不同植被群落表层土壤中细菌群落多样性

对3种不同植被群落(海桐、雪松、桂花)表层土壤中的pH、w(TOC)、w(TN)和w(TP)进行了测定,采用DGGE(变性梯度凝胶电泳)方法对各植被群落表层土壤细菌的16S rDNA V3~V6可变区扩增片段进行了分析,利用分析得到的图谱数据与表层土壤中的pH、w(TOC)、w(TN)和w(TP)进行了群落-理化因子相关性分析以及CCA(典范对应分析). 结果表明,不同植被群落表层土壤的pH和养分含量不同,其中w(TOC)和w(TN)的差异显著(P<0.05),而pH和w(TP)的差异不显著(P>0.05). DGGE图谱分析结果揭示,不同植被群落表层土壤的细菌群落结构明显不同. 聚类分析显示,海桐和雪松的细菌群落组成和结构最为相似(82%),而它们与桂花样地的相似性(55%)相对较低,桂花样地的Shannon-Wiener指数最高且与其他2个样地差异显著,雪松样地的均匀度指数最高. 相关性分析和CCA结果进一步表明,w(TOC)和w(TN)是表层土壤细菌群落结构和多样性的显著影响因素,并且植被群落可能通过其根系分泌物产生间接影响. 

Diversity of Bacterial Communities in Surface Soils under Different Vegetation Communities

Surface soils from three vegetation communities (Pittosporum tobira, Cedrus deodara, Osmanthus fragrans) were collected and their pH values, contents of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) were measured, respectively. DGGE (denaturing gradient gel electrophoresis) was employed to analyze V3-V6variable regions of bacterial 16S rDNA. Pearson correlation analysis and canonical correspondence analysis (CCA) between bacterial community data and physicochemical parameters were respectively carried out to reveal relationships between the bacterial community structure and pH, contents of TOC, TN, TP. The results showed that there were significant differences for contents of TOC and TN among different vegetation communities (P<0.05). The descending orders of the contents were as follows respectively:O. fragrans, C. deodara and P. tobira for content of TOC and O. fragrans, P. tobira and C. deodara for content of TN. The differences of pH and content of TP among sampling sites were not significant respectively (P>0.05). According to analysis of DGGE fingerprint, the bacterial community structures were different between sampling sites. Cluster analysis of bacterial community based on DGGE showed the highest similarity (82%) between bacterial communities of P. tobira and C. deodara. Both Genotypic Richness index and Shannon-Wiener index of bacterial community in O. fragrans site were the highest value, while Pielou Evenness index was the lowest one. In addition, the highest Pielou Evenness index was observed in C. deodara site. Analyses of Pearson correlation and CCA revealed that variations of bacterial community structure were mainly affected by contents of TOC and TN. Meanwhile, the surface soil bacterial community was indirectly impacted by root exudates of vegetation communities.