Optimizing tree selection for planning cable yarding operations: a multi-objective modelling approach

Abstract

When planning timber harvesting in mountainous areas, selecting the trees to extract is highly challenging. This is due to the need to consider both the forest management plan as well as feasibility aspects of the logging operation. Additionally, the choice using cable yarding systems in steep and difficult terrain increases the complexity and related costs of the harvesting process. The protective function of mountain forests against natural hazards adds another layer of consideration. Decision-makers must strike a balance between maintaining the protective function of the forest directly after cutting and on a long term, while maximizing the economic efficiency of the harvesting operation. In this study, we have developed an optimization model for tree selection using linear mixed programming. The model relies on high-resolution airborne laser scanning data to create a forest inventory through individual tree detection. Constituting the Pareto frontier, by optimizing two primary objectives, 15 optimal trade-off solutions could be identified when minimizing the harvesting area and maximizing the economic benefit of timber harvesting. Four of the solutions were identified, which maintain the maximum protective effect of the remaining forest, with a cumulative basal area ranging from 33.3 to 33.9 m²ha⁻¹, while significantly reducing the economic loss from 17 % to 79.6 % when emphasizing the economic benefit maximization. Furthermore, the model presented four solutions that keep the protective effect above the minimum threshold (cumulative basal area > 30 m²ha⁻¹) while also resulting in positive economic benefits from harvesting. This model presents a method that integrates a multi-objective approach to decision making, considering the practical constraints of cable yarding technology in the process of tree selection in mountainous areas.