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A Reminder of the Limitations in Using Beer's Law to Estimate Daily Radiation Interception by Vegetation

Agronomy Physiology Lab., Univ. of Florida, P.O. Box 110965, Gainesville, FL, 32611-0965

View larger version (16K): [in a new window]   Fig. 1. Leaf shadow projection (G) values presented by Duncan et al. (1967) plotted as a function of sun angle.

View larger version (18K): [in a new window]   Fig. 2. Instantaneous extinction coefficients (ki) throughout the day for canopies of various leaf angles.

View larger version (17K): [in a new window]   Fig. 3. Incident and total intercepted radiation calculated for a crop on Day 180 at latitude 30° with leaf area index (L) of 3 and a leaf angle of 45°.

View larger version (14K): [in a new window]   Fig. 4. Daily extinction coefficient (kd) calculated at various leaf area indices and for three leaf angles.

View larger version (16K): [in a new window]   Fig. 5. Daily extinction coefficient (kd) plotted against midday ki calculated for the same conditions. The dash line represents the line of equality for the two variables and the solid line is the regression between the two variables.

View larger version (13K): [in a new window]   Fig. 6. The time in the morning at which radiation interception by a canopy should be measured to obtain directly a ki value that is equivalent to the kd value for the conditions of differing leaf area indices and leaf angle.

View larger version (15K): [in a new window]   Fig. 7. Extinction coefficient under uniformly diffuse incident radiation plotted for canopies of various leaf area indices and leaf angles.