Forest managers studied the effects of different tree densities after partial harvesting in British Columbia. Fir trees grew more with lower tree density, but spruce trees were more productive overall. Smaller trees grew more than larger ones after thinning, and more small trees grew into larger sizes. Lower tree density led to higher growth and volume in the forest. Keeping tree density below 20 m2/ha can lead to better growth. More trees died in areas with higher tree density. In British Columbia, complex forests can be managed well with partial harvesting.