Summary:

Maximum Rate of Carboxylation

The maximum rate of carboxylation (Vcmax25) at 25°C varies with foliage nitrogen concentration and specific leaf area. It is calculated as:

Vcmax25 = Ncb * NUEVcmax25

Where:
- Ncb is the nitrogen for carboxylation (g N m-2 leaf)
- NUEVcmax25 is the nitrogen use efficiency for Vcmax25, calculated as 47.3 x 6.25

Vcmax25 also varies with daylength (DYL) using the function f(DYL), which introduces seasonal variation:

f(DYL) = (DYL)^2 / (DYLmax)^2

Where DYL is calculated based on latitude and declination angle, and DYLmax is the maximum daylength for the present-day orbital geometry.

This mechanism allows the model to capture the seasonal changes in the maximum rate of carboxylation.