Chin J Plant Ecol ›› 2012, Vol. 36 ›› Issue (5): 463-470.DOI: 10.3724/SP.J.1258.2012.00463

• Research Articles • Previous Articles    

Parameterization of water response functions in leaf stomatal conductance model for winter wheat

YUAN Guo-Fu1,*(), ZHUANG Wei1,2, LUO Yi1   

  1. 1Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Published:2012-05-04
  • Contact: YUAN Guo-Fu

Abstract:

Aims Water response functions in leaf stomatal conductance models are used to simulate the effects of water stress on stomatal conductance. Especially under a water-limited environment, the water response function is a critical method for modeling gas exchange between plant and air. Winter wheat (Triticum aestivum) is an important crop grown under water-limited environment in North China. Our objective is to determine the responses of stomatal conductance of winter wheat to vapor humidity, soil water content and leaf water potential and to determine the appropriate water response functions for winter wheat in North China based on field experiments.
Methods Field experiments were carried out at Yucheng Comprehensive Station. Eight water treatment plots were set up to produce different degrees of water stress on winter wheat. Leaf gas exchange and stomatal conductance were measured, along with other environmental and water factors. We analyzed relationships between leaf stomatal conductance and air vapor humidity, soil water content and leaf water potential.
Important findings Leaf stomatal conductance of winter wheat decreased with increasing air vapor pressure deficit (VPD). About 1 kPa in VPD is a valuable threshold value for winter wheat. When VPD is <1 kPa, leaf stomatal conductance decreases rapidly with increasing VPD. But when VPD is >1 kPa, leaf stomatal conductance decreases slightly even with a large VPD increase. A hyperbolic function can simulate the response of stomatal conductance of winter wheat to VPD. Midday leaf stomatal conductance linearly increases when soil water content increases, but the maximum threshold is about 25% of mean soil water volumetric contents, above which leaf stomatal conductance fluctuates in high conductance and does not show a simple increasing trend. A similar relationship between midday leaf stomatal conductance and soil water content occurs between midday leaf water potential and midday leaf stomatal conductance, where the maximum threshold in midday leaf water potential is about -1 MPa when the leaf stomatal conductance becomes relatively stable. We obtained the vapor humidity response function for winter wheat in hyperbolic and power exponent forms based on our field experimental data by data-fitting methods. We also obtained the soil water content response function and leaf water potential response function in simple linear form. These water response functions are useful for the application on modelling surface processes for winter wheat, especially in North China.

Key words: stomatal conductance model, Triticum aestivum, water response function