Rapid Establishment And Mechanism Exploration Of Artificial Algal Crusts Propelled By Clay Minerals

The area of desertification land in China is as high as 2.61 million square kilometers,of which the area in arid and semi-arid regions accounts for 80.48%.Desertification has been hailed as a forbidden zone for life and is one of the most serious ecological and environmental problems in the world.Biolocrusts are the primary stage of natural succession of degraded ecosystems,which can effectively improve soil physical and chemical properties and have great potential for desertification restoration,but their natural formation takes dozens or even hundreds of years.Therefore,accelerating the restoration of biocrust interfaces through human intervention has gradually become a research hotspot in desertification control.This study intends to prepare complex inoculum to rapidly construct artificial algal crusts by screening clay minerals and the optimal cyanobacteria/clay ratio,and explore the mechanism of growth-promoting and soil and water conservation via the analysis of structural reconstruction,hydrological morphological changes,and differences in microbial communities.The main results are as follows:(1)The study of cyanobacteria-clay co-culture showed that both montmorillonite and kaolin promote the secretion of exopolysaccharide,soluble protein and proline by cyanobacteria,and reduce the content of malondialdehyde in solution.The promotion effect of the kaolin group was more significant.On the 4th day,the exopolysaccharide and soluble protein of the montmorillonite group increased to 1.3 times and 3.1 times of the control group,while the kaolin group increased to 5.4 times and 4.2 times.(2)The optimal ratio of cyanobacteria-clay inoculum was 1:500,and the physicochemical properties of clay-type artificial biocrusts were significantly improved compared with those of the control group.Compared with the control group,the maximum thickness of montmorillonite artificial biocrust increased by 2.49 mm,the content of chlorophyll a increased by 4.8 times,and chlorophyll fluorescence parameter(Fv/Fm)increased to 0.08,while the above three indexes increased by 1.3,1.93 and 1.3 times,respectively,in the kaolin group,which proved that the optimization effect of kaolin artificial algal crust was better.(3)Algal filament could easily pass through or extend to adjacent sand grains from inside or on the surface of kaolin cluster,secreting exopolysaccharide to cement kaolin,bacteria and sand grains to form agglomerate-like structure,delaying precipitation infiltration and improving water utilization ratio.With the optimization of the physical and chemical properties,microbial community diversity and abundance were improved in biocrust layer,and the microbial assemblage with cyanobacteria and actinobacteria as the dominant groups was formed to jointly repair the ecology of soil surface.In conclusion,clay minerals can effectively promote the formation and rapid development of artificial biocrusts,and improve the water and fertilizer retention capacity.This study provides a theoretical basis and an effective and feasible method for rapid establishment of artificial biocrusts desert area.