Pseudotsuga Menziesii Var. glauca - Ecology

Ecology

Rocky Mountain Douglas-fir grows on a variety of sites across its wide geographic range. It grows at lower elevations adjacent to and within bunchgrass communities and is also found in upper-elevation subalpine forests. It tends to be most abundant in low- and middle-elevation forests, where it grows over a wide range of aspects, slopes, landforms, and soils.

In spring and winter (in British Columbia, Idaho, and Montana) elk browse on south- and southwest-facing Rocky Mountain Douglas-fir and Ponderosa pine stands, particularly when shrubs and/or grasses are productive. In summer, elk generally are found at higher elevations (outside the Rocky Mountain Douglas-fir and Pacific Ponderosa Pine zones). During fall elk use stands of Rocky Mountain lodgepole pine, subalpine fir, western larch, or grand fir with high canopy cover.

In parts of Yellowstone National Park, elk browsing is so intensive that young Rocky Mountain Douglas-fir are stunted at 1–1.5 m (3–4.5 feet) in height, with live branches trailing very close to the ground, and branches on the upper two thirds of the tree dead. Low-elevation and south-facing open-structure Rocky Mountain Douglas-fir types are often important winter range for white-tailed deer and mule deer. Moose winter in low-elevation Rocky Mountain Douglas-fir types in areas where willow thickets, the preferred winter habitat, are lacking; in such areas Rocky Mountain Douglas-fir is an important moose food.

Chipmunks, mice, voles, and shrews eat large quantities of conifer seeds from the forest floor, and clipped cones are a staple and major part of storage of red squirrels. These animals store a large amount of Rocky Mountain Douglas-fir cones or seeds. American marten commonly den in hollow logs.

Numerous species of songbirds extract seeds from Douglas-fir cones or forage for seeds on the ground. The most common are the Clark's nutcracker, black-capped chickadee, mountain chickadee, boreal chickadee, red-breasted nuthatch, pygmy nuthatch, red crossbill, white-winged crossbill, dark-eyed junco, and pine siskin. Migrating flocks of dark-eyed juncos may consume vast quantities of seeds and freshly germinated seedlings. Woodpeckers commonly feed in the bark of Rocky Mountain Douglas-fir. Blue grouse forage on needles and buds in winter; they and other birds rely heavily on Rocky Mountain Douglas-fir communities for cover.

The Douglas-fir is vulnerable to infestation by a woolly aphid, Adelges cooleyi that also infects the Engelmann spruce to complete its lifecycle.