北京城市绿化树种的水力结构特征

为了更好地了解城市绿化树种的水分生理特性,在北京林业大学校园内,选择8个正常管理、正常生长的乔木和灌木树种为研究对象,在夏、秋季(5—10月)选择天气晴朗之日,用压力室法和改良的冲洗法测定小枝的水势和水力结构参数.实验结果表明:阔叶树种的水势和导水率变幅大于针叶树种,水势和比导率的日变化趋势并非完全一致.所测树种中导水率变幅的大小为国槐>女贞>黄栌>旱柳>油松>侧柏>沙地柏>小叶黄杨.木质部栓塞程度大小和树种有关,环孔材树种比导率的昼夜变幅高于散孔材,其大小为黄栌>国槐>旱柳>小叶黄杨,月均木质部栓塞程度为环孔材树种>散孔材树种>针叶树种,即无孔材.阔叶树木质部栓塞季节变化规律明显:夏季>秋季,最小的木质部栓塞出现在秋季降水最多的月份.

Hydraulic architecture characteristics of urban afforestation trees in Beijing.

In order to better understand the water physiology traits of urban afforested trees, eight healthy species of tree and shrub with regular management were selected in the arboretum of Beijing Forestry University. Water potential and the parameters of hydraulic architecture were measured by the improved flushing method in sunny days in the seasons of summer and autumn (July to October). Experiment showed that the changing range of water potential and hydraulic conductivity in twigs of hardwood trees were higher than that of conifers, the diurnal changes of water potential and specific conductivity were not absolutely the same. The changing range of hydraulic conductivity in species was Sophora japonica > Ligustrum lucidum> Cotinus coggygria > Salix matsudana > Pinus tabulaeformis > Platycladus orientalis > Sabina vulgaris > Buxus sinica. The degree of xylem embolism was related with tree species. The changing range of specific conductivity in species was Cotinus coggygria> Sophora japonica > Salix matsudana> Buxus sinica, ie ring-porous species was higher than diffuse-porous. The monthly degree of xylem embolism was ring-porous species> diffuse-porous> conifers. The seasonal variation of xylem embolism in hardwood trees was autumn lower than summer, the lowest xylem embolism was occurred in autumn, whose precipitation was the most.