Study On Spatio-temporal Variation Of Soil Microbial Community Of Mao'er Mountain In Guangxi

This study was carried out in Mao'er Mountain National Nature Reserve of Guangxi Zhuang Autonomous Region,and the plot was set on different altitude.Four typical vegetation zones were selected,they were Central-Subtropical Evergreen broad-leaved forest(EBF,1145m),Fagus longipetiolata natural forest(NF,1468 m),Evergreen deciduous broad-leaved mixed forest(DBF,1536 m)and Coniferous broad-leaved mixed forest(CBF,1971 m).Conventional chemical analysis techniques,Biolog-Eco plates and Illumina Hiseq 2500high-throughput sequencing techniques were used in this study.Three aspects such as soil enzyme activities,carbon source utilization characteristics of soil microbial and composition of soil microbial community were studied in this research to reveal the temporal and spatial characteristics of soil microbial community in Maoer Mountain.The spatio-temporal variations of functional diversity and community composition of soil microbial communities and its environmental factors such as climate,soil and vegetation were compared in this study.The main conclusions are as follows:(1)There was a spatio-temporal heterogeneity of soil physical-chemical properties and enzyme activity in typical vegetation zones.In different seasons,soil water content,organic matter,total nitrogen,available nitrogen,available phosphorus and available potassium were the highest in high altitude zone,but there were no obvious regular change.There was a monotonously increase of the annual average activities of soil Phosphatase and Catalase with the increase of altitude.The activities of Urease and Invertase decreased monotonously with elevation.The activity of Polyphenol oxidase showed a single peak trend with the increase of altitude.Elevation was negatively correlated with soil Urease and Invertase activities in an extremely significant level.Except soil total potassium,other soil nutrients have a significant or extremely significant negative correlation with Urease and Invertase.There was a significantly negative correlation between soil p H and Catalase.Soil water content have significant and extremely significant negative correlation with Invertase and Urease.Thecorrelation of mean annual temperature(MAT)with Phosphatase and Urease were significant.There was an extremely significant negative correlation between mean annual precipitation(MAP)and Catalase,an extremely significant positive correlation with Polyphenol oxidase.(2)There was a spatio-temporal heterogeneity of soil microbial functional diversity in typical vegetation zones.There was a monotonously decrease of the soil microbial functional diversity with the increase of altitude in spring,autumn and winter,a single peak trend in summer.The soil microbial functional diversity indexes showed the same change rules as Average well color development(AWCD).Amino acids,Amines and Esters were the relatively high utilized carbon sources and the utilization of Carbohydrates and Alcohols were relatively low.The change of soil microbial carbon source utilization pattern was consistent with that of soil AWCD at different altitudes.Vertical differences in soil microbial carbon source metabolic diversity were mainly reflected in the utilization of Carboxylic acids,Carbohydrates and Amino acids.There were seasonal difference of soil microbial AWCD among all the typical vegetation zones,follow the order of summer>autumn>spring>winter.The seasonal variation of soil microbial Shannon index was consistent with that of soil AWCD.Seasonal variation of Simpson index was in the order of autumn> summer>spring>winter.The seasonal variation of soil microbial carbon source utilization pattern was consistent with that of soil AWCD.Seasonal differences in soil microbial carbon metabolism diversity are mainly reflected in the utilization of Amino acids,Esters and Carboxylic acids.The results of Redundancy analysis,Monte Carlo test,Variation partitioning analysis and partial Mantel test indicate that mean annual temperature is the most important factor for the spatio-temporal variation of soil microbial community functional diversity.(3)There was a spatio-temporal heterogeneity of soil microbial species diversity.The number of Operational taxonomic units(OTUs)showed a monotonous decrease trend with the increase of altitude in Mao'er montain.Chao1,Shannon and Simpson diversity indexes have different trends with OTUs abundance along the elevation.Proteobacteria,Acidobacteria and Actinobacteria were the dominant phylum of soil microbial communities at different altitudes,which accounts for more that 75% of the bacterial sequences from each of the soils.Acdio bacteria was always the dominant phylotypes at different taxonomical level.Common OTUs at different altitudes account for 40%,which indicates that the composition of soil bacterial community varied greatly between different altitudes.Non-Metric Multi-Dimensional Scaling(NMDS)analysis showed that there were obviously differences among different altitudinal sites,except for EBF and NF.Multi Response Permutation Procedure(MRPP),Multivariate ANOVA based on dissimilarities(Adonis),Analysis of similarities(Anosim)and Analysis of molecular variance(Amova)results showed that the composition of soil bacterial community between EBF and NF sites were similar.Beta-diversity indexes such as Jaccard and Bray-Curtis showed that there was a significant elevational distance-decay patterns of the soil bacterial diversity on Mao'er mountain.The number of OTUs was the highest in autumn and lowest in summer,but the Shannon and Simpson indexes were the highest in summer and lowest in autumn,Chao1 index was the highest in summer and lowest in spring.Common OTUs at different seasons account for 30%,which indicates that the composition of soil bacterial community varied greatly between different seasons.NMDS analysis showed that there were obviously differences among summer and other seasons,but the results of MRPP and Anosim analysis showed the differences were not significant.Principal component analysis(PCA)showed that seasonal differences in soil microbial community composition are mainly reflected in the relative abundance of Actinomycetes,Acidobacteria,Chloroflexi and WD272.The results of Canonical correspondence analysis(CCA),Monte Carlo test and regression analysis showed that soil available phosphorus and soil water content are the most important factors for the spatial and temporal variation of soil microbial community structure.This study indicates that the spatio-temporal variation of soil microbial community of Mao'er mountain is significantly different.Mean annual temperature is the most important factor for the spatio-temporal variation of soil microbial community functional diversity;soil available phosphorus and soil water content are the most important factors for the spatio-temporal variation of soil microbial community structure.