PARENT SESSION
Contributed Oral Session 110: Biogeochemistry: Nitrogen Dynamics
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 513 C, Level 5, Palais des congrès de Montréal

No responses of belowground C and N pools and dynamics to elevated [CO₂], rising temperature and changing soil moisture in old-field grassland.

Wan, Shiqiang^{1, 2}, Norby, Richard², Weltzin, Jake ³, Allen, Philp³, ¹ Institute of Botany, the Chinese Academy of Sciences, Beijing, China² Environmental Sciences Divsion, Oak Ridge National Laboratory, Oak Ridge, TN, USA³ Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA

ABSTRACT- This study was conducted to investigate the effects of atmospheric [CO₂], air temperature, and soil moisture on belowground pools and dynamics of C and N in a constructed old-field plant community in east Tennessee. Twelve plots (4 m in diameter) constructed in July 2002 were exposed to combinations of ambient and elevated (+ 300 ppm) [CO₂], ambient and elevated (+ 3^oC) temperature, and two levels of soil moisture (relatively wet and dry) beginning in June 2003. Root biomass, soil N availability, gross N mineralization, and microbial biomass C and N were measured in 2003 and 2004 using root in-growth cores, resin capsules, 15N dilution, and chloroform fumigation methods, respectively. None of the measured variables showed any responses to [CO₂], temperature, or soil moisture. The lack of response in belowground pools of C and N in the first 2 years of the experiment might have been because the plant community was relatively young, or because of changes in species composition. Long-term observations are needed to detect the potential influences of multiple driving factors on pools and dynamics of soil C and N.

Key words: Carbon, Nitrogen, old field, global change