Functions used to scale from tissue conductivity to conductance of different elements of the continuum.

hydraulics_maximumSoilPlantConductance(krhizomax, krootmax, kstemmax, kleafmax)

hydraulics_soilPlantResistances(
  psiSoil,
  psiRhizo,
  psiStem,
  PLCstem,
  psiLeaf,
  krhizomax,
  n,
  alpha,
  krootmax,
  rootc,
  rootd,
  kstemmax,
  stemc,
  stemd,
  kleafmax,
  leafc,
  leafd
)

hydraulics_averageRhizosphereResistancePercent(
  krhizomax,
  n,
  alpha,
  krootmax,
  rootc,
  rootd,
  kstemmax,
  stemc,
  stemd,
  kleafmax,
  leafc,
  leafd,
  psiStep = -0.01
)

hydraulics_findRhizosphereMaximumConductance(
  averageResistancePercent,
  n,
  alpha,
  krootmax,
  rootc,
  rootd,
  kstemmax,
  stemc,
  stemd,
  kleafmax,
  leafc,
  leafd,
  initialValue = 0
)

hydraulics_taperFactorSavage(height)

hydraulics_terminalConduitRadius(height)

hydraulics_referenceConductivityHeightFactor(refheight, height)

hydraulics_maximumStemHydraulicConductance(
  xylemConductivity,
  refheight,
  Al2As,
  height,
  taper = FALSE
)

hydraulics_rootxylemConductanceProportions(L, V)

Arguments

krhizomax

Maximum rhizosphere hydraulic conductance (defined as flow per leaf surface unit and per pressure drop).

krootmax

Maximum root xylem hydraulic conductance (defined as flow per leaf surface unit and per pressure drop).

kstemmax

Maximum stem xylem hydraulic conductance (defined as flow per leaf surface unit and per pressure drop).

kleafmax

Maximum leaf hydraulic conductance (defined as flow per leaf surface unit and per pressure drop).

psiSoil

Soil water potential (in MPa). A scalar or a vector depending on the function.

psiRhizo

Water potential (in MPa) in the rhizosphere (root surface).

psiStem

Water potential (in MPa) in the stem.

PLCstem

Percent loss of conductance (in %) in the stem.

psiLeaf

Water potential (in MPa) in the leaf.

n, alpha

Parameters of the Van Genuchten function (rhizosphere vulnerability curve).

rootc, rootd

Parameters of the Weibull function for roots (root xylem vulnerability curve).

stemc, stemd

Parameters of the Weibull function for stems (stem xylem vulnerability curve).

leafc, leafd

Parameters of the Weibull function for leaves (leaf vulnerability curve).

psiStep

Water potential precision (in MPa).

averageResistancePercent

Average (across water potential values) resistance percent of the rhizosphere, with respect to total resistance (rhizosphere + root xylem + stem xylem).

initialValue

Initial value of rhizosphere conductance.

height

Plant height (in cm).

refheight

Reference plant height of measurement of xylem conductivity (in cm).

xylemConductivity

Xylem conductivity as flow per length of conduit and pressure drop (in kg·m-1·s-1·MPa-1).

Al2As

Leaf area to sapwood area (in m2·m-2).

taper

A boolean flag to indicate correction by taper of xylem conduits (Christoffersen et al. 2017).

L

Vector with the length of coarse roots (mm) for each soil layer.

V

Vector with the proportion [0-1] of fine roots within each soil layer.

Value

Values returned for each function are:

  • hydraulics_maximumSoilPlantConductance: The maximum soil-plant conductance, in the same units as the input segment conductances.

  • hydraulics_averageRhizosphereResistancePercent: The average percentage of resistance due to the rhizosphere, calculated across water potential values.

  • hydraulics_findRhizosphereMaximumConductance: The maximum rhizosphere conductance value given an average rhizosphere resistance and the vulnerability curves of rhizosphere, root and stem elements.

  • hydraulics_taperFactorSavage: Taper factor according to Savage et al. (2010).

Details

Details of the hydraulic model are given in the medfate book

References

Christoffersen, B. O., M. Gloor, S. Fauset, N. M. Fyllas, D. R. Galbraith, T. R. Baker, L. Rowland, R. A. Fisher, O. J. Binks, S. A. Sevanto, C. Xu, S. Jansen, B. Choat, M. Mencuccini, N. G. McDowell, and P. Meir. 2016. Linking hydraulic traits to tropical forest function in a size-structured and trait-driven model (TFS v.1-Hydro). Geoscientific Model Development Discussions 9: 4227–4255.

Savage, V. M., L. P. Bentley, B. J. Enquist, J. S. Sperry, D. D. Smith, P. B. Reich, and E. I. von Allmen. 2010. Hydraulic trade-offs and space filling enable better predictions of vascular structure and function in plants. Proceedings of the National Academy of Sciences of the United States of America 107:22722–7.

Olson, M.E., Anfodillo, T., Rosell, J.A., Petit, G., Crivellaro, A., Isnard, S., León-Gómez, C., Alvarado-Cárdenas, L.O., and Castorena, M. 2014. Universal hydraulics of the flowering plants: Vessel diameter scales with stem length across angiosperm lineages, habits and climates. Ecology Letters 17: 988–997.

Author

Miquel De Cáceres Ainsa, CREAF