The Distribution Of Microbial Community Composition And Functional Genes For Regulating C,N And P Cycling In Zoige Peatland Soils

The Zoige peatland located in the alpine plateau had low microbial activity,resulting in slow decomposition of organic matter,accumulation of massive organic matter,and became important C sinks.As the main decomposer of organic matter,microorganisms participate in the cycling of soil carbon（C）,nitrogen（N）,and phosphorus（P）,and their functional genes and community composition play an important role in maintaining the functional stability of the ecosystem.However,in recent years,human activities and climate change may lead to changes in the structure and activities of microbial communities,which eventually affect the soil C,N,and P cycling.Therefore,it is important to reveal the distribution of microbial community composition diversity and functional genes in Zoige peatland soils for understanding the cycling of soil C,N,and P.It is expected that this study could provide theoretical information for managing the soil C sink function in peatland soils.This study chose low grazing（HN）,rotational grazing（MN）,and heavy grazing（LN）sample sites to explore the distribution of microorganisms and key functional genes in the Zoige peatland soils.In these three sampling sites,soils were collected at the beginning of the growing season（June 2020）,the end of the growing season（October 2020）,and the non-growing season（April 2021）,respectively.0-100 cm soils were sampled,with 20 cm as a sampling depth.After sampling,q PCR fluorescence quantification,high-throughput sequencing,and Smart Chip real-time PCR system were used to explore the characteristics of microbial abundance,diversity,community composition,and functional genes of C,N,and P cycling in soils.The results of this study are as follows.（1）In Zoige peatlands soils,bacterial abundance was significantly higher than fungal abundance,with a difference of 10²-10³.Bacterial and fungal abundance were highest in HN soils and decreased with soil depths,however,the season only had a significant effect on fungal abundance,showing a significantly higher non-growing season than the growing season.In this study,the bacterial communities were mainly composed of Proteobacteria,Actinobacteria,Acidobacteria,et al.The fungal communities were mainly composed of Ascomycota and Basidiomycota.Season significantly affected the bacterial community structure but not the fungi,and the bacterial and fungal communities in HN soils differed significantly from those in LN and MN soils,indicating that grazing changed the microbial community composition.Also,aerobic microorganisms decreased,and anaerobic microorganisms increased with increasing depths.（2）The results showed that Zoige peatlands contained various C fixation genes,for example,rcb L,acc A,acs A,et al.,indicating the diversity of C fixation pathways in this region.In addition,the genes regulating labile C degradation,such as amy A,apu,and xyl A,and the genes regulating CH₄ metabolisms,such as pmo A,mmo X,and mxa F were more abundant in the non-growing season.The abundance of genes involved in N fixation（nif H）,denitrification（nir S and nir K）,ammonification processes（ure C）,inorganic P solubilization（ppx）,and organic P mineralization processing（pho D）were also abundant in the non-growing season.The C fixation genes rcb L,etc.,and the P cycling functional genes ppx and pho D had the lowest abundance in the MN soils.In contrast,the abundance of N cycling functional genes such as nir S and nir K,the C degradation genes such as amy A were higher in LN and MN soils.These results indicated that grazing elevated the abundance of C degradation genes and accelerated the process of denitrification and nitrification in soil.However,grazing weakened the utilization of P and inhibited C fixation.（3）This study showed that water content（WC）and ammonia nitrogen（NH₄⁺-N）were the main factors affecting bacterial community structure,while fungal community structure was mainly influenced by p H and nitrate-nitrogen（NO₃^--N）.In addition,p H and NH₄⁺-N were the main influential factors of C cycling genes.N cycling genes were mainly affected by total soil carbon（TC）,NH₄⁺-N,and total soil phosphorus（TP）,but P cycling genes were only significantly affected by NH₄⁺-N.These results demonstrated that NH₄⁺-N might be the key environmental factor driving C,N,and P cycling in peatland soils.In general,this study demonstrated the distribution of microbial community composition and the main microbial functional genes,which may provide a certain theoretical basis for understanding the cycling function of C,N,and P in peatlands.