Blue Mountains forests

• Category: Forest Biomes.
• Geographic Location: North America.
• Summary: Rising above the American northwestern deserts, the Blue Mountains create a dramatic landscape composed of tall peaks, deep river valleys, and vast forests.

Situated amid the deserts and grasslands of the Columbia Plateau, the Blue Mountains form a verdant sanctuary in this landscape. This mountain range occurs mostly in the northeastern quadrant of the state of Oregon, with parts in neighboring Idaho and Washington. The range, which forms a portion of the Snake-Columbia River watershed, supports forests that form a natural link between the Cascade Range to the west and the Rockies to the east. These mountains harbor robust wildlife populations—but the forests of the Blues, as these mountains are commonly called, have been dramatically affected by human activity.

As in any mountainous environment, the ecology of the Blue Mountains is shaped by topography. Much of the land between the Cascades and the Rocky Mountains experiences the rain-shadow effect, creating vast deserts that stretch south through this realm from central Washington to the Great Basin of Nevada and Utah. The Blue Mountains, however, are an exception. Tall peaks drive moist air upward, generating rainfall. Because the Blues lie east of the Cascades, they themselves are subject to a slight rain shadow that causes them to be drier than the very moist coastal areas of Oregon. Nevertheless, rainfall at higher elevations promotes the growth of expansive forests surrounded by an expanse of low-elevation sagebrush and dry steppe environments.

Vegetation Zones

Elevation creates a zonation of plant communities moving up and down the mountains. From the base of a mountain, vegetation shifts from sagebrush (Artemisia tridentata) steppe to juniper (Juniperus spp.) woodlands to ponderosa pine (Pinus ponderosa) forests. These ponderosa forests are often described as parklike, for trees usually are sparse, permitting the growth of understory grasses. Fire maintains these forests by burning understory vegetation and leaving mature, fire-resistant ponderosa pines standing. Above these forests, moister conditions allow the growth of Douglas fir-spruce (Pseudotsuga menziesii) forests. Spread across much of the Blues, these forests generally are more productive due to the increase in rainfall and humidity. Moister conditions allow communities of shrubs to flourish, including the huckleberry (Vaccinium parvifolium), thimbleberry (Rubus parviflorus), and bracken-fern (Pteridium aquilinum).

Still further upslope, lodgepole pine (Pinus contorta) becomes the dominant tree species. It can tolerate the short summers and heavy snowfall of the upper montane zone. Stands of lodgepole are often very dense, prohibiting the development of forest-floor plants. Again, this community is controlled by fire: The dense growth of mature trees encourages intense fires that burn large areas. Fires remove the most mature trees, permitting the next generation to replace them. Lodgepole pine grows fast, but the successional communities that soon follow a burn are productive and important for herbivorous animals.

The highest forest type in the Blues is the subalpine forest, which is composed of several tree species adapted for an extreme environment. The density of these forests varies, with stands becoming thinner higher up the mountains. Subalpine fir (Abies lasiocarpa), western white pine (Pinus monticola), Engelmann spruce (Picea engelmannli), and aspen (Populus tremuloides) are common species in this vegetation zone. Snowfall in these areas can be substantial, and the growing season is short. As a result, many trees are short and stunted due to the harsh environmental conditions. Eventually, forests give way to alpine meadows that are covered by snow for much of the year. Following snowmelt, a rich plant community develops during the short growing season. Grasses and wildflowers abound during these months, many of which are found only on isolated high mountain peaks.

Fauna of the Blues

Wide-ranging herds of mule deer (Odocoileus hemionus), bighorn sheep (Ovis canadensis), and elk (Cervus elephas) share prime mammalian habitats with black bear (Ursus americanus) and cougar (Puma concolor). The gray wolf (Canis lupus) vanished from Oregon—and nearly all the contiguous 48 states—by the 1930s but has sparsely reappeared in the Blue Mountains since 2000; this apex predator enjoys a protected/endangered status here, as does the Canada lynx (Lynx canadensis).

Among amphibians and reptiles, the Columbia spotted frog (Rana luteiventris) ranges along the rivers while the western painted turtle (Chrysemys picta bellii) stalks drier zones.

Avian members of the Blues community include such denizens as the greater sage-grouse (Centrocercus urophasianus), western tanager (Piranga ludoviciana), and pileated woodpecker (Dryocopus pileatus); as well as predators such as the great gray owl (Strix nebulosa), ferruginous hawk (Buteo regalis), and bald eagle (Haliaeetus leucocephalus). Listed as a species of concern is the northern spotted owl (Strix occidentalis caurina).

