胡杨异形叶沿树冠垂直空间分布规律研究
Study on the Vertical Spatial Distribution of the Heteromorphic Leaves along the Canopy of Populus euphratica

为探究胡杨异形叶随树冠高度变化的空间分布规律，以甘肃河西走廊金塔县的人工胡杨林植株为研究对象，调查树冠不同分层间胡杨各异形叶出现频率。结果表明：条形叶与披针形叶频率在树冠底部最高，锯齿卵形叶出现频率在树冠中部达到最大，锯齿阔卵形叶与锯齿扇形叶多出现于树冠上部。其中，条形叶频率、锯齿卵形叶频率与锯齿扇形叶频率在树冠各分层间叶形存在显著差异。随着树冠高度的增加，条形叶出现频率逐渐减少，披针形叶出现频率无明显变化，而锯齿卵形叶、锯齿阔卵形叶和锯齿扇形叶的出现频率逐渐增大；各异形叶在树冠垂直空间分布上表现出一定的消长规律。本研究结果揭示了胡杨异形叶在树冠层的分布规律，有助于深入了解胡杨异形叶对生存环境的适应性变化。
In order to explore the vertical spatial distribution law of the heteromorphic leaves in the canopy of Populus euphratica, the occurrence frequencies of heteromorphic leaves among different layers of the canopy were investigated by taking the artificial P. euphratica forest in Jinta County. The results showed that the frequencies of linear and lanceolate leaves were the highest at the bottom of the crown, the frequency of dentate ovate leaves was the highest in the middle of the crown, and the frequency of dentate broad-ovate leaves and dentate fan-shaped leaves was the highest in the upper part of the crown. Among heteromorphic leaves, the frequencies of linear leaves, dentate ovate leaves and dentate fan-shaped leaves were significantly different among the tree crown layers. The different heteromorphic leaves showed different trends with the increasing the tree crown height, the frequency of linear leaves gradually decreased, the frequencies of dentate ovate leaves, dentate broad-ovate leaves and dentate fan-shaped leaves significantly increased, while the frequency of lanceolate leaves were not significant changes. The relationships of each frequency of heteromorphic leaves in the vertical spatial distribution in the canopy showed a trade-off pattern. These results reveal the distribution pattern of heteromorphic leaves in the canopy layer of P. euphratica, which helps to understand the adaptive changes of heteromorphic leaf distribution to the survival environment.