Optimizing the debarking and cutting schedule of cork oak stands

Abstract

Key message: Optimal management of cork oak forest stands was analyzed for different site indices and cork growth rates. Optimal debarking intervals varied during the rotation and were sometimes shorter or longer than the officially recommended range of 9–14 years. Context: Quercus suber L. is one of the most important multipurpose tree species in the Mediterranean area. Its main product is cork, appreciated for its elasticity, impermeability, and thermal insulation properties. Cork oaks are debarked at constant intervals, which vary from 9 to 14 years depending on the area. However, since the growth rate of cork is not constant during the rotation, it may be optimal to use variable debarking intervals. Aims: This study optimized the debarking and cutting schedules of Quercus suber stands and analyzed the influence of economic and stand-related factors on optimal management. Methods: The study employed a simulation system where the existing growth and yield models for Quercus suber were used with a non-linear derivative-free optimization algorithm. Discount rates and cork prices were tested as economic factors and cork growth rate and site productivity as stand-related factors. Results: The optimal debarking interval varied during the rotation. Increasing cork growth rate increased the optimal number of debarkings and shortened their interval. Decreasing discount rate increased the optimal number of debarkings during rotation while decreasing cork price decreased the number of debarkings. Conclusion: The profitability of the management of cork oak stands depends on site fertility and stand density; management is not profitable on poor sites or at high discount rates. This study is the first that simultaneously optimizes the cutting and debarking schedule of cork oak stands, allowing the debarking interval to vary.