HR: 14:25h
AN: B13B-04    [Abstracts]
TI: The Respiration-to-Photosynthesis Ratio of Intact Forests Exposed to Elevated CO2 concentration
AU: * Trueman, R J
EM: rtruem1@uic.edu
AF: University of Illinois at Chicago, Biological Sciences 3342 SES 845 W. Taylor St. m/c 066, chicago, il 60607 United States
AU: Gunderson, C
EM: gundersonca@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences Division One Bethel Valley Road, Bldg. 1062, Oak Ridge, TN 37831-6422 United States
AU: Norby, R J
EM: norbyrj@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences Division One Bethel Valley Road, Bldg. 1062, Oak Ridge, TN 37831-6422 United States
AU: Oleynik, S A
EM: oleynik@uic.edu
AF: University of Illinois at Chicago, Biological Sciences 3342 SES 845 W. Taylor St. m/c 066, chicago, il 60607 United States
AU: Wullschleger, S D
EM: wullschlegsd@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences Division One Bethel Valley Road, Bldg. 1062, Oak Ridge, TN 37831-6422 United States
AU: Yakir, D
EM: dan.yakir@weizmann.ac.il
AF: Weizmann Institute of Science, Department of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AU: Gonzalez-Meler, M A
EM: mmeler@uic.edu
AF: University of Illinois at Chicago, Biological Sciences 3342 SES 845 W. Taylor St. m/c 066, chicago, il 60607 United States
AB: Forests represent the largest biomass C pool on earth and a major pathway of entry for atmospheric C into recalcitrant soil pools. Photosynthesis and ecosystem respiration determine the net balance between the direction and magnitude of the terrestrial carbon sink. Increasing atmospheric CO₂ concentration from the combustion of fossil fuels has the potential to alter biospheric C fluxes and the pool size of biospheric C. In order to resolve linkages between plants, soil and the atmosphere the biotic and abiotic controls on ecosystem C fluxes need to be understood. A complication in gaining mechanistic information on ecosystem respiration is that in terrestrial ecosystems a variety of substrates are oxidized by multiple biochemical pathways pertaining to organisms of all kingdoms. In this study we used isotope tracers to separate stand level plant respiration from ecosystem respiration in intact forests exposed to elevated [CO₂]. A one-day ¹³C label (C*) was applied to two forested ecosystems; a Populus deltoides plantation and a Liquidambar styraciflua dominated forest under ambient and elevated CO₂ concentrations. The amount of C* that was assimilated by these ecosystems was determined by both net ecosystem exchange (NEE) and leaf-level photosynthesis measurements. We then tracked the C* lost to respiration from the leaves, stems, roots and soil, and determined the mean residence time (MRT) of C*. This method allowed us to assess the instantaneous C use efficiency (iCUE) by determining the respiration:photosynthesis ratio of C* that can be used to provide useful data to C models. In addition, the P. deltoides and L. styraciflua forested ecosystems had received a constant fumigation ¹³C signature for 3 and 8 years, respectively. Using this constant ¹³C label along with the one-day tracer study we were able to separate soil respiration into at least three age classes.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
SC: Biogeosciences [B]
MN: Fall Meeting 2005