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plantecophys (version 1.4-6)

FARAO: FARquhar And Opti

Description

The numerical solution of the optimal stomatal conductance model, coupled with the Farquhar model of photosynthesis. The model of Medlyn et al. (2011) is an approximation to this full numeric solution.

Usage

FARAO(
  lambda = 0.002,
  Ca = 400,
  VPD = 1,
  photo = c("BOTH", "VCMAX", "JMAX"),
  energybalance = FALSE,
  C4 = FALSE,
  Tair = 25,
  Wind = 2,
  Wleaf = 0.02,
  StomatalRatio = 1,
  LeafAbs = 0.86,
  ...
)
FARAO2(lambda = 0.002, Ca = 400, energybalance = FALSE, ...)

Arguments

lambda

The marginal cost of water (mol mol-1)

Ca

The CO2 concentration.

VPD

Vapor pressure deficit (kPa)

photo

Which photosynthesis rate should stomata respond to? Defaults to 'BOTH', i.e. the minimum of Vcmax and Jmax limited rates.

energybalance

If TRUE (Default = FALSE), calculates leaf temperature from energy balance (and its effects on photosynthesis as well as leaf transpiration), using PhotosynEB.

C4

If TRUE, uses the C4 photosynthesis routine (AciC4)

Tair

Air temperature (deg C)

Wind

Wind speed (m s-1) (only used if energybalance=TRUE)

Wleaf

Leaf width (m) (only used if energybalance=TRUE)

StomatalRatio

The stomatal ratio (see PhotosynEB) (only used if energybalance=TRUE)

LeafAbs

Leaf absorptance (see PhotosynEB) (only used if energybalance=TRUE)

...

All other parameters are passed to Aci

Details

This model finds the Ci that maximizes A - lambda*E (Cowan & Farquhar 1977, see also Medlyn et al. 2011). The new function FARAO2 is a much simpler (and probably more stable) implementation, based on Buckley et al. 2014 (P,C&E). Both functions are provided, as FARAO has a few more options than FARAO2, at the moment.

References

Buckley, T.N., Martorell, S., Diaz-Espejo, A., Tomas, M., Medrano, H., 2014. Is stomatal conductance optimized over both time and space in plant crowns? A field test in grapevine (Vitis vinifera). Plant Cell Environ doi:10.1111/pce.12343

Cowan, I. and G.D. Farquhar. 1977. Stomatal function in relation to leaf metabolism and environment. Symposia of the Society for Experimental Biology. 31:471-505.

Medlyn, B.E., R.A. Duursma, D. Eamus, D.S. Ellsworth, I.C. Prentice, C.V.M. Barton, K.Y. Crous, P. De Angelis, M. Freeman and L. Wingate. 2011. Reconciling the optimal and empirical approaches to modelling stomatal conductance. Global Change Biology. 17:2134-2144.