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

Abstract

[1] 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.

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

“…Understanding the mechanisms that shape plot level transpiration and how they influence forests' response to disturbance will help modelers eliminate errors and better capture changes to water and C fluxes as forests are shaped by natural succession and other disturbances, as well as climate and land-use change. The incorporation of advanced hydrodynamic models for hydraulic functional-type-specific stomatal parameterization (e.g., Finite Elements Tree-Crown Hydrodynamic model (FETCH) [Bohrer et al, 2005] or Expert-N [Janott et al, 2011]) could help resolve these differences and improve the quality of simulated ET by land surface models, in general, and particularly in forests undergoing intermediate disturbance. …”

“…This finding supported our fourth hypothesis, that predisturbance and postdisturbance transpiration are distinct in such a manner that adjustment on the basis of LAI alone is not sufficient to adequately represent disturbance in land surface models. Additionally, the PM model residual analysis demonstrated significant interactions of soil water potential with species and size, and analysis of hysteresis revealed significant interactions between soil water potential and tree size indicating that improving the representation of the mechanisms by which soil moisture affects stomatal conductance, and species or hydraulic functional-type parameterization could improve model performance [Bohrer et al, 2005;Grant et al, 2006;Janott et al, 2011;Weng and Luo, 2008]. There was a significant decline in transpiration postdisturbance, beyond the extent that is predicted by the differences in atmospheric forcings and LAI, and the hysteresis analysis revealed important differences between species behavior in disturbed and undisturbed plots.…”

“…The imbalance between the rates of water demand in the leaf and water supply from the soil imposes hydrodynamic limitations on stomatal conductance [Bohrer et al, 2005;Damour et al, 2010;McCulloh and Sperry, 2005;Tyree and Sperry, 1989]. Hydraulic limitations have recently been linked to the hysteretic relationship between transpiration (or stomatal conductance) and vapor pressure deficit (VPD) Novick et al, 2014;O'Brien et al, 2004;Unsworth et al, 2004;Verbeeck et al, 2007a;Zhang et al, 2014].…”

Xylem embolism refilling and resilience against drought‐induced mortality in woody plants: processes and trade‐offs

“…Williams et al 1996;Bohrer et al 2005), ecosystem models (Duursma and Medlyn 2012;Christoffersen et al 2016), and terrestrial biosphere models (Xu et al 2016). However, to date, representations of alternative strategies for repairing embolisms are lacking in existing models, even though the impact may be considerable (Sperry and Love, 2015).…”

Reservoir-on-a-Chip (ROC): A new paradigm in reservoir engineering

“…5,6,11,12 It is now possible to reconstruct the 3D pore space using micro-computed tomography (micro-CT), 5,6,[11][12][13][14] focused ion beam-scanning electron microscope (FIB-SEM), 13 nuclear magnetic resonance (NMR) imaging 15,16 or ultrasonic scanning. 17 Multiphase flow properties are calculated with direct numerical simulations on 3D reconstructed pore space using the finite element method (FEM), 18,19 finite volume method (FVM), 20,21 finite difference method (FDM) 22 or lattice Boltzmann method (LBM). [23][24][25][26][27] However, these types of simulations are computationally expensive, limited to small sample sizes and not possible to scale-up to actual field scale.…”