Power-law fire size distributions from simple local rules
Drossel-Schwabl model: each empty cell grows a tree with prob p; each tree ignites spontaneously with prob f. Fire spreads to adjacent trees. In the limit p/f → ∞, the system self-organizes to criticality — fire sizes follow a power law P(s)~s-τ with τ≈1.2 in 2D.