PARENT SESSION
Oral Session #42: Decomposition.
Presiding: K. Gross
Tuesday, August 6. 1:00 PM to 4:45 PM. Apache Meeting Room, TCC.

Soil microbial responses at three contrasting CO₂ enrichment sites.

SINSABAUGH, ROBERT^*,1, ZAK, DON², LARSEN, JENNIFER², OSGOOD, MARCY², ¹ University of Toledo, Toledo, OH² University of Michigan, Ann Arbor, MI

ABSTRACT- The physiological responses of plants to atmospheric CO₂ enrichment affect soil microbial activity through changes in the quantity and quality of litter and root carbon inputs. These microbial responses may feed back on plant growth by influencing nutrient availabilities. We have been following microbial activity at three contrasting Free Air Carbon Enrichment (FACE) sites: a loblolly pine system in the Duke Forest, NC; a sweet gum system at Oak Ridge National Lab (ORNL), TN; and aspen, birch and maple systems at Rhinelander, WI. At the Duke site, root and litter inputs have differentially affected extracellular enzyme activities (EEA), shifting patterns of decomposition through time. At Rhinelander, initial soil microbial responses resemble those at Duke: more cellulolytic and N&P acquistion activity and higher substrate utilization. At ORNL, no soil EEA and substrate utilization responses have been detected, despite NPP enhancements comparable to those at the other sites. The results indicate that enhanced litter and root inputs may affect microbial activity differently and that soil properties have the potential to mitigate the effects of plant physiological response.

KEY WORDS: microbial activity, CO2 response, decomposition