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)) a nd fertilized with nitrogen were studied using the Biolog microplate a nalysis of sole C substrate utilization. Compared to ambient CO2 under elevated CO2, polymers were more slowly oxidized by the microbial com munity, amides showed no change in usage, and all other substrate grou ps were more rapidly utilized, although there was no significant chang e in the number of viable bacteria. No microbial community responses t o N fertilization were detected. The results indicate that potential f unctional changes in the soil microbial community in response to eleva ted CO2 have to be taken into account in future experiments. Different ial use of rhizo-deposits in elevated CO2 may have important consequen ces for biogeochemistry and plant growth. (C) 1997 Elsevier Science Lt d.