Analysis of Microbial Community Structure and Diversity in Crop Rhizosphere Soil Based on Illumina NovaSeq Sequencing Platform

[Objectives]To make full use of crop rhizosphere microbial resources.[Methods]Illumina NovaSeq sequencing platform was used to analyze the richness and diversity of microbial community structure in rhizosphere soil of rice and maize crops in Baitu Town,Gaoyao District,Zhaoqing City.[Results]A total of 14936 OTUs of bacteria and 1905 OTUs of fungi were obtained from three samples of rice rhizosphere soil,and 13437 OTUs of bacteria and 1413 OTUs of fungi were obtained from three samples of maize rhizosphere soil.The diversity and richness of bacterial communities were higher than those of fungi.There are differences in soil bacterial and fungal communities among different crop samples.The analysis of species with bacteria difference at genus level among crop rhizosphere soil samples showed that 18 genera with significant differences were obtained from 6 samples;species analysis of fungi at the genus level showed that 3 genera with significant differences were obtained from 6 samples.[Conclusions]The research results of this paper have positive significance for the development and utilization of soil resources in Zhaoqing City and the full exploitation of rice and maize rhizosphere microbial resources.

Effects of reclaimed water irrigation and nitrogen fertilization on the chemical properties and microbial community of soil

The ecological effect of reclaimed water irrigation and fertilizer application on the soil environment is receiving more attention.Soil microbial activity and nitrogen（N）levels are important indicators of the effect of reclaimed water irrigation on environment.This study evaluated soil physicochemical properties and microbial community structure in soils irrigated with reclaimed water and receiving varied amounts of N fertilizer.The results indicated that the reclaimed water irrigation increased soil electrical conductivity（EC）and soil water content（SWC）.The N treatment has highly significant effect on the ACE,Chao,Shannon（H）and Coverage indices.Based on a 16S ribosomal RNA（16S rRNA）sequence analysis,the Proteobacteria,Gemmatimonadetes and Bacteroidetes were more abundant in soil irrigated with reclaimed water than in soil irrigated with clean water.Stronger clustering of microbial communities using either clean or reclaimed water for irrigation indicated that the type of irrigation water may have a greater influence on the structure of soil microbial community than N fertilizer treatment.Based on a canonical correspondence analysis（CCA）between the species of soil microbes and the chemical properties of the soil,which indicated that nitrate N（NO3-–-N）and total phosphorus（TP）had significant impact on abundance of Verrucomicrobia and Gemmatimonadetes,meanwhile the p H and organic matter（OM）had impact on abundance of Firmicutes and Actinobacteria significantly.It was beneficial to the improvement of soil bacterial activity and fertility under 120 mg kg^-1 N with reclaimed water irrigation.

Effects of Soil Texture on the Growth of Young Apple Trees and Soil Microbial Community Structure Under Replanted Conditions

A two-year field experiment was carried out in order to study the occurrence degree and mechanism of apple replant disease(ARD)in the apple orchards with different soil textures.So we can adopt appropriate controlmeasures according to the severity of ARD.Healthy two-year-old seedlings with consistent growth were selected,of which the root stock was T337 and the scion was Yanfu 3.There were significant differences in biomass between methyl bromide fumigation and replanted treatments,and the difference was the largest in clay loam,followed by sandy loam,and loam,which verified ARD in clay loam was most serious,followed by sandy loam and loam.Based on high-throughput sequencing of fungi in soil samples,fungal richness and diversity were the highest in clay loam,followed by sandy loam,and loam.The relative abundance of Fusarium in SX,SL,FX,FL,WX and WL was 7.33%,19.32%,2.70%,4.24%,10.71%and 23.87%,respectively.Based on Real-time quantitative analysis,there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments,i.e.,clay loam>sandy loam>loam.Fusarium was the main pathogen causing ARD.This shows that ARD is the most serious under replanted clay loam condition.High-throughput sequencing technology was used to prove the difference in Fusarium was one of the important reasons for ARD under different soil textures.This technology provides a new idea for the prevention and control of ARD.

