针对不同林分密度对树冠结构的影响以及不同密度条件下杨树树冠结构与溃疡病的关系进行 了分析。结果表明：不同密度条件下的杨树一级分枝粗度和冠层密度存在极显著差异。病情指数与 密度呈显著正相关(0.631)，与冠形率呈显著负相关(-0.540)。通径分析结果表明，各树冠结构指标 对病情指数的综合作用均为负，从大到小依次为：冠幅、单株总叶面积、冠长树高比、叶面积指数 、枝下高、树冠表面积、冠层密度、一级分枝粗度、冠形率、一级分枝角度。其中以冠幅和单株总 叶面积的综合负向作用最大。因此，杨树溃疡病密度调控的树冠结构指标选择应着眼于冠幅和单株 总叶面积。在调查的5个林分中，株行距为2.0 m×3.0 m的林分密度最为合理，林中溃疡病病情最轻 。

The effect of different stand density to poplar crown structure and the relation between crown structure and poplar canker under different density were analyzed.The results showed that the difference of the firstorder branch diameter and canopy layer density was significant among 15 plots. Disease index was significant positive correlated with stand density(0.631) and significantly negatively correlated with crown shape ratio(-0.540). Besides, the results of path analysis showed that the general effect of all of crown structure indexes were negative, and their order was crown width, total leaf area, percentage of crown length with height, leaf area index, height under branch, crown surface area, canopy layer density, firstorder branch diameter, crown shape ratio and firstorder branch angle. The negative general effect of total leaf area and crown width was the largest. Accordingly，the choice of crown structure indexes of densitycontrol of poplar canker should emphasize crown width and total leaf area. Density (planting spacing was 2.0 m×3.0 m) of the first stand among 5 stands was optimum, and disease state of poplar canker was the lowest.