【摘要】 为研究泰山不同造林树种凋落物叶分解对细菌群落的影响。以泰山4种主要优势造林树种刺槐(Robinia pseucdoacacia)、麻栎(Quercus acutissima)、油松(Pinus tabulaeformis)和赤松(Pinus densiflora)为研究对象,采用凋落物分解袋法及Illumina Miseq测序平台对细菌16S rDNA V4—V5区扩增产物进行双端测序,分析了4种树种叶片凋落物分解对细菌群落结构及多样性的影响。结果表明:(1)4种树种叶片分解速率差异显著(P<0.05),刺槐分解速率显著高于其他3个树种(P<0.05),表现为刺槐>赤松>油松>麻栎。(2)4种叶凋落物分解一年后化学元素含量与初始化学元素相比均存在显著差异。C、木质素含量均显著降低(P<0.05);N、P含量显著升高(P<0.05)。(3)所有样品一共获得643440条有效序列,分属于35门,92纲,121目,246科,410属,206种。细菌群落NMDSβ-多样性分析显示除油松和赤松间差异较小外,其他树种间差异程度均较大。其中,细菌群落相对丰度在5%以上的优势类群是变形菌门、放线菌门、拟杆菌门、酸杆菌门,且在4种处理之间差异显著(PSymbol|@@0.05)。在纲水平上,α-变形菌纲、β-变形菌纲、不明放线菌纲、鞘脂杆菌纲、γ-变形菌纲、δ-变形菌纲为主要的优势纲,其中不明放线菌纲和鞘脂杆菌纲差异显著(PSymbol|@@0.05)。在种水平上,Bradyrhizobium elkanii和Luteibacter rhizovicinus在4个处理中都为优势种,每个处理也都有自己所特有的优势种。(4)4个处理细菌丰富度(OUT、观测到的物种数和ACE指数)和系统发育多样性(PD指数)之间差异显著(PSymbol|@@0.05),且阔叶树种刺槐和麻栎显著高于针叶树种赤松和油松。(5)叶片凋落物性状和细菌群落NMDS分析表明,细菌群落多样性受到凋落物化学性质的影响,尤其是凋落物初始C/N比和木质素/N比。此外,在细菌群落多样性和叶片凋落物化学性质两个因素中,分解速率与凋落物化学性质相关性更大。研究结果有助于理解细菌群落结构和多样性对森林生态系统叶片凋落物分解的影响。更多还原

【Abstract】 The aim of this study was to identify the effects of leaf litter decomposition on bacterial community structure in the leaf litter of different tree species in Mount Tai.Four different dominant tree species Robinia pseucdoacacia(RP), Quercus acutissima(QA), Pinus tabulaeformis(PT), and Pinus densiflora(PD) in a Yaoxiang Forest Farm were examined. Illumina high-throughput sequencing of the 16 S rDNA genes was performed to analyze the effects of leaf litter decomposition on the bacterial community structure of four dominant tree species in Mount Tai. The results showed that:(1) leaf litter decomposition rates differed significantly among the four species(PSymbol|@@0.05). In all treatments, RP leaf litter was obviously decomposed faster than other three tree species(PSymbol|@@0.05). The sequence of decomposition rate was RP> PD >PT>QA.(2) After 1 year of decomposition of the four leaf litters, there was a significant difference between the current chemical element content and the initial content. Carbon and lignin contents were significantly decreased(P<0.05), whereas nitrogen and phosphorous contents were significantly increased(P<0.05).(3) A total of 643440 valid sequences were obtained for all samples, which were classified from phylum to genus in accordance with QIIME, and included 35 phyla, 92 classes, 121 orders, 246 families, 410 genus, and 206 species. The NMDS β-diversity analysis of the bacterial community showed that there was a significant difference between all species, except for PD and PT. At the phylum level, a total of four phyla were dominant(>5% across all treatments). Based on the average relative abundance, the most abundant phyla were Proteobacteria, Actinomyces, Bacteroidetes and Acidobacteria, although significant differences between the four treatments were found(P<0.05). At the class level, a wide range of classes dominated. Based on the average relative abundance, the most abundant classes were Alphaproteobacteria, Betaproteobacteria, unidentified-Actinobacteria, Sphingobacteria, Gammaproteobacteria, and Deltaproteobacteria. Unidentified-Actinobacteria and Sphingobacteria were significantly different among the four treatments(P<0.05). At the species level, Bradyrhizobium elkanii and Luteibacter rhizovicinus were the dominant species after all four treatments, each of which had its own dominant species.(4) There was significant difference between the average number of four-treated observed species, ACE and phylogenetic diversity(PD)(PSymbol|@@0.05), and these numbers in broad-leaved species were obviously higher than those in coniferous species.(5) Non-Metric Multi-Dimensional Scaling(NMDS) analysis on leaf litter characters and bacterial communities showed that the diversity of bacterial communities was affected by the chemical properties of leaf litter, especially the initial C/N ratio and lignin/N ratio of the litter; In addition, between the two factors of bacterial community diversity and leaf litter chemistry, the decomposition rate was more correlated with the chemical properties of leaf litter itself. The results of this study can improve understanding of the effects of bacterial community structure and diversity on decomposition of leaf litter in forest ecosystem.更多还原