Pre-commercial thinning is a silvicultural treatment or type of cut in which young crop trees are selected and released by removing any less promising neighbouring trees hindering their growth. The trees that are kept are usually free of deformities, harmful insects and disease. The end result is a much healthier and better quality forest with a much faster diameter growth rate.

Where is pre-commercial thinning carried out?

Pre-commercial thinning is best suited to young, very dense stands where more space is required between the trees. It is performed only in forests that are around 15 years old, where all the trees are more or less the same age. Such forests are known as “even-aged forests”. They can be composed of softwoods, hardwoods or a mixture of the two.

Pre-commercial thinning releases the healthier trees and allows them to grow more quickly

This type of cut cannot be used to harvest timber because the trees that are removed are too small to be of use to the mills – hence the “pre-commercial” descriptor.

The trees that are cut should always be left on site, since their decomposition enriches the soil.

The features of pre-commercial thinning

Although species diversity usually remains more or less unchanged, pre-commercial thinning can be used to shape the final composition of a forest intended for wildlife, recreational or other uses.

The treatment produces an environment that is well suited to certain animal species, including the white-tailed deer, which feeds on the branches in newly cut areas and finds shelter in the thinned forest. The same applies to the hare and partridge, which hide in the cutting waste. For other wildlife species, however, it is important to ensure that certain types of trees – fruit trees, for example – are left standing.