宁夏六盘山8种木本植被的叶片水分利用效率

为了解宁夏六盘山地区主要树种的叶片水分利用效率（WUE）的种间和水分生境差异及季节变化，2010年6-9月份在宁夏六盘山具有半湿润气候和较多树种的香水河小流域和具有半干旱气候及较少树种的叠叠沟小流域，选择8个主要树种测定其叶片的 WUE。结果表明，（1）在香水河小流域，树种叶片 WUE 大小排序为油松 Pinus tablaeformis＞山桃 Prunus davidiana＞沙棘Hippophae rhamnoides＞辽东栎Quercus liaotungensis＞华北落叶松Larix principris-rupprechtii＞华山松Pinus armandii＞少脉椴Tilia paucicostata＞白桦Betula platyphylla；在不同生活型之间，叶片WUE的大小排序基本上呈现出灌木＞小乔木＞常绿针叶树＞落叶针叶树＞落叶阔叶树的变化规律；所有8个测试树种的叶片WUE的季节变化均为生长季初期较高，在中后期持续降低，但季节变幅随树种而异。（2）对2个小流域共有的测试树种（华北落叶松、山桃和沙棘）的叶片WUE进行了比较，结果表明存在着明显的水分生境差异，即在半干旱区极显著（p＜0.01）大于半湿润区，前者为后者的2.03倍以上。（3）对于沙棘、山桃、油松和华北落叶松，它们在较干旱气候类型立地和较干旱季节条件下都具有较高的叶片WUE，属抗旱能力较强的生态型节水树种，可选为干旱缺水区主要造林树种。此外，树种叶片WUE同时具有保守性和变异性，说明可采取适度抗旱锻炼来在一定范围内提高造林树种的WUE。

Water use efficiency of eight woody species in Liupan Mountains of Ningxia,China

The water use efficiency （WUE） of leaves of 8 dominant tree species was measured from June to September in 2010 in two small watersheds （Xiangshuihe with semi-humid climate and rich tree species, Diediegou with semi-arid climate and few tree species） of Liupanshan Mountains, Ningxia, northwest China, with the objective of recognizing the difference in leaf WUE among species, moisture habitats and seasons. The results showed that the order of mean WUE among the 8 tree species measured at Xiangshuihe watershed is： Pinus Tablaeformis ＆gt; Prunus davidiana ＆gt; Hippophae rhamnoides ＆gt; Quercus liaotungersis ＆gt; Larix principis-rupprechtii＆gt;Pinus Armandii＆gt;Tilia panciostata＆gt;Betula Platyphylla. There was also a significant difference in leaf WUE among the life forms of trees, with the sequence of shrubs＆gt;small arbor＆gt;high arbor＆gt;evergreen conifers＆gt;deciduous conifers＆gt;deciduous broadleaved trees. The seasonal variation of leaf WUE of all 8 tree species was presented as decreasing with time during the growing season, however, the variation range is different among tree species. For the 3 tree species （H. rhamnoides, P. davidiana and L. principris-rupprechtii） which were measured at both watershed, their WUEs were kept always higher at the dryer site （Diediegou） than the wetter site （Xishangshuihe）, i.e. the former is at least 2.03 times of the latter, showing a very significant （P＆lt;0.01） difference between the moisture habitats. Besides the 3 tree species mentioned above, the tree species of P. tablaeformis showed also a higher WUE in drought season. Thus, it can inferred that the 4 tree species must have higher drought-resistance and water-saving property, and can be used as the main tree species for afforestation in dry regions. This study indicated that the WUE of tree species posses both conservativeness and variability with environment; implying for the forestry practice that the WUE of trees can be increased within certain range through a rational training in drought environment.