PARENT SESSION
Oral Session # 12: Biogeochemistry I: Carbon Dioxide Cycling.
Presiding: D Markewitz
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 204.
Responses of roots of two deciduous tree species, Acer rubrum (red maple) and A. saccharum (sugar maple), to elevated CO2 and temperature.
Wan, Shiqiang*,1, Pregitzer, Kurt2, O'Neill, Elizabeth1, Norby, Richard1, 1 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN2 School of Forestry and Wood Products, Michigan Technological University, Houghton, MI
ABSTRACT- As a central component of ecosystem carbon and nutrient cycling, root production and turnover may be substantially affected by global change and act as a key link between plant responses and long-term changes in soil organic matter and ecosystem carbon balance. A four-year temperature and CO2 interaction experiment was conducted in open-top chambers at the Oak Ridge National Environmental Research Park in Tennessee, USA. Both elevated CO2 and elevated temperature significantly enhanced total root production, root mortality, and net root production. At the end of the experiment, elevated CO2 also increased fine-root biomass. However, higher temperature reduced fine-root biomass for all size classes, which could be attributable to the warming-induced heat stress and reduction in aboveground growth in two hot summers. Specific root length significantly decreased with elevated CO2 and the interaction of temperature and CO2, but temperature alone did not affect it. Elevated temperature and the interaction of temperature and CO2 had significant positive effects on N concentration of roots smaller than 0.5 mm whereas elevated CO2 had a negative effect. Root C concentration increased with root size class, but root N concentration decreased. Both elevated CO2 and temperature reduced the ratio of root biomass to aboveground biomass, suggesting that there might be a relative decrease in belowground C allocation in these deciduous trees in a warmer, CO2 enriched world. The interactive effects of elevated temperature, CO2, and interannual variability of climate in regulating root production, turnover, and biomass may all be important in understanding forest C cycling.
Key words: elevated CO2, Acer rubrum, A. saccharum, root production & biomass, temperature