涡动相关法与波文比-能量平衡法测算森林蒸散的比较研究——以长白山阔叶红松林为例

Comparison of Eddy Covariance and BREB methods in determining forest evapotranspiration——Case study on broad-leaved Korean pine forest in Changbai Mountain

分别采用涡动相关法与波文比-能量平衡法(BREB法)测算了长白山阔叶红松林2002年9、10月的森林蒸散量。结果表明,9月,涡动相关法与BREB法测算的森林蒸散量分别为83.1和87.9 mm,后者相对于前者的误差不到6%,且两者日蒸散量有较好的相关性(0.78),表明涡动相关法与BREB法在森林蒸散研究中有很好的一致性。10月,随着秋季落叶,林内水汽压梯度减小。涡动相关法测算的森林蒸散量为42.5 mm,BREB法测算的结果为49.1 mm,后者相对于前者的误差达到了16%,两者日蒸散量相关系数为0.53。在水汽压梯度较小时,BREB法会产生较大误差。9月中上旬,森林主要热量消耗是用于蒸散,约占辐射平衡量的71%;落叶后,森林主要热量消耗变为森林-大气间的感热交换,蒸散耗热只占辐射平衡量的40%。

In this paper, a comparative study was made to use the methods of Eddy Covariance and Bowen-Ratio Energy Balance （BREB） in continually measuring the evapotranspiration of broad-leaved Korean pine forest in Changbai Mountain from Sept, 1 to Oct. 31, 2002. The results showed that in September, the evapotranspiration measured by Eddy Covariance and BREB was 83.1 and 87.9 mm, respectively, the error of BREB relative to Eddy Covariance was less than 6 %, and the correlation between their daily total evapotranspiration was significant （0.78）, suggesting that BREB was in good agreement with Eddy Covariance in forest evapotranspiration measurement. In October, the evapotranspiration measured by Eddy Covariance and BREB was 42.5 and 49.1 mm, respectively, the error of BREB relative to Eddy Covariance was up to 16 %, and the correlation coefficient between their daily total evapotranspiration was 0.53, which suggested that the error of BREB method increased with decreasing vapour pressure gradient. In early and mid- September, evapotranspiration consumed 71% of total forest available energy, while most of the available energy was used for the transformation of sensible heat, and only 40 % of total available energy was used by evapotranspiration after the forest was leafless.