Polysaccharide-rich cyanomass showed potential for long-term stabilization and ecological restoration of compression-degraded soils in arid drylands

In drylands, which cover >40 % of the Earth's terra firma, anthropogenic soil compression damages biological soil crusts (biocrusts), disrupts subsurface microbial communities, and exposes destabilized mineral soil to weathering. Weathering causes dust generation and erosion, threatening human health and infrastructures. Ecological restoration aims to restore soil ecosystem services by repairing soil structural integrity and functionality. However, in arid regions, effective restoration is largely limited to biocrust seeding. To bolster biocrust-mediated restoration of powdered sandy loam soils in arid regions, extracellular polysaccharide-rich biomass of terrestrial cyanobacteria (EPS-rich cyanomass) was applied to the subsurface soil alongside surface biocrust seeding. The EPS-rich cyanomass served a functional, non-proliferating amendment intended to bind mineral particles stabilizing soil, reducing erosion, and facilitating biocrust establishment and subsurface microbial recovery. Consequently, following cyanomass application, we examined mechanical soil stability, biocrust development, and the size and cyanomass-degradation capacity of subsurface microbial communities for two years. As controls, we included biocrust-seeded unamended soil and soil treated with a synthetic polyacrylamide used for soil stabilization as well as the intact soil. We found that, following the application of 4 g/m² of EPS-rich biomass, soil stability and biomass and enzymatic activity of subsurface microorganisms approached the levels observed in intact soil. The measured capacity for EPS consumption of subsurface microbial community after two years indicated lasting benefit of the cyanomass treatment. This proof-of-concept field study showed that the novel EPS-rich cyanomass-mediated approach of structural and functional subsoil restoration has high potential for ecological recovery of damaged soils in arid regions.