树木水力结构特征的昼夜变化规律

Day and night change of tree hydraulic architecture characteristics.

为更好地了解树木的水分生理特性 ,在北京林业大学校园内 ,选择 12个供水充分、生长正常的乔木、灌木和藤本树种为研究对象 ,在 2 0 0 1年 8月份天气晴朗之日 ,用改良的冲洗法测定各树种 1年生小枝导水率的昼夜变化 ,同时测定各树种的小枝水势、最大日净光合速率和蒸腾速率 .结果表明 ,各树种 1年生小枝的比导率和水势均有明显的昼夜变化规律 ;正常水分供给条件下 ,环孔材树种具有蒸腾快、比导率高且昼夜变幅大、光合能力强、小枝水势变化大、容易发生严重的空穴和栓塞等特点 ;与环孔材树种相比 ,无孔材树种的上述变化特点与之刚好相反 ;散孔材树种的特点则居于二者之间 ,但相对无孔材而言 。

In order to better understand the water physiology traits of trees, twelve healthy tree species with enough water supply were selected in the arboretum of Beijing Forestry University, which respectively belong to tall tree, shrub and liana. The day and night change of annual twigs hydraulic conductivity for different tree species were measured by the improved flushing method in the sunny days in August, 2001. At the same time, the twig water potential, net photosynthesis and transpiration rate were measured. The results show that all annual twigs, specific conductivity of different tree species have evident day and night change. When water supply is enough, the tree species with ring porous wood have higher transpiration and net photosynthesis rate, bigger specific conductivity and twigs water potential day and night change, and more serious cavitation and embolism, and so on. Compared with tree species with ring porous wood, the characteristics of tree species with non pored wood are just opposite. The characteristics of tree species with diffuse porous wood are between the above two, but more like tree species with ring porous wood comparing with tree species with non pored wood.