Link to Home page
Link to Forestry Information
Link to Watershed Information
Link to Mill Information
Link to Consumer Information
Link to Extras Page
Link to More Information

:: Home > Watersheds > Old and Second Growth > Part 1 of 2

An old growth forest.

What are they?

When talking about forests in Oregon, a couple of terms describing forest structure often come up: old growth and second growth. While the terms sound like they refer to the ages of trees within a forest, in fact they don't. The term "old growth" refers to a forest with structural characteristics associated with "old forests"— forests largely undisturbed since Euro-American settlement (roughly since 1850). The trees in the forest all don't need to have been around since 1850, but some are! Second growth refers to the second-generation forest that grows after an old-growth forest is catastrophically disturbed.

Perhaps the following discussion while make it more clear.

When we talk about old growth, we are referring to a forest and not just a single tree. The tree in an old-growth stand may be old, or it may be young. What makes old-growth forest are simply some characteristics we expect to see— in western Oregon we may see them when the forest approaches 120-200 years in age.

An old growth, or "ancient" forest of the Pacific Northwest has large conifer trees that may reach several hundred years in age, but there will also be clumps of young trees that have grown where sun has penetrated the forest canopy. The"canopy" is the part of a tree that contains the branches and leaves, and in a forest it refers to the collection of tree canopies that cover the forest floor like an umbrella.

The canopy of an old growth forest, with the branches and leaves of old trees, and large, standing, dead trees, called snags.The result of the young and old trees, sick and healthy trees growing together, is that the canopy is very complex, with many layers. There are large, standing dead trees, called snags, that poke out of the forest and provide homes for insects, rodents, and birds, and serve as perches for birds-of-prey like owls and eagles.

Large dead trees crisscross the forest floor, and may lie there decaying for hundreds of years. This downed wood provides shelter and food for many more plants, animals, and fungi, and as it decays it acts like a slow-release vitamin for the soils of the forest. Large trees fall into forest streams, decaying and providing food for insects, like the caddis and stone flies, and algae, both of which are foods for fish. The wood in the streams also creates pools where fish can hide and rest.

Second Growth Forests