HR: 1340h
AN: H53E-0521    [Abstracts]
TI: Quantifying the hydrological significance of tree hydraulic redistribution in a savanna ecosystem.
AU: * Cable, W L
EM: wcable@tucson.ars.ag.gov
AF: USDA-ARS, 2000 E. Allen Rd., Tucson, AZ 85719 United States
AU: Scott, R L
EM: rscott@tucson.ars.ag.gov
AF: USDA-ARS, 2000 E. Allen Rd., Tucson, AZ 85719 United States
AB: A number of recent studies have illuminated that plant root systems in dryland ecosystems often facilitate soil moisture redistribution, but the hydrologic significance of this process is poorly understood. In dryland ecosystems this may be an important interaction as water is often the limiting factor in biomass accumulation. We are studying the way in which the tree, Prosopis velutina, influences the hydrologic cycle though hydraulic redistribution in an upland savanna ecosystem. Using the heat ratio method we are measuring bi-directional sap flow in both lateral and tap roots. Additionally, we are monitoring soil water content and whole ecosystem carbon and water exchange adjacent to the trees being studied. We have found that the tree root systems transport water even when the trees are dormant. Thus, wintertime precipitation tends to be taken up by shallow lateral roots and translocated to deeper lateral and tap roots. This trend also occurs when trees are active and when excess moisture from summer monsoons is available in the upper soil layers. As the upper soil layers dry out water use from deeper soil layers is increased. We believe that this deeper "stored" water is what allows the trees to become active in the spring even when surface soils are extremely dry and helps carry them through periods of drought. These findings help shed some light on how a woody plant can thrive in an ecosystem where precipitation is sporadically distributed in space and time.
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology (0476)
DE: 1854 Precipitation (3354)
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: Fall Meeting 2005