HR: 11:30h
AN: H52C-05    [Abstracts]
TI: Use of Geostatistics and Plant Hydraulics to Explain Spatial Patterns of Transpiration Across Environmental Gradients
AU: * Ewers, B E
EM: beewers@uwyo.edu
AF: University of Wyoming, Department of Botany, 1000 E. University Ave., Laramie, WY 82071 United States
AU: Adelman, J D
EM: jadelman@uwyo.edu
AF: University of Wyoming, Department of Botany, 1000 E. University Ave., Laramie, WY 82071 United States
AU: Mackay, D S
EM: dsmackay@buffalo.edu
AF: State University of New York at Buffalo, Department of Geography, 105 Wilkeson Quad., Buffalo, NY 14261 United States
AU: Loranty, M
EM: mloranty@buffalo.edu
AF: State University of New York at Buffalo, Department of Geography, 105 Wilkeson Quad., Buffalo, NY 14261 United States
AU: Traver, E
EM: traver@uwyo.edu
AF: University of Wyoming, Department of Botany, 1000 E. University Ave., Laramie, WY 82071 United States
AU: Kruger, E L
EM: elkruger@wisc.edu
AF: University of Wisconsin, Department of Forest Ecology, 1630 Linden Dr., Madison, WI 53706 United States
AB: As direct measurements of tree transpiration via sap flux have become routine, the sample size of sap flux studies has dramatically increased. These large sample sizes now provide sufficient data for geostatistical analyses when measurement points are spatially explicit. In this study we tested whether 1) center-of-stand approaches to sap flux measurements and scaling are sufficient for characterizing stand level transpiration and 2) geostatistical techniques provide the information necessary for quantifying important stand and landscape level gradients. To maximize the inferences from our tests, we compared two contrasting forests: one dominated by lodgepole pine (Pinus contorta) in Wyoming and another dominated by trembling aspen (Populus tremuloides) in Wisconsin. The forest in Wyoming is characterized by low precipitation regimes dominated by snowfall while the forest in Wisconsin is characterized by moderate precipitation throughout the growing season. Analyses of the relationship between sample size and variance indicated an inflection point of 30 point pairs but the variance continued a shallow decline even at 100 point pairs. There was also evidence of species impacts on variance of transpiration that changed with environmental conditions. We used variogram analyses to quantify the spatial range of transpiration and found a variable spatial range across days with mean of approximately 30 m. The variability in spatial range could be partially explained by tree species' responses to soil moisture, vapor pressure deficit, and light based on current plant hydraulic knowledge. Our results confirm the utility of geostatistical techniques for quantifying and explaining transpiration in time and space.
DE: 0476 Plant ecology (1851)
DE: 1813 Eco-hydrology
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: Fall Meeting 2005