Figure 3. The continuum removed reflectance
(Figure 3a) of the 2.1 µm
absorption feature for two dried and ground Douglas-fir samples: a low
nitrogen sample (dashed line) and a high nitrogen sample (solid line).
The ratio of these two continuum removed reflectance spectra are shown
in Figure 3b indicating that absorptions at 2.054 µm
and 2.172 µm cause a broadening of the 2.1 µm
absorption feature as nitrogen concentration increases.