[Water use strategy of Tamarix chinensis during a drought year in the coastal wetlands of the Yellow River Delta, China].

Tamarix chinensis, the dominant species of plant communities in the coastal wetlands of the Yellow River Delta, was selected to study the water use strategy of coastal plants at different habitats during a drought year. The Δ18O values for xylem water of T. chinensis were analyzed. Potential contributions by different water sources to T. chinensis were estimated using the IsoSource model. The contributions were analyzed to reveal the adaptation mechanism of T. chinensis to water stress at different habitats. The results showed that the main water sources for T. chinensis during a drought year were soil water and groundwater rather than precipitation. However, the water use strategies of T. chinensis changed significantly with different micro-topographies. For dune crests, 72.6%-95.4% water of T. chinensis came from deeper soil water (40-100 cm) and groundwater. However, near the high tide line, T. chinensis absorbed 40.7%-97.3% of the water from the upper soil (0-40 cm) to avoid the salt stress caused by sea water and shallow groundwater. This provided T. chinensis with a competitive advantage related to water consumption and improved its water use efficiency in the coastal ecosystem, which led to mono-dominant shrub community of T. chinensis in this area.