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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.
Copyright 2005 by the American Geophysical Union.
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