HR: 0800h
AN: H51C-0657    [Abstracts]
TI: Modeling Plant-Scale Root Zone Water Dynamics in an Oak Savanna
AU: * Chen, X
EM: chenxy@berkeley.edu
AF: University of California, Department of Civil and Environmental Engineering, Berkeley, CA 94720, United States
AU: * Chen, X
EM: chenxy@berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management, Berkeley, CA 94720, United States
AU: Miller, G
EM: gmiller@berkeley.edu
AF: University of California, Department of Civil and Environmental Engineering, Berkeley, CA 94720, United States
AU: Miller, G
EM: gmiller@berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management, Berkeley, CA 94720, United States
AU: Rubin, Y
EM: rubin@ce.berkeley.edu
AF: University of California, Department of Civil and Environmental Engineering, Berkeley, CA 94720, United States
AU: Baldocchi, D
EM: baldocchi@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management, Berkeley, CA 94720, United States
AB: Study of water exchange between soil, plants, and the atmosphere in response to seasonal or periodic droughts is critical to modeling the hydrologic cycle and biogeochemical processes in water-controlled ecosystems. The difficulties in such studies arise from insufficient understanding of the complex interactions between the various processes and their scale-dependence. The purpose of our study is to establish and calibrate a plant biophysical model that couples plant-soil and plant-atmospheric interactions to calculate the water exchange through the soil-plant-atmosphere continuum at a plant scale (~10 m2), with the regulation of root water uptake and evaporative fluxes by water deficits and climatic conditions explicitly considered. The complexity required for modeling water dynamics at the plant scale is investigated in this study. We start with coupling a big-leaf biophysical model with a bucket soil water balance model, with soil water loss regulated by soil water availability in a linear fashion. The alternative biophysical models with increasing complexities include the dual-source model that divide the canopy into shaded and sunlit parts and a multi-layer 1-D model with sophisticated radiation transfer and energy balance modules. The level of detail in subsurface water dynamics is adjusted by changing the dimensionality of the Richard's equation. The impact of soil water availability on water loss is modified to a nonlinear pattern as desired. The models are calibrated and compared using a cluster of measurements collected on single trees, which includes multiple soil moisture probes that monitor soil moisture profile vertically and laterally and sap flow sensors at different tree heights for measuring tree transpiration. This study forms the basis for scaling up the water dynamics to a stand scale (~100 to ~10000 m2) or other larger scales.
DE: 1818 Evapotranspiration
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1876 Water budgets
SC: Hydrology [H]
MN: 2007 Fall Meeting