REFLECTANCE SPECTRA OF MICROPHYTIC SOIL CRUSTS IN SEMIARID AUSTRALIA

In the semi-arid region of eastern Australia quantitative field survey s showed that microphytic crusts (lichens, mosses and blue-green algae ) contributed up to 27 per cent of the ground cover. Spectral reflecta nce at wavelengths between 0.4 mum and 2.5 mum were recorded from crus ts on two soil types and under a number of different moisture conditio ns. Results showed that the presence of microphytic crusts on both soi l types decreased reflectance throughout the spectrum. When crusts wer e actively photosynthesising chlorophyll absorption features were obse rved. 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 i mportance of a knowledge of soil moisture regimes and their effect on the biotic soil crusts when interpreting remotely sensed imagery of th e region.