Computer simulations of the forest-fire model

We present results of simulations of the forest-fire model proposed by P. Bak et al. containing a tree growth rate p and fire spreading to nearest neighbors. The space-time structure of the fire and the scaling properties of the forest clusters show that the model cannot be critical in the limit p → 0. Instead we observe regular and quasideterministic spiral-shaped fire fronts. We present a deterministic forest-fire model that helps understand the origin of these spirals.