Heterogeneity Of Meso-micro Soil Fauna Pattern And Its Coupling With Soil Microorganisms In Temperate Zonal Forests In China

Soil fauna and soil microbes are the largest and most diverse organisms in the soil ecosystem.They are very active in the soil ecosystem,both as source and sink,and play an important role in decomposing biological residues,improving soil physical and chemical properties,promoting soil material circulation and energy conversion,and improving soil fertility.Soil fauna and microbial community composition,structure and community diversity are sensitive to habitat changes,which can objectively reflect the health and stability of the ecosystem.In this study,Xing’an Larch forest（cold temperate forest）,Changbai Mountain broad-leaved red pine forest（middle temperate forest）and Dongling Mountain deciduous broad-leaved forest（warm temperate forest）were selected as the research objects.Samples were collected in September 2019.To study the community composition,diversity and food web structure of meso-micro soil fauna in different zonal forests.The coupling relationship between meso-micro soil fauna and soil microorganisms and the response of soil fauna and soil microorganisms to environmental factors were analyzed,and a structural equation model of environment,soil microorganisms and soil fauna was constructed.The main conclusions are as follows:（1）A total of 62527 meso-micro soil fauna of 95 species were captured in this study.The dominant taxa were Mesostigmata,Oribatida and Isotomidae.The dominant taxa and common taxa were similar in species in different zonal forests,but the proportion of individual numbers was significantly different.From cold temperate forest to warm temperate forest,the number of soil fauna individuals decreased first and then increased,and the number of soil fauna groups increased.Shannon diversity index and Pielou evenness index of soil fauna community increased first and then decreased,Simpson dominance index decreased first and then increased,and Margalef richness index showed a gradually increasing trend.The Shannon index and Pielou index showed a decreasing trend with the increase of altitude.The community Beta diversity index showed that the community composition of meso-micro soil fauna in temperate zonal forests had high heterogeneity.（2）The trophic level structure of meso-micro soil fauna was studied.The results showed that different zonal forest meso-micro soil fauna groups obtained N sources in different ways.There was significant correlation between soil faunaδ¹⁵N values within different sites,but no correlation between soil faunaδ¹⁵N values between different sites.Through the classification of trophic levels of soil fauna in various regions,the results show that there are differences in different zonal forests.It can be concluded that the plot environment is the main factor affecting the trophic levels and food web of soil fauna.（3）The dominant bacteria phylum groups were Acidobacteria,Proteobacteria and Actinobacteria,etc;The dominant bacteria genera groups were Candidatus＿Solibacter,Bryobacter etc.The dominant fungi phylum groups were Basidiomycota,Ascomycota,etc.The dominant fungi genera groups were Hygrophorus,Russula,Mortierella,etc.There were significant differences in the composition and diversity of soil bacteria and soil fungi communities in temperate zonal forests.From cold temperate forest to warm temperate forest,the Alpha diversity of soil bacteria increased and the soil fungi first decreased and then increased.The Beta diversity analysis showed that the community composition of soil bacteria and soil fungi community in temperate zonal forests had high heterogeneity.（4）In different zonal forests,Shannon index of soil fauna was positively correlated with Shannon index and Simpson index of soil bacteria（r=0.68,p<0.05;r=0.58,p<0.01）.Simpson index of soil fauna was negatively correlated with Shannon index and Simpson index of soil fungi（r=-0.82,p<0.01;r=-0.56,p<0.05）.The relationship between soil fauna and soil microorganism was more significant in the middle temperate forest.The relationship between soil fauna and soil bacterial Acidobacteria did not change,but the relationship between soil fauna and Nitrospirae,Firmicutes,Rokubacteria and soil bacteria under the genus level was significantly different.The relationship between soil fauna and soil fungi basidiomycota and Rozellomycota did not change.The relationships with Blastocladiomycota,Chytridiomycota,Kickxellomycota and other soil fungi at the genus level were significantly different.（5）Soil p H、total nitrogen、total phosphorus and temperature are the most important environmental factor affecting latitude differentiation of meso-micro soil fauna communities;Soil organic matter、total nitrogen and total phosphorus are the most important environmental factor affecting the altitude differentiation of meso-micro soil fauna communities,and it is also used in Oribatida,Mesostigmata,Prostigmata,Hypogastruridae,Onychiuridae,Enchytraeida,Neanridae,Sminthuridae,Chironomidae larvae,Cecidomyiidae larvae,Diplopoda and Cantharidae larvae are significantly affected by environmental factors.Temperature and soil p H value are the main environmental factors affecting soil microbial communities.Rokubacteria,Nitrospirae,Gemmatimonadetes and Chytridiomycota are significantly affected by environmental factors.（6）The structural equation model was established to comprehensively analyze the relationship between environmental factors,microorganisms and soil fauna.The model explained 72%of the variation of soil fauna community composition and 78%of the variation of soil fauna community diversity.Soil p H,temperature and precipitation directly significantly affected soil fauna community composition,while environmental factors indirectly significantly affected soil fauna community composition by changing bacterial and fungal community composition.Temperature and precipitation directly significantly affected soil fauna community diversity.Meanwhile,temperature significantly affected soil animal diversity indirectly by changing bacterial diversity.Soil p H and soil organic carbon significantly affected soil fauna diversity indirectly by changing fungal diversity.