|GUIDELINES for||. . .|
|Developing Stand Density Management Regimes|
Forest estate models are useful for projecting the impacts of stand management activities on the forest inventory over time. They have evolved over the past 30 years in parallel with the evolution of computing technology. Modelling forest estates involves manipulating large amounts of data. The sophistication of the model reflects the detail that can be incorporated into the data set.
Two types of forest estate model are available: simulations models and mathematical programming models. Both are used to determine the impact of stand density management activities on the stock and flow of harvestable timber, and on the achievement of other non-timber objectives. The issues of data quality and reasonable assumptions are important considerations.
Simulation-based forest estate models operate on the principle of achieving pre-determined levels of outputs for flows and stocks of timber and non-timber resources. They can also incorporate risk in defining the success of outcomes of various activities being modelled. Unlike mathematical programming models, simulation models do not rely on a specific algorithm. Rather, they incorporate a wide variety of mathematical relationships, providing considerable flexibility of application.
Mathematical programming models have their roots in the fields of engineering, operations research, medical research and defence. They are widely used to solve transportation network problems, warehouse and inventory control problems, product distribution and sales problems, and in a variety of military applications. Their use in forestry is a relatively small segment of their application throughout the world.
Linear programming is a method used to allocate limited resources to competing activities in an optimal manner. Although there are important assumptions regarding their use, linear programming offers considerable flexibility in applications such as forest management problems, harvest scheduling, silviculture planning and economic analysis.
Economic analysis tools are simply computerized equations or calculation templates that incorporate economic principles for solving specific questions related to the worth of a silvicultural endeavour. Several of the models incorporate some of their capabilities to provide stand- or forest-level economic analysis.
For example, TIPSY allows the user to calculate the present value or site value of a juvenile spacing treatment. WOODSTOCK, a forest estate model, has the capability to account for production costs and the economic operability of any management activity. Most of the decision support models listed in Tables 2 and 3 can produce input to an economic analysis.
Copyright 1999 Province of British Columbia