HR: 1340h
AN: H53E-0530    [Abstracts]
TI: Do We Need To Consider Plant Hydraulic Architecture in Modeling Evapotranspiration? Lessons From a Coupled Land-Atmosphere Model
AU: * Hoffmann, W A
EM: wahoffma@ncsu.edu
AF: North Carolina State University, Department of Botany Campus Box 7612, Raleigh, NC 27691-7612 United States
AB: Realistic representations of plant water transport are generally absent from land-atmosphere models. In these models, stomata are presumed to respond directly to soil water availability, leading to unrealistic responses of transpiration to soil drying. This also makes these models inadequate for representing, for example, the role of hydraulic lift or water uptake by deep roots. I incorporated a more physically realistic representation of plant water transport into the Community Land Model (CLM). Water transport through the vegetation is driven by the gradient of water potential from the soil to leaf. Rather than responding directly to soil moisture, stomatal conductance is determined by leaf water potential, which in turn is determined by the hydraulic resistance of the soil-plant continuum, soil water potential, and the rate of water loss through the stomata. The new parameterization results in improved simulations of ET, particularly in the seasonal tropics where the original parameterization greatly underestimated ET especially during the dry season. The improved performance is results from the more realistic response of water transport to partial drying of the soil profile. When upper soil layers dry, even a relatively small amount of roots in deeper soil are capable of sustaining substantial transpiration rates. As a result, this model shows increased sensitivity to rooting depth. In contrast, simulations examining the influence of hydraulic lift suggest that this process has little influence on ET.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0466 Modeling
DE: 1813 Eco-hydrology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1847 Modeling
SC: Hydrology [H]
MN: Fall Meeting 2005