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Applied and Environmental Microbiology, December 2005, p. 8573-8580, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8573-8580.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Effects of Elevated Atmospheric CO2 on Soil Microbial Biomass, Activity, and Diversity in a Chaparral Ecosystem

David A. Lipson,* Richard F. Wilson, and Walter C. Oechel

Department of Biology, San Diego State University, San Diego, California 92182-4614

Received 28 May 2005/ Accepted 13 September 2005

This study reports the effects of long-term elevated atmospheric CO2 on root production and microbial activity, biomass, and diversity in a chaparral ecosystem in southern California. The free air CO2 enrichment (FACE) ring was located in a stand dominated by the woody shrub Adenostoma fasciculatum. Between 1995 and 2003, the FACE ring maintained an average daytime atmospheric CO2 concentration of 550 ppm. During the last two years of operation, observations were made on soil cores collected from the FACE ring and adjacent areas of chaparral with ambient CO2 levels. Root biomass roughly doubled in the FACE plot. Microbial biomass and activity were related to soil organic matter (OM) content, and so analysis of covariance was used to detect CO2 effects while controlling for variation across the landscape. Extracellular enzymatic activity (cellulase and amylase) and microbial biomass C (chloroform fumigation-extraction) increased more rapidly with OM in the FACE plot than in controls, but glucose substrate-induced respiration (SIR) rates did not. The metabolic quotient (field respiration over potential respiration) was significantly higher in FACE samples, possibly indicating that microbial respiration was less C limited under high CO2. The treatments also differed in the ratio of SIR to microbial biomass C, indicating a metabolic difference between the microbial communities. Bacterial diversity, described by 16S rRNA clone libraries, was unaffected by the CO2 treatment, but fungal biomass was stimulated. Furthermore, fungal biomass was correlated with cellulase and amylase activities, indicating that fungi were responsible for the stimulation of enzymatic activity in the FACE treatment.

* Corresponding author. Mailing address: Department of Biology, San Diego State University, San Diego, CA 92182-4614. Phone: (619) 594-4460. Fax: (619) 594-5676. E-mail: dlipson{at}sciences.sdsu.edu.

Applied and Environmental Microbiology, December 2005, p. 8573-8580, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8573-8580.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Carney, K. M., Hungate, B. A., Drake, B. G., Megonigal, J. P. (2007). Altered soil microbial community at elevated CO2 leads to loss of soil carbon. Proc. Natl. Acad. Sci. USA 104: 4990-4995 [Abstract] [Full Text]  


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