应用热脉冲技术对棘皮桦和五角枫树干液流的研究

应用热脉冲方法，对暖温带落叶阔叶森林主要树种棘皮桦Ｂｅｔｕｌａｄａｈｕｒｉｃａ和五角枫Ａｃｅｒｍｏｎｏ树干的流液量变化及其与环境因子相关性进行研究，结果表明：①在正常生长状态下，棘皮桦树干单位面积液流通量为０．１５８Ｌ·ｃｍ－２·ｄ－１，五角枫为０．２１３Ｌ·ｃｍ－２·ｄ－１．如果忽略树冠部位的水分贮存，可认为五角枫的蒸腾耗水强度较大．②两树种形成层以下不同深度的树液流速具有相同的日变化趋势．在正午前后各深度流速值均达到最大，各深度流速差值亦达到最大．最大液流速度相对位点棘皮桦在位于距形成层相对距离０．３处，五角枫在位于距形成层相对距离０．５处，表明在上述边材区域具有最高的水分传导率．③棘皮桦、五角枫均存在夜间明显的树干液流上升现象，以补充树冠部的水分贮存．作者认为阔叶树种夜间树液上升的动力是根压．④棘皮桦、五角枫的白昼树液流量变化呈现多峰状曲线．树干液流量变化与环境中气象因子变化密切相关．逐步回归的结果表明，在不同树种中，影响树干液流量的主要因子是不同的．

A Study on the Volume and Velocity of Stem Sapflow of Betula dahurica and Acer mono Forests by the Heat Pulse Technique

In this paper,the heat pulse technique was applied to study the stem sapflow of two main tree species in deciduous broad leaved forest in July and August of 1994.The results show that,1)in the natural conditions,the intensity of sapflow of Betula dahurica was 0.158 L·cm-2·d-1,and that of Acer mono was 0.213L·cm-2·d-1;2)The velocity of sapflow at different depths below the cambium showed the same temporal changes of the investigated tree species.At noon it reached the maximum,and its difference did so.The ring area with the highest water conductivity at radial section was different in the above tree species;3)Even at night,the ascent of sapflow could be observed in the above main tree species owning to the existence of root pressure;4)The diurnal change of volume of sapflow showed minor fluctuations closely related to the change of micrometeorological factors,and the most significent factors that influenced the volume of sapflow were different in the tree species.