The Energy Budget at the Earth's Surface: Water Relations and Stomatal Response in a Corn Field.
Abstract
The study described is an attempt to separate the effects of light intensity and water stress on stomatal behavior under field conditions. A simple model has been developed as a means of systematically approaching the problem. The model is based on measurements of leaf resistance and relative water content through the day for a range of different stress conditions. The results of the model indicate that after-effects of stress must be considered and that a more complete model must include the effects of internal CO2 concentration. Testing of the changes in stomatal resistance in response to changes in leaf water relations shows how the effects of water stress can be included as a sub-model in the larger plant community model. The agreement between the energy balance measurements and the model calculations using the measured resistances strengthens the confidence in the approach. Comparison of the total flux values for the crop appears to be a good test of the model and illustrates how small differences in profiles can influence the overall exchange processes. The modeling approach has been discussed as an example of how the plant parameters and meteorological parameters can be combined in a systematic way to evaluate the plant response to a change of a large number of factors. The model can be manipulated to arrive at 'answers', but this is a dangerous procedure. The value of the exercise lies in the fact that it forces us to systematize our approach and helps to identify areas where more precise information is needed. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1971
- Accession Number
- AD0733286
Entities
People
- R. W. Shawcroft
Organizations
- Agricultural Research Service