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As various methods for precision inventories, including light detection and ranging (LiDAR), are becoming increasingly common in forestry, planning at the individual-tree level is becoming more viable. In this study, we present a method for finding the optimal thinning times for individual trees from an economic perspective. The method utilizes a forest growth model based on individual trees that has been fitted to Norway spruce (Picea abies (L.) Karst.) stands in northern Sweden. We find that the optimal management strategy is to thin from above (i.e., harvesting trees that are larger than average). We compare our optimal strategy with a conventional management strategy and find that the optimal strategy results in approximately 20% higher land expectation value. Furthermore, we find that for the optimal strategy, increasing the discount rate will reduce the final harvest age and increase the basal area reduction. Decreasing the cost to initiate a thinning (e.g., machinery-related transportation costs) increases the number of thinnings and delays the first thinning. Key words: forest management, optimization, precision forestry, simulation, thinning. La planification a l'echelle de l'arbre devient de plus en plus viable a mesure qu'augmente le recours a diverses methodes d'inventaire de precision en foresterie, telles que le lidar (<>). Dans cette etude, nous presentons une methode visant a determiner les periodes optimales d'application d'une eclaircie pour les arbres individuels d'un point de vue economique. La methode utilise un modele de croissance forestiere a l'echelle de l'arbre qui a ete ajuste a des peuplements d'epicea commun (Picea abies (L.) Karst.) du nord de la Suede. Nous avons trouve que la strategie d'amenagement optimale consiste a eclaircir par le haut, c'est-a-dire a recolter des arbres plus gros que la moyenne. Nous avons compare notre strategie optimale a une strategie d'amenagement conventionnelle et avons constate qu'elle produit une augmentation de la valeur actualisee des terres d'environ 20 %. De plus, lorsque la strategie optimale est associee a une augmentation du taux d'actualisation, l'age de la recolte finale diminue et le prelevement en surface terriere augmente. Une diminution des couts associes a l'eclaircie (p. ex., les couts de transport mecanise) augmente le nombre d'eclaircies et retarde l'application de la premiere eclaircie. Mots-cles: amenagement forestier, optimisation, foresterie de precision, simulation, eclaircie., Introduction Given the ecological and economic importance of forests, it is not surprising that much effort has been invested in developing and improving forestry practices. Increasingly common use of remote [...]

Ground-based mechanized forestry requires the traversal of terrain by heavy machines. The routes that they take are often called 'machine trails' and are created by removing trees from the trail and placing the logs outside it. Designing an optimal machine trail network is a complex locational problem that requires understanding how forestry machines can operate on the terrain, as well as the trade-offs between various economic and ecological aspects. Machine trail designs are currently created manually based on intuitive decisions about the importance, correlations, and effects of many potentially conflicting aspects. Badly designed machine trail networks could result in costly operations and adverse environmental impacts. Therefore, this study was conducted to develop a holistic optimization framework for machine trail network design. Key economic and ecological objectives involved in designing machine trail networks for mechanized cut-to-length operations are presented, along with strategies for simultaneously addressing multiple objectives while accounting for the physical capabilities of forestry machines, the impact of slope, and the operating costs. Ways of quantitatively formulating and combining these different aspects are demonstrated, together with examples showing how the optimal network design changes in response to various inputs. Key words: mathematical modeling, forest engineering, machine trail network, environmental impact, logistics. L'exploitation forestiere mecanisee necessite que la machinerie lourde se deplace sur le terrain. Les chemins qu'elle emprunte sont souvent appeles des sentiers de machines et sont crees en enlevant les arbres et en placant les billes sur le cote du sentier. La conception d'un reseau optimal de sentiers de machines est un probleme complexe de localisation qui exige de comprendre de quelle facon la machinerie forestiere peut operer sur le terrain, ainsi que les compromis entre divers aspects economiques et ecologiques. La conception des sentiers de machines est actuellement realisee manuellement sur la base de decisions intuitives au sujet de l'importance, de la correlation et des effets de plusieurs aspects potentiellement antagonistes. Les sentiers de machines mal concus pourraient engendrer des operations couteuses et avoir des impacts nefastes sur l'environnement. Par consequent, cette etude a ete realisee dans le but de developper un cadre d'optimisation holistique pour la conception des reseaux de sentiers de machines. Les objectifs ecologiques et economiques cles retenus dans la conception de reseaux de sentiers de machines pour des operations mecanisees de recolte par bois tronconnes sont presentes, ainsi que les strategies pour repondre simultanement a plusieurs objectifs tout en tenant compte des capacites physiques de la machinerie forestiere, de l'impact de la pente et des couts d'operation. Des facons de combiner et de formuler quantitativement ces differents aspects sont illustrees avec des exemples montrant comment la conception du reseau optimal change en reaction a differents intrants. [Traduit par la Redaction] Mots-cles : modelisation mathematique, genie forestier, reseau de sentiers de machines, impact environnemental, logistique., 1. Introduction In ground-based forestry, large volumes of timber are extracted from forest to roadside using heavy vehicles. When conducting 'close-to-nature' forestry, the machines should ideally be able to operate [...]

