Rubisco limited
Adopted after the dissertation of Stephen Sitch
where
- C3 pathway:
- C4 pathway:
Carboxylation capacity of Rubisco VR will be calculated by optimizing daily assimilation And (see Photosynthesis).
This is based on the ‘strong optimality hypothesis’ by Haxeltine (1996), Dewar (1996) and Prentice (2000) that nitrogen content and Rubisco activity of leaves vary both seasonally and with canopy position in such a way as to maximize net photosynthesis.
Components are
- θ = 0.7 is a constant,
- KO and KC are Michaelis-Menten half-saturation constants,
- pi is the internal partial pressure of CO2 given as Pi = λ· pa, pa is ambient partial pressure,
- Γ* is the carbon dioxide compensation point.
The kinetic parameters KO, KC and τ are temperature dependent; their temperature dependence is computed as
where k25 is the value of the parameter at 25°C and Q10 is the relative change in the parameter for a 10°C increase in temperature (T). (Haxeltine & Prentice, 1996)
Carbon compensation point is determined with the partial pressure of
oxygen pO2 and τ:
τ in the code is calculated in source:trunk/src/lpj/photosynthesis.c as
and reflects the ability of Rubisco to discriminate between CO2 and O2.