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WATER RESOURCES RESEARCH, VOL. 41, W11404, doi:10.1029/2005WR004181, 2005

Finite element tree crown hydrodynamics model (FETCH) using porous media flow within branching elements: A new representation of tree hydrodynamics

Gil Bohrer

Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA


Hashem Mourad

Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA


Tod A. Laursen

Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA


Darren Drewry

Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA


Roni Avissar

Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA


Davide Poggi

Nicolas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina, USA


Ram Oren

Nicolas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina, USA


Gabriel G. Katul

Nicolas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina, USA


Abstract

Estimating transpiration and water flow in trees remains a major challenge for quantifying water exchange between the biosphere and the atmosphere. We develop a finite element tree crown hydrodynamics (FETCH) model that uses porous media equations for water flow in an explicit three-dimensional branching fractal tree-crown system. It also incorporates a first-order canopy-air turbulence closure model to generate the external forcing of the system. We use FETCH to conduct sensitivity analysis of transpirational dynamics to changes in canopy structure via two scaling parameters for branch thickness and conductance. We compare our results with the equivalent parameters of the commonly used resistor and resistor-capacitor representations of tree hydraulics. We show that the apparent temporal and vertical variability in these parameters strongly depends on structure. We suggest that following empirical calibration and validation, FETCH could be used as a platform for calibrating the “scaling laws” between tree structure and hydrodynamics and for surface parameterization in meteorological and hydrological models.

Received 12 April 2005; accepted 28 July 2005; published 2 November 2005.

Keywords: atmospheric modeling; FEM; plant hydraulics; porous media flow; resistor-capacitor representation.

Index Terms: 1813 Hydrology: Eco-hydrology; 1818 Hydrology: Evapotranspiration; 1851 Hydrology: Plant ecology (0476); 2753 Magnetospheric Physics: Numerical modeling; 3322 Atmospheric Processes: Land/atmosphere interactions (1218, 1631, 1843).

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Citation: Bohrer, G., H. Mourad, T. A. Laursen, D. Drewry, R. Avissar, D. Poggi, R. Oren, and G. G. Katul (2005), Finite element tree crown hydrodynamics model (FETCH) using porous media flow within branching elements: A new representation of tree hydrodynamics, Water Resour. Res., 41, W11404, doi:10.1029/2005WR004181.