The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
1394 
equation (2), for example, substituting 
/850 /-760 
^ Rfd^ for Rf^x. > the index kept the high correlation 
with mixed leaves chlorophyll content (R 2 =0.7991) . So the 
index is calculated based on the reflectance of wavelength range 
of 698-7 lOnm and 740-900nm can serve as indictor of mixed 
canopy chlorophyll content. 
ci 
Figure 5. The relationship between chlorophyll content and CI 
Clwide 
Figure 6. The relationship between chlorophyll content and 
Clwide 
Filella et al. (1995) suggested that wheat canopy chlorophyll a 
concentration had strong linear relationship with the sum of the 
amplitudes of the first derivative between 680nm and 780nm 
and the amplitude of the main peak of the first derivative. The 
area of the derivative under the red edge ( 76 r ° ) also has 
& ADR= jD 
680 
been developed to indicate the total chlorophyll content. Based 
on the LOPEX93 database, we tested ADR for its application to 
indicate total chlorophyll content of mixed canopy. Figure 7 
illustrated that ADR can not be the indicator of the mixed 
canopy chlorophyll content. 
According to the analysis results in the table 1, the amplitudes 
of the first derivative between 720nm and 745nm can indicate 
the mixed canopy chlorophyll content. So the algorithm of ADR 
was modified to narrow the area of the derivative under the red 
edge to 725-735nm range. The result in Figure 8 showed that 
the area of*the derivative under the red edge between 725 and 
735nm was good indicator of the mixed canopy chlorophyll 
content. The sum of the amplitudes of the first derivative 
between535nm and 550nm had strong correlation (R 2 =0.71) 
with mixed canopy chlorophyll content (Figure 9). 
ADR 
Figure 7. the relationship between chlorophyll content and 
ADR 
D725-D735 
Figure 8. The relationship between chlorophyll content and the 
integration of the first derivative of reflectance at 725-73 5nm 
0 0.005 0.01 0.015 0.02 
D540-D550 
Figure 9. The relationship between chlorophyll content and 
the integration of the first derivative of reflectance at 
540-550nm 
4. DISCUSSION 
The results indicate the optimal band range for estimating the 
mixed canopy chlorophyll content is 698-715nm region, which 
is the part of the red edge. For the first derivative of reflectance, 
the optimal bands range was D720-D735nm region and 
D535-D550nm region. The 740-900nm region can be used as 
reference band. 
This study was performed based on LOPEX93 database. Further 
analysis is necessary to make sure that the optimal bands for 
estimating mixed canopy chlorophyll content can apply to other 
species unavailable in LOPEX93 database, especially conifer 
species.