Optimising the management of Scots pine (Pinus sylvestris L.) stands in Spain based on individual-tree models

The article describes a simulation-optimisation system, SPINE, for the management of Pinus sylvestris L. stands in Spain. The simulation sub-system is based on an individual-tree diameter growth model, a static individual-tree height model, and models for the self-thinning limit and the probability of a tree to survive for the coming 5-year period. The simulation sub-system was combined with the optimisation algorithm developed by Hooke and Jeeves. The combined simulation-optimisation system is able to find the optimal timing and intensity of thinnings and the optimal time to commence regenerative cuts. The set of regenerative cuts consisted of a preparatory cut, a seed cut 10 years later and a final cut 20 years after the preparatory cut. The decision variables were thinning times, expressed as years since stand establishment or previous thinning, and the remaining stand basal area after each thinning. The system was used to find optimal management schedules of Pinus sylvestris stands on site indices 17, 24 and 30 m (dominant height at 100 years). When soil expectation value with 2% discounting rate was maximised, the optimum management schedule included five thinnings on all site indices. The optimal rotations from stand establishment to the final cut were 119, 90 and 94 years, respectively, on site indices 17, 24, 30 m. On all sites, the optimal management schedules were sensitive to the discounting rate, management objective (soil expectation value, forest rent or mean annual harvest) and fixed harvesting costs. Changes of up to 30 percent from the optimal value in a single decision variable did not affect much the soil expectation value. Optimisation de l'aménagement des peuplements de pin sylvestre en Espagne basée sur des modèles simulant la croissance individuelle des arbres. L'article décrit un système de simulation et optimisation, SPINE, pour la sylviculture des peuplements de pin sylvestre en Espagne. Le sous-système de simulation est basé sur un modèle de croissance en diamètre et un modèle statique de centrés-individu, et des modèles pour la limite d'éclaircie naturelle et la probabilité de survie pendant la période des 5 années suivantes. Le sous-système de simulation était combiné avec l'algorithme d'optimisation développé par Hooke et Jeeves. La combinaison des systèmes simulation-optimisation est capable de trouver le rythme et l'intensité optimale des éclaircies ainsi que le temps optimal pour commencer les coupes de régéneration. Les co