Next Article in Journal
Nitrogen Application Improved Photosynthetic Productivity, Chlorophyll Fluorescence, Yield and Yield Components of Two Oat Genotypes under Saline Conditions
Previous Article in Journal
Nitrogen Utilization in a Cereal-Legume Rotation Managed with Sustainable Agricultural Practices
Previous Article in Special Issue
Using Neural Networks to Estimate Site-Specific Crop Evapotranspiration with Low-Cost Sensors
Article Menu
Issue 3 (March) cover image

Export Article

Open AccessArticle
Agronomy 2019, 9(3), 114; https://doi.org/10.3390/agronomy9030114

Radiometric Method for Determining Canopy Stomatal Conductance in Controlled Environments

1
AECOM, Air Revitalization Lab, Mail code: LASSO-008, Kennedy Space Center, Merritt Island, FL 32899, USA
2
Plants, Soils and Biometeorology Department, Utah State University, Logan, UT 84322, USA
*
Author to whom correspondence should be addressed.
Received: 1 January 2019 / Revised: 19 February 2019 / Accepted: 20 February 2019 / Published: 27 February 2019
(This article belongs to the Special Issue Crop Evapotranspiration)
  |  
PDF [4483 KB, uploaded 27 February 2019]
  |     |  

Abstract

Canopy stomatal conductance is a key physiological factor controlling transpiration from plant canopies, but it is extremely difficult to determine in field environments. The objective of this study was to develop a radiometric method for calculating canopy stomatal conductance for two plant species—wheat and soybean from direct measurements of bulk surface conductance to water vapor and the canopy aerodynamic conductance in controlled-environment chambers. The chamber provides constant net radiation, temperature, humidity, and ventilation rate to the plant canopy. In this method, stepwise changes in chamber CO2 alter canopy temperature, latent heat, and sensible heat fluxes simultaneously. Sensible heat and the radiometric canopy-to-air temperature difference are computed from direct measurements of net radiation, canopy transpiration, photosynthesis, radiometric temperature, and air temperature. The canopy aerodynamic conductance to the transfer of water vapor is then determined from a plot of sensible heat versus radiometric canopy-to-air temperature difference. Finally, canopy stomatal conductance is calculated from canopy surface and aerodynamic conductances. The canopy aerodynamic conductance was 5.5 mol m−2 s−1 in wheat and 2.5 mol m−2 s−1 in soybean canopies. At 400 umol mol−1 of CO2 and 86 kPa atmospheric pressure, canopy stomatal conductances were 2.1 mol m−2 s−1 for wheat and 1.1 mol m−2 s−1 for soybean, comparable to canopy stomatal conductances reported in field studies. This method measures canopy aerodynamic conductance in controlled-environment chambers where the log-wind profile approximation does not apply and provides an improved technique for measuring canopy-level responses of canopy stomatal conductance and the decoupling coefficient. The method was used to determine the response of canopy stomatal conductance to increased CO2 concentration and to determine the sensitivity of canopy transpiration to changes in canopy stomatal conductance. These responses are useful for improving the prediction of ecosystem-level water fluxes in response to climatic variables. View Full-Text
Keywords: canopy stomatal conductance; aerodynamic conductance; elevated CO2; climate change canopy stomatal conductance; aerodynamic conductance; elevated CO2; climate change
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Monje, O.; Bugbee, B. Radiometric Method for Determining Canopy Stomatal Conductance in Controlled Environments. Agronomy 2019, 9, 114.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Agronomy EISSN 2073-4395 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top