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Development and Evaluation of Simplified Models for Simulating Canopy Photosynthesis and Transpiration

T. R. Sinclair, C. E. Murphy and K. R. Knoerr
Journal of Applied Ecology
Vol. 13, No. 3 (Dec., 1976), pp. 813-829
DOI: 10.2307/2402257
Stable URL: http://www.jstor.org/stable/2402257
Page Count: 17
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Development and Evaluation of Simplified Models for Simulating Canopy Photosynthesis and Transpiration
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Abstract

(1) Comparisons were made of three micrometeorological models which simulated daily rates of the photosynthesis and transpiration in a maize crop. (2) The most complex model, a complete soil-plant-atmosphere model (SPAM), simulated the wind speed, CO2 concentration, atmospheric water vapour content, air and leaf temperatures, and radiation distribution in canopies. The model predicted that transpiration rates of maize were highly dependent on air temperature and mildly dependent on the atmospheric water vapour content, but only on wind speed when air temperature was high. Predicted CO2 assimilation rates were strongly dependent on air temperature, as a consequence of the simulated sensitivity of respiration to temperature, but not on water vapour and wind speed. (3) A simplified model assumed that there were no vertical gradients of air temperature, water vapour and CO2 concentrations above and within the maize canopy. This model produced predictions of CO2 assimilation within 12% of the complete model (SPAM), but predictions of transpiration agreed only under conditions that resulted in low transpiration rates; the difference could be as great as 40%, because the moderating effect of the aerodynamic resistance had been ignored.

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