7种造林树种木质部栓塞脆弱性研究

Study on vulnerability of xylem embolism in twigs of seven tree species

以中国北方地区7种造林树种刺槐Robiniapseudoacacia,杜梨Pyrusbetulaefolia,麻栎Quercusacutissima,苦楝Meliaazedarach,银杏Ginkgobiloba,黄连木Pistaciachinensis和元宝枫Acermono为研究对象,于秋季测定1年生枝条水势变化及其对木质部导水性和栓塞的影响,并绘制出各树种的枝条脆弱性曲线。研究发现:①利用冲洗法获得的7种被测树种苦楝、麻栎、杜梨、刺槐、元宝枫、黄连木、银杏的枝条木质部最大导水率依次为0 0543,0 0362,0 0220,0 0184,0 0141,0 0133,0 0110g·cm-2·s-1。②枝条水势与栓塞程度相关显著,随着枝条水势的下降,被测树种枝条木质部栓塞程度加重。③以导水率损失50%对应的枝条水势为临界值评价各树种栓塞脆弱性,苦楝、黄连木最大栓塞脆弱性最大,其次为刺槐和麻栎,银杏、杜梨和元宝枫3种树种栓塞脆弱性最小。④当水势下降到一定程度后,各树种相继出现极限导水率,其中麻栎、刺槐、黄连木和苦楝4种树种最大导水率损失高达94%～96%,银杏和杜梨90%左右,元宝枫仅为78%。⑤多数被测树种栓塞脆弱性拟合曲线为倒数形式,苦楝和麻栎为指数形式。拟合方程均为极显著。

The xylem embolism and moisture potential of one-year-old twigs of 7 tree species including Robina pseudoacacia,Pyrus betulaefolia,Quercus acutissima,Melia azedarach,Ginkgo biloba,Pistacia chinensis and Acer mono in the north of China were studied with the 'flushing method'in autumn.Embolism vulnerability curves of all 7 species were drawn.The results were as follows:(1)Maximum twig water conductivity of 7 tree species were 0.054 3,0.036 2,0.022 0,0.018 4,0.014 1,0.013 3 and 0.011 0 g·cm^(-2)·s^(-1);(2)Branch moisture potential had a magnificent affect on xylem embolism.With the decrease in moisture potential,the xylem embolism became serious;(3)Taking 50% hydraulic conductance loss as the critical value of the embolism vnlnerability,we found out that M.*'azedarach and P.*'chinensis were of the most embolism vulnerabiliy;and R.*'pseudoacacia and Q.*'acutissima came in second;the other three species were of least embolism vulnerability;(4)When the twig moisture potentials descend to -4.5,-3.8,-4.2,-3.6,-4.7,-4.5 and -4.3 MPa respectively,the maximum hydraulic conductivities of Q.*'acutissima,R.*'pseudoacacia and M.*'azedarach were about 94%～96%,G.*'biloba and P.*'betulaefolia about 99%,and P.*'chinensis only 78%;(5)The embolism vulnerability curves of most species under test were in reciprocal forms;those of R.*'pseudoacacia and M.*'azedarach were in index forms.They all had significantly fitting formulas.