Water Use Strategy of Four Desert Shrubs in Gonghe Basin, Qinghai-Tibetan Plateau

Gonghe basin is located in the ecotone from the semi-arid to arid zone on the northeastern Qinghai-Tibetan Plateau. Caragana intermedia and Caragana korshinskii are dominant on sand dunes. Salix psammophila and Salix cheilophila are mainly distributed on interdune. Water source of four desert shrubs was examined by δD and δ18O, and their long-term water use efficiency (WUE) was compared by leaf δ13C. Four desert shrubs used different depths of soil water depending on their availability in different seasons, including shallow soil water recharged by rain in spring or summer and deep soil water recharged by ground water. The reliability on ground water of two Salix shrubs on interdune was more significant than two Caragana shrubs on sand dunes. Moreover, the WUE of four shrubs decreased in drought spring. Two shrubs in Caragana had similar WUE in the growing season. However, the WUE of S. psammophila was always higher than that of S. cheilophila, which might have more adaptability in Gonghe Basin.