Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> A bucket conveyor has buckets which are supported by transverse elements extending between two conveyor belts, each conveyor bucket being connected to the neighboring bucket at the transverse element but without pivotal movement between the buckets at this connection, flexure of the conveyor belts at drive and guide rollers being accommodated by bending of a part of one of the transverse bucket walls of reduced thickness. <s> BIB001 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> A number of approaches to forest management planning are surveyed and analysed. A unified treatment of the various models and optimisation techniques is attempted, aiming at a better understanding of their essential characteristics and interrelationships. Ways of improving computational efficiency are examined. Structures for the forestry submodel are classified into three basic types, and interpreted in terms of network flows. A utilisation / economics submodel, comprising an objective function and constraints representing supply requirements, yield regulation, terminal conditions, and other aspects of the management problem, completes the formulation. A new criterion for yield regulation, based on irreversible investment concepts, is discussed in detail. The optimisation methods proposed in the literature for solving forest planning problems are evaluated, together with other potentially useful techniques and strategies. Topics covered include the use of standard Linear Programming packages, the prospects of decomposition and partitioning methods, the potential for utilising oldest-first and other cutting priorities, the explicit use of time structure in Dynamic Linear Programming and Optimal Control Theory algorithms, and the Hoganson-Rose procedure and its relationship to Lagrangian relaxation. <s> BIB002 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> Implementing forest plans involves decisions regarding the geographic arrangement and timing of management activities, and the design of efficient transportation networks to provide access for these activities. These planning problems have been modeled successfully as mixed integer linear programs. However, these models are difficult to solve with commercial software due to their relatively large number of binary variables. We present a heuristic approach that has solved these problems well. The heuristic rules and a linear programming package interact within a closed system requiring no special user intervention. We describe several applications of this system for decision making in the USDA Forest Service. <s> BIB003 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> Over the last two decades, forest land management practices have changed in response to ecological issues and the need to improve efficiency to remain competitive in emerging global markets. Decision processes have become more open and complex as information and communication technologies change. The OR/MS community is meeting these challenges by developing new modeling strategies, algorithms, and solution procedures that address spatial requirements, multiresource planning, hierarchical systems, multiple objectives, and uncertainty as they pertain to both industrial timberlands and public forests. <s> BIB004 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> This is an overview of operational research work that has been carried out to support strategic forest management planning, short term forest planning, forest operations, and forest fire management. It identifies important unresolved problems and new challenges that could serve as a rich source of problems for both practitioners and researchers. <s> BIB005 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> In 1995, the Pacific Lumber Company contracted with VESTRA Resources to develop a 120-year, 12-period forest-eco system management plan for its properties to meet new California Board of Forestry wildlife, fisheries, and timber resource requirements and to optimize its timberland operations and profitability. VESTRA Resources developed the ecosystem planning express model, Ep(x), which seamlessly integrates geographic information systems with a database resource capability model and a policy-alternative model, providing the inputs to a linear program. The Ep(x) model uses an underlying adaptive management approach that also maximizes the knowledge base of the ecosystem through detailed sensitivity analyses. The model increased present net worth by over $398 million and generated a more optimal mix of wildlife habitat acres, including spotted-owl-nesting habitat. <s> BIB006 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> In this paper a two-level model and optimization algorithms areintroduced to assist forestry companies in simultaneously considering strategicinvestment and tactical planning decisions. A procedure to reduce thediscrepancy produced in the aggregation and disaggregation process used to linkthese two-level decisions is also presented. This procedure is based onboth cluster analysis over economic parameters defined on “the standmacro-units to be harvested” and on the information transmittedbottom-up and top-down between the strategic and tactical models. Wealso show a new approach for solving the tactical mixed integer model. <s> BIB007 