HR: 10:40h
AN: H52C-02    [Abstracts]
TI: Dioecy Impacts on Plant Water Fluxes in Riparian Ecosystems
AU: * Hultine, K R
EM: hultine@biology.utah.edu
AF: University of Utah, 257 S 1400 E, Salt Lake City, UT 84112-0840 United States
AU: Bush, S E
EM: sbush@biology.utah.edu
AF: University of Utah, 257 S 1400 E, Salt Lake City, UT 84112-0840 United States
AU: West, A G
EM: awest@biology.utah.edu
AF: University of Utah, 257 S 1400 E, Salt Lake City, UT 84112-0840 United States
AU: Ehleringer, J R
EM: ehleringer@biology.utah.edu
AF: University of Utah, 257 S 1400 E, Salt Lake City, UT 84112-0840 United States
AB: Dioecious plants are frequently associated with different spatial distributions of the two sexes across resource gradients. Segregation between sexes might be expected to occur if the cost of reproduction is greater in females than in males. If so, females would be under stronger selection to increase rates of resource uptake. Acer negundo is a dioecious riparian tree species that show spatial segregation among sexes: females are typically more common along streamside (high resource) environments than males. The spatial segregation of the sexes leads to the hypothesis that male and female individuals have varying influence on ecohydrological processes. To address this, we measured sap flux, water relations and hydraulic architecture of mature streamside (less than 1 m from stream channel) male and female Acer negundo trees occurring near Salt Lake City, Utah, USA during the 2004 growing season. Despite similar predawn and midday leaf water potentials, sap flux density ( J_s) was 40 percent higher in female trees than in male trees during the 2004 growing season (n = 42 days, F = 73.56, P < 0.0001). Both genders showed a similar relationship between conducting sapwood area to stem diameter ratio suggesting that differences in J_s scale to the whole tree level. Sap flux data from Acer negundo trees was compared to five other co-occurring riparian tree species. Female Acer negundo trees showed the highest J_s among all species while J_s in male Acer negundo trees was lower than all other species except one ( Acer grandidentatum). These data demonstrate that individual female Acer negundo trees have the capacity remove water at higher rates than males in high resource environments. The spatial segregation of the sexes along streamside environments may therefore have profound impacts on ecohydrological processes such as stream discharge, groundwater recharge, and nutrient cycling.
UR: http://ecophys.biology.utah/Labfolks/KHultine/page1.html
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1839 Hydrologic scaling
DE: 1851 Plant ecology (0476)
DE: 1852 Plant uptake
SC: Hydrology [H]
MN: Fall Meeting 2005