| The spatial and temporal pattern of microbial community and its construction mechanism are important scientific issues in microbial community ecology.Microbial community is a key component of forest soil ecosystem structure,driving soil biogeochemical cycles and nutrient transformation processes.With the change of soil physical and chemical properties from surface to deep layer,the composition,diversity and function of soil microbial community also showed significant changes.Understanding the distribution pattern and its driving mechanism of deep soil microbial communities in forest communities has important theoretical and applied value for maintaining the stability of soil carbon pool and protecting biodiversity in forest ecosystems.In paper,Illumina MiSeq technology was used to analyze the characteristics of microbial community in the humus layer and 0～80 cm soil layer of Larix principisrupprechtii forest in Luya Mountain,and to explore the driving factors affecting the microbial community structure of soil profiles.The main results are as follows:(1)Distribution patterns and driving factors of bacterial and archaea communities in soil profilesThe α diversity of bacterial community decreased monotonically with the increase of soil depth,and the community composition had significant difference in soil profiles.Chloroflexi,Actinobacteria,Acidobacteria,Proteobacteria and Chloroflexi are the dominant phylum of the bacterial community.The results of RDA analysis showed that soil p H was the main factor determining the bacterial community structure in soil profiles.At the level of archaea,there were two dominant bacteria,namely Crenarchaeot and Thermoplasmatota.TC and TS were the main influencing factors of archaea community change.Molecular ecological network analysis showed that the complexity of bacterial communities in litter layer and subsurface soil(10～20 cm)was high.Proteobacteria,Acidobacteria,Chloroflexi and Actinobacteria were the key groups.(2)Distribution patterns and driving factors of protozoa and algae communities in soil profilesThe abundance,species composition,and diversity of protozoa and algae vary with soil depth.The phyla Cercozoa,Ciliophora and Conosa are the dominant phyla of protozoa community.The results of RDA analysis showed that soil water content and p H had significant effects on the structure of protozoa community.Ochrophyta and Chlorophyta account for more than 95% of the protozoa community in the soil profiles.The decrease of protozoan and algal α diversity may be related to the decrease of soil physicochemical properties and food resources with increasing depth.The results of molecular ecological network analysis of soil protozoa and algae showed that the deep soil protozoa network was more complex and the niche differentiation was stronger.(3)Relationship between bacteria,archaea and protists in soil profilesThe results of molecular ecological network analysis showed that the number of positive connections among microbial community species was much higher than the number of negative connections in the whole soil profiles,and the bacterial community occupies a key position in the microbial network in the soil profiles.The construction of protist community is mainly driven by deterministic process,while bacterial and archaea community is affected by random process.From the perspective of protozoan feeding,the bacterial detrital feeders(Group B)dominated the protozoan community structure in soil profiles,and the α diversity trend was increase,which was significantly correlated with p H,TN and TP of soil environmental factors.In conclusion,the distribution pattern of soil microbial communities along the soil profiles was obvious,and the interaction between environmental factors and microbial communities affected the distribution pattern and community construction. |
