中文摘要：

通过野外调查和室内分析,研究胡杨叶形随个体生长发育阶段的变化规律及其与叶片养分间的关系。结果表明：胡杨个体叶形指数（叶片长/宽）与胸径、树高和叶面积均呈极显著负相关（P〈0.01）;不同发育阶段的胡杨均表现出叶形指数随树冠层次增高而减小的趋势,同一个体树冠不同层次的小枝也均表现为叶形指数随小枝节位数增加而减小。胡杨个体叶片全N、全P和有机C含量与树高和胸径呈正相关,全K含量与树高和胸径呈极显著负相关（P〈0.01）;叶形指数与叶片全P含量呈显著负相关（P〈0.05）,而与全K含量呈极显著正相关（P〈0.01）。说明胡杨叶形指数的变化不仅存在于个体发育的不同阶段,同时存在于同一个体树冠的不同层次以及当年生枝条的不同节位,而叶片全N、全P、全K和有机C含量的变化存在于个体发育的不同阶段。随着胸径增加,叶片叶形指数减小、叶面积增加,伴随着叶片全P、全K含量增加。

英文摘要：

Through field observation and laboratory analysis,this study investigated the leaf growing pattern in Populus euphratica and its relationship with developmental stages and leaf nutrient contents. The results showed that the individual leaf index（ leaf length /width ratio） had a significant negative correlation（ P〈0. 01） with DBH（ diameter at breast height）,tree height and leaf area. Leaf shape index decreased with the increase of canopy level at all development stages,and decreased with the increase of number of minor branch nodes at different canopy levels of the same individuals. The total N,P and organic C contents of individual leaf were positively correlated with tree height and DBH; total K content had a significant negative correlation with tree height and DBH（ P〈0. 01）; leaf index had a significant negative correlation with the total P content（ P〈0. 05） and a significant positive correlation with the total K content（ P〈0.01）. These results suggested that leaf index in P. euphratica changed not only at different developmental stages,but also at different levels of the same canopy and at different nodes of the branches. Total N,P,K and organic C contents of the leaves mainly changed at different developmental stages. With the increase of DBH,leaf index decrease and leaf area increase,the total P,K contents of the leaves have an increase trend.