350
R.W. Pearcy and W.A. Pfitsch
50
(f)
.::s:.
0
Q)
40
'IC
::J
(f)
30
'I0
+J
20
c
Q)
0
I.10
Q)
D....
0
80 I(f)
.::s:.
0
Q)
60
.---- -
'IC
::J
(f)
'I40
0
+J
C
Q)
20
0
I..---- -
Q)
D....
0
T
or
or
or
or
~-r+-r+2
4
8 16 32 64 128 256
Sunfleck duration (seconds)
Fig. 17.3. Histograms showing the percent of sunflecks (top) and percent of sunfleck PFD
received in sunflecks (bottom) of different duration in the redwood forest understory
basis. Extrapolation from gas exchange measurements such as those shown
above is difficult because of the required sampling on days with different
cloud covers and climatic conditions, and because of the extreme spatial
variation. Consequently, a more integrative approach is needed. Since the
carbon isotope ratio (013C) of plant tissue is a function of the ratio of intercellular to ambient CO2 pressure (pJPa) at which the carbon was fixed, it is a
measure of the behavior of stomatal conductance and assimilation relative to
one another. It is an integrative measure over the period that the carbon
making up the sample is assimilated. Although applied primarily to water
use efficiency problems (e.g., Farquhar and Richards 1984), it is also ap-
R.W. Pearcy and W.A. Pfitsch
50
(f)
.::s:.
0
Q)
40
'IC
::J
(f)
30
'I0
+J
20
c
Q)
0
I.10
Q)
D....
0
80 I(f)
.::s:.
0
Q)
60
.---- -
'IC
::J
(f)
'I40
0
+J
C
Q)
20
0
I..---- -
Q)
D....
0
T
or
or
or
or
~-r+-r+2
4
8 16 32 64 128 256
Sunfleck duration (seconds)
Fig. 17.3. Histograms showing the percent of sunflecks (top) and percent of sunfleck PFD
received in sunflecks (bottom) of different duration in the redwood forest understory
basis. Extrapolation from gas exchange measurements such as those shown
above is difficult because of the required sampling on days with different
cloud covers and climatic conditions, and because of the extreme spatial
variation. Consequently, a more integrative approach is needed. Since the
carbon isotope ratio (013C) of plant tissue is a function of the ratio of intercellular to ambient CO2 pressure (pJPa) at which the carbon was fixed, it is a
measure of the behavior of stomatal conductance and assimilation relative to
one another. It is an integrative measure over the period that the carbon
making up the sample is assimilated. Although applied primarily to water
use efficiency problems (e.g., Farquhar and Richards 1984), it is also ap-