Micro-topography dominated microhabitat significantly influences colonization and development of incubated-cyanobacteria biocrusts in a harsh sandy desert environment

Incubated biocrusts is a promising biotechnology for restoring biocrusts and for improving soil health in dryland environments. However, it is challenging to use this method to restore biocrusts on a large-scale, because sand dunes have a complex morphology, and the angle of their varying slopes can expose biocrusts to wind speeds that delay or even prevent their development. In this study, we investigated how micro-topography, i.e. steepness of a sand dune's slope, affects cyanobacteria communities that incubate and restore biocrusts. We covered four different portions of a sand dune (which ranged between 2.3° and 31.3° of slope) with fine-soil substrate in the Tengger Desert, China, and then measured the cyanobacteria's colonization, development, and composition over three years as they formed biocrusts. The cyanobacteria successfully formed biocrusts on all sand dune slopes, and the greatest coverage (36.40 %), thickness (2.70 mm), biomass (22.38 μg cm−2), and exopolysaccharide content (EPS, 306.49 μg cm−2) occurred at the lowest degree of slope (2.3°–5.6°, dune-lowland), whereas the minimum coverage (4.90 %), thickness (1.62 mm), biomass (8.45 μg cm−2), and EPS (160.89 μg cm−2) occurred at the steepest degree of slope (25.3°–31.3°, dune-crest). These plots involved 20 genera of cyanobacteria, and Phormidium was the dominant genus, occupying >65 % of the species composition across all slope treatments. The steepness of a sand dune significantly and negatively influenced the biocrusts' coverage, thickness, chlorophyll a, and EPS (p < 0.05). Steepness was also negatively related to Phormidium (p < 0.05), but positively related to Crinalium, Sericytochromatia (p < 0.05), Chloroplast, and CENA359 (p < 0.10) genera. Our study demonstrated that covering sand with a fine-soil substrate can lead to the successful incubation of biocrusts. Further, the importance of the degree of sand dune slope demands further study to ensure maximum biocrusts restoration at a large scale. It will also be necessary to use a variety of cyanobacteria species in these future studies to achieve a broader knowledge of community functionality.