CO_2 and H_2O gas-exchanges of trees in changeable environments

以扁柏（Chamaaparis obtusa（Sieb. et Zucc.）Endl.）树木生长在一个开放的气体交换系统领域。这些树枝大小相似，位于树冠内的相似位置。一个分支经受具有约370 μ mol/L的CO_2浓度的环境空气<-1>。夜间呼吸速率在CO_2浓度升高时高于环境CO_2浓度。各月夜间呼吸与夜间气温的关系均为指数函数。两种CO_2处理间回归线的分离度随季节的推移逐渐增大。夜间呼吸的Q值<10>在CO_2浓度升高时为1.9 ~ 3.7，而在大气CO_2浓度升高时为2.4 ~ 4.5。在<10>CO_2浓度升高和大气CO_2浓度升高的情况下，Q_2与月平均夜间气温呈负相关。两种CO_2处理下暗呼吸速率的日变化趋势基本一致，与温度变化基本同步。大气CO_2浓度升高时，土壤呼吸速率与大气CO_2浓度的比值从1.0逐渐增大到1.5。结果表明，CO_2浓度和温度对呼吸活动有很强的交互作用。

The effect of elevated atmospheric CO_2 concentrations on the nighttime respiration were examined for two sample branches of a hinoki cypress (Chamaecyparis obtusa (Sieb.et Zucc.) Endl.) tree growing in the field with an open gas exchange system. The branches were of a similar size and located at a similar position within the crown. One branches was subjected to ambient air which had a CO_2 concentration of about 370 mu mol mol^<-1>. The nighttime respiration rate was higher in elevated CO_2 level than in ambient CO_2 level. The relationship between hourly nighttime respiration and the corresponding nighttime air temperature was fitted with the exponential function in every month. The segregation of the regression lines between the two CO_2 treatments increased gradually as the season progressed. The Q_<10> values for nighttime respiration were lower in elevated CO_2, i.e.1.9 to 3.7, than in ambient CO_2, i.e.2.4 to 4.5 in every month. The Q_<10> was inversely related to the monthly mean nighttime air temperature in both elevated and ambient CO_2. The estimated daily dark respiration rate showed a similar seasonal pattern in both CO_2 treatments, which almost synchronized with the temperature change. The respiration ratio of elevated CO_2 to ambient CO_2 increased gradually from 1.0 to 1.5. The present results indicated that the CO_2 level and the temperature have a strong interactive effect on respiratory activities.