植物生态学报 ›› 2008, Vol. 32 ›› Issue (4): 961-966.doi: 10.3773/j.issn.1005-264x.2008.04.026

所属专题: 稳定同位素生态学

• 论文 • 上一篇    下一篇

叶片水H218O富集的研究进展

温学发; 张世春; 孙晓敏; 于贵瑞   

  1. (中国科学院地理科学与资源研究所生态系统网络观测与模拟重点实验室,北京 100101)
  • 出版日期:2008-07-30 发布日期:2008-07-30
  • 通讯作者: 温学发

RECENT ADVANCES IN H218O ENRICHMENT IN LEAF WATER

WEN Xue-Fa; ZHANG Shi-Chun;SUN Xiao-Min; YU Gui-Rui   

  1. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
  • Online:2008-07-30 Published:2008-07-30
  • Contact: WEN Xue-Fa

摘要: 植物叶片水H218O富集对大气中O2和CO218O收支有着重要影响。蒸腾作用使植物叶片水H218O富集, 而植物叶片水H218O富集的程度主
要受大气水汽δ18O和植物蒸腾水汽δ18O的影响。过去, 通过引入稳态假设(蒸腾δ18O等于茎水δ18O)得到Craig-Gordon模型的闭合形式, 或
将植物整个叶片水δ18O经过Péclet效应校正后得到植物叶片水δ18O的富集程度。然而, 在几分钟到几小时的短时间尺度上, 植物叶片蒸腾
δ18O是变化的, 稳态假设是无法满足的。最近成功地实现了对大气水汽δ18O和δD的原位连续观测, 观测精度(小时尺度)可达到甚至优于稳定
同位素质谱仪的观测精度。在非破坏性条件下, 高时间分辨率和连续的大气水汽δ18O和蒸腾δ18O的动态观测, 将提高植物叶片水H218O富集的
预测能力。该文综述了植物叶片水H218O富集的理论研究的新进展、研究焦点和观测方法所存在的问题, 旨在进一步加深理解植物叶片水H218O
富集的过程及其机制。

Abstract:
There is considerable interest in the use of atmospheric C18O16O and 18O16O as a tracer for resolving the role of
the terrestrial biosphere in the global carbon cycle. Leaf transpiration will result in the enrichment of the heavy H218O
isotopes. The δ18O of leaf water at the evaporating site in the stomatal cavity directly influences the C18O16O and 18O16O
exchanges, instead of that of the bulk leaf water. How to best quantify this enrichment effect remains an active area of
research. In the past, a closed form of the Craig-Gordon model was obtained by invoking the steady-state assumption (δ18O of
the transpired water is identical to δ18O of the xylem water). For the purpose of verification, the predictions of Craig-
Gordon model are compared with δ18O of the bulk leaf water after appropriate corrections for the Péclet effect. On small
time scales of minutes to hours, δ18O of the transpired water is variable in field conditions, implying that the steady
state assumption is invalid. Recently, in-situ δ18O and δD measurement technology has been developed that has potential for
improving our understanding of isotopic exchanges between the Earth’s surface and the atmosphere. The precision of hourly δ
18O and δD is comparable to the precision of mass spectrometry. It has the potential to improve prediction of δ18O of leaf
water at the evaporating site within the stomatal cavity for the temporal dynamics of atmospheric water vapor δ18O and the
δ18O of the transpired water, especially if its measurement is made in a non-destructive manner and on a continuous basis.
Because the isotopic flux of δ18O and δD is influenced by a similar set of biological and meteorological variables,
simultaneous observations of δ18O and δD will provide additional constraints on the hydrological and ecological processes
of the ecosystem. We review the theory and measurement techniques for the enrichment of H218O in leaves and focus on the
recently developed in-situ measurement technology and its potential for improving our understanding of H218O enrichment in
leaf water and C18O16O and 18O16O exchanges between the ecosystem and atmosphere.