Stomatal conductance is currently calculated using the dummy value 1.0 for optimal chi. For calculating g_s, the true internal CO2 partial pressure is needed. This can be calculated for C4 plants using the same equations but a different beta cost, which Colin has suggested should be:
Both Lin et al 2015 and DeKauwe et al 2015 provide estimates for the $g_1$
parameter for C3 and C4 plants, with a ratio of C3/C4 values of around 3. The
$g_1$ parameter is equivalent to $\xi$ in the P model. Given that
$\xi \propto \surd\beta$, a reasonable default for C4 plants is that
$\beta = 146 / 9 \approx 16.222$
So, a new optimal chi function is needed that returns $\chi$ for use in appropriate calculations.
Stomatal conductance is currently calculated using the dummy value 1.0 for optimal chi. For calculating
g_s, the true internal CO2 partial pressure is needed. This can be calculated for C4 plants using the same equations but a different beta cost, which Colin has suggested should be:So, a new optimal chi function is needed that returns$\chi$ for use in appropriate calculations.