Numerical Simulation of the Impact of CO_2 and Temperature Changes on Crop Canopy Photosynthesis

The leaf photosynthesis of LU-MAI 23 is measured with Licor-6200 Portable Photosynthesis Analyzer,and the curves of leaf photosynthesis response to CO_2 and radiation are determined.Based on these measurements,a leaf photosynthesis model is established,then the leaf model is scaled up to a winter wheat canopy photosynthesis model of simultaneous time scale and leaf surface spatial scale,which can simulate the canopy photosynthesis accurately.Results of the numerical simulation show that (1)on a fine day,the canopy photosynthesis increases with CO_2 enhancement,and the daily total photosynthesis will increase by 19.7% when the CO_2 concentration increases from 330×10~(-6) to 660×10~(-6);(2)the canopy photosynthesis increases with radiation enhancement,and the daily total photosynthesis will increase by 6.7% when the radiation increases by 10.0%;(3)the canopy photosynthesis decreases with temperature increasing,and the daily total photosynthesis will decrease by about 2.9% when the temperature increases 1 ℃.The comprehensive numerical analysis indicates that the total daily canopy photosynthesis will become more sensitive to the variation of CO_2 and temperature under stronger radiation conditions.