Chin J Plant Ecol ›› 2010, Vol. 34 ›› Issue (2): 170-178.DOI: 10.3773/j.issn.1005-264x.2010.02.008

Special Issue: 稳定同位素生态学 碳水能量通量

• Special feature: Stable isotope ecology • Previous Articles     Next Articles

Partitioning wheat field evapotranspiration using Keeling Plot method and continuous atmospheric vapor δ18O data

YUAN Guo-Fu1,*(), ZHANG Na1,2, SUN Xiao-Min1, WEN Xue-Fa1, Zhang Shi-Chun1,2   

  1. 1Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2008-12-15 Accepted:2009-07-15 Online:2010-12-15 Published:2010-02-01
  • Contact: YUAN Guo-Fu

Abstract:

Aims Stable isotopes technique and Keeling Plot relationship offer great promise for partitioning evapotranspiration (ET), which can help us better understand the hydrologic cycle within terrestrial ecosystems. Our objectives are to evaluate the Keeling Plot method in ET partitioning using in situ continuous δ18O data and find the fractional contribution of crop transpiration to total ET in a winter wheat (Triticum aestivum) field.

Methods Field experiments were conducted at Luancheng Agro-ecology Station, Chinese Academy of Sciences. A hydrogen and oxygen isotopes in situ measurement system based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) was used to obtain the continuous atmospheric vapor δ18O data. Other measurements were made with the eddy covariance technique, cryogenic vacuum distillation and stable isotope ratio mass spectrometry.

Important findings An analysis on the Keeling Plot relationships based on data from different time intervals in one daytime showed that the Keeling Plot would be better when using the midday time interval data to build Keeling Plot, which inferred that the plant transpiration isotopic steady-state (ISS) can be more easily obtained during midday when plant transpiration flux is generally largest. ISS was not always satisfied in field conditions, especially when mature wheat suffered from water stress. Using isotopic partitioning, we estimated transpiration contributed roughly 94%-99% to the total ET during the field measurement period, which indicated plant transpiration dominated local ET.

Key words: flux partitioning, Keeling Plot, stable isotopes, TDLAS