Comparative study on the water characteristics of Populus euphratica with different depths of underground water in the foreland of Takelamakan Desert

摘要

The effect of depth to ground water on water relations of obligate phreatophyte Populus euphratica (Salicaceae) was investigated in the foreland of the hyper-arid Takelamakan Desert in Xinjiang, NW China. P. euphratica grow on sand dunes of different height (0--15.4m) above ground water that was the only water source for the species. The depth to ground water from the surface of the lowest sand dune was 6.8m under Populus. The water relation data illustrated the negative impact of sand dune height on water status of the species. Predawn and midday water potentials decreased significantly with increasing sand dune height. Water relation data suggest that decreases in hydraulic conductance with increasing distance to ground water have caused decreases in stomatal conductance due to a diminished water supply in plants on higher sand dunes. Results of this study indicate that whole-tree hydraulic conductance for Populus is heavily influenced by below ground hydraulic conductance. Whether the variations in hydraulic conductance are a function of increased path length or if they are the result of morphological changes in the conducting tissues remains further investigation. A detailed knowledge of hydraulic parameters in the root system is required to assess the effects of hydraulic limitations on plant water relations.