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> Forest management and planning can involve large tracts of land involving numerous areal units. One approach to plan activities for a forested region over decades involves breaking down decision making into three components: strategic, tactical, and operational. Each level of the management hierarchy can involve the development and application of optimization models. These models typically aid in exploring management alternatives as well as multi-objective tradeoffs. Even though a strategic model can provide support for long term management at a broad scale, solutions may not be feasible at an operational level. Tactical level modeling helps to bridge solutions reached at a strategic level using operational planning information. This paper presents several tactical level planning models that have been developed as a part of a research effort supported by the US Forest Service. These models have been utilized in land use management and planning by the US Forest Service through a specially developed spatial decision support system. Copyright Kluwer Academic Publishers 2000 <s> BIB008 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> An important function of tactical planning in forest management is to choose spatially and temporally explicit schedules for both harvesting and road construction activities. In addition to maintaining consistency with goals of the strategic planning process, harvesting decisions are subjected to spatial, environmental constraints. At the same time, planning and cost of road access over the medium-term planning horizon must be considered. This article presents a model and heuristic solution methodology to address stand level harvest scheduling and the associated road construction scheduling problem. The model is formulated to determine minimal cost schedules, for stand harvests and road construction, that achieve recommended timber harvest volume targets and that comply with environmental regulations. The harvest decisions are made at the stand level of resolution. Graph structures are used to formulate the spatial restrictions on clearcut opening size and location. Road construction projects are scheduled to create a feasible road network at minimum net present capital cost. The optimization problem is solved using a Tabu search heuristic, which includes special constructs to cope with the complexity of this problem. An efficient frontier of solutions is produced, which may be utilized to analyze tradeoffs between lost forest productivity, due to timing of harvests, and the capital cost of road construction. Forest Science 46(2):188-203. <s> BIB009 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> In this article we present a new model for the scheduling of forest harvesting with spatial and temporal constraints. Our approach is unique in that we incorporate access road network development into the harvest scheduling selection process. Due to the difficulty of solving the problem optimally, we develop a heuristic that consists of a solution construction stage and two solution improvement stages. We call our approach INROADS and compare it to three other approaches by employing hypothetical example problems with 225 stands (or cut blocks) over a three-period planning horizon. Thirteen example forests that vary in terms of stand value and spatial dispersion are used to evaluate our heuristic, which outperforms the other approaches tested. For. Sci: 46(2):204-218. <s> BIB010 </s> Operations Research Models and the Management of Agricultural and Forestry Resources: A Review and Comparison <s> Decision-Making Levels <s> Multi-criteria decision-making (MCDM) methodology is used to analyse shifts in the utility function of farmers due to policy changes. The presented approach is tested for a sample farm in the loamy region in Belgium. The utility functions under the situation before and after the CAP-reform are estimated and compared. This reveals that the change from price support to direct income support has decreased the relative importance of the risk objective, while the environmental objective, almost non-existent in the situation before 1992, is gaining importance. The example shows that the multi-objective methodology can be a useful framework for a better understanding of farmers' reactions on policy reforms. <s> BIB011
Decisions in forestry are often divided into strategic or long range, tactical or medium range, and operational or short range. Strategic decisions deal with long-range plans to obtain sustainable yields at the aggregate level, both in terms of land specification and timber products. Thus, analysts aggregate forest areas that are similar in site quality, tree species, and age, and they usually consider the total volume of timber. LP models have been the basic planning tools for native forests, which have multiple species coexisting in any area, standard tree rotations of 60 to 80 years, and planning horizons of several rotations. For example, the US Forest Service explicitly introduced multiple uses and concerns, such as recreation, concern for indigenous populations and historical sites, and such environmental considerations as sustainability, wildlife, scenic beauty, and soil and water quality, through its LP models FORPLAN  ) and SPEC-TRUM BIB005 . Plantation owners have relied on LP models for