黄河三角洲海岸带湿地柽柳在干旱年份的水分利用策略

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

以黄河三角洲海岸带贝壳堤湿地灌木群落主要建群种柽柳为对象,利用稳定同位素技术测定柽柳木质部和潜在水源δ^(18)O值的时空变化,采用IsoSource模型计算潜在水源对柽柳的贡献比例,研究海岸带不同生境中柽柳对不同水分条件的适应机制.结果表明:在降水较少的干旱年份,相对于不稳定的降水,柽柳倾向于利用稳定的土壤水和浅层地下水,但是在不同微地形生境下柽柳的水分利用策略有所差异.滩脊的柽柳72.6%~95.4%水分来源于浅层地下水和含水量相对较高的深层土壤水(40~100 cm);高潮线附近的柽柳有40.7%~97.3%的水分来源于上层土壤水(0~40 cm),以避免海水和浅层地下水的盐分胁迫.柽柳对外界水盐条件变化具有较强的适应性,在海岸带可利用水资源缺乏的恶劣生境中具有更强的种间竞争优势,从而导致柽柳单优灌木群落的形成.

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. Po- tential contributions by different water sources to T. chinensis were estimated using the lsoSource 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.