Prior to immigrants following the Oregon Trail into the Oregon Territory, the western valleys of this region were cloaked with oak woodlands. Interspersed with the woodlands were savanna and prairie habitats that the Native Americans cleared with periodic fires. These habitats dominated the lower elevation hills and valleys and were important resources for the Native Americans but also for a host of wildlife and plant life associated with the woodlands.
As settlers and pioneers streamed into these new lands, their need to clear acreage for crops and need for fuel and building material decimated the oak groves. As land was cleared, the range of these oaks started to shrink. The preference for faster growing Douglas fir trees for lumber also played a role in the removal of the oak trees.
Oregon white oak (Quercus garryana) is native to British Columbia, Washington, and Oregon. It grows mainly west of the Cascade Mountains in well-drained soils from sea level to about 4,000’ in elevation. However, in the southern portion of its range, these oaks may occur at elevations up to 7,500 feet. Oak trees may also be found west of the Cascades along the Columbia River Gorge. The oak is found in two main habitat types: oak woodlands and oak savannas. Many areas in this western region have seen significant declines of these habitats, some up to 95%. Most of the original oak woodlands and savannas exists in private ownership.
Massive, stately trees grow from 50-90 feet tall with over-arching limbs. With 20-40” diameters, these trees are better known for their charismatic limbs and growth versus immense size. Found in areas with hot, dry summers and wet winters, these oaks handle snow and ice well. In areas with poor soil conditions, Oregon white oak and Pacific madrone may be the only two tree species growing in those conditions. The white oak does not tolerate shade well and will often die out if overtopped by the faster growing Douglas fir or big leaf maple.
The oak’s large acorns are an important food source for many species of wildlife including acorn woodpeckers and wild turkeys and smaller animals like Western gray squirrels. Over 200 species of wildlife are associated with the trees due to the acorns, nesting habitat in the limbs or from gleaning insects that are attracted to the deciduous leaves and buds. Many insects inhabit the duff layer and rotting leaves beneath the trees.
Numerous butterfly species including the Fender’s blue and hoary elfin also inhabit this oak savanna and are dependent upon host plants such as Kincaid’s lupine that have also declined because of land conversion.
In addition to wildlife and insects, a variety of shrubs such as oceanspray, mock orange, Oregon grape, and red-flowering currant are also associated with white oak habitats. Open grasslands or prairies interspersed amongst the oak woodlands have different species of wildflowers associated with these habitats, most notable of this list is camas.
Native Americans harvested camas bulbs and roasted them in huge pits for later consumption. Periodic burning of the prairies reduced competition between camas bulbs and other plants and was a method employed to maintain the health of these camas’ fields. These fires were either set by the local inhabitants or ignited through lightning storms. Today, prescribed fires are a management tool to reduce invasive plants and restore the health of these once common savannas as the historical fire regime has been altered.
Along with the Oregon white oak, there are two other common species of oaks that occur in this region: California black oak and canyon live oak.
Though the transition of the oak savannas to development of homes or cropland has taken place for many years, fortunately, there are organizations that have risen to the rescue of this historic habitat.
Conservation partners include federal, state and local government agencies, universities, non-profit conservation groups, and private landowners. Management practices include planting oak seedlings and plants, reducing pesticide and herbicide use, incorporating prescribed fires were needed, managing for diseases, and utilizing mowing or grazing where fires are not practical.
Landowners may qualify for assistance or technical expertise from agencies such as US Fish and Wildlife Service, Oregon Department of Fish and Wildlife, tribal members, Washington Department of Fish and Wildlife, the US Natural Resource Conservation Service, and Canada’s Ministry of Resources and Forestry. Local Soil and Water Conservation Districts also provide assistance to landowners in various forms and should be contacted by any private landowner willing to undertake conservation of this magnificent species on their land. On the east side of the Cascades Mountains, the East Cascades Oaks Partnership keeps track of oak woodlands as they grade into ponderosa pine forests or sagebrush steppe habitats.
Though distribution of the Oregon white oak is but a fraction of its historical range, partners are hard at work conserving this special tree that defines much of the Pacific Northwest.