Abstract:

In Ulanbuh desert, Artemisia ordosica, Ammopiptanthus mongolicus, Nitraria tangutorum, Caragana korshinskii and Haloxylon ammodendron are five dominant shrubs. In October 2007 (late autumn) and June (early summer) 2008, a stable isotope technique was used to measure the δD value of water in rain, well, irrigation ditch, branch and different soil horizons of these five shrubs, and then the main water source in the plants in different seasons was analyzed. Also, the δ¹³C value of their leaves (or assimilating shoot) was measured and the water use efficiency of four C₃ plants was analyzed. The results indicated N. tangutorum used the water in 30-60 cm soil in early summer and late autumn whereas other four shrubs extracted water from different soil horizons in two different seasons. The long term water use efficiency of N. tangutorum was significantly higher in early summer than in late autumn (P<0.05). Water use efficiency of A. ordosica, A. mongolicus and C. korshinskii was relatively stable in the two different seasons. Water use efficiency of A. mongolicus, N. tangutorum and C. korshinskii was higher than A. ordosica.

Key words: selective use of soil water, water use efficiency, stable isotope, Ulanbuh desert, shrub