Reflectance spectra of microphytic soil crusts in semi-arid Australia

In the semi-arid region of eastern Australia quantitative field surveys showed that microphytic crusts (lichens, mosses and blue-green algae) contributed up to 27 per cent of the ground cover. Spectral reflectance at wavelengths between 0·4 μm and 2·5 μm were recorded from crusts on two soil types and under a number of different moisture conditions. Results showed that the presence of microphytic crusts on both soil types decreased reflectance throughout the spectrum. When crusts were actively photosynthesising chlorophyll absorption features were observed. A strong photosynthetic response occurred within ten minutes of wetting. This work highlights the importance of microphytic crusts as a ground component in the semi-arid region of Australia and also the importance of a knowledge of soil moisture regimes and their effect on the biotic soil crusts when interpreting remotely sensed imagery of the region.