PARENT SESSION
Organized Oral Session 36: Role of microbial communities in mediating biogeochemical response to disturbance
Organizer(s): EAH Smithwick and MG Turner
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 511 B, Level 5, Palais des congrès de Montréal
Global disturbance affecting the micro-scale: Microbial communities and carbon cycling at the JRGCE.
Mentzer, Jessica*,1, Balser, Teri1, 1 Department of Soil Science, Madison, WI, USA
ABSTRACT- An understanding of the potential effects of global change on atmospheric chemistry and climate is especially important in grassland ecosystems. Because of their central role in soil carbon storage and nutrient cycling, grassland soil microbial communities are an essential link between ecosystem function, plants, and soil. In this study, we used analysis of membrane lipids to track seasonal carbon flow and characterize a California grassland microbial community undergoing long-term multiple global change treatments. The Jasper Ridge Global Change Experiment (JRGCE, Stanford, California) began in November 1998 to test the effects of four global change factors (elevated carbon dioxide, nitrogen deposition, elevated temperature and elevated precipitation) on grassland functioning in a full factorial experiment with eight replicates of each treatment. Samples were taken in May 2001, November 2001, January 2002, March 2002, and April 2002 from the JRGCE. Initial results from 2001 and 2002 indicate that elevated precipitation resulted in lower abundance of all bacterial indicators and higher relative abundance of the protozoal indicator. Elevated nitrogen deposition appears to decrease the relative abundance of mycorrhizal fungi while increasing the relative abundance of saprotrophic fungi. Stable isotope carbon ratios indicate that mycorrhizal and saprotrophic fungal indicators have a signature close to the ′new′ (more labile) carbon while Gram-positive microbial indicators have a carbon isotope ratio closer to that of the ′old′ recalcitrant organic carbon pool. It appears that elevated nitrogen and elevated precipitation have the greatest effect on microbial community composition and that global change factors may have different effects seasonally.
Key words: stable isotope ecology, microbial ecology, global change, lipid analysis