Figure 5. The continuum removed reflectance (Figure 5a) of the 2.1 µm absorption feature for two samples: a low nitrogen sample of dried and ground Norway spruce needles (dashed line) and a high nitrogen sample of dried and ground basswood leaves (solid line). The ratio of these two continuum removed reflectance spectra are shown in Figure 5b again 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.