| Biocrusts,as a unique ecological landscape formed by long-term succession in arid and semi-arid regions,can effectively maintain the stability of sandy ecosystems.Soil microorganisms are the main components of biocrusts and play an important role in all stages of their development.The biocrusts of the Kubuqi sands are widely distributed and diverse in type.In this paper,we used amplicon sequencing technology to analyze the microbial community characteristics and their stability of biocrusts in different developmental stages and different sand-fixing vegetation in the Kubuqi sand.The main conclusions were obtained as follows.(1)In the biocrusts at different developmental stages,the bacterial communities were dominated by the phylum Cyanobacteria,Actinobacteriota,Proteobacteria and Chloroflexi,the fungal communities were dominated by the phylum Ascomycetes,Basidiomycota and Chytridiomycota,and the archaeal communities were dominated by the phylum Crenarchacota.The diversity of bacteria increased significantly with crust succession,while the diversity of fungi and archaea did not change significantly.In addition,the increase of soil organic matter increased the relative abundance of eutrophic bacteria and reduced the oligotrophic groups;the relative abundance of resistant fungi as Ascomycetes decreased,while the relative abundance of lignindegrading fungi such as Basidiomycota increased;the Archaea community did not change significantly with crust succession.(2)With the succession of biocrusts,the network of bacteria and fungi tends to be more complex,the interaction increases,and the stability of the community increases.Bacteria and fungi had the lowest proportion of positive interactions in moss crusts,while archaea were the opposite.Stochastic processes dominated the assembly of crusts microbial communities in sandy ecosystems,with the highest proportion of stochastic processes in moss crusts,homogeneous dispersal dominating bacterial communities,and the highest relative contribution of dispersal limitation processes in fungal and archaeal communities.(3)Vegetation type significantly affected bacterial diversity in algal crusts,fungal diversity did not differ significantly at all developmental stages under different vegetation,and for archaeal communities,vegetation type significantly affected archaeal diversity at all stages of crusts.Bacterial communities of bioconidia in Artemisia ordosica and Caragana korshinskii showed higher stability in response to environmental changes than in Salix psammophila,and fungal and archaeal communities of biocrusts had more complex and stable networks in Caragana korshinskii.Regardless of the differences in vegetation type or microbial species,stochastic processes were absolutely dominant in the process of community assembly,and the proportion of stochastic processes was higher in the Caragana korshinskii community than in the Salix psammophila and Artemisia ordosica communities.In conclusion,changes in microbial community characteristics and their stability during crust succession are closely related to the improvement of soil physicochemical properties,and thesis research results provide new insights for understanding the developmental mechanisms of biocrusts and desertification control in sandy ecosystems in arid and semi-arid regions. |
