Summary of the 13-Year Results of an Interior Douglas-fir Precommercial Thinning Experiment in the Alex Fraser Research Forest Williams Lake British Columbia

This document details a long-term forestry study in British Columbia designed to evaluate how pre-commercial thinning influences the development of uneven-aged interior Douglas-fir stands. Researchers compared a control group against three distinct thinning strategies, including standard and clumped spacing, to determine which methods best promote individual tree growth and forest health. Over a thirteen-year period, the thinned plots demonstrated superior diameter and basal area increases compared to untreated areas, while also suffering from lower mortality rates. This study highlights that strategic spacing can accelerate the recruitment of large-diameter trees, which are vital for both high-value timber production and maintaining critical winter habitats for mule deer.