Conversion of pure Chinese fir plantation to multi-layered mixed plantation enhances the soil aggregate stability by regulating microbial communities in subtropical China

Background:Soil aggregates are the basic units of soil structure,and their stability is a key indicator of soil quality and capacity to support ecosystem functions.The impacts of various environmental factors on soil aggregates have been widely studied.However,there remains elusive knowledge on the synergistic effects of changing forest stand structure on soil aggregate stability(SAS),particularly in subtropical China where soil erosion remains a critical issue.Methods:We investigated variations in the components of soil humus(HS),including humic acids(HAs),fulvic acids(FAs),and humins(HMs),under pure Chinese fir(Cunninghamia lanceolata)plantation(PP)and multilayered mixed plantation(MP)comprising C.lanceolata,Castanopsis hystrix,and Michelia hedyosperma.The state of soil aggregate stability,was determined by three separate methods,i.e.,dry-sieving,wet-sieving,and the Le Bissonnais.High-throughput sequencing was used to determine the diversity and composition of microbial communities under PP and MP.We then built partial least squares path models(PLS-PM)for assessing the responses of SAS to the variations in soil microorganisms and HS components.Results:The MP stands had significantly greater SAS(P<0.05),higher content of HAs and more rapid organic matter humification within aggregates,than the PP stands.High-throughput sequencing confirmed that the Pielou andα-diversity index values(Chao1 and Shannon)for fungi were all significantly higher under MP than under PP,while no marked difference was found in bacterialα-diversity between the two plantation types.Moreover,there were markedly greater abundance of three bacterial phyla(Verrucomicrobia,Chloroflexi,and Gemmatimonadetes)and three fungal phyla(Ascomycota,Kickxellomycota,and Glomeromycota),and significantly less abundance of two bacterial phyla(Planctomycetes and Firmicutes)and four fungal phyla(Basidiomycota,Mortierellomycota,Mucoromycota,and Rozellomycota)under MP than under PP.The Chloroflexi and Ascomycota phyla appeared to be the primary drivers of soil aggregate distribution.Our findings revealed that the promotion of SAS under MP was mainly driven by increased soil organic matter(SOM)content,which altered bacterial communities and enhanced fungal diversity,thereby increasing HAs content and the rate of organic matter humification.Conclusions:Considering the combined effects of enhanced soil quality,productivity,and relevant economic costs,introducing broadleaved tree species into Chinese fir plantations can be an effective strategy for stabilizing soil structure against erosion in subtropical China.Our study elucidated the controls on variations of SAS in Chinese fir-dominated plantations and demonstrated the benefit of converting pure Chinese fir plantation to multi-layered mixed plantations in increasing soil structural stability and improving site quality.

Microbial Diversity in Rhizosphere Soil of Cotinus coggygria Based on High Throughput Sequencing

In order to reveal the influence of different plant configurations on the microbial community structure and diversity in rhizosphere soil of Cotinus coggygria in Fragrant Hills park,the ITS+5.8S rDNA gene and 16S rDNA gene V3-V4 region sequencing analysis for fungi and bacteria,respectively,were conducted by high throughput sequencing(Illumina MiSeq).The results showed that the fungal diversity in the rhizosphere soil samples of C.coggygria in Fragrant Hills park in 2018 was significantly higher than that in 2016,and it was higher in the rhizosphere soil of healthy C.coggygria in Xunlupo than that in diseased ones in 2018.Verticillium dahliae,which is the causal agent of C.coggygria wilt,was detected in five soil samples.In 2018,the bacterial diversity in the rhizosphere soil of diseased C.coggygria in Xunlupo was the lowest,while it was the highest in the rhizosphere soil of healthy C.coggygria under Platycladus orientalis in Langfengting.