Human Impact

Forests are defining hallmarks of much of the Blue Mountains, but this ecoregion has other notable features. Between the peaks are deep valleys with rich soils that support grasslands, many of which have been converted for agriculture; crops such as wheat and alfalfa are common here. These valleys have been carved by powerful rivers such as the John Day, Grande Ronde, Powder, and Malheur. Perhaps the most impressive of these areas is Hells Canyon, created by the Snake River as it passes between the Wallowa Mountains in Oregon and the Seven Devils Mountains in Idaho. Many wildlife species are dependent on riparian areas here. In the past, nearly all these rivers supported massive salmon runs, although those runs have now dwindled to a fraction of their former levels.

The rugged nature of the Blue Mountains landscape supports a sparse human population. Most live in the valleys, which can support agriculture, but the entire area has been extensively affected by human activity. A large proportion of forests have been logged in the past, leaving few old-growth forests that are essential for many species. (One protected old-growth stand envelops the Emigrant Springs State Heritage Area, a campground and interpretive site that recalls the Oregon Trail pioneering days.)

Livestock grazing on both forested and open lands has degraded many local ecosystems, especially riparian zones. Outbreaks of pine beetles and other pests have created large swaths of dead trees. Invasive species range from Kentucky bluegrass (Poa pratensis) and tansy ragwort (Senecio jacobaea) to European red fox (Vulpes vulpes) and Virginia opossum (Didelphis virginiana).

Land management programs aim to address these issues while balancing human use of natural resources. A related issue is firefighting policies. Studies have called into question, for example, the suppression of fire in terms of the impact on the overgrowth of certain evergreen species and the consequent loss of elk grazing habitat. Research continues both on the use of prescribed fire and overall fire regime decision-making in light of a new understanding of the balance of mature trees, understory growth, and the forage needs of a wide range of animals.

Fire policy becomes even more crucial with the progression of global warming, although the effects of climate change in the Blue Mountains Forests biome are unpredictable. The predicted rise in air temperature will influence soil moisture and impact the distribution of plant species, with drought-tolerant species competing more for limited resources. The Pacific Northwest as a whole is projected to gain in average annual precipitation due to global warming—but recent years have seen reduced precipitation in parts of the Blue Mountains. It is certain, however, that higher average temperatures will lead to reduced snowpack, earlier snowmelts, and lower water flow in the warm season. Such alterations to the hydrologic cycle will sometimes cause dramatic changes in local habitats, which naturally must give rise to species migration to other temperature zones, behavioral and genetic adaptation, or extinction.

Holding back habitat fragmentation becomes especially critical under such conditions. Federal reserves situated wholly or partly in this biome include the Malheur, Umatilla, and Wallowa-Whitman National Forests. There are many state parks, as well as federal Wilderness Areas. The Blue Mountains Forest Reserve was established on 2.63 million acres (1.06 million hectares) in 1906 following several years of patchwork, informal reserve-creating in Oregon. President Theodore Roosevelt, in 1907, signed an expansion of the reserve; much of this area was subdivided by the National Forest Service for better regional management.

Bibliography

Franklin, Jerry F., and C. Ted Dyrness. Natural Vegetation of Oregon and Washington. Oregon State University Press, 1973.

Halofsky, Jessica E., and David L. Peterson. "Climate Change Vulnerability and Adaptation in the Blue Mountains." U.S. Department of Agriculture, 2017, doi.org/10.2737/PNW-GTR-939. Accessed 30 Oct. 2024.

Mitchell, Steven. "BIC Completes Desired Conditions for Blue Mountain Management Plan." Blue Mountain Eagle, 9 Feb. 2022, www.bluemountaineagle.com/news/bic-completes-desired-conditions-for-blue-mountain-forest-management-plan/article‗56fd653a-858e-11ec-95ce-f381570ddbde.html. Accessed 30 Oct. 2024.

National Research Council. Environmental Issues in Pacific Northwest Forest Management. National Academies Press, 2000.

Quigley, Thomas M. Forest Health in the Blue Mountains: Science Perspectives. Pacific Northwest Research Station, 1994.

U.S. Forest Service. Wildlife Habitats in Managed Areas: The Blue Mountains of Oregon and Washington. U.S. Department of Agriculture, 1979.