Influence of snow-cover and soil-frost variations on continuously monitored CO 2 flux from agricultural land

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