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Energy Exchange and Water Use Efficiency of Field Crops: Validation of a Simulation Model
Author(s) -
Grant R. F.,
Rochette P.,
Desjardins R. L.
Publication year - 1993
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1993.00021962008500040025x
Subject(s) - canopy , latent heat , environmental science , sensible heat , atmospheric sciences , leaf area index , soil water , agronomy , hydrology (agriculture) , soil science , ecology , meteorology , biology , geography , geology , geotechnical engineering
Crop canopies exercise some control on the exchange of mass and energy with the atmosphere by regulating their stomatal resistance. A hypothesis is proposed in which regulation of stomatal resistance is controlled jointly by the water status of the canopy and photosynthetic capacities of the leaves in the canopy. This hypothesis was incorporated into an ecosystem simulation model, which was tested against data for mass and energy exchange measured over a growing barley crop at different levels of canopy cover and soil water content. Standard differences (square root of the mean square difference) between simulated and measured hourly values for net radiation, latent heat, and sensible heat over the soil‐canopy surface were <50 W m − during each date for which comparisons were made, which is within the range of experimental error. The hypothesis allowed title model to simulate diurnal changes in canopy stomatal resistance under changing atmospheric conditions that were consistent with those estimated from flux measurement techniques. These diurnal changes allowed the model to reproduce changing relationships between latent and sensible heat fluxes measured at different canopy covers and soil water contents. The diurnal changes in simulated canopy stomatal resistance also allowed the model to reproduce diurnal changes in soil‐canopy net CO 2 exchange (SD = 3–4 μ mol m −2 s −1 ) and water use efficiency under changing atmospheric conditions and soil water status. The hypothesis for the regulation of canopy stomatal resistance is simple, and yet allows observed canopy behavior to be reproduced over a wide range of conditions.