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Western Coniferous Forest

The Rocky Mountains, Sierra Nevada, and Cascades are blanketed with dense forests of mixed conifers, some of the most magnificent forests in the world. The tall mountain ranges intercept the clouds as they move in from the Pacific Ocean. As a result, there are forests even on the southern mountains amidst deserts and grasslands. Only in the cool North, where rainfall is abundant, are there dense forests in the valleys as well. On the mountain slopes, soils are generally shallow and composed of organic duff or peat. In the valleys, alluvial soils from the eroding mountains are deep and rich. Wildlife abounds in the western forests, including elk, moose, bear, squirrels, and birds. Campers are familiar with the thieving jays, often called camp robbers, who never pass up a handout.

Gardeners in this region have cool summers - perfect for growing perennials. The coastal regions have mild winters as well and are a gardening paradise. The herbaceous border so admired in English gardening books, lush with plants from around the globe, is most attainable here.

Three distinct associations are found in the Western Coniferous Forest: the Northwest Coastal Forest, the Sierra Montane Forest, and the Rocky Mountain Montane Forest. Each association has its unique assemblage of species, but trees such as Douglas fir and lodgepole pine are common across the entire province. At higher elevations lie the subalpine zones.

Once Upon a Forest

Some 50 million years ago, before the great ice age, a lush forest stretched across North America from coast to coast. The northern reaches of the forest were dominated by mixed stands of deciduous and coniferous trees. In these stands grew the ancestors of the common conifers and deciduous trees we know today - oaks, magnolias, spruces, firs. The central and southern regions were subtropical. Ginkgo, ferns, and trees similar to those in present-day Australia were common.

Over the next 45 million years, forces altered the face of the continent. The western mountain ranges slowly began to rise, and in time divided the continent into distinct sections. These mountains changed rainfall patterns, and vast grasslands came to dominate the Midwest, separating the forests of the East and West. The stage was set for divergent evolution. The deciduous trees could not thrive in the cool, arid West, and conifers dominated. The humid East became a great deciduous forest. When the ice age began 3 million years ago, plants began migrating in response to warming and cooling trends, but the basic division in vegetation between East and West was already in place. With the final retreat of the ice between 10 and 7 thousand years ago, the die was cast for the distribution of species we see today.

Northwest Coastal Forest

The Northwest Coastal Forest is dominated by Sitka spruce, western hemlock, western white cedar, and, at its southernmost locations, towering redwoods. The forests of northern California, Oregon, and Washington have been at the center of a controversy for years, as huge stands of old-growth trees have fallen to the saw. The northern Pacific Coast receives over 100 inches of rain a year. The temperate rainforest in this region is lush and productive.

Sierra Montane Association

This association carpets the slopes and valleys of the Sierra Nevada Mountain chain. The moist, rich soils of valley floors and lower mountain slopes favor incense cedar, Douglas fir, and ponderosa pine. In these areas, the canopy is closed. In sheltered valleys, ancient forests of sequoia are found. These trees may be as much as two thousand years old. The drier slopes are host to many pines, especially lodgepole and sugar pines (Pinus contorta and Pinus lambertiana), as well as Douglas fir. Here, the trees are more dispersed and the canopy is more open.

Rocky Mountain Forest

The Rocky Mountain association is dominated by ponderosa pine, lodgepole pine, and Douglas fir. Moist forests in valleys and along streams have closed-canopy forests of Douglas fir, western red cedar, and western hemlock (Tsuga heterophylla). The drier slopes have a sparse canopy with a thick shrub layer of redroots (Ceanothus species) and ocean spray (Holodiscus discolor). In the hotter, drier southern reaches of the mountains, pinyon-juniper woodlands are found. These trees grow in open communities with grasses, bulbs such as mariposa lilies (Calochortus species), and annual wildflowers. The soil is generally shallow and rocky.

Subalpine Forest>