Differential responses of soil bacterial communities to elevated CO₂ between strongly CO₂-responsive and weakly...

Effects of elevated CO₂ (eCO₂) on paddy soil microbial communities remain unclear, particularly when different rice cultivars exposed to eCO₂. We thus compared responses of soil bacterial communities to ambient CO₂ (aCO₂) and eCO₂ (aCO₂ + 200 μmol CO₂ mol^-1) between two weakly CO₂-responsive (Wuyunjing27, W27; Huaidao5, H5) and two strongly CO₂-responsive rice cultivars (Yongyou1540, Y1540; LongIIyou1988, L1988) throughout six growth stages (early tillering, late tillering, jointing, heading, grain filling and ripening) in a paddy field in Jiangdu, China in 2018. No significant changes in soil bacterial diversities were observed between eCO₂ and aCO₂ or between cultivars for any single growth stage at the OTU level, but α diversity significantly changed at the phylum level except for the ripening stage. For a single cultivar, particularly two strongly CO₂-responsive cultivars, over their whole growth stage, eCO₂ enhanced differences in bacterial β diversity at both OTU and phylum levels under H5, Y1540 and L1988. Soil bacterial community complexity at the phylum level under eCO₂ was weakened under W27, H5 and Y1540, but enhanced under L1988. eCO₂-induced changes in soil DOC under these four cultivars had significantly positive impact on bacterial abundances. However, structural equation modeling illustrated that changes in soil DOC induced by eCO₂ significantly decreased soil bacterial community richness. eCO₂ did not significantly affect relationships between soil bacterial community diversities and rice yields, but displayed significantly negative correlations between strongly CO₂-responsive rice cultivars' yields and relative abundances of Proteobacteria at the ripening stage. Dynamics that how soil microbial communities can differentiate their eCO₂ responses between strongly- and weakly-responsive rice cultivars will provide a new insight into promoting rice productivity and soil health.