  The role of forest heterogeneity in the long-term, large-scale dynamics of
forest fires is investigated by means of a cellular automata model and mean
field approximation. Heterogeneity was conceived as trees (or acres of forest)
with distinct strengths of resistance to burn. The scaling analysis of
fire-size and fire-lifetime frequency distributions in the non-interacting fire
steady-state limit indicates the breakdown of the power-law behavior whenever
the resistance strength parameter R exceeds a certain value. For higher
resistant strength, exponential behavior characterizes the frequency
distributions, while power-law like behavior was observed for the lower
resistant case in the same manner as reported in the literature for a
homogeneous counterpart model. For the intermediate resistance strength,
however, it may be described either by a stretched exponential or by a
power-law plot whenever the fraction of recovering empty cells by susceptible
trees not-exceeds or exceeds a certain threshold respectively, also suggesting
a dynamical percolation transition with respect to the stationary forest
density.
