Abstract: Based on the two-year continuous observation on the carbon exchange of Chinese boreal forest during its growth seasons in 2007 and 2008 by the method of open path eddy covariance, this paper analyzed the seasonal dynamics of the gross ecosystem productivity (GEP), ecosystem respiration (R_e), and net ecosystem carbon exchange (NEE) of the forest, with related regulation mechanisms approached. The GEP, R_e, and NEEof the forest reached to their maximum in the vigorous growth period from late June to mid August, but the dates of the maximum appeared differed. The mean daily GEP, R_e, and NEE were 19.45, 15.15, and -1.45 g CO₂·m^-2·d^-1 in 2007, and 17.67, 14.11, and -1.37 g CO₂·m^-2·d^-1in 2008, respectively. The intensity of the carbon exchange during growth season was obviously stronger in 2007 than in 2008, possibly due to the higher mean air temperature (12.46 ℃ in 2007 vs. 11.04 ℃ in 2008) and the higher mean photosynthetically active radiation (PAR) (697 μmol·m^-2·s^-1 in 2007 vs. 639 μmol·m^-2·s^-1 in 2008). The GEP had close linear relationships with air temperature and PAR, and the correlation coefficient of GEP and air temperature was around 0.55(P<0.01). The R_e was mainly controlled by air temperature, with the correlation coefficient being 0.66-0.72 (P<0.01), and the NEE was mainly controlled by PAR, with the correlation coefficient being 0.59-0.63 (P<0.01).

Key words: Chinese boreal forest, gross ecosystem productivity, ecosystem respiration, net ecosystem carbon exchange, affecting factor