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the vegetation bud, known before only for a leaf. These studies revealed an
interaction between spectral characteristics of a vegetation species (spectral vege-
tation index
SVI) and important functional relationships that regulate the pro-
cesses of photosynthesis and evaporation off leaf canopies. Apart from this, an
accomplished analysis revealed a connection between the share of the photosyn-
thetically active radiance (PAR), absorbed by the vegetation canopy with the
respective characteristic coef
—
cient of vegetation species (simple ratio vegetation
index
SR). Here, we consider SR and relative difference (normalized difference
vegetation index
—
NDVI) as SVI. Spectral characteristics of vegetation species SR
and NDVI are based on the remote sounding of the re
—
fl
ected emission in the visible
and near-IR regions and determined as follows:
SR ¼ a
N
=
a
V
;
NDVI ¼ a
N
a
V
ð
Þ=
a
N
þ
a
V
ð
Þ
where a
N
and a
N
are hemispheric re
fl
ections and radiance in the visible and near-IR
wavelength regions, respectively.
The parameters a
N
and a
N
are measured directly above a leaf canopy. Therefore
the effects of absorption and scattering of emission by the atmosphere are not
considered here. For the space-borne remote sounding a method has been devel-
oped to correct the experimental data, FASIR (Fourier-adjusted, solar zenith angle
corrected, interpolated and reconstructed data). A theoretical dependence (close to
linear) has been established between PAR and SR, con
rmed later by experimental
measurements in the region of Kansas (Sellers et al. 1995, 1996, 1997). A minimum
and maximum of FPAR are determined experimentally, and the
final relationship
becomes
SR
SR
i
;
min
ð
PAR
max
PAR
min
Þ
PAR ¼
ð
8
:
6
Þ
SR
i
;
max
SR
i
;
min
where PAR
max
= 0.950, PAR
min
= 0.001, but in general, PAR
max
and PAR
min
depend
on the type of vegetation; SR
i
;
max
and SR
i
;
min
can be calculated from NDVI, based
on experimental data.
Sellers et al. (1996) use the
ecting an amount of vegetation
cellulose taking part in the process of photosynthesis. The
P
parameter re
fl
P
parameter changes
from 0 (lack of vegetation) to
1
5 for bushy species rich in photic vegetation
cellulose and can be approximately estimated as
:
PAR
k
P
where k is the coef
cient of attenuation for PAR averaged in time.
Apart from spectral characteristics, Sellers et al. (1996) considered the photic
characteristic (green leaf area index L
g
) and the photic share (green part N) for a
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