Influences of finite-size effects on the self-organized criticality of forest-fire model

The influences of finite-size effects on the self-organized criticality (SOC) of the traditional forest-fire model are investigated by means of a new method. The forest size is originally set to a value much greater than the correlation length of the forest. Finite-size effects are then studied by equally dividing the forest into more and more separate subsystems on condition that the forest size, igniting probability and planting probability are invariant. A new phenomenon, i.e. the finite-size effects with one-side frequency peak, is observed. The boundary between two neighboring subsystems can be regarded as a firebreak. The concept of 'separation ability' is introduced to represent the probability for the firebreak to block off the fire successfully. Restraining effects of separation ability on finite-size effects are analyzed. Finite-size effects and separation ability, as well as their relations are found to have practical importance to the actual forest-fire protection.