In conventional mechanized cut-to-length systems, a harvester fells and cuts trees into logs that are stored on the ground until a forwarder picks them up and carries them to landing sites. A proposed improvement is to place logs directly into the load spaces of transporting machines as they are cut. Such integrated loading could result in cost reductions, shorter lead times from stump to landing, and lower fuel consumption. However, it might also create waiting times for the machines involved, whereas multifunctional machines are likely to be expensive. Thus, it is important to analyze whether or not the advantages of any changes outweigh the disadvantages. The conventional system was compared with four potential systems, including two with autonomous forwarders, using discrete-event simulation with stochastic elements in which harvests of more than 1000 final felling stands (containing in total 1.6 million [m.sup.3]) were simulated 35 times per system. The results indicate that harwarders have substantial potential (less expensive on ≥80% of the volume and fuel consumption decreased by ≥18%) and may become competitive if key innovations are developed. Systems with cooperating machines have considerably less potential, limited to very specific stand conditions. The results conform with expected difficulties in integrating processing and transporting machines' work in variable environments. Resume: Dans les procedes mecanises conventionnels de recolte par bois tronconne, une abatteuse-faconneuse coupe et tronconne les arbres en billes qui sont entreposees au sol jusqu'a ce qu'un porteur les ramasse et les transporte jusqu'a une jetee. Une amelioration qui a ete proposee consiste a placer les billes directement dans l'espace de chargement des porteurs a mesure qu'elles sont coupees. Un tel chargement integre pourrait reduire les couts, le delai entre la souche et la jetee ainsi que la consommation de carburant. Cependant, cela peut egalement engendrer des periodes d'attente pour la machinerie concernee alors que les machines multifonctionnelles risquent d'etre onereuses. Par consequent, il est important de determiner si les avantages des changements l'emportent sur les desavantages ou non. Le procede conventionnel a ete compare a quatre procedes potentiels, incluant deux procedes avec porteurs autonomes, en utilisant la simulation d'evenements discrets avec des elements stochastiques au moyen de laquelle la coupe definitive de plus de 1 000 peuplements (contenant au total 1,6 million de [m.sup.3]) a ete simulee 35 fois avec chaque procede. Les resultats indiquent que les machines multifonctionnelles ont beaucoup de potentiel (plus economiques pour [greater than or equal to]80 % du volume et consommation de carburant reduite de ≥18 %) et peuvent devenir competitives si des innovations cles sont developpees. Les procedes qui impliquent la cooperation de differentes machines ont beaucoup moins de potentiel et sont limites a des conditions de peuplement tres specifiques. Les resultats correspondent aux difficultes anticipees par l'integration des machines qui effectuent la transformation et le transport dans des environnements variables. [Traduit par la Redaction], Introduction During the last 50 years, forest operations have been subject to many steps of mechanization. The forces driving mechanization have included labor shortages, an aspiration to perform forestry operations [...]