Stomatal Conductance

The stomatal conductance process computes conductance to CO2 (Gₛ). Available implementations are:

• Medlyn;
• Tuzet;
• ConstantGs.

Standalone Model

using PlantBiophysics, PlantSimEngine, PlantMeteo, Dates

meteo = Atmosphere(
    T=25.0,
    Wind=1.0,
    P=101.3,
    Rh=0.5,
    duration=Hour(1),
)

scene = leaf_scene(
    Medlyn(0.03, 12.0);
    status=Status(A=20.0, Cₛ=400.0, Dₗ=1.5),
    environment=meteo,
)

run!(scene)
only(model_objects(scene; scale=:Leaf)).status.Gₛ

0.5698979485566357

Timestep Contract

Stomatal conductance models declare a required range of one minute to six hours and prefer one hour:

PlantSimEngine.timestep_hint(Medlyn(0.03, 12.0))

(required = (Dates.Minute(1), Dates.Hour(6)), preferred = Dates.Hour(1))

A scenario can override the cadence:

spec = ModelSpec(Medlyn(0.03, 12.0); on=One(scale=:Leaf), every=Hour(3))
spec.timestep

3 hours

Tuzet Water Stress

Tuzet adds leaf water potential (Ψₗ) to the conductance response. Its parameters control the potential at half closure and the steepness of the closure response.

tuzet_scene = leaf_scene(
    Tuzet(0.03, 12.0, -1.5, 2.0, 30.0);
    status=Status(A=20.0, Cₛ=400.0, Ψₗ=-1.0),
    environment=meteo,
)
run!(tuzet_scene)
only(model_objects(tuzet_scene; scale=:Leaf)).status.Gₛ

0.5278091948530834

Use inputs(model) and outputs(model) to inspect each model's variable contract.