Tree Thinning

As you can see, the only remaining live branches are clustered high in the top 15% of the trunk. Thinning would reduce competition.

As you can see, the only remaining live branches are clustered high in the top 15% of the trunk. Thinning would reduce competition.

The term “thinning” or “selective harvest” describes the practice of removing some, but not all, of the trees in a forested area. The idea behind most thinning projects is to reduce competition and increase growing space for the remaining trees. Growing larger trees more quickly can enhance habitat for wildlife that nest and feed in bigger trees. Also, trees that are growing vigorously are often healthier, and more resistant to disease, insect pests, and even wildfire damage.

So, when should you consider thinning? As trees grow larger, look up to the canopy areas and see if some of the tree crowns are smaller than others.  That’s a sign of competition. Also, if the area under your trees is heavily shaded from the crowns and there aren’t many shrubs, ferns, or wildflowers growing in the understory, it might be a good time to remove some trees to allow more light on the forest floor.

Tree thinning pic2

There is very little ground vegetation in this densely forested area. A thinning project would allow more light to the forest floor where wildflowers and shrubs could grow.

You can also walk through your woodland and measure tree spacing and tree diameters to gather more data to support a decision on thinning. There are a few ways to do this, which are better learned out in the woods. Each year we work with several landowners in the District to complete these measurements as part of their Forest Stewardship Plan.

For more information about tree thinning, click here.  Here’s another great resource on the Care and Planting of Tree Seedlings.

Please contact Forest Conservationist Michael Ahr at 503.238.4775, ext. 109 or, for a site visit to learn more about evaluating your woodland for a potential thinning project.


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