between the species is more than within them. We calculated
these vegetation indices listed in Table 2, that are based on
the chlorophyll absorption band in the 680- 850 region of the
spectrum.
Statistical analysis
The differences between sunlit and shaded leaves in each
species were tested by comparing the mean of vegetation
index values. We also used Analysis of Variance (ANOVA)
to test the differences among the species both in sunlit and
shaded leaves. Statistical analyses were performed with SAS
software.
3. RESULT AND CONCLUTIONS
3.1. Spectral fingerprinting of forest species
The sampling plan in acquiring spectral measurement is very
important to get a reliable spectral library. Because of large
altitude gradient in the Caspian forest and complex
topography as well as uneven aged stands we sampled the
species in different diameter from dominant stairs to cover
the variety of the spectral signature between different
samples.
The spectra of the collected species show the typical pattern
of vegetation (Figure 2). A visual discrimination of the
species by their reflectance alone must be regarded as
difficult for most species. Figure 2 shows the mean spectra of
all five species in two illumination conditions. Although we
could distinguish that sunlit leaves shows less reflectance
values for some species verse shaded leaves, it must be
statistically tested to prove the differences between them.
In order to remove the noise spectra in water absorption
feature wavelength we calculated the standard deviation of all
reflectance values in each wavelength and omitted the values
which were more than twice of standard deviation (Figure 3).
Since a non-noisy reference spectrum does not exist, we
focused on those wavelengths that had values less than twice
of standard deviation.
Alder
(Alnus subcordata)
wavelength (turn)
Hornbeam
(Carpinus betulus)
| 0,
1 03
0,2
550 »0 ?50 950 * *50 1350 1550 1?5Q 1950 2150 2350
wavelength (nm)
wavelength (nm)
Common Oak
(Quercus castaniafolia)
I «
£
f 0.3
m «o m m
11» \m 1560 1W0 1950 2150 2350
wavelength (nmj
Figure 2: Spectral fingerprints of five tree species in two
exposed conditions (shaded vs. sunlit leaves). Black lines
represent sunlit leaves and gray line shaded leaves.
1150 1350 1550 1750 1950 2150 2350
Wavelength (nm)
1.4E+16
1.2E+16
3 1E+16
c
J
I 8E+15
«
I 6E+15
T)
c
w 4E+15
2E+15
b
4$
%
■ standard
deviation
i
}
i
ft
I ;
Figure 3: Standard deviation (b) calculated for all reflectance
values in each wavelength to remove the noise spectra in
water absorption bands (a).