植物水分来源稳定氢氧同位素偏移研究进展

A review of stable hydrogen and oxygen isotopic offset in plant water source research

稳定氢氧同位素技术能有效计算植物根系水分吸收量,确定植物水分来源贡献,评估植物水分利用策略,是生态水文学探究大气-植被-土壤系统水分传输过程机制的有效工具。然而土壤与木质部水稳定氢氧同位素比值(δ^(2)H和δ^(18)O)偏移造成植物水分来源贡献率计算偏差,引起氢氧同位素结果差异的原因尚不明晰。该文首先简要介绍氢氧稳定同位素比值偏移现象,其次沿水分在土壤-植物-大气连续体中的传输路径构建梳理框架,系统阐述了3个界面(植物-大气界面、土壤-大气界面和根系-土壤界面)与2个空间(植物体和土壤层)中引起δ^(2)H与δ^(18)O偏移的自然效应,同时概述了土壤与木质部样品提取与测定技术中引起δ^(2)H与δ^(18)O偏差的人为效应。最后,根据现有研究进展提出主要问题,从获取同位素时空数据,微尺度同位素偏移原因,提取与测定技术的优化三方面指出未来的发展方向。

Stable hydrogen and oxygen isotope analysis provides an important tool for calculating plant root water uptake amount,determining the contribution to plant water source,and evaluating plant water use strategy,and is thus of great relevance to ecohydrological studies with respect to exploration of the water transmission mechanism of the atmosphere-vegetation-soil system.However,the stable hydrogen and oxygen isotope ratios(δ^(2)H andδ^(18)O)offset between soil and xylem water can cause inconsistency in the calculated contribution rate of plant water source,but the reasons for differences in hydrogen and oxygen isotope results are unclear.In this review,we first briefly introduced the phenomenon of hydrogen-oxygen stable isotope ratio offset;secondly,the framework was constructed along the water transport path of the soil-plant-atmosphere continuum.We systematically expounded the natural effects ofδ^(2)H andδ^(18)O offset in three interfaces(plant-atmosphere interface,soil-atmosphere interface,and root-soil interface)and two spaces(plant and soil layer).At the same time,we summarized the methodological artifacts that are associated with soil and xylem sample extraction andδ^(2)H andδ^(18)O determination technologies.Finally,we identify main knowledge uncertainties according to the existing research progress;and highlight three areas that deserve future research attention:the acquisition of isotope spatiotemporal data,the cause of micro-scale isotope offset,and the optimization of extraction and determination technology.