不同程度的水分胁迫对沙棘幼苗生理生态特征的影响

为探讨未来降水减少对内蒙古皇甫川流域沙棘幼苗生理生态特征的影响，特设计平均降雨水平、偏旱、干旱和极端干旱4种不同的水分梯度处理，开展人工水分梯度实验。方差分析表明，不同的水分梯度显著影响土壤的含水量、土壤温度等微生境因子，并显著影响净光合速率、气孔导度、蒸腾速率等气体交换特征、资源利用效率和叶片水势特征。适度的水分胁迫(干旱环境)能够提高沙棘的水分利用效率，同时却降低净光合速率和蒸腾速率。各种生理生态指标表明，4种水分处理的沙棘幼苗都受到不同程度的水分胁迫的影响，极端干旱环境中沙棘幼苗的内在生理调节机制出现紊乱，皇甫川流域沙棘不适宜在极端干旱环境中生长。

Effects of Different Water Stresses on Eco-physiological Characteristics of Hippophae rhamnoides Seedlings

In order to examine the effects of the decrease of future precipitation on the eco-physiologi-cal characteristics of sea buckthorn (Hippophae rhamnoides Linn.) in Huangfuchuan Watershed in NeiMongol, a water gradient experiment was conducted based on the four specially designed water supplylevels, including normal precipitation, slight drought, drought and extreme drought. Results of ANOVEshowed that different water gradients had a significant effect on (1) microhabitat factors, such as soilwater content and soil temperature; (2) gas exchange, such as net photosynthetic rate, stomatal conduc-tance and transpiration rate; (3) resource use efficiency; and (4) leaf water potential. Water use efficiencyof H. rhamnoides could increase under moderate water stress, i.e. drought condition, while its net photo-synthetic rate and transpiration rate decreased. All kinds of eco-physiological characteristics proved H.rhamnoides seedlings under all water supplies were affected by water stress more or less and that mecha-nism of intrinsic physiological regulation in seedlings under the extreme drought conditions had the ap-pearance of turbulence to a certain extent. Therefore, H. rhamnoides seedlings in Huangfuchuan Water-shed could not acclimate to extreme drought conditions.