Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2

Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO2, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO2 (eCO(2)) through optimizing functioning of the root-soil interface. By using a labeling technique with C-13 and N-15, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO(2). These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO(2) effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO(2). The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.