HR: 17:45h
AN: B42D-07    [PDF]
TI: A Challenge to the Flux-Tower Upscaling Hypothesis? A Multi-Tower Comparison From the Chequamegon Ecosystem-Atmosphere Study
AU: * Davis, K J
EM: kjd10@psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Ricciuto, D R
EM: ricciuto@essc.psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Butler, M P
EM: mpbutler@essc.psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Desai, A R
EM: adesai@essc.psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Wang, W
EM: wang@essc.psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Yi, C
EM: cxyi@essc.psu.edu
AF: The Pennsylvania State University, Department of Meteorology, University Park, PA 16877 United States
AU: Bakwin, P S
EM: pbakwin@cmdl.noaa.gov
AF: National Oceanographic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, CO 80307 United States
AU: Cook, B D
EM: bcook@essc.psu.edu
AF: University of Minnesota, Department of Forest Resources, St. Paul, MN 55108 United States
AU: Bolstad, P V
EM: pbolstad@umn.edu
AF: University of Minnesota, Department of Forest Resources, St. Paul, MN 55108 United States
AU: Carey, E
EM: ecarey@umn.edu
AF: University of Minnesota, Department of Forest Resources, St. Paul, MN 55108 United States
AU: Martin, J
EM: mart0166@umn.edu
AF: University of Minnesota, Department of Forest Resources, St. Paul, MN 55108 United States
AU: Teclaw, R
EM: rteclaw@fs.fed.us
AF: USDA Forest Service, Forest Sciences Laboratory, Rhinelander, WI 11111 United States
AU: Mackay, D S
EM: dsmackay@buffalo.edu
AF: State University of New York at Buffalo, Department of Geography, Buffalo, NY 11111 United States
AU: Ewers, B E
EM: beewers@uwyo.edu
AF: University of Wyoming, Department of Botany, Laramie, WY 11111 United States
AU: Chen, J
EM: jiquan.chen@utoledo.edu
AF: University of Toledo, Department of Ecology, Toledo, OH 11111 United States
AU: Noormets, A
EM: asko.noormets@utoledo.edu
AF: University of Toledo, Department of Ecology, Toledo, OH 11111 United States
AU: Heinsch, F A
EM: faithann@ntsg.umt.edu
AF: University of Montana, Department of Forestry, Missoula, MT 59812 United States
AU: Denning, A S
EM: denning@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Sciences, Fort Collins, CO 11111 United States
AB: The "flux-tower upscaling hypothesis" asserts that flux tower measurements of representative ecosystems can be upscaled to regional fluxes via ecosystems mapping and process models. Collecting an integrated set of measurements to attempt upscaling is challenging. The required sampling density is also uncertain, and at minimum depends on local soil and vegetation cover, land use patterns, and climate gradients. Measurements that can be used to evaluate upscaling efforts are similarly difficult to obtain. Thus the basic hypothesis behind the flux tower approach of studying regional and global carbon (and hydrologic) cycles remains difficult to implement and test. The Chequamegon Ecosystem-Atmosphere Study (ChEAS) has endeavored to create a distributed set of stand-level flux tower and supporting measurements that can be used to upscale carbon and water flux measurements to the regional scale. The flux measurements collected at the 447m WLEF TV tower are proposed as a regional integral that can be used to evaluate the stand-level upscaling. Though more exhaustive analyses are warranted, the results to date bear a mixed message for tower-based upscaling. The absolute magnitude of the fluxes from two stand-level towers cannot be simply aggregated to explain the observations from the WLEF tower. Decomposition implies that while photosynthesis may upscale, respiration does not. Potential explanations will be discussed, including comparisons to chamber respiration data, wetland water table, and flux measurements across young, mature and old-growth stands. The data from WLEF show a regional source of carbon to the atmosphere, counter to most temperate forest data and counter to the stand-level towers in the region. Upscaling interannual variability, however, appears to be a more tractable problem. Though the temporal extent of the multiple flux tower system is limited, a tent caterpillar outbreak in 2001 provides an example of a strong, coherent perturbation to the regional ecosystem that is captured by the available sampling. Stand-level measurements upscale reasonably well to explain the changes in regional fluxes measured at WLEF. Climatic variability from more recent data will also be presented, in addition to recommendations for future upscaling efforts.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
DE: 1694 Instruments and techniques
DE: 4805 Biogeochemical cycles (1615)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting