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Multiobjective optimization is increasingly used to assist decision‐making in forest management when multiple objectives are considered and conflict with each other. Since forest management problems may deal with combinatorial optimization, as the scale of a problem increases, the computation complexity increases exponentially beyond the practical use of exact methods. We propose a multiple‐objective metaheuristic method, referred to as multiobjective record‐to‐record travel (MRRT), to solve such challenging problems. We examined the performance of MRRT and compared it to a mixed integer programming (MIP) optimizer on a forest supply chain multiobjective optimization problem that simultaneously maximizes net revenues and greenhouse gas emission savings from salvage harvest and utilization of beetle‐killed forest stands. Testing on four cases of different problem sizes showed that MRRT performed satisfactorily in approximating the actual Pareto fronts in terms of convergence and coverage, and the distribution of solutions was approximately uniform. The gap between MRRT and MIP solutions increased as the problem size increased. But MRRT produced all solutions within a reasonable computation time, where the computational advantage over MIP was more apparent for large‐scale test cases. Recommendations for Resource Managers Multiobjective optimization shows trade‐offs among conflicting objectives and assists decision‐making to enhance sustainable forest management. Multiobjective record‐to‐record travel (MRRT) has a simple algorithm structure and easy parameterization process so that it is adaptable to solve various multiobjective optimization problems. MRRT produces high‐quality solutions for large‐scale multiobjective optimization problems within a reasonable computation time, which promotes its applicability in practice.
Ji She; Woodam Chung; Hector Vergara. Multiobjective record‐to‐record travel metaheuristic method for solving forest supply chain management problems with economic and environmental objectives. Natural Resource Modeling 2020, 34, 1 .
AMA StyleJi She, Woodam Chung, Hector Vergara. Multiobjective record‐to‐record travel metaheuristic method for solving forest supply chain management problems with economic and environmental objectives. Natural Resource Modeling. 2020; 34 (1):1.
Chicago/Turabian StyleJi She; Woodam Chung; Hector Vergara. 2020. "Multiobjective record‐to‐record travel metaheuristic method for solving forest supply chain management problems with economic and environmental objectives." Natural Resource Modeling 34, no. 1: 1.
Harvesting mountain pine beetle-infested forest stands in the northern Colorado Rocky Mountains provides an opportunity to utilize otherwise wasted resources, generate net revenues, and minimize greenhouse gas (GHG) emissions. Timber and bioenergy production are commonly managed separately, and their integration is seldom considered. Yet, degraded wood and logging residues can provide a feedstock for bioenergy, while the sound wood from beetle-killed stands can still be used for traditional timber products. In addition, beneficial greenhouse gas emission (GHG) savings are often realized only by compromising net revenues during salvage harvest where beetle-killed wood has a relatively low market value and high harvesting cost. In this study we compared Sequential and Integrated decision-making scenarios for managing the supply chain from beetle-killed forest salvage operations. In the Sequential scenario, timber and bioenergy production was managed sequentially in two separate processes, where salvage harvest was conducted without considering influences on or from bioenergy production. Biomass availability was assessed next as an outcome from timber production managed to produce bioenergy products. In the Integrated scenario, timber and bioenergy production were managed jointly, where collective decisions were made regarding tree salvage harvest, residue treatment, and bioenergy product selection and production. We applied a multi-objective optimization approach to integrate the economic and environmental objectives of producing timber and bioenergy, and measured results by total net revenues and total net GHG emission savings, respectively. The optimization model results show that distinctively different decisions are made in selecting the harvesting system and residue treatment under the two scenarios. When the optimization is fully economic-oriented, 49.6% more forest areas are harvested under the Integrated scenario than the Sequential scenario, generating 12.3% more net revenues and 50.5% more net GHG emission savings. Comparison of modelled Pareto fronts also indicate the Integrated decision scenario provides more efficient trade-offs between the two objectives and performs better than the Sequential scenario in both objectives.
