Current issue: 53(2)

Under compilation: 53(3)

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Articles containing the keyword 'threshold accepting'.

Category: Research article

article id 1232, category Research article
Pete Bettinger, Mehmet Demirci, Kevin Boston. (2015). Search reversion within s-metaheuristics: impacts illustrated with a forest planning problem. Silva Fennica vol. 49 no. 2 article id 1232. https://doi.org/10.14214/sf.1232
Highlights: The interruption of the sequence of events used to explore a solution space and develop a forest plan, and the re-initiation of the search process from a high-quality, known starting point (reversion) seems necessary for some s-metaheuristics; When using a s-metaheuristic, higher quality forest plans may be developed when the reversion interval is around six iterations of the model.
The use of a reversion technique during the search process of s-metaheuristics has received little attention with respect to forest management and planning problems. Reversion involves the interruption of the sequence of events that are used to explore the solution space and the re-initiation of the search process from a high-quality, known starting point. We explored four reversion rates when applied to three different types of s-metaheuristics that have previously shown promise for the forest planning problem explored, threshold accepting, tabu search, and the raindrop method. For two of the s-metaheuristics, we also explored three types of decision choices, a change to the harvest timing of a single management unit (1-opt move), the swapping of two management unit’s harvest timing (2-opt moves), and the swapping of three management unit’s harvest timing (3-opt moves). One hundred independent forest plans were developed for each of the metaheuristic / reversion rate combinations, all beginning with randomly-generated feasible starting solutions. We found that (a) reversion does improve the quality of the solutions generated, and (b) the rate of reversion is an important factor that can affect solution quality.
  • Bettinger, School of Forestry and Natural Resources, 180 E. Green Street, University of Georgia, Athens, Georgia, USA 30602 ORCID ID:E-mail: pbettinger@warnell.uga.edu (email)
  • Demirci, General Directorate of Forestry, Ministry of Forest and Water Affairs, Republic of Turkey ORCID ID:E-mail: mehmetdemirci@yahoo.com
  • Boston, Department of Forest Engineering, Resources and Management, College of Forestry, Oregon State University, USA ORCID ID:E-mail: Kevin.Boston@oregonstate.edu
article id 474, category Research article
Tero Heinonen, Mikko Kurttila, Timo Pukkala. (2007). Possibilities to aggregate raster cells through spatial optimization in forest planning. Silva Fennica vol. 41 no. 1 article id 474. https://doi.org/10.14214/sf.474
This study divided the forest into raster cells and used these cells as calculation units in optimisation instead of predefined stand compartments. It was hypothesized that raster cells would result in feasible treatment units and more efficient utilization of the production potential of the forest when spatial optimisation is used to compile the plan. The optimization problems of this study included both ecological and economic objectives. The raster cells were hexagons (721 m2) and their data were derived from traditionally defined forest compartments. Three forest plans were developed by using the rasterized forest, and they were compared to the corresponding forest plans developed by using compartments. Cutting areas were aggregated in all plans, by maximizing the proportion of the boundaries between two adjacent calculation units that were both cut during the same management period, and by minimizing the proportion of cut-uncut boundaries. In the first plan, only cutting areas were aggregated. In the second and third plan, also old forests were aggregated by using two different spatial objectives. The first maximized the proportion of the boundary between adjacent calculation units that were both considered as old forest. The second objective maximized the mean of the neighbourhood minima of the calculation units’ old forest indices. The neighbourhood included the calculation unit itself and all the adjacent calculation units. The growing stock volume targets at the end of the 60-year planning period and the cutting volume targets of the three 20-year management periods were set to the same levels in all plans. The results showed that the raster approach was able to aggregate old forest patches and cutting areas similar in shape and size as the conventional approach. When the aggregation of old forest was a management objective, the total old forest area was larger in the raster forest but the mean size of the old forest patches was larger with predefined compartments. The trade-off curve between harvested volume and old forest area was further from the origin for the raster forest.
  • Heinonen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: tero.heinonen@joensuu.fi (email)
  • Kurttila, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail:
  • Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail:
article id 357, category Research article
Elizabeth Dodson Coulter, John Sessions, Michael G. Wing. (2006). Scheduling forest road maintenance using the analytic hierarchy process and heuristics. Silva Fennica vol. 40 no. 1 article id 357. https://doi.org/10.14214/sf.357
The management of low-volume roads has transitioned from focusing on maintenance designed to protect a capital investment in road infrastructure to also include environmental effects. In this study, two models using mathematical programming are applied to schedule forest road maintenance and upgrade activities involving non-monetary benefits. Model I uses a linear objective function formulation that maximizes benefit subject to budgetary constraints. Model II uses a non-linear objective function to maximize the sum of benefits divided by the sum of all costs in a period. Because of the non-linearity of the constraints and the requirements that the decision variables be binary, the solutions to both problem formulations are found using two heuristics, simulated annealing and threshold accepting. Simulated annealing was found to produce superior solutions as compared to threshold accepting. The potential benefit for completing a given road maintenance or upgrade project is determined using the Analytic Hierarchy Process (AHP), a multi-criterion decision analysis technique. This measure of benefit is combined with the economic cost of completing a given project to schedule maintenance and upgrade activities for 225 km (140 miles) of road in forested road systems within western Oregon. This combination of heuristics, cost-benefit analysis, environmental impacts, and expert judgment produces a road management schedule that better fits the current road management paradigm.
  • Coulter, College of Forestry and Conservation, University of Montana, 32 Campus Drive, Missoula, MT 59812, USA ORCID ID:E-mail: elizabeth.coulter@cfc.umt.edu (email)
  • Sessions, Department of Forest Engineering, College of Forestry, Oregon State University, 204 Peavy Hall, Corvallis, OR 97331-5706, USA ORCID ID:E-mail:
  • Wing, Department of Forest Engineering, College of Forestry, Oregon State University, 204 Peavy Hall, Corvallis, OR 97331-5706, USA ORCID ID:E-mail:

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