| Summary: | The relationship between soil temperature and CO flux from undisturbed soil cores was examined during freeze-up of arctic tundra. Three habitats which dominate tundra topography, polygon trough, ridge and basin, produced significantly different amounts of CO when soil temperatures were above 0 C. A significant positive correlation between soil temperatures between 10 to -7 C and CO flux from each habitat was established. Substantial quantities of CO were produced during freeze-up period when soil temperatures remained near 0 C for an extended period, and the CO production continued at reduced levels as the soil temperature dropped below 0 C. When soil temperatures reached -7 C and the study was terminated, the CO flux was reduced to a low level, but did not reach extinction. A maximum CO flux of 2925 mg CO/m²/day from the trough habitat was observed when the soil temperature was 10 C, and the minimum CO flux of 131 mg/m²/day was observed when the soil temperature was -7 C. These data are consistant with the hypothesis that soil microorganisms in arctic tundra are capable of physiological activity in the range of 0 to -7 C. Master of Science
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