Cover photo courtesy Shallan Knowles
By Adam Gebauer
Perhaps no other tree represents the Pacific Northwest more than the Douglas Fir, Pseudotsuga menziesii, not to throw any shade to our beloved Ponderosa pine (more on that later). Doug fir, also known as red fir, is the dominant tree in many low- to mid-elevation forests. It is the most economically important tree across the Pacific Northwest and yields more timber than any other tree. It is used for dimensional lumber, plywood, and veneers, as well as in Christmas tree plantations. It is also the most replanted tree in industrial timber lands across the region. It can grow in the moist, coastal mountains to dry, east-side forests and can tolerate shade to full sun.
When I first started wandering around the towering trees of the PNW forests, I remember learning a few key things about these trees. One, its name is confusing; it is not a true fir; and its scientific name, Pseudotsuga, means false hemlock. Its common name, Douglas fir, comes from the naturalist David Douglas, who brought the tree from Europe fostering Doug fir plantations. It also has distinguishing cones that appear like a mouse has crawled between the scales with only its tail and feet sticking out. There are tribal stories of a mouse fleeing a fire and finding refuge in the cones.
There are two varieties of Doug fir. The coastal Douglas fir ranges from costal British Columbia as far south as Yosemite and grows faster and bigger than the Rocky Mountain variety. The latter variety spans all the way to the Mexico border, becoming less frequent with lower latitudes. Because of its timber value, it has spread to many corners of the world, including New Zealand, Chile, Argentina and Europe.
In parts of its range Doug firs are suffering from the effects of climate change, as increased drought has led to outbreaks of beetle die off. In parts of southwestern Oregon, for example, there has been a massive increase in Doug fir die off with an estimated 260,000 trees killed on nearly 150,000 acres from 2016 to 2019. This was more trees in a four-year period than in the previous four decades.
Although larger, older Doug fir are relatively tolerant to low and moderate fires due to their developed deep-furrowed bark, it can take up to 100 years to develop these characteristics. Doug fir is fairly shade tolerant, meaning it can grow under shade, and in general shade tolerant species are less fire tolerant. Ponderosa pine and western larch are shade intolerant and many land managers in eastern Washington are shifting tree stands to these more drought- and fire-tolerant species.
Ponderosa pine and larch have several other adaptations that make them particularly tolerant to fire. Where deep soils allow —unlike on Spokane’s South Hill—they grow deep tap roots. They have thick buds that can withstand heat. These trees are self-pruning, dropping branches that don’t receive a lot of sunlight, which helps them reduce ladder fuels—protecting the crowns from catching fire. Both species also have airy canopies that can disperse heat rather than trapping it like the dense canopy of Doug fir.
Douglas firs will still be a large part of the forests of the Pacific Northwest, but climate change will alter where some of our tree species will thrive and where others will suffer from drought, insects, and disease outbreaks. On the coast, these mighty trees still can grow to over 300 feet and throughout their range grow deep, furrowed red bark that will impress those traversing amongst their trunks.
Recently Adam Gebauer has been working with some regional folks on prescribed fire training. He is thinking hard about doing squats before ski season.
