Leaf to Canopy Scale
0.6
8
~ 0.4
011
I ;
011
a:: 0.2
o
350
850
1350
1850
2350
Wavelength (nm)
Populus res prouts
0.7 r-....;....-------------,
0.6
LAI: 4.8
0.5
8
~ 0.4
£ 0.3
011
a:: 0.2
0.1
o ~---~~--. . ---~-~~~
350
850
1350
1850
2350
Wavelength(nm)
FIGURE 1.2. Leaf and canopy scale spectra of natural materials. The photograph on the left shows Populus resprouts
(P. deltoides X P. nigra = D X N) located in the vicinity of Wallula, WA. Plants were flagged and placed in five height
classes covering a range of heights and LAIs. Multiple spectra were collected from each resprout. A subset of 25 plants
was destructively harvested to determine LAI for each plant and compared with canopy spectra and several spectral
indices. Example spectra of a leaf, bare soil, and a Populus stump are shown in the upper right frame. Diagnostic
absorptions for chlorophyll in the visible, liquid water in the NIR, and lignocellulose in the shortwave infrared are
marked by arrows. Four spectra, sampled from bare soil and three canopies with LAIs ranging from 1.8 to 4.8, are
shown in the lower right frame. Note the general decrease in red reflectance and increase in NIR reflectance with
increasing LA!. Details on LAI sampling and spectral analysis are provided in Roberts et al., (l998b).