Effects Of Soil Arthropods On Microbial Community During Litter Decomposition Process In The Subalpine Forests Of Western China

The detritus food chain composed of soil fauna and microbes regulates the cycle of litter carbon and nutrients,and understanding their interaction helps to deeply understand the material cycle and energy flow process of the soil detritus food chain.To understand the relationship between soil fauna and microbes in the clastic food chain during the decomposition of litters,we selected the litters of Abies faxoniana and Betula albosinensis in the subalpine forests of western Sichuan as research objects.We applied biological inhibitor(naphthalene)to expel soil fauna to participate in litter decomposition,and used high-throughput sequencing technology to study the effects of soil fauna to the composition,structure,and diversity of bacterial and fungal communities during litter decomposition from August 2016 to April 2018.The main research results are as following:(1)The two kinds of litter had the same dominant group composition.The dominant bacteria community are Proteobacteria,Actinobacteria,Bacteroidetes and Saccharibacteria,the dominant fungi community are Ascomycota,Basidiomycota,Unclassified＿k＿Fungi and Ciliophora.(2)With the decomposition process of the two kinds of litter leaves,the participation of soil fauna significantly affected the diversity of bacterial and fungal communities,and the tree species significantly affected the diversity of the microbial communities of litter.The interaction between sampling time and soil fauna exclusion significantly affected the shannon,ace and chao1 diversity indices of bacterial communities.Tree species,sampling time,and interactions between soil fauna and their three factors all have significant effects on the fungal community shannon and simpson diversity indices.There are significant differences in the bacterial and fungal community structure between the growing season and the non-growth season.(3)Soil fauna had a significant effect on the bacterial community structure of litter leaves of Betula albosinensis,but no significant effect on the bacterial community structure of litter leaves of Abies faxoniana.Compared with the bacterial community in the soil fauna excluded treatment(relative abundance> 1%),soil fauna excluded treatment increased the Gemmatimonadetes phylum of the Betula albosinensis litter bacterial community,and decreased the relative abundance of the Cyanobacteria phylum and Kineosporia genus.However,there was no significant difference between the levels of soil fauna inclusion and expulsion in the Abies faxoniana litter.Soil fauna had no significant effect on the fungal community structure in the litter of Betula albosinensis and Abies faxoniana.Compared with the fungal community of soil fauna exclusion,soil fauna inclusion increased the relative abundance of LKM15 and Nuleariida phylum,and reduced the relative abundance of Unclassified＿o＿pleosporales and Aureobasidium in fungal community.(4)SEM analysis showed that soil arthropods and microbial community structure have a significant positive direct effect,and soil arthropods can indirectly affect bacterial and fungal communities by regulating the content of refractory components and nutrient elements in litter.Specifically,soil arthropods have a significant positive effect on the content of nutrient elements(C,N,P)in litter leaves.These nutrient element changes have a significant negative effect on the bacterial community structure,that is,the higher the nutrient element content,the bacterial community The lower the diversity;the content of refractory substance(lignin,cellulose)has a significant positive effect on the bacterial community structure,that is,the higher the content of refractory substance,the higher bacterial community diversity.The bacterial community structure of litter leaf of Betula albosinensis was significantly affected by the content of C,P and lignin,and the litter leaf of Abies faxoniana was significantly affected by the content of P and lignin.(5)The content of refractory components has a significant negative effect on the fungal community structure,that is,the higher the content of refractory components,the lower fungal community diversity.The community structure of litter fungi in Betula albosinensis was significantly affected by lignin content and p H value of litter leaves,while in Abies faxoniana leaves was not significantly affected by substrate characteristics.In short,the effects of soil fauna on microbes are affected by differences in tree species.In comparison with conifer species,the microbial community of broad-leaved litters is easily affected by soil fauna.Soil fauna and microbes have significant direct and indirect effects.