Rapid artificial biocrust development by cyanobacterial inoculation and clay amendment

The establishment of biological soil crusts is widely perceived as a main strategy to improve the ecological environment in arid and semi-arid regions. However, artificial biocrusts fail to withstand environmental stresses when using traditional methods for initial establishment. Hence, in this study, kaolin, a common clay mineral, was introduced as a biocrust stabilizer by mixing at different mass ratios with Microcoleus steenstrupii for sand inoculation. The results showed that the addition of kaolin exhibited a significantly positive effect on promoting biocrust formation and accelerating biocrust development. Moreover, the artificial biocrust from 1:500 (algae: kaolin) inoculant achieved the best performance with coverage of 98%, and top layer thickness of 5.62 mm after 86 days of incubation. The highest contents of chlorophyll a, exopolysaccharides, and soluble protein were also observed in 1:500 mass ratio of algae: kaolin throughout the biocrust development process. As for the water retention performance, the results of contact angle, water drop penetration time (WDPT), and repellency index (RI) illustrated that biocrust improved water utilization in kaolin-treated groups by delaying the time of water infiltration, especially in 1:500 group. After 86 days post inoculation, a series of common bacteria appeared in the biocrusts such as actinobacteria and acidobacteria, and decomposed metabolites from cyanobacteria as an energy source. This study gains new insights into clay minerals on biocrust development and puts forward a new approach for rapid artificial biocrust establishment to reverse desertification.