Comparing Stand Growth Models in Optimizing Mixed-Species Forest Management

We study the effect of forest stand growth models on the economically optimal management of boreal mixed-species forests. Our size-structured economic-ecological model includes the optimization of harvest timing, harvesting intensities, rotation periods, and the choice between rotation forestry and continuous cover forestry. We carry out a systemic comparison of economically optimal solutions obtained with three statistical-empirical stand growth models for both single- and mixed-species stands with up to four tree species. Given a 1% interest rate, the optimal choice between continuous cover and rotation forestry depends on the applied growth model. However, under a 3% interest rate, the optimal management regime is always continuous cover forestry. The optimal solution details are highly dependent on the growth models. With a 1% interest rate, it may become optimal to apply intensive close-to-clearcut harvesting that results in a dominant species change via natural regeneration. However, the level of natural regeneration varies strongly between the growth models. The economic superiority of a species mixture cannot be determined from overyielding differences. Mixed-species stands have higher maximum sustainable yields, bare land values, and average net revenues compared with monocultures.