Calculating Canopy Assimilation from Leaf Assimilation
average:
pmol
= 177 m 2 (leaf hemi-surface area) s '
The scattered beam radiation is zero at the top ofthe canopy and is given by
Qs, = Qbt (@) - Qb(@) at the bottom. If the beam extinction coefficient
is
then
= 278 pmol photons m-2 (ground area) s-'
= 226 pmol photons m-2 (ground area) s-'
Q,, = 278 - 226 = 52 pmol photons m-2 (ground area)sP' .
Therefore the average scattered illumination on leaves is (52 + 0)/2 =
26 pmol photons m-2 (leaf hemi-surface area) s-' . The PAR flux density
absorbed by shaded leaves is
pmol photons
= 162 m 2 (leaf hemi-surface area) s
where the overbar denotes an average over the depth of the canopy. The
PAR flux density absorbed by sunlit leaves is given by
pmol photons
= 997 m 2 (leaf hemi-surface area) s '
The sunlit LA1 (LT) and shaded LAI (L, - LT) are given by
m 2 (leaf hemi-surface area)
= 1.32
m 2 (ground area)
L, - LT = 3.0 - 1.32 = 1.68
m
2 (leaf hemi-surface area)
m 2 (ground area)
The leaf assimilation rates can be obtained from Fig. 14.6 using 12sh for
shaded leaves and
for sunlit leaves. The leaf assimilation rates in Fig.