HR: 1340h
AN: H33C-1456    [Abstracts]
TI: Reference Canopy Stomatal Conductance Explains Spatiotemporal Patterns of Tree Transpiration
AU: * Loranty, M M
EM: mloranty@buffalo.edu
AF: SUNY Buffalo Department of Geography, 105 Wilkeson Quad, Buffalo, NY 14261, United States
AU: Mackay, D S
EM: dsmackay@buffalo.edu
AF: SUNY Buffalo Department of Geography, 105 Wilkeson Quad, Buffalo, NY 14261, United States
AU: Ewers, B E
EM: beewers@uwyo.edu
AF: University of Wyoming Department of Botany, 1000 East University Ave, Laramie, WY 82071, United States
AU: Kruger, E L
EM: elkruger@facstaff.wisc.edu
AF: University of Wisconsin - Madison Department of Forest Ecology and Management, Russell Labs 1630 Linden Dr, Madison, WI 53706, United States
AU: Traver, E
EM: etraver@uwyo.edu
AF: University of Wyoming Department of Botany, 1000 East University Ave, Laramie, WY 82071, United States
AB: Increased heterogeneity in patterns of whole tree transpiration (E_C) with increasing atmospheric vapor pressure deficit (D) suggests a dynamic response of sap flow velocity (J_S) to environmental drivers. We hypothesized that differences in reference stomatal conductance (G_Sref), stomatal conductance at D = 1kPa, would explain the spatiotemporal dynamics of J_S. Using a coupled model of plant hydraulic and biochemical processes we tested this hypothesis with sap flux data for 106 aspen ( Populus tremuloides) and 108 sugar maple ( Acer saccharum) trees collected from plots using in 2-D cyclic sampling scheme during the summer of 2005 in northern Wisconsin. Inverse modeling is used to estimate G_Sref for each tree. For each species, trees from across the ranges of J_S and diameter distributions are compared. G_Sref explained temporal variability in spatial patterns of E_C We explore several possible mechanistic explanations for differences in G_Sref among trees. Topoedaphic factors are considered to determine if location within a stand has an effect. We also consider competition with neighboring individuals as a possible explanation. Variations in G_Sref in aspen were explained in part by competition for light between neighboring individuals, while competition for light was not a significant factor for sugar maple. Based on simulation analysis we identify possible biochemical feedbacks as drivers of the variability in plant hydraulics. Other factors examined included micro-topography within both sites.
DE: 1813 Eco-hydrology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1851 Plant ecology (0476)
DE: 1878 Water/energy interactions (0495)
SC: Hydrology [H]
MN: 2007 Fall Meeting