A multiscale stochastic cellular automata model for dispersion of mountain pine beetles.

We construct a multiscale model of dispersion of mountain pine beetles in western North American forests. Dispersion is modelled at a macroscale (regional scale) by a novel nonlinear stochastic process for population density. This is coupled to a microscale (tree scale) model of population dynamics using a sequential approach, which assumes that dispersion occurs on a slower time scale than local dynamics. We conduct a numerical investigation of the multiscale model properties. While the model depends on a relatively small number of parameters, it can produce a wide range of behaviours, including dispersion patterns qualitatively similar to those of mountain pine beetle infestations. We also conduct a Bayesian calibration for key parameters in the model using synthetic and real data.