Optimizing continuous cover and rotation forestry in mixed-species boreal forests

Abstract

We study the management of mixed-species boreal forests and tree species composition in a stand-level economic–ecological, size-structured model. The model includes ecological tree species interaction, a detailed harvesting cost module, optimal harvest timing, and optimization between continuous cover and rotation forestry. Optimization is solved by applying a trilevel structure in which the optimal rotation is the highest-level problem, harvest timing is the mid-level problem, and thinning intensity is the lowest-level problem. Given realistic regeneration costs and a 3% interest rate, continuous cover forestry is optimal and may include up to a 40% fraction of broadleaves. A low interest rate and low regeneration cost together with the presence of light-demanding Scots pine (Pinus sylvestris L.) favours rotation forestry. Eurasian aspen (Populus tremula L.) decreases the bare-land value but is optimal to fell without utilization only when it has no commercial value. Overyielding in terms of cubic metre output does not reveal the economically preferable species combination. Managing single-species stands by removing other species that are naturally regenerated decreases the economic outcome by 35%–44%. Felling noncommercial trees without utilization shows that the economically optimal solution avoids high-grading. Maintaining the number of large-diameter trees beyond the level that maximizes profitability implies only minor losses. Omitting thinning decreases the bare-land value up to 73%.