Adopted after the dissertation of Stephen Sitch

where

• C3 pathway:
• C4 pathway:

Carboxylation capacity of Rubisco V_R will be calculated by optimizing daily assimilation A_nd (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,
• K_O and K_C are Michaelis-Menten half-saturation constants,
• p_i is the internal partial pressure of CO₂ given as P_i = λ· p_a, p_a is ambient partial pressure,
• Γ_* is the carbon dioxide compensation point.

The kinetic parameters K_O, K_C 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.