不同分解等级的兴安落叶松倒木细菌多样性分析

Analysis on bacterial diversity and composition of Larixg melinii fallen wood with different decomposition levels

【目的】为探究大兴安岭寒温带兴安落叶松倒木分解过程中细菌的多样性、群落结构特征以及影响因素,揭示细菌在倒木分解过程中的作用。【方法】采用空间代替时间的方法,以5级分解等级的倒木为研究对象,测定不同分解等级倒木的理化性质,应用16S rRNA基因-Illumina MiSeq高通量测序技术分析细菌多样性和群落结构特征;通过冗余分析探讨不同分解等级倒木上细菌的差异及影响因素。【结果】5个分解等级倒木的理化性质存在不同的差异,对细菌16S rDNA测序共获得1360种可操作分类单元(OTU),分属于20门47纲126目222科377属637种,其中变形菌门Proteobacteria和放线菌门Actinobacteria为各分解等级倒木细菌的主要共有优势菌,相对丰度分别为38.55%~53.39%和17.97%~41.64%;各分解等级倒木细菌的优势菌门中放线菌门呈显著性差异。倒木的各分解等级间的Alpha多样性指数中,Ace指数呈显著性差异。Beta多样性和冗余分析结果表明:5个分解等级倒木上的细菌被划分为3组,Ⅰ级和Ⅱ级倒木的细菌群落相似性较高,Ⅲ级和Ⅳ级相似性较高;优势菌门中变形菌门与总氮含量极显著负相关,与碳氮比极显著正相关;优势菌门中的放线菌门与半纤维素含量极显著正相关,与碳氮比显著正相关。【结论】各分解等级倒木上的细菌多样性和组成受倒木腐烂程度影响,随着腐烂的加剧,分解的进行,分解基质发生了改变,细菌的多样性也随之发生了变化,碳氮比是影响细菌组成和多样性的重要因素。

【Objective】In order to explore the bacterial diversity,composition structure characteristics and influencing factors of Larix gmelinii fallen wood during the decomposition process in the cold temperate zone of Daxing’an mountains,and to reveal the roles of bacteria in the decomposition process of fallen wood.【Method】The method of space substituting time was used,the fallen wood with five decomposition levels were taken as the research object,the physical and chemical properties of fallen trees were determined,the bacterial diversity and community structure characteristics were analyzed by 16S rRNA gene Illumina miseq high-throughput sequencing technology,and the bacteria differences and influencing factors on different decomposition levels of Larix gmelinii fallen wood were discussed by redundancy analysis.【Result】The results showed that there were differences in the physicochemical properties of the fallen wood at the five decomposition levels.A total of 1360 operable taxonomic units(OTU)were obtained from sequencing technology,which belonged to 20 phyla,47 classes,126 orders,222 families,377 genera and 637 species,the Proteobacteria and Actinomycota were the main common dominant bacteria of Larix gmelinii fallen wood with each decomposition level,andthe relative abundance were 38.55%-53.39%and 17.97%-41.64%,respectively;the actinomycetes was significantly different in the dominant phylum.Among the Alpha diversity index of fallen wood with the different decomposition levels,and the Ace index showed a obvious difference.The results of Beta diversity and redundancy analysis showed that the bacteria on Larix gmelinii fallen wood with the five decomposition levels were divided into three groups,the similarity were closer betweenⅠandⅡlevels of fallen wood,and he similarity were closer betweenⅢandⅣlevels of fallen wood;the Proteobacteria had an extremely significant negative correlation with the total nitrogen content,and an extremely significant positive correlation with carbon-to-nitrogen ratio.The Actinomycota had an extremely significant positive correlation with hemicellulose content of Larix gmelinii fallenwood,and a significant positive correlation with carbon-nitrogen ratio.【Conclusion】The bacterial diversity and composition of the Larix gmelinii fallen wood at each decomposition level was affected by the rotten degree.As the decay was intensified,the matrix of fallen tree was changed with the rotten and decomposition progresses,so that the bacterial diversity of Larix gmelinii fallenwood was changed.The carbon-nitrogen ratio was an important factor to affect bacteria composition and diversity.