Ji She; Woodam Chung; Hee Han; She; Han. Economic and Environmental Optimization of the Forest Supply Chain for Timber and Bioenergy Production from Beetle-Killed Forests in Northern Colorado. Forests 2019, 10, 689 .
AMA StyleJi She, Woodam Chung, Hee Han, She, Han. Economic and Environmental Optimization of the Forest Supply Chain for Timber and Bioenergy Production from Beetle-Killed Forests in Northern Colorado. Forests. 2019; 10 (8):689.
Chicago/Turabian StyleJi She; Woodam Chung; Hee Han; She; Han. 2019. "Economic and Environmental Optimization of the Forest Supply Chain for Timber and Bioenergy Production from Beetle-Killed Forests in Northern Colorado." Forests 10, no. 8: 689.
Operational studies are necessary to support production and management decisions of forest industries. A time study (TS) approach is widely used in timber harvesting operations to understand the performance of individual harvesting machines as well as the entire system. However, several limitations of the TS approach include the use of generalized utilization rates, incapability of capturing interactions among equipment, and model extrapolation in sensitivity analysis. In this study, we demonstrated the use of discrete event simulation (DES) techniques in modeling a ground-based timber harvesting system, and compared the DES results with those of the TS model developed with the same observed data. Although both TS and DES models provided similar estimation results for individual machine cycle times and productivities, the estimated machine utilization rates were somewhat different due to the difference in synthesizing machine processes in each approach. Our sensitivity analysis and model expansion to simulate a hypothetical harvesting system suggest that the DES approach may become an appropriate method for analyzing complex systems especially where interactions among different machine processes are unknown.
Ji She; Woodam Chung; David Kim. Discrete-Event Simulation of Ground-Based Timber Harvesting Operations. Forests 2018, 9, 683 .
AMA StyleJi She, Woodam Chung, David Kim. Discrete-Event Simulation of Ground-Based Timber Harvesting Operations. Forests. 2018; 9 (11):683.
Chicago/Turabian StyleJi She; Woodam Chung; David Kim. 2018. "Discrete-Event Simulation of Ground-Based Timber Harvesting Operations." Forests 9, no. 11: 683.
Two ground-based timber harvesting methods have been commonly used for beetle-kill salvage treatments after a bark beetle epidemic in northern Colorado. A “lop and scatter” method uses a mobilized stroke delimber to delimb and buck trees at the stump, leaving tree tops and limbs on the forest floor, while a whole-tree harvesting method brings the entire tree to the landing where it is delimbed and bucked, and thus produces logging residue piles at the landing as a byproduct. We conducted a detailed comparative time study of the two harvesting methods to develop productivity and cost models and compared the performance of the two methods under various site conditions. We applied the productivity and cost models to lodgepole pine forest stands totaling 3400 hectares of the Colorado State Forest State Park to estimate salvage harvesting costs for each forest stand and identify the least costly harvesting options. The results show that the estimated stump-to-truck timber production costs were $30.00 per oven dry ton (odt) for lop and scatter and $23.88 odt−1 for the whole-tree method in our study harvest unit. At the forest level, the estimated average stump-to-truck costs were $54.67 odt−1 and $56.95 odt−1 for lop and scatter and whole-tree harvesting, respectively. Skidding distance and downed trees affect the harvesting costs of both methods, but their influence appears to be more significant on the whole-tree method.
Hee Han; Woodam Chung; Ji She; Nathaniel Anderson; Lucas Wells. Productivity and Costs of Two Beetle-Kill Salvage Harvesting Methods in Northern Colorado. Forests 2018, 9, 572 .
AMA StyleHee Han, Woodam Chung, Ji She, Nathaniel Anderson, Lucas Wells. Productivity and Costs of Two Beetle-Kill Salvage Harvesting Methods in Northern Colorado. Forests. 2018; 9 (9):572.
Chicago/Turabian StyleHee Han; Woodam Chung; Ji She; Nathaniel Anderson; Lucas Wells. 2018. "Productivity and Costs of Two Beetle-Kill Salvage Harvesting Methods in Northern Colorado." Forests 9, no. 9: 572.