HR: 16:36h
AN: B14A-03 INVITED     [Abstracts]
TI: Ecosystem Water Use Varies With Disturbance And Stand Age
AU: * Chen, J
EM: jiquan.chen@utoledo.edu
AF: University of Toledo, Dept. of EEES, Toledo, OH 43606 United States
AU: Noormets, A
EM: asko.noormets@utoledo.edu
AF: University of Toledo, Dept. of EEES, Toledo, OH 43606 United States
AU: Paw U, K
EM: ktpawu@ucdavis.edu
AF: University of California, of Land, Air, and Water Resources, Davis, CA 95616 United States
AU: Ustin, S
EM: susan@cstars.ucdavis.edu
AF: University of California, of Land, Air, and Water Resources, Davis, CA 95616 United States
AU: Suchanek, T
EM: Tom_Suchanek@fws.gov
AF: U.S. Fish & Wildlife Service, 2800 Cottage Way, Sacramento, CA 95825 United States
AU: Sun, G
EM: ge_sun@ncsu.edu
AF: USDA Forest Service, Southern Global Change Program 920 Main Campus Dr., Raleigh, NC 27606 United States
AU: McNulty, S
EM: steve_mcnulty@ncsu.edu
AF: USDA Forest Service, Southern Global Change Program 920 Main Campus Dr., Raleigh, NC 27606 United States
AU: Euskirchen, E
EM: ffese@uaf.edu
AF: University of Alaska, Institute of Arctic Biology, Fairbanks, AK 99775 United States
AU: DeForest, J
EM: jdefore@UTNet.UToledo.Edu
AF: University of Toledo, Dept. of EEES, Toledo, OH 43606 United States
AU: Brosofske, K
EM: kdbrosof@hotmail.com
AF: University of Toledo, Dept. of EEES, Toledo, OH 43606 United States
AB: Many functions of an ecosystem are strongly controlled by water. Compared to ecosystem carbon exchange, the dynamics and controls of ecosystem water balance have received relatively less attention. Yet, these two fluxes are tightly interdependent, with water availability having a direct effect on the carbon budget. Using direct measurements (eddy flux towers) of net ecosystem exchange (NEE) of water and carbon from over 12 different ecosystem types in the Pacific Northwest and the Upper Great Lakes Region, we examined the magnitude and rate of change in ecosystem water use (WUe, defined as the mass ratio of NEE of carbon to NEE of water). We constructed empirical relationships for estimating WUe that incorporate disturbance and stand age, as well as the biophysical regulations such as vapor pressure deficit (VPD), solar radiation, and soil moisture conditions. WUe varied little throughout the growing season (June through September) in both regions, but there were notable differences in WUe with stand age. In northern Wisconsin, WUe was higher in mature stands (4.5 $\mu$g C.g$^-1$ H$_{2}$O) than in the younger, recently disturbed stands (2.1 $\mu$g C.g$^-1$ H$_{2}$O); yet WUe was much higher in 20 and 40 year-old stands (0.34-5.57) than in a 450-year-old stand (0.38-1.59) in the Pacific Northwest. The lowest WUe was found in a recent clearcut, where leaf area index was also the lowest. VPD is found to be a significant predictor of WUe in many ecosystems. Given the broad network of eddy flux towers currently collecting NEE data across the United States (e.g., Fluxnet), we expect that in the future we will be able to make further generalizations about WUe in ecosystems of different ages and under various disturbance regimes.
DE: 9350 North America
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting