Spectral Characteristics of Cyanobacteria Soil Crust in Semiarid Environments

Large areas of sand fields in arid and semiarid regions are covered by cyanobacteria soil crusts. The objective of this article is to analyze (systematically throughout the VIS, NIR, and the SWIR regions of the spectrum) the unique spectral features of cyanobacteria crust relative to bare sands and under different moisture conditions. It was found that: 1) When biogenic soil crusts are wet, their NDVI value can reach 0.30 units due to their photosynthetic activity; 2) the closer the red edge inflection point is to the longer wavelengths, the higher the relative abundance and distribution of the microphytic community; 3) the phycobilin pigments, which are unique to cyanobactria, contribute to higher reflectance in the blue region relative to the sand substrate; 4) a crust index based on this uncommon spectral feature can be useful for detecting and mapping, from remote sensing imagery, different lithologic/morphologic units; 5) although most dune sand areas are generally made of quartz, other notable features appear on their spectra. In the study area, there are absorption features representing minerals (iron oxides at 860 nm and clay minerals at 2200 nm) and biogenic crusts (chlorophyll at 670 nm and organic matter at 1720 nm, 2180 nm, and 2309 nm).