To meet the goal of economically valuable timber volume flow over time, silviculture programs apply silviculture treatments such as pre-commercial thinning (PCT) to concentrate growth on higher-value tree species and shorten the time to reach harvestable age. A study was established to examine growth and yield of a range of PCT treatments in a mixed western hemlock (Tsuga heterophylla (Raf.) Sarg.) and amabilis fir (Abies amabilis Dougl. ex Forbes) stand that had regenerated naturally, and at 18 years was characteristically clumpy with density ranging from 0 to 80 000 stems per hectare (sph). Using the results from the 15-year post-treatment measurement, future growth and yield of each PCT treatment was projected, and a financial analysis was conducted to compare the costs and benefits of PCT or no treatment. As expected, the results of the financial analysis showed that the site values increased for all the PCT treatments and the control under the scenarios with lower discount rate, lower harvesting costs, and higher log prices. Minimum harvest criteria that reduced harvest age reduced merchantable volumes and site value. In general, of the PCT treatments, the denser 1200 sph treatment provided the best merchantable volume and site value. This information can assist in decision-making regarding best treatments needed to achieve stand-level objectives. Continued monitoring of this experiment over time will provide better information about the longer-term effects on growth, yield, and economic returns of PCT in these mixed western hemlock and amabilis fir stands.
de Montigny, L., Asante, P.; Noble, S. Le; Nigh, G.. 2019. The Economic Implications of Pre-commercial Thinning Treatments in Mixed Western Hemlock and Amabilis Fir Stands in Coastal British Columbia under Varying Cost and Benefit Assumptions and Minimum Harvest Criteria (EP1211). Ministry of Forests, Lands, Natural Resource Operations and Rural Development. Technical Report (FLNRORD). TR124