Competitive adsorption and mobility sequence of heavy metals in urban soils of southeastern China

Heavy metals can be introduced into urban soils at the same time. Therefore, their selective retention and competitive adsorption by the soils become of major importance in determining their availability and movement throughout the soil. In this study, the availability and mobility of six heavy metals in eight urban soils collected from different cities of Zhejiang Province, southeastern China were assessed using distribution coefficients（Kd） and retardation factor（Rf）. The results showed that there were great differences in the Kd and Rfamong the tested soils. The adsorption sequences were Cr〉Pb〉Cu〉Cd〉Zn〉Ni, and the Kd decreased with increasing levels of metal addition. Ni generally has the lowest Rf values followed closely by Cd, and Zn whereas Cr and Pb reached the highest values. The results suggest that Ni and Zn have the highest mobility associated to the lowest adsorption, Cr and Pb present the opposite behavior. Correlation analysis indicates that soil pH, CaCO3 content, and cation exchange capacity （CEC） are key factors controlling the solubility and mobility of the metals in the urban soils.

Effect of glucose on the soil bacterial diversity and function in the rhizosphere of Cerasus sachalinensis

Most cherry orchards in China have low organic carbon content,though carbon is very important for plant growth.The changes in soil carbon and bacterial diversity were determined after different amounts of 12C-glucose were added to the rhizosphere of Cerasus sachalinensis.Soil bacteria diversity was measured using high throughput sequencing,and bacteria containing 13C-glucose were identified using DNA-SIP methods.The results demonstrated that soil microbial biomass carbon(MBC)content and the soil respiratory rate were increased at 3 and 7 days after adding glucose.The soil organic carbon(SOC)content was decreased on the 7th day in the treatment where the added glucose-C was equivalent to the MBC content.SOC content was decreased on the 15th day after adding glucose-C equivalent to five times that of the soil MBC.Compared to the controls,the relative abundance of taxa at the phylum level displayed no significant change in the treatments with glucose-C added as 10%and equal amount of soil MBC 3–30 days after treatment.However,the relative abundance of Proteobacteria increased significantly in the treatment with the addition of glucose-C equivalent to five times of soil MBC.The main changes were observed in the bacteria in several genera including A4,Flavisolibacter,Aquicella,and Candidatus Solibacter.DNA-SIP results indicated that the relative abundance of the Proteobacteria and Pseudomonas was the highest;these were the primary bacteria phylum and genus,respectively,from day 3 to day 15.In conclusion,the changing pattern demonstrated that with the addition of more glucose,the range of the bacterial communities changed more.Proteobacteria and Pseudomonas may be the bacteria promoting priming effect.

Significant changes in arbuscular mycorrhizal community and soil physicochemical properties during the saline-alkali grassland vegetation succession

Arbuscular mycorrhizal(AM)fungi are widely distributed in various habitats,and the community composition varies in response to the changing environmental conditions.To explore the response of community composition to the succession of saline-alkali land,soil samples were collected from three succession stages of Songnen saline-alkali grassland.Subsequently,the soil characteristics were determined and the AM fungi in soil samples were analyzed by high-throughput sequencing.Then,the response relationship between community composition and soil characteristics was studied by Canonical correlation and Pearson analyses.The soil properties improved with the succession of saline-alkali grassland.There was no significant difference in alpha diversity between the first and second succession stage(Suaeda glauca and Puccinellia tenuiflora,respectively),and the microbial community had a dense association network at the third stage(Leymus chinensis);in addition,each succession stage had significantly enriched amplicon sequence variants(ASVs)and functional pathways.All the soil properties except cellulase activity had significant effects on community composition.Furthermore,the pH,organic carbon,organic matter,and sucrase activity significantly correlated with alpha diversity indices.These results provide a theoretical basis for realizing the significant changes in AM fungal community and soil properties during the saline-alkali grassland vegetation succession.

Competitive adsorption of Cd, Cu, Hg and Pb by agricultural soils of the Changjiang and Zhujiang deltas in China

Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concen- tration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils.

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient(0-0.4043 g/g)in surface(5-10 cm)and subsurface(35-40 cm)petroleum-contaminated soil samples from the Dagang Oilfield,China.Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods,the bacterial diversity of the soil was studied.Subsequently,the environmental parameters were measured to analyze its relationship with the community variation.Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils,but no differences were observed in different depths of petroleum-contaminated soil.Meanwhile,many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties.Total petroleum hydrocarbon,total organic carbon,and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils.Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Metagenomic approach revealed effects of forest thinning on bacterial communities in the forest soil of Mt. Janggunbong, South Korea

The soil microbiome that plays important ecological roles in mountains and forests is influenced by anthropogenic and natural causes.Human activity,particularly harvesting or thinning,affects the soil microbiome in forests by altering environmental conditions,such as vegetation,microclimate,and soil physicochemical properties.The purpose of this study was to investigate the effects on forest thinning on the diversity and composition of the soil bacterial community.From next-generation sequencing results of the 16S rRNA gene,we examined differences in soil bacterial diversity and community composition before and after thinning at Mt.Janggunbong,South Korea.We identified 40 phyla,103 classes,192 orders,412families,947 genera,and 3,145 species from the soil samples.Acidobacteria and Proteobacteria were the most dominant bacterial phyla in the forest soil of Mt.Janggunbong.Soil bacterial diversity measures(richness,Shannon diversity index,and evenness)at the phylum level increased after thinning,whereas species-level taxonomic richness decreased after thinning.Thinning provided new opportunities for bacterial species in Chloroflexi,Verrucomicrobia,Nitrospirae,and other nondominant bacterial taxa,especially for those not found in Mt.Janggunbong before thinning,to settle and adapt to the changing environment.Our results suggested that thinning affected the diversity and composition of soil bacterial communities in forests and mountains.

Composition and Diversity of Soil Bacterial Communities along an Environmental Gradient in the Sudano-Sahelian Region of Senegal

The soils of the semi-arid Sudano-Sahelian region of West Africa have been identified as being highly vulnerable to soil degradation with impacts on their capacity to provide goods and services in which soil microorganisms participate. Unfortunately, soil microbial diversity from this semi-arid region with high rainfall variability remains largely unexplored. The aim of the present study was to characterize the diversity and composition of the soil bacterial communities and to identify factors involved in their spatial distribution along an environmental gradient in Senegal. Samples were collected from non-anthropogenic sites across four pedoclimatic zones. Bacterial communities were characterized using next-generation sequencing and soil physico-chemical parameters were determined. Our results showed that Firmicutes, Actinobacteria, Proteobacteria, Chloroflexi, Gemmatimonadetes, Acidobacteria, and Verrucomicrobia phyla were predominant in the soils of the region. Bacterial α-diversity was stable along the environmental gradient whereas β-diversity highlighted significant changes in the composition of the soil bacterial community. Changes were driven by shifts in the relative abundance of OTUs belonging mainly to the genus Bacillus, Conexibacter, Kaistobacter, Solirubrobacter, Ktedonobacter, Sphingomonas, Microvirga, Rubrobacter and Pelobacter. Soil properties like pH, soil moisture and clay content were the environmental parameters identified as drivers of the composition of the bacterial communities in the semi-arid Sudano-Sahelian region of Senegal (West Africa).

