Effects 10 years elevated atmospheric CO2 on soil bacterial community structure in Sanjiang Plain, Northeastern China

This study was conducted over 10 years using an open top chamber experiment in the Sanjiang Plain to explore the impact of environmental parameters and bacterial community composition and structure under long-term conditions of elevated CO2 concentrations (eCO2, 550 μmol·mol−1). Illumina sequencing of 16S rRNA was used to determine soil bacterial communities over the long-term in the Sanjiang Plain. Vegetation characteristics and soil properties were also investigated. Dominant bacterial group was Proteobacteria, accounting for 23.52–39.03%, while there were remarkable changes in the bacterial community composition. eCO2 increased the relative abundance of Subgroup_6 and decreased those of AD3 and Candidatus_Udaeobacter. These variations might be related to gene functions. A redundancy analysis indicated that there was a strong relationship between dominant bacterial phyla and environmental factors (photosynthetic rate, aboveground biomass and stomatal conductance). Structural equation model (SEM) showed that eCO2 and year both affected the soil bacterial community. In contrast, the short-term had greater impacts on the bacterial community under eCO2 compared with the long-term via indirect effects on vegetation and soil characteristics. eCO2 affect soil bacterial community through indirect effects on soil nutrient content and vegetation characteristics in the short-term whereas showed adaptability to eCO2 in the long term.