Detailed Models of Light Interception by Canopies
253
vertical
I
\
0
10
20
30
40
50
60
70
80
90
Zenith Angle (degrees)
FIGURE 15.3. Fraction of the incident solar beam reaching the ground below a
canopy with LA1 = 1, for different leaf angle distributions.
bution of leaves in the canopy, it is often assumed to be spherical. Values
of x are not particularly intuitive for understanding leaf orientation. Mean
leaf inclination angle is more easily understood. The mean leaf inclination angle can be approximated as COS-'(K~,(O)) using Eq. (15.4). The
mean leaf inclination angles are therefore about 73", 60°, and 34" for x
values of 0.5, 1.0, and 3.0. This approximation of mean leaf inclination
TABLE 15.1. Values of the leaf angle distribution parameter
x for various crop canopies (from Campbell and van Evert,
1994)
Crop
x
Crop
x
Ryegrass
Maize
Rye
Wheat
Barley
Timothy
Sorghum
Lucerne
Hybrid swede
Sugar beet
Rape
Cucumber
Tobacco
Potato
Horse Bean
Sunflower
White clover
Strawberry
Soybean
Maize
J. artichoke