Douglas-fir and other conifers associate with it to form perhaps the densest of all coniferous forests, with the world's largest trees. This is typically open forest mixed with grass and shrubs. It occurs throughout the Southwest, the Sierra Nevada, the Rocky Mountains, and the Black Hills. An open, parklike stand of ponderosa pine, Deschutes National Forest, Oregon. The high, snowcapped mountains of the Cascades have a well-marked subalpine forest belt that reaches into British Columbia.
Important trees are mountain hemlock, subalpine fir, whitebark pine, and Alaska-cedar.
To the north, the subalpine forest becomes fragmentary or disappears completely. All but the highest peaks are covered by forest. Above timberline, there is an alpine zone with rich communities of shrubs and herbs. Perpetual snow is confined to small patches. Riparian forests in the Pacific Northwest are an exception to the general rule that conifers dominate in the region.