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where
ˈ
s
is the value of saturation potential for
moisture content in the soil (m); B is an empirical parameter; is
l
is the parameter of
suppression of high and low temperatures;
ˈ
c
is a critical water potential (m);
W
s
W
B
W
r
=
is the potential of moisture
2
content in the root later of the soil (m).
The physiological processes described by the A
c
and g
c
parameters do not exhibit
an instant response to changes in the control derivatives. It takes about 1 min to
stabilize the photosynthesis process after changes in the external conditions, but for
conductivity the time step constitutes several minutes. Hence, for time steps longer
than one minute the photosynthesis intensity A
c
can be calculated using relationship
(
8.7
), and a delay in changes of conductivity can be described reliably by the
equation:
@
g
c
@
t
¼
k
g
g
c
g
inf
ð
Þ
ð
8
:
8
Þ
where k
g
is a time constant for the response of vegetation cellulose (=0.00113 c
−
1
);
g
c
inf
¼ g
c
for t
!1;
g
c
inf
¼ m
A
c
c
S
h
S
p
þ
b
:
The solution (
8.7
) is written as:
g
c
inf
;
g
c
0
¼ g
c
for t ¼ 0
;
g
c
¼ e
k
g
t
g
c
0
þ
1
e
k
g
t
and a change in the g
c
during a time step
D
twillbe:
g
c
inf
g
c
0
1
e
k
g
D
t
D
g
c
¼ g
c
g
c
0
¼
ð
Þ:
These correlations give the opportunity to calculate the energy
fl
fluxes in a
“
”
multi-layer structure of the system
. As a result, one can
specify the elements of the climate models, and to assess from the space-borne
monitoring data the impact of surface vegetation on the synoptic situation. This is
especially important in arid and over-humid zones where the state of vegetation
cover strongly depends on small changes of temperature and other meteorological
parameters. Another important conclusion from these correlations can be drawn
for the study of the effect of vegetation cover on the processes of CO
2
assimilation
from the atmosphere. Clearly, the use of such models increases the adequacy of
the global carbon cycle modeling.
atmosphere-plant-soil
8.3.7 Modeling the Forest Age Structure
Seppelt and Voinov (2002, 2003) proposed two-stage procedure for the age
structure modeling of the forest ecosystem. The
first stage uses the simulator and
model for the parameterization of carbon balance and heterotrophic ecosystem
transpiration only for stand of isolated tree. The second stage synthesizes regional
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