The final step is now to validate the adjusted model structure
with its parameter set on the basis of data from the
experimental AF sites in Silsoe and Leeds. The calibrated
model was then run to calculate growth trajectories and yields
(under water limitation) for crops and trees within a silvoarable
system over a 30 year tree rotation. The predicted
relative crop yields for the first twelve years (Figure 3)
generally matched the experimental results. This match
between data and simulation results in the agroforestry
situation provides further evidence for the validity for the
modelling concept and calibration philosophy. Recall that so
far the model was not fitted to any data from the agroforestry
stand, but only to data from pure stands of crops or trees.
Thus, the rather good fit of the model to the yields in an
actual agroforestry experiment provides evidence that it
correctly captures the essence of the crop-tree interactions.