Abstract
Canopy transpiration is a major factor determining crop evapotranspiration and energy budgets. Unfortunately the development of robust models of canopy transpiration is hindered by a lack of reliable data due to the difficulties of making canopy-scale measurements. However, measurements of canopy water vapor and carbon fluxes via gas exchange techniques are possible in controlled environments. Simultaneous measurements of transpiration, photosynthesis, and canopy temperature were made in wheat and soybean communities. These data were used to calculate chamber aerodynamic and canopy stomata! conductances, and to model the response of canopy transpiration to CO2concentration and vapor pressure deficit. Canopy stomata! conductance was found to decrease diurnally by 20-30% in well-watered crops grown under constant environmental conditions. The magnitude of this diurnal decrease in the canopy stomata! conductance of wheat and soybean decreased with increasing ambient CO2 concentrations. Eight models describing how canopy stomatal conductance responds to environmental changes were incorporated into a canopy transpiration model. The results and methods developed in this study will allow future physiologically-based canopy transpiration models to incorporate these models for predicting the response of transpiration rates in controlled environments.
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Claims 3
Claim · model-written summary
Canopy stomatal conductance decreased by 20-30% diurnally in well-watered crops under constant conditions.
- Taxon
- wheat and soybean
Glycine max
Triticum aestivume1 - Outcome
- Canopy stomata! conductancee0
- Direction
- decreasee0
- Value
- 20-30%e0
- Qualifier
- constant environmental conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“were made in wheat and soybean communities”
e0“Canopy stomata! conductance was found to decrease diurnally by 20-30% in well-watered crops grown under constant environmental conditions”
Claim · model-written summary
The diurnal decrease in canopy stomatal conductance of wheat and soybean was smaller with increasing ambient CO2.
- Taxon
- wheat and soybeanGlycine maxTriticum aestivume2
- Treatment
- increasing ambient CO2 concentrationse2
- Outcome
- diurnal decreasee2
- Direction
- decreasede2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“The magnitude of this diurnal decrease in the canopy stomata! conductance of wheat and soybean decreased with increasing ambient CO2 concentrations”
Claim · model-written summary
Eight models of canopy stomatal conductance response to environment were incorporated into a canopy transpiration model.
- Taxon
- wheat and soybeanGlycine maxTriticum aestivume1
- Outcome
- canopy stomatal conductance respondse3
- Value
- Eight modelse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“were made in wheat and soybean communities”
e3“Eight models describing how canopy stomatal conductance responds to environmental changes were incorporated into a canopy transpiration model”