Biogeographic Distribution Characteristics And Driving Factors Of Desert Soil Microbial Community In Northern China

At present,desertification in China accounted for more than 25%of the national land area,among which the land area with obvious sandy trend was 30.03 million km~2.These desertified lands are extremely vulnerable to global climate and land use type changes.Understanding the biological structure of desert ecosystems and their diversity is important for the monitoring,prediction,evaluation and management of desertification processes.As one of the essential parts of desert ecosystems,soil microorganisms play a critial role in maintaining the material transformation and energy flow of soil ecosystems,and can quickly respond to changes in soil ecosystems.However,due to the limitations of technical means and harsh natural environment,there has been a lack of systematic studies on the spatial distribution pattern of large-scale soil microbial diversity in desert ecosystems and its response to global climate change in China.In this study,desert soil samples were collected along an aridith gradient in northern China,and high-throughput sequencing technology and bioinformatics analysis were used to conduct a systematic and comparative study on the structure and diversity of soil microbial communities with different aridity gradient deserts.We also analyzed the spatial distribution of soil microbial communities in deserts at the regional scale by combining climate factors,soil physical and chemical properties,plant communities and geographical distance,and clarified the characterization of the spatial patterns of soil microbial communities and their contributing mechanisms in the deserts ecosystems of northern China.The key findings are as follows.(1)The dominant soil bacterial phyla under different aridity gradient were similar and mainly included Proteobacteria,Actinobacteria,Firmicutes,Bacteroidetes,Acidobacteria,Chloroflexi,Planctomycetes,Verrucomicrobia,Cyanobacteria,Gemmatimonadetes and Candidatus Saccharibacteria.The dominant soil fungal phyla under different aridity gradient were similar and mainly included Ascomycota,Chytridiomycota,Zygomycota,Basidiomycota,Glomeromycota and Cryptomycota.The richness and diversity of soil bacterial and fungal communities were lower in hyper-arid desert,and soil microbial communities regulated key microbial taxa by changing their relative abundance in response to changes in aridity gradients.(2)The aridity index was the main environmental factor affecting the spatial distribution of soil bacterial and fungal communities in the sandy areas of northern China.Environmental factors affecting the spatial distribution of soil bacterial communities also included total soil phosphorus,p H and vegetation diversity,and those affecting the spatial distribution of soil fungal communities also included vegetation diversity,electrical conductivity,altitude,total soil nitrogen and total phosphorus.The environmental factors affected by the spatial distribution of soil microorganisms in sandy areas of different aridity gradients differed depending on the scale of the study.(3)The similarity of soil bacterial and fungal communities in deserts of northern China decreased significantly with geographic and environmental distance,and the spatial distribution characteristics of soil microbial community composition and diversity in the deserts were driven by both historical evolutionary factors and contemporary environmental factors,and the influence of dispersal limitation on the spatial distribution of soil microbial communities in the deserts was greater than that of environmental heterogeneity on the spatial distribution of soil microbial communities in the deserts.The distance decay rate of soil bacterial communities was greater than that of soil fungal communities,and the distance decay rate was greater in sand areas with greater aridity.(4)The relative abundance of potential functional genes in soils of different aridity gradients in sandy areas differed significantly.Different combinations of carbon fixation and carbon decomposition genes were selected for different aridity gradient deserts.The relative abundance of nitrogen fixation genes was significantly higher in the dry sub-humid deserts and arid deserts than in the arid deserts and hyper-arid deserts.The relative abundance of nitrate reduction-related genes was higher than the relative abundance of other nitrogen cycle-related genes.This study has an important scientific significance for the effective utilization of soil microbial resources and the improvement of desert ecosystem management in China,and provides a scientific basis for the further understanding of the structure and function of desert ecosystems and the prediction of the response of desertified land to environmental changes.