稳定氢氧同位素定量植物水分来源的不确定性解析

稳定氢氧同位素技术被广泛运用于生态系统、特别是干旱区生态系统中植物水分来源的研究,其理论假设为"水分被植物根系吸收并向木质部运输过程中不发生氢氧同位素分馏"。生态系统中不同水源的氢氧同位素组成普遍存在显著差异,为从水源混合体中区分出各水源的贡献率提供了前提条件。但在实际应用过程中,诸多因素导致稳定氢氧同位素技术定量植物水分来源的结果具有不确定性。综合已有研究并加以分析,举证说明植物吸收水分相对于水源同位素变化的滞后性、水源同位素的季节性变化、蒸发作用和水源之间的混合作用对水源同位素的影响等导致植物水分来源定量结果不确定性的几个因素,以期为今后稳定氢氧同位素技术在植物水分来源领域的应用提供参考。

Uncertainties in the usage of stable hydrogen and oxygen isotopes for the quantification of plant water sources

Stable hydrogen and oxygen isotope analysis has been used widely to study the usage of plant water in ecosystems, especially in arid ecosystems. The theoretical basis of this analysis is that hydrogen and oxygen isotopes do not fractionate during the processes of root water absorption and water transport to the plant xylem. Dramatic differences in hydrogen and oxygen isotope ratios exist among various water sources within an ecosystem, which is a pre-condition of using stable hydrogen and oxygen isotope analysis to distinguish the proportional contributions of different water sources. However, some factors have caused uncertainty in the quantification of plant water sources using stable hydrogen and oxygen isotope analysis. This study has discussed previous research as examples of the factors leading to this uncertainty, such as the retention of root water uptake in relation to the dynamics of the isotopic ratio of water sources, the seasonal variation of isotopic water sources, and the variation of the isotopic ratio of water sources caused by evaporation and mixing of different water sources. Our research can act as a reference for future research into the quantification of plant water sources using stable hydrogen and oxygen isotopic analysis.