Description:
<jats:title>Abstract</jats:title><jats:p>Rising atmospheric CO<jats:sub>2</jats:sub> concentration directly stimulates plant productivity and affects nutrient dynamics in the soil. However, the influence of CO<jats:sub>2</jats:sub> enrichment on soil bacterial communities remains elusive, likely due to their complex interactions with a wide range of plant and soil properties. Here, we investigated the bacterial community response to a decade long preindustrial‐to‐future CO<jats:sub>2</jats:sub> gradient (250–500 ppm) among three contrasting soil types using 16S rRNA gene amplicon sequencing. In addition, we examined the effect of seasonal variation and plant species composition on bacterial communities. We found that Shannon index (<jats:italic>H</jats:italic>’) and Faith's phylogenetic diversity (PD) did not change in response to the CO<jats:sub>2</jats:sub> gradient (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.01, <jats:italic>p</jats:italic> > 0.05). CO<jats:sub>2</jats:sub> gradient and season also had a negligible effect on overall community structure, although silty clay soil communities were better structured on a CO<jats:sub>2</jats:sub> gradient (<jats:italic>p</jats:italic> < 0.001) among three soils. Similarly, CO<jats:sub>2</jats:sub> gradient had no significant effect on the relative abundance of different phyla. However, we observed soil‐specific variation of CO<jats:sub>2</jats:sub> effects in a few individual families. For example, the abundance of <jats:italic>Pirellulaceae</jats:italic> family decreased linearly with CO<jats:sub>2</jats:sub> gradient, but only in sandy loam soils. Conversely, the abundance of <jats:italic>Micromonosporaceae</jats:italic> and <jats:italic>Gaillaceae</jats:italic> families increased with CO<jats:sub>2</jats:sub> gradient in clay soils. Soil water content (SWC) and nutrient properties were the key environmental constraints shaping bacterial community structure, one manifestation of which was a decline in bacterial diversity with increasing SWC. Furthermore, the impact of plant species composition on community structure was secondary to the strong influence of soil properties. Taken together, our findings indicate that bacterial communities may be largely unresponsive to indirect effects of CO<jats:sub>2</jats:sub> enrichment through plants. Instead, bacterial communities are strongly regulated by edaphic conditions, presumably because soil differences create distinct environmental niches for bacteria.</jats:p>