Abstract:

As part of China FLUX program, CO₂ fluxes were measured continuously by an open-path eddy covariance system over a broad-leaved Korean Pine forest in northeastern China, during the non-growing seasons. The CO₂ flux between forest and atmosphere ranged from -0.3 to 0.5 mg·m^-2 s^-1 during the observational days, with most positive fluxes occurred in the late autumn and the early spring. Though the air temperature was lower than 5 ℃, the studied forest still showed a clear evidence of carbon assimilation for several hours at noon of late autumn. When covered by snow, the efflux of CO₂ from forest was low and with a constant rate, whereas there was a peak of CO₂ efflux during snow-melt period. The net ecosystem carbon exchange (NEE) showed an exponential regression relationship with 5 cm depth soil temperature when the later was above 0 ℃. The total NEE was 127 g C·m^-2 in 190 observational days, which indicated that the broad-leaved Korean Pine forest of Changbai Mountain was functioning as a moderate carbon source outside the growing season.

Key words: broad-leaved and Korean Pine forest, CO₂ flux, eddy covariance method, carbon budget