California Red Fir Forest

This ecological system includes high-elevation (1600-2700 m [4850-9000 feet]) forests and woodlands dominated by Abies magnifica var. magnifica, Abies magnifica var. shastensis, and/or Abies procera. This system is typically found on deep, well-drained soils throughout this elevation zone from the central Sierra Nevada north and west into southern Oregon. Heavy snowpack is a major source of soil moisture throughout the growing season. The limiting factors can be either cold-air drainages or ponding, or coarser soils (pumice versus ash, for example). Other conifers that can occur in varying mixtures with Abies magnifica include Pinus contorta var. murrayana, Pinus monticola, Tsuga mertensiana, Pinus jeffreyi, and Abies lowiana. At warmer and lower sites of the North Coast Ranges and Sierra Nevada, Abies lowiana can codominate with Abies magnifica. Pinus contorta in Oregon indicates lower productivity where it intergrades with Abies magnifica var. shastensis. This system ranges from dry to moist, and some sites have mesic indicator species, such as Ligusticum grayi or Thalictrum fendleri. Common understory species include Quercus vacciniifolia, Ribes viscosissimum, Chrysolepis sempervirens, Ceanothus cordulatus (in seral stands), Vaccinium membranaceum, Symphoricarpos mollis, and Symphoricarpos rotundifolius. Characteristic forbs include Eucephalus breweri, Pedicularis semibarbata, and Hieracium albiflorum. This system commonly occurs above mixed conifer forests with Abies lowiana and overlaps in elevation with forests and woodlands of Pinus contorta var. murrayana. On volcanic sites of lower productivity, stands may be more open woodland in structure and with poor-site understory species such as Wyethia mollis. Driving ecological processes include occasional blowdown, insect outbreaks and stand-replacing fire.

These forests and woodlands are dominated by Abies magnifica var. magnifica, Abies magnifica var. shastensis, and/or Abies procera. Other conifers that can occur in varying mixtures with Abies magnifica include Pinus contorta var. murrayana, Pinus monticola, Tsuga mertensiana, Pinus jeffreyi, and Abies lowiana (= Abies concolor var. lowiana). At warmer and lower sites of the North Coast Ranges and Sierra Nevada, Abies lowiana can codominate with Abies magnifica. Pinus contorta in Oregon indicates lower productivity where it intergrades with Abies magnifica var. shastensis (= Abies x shastensis). This system ranges from dry to moist, and some sites have mesic indicator species, such as Ligusticum grayi or Thalictrum fendleri. Common understory species include Quercus vacciniifolia, Ribes viscosissimum, Chrysolepis sempervirens, Ceanothus cordulatus (in seral stands), Vaccinium membranaceum, Symphoricarpos mollis, and Symphoricarpos rotundifolius. Characteristic forbs include Eucephalus breweri, Pedicularis semibarbata, and Hieracium albiflorum. This system commonly occurs above mixed conifer forests with Abies lowiana and overlaps in elevation with forests and woodlands of Pinus contorta var. murrayana. On volcanic sites of lower productivity, stands may be more open woodland in structure and with poor-site understory species such as Wyethia mollis.

Red fir forests occur at high elevations (1600-2700 m [4850-9000 feet]), and are typically found on deep, well-drained soils throughout this elevational zone from the central Sierra Nevada north and west into southern Oregon. Heavy snowpack is a major source of soil moisture throughout the growing season. Climate is relative mild for high-elevation forest with summer temperatures rarely exceeding 29°C (85°F) and winter temperatures rarely fall below -29°C (-20°F). Summers are dry (4-5 months). Between May (or April) and October summer thunderstorm precipitation is negligible, almost all precipitation occurs from October to March, 80% as snow. Snowpack can exceed 4 m (13 feet). Total ppt per year ranges 750-1500 mm (30-60 inches).

Stand-replacing fire is important but so are moderately frequent (about once every 40 years) low- to moderate-severity fires. The whole system is characterized by a "moderate-severity fire regime" (Agee 1993), i.e., high variability in severity and moderate frequency of fires. See also Chappell and Agee (1996), Pitcher (1987), and Taylor and Halpern (1991) for documentation of fire regime in these forests. Windthrow causes tree-sized gaps that release already established individuals in the understory.

TNC model information: At higher elevations and in the southern Sierra Nevada, fuels are relatively more discontinuous than northern locations because the terrain is broken up by natural breaks such as rock outcrops, lava reefs, wet meadows, etc. Fuels may be more continuous at the northern end of the range, where this vegetation type is found at lower elevations. Primarily Fire Regime Group III, but because of slow fuel accumulation rates, it is possible to have 35- to 150-year frequency surface fire in some classes (lower frequency for these settings as a whole). The discontinuous nature of the fuels limits the extent of fires, and while fires may burn less often, they may burn at high severities. Larger and more frequent moderate-intensity fires occur on average every 60-70 years. High-intensity crown fires are rare, occurring every few hundred years; overall mean fire-return interval is approximately 35-50 years (Pitcher 1987, Skinner 2000, Taylor 2000, Bekker and Taylor 2001). Replacement fire likely varies with slope position (upper slope > midslope > lower slope), and landscapes with greater topographic variation are likely to experience more stand-replacement fires. A considerable range of values has been reported in the literature for mixed and surface fires (Taylor and Halpern 1991, Taylor 1993, Bekker and Taylor 2001, Taylor and Solem 2001).

This system is typically found on deep, well-drained soils throughout the high-elevation zone (1600-2700 m [4850-8200 feet]) from the central Sierra Nevada north and west into southern Oregon.