高寒岩溶土壤微生物群落组成及其多样性

Composition and diversity of microbial communities in high-altitude karst soil

高寒岩溶是四川黄龙风景区独特的地质特征。为分析高寒岩溶区土壤微生物群落组成特征与土壤理化性质间的相关性,以黄龙风景区土壤为研究对象,对土壤细菌的16SrRNA基因序列和真菌ITS序列进行高通量测序。结果表明:不同岩溶区的土壤细菌多样性和丰富度具有显著差异,但土壤真菌差异不显著,且土壤细菌群落占主导地位;细菌群落以变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)为主;真菌群落以子囊菌门(Ascomycota)、担子菌门(Basidiomycota)为主,真菌在门和属水平的差异较大。冗余分析发现总磷和温度是黄龙风景区土壤微生物群落结构变化的重要环境因子,pH是第二重要的环境因子。

As a World Natural Heritage Site,Huanglong Scenic Area,is located in the eastern part of the Qinghai–Tibet Plateau in Songpan county,Aba Tibetan and Qiang Autonomous Prefecture,Sichuan Province.Huanglong valley is 3.50 km long,with an altitude of 3,145–3,578 m.In the Huanglong Scenic Area,there is a sixmonth freezing period,with a minimum temperature of 3℃.The main vegetation types are coniferous and broadleaved mixed forests and coniferous forests,belonging to a typical plateau temperate to subfrigid monsoon climate.This scenic area is renowned at home and abroad for its rare and colorful karst landscape.At present,there is still a research gap in the structure and function of soil microorganisms of high-altitude karst habitats.Therefore,in order to explore the characteristics of soil microbial communities in Huanglong Scenic Area−a high-altitude karst area,we compared the differences in soil microbial community structure and diversity between high-altitude karst and non-highaltitude karst areas,with typical primary karst in Guilin−a non-high-altitude karst area.By analyzing the structural characteristics of soil microbial communities and their correlation with environmental impact factors,we laid a theoretical foundation for the relationship between soil microbial communities and ecological environment in highaltitude karst areas.In this study,we collected and analyzed soil samples from Huanglong valley,the main scenic area of the Huanglong Scenic Area.A total of 27(three replicates)samples were collected and compared with the samples from the typical primary karst area in Guilin.We collected data on environmental factor,such as Total Organic Carbon(TOC),Soil Organic Matter(SOM),Total Nitrogen(TN),Total Product(TP),Temperature(T),Soil Water Content(SWC),and pH.Meanwhile,we employed high-throughput sequencing techniques such as 16SrRNA and ITS gene sequencing to perform bioinformatics analysis on sequencing data,including species diversity andβdiversity.Then,we identified the main driving factors affecting soil in the Huanglong Scenic Area through principal component analysis(PCA),and explored the relationship between environmental factors and soil microbial communities by Spearman correlation analysis and redundancy analysis(RDA).The results show that the soil pH at each sampling point in Huanglong valley indicates a neutral to alkaline property,with no significant difference.But there are significant temperature differences at various sampling points.Compared to the soil from slopes of the Yaji test site in the non-high-altitude karst area of Guilin,the SOC,SOM,and TN contents in soil at various points in the Huanglong Scenic Area are relatively higher.There are differences in the bacterial chao1 index and observed OTUs index between Guilin's primary karst area and Huanglong valley.Similarly,the ACE index of bacteria and fungi also shows differences.These results may be attributed to the influence of vegetation types,soil types,and topographical factors on the distribution of soil microorganisms.The diversity indices of Shannon and Chao1 at HJ.4 sampling point in Huanglong valley are higher than those of other sampling points,indicating the richest biodiversity in this sampling point.At a phylum level,the bacterial community is mainly composed of Proteobacteria and Acidobacteria.Ascomycota and Basidiomycota are the dominant microbial groups in the high-altitude karst habitat of the Huanglong area.At a subordinate level,the main dominant bacteria in Huanglong valley are Pseudomonas,RB41,and Candidatus_Udaeobacter,with an average abundance of 14.57%,3.11%,and 2.29%,respectively.The most dominant group in the primary karst area of Guilin is Candidatus_Udaeobacter,with an abundance of 6%.At a genus level,the dominant fungi in Huanglong valley are Humicola(22%)and Mortierella(22%).The dominant groups of the primary karst area in Guilin are Staphylococcum(5%),Absidia(5%),and Fusarium(4%).The differences in fungi at the phylum and genus levels are greater than those in bacteria.In summary,the proportion of dominant microorganisms in the primary karst area is relatively low,and the community types differ significantly compared to those in Huanglong valley.Samples collected from nine sampling points(three replicates)in Huanglong valley and in the primary karst area of Guilin show varying degrees of dispersion.UPGMA clustering analysis shows a high degree of similarity in various eukaryotic communities in Huanglong valley,while there are certain differences in the composition of prokaryotes among them.Redundancy analysis indicates that in bacteria,TP is the most correlated factor with community distribution,while T is the second most important environmental factor.In fungi,TP is also the most correlated factor,while T and pH are the second most important environmental factors.Both soil TP and T have a significant impact on the distribution of fungal and bacterial communities.