Elevated atmospheric CO₂ generally stimulates plant photosynthesis and nutrient uptake, modifying the local and global cycling of bioactive elements. Although nutrient cations affect the long-term productivity and carbon balance of terrestrial ecosystems, little is known about the effect of CO₂ enrichment on cation availability in soil. Utilizing free-air CO₂ enrichment facilities, we conducted two field experiments to investigate the effect of elevated CO₂ (ambient + 200 μmol mol^-1) on plant growth, soil solution chemistry and microbial activities in the rice-wheat rotation system.
Results/Conclusions

Elevated CO₂ enhanced organic C allocation belowground and stimulated root and microbial respiration. Elevated CO₂ significantly increased Ca²⁺, Mg²⁺, Fe²⁺ and Mn²⁺ in soil solutions. While enhancing cation uptake of rice plants, elevated CO₂ also increased net H⁺ excretion from roots. These results indicate that over the short term, elevated CO₂ may stimulate cation release from soils and plant growth. Over the long term, however, CO₂-induced cation release may increase cation losses and depletion, constraining the productivity of terrestrial ecosystems