Water sources and water-use efficiency of desert plants in different habitats in Dunhuang, NW China

To understand habitat associated differences in desert plant water-use patterns, water stable oxygen isotope composition was used to determine water source and leaf carbon isotope composition (delta C-13) was used to estimate long-term water-use efficiency in three typical habitats (saline land, sandy land and Gobi) in Dunhuang. The primary findings are: (1) in the three habitats, plant species used mainly deep soil water (> 120 cm), except for Kalidium foliatum in the saline land, which relied primarily on 0-40 cm soil water; (2) in the saline land and Gobi habitat, Alhagi sparsifolia had the most negative foliar delta C-13; in the sandy land, Elaeagnus angustifolia leaf was enriched in C-13 than the other three species in 2011, but no species differences in foliar delta C-13 was observed among the four species in 2012; (3) common species (Tamarix ramosissima and A. sparsifolia) may alter their water sources to cope with habitat differences associated changes in soil water availability with deeper water sources were used in the Gobi habitat with lower soil water content (SWC) compared to in the saline land and sandy land; (4) we detected significant habitat differences in foliar delta C-13 in A. sparsifolia which may have resulted from differences in SWC and soil electrical conductivity. However, no habitat differences in foliar delta C-13 were observed in T. ramosissima, which may attribute to the strong genetic control in T. ramosissima or the ability to access stable deep soil water. Overall, the results suggest that extremely arid climate, root distribution and soil properties worked together to determine plant water uptake in Dunhuang area.