observation conditions; and 3) explore relationships between biophysical properties (i.e., LAI, A ) and canopy 
reflectance (Suits, 1972; Kimes et al., 1984; Verhoef, 1984). 
Photosynthetically active radiation (PAR) absorbed by plant pigments is the energy source for 
photosynthesis. The pigments making the greatest contribution to light absorption and photosynthesis are 
chlorophyll a, chlorophyll b, and carotenoids (Fig 1). Both chlorophylls a and b have absorption maxima in the 
640 nm-690 nm region and in the 440 nm-470 nm region. Also /9 -carotene has an absorption maximum at 470 nm 
region and minimum absorption beyond 530 nm. Both chlorophylls and /9 -carotene have minimal absorbance at 
550 nm region and beyond 700 nm. One of the canopy reflectance characteristics that directly governs the amount 
of light absorption and reflectance 
is the quantity of these 
photosynthetic pigments in the 
plant leaves. Also, the amount of 
exposed nonphotosynthetic 
materials including soil, leaf litter, 
and woody biomass such as twigs, 
stems, and trunks have been shown 
to be important factors in canopy 
reflectance. 
The main objective of this 
research is to investigate the use of 
narrow reflectance bands in remote 
estimates of canopy A . The 
research concentrateci toward 
reducing the variability in the A 
estimates due to the presents of 
diverse nonphotosynthetic 
materials. This technique utilized 
narrow spectral bands with 
bandwidth of approximately 10 nm. 
For evaluating the proposed 
narrow band method, the SAIL 
(scattering from arbitrarily inclined 
leaves; Verhoef, 1984) canopy 
model was used; 1) for simulating 
vegetation canopy reflectance as a mixture of green biomass and background material components; and 2) to 
derive v4 par This model has been used successfully in similar applications (Goward et al., 1992, Hall et al., 1990). 
Wavelength (nm) 
Figure 1 
Absorbance of pure plant pigments (Absorbance = log 
(Iq/I), Iq = incident, I = transmitted light) 
2. DEVELOPMENT OF NARROW BAND METHOD 
2.1 Leaf level Reflectance 
TABLE 1. Correlations (r 2 ) between soybean leaf reflectance (n = 50) bands. Reflectance measurements 
were acquired using LI-COR 1800 spectroradiometer and integrating sphere. 
Wave (nm) 
550 
670 
690 
700 
710 
750 
800 
550 
1.000 
0.786 
0.930 
0.992 
0.981 
0.000 
0.062 
670 
0.786 
1.000 
0.914 
0.802 
0.710 
0.005 
0.083 
690 
0.930 
0.914 
1.000 
0.955 
0.871 
0.001 
0.075 
700 
0.992 
0.802 
0.955 
1.000 
0.973 
0.000 
0.059 
710 
0.981 
0.710 
0.871 
0.973 
1.000 
0.008 
0.034 
750 
0.000 
0.005 
0.001 
0.000 
0.008 
1.000 
0.903 
800 
0.062 
0.083 
0.075 
0.059 
0.034 
0.903 
1.000