HR: 0800h
AN: B51C-0970    [Abstracts]
TI: Rainfall regulates the impact of elevated atmospheric CO2 on carbon balance in Chesapeake Bay wetland and Florida Scrub Oak.
AU: * Drake, B G
EM: drakeb@si.edu
AF: Smithsonian Environmnetal Research Center, PO Box 28, Edgewater, MD 21037
AU: Rasse, D
EM: drasse@grignon.inra.fr
AF: Smithsonian Environmnetal Research Center, PO Box 28, Edgewater, MD 21037
AB: Elevated atmospheric CO2 (Ca) is expected to stimulate ecosystem carbon assimilation and reduce stomatal conductance and transpiration in native ecosystems but the interaction between these effects and water and nutrient supply is highly uncertain. We report results of measurements of Net Ecosystem CO2 Exchange (NEE) from an 18 year study of the effects of elevated Ca on a Chesapeake Bay Maryland wetland and a seven year study in a scrub oak ecosystem Cape Canaveral, Florida exposed to ambient or elevated (normal ambient plus 350 ppm) Ca in open top chambers which were also used to measure NEE. Although acclimation of photosynthesis was commonly observed, elevated Ca often caused a stimulation of photosynthesis of 35-100 percent. Elevated Ca stimulated NEE was the same or greater than NEE in sites at normal ambient Ca but inter-annual variation in the effect was large. Stimulation of NEE by elevated Ca was linearly correlated with rainfall. These results suggest that the inter-annual variation in the effects of elevated Ca on ecosystem carbon balance were due to the availability of water and not to other factors such as nitrogen supply.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting