HR: 0800h
AN: B41D-0231    [Abstracts]
TI: Soil and Canopy Control Over Ecosystem Carbon and Water Fluxes in a Desert Grassland: Patterns From a Rainfall Manipulation Experiment.
AU: * Huxman, T E
EM: huxman@email.arizona.edu
AF: University of Arizona, Ecology and Evolutionary Biology, Tucson, AZ 85721-0088 United States
AU: Williams, D
B41D-0231 AF: University of Wyoming, Department of Botany, Laramie, WY 82050
AU: Scott, R
B41D-0231 AF: USDA-ARS, Southwest Watershed Research Center, Tucson, AZ 85716
AU: Cable, J
B41D-0231 AF: University of Arizona, Ecology and Evolutionary Biology, Tucson, AZ 85721-0088 United States
AU: Potts, D
B41D-0231 AF: University of Arizona, Ecology and Evolutionary Biology, Tucson, AZ 85721-0088 United States
AU: Pavao-Zuckerman, M
B41D-0231 AF: University of Arizona, Ecology and Evolutionary Biology, Tucson, AZ 85721-0088 United States
AU: Ignace, D
B41D-0231 AF: University of Arizona, Ecology and Evolutionary Biology, Tucson, AZ 85721-0088 United States
AB: While plant canopies are important controllers over water and carbon fluxes between the biosphere and atmosphere, in water limited ecosystems soils have important direct and indirect effects on ecosystem fluxes. Using whole-ecosystem assessments of water and carbon exchanges in large plots exposed to different precipitation regimes, we have attempted to understand how individual rainfall events and characteristics of precipitation in time influence exchange processes. Since precipitation is an important trigger for biological and physical processes that result in exchange, how soils translate rainfall into biologically available water affects microbially-mediated carbon cycling and potential plant activity. Additionally, the expanse of bare-ground area and microclimate characteristics can influence the relative importance of transpiration versus evaporation following rainfall events. Because physical processes, such as gas displacement by infiltrating water, occur quicker than photosynthetic upregulation by plants, semi-arid and arid ecosystems are often immediate sources of carbon to the atmosphere following rainfall events and only become sinks should water persist in the rooting zone for sufficient time to allow for plant activity. In general, characteristics of rainfall, such as frequency and magnitude influence ecosystem processes primarily by controlling the duration of process rather than the maximum rate of activity. Understanding such controllers is important to mechanistically modeling biosphere / atmosphere exchange in water limited ecosystems.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: Fall Meeting 2005