Shared components in the P Model module

The standard and subdaily forms of the P Model share a great deal of theory and many pyrealm code structures. This section of the documentation describes the key shared concepts and tools used for fitting both forms of the P Model. These components are:

• Calculation of the photosynthetic environment, which calculates critical photosynthetic variables from the model forcing variable.

• Calculation of optimal chi, defining the optimal ratio of carbon dioxide partial pressure inside the leaf compared to the surrounding air. This value captures the trade off between water loss and carbon acquisition.

• Estimation of quantum yield efficiency, which sets the efficiency with which a plant converts absorbed light radiation into captured carbon.

• Estimation of rate limitation on the maximum values of the electron transfer rate and carboxylation capacity, sometimes called \(J_{max}\) limitation.

• The form of the Arrhenius scaling used to calculate the electron transfer rate and carboxylation capacity at standard temperatures. This is central to the Subdaily P Model as the variables \(J_{max}\) and \(V_{cmax}\) need to be converted to a standard temperature to map predictions from the daily scale back to the subdaily scale.

• Approaches to the impacts of soil moisture stress.

• The behaviour of core P Model equations with extreme forcing values.