Although there were not spectrally separable bands among
the
V. riparia
genotypes, we were able to identify them in
V.
rupestris
genotype groups. Some of these separable bands
were not even found in leaf spectra comparison groups. For
instance, the B 38 and R-66-3, B 38, and R-66-9, and R-67-2
and R-66-9 genotype groups were spectrally separable in
VIS
,
NIR
, and
SWIR
regions (Figure 7a, 7b, and 7d). The R-67-2 and
R-66-3 group, which also had separable bands in leaf reflec-
tance factor spectra (Figure 2d), was discriminated in
VIS
band
range (517-612 nm and 696-731nm) (
p
<0.04) (Figure 7c).
The 1
st
-d canopy reflectance factor spectra enabled us to
detect wavelength specific differences that were not shown
in the raw canopy reflectance factor data. Figure 8 presents
the evidence that more spectrally separable bands between
two grapevine species were identified in
VIS
and
NIR
regions.
Among genotypes, the 1
st
-d calculation not only revealed
significantly different
VIS
bands in the B-38 and R-66-9 group
(Figure 9a), but also identified a new genotype group R-65-44
and R-66-9 which had separable bands through the
VIS
and
NIR
regions and part of the
SWIR
region (
p
< 0.03)
(Figure 9b).
The 2
nd
-d canopy reflectance factor spectra were also
analyzed for species and genotype groups. However, 2
nd
-d
was only capable of detecting significantly different bands at
the species level (Figure 9c). This finding was very similar to
the result that we found with our 1
st
-d analysis. There were
also few numbers of separable bands in genotype comparison
groups (data not shown).
Foliar Separability
We found by examining growing grapevines of nine genotypes
that foliar properties differ noticeably between species. Fresh
and dry leaf weight of
V. riparia
was significantly higher than
that of
V. rupestris
(
F
1, 59
= 19.92,
p
< 0.01 and
F
1.59
= 44.49,
p
< 0.01, respectively) (Figure 10a and 10b). Correspondingly,
the
LAI
had higher values among
V. riparia
genotypes than
V. rupestris
. The
V. rupestris
LAI
had a broader data range
compared to the ranges of all other properties discussed here.
However, the difference in
LAI
between the two species was
not statistically significant (
F
1, 59
= 0.13,
p
= 0.72) (Figure 10c).
Similarly,
V. rupestris
genotypes differed from
V. riparia
geno-
types with their lower total chlorophyll content, but again the
difference was not significant (
F
1, 59
= 2.37,
p
= 0.13) (Figure
10d). As we expected, s
PRI
, an indicator of epoxidation state
of xanthophyll, was significantly lower in
V. riparia
than in
V. rupestris
(
F
1, 59
= 15.52,
p
<0.01) (Figure 10e). We expected
this because these two grapevine species have different
drought tolerance characteristics.
Among genotype pairs of
V. riparia
, the results of one-way
ANOVA
did not show significant differences in any of the foliar
properties. Therefore, we did not perform a Bonferroni adjust-
ed t-test. Within
V. rupestris
species, one-way
ANOVA
results
Figure 9. Mean 1
st
-d canopy reflectance factor spectra of (a) B 38 and R-66-9 within
V. rupestris
, (b) R-65-44 and R-66-9 within
V. rupes-
tris
,
(c), Mean 2
nd
-d 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 8. Mean 1
st
-d canopy reflectance factor spectra of
V. ripar-
ia
and
V. rupestris
, with band-by-band t-tests showing significant
differences in grey bars (p-values≤0.05).
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
January 2016
57
