HR: 1340h
AN: H13C-0441    [Abstracts]
TI: Spatially Explicit Observations to Elucidate Simple Scalars of Forest Canopy Transpiration Across Environmental Gradients
AU: * Loranty, M M
EM: mloranty@buffalo.edu
AF: Department of Geography, State University of New York at Buffalo, 105 Wilkeson Quadrangle, Buffalo, NY 14261 United States
AU: Ewers, B E
EM: beewers@uwyo.edu
AF: Department of Botany, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Mackay, D S
EM: dsmackay@buffalo.edu
AF: Department of Geography, State University of New York at Buffalo, 105 Wilkeson Quadrangle, Buffalo, NY 14261 United States
AU: Adelman, J D
EM: jadelman@uwyo
AF: Department of Botany, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Kruger, E L
EM: kruger@calshp.cals.wisc.edu
AF: Department of Forest Ecology and Management, University of Wisconsin - Madison, 1630 Linden Drive, Madison, WI 53706 United States
AB: The ability to scale from point measurements to watersheds has been a key goal of hydrology. Assumptions are often made that averaging point measurements and scaling them up using a cookie-cutter or paint-by-numbers approach will capture relevant spatial gradients. To test this, we chose a site in the Chequamegon National Forest near Park Falls, WI because of its proximity to the WLEF Ameriflux tower providing kilometer scale estimates of water fluxes from a heterogeneous forest. We used a cyclic sampling design for all 144 plots of spatial measurements within a 1.5 ha area, in order to efficiently quantify spatial trends using geostatistics. Spatial data was collected for sap flux using Granier type sensors daily for ten days in 170 trees representing 7 species, including aspen, alder, and white cedar. Aspen is a dominant species in the managed forests around the WLEF tower and we have previously shown it to have the highest transpiration rates per unit leaf area of all dominant species in the area. Consequently, for this study we focused on aspen. Spatial soil moisture, vapor pressure deficit, and leaf area index were also measured periodically at the same 144 plots. We found that the semivariagram of soil moisture showed a range of 110 meters on a low soil moisture day and 80 meters on a high soil moisture day. When we quantified sap flux per unit xylem area across a 105-meter long gradient from a wetland to an upland we found no differences. However, once we scaled the sap flux measurements to the whole tree using basal area, there was more than a 100 percent increase in whole tree water use in the upland area in comparison to the wetland area. Thus, we will test the hypothesis that in the absence of moisture stress, canopy transpiration in aspen varies spatially with allometrically scaled sapwood area and leaf area and not as a function of sap flux per unit sapwood area.
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting