荒漠草原生物结皮演替对结皮层及层下土壤细菌群落结构的影响

Influence of biocrusts succession process on bacterial community structure of biocrustal layer and subsoils in desert steppe

为探明生物结皮演替对结皮层及层下土壤细菌群落结构的影响,采用空间代替时间序列的研究方法,以位于宁东能源化工基地的荒漠草原的不同演替阶段(藻结皮(ZB)、混生结皮(HB)和藓结皮(TB))的生物结皮和其下0~5 cm土壤为研究对象,通过Illumina NovaSeq PE250平台对细菌16S rRNA的V3-V4高变区进行高通量测序,分析了生物结皮演替过程中结皮层及层下土壤细菌α多样性和β多样性、群落结构及其与土壤理化因子的关系。结果表明:细菌α多样性指数表现出了基本一致的趋势,生物结皮下层0~5 cm土壤细菌群落的Chao1指数、ACE指数和香农指数均明显高于结皮层,但不同类型生物结皮细菌α多样性差异不显著(P>0.05);主坐标分析结果表明,不同类型生物结皮下层0~5 cm土壤中细菌OTUs相近,细菌群落物种组成结构相似;藻结皮和混生结皮细菌群落结构有一定的相似性,而藓结皮与藻结皮、混生结皮差异较大。在门水平上相对丰度最高的5个菌群分别为:放线菌门、变形菌门、酸杆菌门和芽单胞菌门和浮霉菌门,且均表现为下层0~5 cm土壤的优势菌群相对丰度高于结皮层,下层0~5 cm土壤的特有属和共有属数量多于结皮层。冗余分析结果表明,土壤有效钾、全氮和有效磷是影响生物结皮层细菌群落结构的主要因素,分别解释了21.4%、18.9%和17.4%的群落结构变化(P<0.05),而EC是影响结皮层下土壤细菌群落结构的主导因子,解释度为20.5%(P<0.05)。这些结果证实了在生物结皮演替进程中,土壤微生物的发育过程与土壤理化性质的改善相互依存,细菌群落结构组成及多样性的变化可能会促进结皮层理化性质的改善。

To verify the effects of different biological soil crusts(biocrusts)succession phases(algal crusts,mixed crusts,moss crusts)on microbial community compositions and diversities in biocrustal layer and subsoils in a desert steppe,Ningxia,China,the biocrusts and subsoils(0-5 cm)were sampled using method of space instead of time series.The high-throughput sequencing of V3-V4 fragment of bacterial 16 S rRNA was conducted using the platform of Illumina Miseq.The bacterialαandβdiversity,community structure and their relationships with soil physical and chemical factors were analyzed.The results showed that bacterialαdiversity showed a consistent trend.The Chao1,ACE and Shannon indices in the subsoil(0-5 cm)were all higher than those of biocrustal layer(P<0.05),whileαdiversity among biocrusts was not significant(P>0.05).Results of principal coordinate analysis results indicated that 0-5 cm soil beneath different biocrusts had similar bacterial OTUs,and could be categorized as one type.Bacterial community structures of algal crust and mixed crust had some similarity,but that under moss crust was significantly different from algal crust and mixed crust.The dominant bacteria community of three biocrusts and subsoils were consistent.The top-five dominant bacterial community phyla were Actinobacteria,Proteobacteria,Acidobacteria,Gemmatimonadetes,and Planctomycetes.The relative abundance of these dominant bacterial communities in subsoil(0-5 cm)were higher than that in biocrustal layer,and that of the endemic and shared genera was higher in subsoil(0-5 cm)than in biocrustal layer.Results of distance based redundancy analysis(db-RDA)indicated that soil available potassium,total nitrogen and soil available phosphorus concentrations were the main factors affecting soil bacterial community structure in biocrustal layer,and explained 21.4%,18.9%and 17.4%variances(P<0.05),respectively,whereas EC was the major factor affecting soil bacterial community structure in subsoil(0-5 cm),and explained20.5%of variance(P<0.05).These results suggested that the development of soil microorganisms and the improvement of soil physical and chemical properties were inter-dependent,and that the changes of bacterial community structure and diversity facilitate the improvement of physical and chemical properties of biocrustal layer during the process of biocrusts succession.