Pyrosequencing of soil microbial communities under ambient CO2 and elevated CO2 after 12 years on grazed grassland.

We used pyrosequencing based analysis of the 16S rRNA genes to identify changes in the microbial communities and 17,912 high quality sequences were obtained. The results showed the overall microbial community structure, diversity and abundance had no significant differences between treatments. The dominant phyla still were Actinobacteria, Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, accounting for more than 85% of the total microbial 16S rRNA sequence reads. Noteworthy, we found a 50% increase in relative abundance of the phylum Planctomycetes at eCO2, especially in genus Singulisphaera, Plantomyces and Blastopirellula, which were closely related to soil organic matter turnover. Besides, a small portion of taxa (e.g. 7.7% of the total at the genus level) significantly shifted in relative abundance in soils from eCO2. However, the force of such dynamic variations was not strong enough to drastically differentiate the whole microbial communities from aCO2. It indicated that microbial communities holds the resistance and resilience to the influence of 12-year CO2 enrichment, despite substantial changes in soil functions, pools and fluxes under eCO2 documented in prior studies. Our results provide useful insights into the understanding of global climate change implications on soil ecosystems with grazing animals.