准噶尔盆地东南缘多枝柽柳、白刺和红砂水分来源的异同

荒漠生态系统中, 水是植物生长最主要的限制因子。为了比较同一生境下不同荒漠植物的水分来源特征, 选取了同一生境下的多枝柽柳(Tamarix ramosissima)、白刺(Nitraria sibirica)和红砂(Reaumuria soongorica), 测定了这3种植物茎水和各潜在水源(降水、土壤水和地下水)的氢、氧稳定同位素比率(δD和δ¹⁸O)值, 并利用IsoSource软件计算了3种植物对潜在水源的利用比例。结果表明: 红砂和白刺的茎水δD和δ¹⁸O值及其水分来源有明显的季节波动特征。其中, 红砂为浅根系植物, 春季(3-5月)以表层土壤水为主要水源, 夏秋季节(6-10月)表层土壤含水量显著降低, 其主要的水分来源逐渐偏向于较深层的土壤水; 白刺的根系分布范围介于红砂和多枝柽柳之间, 在春季能够较多地利用表层土壤水, 而到了夏秋季节, 所利用的水分更多地来源于深层土壤水或地下水; 多枝柽柳为深根系植物, 其90%以上的水分来源于深层土壤水和地下水, 而且茎水δD和δ¹⁸O值及其水分来源没有季节波动特征。3种植物水分来源特征的差异与其水分利用策略密切相关, 同时, 也说明荒漠灌木可以通过自身调节向着最优(最有利)表现型发展, 从而最大限度地获取水分。

Differences and similarities between water sources of Tamarix ramosissima, Nitraria sibirica and Reaumuria soongorica in the southeastern Junggar Basin

Aims Water is the most important limiting factor for plant growth in desert ecosystems. Our objective was to investigate the water sources of three co-existing desert plants and illustrate seasonal variation characteristics in southeastern Junggar Desert in China.
Methods We investigated three kinds of desert plants (Tamarix ramosissima, Nitraria sibirica and Reaumuria soongorica) in the same habitat and measured hydrogen and oxygen stable isotope ratio (δD and δ¹⁸O) values of their xylem water and potential water sources (precipitation, soil moisture and ground water). The IsoSource model was then used to calculate probable contributions of potential water sources to total plant water uptake.
Important findings The water sources of the three desert plants had obvious seasonal characteristics. Reaumuria soongorica and N. tangutorum obtained a high proportion of water from shallow soil water (0-100 cm) in spring. However, during the summer and autumn, R. soongorica tended to use deeper soil water, and N. tangutorum tended to use ground water. Tamarix ramosissima obtained 90% of its water from deep soil water and ground water, and there were no seasonal variations. The three kinds of plants had different water sources closely related to their water use strategies. This shows desert shrubs, through self-regulation, could tend to their optimal phenotypes and maximize water uptake.