Survey of Annual and Seasonal Fungal Communities in Japanese <i>Prunus mume</i>Orchard Soil by Next-Generation Sequencing

Fungi play a vital role in the management of soil environment. Although various fungal communities are found in soil, it is difficult to determine the fungal community structure in soil. In this study, we conducted a comprehensive survey of fungal communities in Japanese Prunus mume orchard soil from 2010 to 2012 growing seasons using next-generation sequencing technology. Fungal DNA was directly extracted from the soil samples and the internal transcribed spacer 1 region was amplified by PCR and sequenced. We identified 34,826 fungal clone sequences from the soil samples. The fungal clones were sorted into 2132 operational taxonomic units and a majority of the discriminated clone sequences were classified as Ascomycota and Basidiomycota. The number of fungal species belonging to Ascomycota showed increases in June in the three growing seasons. That belonging to Glomeromycota showed increases in August in the three growing seasons. As Ascomycota fungi are wood decomposers and saprotrophs, the results suggested that the number of plant pathogenic fungi increased in Japanese P. mume orchard soil in June. These findings show for the first time the annual and seasonal fungal community structures in Japanese P. mume orchard soil, and are expected to provide valuable clues for improvement when planting new P. mume trees in Japanese orchards.

16S rRNA Gene-Based Metagenomic Analysis of Soil Bacterial Diversity in Brazzaville, Republic of the Congo

Soil contains a great diversity of microorganisms, among which are bacteria. This study aimed to explore bacterial diversity in soil samples in Brazzaville in the Republic of the Congo. Environmental DNA was extracted. The illumina MiSeq sequencing was held and the diversity indices have been computed. Illumina MiSeq sequencing revealed 21 Phyla, four of which were abundant: Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes. Soil microbial communities in the studied samples were phylogenetically diverse but with a stable community structure. 17 classes are represented with relative abundances of Rihzobiales, Bacillales, Actinomycetales and Acidobacteriales. 40 families, the Alphaproteobacteria, the Bacilli and the 12 Actinobacteria. 83 orders among which the Rhizobiales are the most abundant followed by Bacillales and the least abundant followed by the Flavobacteriaceae. Of the 28 genera listed, the Bradyrhizobium is the most dominant in Mw3 and Mw4. 25 listed species, Bradyrhizobium, Bacillus, Actinoplanes, and Candidatu coribacter Acidobacterium are the most abundant species. The Shannon indices of Mw3 and Mw4 are equal, the H’max of Mw4 is greater than the H’max of Mw3. The Simpson index of Mw4 is equal to the Simpson index of Mw3, and the Pielou index (J) of Mw4 is less than the R of Mw3, but very close. This study opens interesting perspectives on the knowledge and exploitation of telluric bacteria in several areas of life.

Impact of Different Rates of Nitrogen Supplementation on Soil PhysicochemicalProperties and Microbial Diversity in Goji Berry

Goji berry(Lycium barbarum L.)is substantially dependent on nitrogen fertilizer application,which can signifi-cantly enhance fruit yield and Goji berry industrial development in Ningxia,China.This study aimed to analyze the functions of differential nitrogen application rates including low(N1),medium(N2),and high(N3)levels in soil microbial community structure(bacterial and fungal)at 2 diverse soil depths(0-20,20-40 cm)through high-throughput sequencing technology by targeting 16S RNA gene and ITS1&ITS2 regions.All the observed physicochemical parameters exhibited significant improvement(p<0.05)with increased levels of nitrogen and the highest values for most parameters were observed at N2.However,pH decreased(p<0.05)gradually.The alpha and beta diversity analyses for bacterial and fungal communities’metagenome displayed more similarities than differences among all groups.The top bacterial and fungal phyla and genera suggested no obvious(p>0.05)differences among three group treatments(N1,N2,and N3).Furthermore,the functional enrichment analysis demonstrated significant(p<0.05)enrichment of quorum sensing,cysteine and methionine metabolism,and transcriptional machinery for bacterial communities,while various saprotrophic functional roles for fungal communities.Conclusively,moderately reducing the use of N-supplemented fertilizers is conducive to increasing soil nitrogen utilization rate,which can contribute to sustainable agriculture practices through improved soil quality,and microbial community structure and functions.

