Research On The Distribution Pattern And Diversity Maintenance Mechanism Of Soil Fungi In The Yellow River Delta

The distribution pattern and maintenance mechanism of fungal diversity are the key areas of ecological research.In this paper,taking the Yellow River Delta as the study area,based on high-throughput sequencing technology,using molecular ecological network and Null analysis methods,to explore the distribution pattern and influencing factors of soil fungal communities under different salinity gradients,to reveal the maintenance of soil fungi diversity mechanism.The main conclusions are as follows:(1)With the decrease of soil salinity,soil quality has a trend of continuous improvement.The contents of soil total nitrogen and organic matter increased with the decrease of soil salinity.Pearson correlation analysis showed that soil electrical conductivity(salinity)was significantly negatively correlated with soil total nitrogen and organic matter(r =-0.63,P<0.01;r =-0.69,P<0.01).(2)The Yellow River Delta is rich in soil fungal resources.1368200 effective sequences were obtained from 57 soil samples,which can be classified into 8 phyla,34 classes,and 201 genera.At the level of phylum classification,the relative abundance of Ascomycota in soils with different salinity gradients was the highest(67.82?75.87%);At the class classification level,Dothideomycetes was the most dominant fungal class in extremely heavy saline soil and heavy saline soil(17.69%,34.23%).The abundance of Sordariomycetes was the highest in moderately saline soil,salinized soil,and non-salinized soil(23.62%,31.97%,42.8%);At the level of genus classification,the most dominant fungi in extremely heavy saline soil,heavy saline soil,and moderate saline soil were Aspergillus(14.99%),Cladosporium(16.25%)and Mortierella(9.47%),respectively.In salinized soil and non-salinized soil,the most dominant fungal genus was Chaetomium(14.96%,25.68%).A total of 19 differential indicator species were found in different salinity soils,including 8 in non-salinized soil,5 in salinized soil,4 in heavy saline soil,2 in extremely heavy saline soil,and no differential indicator species were found in moderate saline soil.(3)Soil salinity significantly affected the Alpha diversity of fungal communities.The diversity of soil fungi(Shannon,Simpson)increased with the decrease of salinity.The richness of soil fungi(Chao1,ACE)was the highest in moderate saline soil,followed by non-salinized soil,salinized soil,extremely heavy saline soil,and heavy saline soil.In the same salinity gradient,the fungal community structure was similar among different halophytic vegetation,while the fungal community structure was quite different in different salinity gradients.(4)Molecular ecological network analysis showed that reducing the soil salinity gradient will expand the network scale,increase the number of network connections,and make the network structure more complex.Fungal OTUs(Operational Taxonomic Units)were more likely to exist in the form of symbiosis or symbiosis.Ascomycota might be the most important key species in the saline soil region of the Yellow River Delta,which play an important role in maintaining the stability of fungal communities.(5)Mantel test showed that electrical conductivity,total nitrogen,and organic matter had significant effects on community structure(r=0.29,P<0.01;r=0.23,P<0.01;r=0.21,P<0.05).There was a typical distance-attenuation relationship in soil fungal community similarity(r=-0.82,P<0.001),that was,fungal community similarity decreases with the increase of geographical distance.The results of the Null model analysis showed that deterministic process and random process jointly driven the construction of soil fungal community in the Yellow River Delta,but the stochastic process played a dominant role(89.39?100%),and the influence of the deterministic process was weak(0?10.61%).