HR: 11:45h
AN: NB52E-06    [Abstracts]
TI: Integrating Vegetation, Soil and Topography to Assess the Impact of Lateral Flow on Plant Solute Uptake
AU: * Rebel, K T
EM: karin.rebel@ce.gatech.edu
AF: Georgia Institute of Technology, 790 Atlantic Dr., Atlanta, GA 30332-0355 United States
AU: Riha, S J
EM: sjr4@cornell.edu
AF: Cornell University, 1110 Bradfield Hall, Ithaca, NY 14853 United States
AU: Stedinger, J R
EM: jrs5@cornell.edu
AF: Cornell University, 213 Hollister Hall, Ithaca, NY 14853 United States
AB: Simulation of solute uptake by vegetation in complex terrain typically fails to account for subsurface lateral movement of solutes. This study uses a spatially explicit plant-soil-water simulation model to investigate whether subsurface lateral flow at the sand-clay interface impacts tritium uptake by mixed forest vegetation. Ten hectares of a mixed pine - laurel oak forest on Coastal Plain soils periodically received irrigation with tritium-enriched water (activity ranged from 5,000 to 20,000 pCi/ml) over a three year time period. To simulate water and tritium fluxes we developed a spatially explicit water balance model. Tritium was completely mixed daily with water in each soil layer. Vertical flow of water was simulated using a capacitance model with lateral flow dependent on head development and the local slope of the impeding clay layer. The model was evaluated by comparing biweekly measurements of tritium activity (measured to 3 meter depth) and soil water content (measured to 2 meter depth) in 18 measurement clusters distributed over the catchment. We evaluated the importance of including subsurface flow in model simulations. Lateral flow was locally important (mean distance tritium traveled laterally was 1.35 m). However, after three years of simulation, the maximum predicted lateral movement of tritium did not exceed 70 meters. On the catchment scale, the average simulated amount of tritium taken up by vegetation was not impacted by lateral flow, but smaller scale spatial variability in tritium uptake increased with the inclusion of lateral flow. Simulated tritium uptake was most sensitive to changes in vegetation cover, and was less sensitive to differences in soil properties (e.g. field capacity, hydraulic conductivity and root distribution). When integrated over the study area, the simulation of solute uptake by a mixed forest in Coastal Pain soils was not sensitive to inclusion of subsurface lateral flow of water.
DE: 0400 Biogeosciences
DE: 1818 Evapotranspiration
DE: 1875 Unsaturated zone
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly