Abstract

The paper introduces the risk of fire as part of a stand management optimisation problem for even-aged Pinus sylvestris L. stands in Spain. The study used a simulation-optimisation system, SPINE, to examine the effect of risk of fire on the optimal stand management schedule when maximising soil expectation value (SEV). The simulation sub-system includes a deterministic stand growth and yield simulator based on individual-tree growth and mortality models. The simulator was modified to include stochastic fire occurrence. The simulation subsystem was combined with a non-linear optimisation algorithm to find the optimal management schedule. Five different fire probabilities were analysed (0, 0.5, 1, 2 and 5% five-year fire probabilities). In most calculations, the probability of fire was assumed to be constant over the whole rotation, but an analysis was also conducted in which the probability depended on management and the stage of stand development. The results were computed for discounting rates of 1, 2 and 3%, site indexes of 17, 24 and 30 m (dominant height at 100 years), and 0 to 3 thinnings. The effects of reforestation cost, salvage possibility and regeneration lag were also studied. Increased fire probability caused 15 to 35 years reductions in the optimal rotation length, and also decreased soil expectation value. The effect of fire risk on the timing and intensity of thinnings was less systematic when a constant fire risk was assumed. When fire risk depended on stand structure, increased risk level led to earlier and heavier low thinnings.