GEOPHYSICAL FACTORS AFFECTING PLANT PRODUCTIVITY
MISSOURI BOTANICAL GARDEN ST LOUIS
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A model for productivity is presented. It combines a model for photosynthesis with an energy budget approach to leaf energy balance. The photosynthesis model describes the rate of photosynthesis of a leaf as a function of leaf temperature, diffusive resistance to CO2 and biochemical reaction rate using the Michaelis-Menton equation. The energy budget approach describes the temperature of a leaf as determined by air temperature incident radiation, wind speed, relative humidity, diffusive resistance to water vapor, leaf size, leaf orientation, and leaf spectral characteristics. When the photosynthesis and energy budget approaches are combined, photosynthetic rate and rate of water loss, transpiration, can be calculated as functions of any combination of the above variables wind speed, air temperature, etc. A number of graphs of this ratio as it varies with several important geophysical factors are given along with comments as to the significance of the relationships.