Environmental factors regulating winter CO 2 flux in snow-covered black forest soil of Interior Alaska

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 snowcovered 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 similar to 20% of annual soil-originated emissions.