Microbial carbon-substrate utilization in the rhizosphere of Gutierrezia sarothrae grown in elevated atmospheric carbon dioxide

Differences in rhizosphere microbial community function in response to Gutierrezia sarothrae plants grown in elevated CO2 (750 mu l l(-1)) and fertilized with nitrogen were studied using the Biolog microplate analysis of sole C substrate utilization. Compared to ambient CO2 under elevated CO2, polymers were more slowly oxidized by the microbial community, amides showed no change in usage, and all other substrate groups were more rapidly utilized, although there was no significant change in the number of viable bacteria. No microbial community responses to N fertilization were detected. The results indicate that potential functional changes in the soil microbial community in response to elevated CO2 have to be taken into account in future experiments. Differential use of rhizo-deposits in elevated CO2 may have important consequences for biogeochemistry and plant growth. (C) 1997 Elsevier Science Ltd.