HR: 1330h
AN: B22A-0795    [PDF]
TI: Short-term Fate of Carbon in two Woody Species Under Contrasting Resources Availability: Insights From a $^{13}$CO$_{2}$ Pulse Labeling Approach
AU: * Mambelli, S
EM: mambelli@socrates.berkeley.edu
AF: Department of Integrative Biology, 3060 Valley Life Sciences Bldg. University of California, Berkeley, CA 94720
AU: Dawson, T E
EM: tdawson@socrates.berkeley.edu
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road MS 90-1116, Berkeley, CA 94720
AU: Bird, J A
EM: jabird@socrates.berkeley.edu
AF: Department of Integrative Biology, 3060 Valley Life Sciences Bldg. University of California, Berkeley, CA 94720
AU: Bird, J A
EM: jabird@socrates.berkeley.edu
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road MS 90-1116, Berkeley, CA 94720
AU: Torn, M S
EM: mstorn@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road MS 90-1116, Berkeley, CA 94720
AU: Gaudinski, J B
EM: Gaudinsk@ucsc.edu
AF: Department of Environmental Studies, 473 Integrated Sciences Building University of California, Santa Cruz, CA 95064
AB: In response to the environment, plants adjust allocation patterns to maintain a functional balance between the activities of roots and shoots such that belowground resources are acquired in approximate balance with aboveground resources. Changes in allocation driven by changes in environmental conditions may affect the amount of carbon stored in plant tissues, released by the root system, and ultimately sequestered into the soil. The aim of this study was to quantify the allocation belowground of recently fixed carbon in contrasting species and resources availability. We tested the hypothesis that carbon limitation and high nitrogen supply both negatively affect carbon transport to roots, causing a reduction of the carbon flow into the soil rhizosphere. Two woody species, a conifer ({\it Pinus Ponderosa}) and a deciduous tree ({\it Acer Rubrum}) were grown in a greenhouse under a factorial of light and nitrogen regimes (full light/shade and limited/excess nitrogen). At the stage of full leaf expansion plants were pulse-labeled by addition of $^{13}$CO$_{2}$ and harvested after 0, 7 and 30 days. During the experiment the treatments affected the pattern of plant biomass allocation. Shade negatively influenced belowground growth and Maple showed a more conservative response than Pine. High supply of nitrogen also reduced allocation to roots but only when plants were grown under light. Preliminary results show that the initial amount of recently fixed carbon into the rhizosphere was in general higher under Pine. However, after 7 and 30 days, the new soil carbon pool increased only in the rhizosphere of carbon limited Pine seedlings. These findings suggest that belowground respiration was negatively affected or, alternatively, that the exudates released were less easily decomposable
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting