Constant unit prices for sawlogs and pulpwood are commonly used in the valuation of a forest stand. We analyzed the optimal management strategy at the stand level in even-aged pine stands in the case where stems are valued based on the prices and predicted quantities of the end products of the sawing process at the stand level (QualityPremiumCase). The QPC was then compared to the base case (BC) in which quality indifferent unit prices are used.
We used a simulation-optimization system OptiFor in which a process-based growth model PipeQual provides growth predictions that include input variables for models that predict the lumber grades and by-products percentages of the total volume of stems. Growth model predictions, harvesting cost function, and models for predicting the yield of various sawn wood grades and by-products of the sawing process, in addition to exogenous unit prices and processing costs were used for calculation of the bare land value as a function of the decision variables. Numerical optimization, by Osyczka’s direct and random search algorithm was used to determine the management regime that maximized the bare land value for both cases.
Fewer thinnings in the QPC were optimal compared to the BC. Thinnings were heavier, and time intervals between thinnings were longer in the QPC than in the BC. The yield of sawn wood was significantly higher and the quality distribution of sawn wood better in the QPC. It was also found that optimal management regimes obtained by constant unit prices may lead to raw material supply, which is not profitable for sawmills to process.