The effect of the density of candidate roads on solutions in tactical forest planning

In this paper, we inquire into whether, and by how much, the use in tactical planning of a dense set versus a sparse set of candidate roads can reduce the two major costs (construction and transportation) of forest operations. This inquiry is conducted by using an optimal road location model to generate dense and sparse sets of candidate roads for three different problem instances. These problem instances were then solved using a mixed integer representation of the integrated tactical planning problem. The results show that the use of a dense set versus a sparse set of candidate roads, for all three problem instances, yielded solutions with a mean decrease in transportation and construction costs of 34.34% and 6.94%, respectively. The mean increase in revenue was 1.06%, and the mean increase in the objective function value (revenue minus the total road construction and transportation costs) was 5.62%. In addition, the mapped solutions reveal the spatial attributes of a lower versus a higher cost road network: straighter roads and more efficiently located forks within the road network. These results were obtained to illustrate how reductions in the costs of transportation and road construction can be achieved in tactical planning. Key words: forest harvest scheduling, tactical planning, network design, optimal road location, forestry. Dans cet article, nous cherchons a savoir si, et dans quelle mesure, l'utilisation d'un ensemble clairseme versus dense de chemins candidats dans la planification tactique peut reduire les deux principaux couts (construction et transport) associes aux operations forestieres. La recherche a ete realisee en utilisant un modele de localisation optimale des chemins pour generer un ensemble clairseme ou dense de chemins candidats pour trois variations differentes du probleme. Ces variations du probleme ont ensuite ete resolues a l'aide d'une representation partiellement en nombre entier du probleme de planification tactique integree. Les resultats montrent que l'utilisation d'un ensemble dense plutot que clairseme de chemins candidats produit, pour les trois variations du probleme, des solutions qui entrament une diminution moyenne des couts de transport et de construction de respectivement 34,34 % et 6,94 %. Les revenus ont augmente en moyenne de 1,06 % et la fonction d'objectifs (revenus moins cout total de construction et de transport) de 5,62 %. De plus, les solutions cartographiees revelent les caracteristiques spatiales d'un reseau de chemins dont le cout est faible plutot qu'eleve : des chemins plus droits et des embranchements situes de facon plus efficiente a l'interieur du reseau routier. Ces resultats ont ete obtenus afin d'illustrer comment il est possible de reduire les couts de transport et de construction des chemins grace a la planification tactique. [Traduit par la Redaction] Mots-cles: etablissement d'un calendrier de recolte forestiere, planification tactique, conception de reseaux, localisation optimale des chemins, foresterie.
Introduction At the tactical scale of forest management planning, the two greatest costs resulting from the allocation of cutblocks are the construction of forest roads and the transportation of harvested [...]