Selecting phototrophic species of native biocrusts in arid and semi-arid regions

Background: Biological soil crusts (BSCs) that are able to produce sticky extracellular polymeric substances (EPS) play an important role in the formation of soil aggregates, thereby, reducing soil erosion. In this study, experiments were undertaken to identify biocrust species that produce EPS, in order to combat desertification in the Sejzi desert of Iran. Methods: A biocrust distribution map of Sejzi plain was prepared using Landsat 8 OLI images, then, various sampling points were selected. Some physicochemical parameters of samples from lichendominated and non-biocrusted areas were measured. The relationship between soil parameters and biocrusts presence was confirmed based on the Pearson's correlation coefficient and principal component analysis (PCA) method. The type of chemical compounds in the soil content were determined via Fourier transform infrared spectroscopy (FTIR), including polysaccharides. To estimate the degradability of polysaccharides, each soil sample was placed under defined UV-B radiation for 24, 48, and 72 hours at three replications. Results: There was no significant correlation between moss and lichen species with the amount of EPS (%) values and various occurring cyanolichen species in three biocrusted soil samples, which included Collema coccophorum, Collema tenax, Peccania terricola, and Placidium squamulosum. It was speculated that these polysaccharides were produced by the photobiotic partners (microalgae or cyanobacteria) and secreted to the soil. Conclusion: According to the results, the cyanobacteria species of biocrusted samples might have high potential to combat desertification and soil stabilization in Sejzi desert.