Elevated CO weakens the shift in bacterial community structure in response to 8-year soybean straw return in the same experiment.

A potentially important source for soil organic carbon (SOC) in the agricultural ecosystem is straw, straw return has been shown to affect soil bacterial communities. Facing global climate change, the response of bacterial communities to straw return will change at CO enrichment. In this study, we investigate the changes of bacterial communities in response to straw return (+straw) at elevated CO (eCO, 700 ppm) in a long-term field experiment of northeast China. Soil samples were taken in the eighth year and analyzed by high throughput sequencing. Soil bacterial communities exhibited distinct clustering according to straw return and eCO, while eCO shortened the distance of clustering between straw return and not. The relative abundances of 10 genera (, , , , , , , and ) were significantly affected by the interaction of straw × eCO. In addition, straw return significantly decreased the relative abundances of , , , and and increased that of , , and . These differential responses of genera abundances are illustrative of the susceptibility of bacterial communities and indicate their importance in evaluating the fate of exogenous C. The Clusters of Orthologous Groups (COG) analysis showed that straw return had a greater effect on the relative abundances of COG categories than eCO. The present results point to the need to focus more strongly on the turnover and storage of straw-C during a chronic straw return in the future.