马占相思夜间树干液流的分配及其对整树蒸腾估算的影响

PARTITIONING OF NIGHT SAP FLOW OF ACACIA MANGIUM AND ITS IMPLICATION FOR ESTIMATING WHOLE-TREE TRANSPIRATION

采用Granier热消散探针测定了马占相思(Acacia mangium)的树干液流,结合Li-6400光合测定系统测定的夜间叶片气孔导度和蒸腾,将夜间液流区分为夜间树干水分补充和叶片气孔蒸腾。叶片的蒸腾作用微弱,因此,夜间液流主要用于补充贮水部位的水分亏缺。马占相思夜间水分补充量年内和年际的变化不明显,树形特征的差异是解释夜间水分补充量变化的重要因子,夜间水分补充量对于整树蒸腾量的贡献因季节和树木径级的不同而有明显变化,但对整树总蒸腾量计算造成的误差可以忽略。

Aims This study was designed to analyze the partitioning of night sap flow in Acacia mangium and its implication for estimating whole-tree transpiration. Methods Analyses were performed on the partitioning of night sap flow into refilling of internal water storage and transpiration in A. mangium. Sap flow of trees was monitored continuously with Granier＇ s sensors for estimating whole-tree transpiration. Night sap flow data were used to calculate trunk water recharge. Possible night transpiration and stomatal conductance at leaf level in the canopy were measured with a Li-6400 photosynthesis measuring system. Important findings Vapor pressure deficit （VPD） and wind speed （V） could not fully explain sap flow in A. mangium at night （night leaf transpiration and stomatal conductance were weak）. Therefore, night sap flow of mature A. mangium trees was mainly associated with water recharge in the tnmk. No significant change in night water recharge of the tnmk was found at both seasonal and inter-annual scales. Morphological features of trees including diameter at the breast height （DBH）, tree height, and canopy size could explain variances of night water recharge. Furthermore, the error caused by night water recharge on whole-tree transpiration was negligible. The mechanisms and ecological implications of night sap flow partitioning of A. mangium deserve further investigation.