Effects of lichens on the reflectance spectra of granitic rock surfaces

The objective of this study was to determine the effect of lichen cover on the spectral reflectance characteristics of granitic rocks. Rock samples collected from bedrock exposures and talus slopes were granodiorite, tonalite, granite, and quartz-diorite. The lichens found on these rocks varied in color, i.e., black, dark brown, medium gray, olive-green, yellow-green, green, orange, and orange-red. The visible and near infrared reflectance spectra (400–1100 nm) of the rock and lichen samples show that lichens can affect the rock's spectra. These changes are dependent on the reflectance contrast between the rock surface and the lichen covering.