC suppressing microbial activity. These findings provide critical insights for optimizing N₂O monitoring and improving emission estimates.