Douglas Fir at Deer Island, Columbia County, Oregon

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Deer Island Fir

Douglas Fir trees are a fire cycle tree species unique to the Pacific Northwest. Botany type folks will tell you that it really isn't a true fir but we call it that anyway. It is found natively from the coast to the Cascade Mountain summit and generally from the Canadian Border to the Northern California Border. It has been successfully grown in New Zealand and Switzerland. It thrives in temperate climates with rainfall exceeding 30 inches per year. In favorable sites it will produce 1000 board feet per acre per year in annual growth over a wide range of tree densities. Despite liking lots of rain, it will not survive in 'wetlands' or places where there is standing water as it feet will drown.

The bark is pitchy, and Douglas Fir forest burn violently when they do get on fire. The tree is not shade tolerant and will die out if it is not the dominant species. It regenerates best after a fire or other activity that has cleared away the ground to bare dirt, as even grass and low shrubs will shade out young trees. The cones contain seeds with wings on them and the cones open on a fall freeze and the seeds blow in the wind. It is believed that the seed will travel several miles under favorable conditions which would be bear ground (as in after a fire) or logging operation, followed by a snow, and a freeze and a strong wind.

In most of the fir region, the Douglas Fir is not the Climax species, but is the first softwood to return after a fire. Western Hemlock which is shade tolerant start well in duff on a forest floor and it will ultimately grow up through the Douglas fir and supplant it. Historically it is believed that forest fires consumed Douglas Fir Forests about ever 200 years. In isolated instances however, trees lasted for much longer than than and the example shown in the photo above is one of those instances. Trees up 4 feet in diameter were common in the virgin timber, however whoppers were found including this 22 foot monster shown above.

Some people, it seems oppose timber harvesting, on the false premise that the Douglas Fir is not a renewable resource, but in fact the Douglas fir regenerates rapidly, and most successfully after the most aggressive harvesting methods ( harvest of all merchantable timber followed by a fire to burn the rest). Douglas fir forests begin to be harvestable after about 30-40 years, and attain a stage of maturity in 60 to 80 years after which their robust growth rate begins to decline, and various tree diseases begin to take their toll. A classic defect in older Douglas Fir forests is 'conk rot'. It begins as water penetrates the protective bark of the tree via a dead limb hole or injury. This is followed by a fungus which will appear on the outside of the tree as perhaps a small white growth, but will help rot the inside of the tree which will ultimately lead to a hollow spot in the tree. These hollow spots are popular homes for certain forest species collectively known as 'cavity dwellers', but a forest radically infected with conk rot is greatly devalued or worthless for lumber. Conk rot is very difficult to detect in standing timber, and many a logging company who has made a practice of buying timber on the stump has taking a beating upon encountering a stand with extensive conk rot.

This photo has floated around for a long time. Whether it was really taken at Deer Island or somewhere else has been questioned. This writer cannot verify where it was taken.

- - Updated 12/11/2012
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