巨菌草对宁夏中度盐碱地土壤酶活性、微生物群落结构和功能多样性的影响

【目的】探究种植巨菌草后中度盐碱地的根际微生物群落结构和多样性,为利用巨菌草改良宁夏中度盐碱地提供依据。【方法】采用微量法测定土壤酶活性,采用高通量测序法测定土壤细菌及真菌的群落结构及功能多样性。【结果】种植巨菌草后,土壤容重下降8.96%,含盐量下降71.90%,有机质含量上升35.25%,碱解氮含量下降56.20%,有效磷、速效钾含量分别上升81.97%和2.51%,改良后土壤碱性磷酸酶、蔗糖酶活性分别上升16.87%和6.14%,种植巨菌草后土壤真菌Simpson指数、Shannon指数与对照组之间存在显著差异。在群落结构方面,种植巨菌草增加了绿弯菌门、粘菌门、疣微菌门、担子菌门、霉菌门、芽枝霉门、毛霉门、油壶菌门和罗兹菌门的相对丰度。微生物群落OTU数上,种植巨菌草后细菌OTU数比CK增加了0.74%,真菌OTU数比CK减少了42.24%。土壤微生物群落物种差异分析表明,试验组和CK之间细菌和真菌门的类别差异较大。冗余分析表明,有机质含量、土壤碱性酶活性、有效磷含量和水溶性盐质量分数是引起种植巨菌草后根际土壤环境改变的主要因子。【结论】种植巨菌草可以提高中度盐碱地土壤酶活性和微生物多样性,改善土壤微生物群落环境。

添加不同类型水稻秸秆对植烟连作土壤微生物群落的影响

为研究添加不同类型水稻秸秆对烤烟连作土壤细菌群落的影响,以无添加土壤为对照(CK),分别添加新鲜水稻秸秆(FS)和腐熟水稻秸秆(RS),利用高通量测序分析3种处理下不同时间(0、7、30、60、90 d)土壤细菌和真菌的群落组成及多样性。结果表明,新鲜水稻秸秆和腐熟水稻秸秆能够显著提高土壤微生物群落的多样性和丰富度。FS和RS处理90 d后显著提高了土壤细菌的Chao1指数、Shannon指数和Simpson指数及真菌的Chao1指数。群落结构组成分析表明,FS和RS处理提高了变形菌门(Proteobacteria)、螺旋体门(Spirochaetes)和疣微菌门(Verrucomicrobia)的相对丰度;其中FS处理还增加了担子菌门(Basidiomycota)的相对丰度,降低了壶菌门(Chytridiomycota)和罗兹菌门(Rozellomycota)的相对丰度;RS处理增加了子囊菌门(Ascomycota)和担子菌门(Basidiomycota)的相对丰度,降低了结合菌门(Zygomycota)和壶菌门(Chytridiomycota)的相对丰度。综上所述,添加新鲜水稻秸秆和腐熟水稻秸秆均能改变土壤细菌和真菌的群落构成,改善植烟连作土壤的健康状态。相较于添加腐熟水稻秸秆处理,添加新鲜水稻秸秆处理会导致致病性真菌丰度的增加。

鄂尔多斯市不同退化程度荒漠草原土壤微生物特征分析

本研究运用Illumina MiSeq高通量测序技术系统地分析了鄂尔多斯市荒漠草原在不同退化梯度下(轻度、中度、重度、极重度、对照)土壤微生物群落的多样性和群落组成等。结果显示:(1)土壤铵态氮(65.53 mg/kg)在轻度退化下表现较好;有效磷(22.12 mg/kg)在轻度退化下表现较好;速效钾(367.73 mg/kg)和有机质(82.49 g/kg)在对照下表现较好;pH变化不明显。(2)在中度退化下的细菌和真菌ASV种类相对较多,分别为975和209,土壤真菌较细菌变化更为显著;Alpha多样性指数在中度退化时表现较好,其中,细菌和真菌群落Chao1指数分别为2 338.02和384.49,Shannon指数分别为10.28和5.80,在中度退化下均达到最高。在门分类水平上,土壤优势微生物种类相同;在属分类水平上,土壤优势微生物种类相差较大。(3)对荒漠草原土壤微生物的各项指标进行隶属函数综合分析,细菌表现为中度(0.55)>对照(0.51)>轻度(0.50)>重度(0.48)>极重度(0.47),真菌表现为中度(0.53)>对照(0.51)=轻度(0.51)>极重度(0.48)>重度(0.45)。由此可见,中度退化程度对土壤微生物影响最大,有利于促进荒漠草原区生态环境的可持续发展。

