干旱区植物水分来源的D、18O同位素示踪研究进展

在干旱、半干旱地区,水是生态系统的主要限制因子,对植物水源的研究有助于指导干旱、半干旱地区的生态建设.在水分被根系吸收和从根系向叶片输送的过程中,其δ(D)、δ(18O)值一般不会发生变化.因此,水中天然δ(D)、δ(18O)值的分析为确定植物的水分来源提供了一种有效的途径:只要各潜在水源的稳定同位素组成具有显著差异,就可通过植物体内水的δ(D)、δ(18O)值和各潜在水源δ(D)、δ(18O)值的对比,定量确定植物对这些水源的吸收情况.但是,由于各潜在水源的不确定性和蒸发富集等因素的影响,该技术还存在一些不足.另外,隐性降水是干旱环境下植物的重要水源,但目前尚未开展隐性降水对植物补给作用的定量评价.利用稳定同位素技术定量评价干旱区植物隐性水源将是今后重要的研究方向.

Advances in the D and 18O Isotopes of Water Source of Plants in Arid Areas

This paper studies the water sources of plants in arid and semi-arid areas, the main limitation factor for the ecosystem in order to promote ecological construction. As the δ(D) and δ(18O) of the water do not change as a rule in the process of transmission from root to leaves, the isotope D, 18O technology can provide an effective way to determine the water sources of plants. So long as the stable isotope composition in the potential water sources possesses a significant difference, it is possible to determine quantitatively the water sources of plants by δ(D), δ(18O) values and comparing the δ(D), δ(18O) values. However, due to the uncertainty of the potential water sources of plants and enrichment, there are still some problems. Though occult precipitation is an important water source of plants in arid and semi-arid areas, few studies have assessed quantitatively its contribution. It is suggested that quantitative assessment of occult precipitation by using stable isotope technology should be an important future research.