Sierra Nevada and Desert White Pine-White Fir Woodland

This interior Pacific Northwest ecological system occurs on the Modoc Plateau and Warner Mountains of California, north into the Fremont National Forest along the east slope of the southern Cascades in Oregon, and may also occur in isolated high-elevation ranges of northern Nevada. These forests and woodlands range from just above the zone of ponderosa pine in the montane zone, to the upper montane zone. Elevations range from 1370 m to over 2135 m (4500-7000 feet). Occurrences are found on all slopes and aspects, although more frequently on drier areas, including northwest- and southeast-facing slopes, but also occurs on northerly slopes and ridges. This ecological system generally occurs on basalts, andesite, glacial till, basaltic rubble, colluvium, or volcanic ash-derived soils, and sometimes on granitics (Carson Range). These soils have characteristic features of good aeration and drainage, coarse textures, circumneutral to slightly acidic pH, an abundance of mineral material, rockiness, and periods of drought during the growing season. Climatically, this system occurs somewhat in the rainshadow of the Sierras and Cascades and has a more continental regime, similar to the northern Great Basin. This system tends to be more woodland than forest in character, and the undergrowth is more open and drier, with little shrub or herbaceous cover. Tree regeneration is less prolific than in other mixed-montane conifer systems of the Cascades, Sierras and California Coast Ranges. Pinus monticola is the dominant conifer in most places, but Abies lowiana (= Abies concolor var. lowiana) is usually present, at least in the understory, and occasionally as the dominant in the canopy, replacing Pinus monticola, particularly at lower elevations, and Pinus ponderosa is also often present. In the Warner Mountains, the Abies lowiana stands range from 1675 to 2135 m (5500-7000 feet) in elevation, and the mixed Pinus monticola - Abies lowiana is usually above 2135 m (7000 feet). Mixed stands with Pinus contorta, in moister locations, as well as Pinus jeffreyi and sometimes Populus tremuloides occasionally occur. Southern stands (around Babbitt Peak and in the Carson Range) can sometime have Abies magnifica in them, sometimes replacing Abies lowiana. These forests and woodlands are marked by the absence of Pseudotsuga menziesii, Pinus lambertiana, and Calocedrus decurrens, and the generally drier, continental climatic conditions. In addition, the overall floristic affinities are with the Great Basin rather than Pacific Northwest. Understories are typically open, with moderately low shrub cover and diversity, and include Arctostaphylos patula, Arctostaphylos nevadensis, Chrysolepis sempervirens, Ceanothus sp., and Ribes viscosissimum. Common herbaceous taxa include Arnica cordifolia, Festuca sp., Poa nervosa, Carex inops, Pyrola picta, and Hieracium albiflorum. In openings, Wyethia mollis can be abundant.

The open nature of the stands suggests regeneration and establishment is slow and sporadic. Stand-replacing events are not frequent; most fire is probably partial stand disturbance. These stands are relatively high elevation, and there are generally widely spaced large and somewhat fire-resistant individuals. Also the discontinuous understory and only patchy regeneration suggests non-stand-replacing fire as the norm., rather patchy burns with isolated trees surviving regularly. Local windthrow, insects, disease (blister rust), and individual lightning strikes probably make up most of the disturbances.

This ecological system is found in the transition zone from the northern Sierra Nevada of California and Oregon, east into the Modoc Plateau and Intermountain region of northwestern Nevada. It is found in the Fremont National Forest east of Lake View in Oregon, and in the Modoc Plateau and Warner Mountains of California. It continues farther south in California to the Diamond Mountains south of Honey Lake (a northeast extension of the Sierras), on Babbitt Peak between Lake Tahoe and Sierra Valley, and also in the Carson Range in Nevada east of Lake Tahoe Scattered stands may occur on Hart Mountain and Steens Mountain in Oregon and possibly a few isolated places in the northern Great Basin and the Jarbridge Mountains of Nevada.