TERRAPUB Geochemical Journal

Geochemical Journal, Vol. 51 (No. 4), pp. 359-371, 2017

Environmental factors regulating winter CO2 flux in snow-covered black forest soil of Interior Alaska

Yongwon Kim,1* Yuji Kodama2 and Gilberto J. Fochesatto3

1International Arctic Research Center (IARC), University of Alaska Fairbanks, Fairbanks, AK 99775-7335, U.S.A.
2Arctic Environment Research Center, National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
3Department of Atmospheric Sciences, Geophysical Institute and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, AK 99775, U.S.A.

(Received February 4, 2016; Accepted February 6, 2017)

Abstract: High latitude winter soil CO2 emission is an important component of the annual carbon budget at regional and global scales. Here, continuous monitoring of winter CO2 flux-measurement in black spruce forest soil of interior Alaska was performed using non-destructive infrared (NDIR) CO2 sensors at 10, 20, and 30 cm above the surface during the snow-covered period of 2006/7. To analyze the effects of environmental factors in the CO2 flux, the dataset was clustered based on major meteorological patterns. Periods were selected based on atmospheric pressure corresponding to well-identified synoptic large scale patterns: ambient pressure larger than 1000 hPa (HP: high pressure), atmospheric pressure is in the range between 985 and 1000 (IP: intermediate pressure), and cases in which the atmospheric pressure was below 986 hPa (LP: low pressure). Furthermore, the dataset corresponding to the snowmelt period (MP) was treated independently for all values of ambient pressure. Winter CO2 fluxes were 0.20 ± 0.02, 0.23 ± 0.02, 0.29 ± 0.03, and 0.17 ± 0.02 gC m−2 d−1 for the HP, IP, LP, and MP phases, respectively. Atmospheric and soil temperature at 5 cm depth, modulated by atmospheric pressure, were significant factors in regulating winter soil-originated CO2 emission and fluctuation. We found that changes in CO2 fluxes during the snow-covered period can be as much as 35% on the average. These results are significant, as wintertime CO2 emissions represent ∼20% of annual soil-originated emissions.
Key words: winter CO2 flux, ambient pressure, air temperature, snow depth, black spruce forest of Alaska

*Corresponding author E-mail: kimyw@iarc.uaf.edu

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