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

Shinjiro Ohkubo; Yukiyoshi Iwata; Tomoyoshi Hirota

doi:10.1016/j.agrformet.2012.06.012

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

Shinjiro Ohkubo, Yukiyoshi Iwata, Tomoyoshi Hirota

Research output: Contribution to journal › Article

7 Citations (Scopus)

Abstract

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).

Original language	English
Pages (from-to)	25-34
Number of pages	10
Journal	Agricultural and Forest Meteorology
Volume	165
DOIs	https://doi.org/10.1016/j.agrformet.2012.06.012
Publication status	Published - Nov 15 2012
Externally published	Yes

All Science Journal Classification (ASJC) codes

Forestry
Global and Planetary Change
Agronomy and Crop Science
Atmospheric Science

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Ohkubo, S., Iwata, Y., & Hirota, T. (2012). Influence of snow-cover and soil-frost variations on continuously monitored CO ₂ flux from agricultural land. Agricultural and Forest Meteorology, 165, 25-34. https://doi.org/10.1016/j.agrformet.2012.06.012

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

abstract = "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).",

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