Douglas Fir

Pseudotsuga menziesii

Douglas Fir
Douglas Fir starting to grow
All photos with blue borders expand if clicked
a few weeks later
A couple weeks later
Douglas Fir
Sixty year old timber
Douglas Fir Bark on 40 year old tree
Douglas Fir Bark on 40 year old tree

The Douglas Fir is the dominant conifer in Oregon and Washington west of the Cascades. It is found in portions of British Columbia, and has been taken around the world for use in forest plantations. It is a fire cycle tree that regenerates quickly on the scorched earth residual of a forest fire. It also has a pitchy bark and burns profusely in a forest fire. It is shade intolerant and dies out quickly if shaded. As a wood product it is much in demand.

The bark which is very thin on young trees and has sap blisters on it, thickens with age. It grows from the inside so as the tree gets larger the bark tends to get cracks in the outer layers of of as the older layers are not shed but rather accumulate to provide the tree with some additional protection. A tree several hundred years old may have bark several inches thick. when dried, bark can be used for a slow and long lasting fire.

A Douglas Fir can add anywhere from a few inches to as much as 60 inches in height in a single year. Younger trees usually grow the most robustly at the attempt to get above the competition quickly. If the tree is in the open it will usually grow in height more slowly and put more energy into growing limbs, implying that widely spaced trees are shorter and have heavier limbs. This makes for lower quality lumber, but provides an adaptation to the conditions in that the shorter trees are less likely to blow over. Where the trees are thick, they effectively support one another, and the winds can't get at them implying that they can be taller and thinner, which is exactly what happens.

Economic importance

Douglas Fir Logs
Douglas Fir logs have been the economic engine of the Pacific Northwest for 150 years. The logs here are moving by truck down a road originally construction 85 years ago as a logging railroad to log a previous generation of Douglas Fir.
Butt view
Butt view
This tree was likely scarred during thinning, but note the change in the growth rate after the thinning

The Douglas Fir has been the mainstay of the timber industry throughout its primary growing area for a 150 years. Loggers began harvesting the Douglas Fir to make lumber to support the California Gold Rush and it continues to this day to be one of the most important crops in the region. The tree grows over a wide area ranging from southern British Columbia to approximately the Northern California border and west of the Cascades. While it most famously makes lumber for houses, thousands of miles of railroad tracks have Douglas Fir ties, and Douglas fir is frequently used for poles and piling as well. Little is wasted and the scraps from lumber manufacture are chipped and used to make paper and the portions unsuitable for that and up as wood pellets for pellet stoves, mulch, and hog fuel for co generation plants.

Timber Management

The world is full of self proclaimed timber managers, most of whom can' even identify the various specie of trees. One ongoing issue has to do with the benefits of thinning a Douglas Fir stand. the pictures in the margins show some of the issues. What you see is a tree that was 'released' by thinning approximately 25 years before this picture was taken. The tree was injured in the process and you can see the results of that. The tree has developed a rotten spot in the butt which will degrade the the quality of the tree for lumber. Likely at this age the rotten spot extends only a few feet up the log so it could be easily trimmed out. Of course, it goes without saying that the longer the tree is left before harvest the worse the rotten spot would become.

The other message in the photo though, is to simply see how the growth rate of the tree changed when it was 'released' by thinning. The concentric rings you can see are the annual growth amount. The tree was about 25 years old when the thinning occurred, and had almost stopped growing. This particular tree was along a skid trail where the harvesting was done and was a "burn tree" which means that it was deliberately left along the skid road to be the designated tree to be damaged so as to save those behind it. The difference in growth rate even though this tree had many of the trees around it dragged against it damaging it somewhat tells the story.

Additional information: see Wikpedia - Douglas Fir

- - Updated 09/05/2016
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