PARENT SESSION
Contributed Oral Session 32: Soil Nutrient Dynamics and Acid Deposition
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal

Microbial community function in elevated atmospheric CO₂ in Florida, USA scrub oak soil and leaf litter.

Pagel, Alisha^*,1, Garland, Jay², Day, Frank¹, Hungate, B⁴, Carney, K³, Drake, Bert³, ¹ Old Dominion University, Norfolk, Virginia, USA² Dynamac Corporation, Kennedy Space Center, Florida, USA⁴ Northern Arizona University, Flagstaff, AZ³ Smithsonian Environmental Research Center, Edgewater, Maryland, USA

ABSTRACT- Microbial response remains unclear as anthopogenically derived carbon dioxide is integrated into the global ecosystem. With the potential to increase carbon release from the soil or facilitate long-term carbon storage, it is important to investigate microbial response under elevated atmospheric CO₂ conditions. Soil and leaf litter microbial communities can potentially be affected through elevated CO₂ derived changes in nutrient availability or C cycling in the ecosystem. Soils and leaf litter were taken from a Florida scrub oak ecosystem that has been under elevated CO₂ treatment since 1996. When exposed to several nutrient treatments and carbon energy sources, microbial community responses were observed using an oxygen biosensor system (OBS) based on microtiter plates containing an oxygen sensitive flourophore. Using this technique, it is possible to assay microbial oxygen consumption and use of carbon substrates, rapidly profiling the community. The nutrient treatments were: -N-P (mineral salt media without N and P), +N (mineral salt media with N without P), +P (mineral salt media with P without N), +N+P (mineral salt media with N and P). The substrates for energy use were made from litter and root material taken from CO₂ treated open topped chambers, and from glucose. There was no acclimation of microbial communities to litter or root material taken from their respective CO₂ treatments, and overall microbial community function as assessed by OBS remained unchanged by elevated CO₂. There were no elevated CO₂ treatment effects on soil dissolved organic carbon, soil pH or soil and leaf litter microbial response under any nutrient treatment. Soil and litter microbial communities were released from limitation when exposed to both N and P. The primary nutrient limitation of N and secondary limitation of P suggests that soil microbial communities will be not able to utilize additional carbohydrates released into the soil and litter due to elevated atmospheric CO₂, leading to leaching of additional carbon into the groundwater.

Key words: elevated CO2, microbial community function, nutrient limitation