不同林龄文冠果人工林根际土壤细菌群落结构及多样性研究

为分析不同林龄文冠果(Xanthoceras sorbifolia)根系对其根际土壤细菌群落结构及多样性的影响,基于高通量测序技术,以陕西靖边地区3 a、6 a、12 a林龄文冠果人工林的土壤为研究对象,对其林下根际土壤细菌群落进行测序,并分析其结构和多样性与土壤化学性质之间的关系。结果表明:(1)优势菌门为假单胞菌门(Pseudomonadota)、放线菌门(Actinomycetota)和芽孢杆菌门(Bacillota)。(2)土壤细菌α-多样性分析发现,林龄3 a和6 a的文冠果林下土壤Chao1指数均较高,不同林龄的Simpson指数存在明显差异。(3)土壤细菌β-多样性分析发现,林龄3 a、6 a和12 a的β-多样性相互没有交叉,群落结构组成不相似,且组间具有显著差异(P<0.05)。(4)土壤细菌群落Lefse分析发现,林龄6 a土壤中黏球菌门(Myxococcota)、热脱硫杆菌门(Thermodesulfobacteriota)和Luteitalea等门、属的相对丰度显著高于林龄3 a和12 a的土壤细菌群落;林龄3 a的土壤中红杆菌属(Solirubrobacter)和芽孢杆菌属(Bacillus)的相对丰度显著高于林龄6 a和12 a;林龄12 a的土壤中Roseisolibacter的相对丰度显著高于林龄3 a和6 a。(5)热图和冗余分析不同林龄土壤化学性质与细菌群落间的相关性发现,全氮、全碳、全磷、全钾、速效磷和pH与土壤细菌群落结构有显著的相关关系。基于以上结论,不同林龄文冠果人工林土壤细菌群落组成结构存在一定程度的多样性,全氮、全碳、全磷、全钾、速效磷和pH是影响这些差异的主要因子。

Effect of long-term continuous cropping of strawberry on soil bacterial community structure and diversity

Long-term monoculture leads to continuous cropping （CC） problems, which complicate agricultural production, both locally and abroad. This study contrasted the different bacterial community compositions, physicochemical properties and enzyme activities of strawberry soil subjected to CC, CC rhizosphere （CCR）, non-CC （NCC） and non-CC rhizosphere （NCCR） treatments. The soil physicochemical properties and enzyme activities were significantly reduced after long-term CC. In addition, five variation trends were observed for the 11 major bacterial genera in the soil. Sphingomonas was the only stable group among all treatments. The proportions of Novosphingobium, Rhodoplanes, Povalibacter, Cellvibrio and Stenotrophobacterdecreased after CC. The relative abundances of Pelagibius, Thioprofundum and AIIokutzneria increased only in the CC treatment. Nitrospira were more abundant in rhizosphere soil than in non-rhizosphere soil. The relative abundance of Bacillus increased after CC. Redundancy analysis revealed that Bacillus, Pelagibius and AIIokutzneria had significant negative correlations with the soil physicochemical properties and enzyme activities. Therefore, these genera may be the key bacteria influenced by the physicochemical properties and enzyme activities altered by replanting. These results indicate that long-term CC of strawberry leads to less favourable rhizosphere soil conditions, which can be understood as a stress-induced response of the bacterial community diversity. Further research is needed to determine how the quality of soil is reduced by the shift in the diversity of the soil bacterial community.