Changes in cryospheric snow accumulation, snowmelt, and soil freezing and thawing might influence the ground-surface CO 2 flux and cumulative winter CO 2 flux from agricultural land. We continuously observed CO 2 flux using automatically closing chambers at an untreated control plot and a plot with snow removal in northern Japan. The CO 2 in soil pores at 10-cm depth increased by 6.5ppmvday -1 as soil began to freeze, but it increased dramatically (to 49ppmvday -1) after snowmelt water infiltrated the soil and froze. The soil-frost layer constrained gas diffusion into the air, and the barrier strengthened as the frozen snowmelt water decreased the air volume in soil pores. Leached gas CO 2 from the freezing snowmelt water also increased gas CO 2 concentration in soil. As the soil thawed, the CO 2 concentration decreased drastically, at 790ppmvday -1. However, these changes had little effect on CO 2 flux. The soil CO 2 concentration remained stable after snow cover reached 30cm in the control plot. Low CO 2 flux in both plots occurred during the winter. No clear relation was found between CO 2 flux and snow depth or soil-frost depth because of the small CO 2 source at this site. We also considered how the presence of the chamber influenced soil temperatures and water contents. During the snow-free season, the chamber mitigated diurnal changes in soil temperature. The daily average soil temperature differed from that in the natural state by -1.7°C to 6.3°C. This fluctuation of temperature corresponded to the fluctuation of CO 2 flux, which ranged from 91% to 143% of the CO 2 flux in the natural state based on the temperature-response equations. The chamber had little influence on the soil temperature during the snow-cover period, and did not influence soil water content throughout the study period. Cumulative winter CO 2 emissions were 17.2gCm -2 (over 143 days) in the control plot and 13.4gCm -2 (over 151 days) in the treated plot (10.0 and 7.5% of annual accumulation, respectively).
All Science Journal Classification (ASJC) codes
- Global and Planetary Change
- Agronomy and Crop Science
- Atmospheric Science