Optimal Stomatal Conductance Model of Katul et al. (2010)

Solves the combined Farquhar photosynthesis model for C3 plants along with Fickian diffusion and a stomatal optimization hypothesis that assumes leaves autonomously maximize carbon gain for a given water loss. The model formulation and comparison with field data are described in Katul, G.G., S. Manzoni, S. Palmroth, and R. Oren, 2010, A stomatal optimization theory to describe the effects of atmospheric CO2 on leaf photosynthesis and transpiration, Annals of Botany, 105(3):431-442.Full Manuscript in PDF.

The model components (main calling program is called C3_optimal_Main_Program.m) are all developed in MATLAB and the complete stand-alone files can be downloaded (as a zip-file) from: Matlab_C3_optimal_stomatal_conductance.

the MAIN INPUTS to the model include:

  • FORCING VARIABLES: leaf temperature (T_L), photosynthetically active radiation (Qp), air relative humidity (RH), and atmospheric CO2 (Ca).
  • PHYSIOLOGICAL VARIABLES: These are specified in the subroutine Compute_Parameters_C3.m - the variables are:

    ==> CONSTANTS THAT ARE GENERIC ACROSS SPECIES:

  • Maximum quantum efficiency (e_m, mol/mol; default = 0.08).
  • Leaf absorbtivity for Qp (alpha_p, dimensionless, default = 0.8).
  • Michaelis coefficient for CO2 (Kc, micromol/mol; default = 300).
  • Inhibition constant for O2 (Ko, mmol/mol, default = 300).

    ==> CONSTANTS THAT ARE SPECIES SPECIFIC:

  • Rubisco capacity (Vcmax,25, micromol/m2/s, for pine = 59).
  • Marginal water use efficiency or cost parameter (La, micro-mol/mol/kPa).