Rising atmospheric CO2 levels are predicted to have major consequences on C cycling and the functioning of terrestrial ecosystems. Experimentation during the last two to three decades using a large variety of approaches have provided sufficient information to conclude that the enrichment of atmospheric CO2 may have severe impact on the terrestrial ecosystems. These changes are due to the increased photosynthetic activity which is expected to influence vegetation dynamics. As the majority of life in soil is heterotrophic and dependent on the input of plant-derived carbon, the activity and functioning of soil organisms will greatly be influenced by changes in the atmospheric CO2 concentration. In this chapter, we examine the current state-of the art with the respect to effect of elevated CO2 on the path of fixed C (C) into soilborne communities and resulting feedbacks on ecosystem function. On the basis of existing information, we conclude that the main effects of elevated CO2 are on the arbuscular mycorrhizal fungi (AMF) functionality and on the rhizosphere bacterial and fungal microbial community structure. There is no direct effect on the microbial community of the bulk soil. In particular, we have explored the impact of these changes on the rhizosphere interactions and ecosystem processes including food web interactions.