about two decades in many countries, including, Brazil, Canada, Chile, Sweden, and the United States. The models vary, considering basic forest management in New Zealand BIB002 ), environmental concerns in the United States BIB006 , and vertical integration with pulp plants and sawmills, with 0-1 variables to account for plant investments BIB007 . Tactical medium-range models concern horizons that run only to the next harvest BIB008 . They are more detailed than strategic models in terms of spatial resolution, specifying actions for each area, roads for access, and other spatial details due to environmental issues. Their recommendations on harvesting and other actions are usually aggregated. Models give timber production as total volume or as a few classes based on eventual use, such as sawmill lumber or pulp for paper.  developed mixed-integer LP models, integrating harvesting decisions with road building. These are mixed-integer problems of network design, often difficult to solve. Analysts have used commercial packages (accepting suboptimal solutions for the more difficult problems) and heuristics mixed with LP solutions BIB003 . By adding logical inequalities, lifting, and Lagrangean relaxation, they have improved problem-solving processes  . BIB009 and BIB010 proposed heuristic algorithms based on local search approaches. The use of OR tools has increased for operational decisions on harvesting and transportation: (1) Short-term harvesting requires decisions about which areas to harvest each week and how to cut up stems into logs of defined quality, length, and diameter to meet demand at various destinations. Analysts use LP models to match the supply of standing timber with demand for specific products in such countries as Brazil, Chile, New Zealand, Sweden, and the United States BIB005   . In some cases, the problem of how best to cut up stems is solved at the plant, which has more equipment and information available to make better use of each tree than lumberjacks in the woods. Plant managers base such decisions on the characteristics of each stem (length, shape, diameter, and quality) and the products demanded and their market prices, and use dynamic programming  , Tabu search  , and other heuristics BIB001 ). To integrate decisions about areas to harvest and products to produce, analysts have used LP with column generation, reducing wasted timber  . (2) Locating harvesting machinery to carry felled trees to roads is another problem. Workers use skidders or tractors on flat terrain and towers or cable logging machinery to bring stems in steep areas up to a loading area. The company must build access roads to the loading areas and roads on flat terrains so the slow-moving tractors do not have to travel long distances. The traditional manual approach to solving this problem using topographic graphs has often been replaced by computational tools, which interact with geographic information systems (GISs) that collect and manage detailed terrain and forest inventory data. The USDA Forest Service's PLANS BIB011 and New Zealand's PLANZ  are simulation tools that define the access roads and timber operations needed for the machine locations the user specifies using a visual interactive approach based on the GIS. Another system, PLANEX , used by Chilean forest firms uses a heuristic algorithm that interacts with the GIS to determine the best locations for the machines, saving costs and the environment by reducing the number of roads needed. (3) Transportation is usually an important cost in global logistics. Typically logs are carried by truck from forest locations to such destinations as pulp plants, sawmills, and ports for overseas transport. Trucks scheduled manually typically queue at loading and unloading points and overall have higher costs than those scheduled by computerized systems. ASI-CAM , used by forestry firms in Argentina, Brazil Chile, South Africa, Uruguay, and Venezuela, supports daily scheduling decisions for all trips. The system is based on a deterministic simulation model with heuristic decision rules to assign trips. The system reduced the number of trucks needed and overall costs by 10 to 25 percent.  developed a system based on heuristic LP column generation to support truck routing in Sweden, where many trucks visit several loading areas before delivering the accumulated logs at a destination. As communication technology prices fall and the devices become more accessible, transportation scheduling will increasingly involve real-time decisions. One such system, based on a heuristic column-generation LP model  , was used in New Zealand for a time. A remaining problem is the interaction of decisions at different hierarchical levels for horizons ranging from a day to many decades and areas ranging from a few hectares to hundreds of thousands of hectares. Analysts have developed and implemented models to deal with different levels separately and linked them mostly in ad hoc ways. The remaining problems include ensuring consistency between levels of decisions, which means aggregating and disaggregating information and decision variables between decision levels, which is difficult with 0-1 variables, as is the case, for example, when building roads or investing in plants BIB004 . Another problem is considering multiple forest owners within global governmental policies BIB005 ).