# Cyanobacterial Potential for Restoration of Loess Surfaces through Artificially Induced Biocrusts
## 4 Discussion
### Particle Trapping and Stabilization by Cyanobacteria
The preparation of the inoculum comprising the strains from this study and its application in the field will be investigated in the future. The development of cyanobacterial biocrusts on loess sediments is strongly supported by their mineralogy and granulometry as well as cyanobacterial affinity to fine particles. A faster development of cyanobacterial biocrusts over the finer sand particles [56] and the formation of thicker biocrusts on finer soils compared to sandy soils [122] has been observed. The development of measurable biocrusts requires at least 4-5% clay and silt [123], while typical loess sediment consists mainly of silt (40-70%) and clay (5-20%) [2], the particles of which are finer than those of sands. The chemical composition of mineral particles can also influence the efficiency of sediment stabilization by affecting the weathering rate and the availability and quality of cations, which can affect the formation of organomineral bonds. The diversity of mineral particles in the loess is high, with the dominance of quartz (typically 60-70%, but there are also extremes), followed by mica, feldspars, carbonates and clay minerals. Also, finer particles comprising loess are more susceptible to weathering due to their large surface area. Such loess properties support intense weathering events and subsequent mineral precipitation, which are promoted by cyanobacteria and EPS. The mineral precipitation leads to the formation of organomineral structures between the particles [10], which improves EPS-particle binding and thus sediment stabilization. In contrast to loess, desert sand is strongly dominated by coarse quartz particles, which are extremely resistant to weathering. This could hamper the formation of organomineral bonds and thus lower the efficiency of particle/sediment stabilization. Studies on weathering and mineral precipitation events within the biocrust are rare, and this study shows that in the future more attention should be paid to the interaction of cyanobacteria with sediment particles and its influence on sediment stability. Topsoil stability and vegetation are regarded as the main concerns in combating desertification [35]. Many studies have described the role of cyanobacteria in sand stabilization through the formation of a complex network of filaments and EPSs e.g., [40; 41; 46; 52; 53; 54; 55; 56; 57; 58; 59; 109; 118; 119; 122; 124]. [PERSON] et al. [125] investigated the influence of two cyanobacterial species (_Oscillatoria prolifica_ and _Nostoc commune_) on aggregate stability of Peroria loess soil, the cyanobacterial potential to interact with loess particles, loess stabilization and use in loess restoration. Our study presents progress in this field to develop a strategy to combat desertification in loess landscapes. We demonstrated the formation of artificial biocrusts by initiating an interaction between dust particles as abiotic components and inoculated cyanobacterial cells as biotic components. This close relationship between biotic and abiotic components in direct contact with each other was recently recognized as synergosis [10]. Therefore, we suggest that a potential solution for the restoration of exposed loess surfaces and the mitigation of the desertification process and related problems in loess regions could be achieved by initiating the formation of cyanobacterial biocrusts. Our proposal is based on the use of cyanobacteria as inoculum for the initiation of biocrust formation and the acceleration of the natural succession of biocrusts from cyanobacteria to masses and further to vascular plants. The proposed use of cyanobacteria for stabilization and restoration of loess landscapes has its background in the BLOCDUST hypothesis [9; 10]. Earlier studies by [PERSON] et al. [35] and [PERSON] et al. [116] support the use of cyanobacteria as inoculum to accelerate the natural succession of biocrust components and further to develop communities of vascular plants.