Warming rather than elevated CO2 shifts the rhizobacterial community composition in four maize‐growing soils

Climate change may fundamentally affect the microorganisms in the rhizosphere that drive soil C and nutrient cycles. This study aimed to clarify the response of rhizobacterial community to warming and elevated CO2 (eCO2) in typical maize (Zea mays L.)‐growing soils. Under climate change, the shift of rhizobacterial community composition was assumed to be different among soils, which would be associated with the C sequestration and stability in soils. Using open‐top chambers to mimic climate warming and eCO2, we examined the taxonomic composition of bacterial communities in the rhizosphere of maize grown in four farming soils (Acrisol, Fluvisol, Kastanozem, and Phaeozem). Warming decreased the richness of the rhizobacterial community by 3.8% across the soils, but eCO2 did not significantly alter community richness. The shift in bacterial community composition was greater under warming than under eCO2, and the shift was different among soils. The abundance of Streptomyces and Gaiella significantly increased in Phaeozem and Acrisol in response to warming but not in Fluvisol or Kastanozem. Sphingomonas was suppressed in Phaeozem under warming, whereas Sphingomonas, Shinella, and Rhodospirillaceae_norank were enriched in the other three soils. Soil chemical characteristics including nitrate, Olsen P, available K, and soil organic C (SOC) were significantly associated with a number of dominant operational taxonomic units. These results indicate that the effect of warming on bacterial community composition in the rhizosphere of maize may be stronger than the effect of eCO2. Climate change led to various changes in the rhizobacterial community composition among soils that might be associated with the quality of SOC and nutrient status in different soils. Core Ideas Warming rather than eCO2 decreased the richness of the rhizobacterial community. The shift in bacterial community composition was greater under warming than under eCO2. The shift of bacterial community in response to climate change was different among soils.