哀牢山滇南山杨幼苗生境选择特征1）

为探究哀牢山滇南山杨（ Populus rotundifolia）幼苗的生境选择特征，对其幼苗进行了移栽试验，移栽后的幼苗置于人工遮阴生境中，对其相关的生长参数和气体交换参数进行了测定。结果表明：滇南山杨幼苗生长参数和气体交换参数均随光照强度增加而增大，而比叶面积则随着光照强度增大而减小。可见，光照强度是影响植物生长的重要环境因子，在一定光照强度范围内，幼苗生长都随光照的增强逐渐加快。在1层和2层遮阴网条件下，与其它水分条件相比，土壤含水量为20％（极端干旱）时，滇南山杨幼苗的生长参数均表现出较高水平，说明不耐阴的树种滇南山杨对水分变化不敏感，而且有较高的耐旱性。

Habitat Preference Characteristics of Populus rotundifolia Seedlings in the Ailao Mountains

Seedlings of Populus rotundifolia were transplanted to different environmental conditions for observing their habitat preference.A couple of parameters of seedling early growth and gas exchange were measured in the artificial shading condi-tions outside of the forest.The parameters of seedling early growth and gas exchange of Populus rotundifolia showed a posi-tive correlation with the increase of light intensity, while their specific leaf area (SLA) decreased.Visible, light intensity was one of the important environmental factor affecting plant growth, and seedling growth was enhanced with the light grad-ually accelerated in a certain light intensity.P.rotundifolia seedlings performed better at 20% soil moisture ( drought stress) at 28.36% and 8.10% light levels; therefore, P.rotundifolia seedlings might be more drought-tolerant.