Abstract:Water is the main limiting factor for plant growth in the waterwind erosion area of the Loess Plateau. Liudaogou watershed was taken as a study area in consideration of its typical representative of the Loess Plateau. Caragana korshinskii and Salix psammophila, two kinds of typical shrubs, were chosen as the objects of the study to measure the δD of their stem water and soil water in different soil depths and δ13C of the leaves. And the IsoSource model was used to calculate the probable contributions of soil water to these two shrubs. In addition, the leaf water potential, stomatal conductance, photosynthetic rate and transpiration rate were measured to compare the different water sources and ecophysiological adaption of the two shrubs in different seasons. The results showed that: (1) the water use strategies of C. korshinskii and S. psammophila changed with seasonal fluctuations, and the soil moisture utilization ratio of different depths in different seasons were significantly different. (2) In the dry season, C. korshinskii and S. psammophila mainly used the water from 40-80 cm layer, and the ratio was 48.1% and 49% respectively. (3) In the wet season, C. korshinskii used more than 57.5% water from the surface soil layer (0-10 cm) and shallow layer (10-40 cm), while S. psammophila used more than 76% water from shallow layer (10-40 cm). (4) The soil water deficit of the two shrubs were serious in the dry season, and the leaf water potential, stomatal conductance, photosynthetic rate and transpiration rate were less than those in the wet season. It indicates that the C. korshinskii and S. psammophila can obtain higher carbon assimilation rate by reducing stomatal conductance to decrease water loss. And they can maintain higher water use efficient to adapt the arid condition.