Vegetation obscuration effects on mid-infrared laser reflectance of soil

Mid-infrared laser reflectances of soils containing specific minerals show diagnostic features in the 9-11 wavelength range, resulting in their suitability for remote sensing of terrestrial lithology. However, the presence of actively growing vegetation can obscure these diagnostic features, in some cases almost completely, so as to make mineral identification virtually impossible. An experimental study was carried out to determine the effects of growing grass on the mid-infrared laser reflectance of bare soil in order to determine the conditions under which the underlying soil reflectance loses its diagnostic features. Reflectance ratios (indicative of diagnostic features) were investigated as a function of grass-blade height for different grass densities. It was found that, under specific soil conditions, there appeared a grass-blade height value at which the diagnostic ratios level off to a value of 1.0, thereby masking the underlying soil features. These results are expected to be useful for identifying optimal conditions under which soil mineralogy can be identified under overlying vegetation.