非生长季长白山红松针阔叶混交林CO_2通量特征

Non-growing Seasons CO_2 Flux of a Broad-leaved Korean Pine Forest in Changbai Mountain

采用开路式涡度相关系统对长白山红松针阔叶混交林非生长季的CO2通量特征进行连续监测.结果显示：非生长季CO2通量变动范围为-0.3～0.5 mg·m-2s-1;秋末与初春均为显著的释放过程,虽然气温低于生物学最低温度,但在晴朗的午间,森林仍有数小时表现为碳汇的特征;在冬季覆雪状态下,森林存在微弱的相对恒定的CO2释放,在融雪阶段有一释放高峰;土壤温度高于0℃时,净生态系统碳交换量与5 cm深土壤温度呈指数相关变化.观测期间（190 d）,长白山红松针阔叶混交林净碳交换量为127 g C·m-2,整体表现为一定强度的碳释放.

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.