Trade-off analysis for multi-objective boreal forest thinning

Abstract Thinning is an essential forest management activity because it recovers capital from forest stands, increases the relative value growth of remaining trees, and affects other ecosystem services. Optimizing the selection of harvested and retained trees requires an understanding of how thinning decisions affect different objectives. We studied the trade-offs between multiple indicators of economic benefits, landscape amenity, tree size inequality, spatial order of trees, species mixture, and retention value in 35 field plots in the Finnish boreal forest. Tree selection was optimized for single and multiple goals, limiting only the basal area of remaining trees so that the solutions were practical and legal. Maximizing economic objectives resulted in a “thinning from above” treatment, i.e. selecting larger trees for harvest. Maximizing tree retention index or landscape amenity resembled a “thinning from below” treatment. Maximizing ecological indicators favored leaving deciduous trees standing. Fixed harvesting rules cannot achieve all objectives because, e.g. optimizing relative value growth conflicts with most environmental indicators. Reasonable tree selection can be achieved through multicriteria optimization as shown in this paper. Overall, this approach can improve precision forestry, where forest operations are planned at detailed scales to account for within-stand variation in forest structure.