Based on the stable isotope method

The water use patterns and strategies of Populus euphratica and Tamarix ramosissima at different ages were studied in Tarim River Basin. The results showed that: (1) precipitation offset of plant and soil water were significantly different from the offsets of groundwater

indicating that there were two?inhomogeneous and incompletely mixed water reservoirs that supply either for the plant water fluxes or the fluxes of groundwater. (2) The δ18O value of surface soil water fluctuated widely

which was affected by evaporation

and the δ18O value of soil water decreased gradually with the increasing soil depth. (3) The water used by the Populus euphratica and Tamarix ramosissima with different ages came from different sources. The deeper soil water could be accessed after the ages increased. There might be water competition at the mature age of Populus euphratica and seedling age of Tamarix ramosissima. Whether seedling or mature

Tamarix ramosissima could use deeper water than Populus euphratica

and therefore

be more adaptable to the arid environment.