Assessing Alternative Silvicultural Prescriptions for Mid-Rotation, Unthinned, Spruce-Fir Stands in Maine

Determining the optimal timing and type of entry in mid-rotation, unthinned stands can be complicated by a variety of economic and biological factors. In this analysis, long-term data from the Commercial Thinning Research Network was used to project spruce-fir (Picea spp.-Abies balsamea (L.) Mill.) stand growth on six different sites across Maine following six alternative thinning treatments (33% and 50% relative density removal paired with low, crown, and dominant thinning methods). Results showed that the low-thinning treatment performed best in terms of maximum net present value, stand age at time of maximum net present value, and average merchantable stem size. Although the low-thinning resulted in a 10% mean reduction in maximum net present value when compared to the control, the average merchantable stem size more than doubled. Overall, results of this analysis indicate that it may be financially responsible to commercially thin these stands using a low-thinning method and a light removal intensity, as the average merchantable stems size was increased and a mid-rotation financial return provided.