The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008
is more efficient than the traditional method of using original
spectra reflectance to explore the change of reflection curve.
The relationship between REP and chlorophyll content will be
studied further in the following section.
Wavelength (nm)
Figure 1. The reflectance spectrum and derivative reflectance
spectrum of all species mean spectrum reflectation
3.2 Relationship Between REP and Chlorophyll Content
In this study, in order to explore the capability of using REP to
estimate the chlorophyll content of leaves, the correlation
coefficient related with red edge inflection point, REP and
chlorophyll, and carotenoid of each species was analyzed as
shown in Table 1.
Table 1. Regression equations relating the parameters of red
edge of leaves to their pigment contents for Daphniphyllum
glaucescen, Michelia compressa, Illicium dunnianum and
Machilus kusanoi
Trees
Regression equations
R 2
Daphniphyllum
glaucescen
Chi = 98.584X.red -66761.259
Car = 42.565X.red -28546.904
0.508**
0.696**
Michelia compressa
Chi = 215.619Xred -149796.414
Car = 74.906Xred -51566.680
0.666**
0.617**
Illicium dunnianum
Chi = 147.675Xred -102017.431
Car = 66.055Xred -45729.653
0.503**
0.669**
Machilus kusanoi
Chl = 113.183X.red -77126.258
Car = 42.886Xred -29021.724
0.774**
0.770**
All species
Chi = 133.989Xred -91865.439
Car = 49.718Xred -33753.059
0.577**
0.541**
**,P<0.01
From Table 1, there is a good correlation between the red edge
parameter and the total contents of chlorophyll and carotenoid,
and have reached at 0.01 significant level; while on the aspect
of the correlation between REP and the total chlorophyll
content, Michelia formosanaand Illicium dunnianum reached a
great level.
the location of red edge comparatively near longer wavelengths
range is an index that shows healthy growing.
Based on these preceding results, the samples of the 4 species
were comprehensively studied for the relationship between REP
and chlorophyll content and carotenoid, and are illustrated in
Fig. 2. From Fig. 2, correlation between some indices was
obvious not only in the analysis of a single species, but also in
the mixed samples of 4 species. From the above results a
conclusion may be drawn that whether an analysis is conducted
on a single species or a group of tree species, chlorophyll and
carotenoid content can be calculated with their linear
relationship with REP; REP can faithfully reflect the thickness
of pigment in plants’ leaves. These results agree with the
studies of most reports, although many researches were about
crops (Dalezios et al., 2001; Pattey et al., 2001; Thenkabail et
al., 2000).
Figure 2. Relationship between leaf red edge inflection point,
chlorophyll content and carotenoid content of mixed species.
Pigments extracted with acetone from Daphniphyllum
glaucescen, Michelia compressa, Illicium dunnianum and
Machilus kusanoi
The REP shift to shorter wavelengths due to pigment
degradation, as expected and previously reported (Horler et al.,
1983; Vogelmann et al., 1993). Despite these described may
change in the canopy scale (due to the canopy structural
change), it can be seen that the REP indicator of pigment
content could be detected from the experiment of REP value in
leaf scale. And there were many suitable simulate models for
broad leaf canopies to link leaf optical properties with canopy
structural characteristics through radiative transfer modeling
(e.g., PROSPECT model, SAIL model, LIBERTY model,
BOREAS model). The next section describes the results
obtained that the relationship between several vegetation
indices calculated from the leaf spectral reflectation and leaf
pigment content measurements in different terrains.
From the above results we understand that the average REP
always moved towards longer wavelength with the increase of
chlorophyll content, which is called “red shift”; the REPs of all
species were in the range of 698 nm-723.2 nm; from the view
angle of plant’s physiological condition, when the leaves are
senescing or when they are under adverse environmental
conditions, their chlorophyll contents may fall gradually, and
the location of the red edge tent to move towards shorter
wavelength, which is called “blue shift”. This result shows that
3.3 Vegetation Index and Chlorophyll Content
This study analyzed the relationship between pigment content
and NDVI, mNDVI, SR, and mSR; the results of a single tree
species are in Fig. 3. From the results we understand that the
correlation between 2 modified indices such as mNDVI and
mSRand chlorophyll content were much better than the
ordinary vegetation indices i.e. NDVI and SR. After the factor
of different leaf structures is taken into calculation according to
the calculation principle for modified vegetation indices, the
233