was GVIT 775 and Okoboji where distinct spectral signatures
were located in the 690-750 nm (
p
<0.02) region (Figure 5b).
Canopy Reflectance Factor Spectra Separability
We analyzed the canopy reflectance factor spectra with the
same method that we used for leaf reflectance factor spectra.
Again, the mean canopy reflectance factor spectra of two
grapevine species were distinguished visually (Figure 6).
Interestingly,
V. riparia
had higher reflectance factor values
in portion of
VIS
, full
NIR
, and SW
NIR
spectral regions than
V. rupestris
, which was opposite to what we found in leaf
reflectance factor spectra (Figure 1). Possible causes of this
observation will be explored in the Discussion Section. In the
VIS
and
NIR
spectral regions, the number of spectrally sepa-
rable bands in canopy reflectance factor spectra was reduced
substantially compared to leaf level spectra. In contrast, the
number of spectrally separable bands expanded in the
SWIR
spectral region together with an increase in their statistical
significance (
p
<0.01).
Figure 5. Mean 2
nd
-d leaf reflectance factor spectra of (a)
V. riparia
and
V. rupestris
, (b) GVIT 775 and Okoboji within
V. riparia
, and
(c)
with band-by-band t-tests showing significant differences in grey bars (p-values≤0.05).
Figure 6. Mean canopy reflectance factor spectra of
V. riparia
and
V. rupestris
with band-by-band t-tests showing significant differ-
ences in grey bars (p-values≤0.05)
Figure 7. Mean canopy reflectance factor spectra of (a) B 38 and R-66-3 within
V. rupestris
, (b), B 38 and R-66-9 within
V. rupestris
, (c),
R-67-2 and R -66-3 within
V. rupestris
,
(d), R-67-2 and R-66-9within
V. rupestris
, with band-by-band t-tests showing significant differences
in grey bars (p-values≤0.05).
56
January 2016
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
