鼎湖山不同演替阶段森林土壤细菌多样性

Bacterial diversity of different successional stage forest soils in Dinghushan

【目的】了解鼎湖山早、中、后3个演替阶段的3类森林(针叶林、混交林、阔叶林)土壤细菌群落结构及其多样性,为下一步研究不同演替阶段森林土壤微生物的功能及其与植物的相互作用提供依据。【方法】在代表性林区采集土样,从中提取总DNA,利用细菌通用引物27F和1492R PCR扩增16S rDNA并构建文库。从所构建的3个文库中各挑取150个阳性克隆子并对插入片段进行测序,利用Mothur软件对所得序列进行分析。【结果】从针叶林、混交林和阔叶林文库中分别得到122、118和120条有效16S rDNA序列,各代表70、64、72个OTUs(operational taxonomic units,以97%相似性为划分标准)。分析结果显示,共检测到8个细菌门类,其中酸杆菌门(Acidobacteria)在针叶林、混交林和阔叶林土样中分别占53.3%,67.8%和60%;变形杆菌门(Proteobacteria)分别占29.5%,20.3%和32.5%;其它如厚壁菌,放线菌等均不超过10%。3类森林土壤细菌群落结构差异显著(P<0.05),3者两两间共有的OTU数量占检测到的OTU总数的比例均低于25%,其中阔叶林土壤细菌有着最高的Chao指数(414.2)和Shannon指数(3.90),及最低的Simpson优势度指数(0.0249)。【结论】鼎湖山针叶林、混交林和阔叶林3类林区土壤细菌在种群构成上差异显著,其中阔叶林土壤细菌丰富度及多样性相对较高,但3者在大类组成方面比较相似,均为酸杆菌占绝对优势,变形杆菌次之。

[Objective]The aim of the present study was to investigate the soil bacterial diversity of pine forest（PF）,pine-broadleaf mixed forest（MF） and monsoon evergreen broadleaf forest（MEBF）,the typical forest types that represent early,middle and late successional stage forests in Dinghushan,respectively.The results obtained will also provide information for further examination of the relationship between the soil bacterial diversity and ecological function of the forests.[Method]Three total DNA samples were extracted directly from soil samples collected from PF,MF and MEBF,and then the 16S rDNA sequences were PCR amplified and the libraries were constructed,respectively.For each of the three libraries constructed,150 positive clones were picked randomly and the inserted 16S rDNA were sequenced.The soil bacterial diversity of the forests was analyzed by Mothur based on the sequences obtained.[Result]A total of 122,118 and 120 valid 16S rDNA sequences were obtained from PF,MF and MEBF,which represented 70,64 and 72 operational taxonomic units（OTUs,definition at a level of 97% similarity）,respectively.Bacteria belonging to 8 phyla were identified.Among them,Acidobacteria accounted for 53.3%,67.8% and 60%,while Proteobacteria took up 29.5%,20.3% and 32.5% in PF,MF and MEBF,respectively.The other bacterial phyla identified each accounted for less than 10%.The bacterial community structure differed significantly at species level among three soil samples（P0.05） with the percentages of the shared OTUs between any two soil samples lower than 25%.MEBF had the highest Chao index（414.2）,Shannon index（3.90） and the lowest Simpson dominance index（0.0249）.[Conclusion]The soil bacterial community structure differed significantly at species level among PF,MF and MEBF in Dinghushan,while they have a similar structure at phyla or class levels with Acidobacteria predominated followed by Proteobacteria.