DF decline & mortality in Southwestern Oregon

Douglas-fir (Pseudotsuga menziesii) is among the world’s most economically important tree species and is abundant across southwestern Oregon where it is the dominant species in many low to mid-elevation forests. Douglas-fir trees provide vital wildlife habitat, capture and store carbon, and are an important source of timber. However, recent increases in Douglas-fir mortality in SW Oregon have raised concerns about the future viability of the species in this region, the loss of ecosystem services, the costs and difficulties of managing extensive mortality patches, increased wildfire risk, as well as increased risk to homes, properties and infrastructure. The purpose of this website is to share information about Douglas-fir decline in SW Oregon with forest landowners and land managers who are grappling with these issues. As we learn more about DF decline thanks to on-going monitoring efforts and new research, we can expect the findings and recommendations discussed here to evolve.

“SW Oregon” refers to the Oregon portion of the Klamath Mountains Ecoregion and a portion of the Western Cascades ecoregion, shown in the area outlined in black on the image below.

In this website we’re focusing on Douglas-fir decline and mortality in SW Oregon stemming from the interactions of hotter drought and insects, primarily the flatheaded fir borer, which together are responsible for most of the recent increase in Douglas-fir mortality in interior SW Oregon.  Mortality from these causes is mostly found on hot, dry, relatively low to mid elevation sites in the interior Rogue and Umpqua valleys.  Of course, Douglas-fir mortality can also result from a variety of other causes such as root disease, wildfire, and excessive shading in dense stands, but these factors are not addressed here.  While our focus is on SW Oregon, it should be noted that the combination of drought and flatheaded fir borer attack has resulted in Douglas-fir mortality in other part of the state, such as the Willamette Valley, as well as in northern California. 

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