Geoscience Reference
In-Depth Information
1.00
1.00
0.90
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A
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B
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0.00
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0
20 40 60 80 100 120 140
0
20 40 60 80 100120140
Canopy Height (cm)
Canopy Height (cm)
1.00
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C
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Canopy Height (cm)
Figure 5.7
Light attenuation profiles ([
marsh
representing the aggregate of (A) all profiles, (B) only undisturbed canopy locations, and (C) partial
canopy gaps.
●
] 30 March and [
] 9 July) associated with a
Spartina patens
of herbivory on a Spartina P. marsh closely preceding the March occupation and regrowth toward
recovery by July (Figures 5.7A, B, and C). Inclusion of locations with partial canopy (Figure 5.7C)
fully distorted the consistency shown in the undisturbed profiles (Figure 5.7B).
5.3.3
Changing Sun Zenith
Normalization of canopy light penetration measurements to a nadir sun zenith was more
successful in more vertical canopies such as Juncus R. and less effective in more lodged and
horizontal canopies such as Spartina P. Canopy light penetration recordings collected at one Juncus
R. site at four different times and sun zeniths show a number of results of applying the sun zenith
correction factor (Figures 5.8A and B). First, as sun zenith increased the rate of PAR fall-off with
canopy depth increased. After application of the sun zenith correction factor, the PAR fall-off was
greatly decreased, and conversely the magnitude of PAR reaching lower within the canopy was
vastly increased. Second, after correction, light attenuation profiles associated with the first three
1.00
1.00
0.90
0.90
0.80
0.80
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0.70
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A
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B
0.00
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0
120 140
Canopy Height (cm)
20
40
60
80
100
0
20 40 60 80 100120
Canopy Height (cm)
140
Figure 5.8
Aggregate light attenuation profiles of a
Juncus roemerians
marsh associated with PAR collections
at a sun zenith angles of [
—
] 54
∞
, [
] 59
∞
, [
✴
] 66
∞
, and [
] 75
∞
(A) without normalization and (B)
with normalization of PAR recordings to a nadir collection.
