SunScan User Manual v 1.05
Measurement options
••••
45
Estimating ELADP in the field
If the canopy shows a clear predominance of horizontal or vertical leaves, then
choose a small volume of the canopy that is representative. Count the number of
leaves that are at more than 45° from the vertical (i.e. mostly horizontal), and the
number of leaves that are less than 45° from the vertical. If the leaves are curved,
pick the angle at the widest part of the leaf. The ELADP can be estimated as the
number of horizontal leaves (N
h
) divided by the number of vertical leaves (N
v
),
multiplied by
π
/2 (1.6).
ELADP
N
N
h
v
=
π
2
The factor
π
/2 comes from the fact that the vertical leaves are distributed about the
vertical axis, so for any light ray, some will be seen face-on, and some edge-on. In
effect, the ellipsoidal distribution is being further approximated as a cylindrical
distribution.
If you set ELADP to 1024, and Absorption to 1.0, the LAI calculations will be
equivalent to the simple Beer’s law inversion based on black, horizontal leaves.
Relationship between Mean Leaf Angle and ELADP
Wang & Jarvis (1988) describe the relationship between ELADP and the Mean Leaf
Angle, which is sometimes known from other studies. Their results are summarised
by the following graph:
0.01
0.1
1
10
100
0
10
20
30
40
50
60
70
80
90
ELADP
MLA degrees
