中文摘要：

本文用Shuttleworth-Wallace（S-W）双涌源能量守衡模型以小时为时段，模拟计算了浑善达克沙地天然杨树种群的蒸散量，并用插针式茎流计（Dynagage Probe 12^TM）测定的杨树蒸腾量和微型蒸发器测定的冠层下部土壤蒸发量值对其计算精度进行了验证。验证后的日变化分析结果显示：浑善达克沙地天然杨树蒸散量日变化进程曲线的总趋势是晴朗无雨的天气呈单峰型；在时晴、时云相间天气蒸散量日变化进程曲线呈现显著的变化过程；在太阳辐射很小的全阴或全雨天S-W模型模拟计算值精度有限，不易用它对全阴或全雨天蒸散量进行日变化进程分析。当研究目标为探求天然杨树全生育期耗水量时，建议以天为计算时段，这样既可以减少以小时为计算时段的计算工作量，也能达到计算精度。

英文摘要：

The Shuttle-Wallace （S-W） energy conservation model is applied to simulate the evaportranspiration variation of populus in Otindag sandy land region with one hour as the calculation period. The evapotranspiration estimated is verified by the measurement data obtained by Dynagage Probes and micro-lysimeters. The analysis on diurnal evaportmnspimtion shows that it tends to increase in the morning and reaches a peak value at 9 ： 00 to 12 ： 00 AM if the day is sunny, but it tends to decrease slowly afterward and reaches a minimum at night. In case the day is alternatively changing between sunny and cloudy the evapotranspiration will fluctuates obviously. The evaportranspiration of cloudy or rainy day cannot be estimated from the S-W model since remarkable error will appear due to the low solar radiation. The diurnal variations of Populus evaportmnspiration in different growing season will not be the same due to the differences of stomatal mediation. A peak value is also exists in the variation curve of soil evaporation and exhibit a variation tendency similar to that of evaportranspiration. It is suggested that using one day as the calculation period is more suitable for investigating the water assumption of Populurs since the computation time will be greatly reduced.