流溪河生态公益林下土壤细菌多样性

Soil bacterial diversity in Liuxihe National Park

【背景】森林土壤细菌多样性在一定程度上是衡量森林质量的重要指标之一,土壤细菌群落结构组成及变化能够反映森林生态系统的结构和功能,在森林生态系统物质养分循环中发挥着重要的作用。【目的】以广州市流溪河国家森林公园3种不同密度林分生态公益林的土壤为研究对象,分析不同密度林分类型对土壤细菌群落结构的影响,探讨不同林分密度土壤养分和土壤细菌的分布规律,为退化生态系统的恢复、合理利用公益林土壤资源、维护地力及提高公益林生态系统生产力和服务功能提供参考。【方法】选择高密度林分(HD)、中密度林分(MD)、低密度林分(LD)3种林分类型,采用"S"形取样法采集土壤样品,提取土壤微生物总DNA,采用Illumina MiSeq高通量测序技术对16S rRNA基因进行序列测定,利用R语言和SPSS21.0等软件分析林分密度对细菌多样性及群落结构的影响。【结果】高林分密度土壤肥力状况较中低林分密度高;不同林分密度下土壤细菌多样性指数、丰富度指数略有差异,中密度林分指数最高;流溪河区域土壤细菌多样性较高,变形菌门和酸杆菌门是主要类群。【结论】流溪河生态公益林土壤细菌具有丰富的多样性,以变形菌门和酸杆菌门为主;林分密度对土壤细菌的多样性、丰富度及其群落结构产生明显影响;流溪河区域中密度林分(1 800-2 200株/hm2)更适合土壤细菌的繁衍生息;土壤的肥力状况受林分密度、灌木杂草的影响;16SrRNA基因的基因组异质性会导致对细菌多样性的过高估计。

[Background] Forest soil bacterial diversity is one of important indexes to measure forest quality. The composition and change of soil bacterial community structure can reflect the structure and function of forest ecosystem. They play important roles in the circulation of nutrients in forest ecosystems. [Objective] The influence of different forestry density on soil bacterial community structure was analyzed and discussed in Liuxihe National Park, in order to provide a reference for the restoration of degraded ecosystems, rational utilization of forestry resources, conservation of soil fertility, improvement of ecosystem productivity and service functions of forests. [Methods] A manipulative field experiment was conducted to investigate the effects of three different forest types： high density forest type（HD）, medium density forest type（MD）, low density forest type（LD）. The soil samples were collected by ＂S＂ sampling method and the total DNA of soil microbes was extracted. 16 S rRNA gene sequences were sequenced by Illumina MiSeq sequencing and analyzed using R language, SPSS 21.0 and other software. [Results] The soil fertility of high density forest was higher than those of medium and low-density forests. Soil bacterial diversity index and richness index differed among different density forests, and the highest was in middle-density forest. Proteobacteria and Acidobacteria are the major groups in Liuxihe National Park. [Conclusion] The soil bacterial diversity is abundant in Liuxihe National Park. Proteobacteria and Acidobacteria are the major groups. Soil bacterial diversity, richness and community structure were significantly affected by forest density. The medium density forest type（1 800-2 200 plants/ha） in Liuxihe National Park is suitable for bacterial growth. The fertility of soil was affected by the forest density and shrub weeds. Intragenomic heterogeneity of 16 S rRNA genes causes overestimation of bacterial diversity.