Chin J Plan Ecolo ›› 2016, Vol. 40 ›› Issue (9): 912-924.DOI: 10.17521/cjpe.2015.0431

Special Issue: 稳定同位素生态学

• Research Articles • Previous Articles     Next Articles

Leaf water δD and δ18O enrichment process and influencing factors in spring maize (Zea mays) grown in the middle reaches of Heihe River Basin

Xiao-Ting WANG1,2, Xue-Fa WEN1,*()   

  1. 1Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    and
    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2015-12-02 Accepted:2016-05-12 Online:2016-09-10 Published:2016-09-29
  • Contact: Xue-Fa WEN

Abstract:

Aims The stable isotope fractionation of plant water is an important part for the water cycle in the soil-plant-atmosphere continuum. There is a lack of control mechanisms research of leaf water isotope ratio (δl,b) enrichment based on the field conditions. Because it is tough to get the measured 18O isotope ratio (δ18O l,b) and deuterium (D) isotope ratio (δDl,b) of leaf water (collective name δl,b). Therefore most previous research focuses on model building used the limited number of δl,b. Leaf water δDl,b and δ18O l,b enrichment (collective name Δl,b) is usually represented as the difference of the leaf water isotope ratio (δl,b) and the plant source water isotope ratio (δDx and δ18O x,collective name δx), that is Δl,b = δl,b - δx.
Methods A field experiment with spring maize (Zea mays) was conducted in the middle reaches of Heihe River Basin to investigate the characteristics of leaf water δ18O and δD enrichment and their abiotic control mechanisms on seasonal and daily scales. Leaf and stem samples were collected and analyzed according to different time scales, and the δ18O and δD of atmospheric water vapor (collective name δv) were determined based on the in situ and continuous water vapor isotope ratio measurement system at the same time.
Important findings The results showed that: δl,b and Δl,b of leaf water varied little during the experimental season while largely at daily scale, which enrichment was found at the daytime but depletion at night. Atmospheric water vapor isotope ratio (δv) and relative humidity were main factors to D on both seasonal and daily scales; for 18O, only relative humidity was the key control factor on both seasonal and daily scales. Differences of D and 18O came from the equilibrium fractionation because equilibrium fractionation factor for D was over 8 times than for 18O. The analysis of these differences help us distinguish the environmental factors of leaf water enrichment for D (ΔDl,b) from leaf water enrichment for 18O (Δ18Ol,b), and improve our understanding of leaf water enrichment process and develop the related models as well.

Key words: leaf water enrichment, δD and δ18O, atmospheric water vapor, relative humidity, temperature, synergism