Abies concolor

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Description

The white fir (Figure 1) is a conifer with flat, grayish-green needles. The cone length averages 3-6 inches long and the cones sit upright on the branches. Wind pollination facilitates seed fertilization and the cones disintegrate 6 months after pollination. The twigs and stems of the white fir remain smooth after the needles have been shed. The white fir grows to an average height of 30-50 feet.

Identification

It is often difficult to distinguish the white fir from its close relative, the subalpine fir (Abies lasiocarpa); however, the two can be determined by the location of the large resin ducts inside the needle. By examining a needle in cross-section, the white fir has resin ducts located directly underneath the epidermis of the needles; the ducts of the subalpine fir are located toward the center of the needle, away from the epidermis (Figure 2).

Distribution

The native range of the white fir (Figure 3) lies in the mountains of Oregon, California, Idaho, Utah, Colorado, Arizona, and New Mexico. It grows at elevations of 900-3,400 meters (3,000-11,000 feet) depending on annual precipitation; in areas with lesser amounts of annual precipitation, such as Utah, the white fir grows at elevations of 1,800-2,400 meters (6,000-8,000 feet) in order to remain in moist soils.

Ecology

At higher elevations, the white fir has adapted to environmental stresses, such as a short growing season, low winter temperatures, and high UV light. The white fir is also shade tolerant, which allows it to compete with other conifers that may try to shade it out.

White fir mistletoe (Phoradendron bolleanum) and white fir dwarf mistletoe (Arceuthobium abietinum) are parasites to the white fir which cause extensive damage to the wood and increase the treeÕs susceptibility to bark beetles.

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Figure 1. Abies concolor; photo by Hans-Otto Tengrud.




Figure 2. Resin duct location in a needle cross-section of Abies concolor (left) and Abies lasiocarpa (right).




Figure 3. The native range of California white fir (left) and Rocky Mountain white fir (right).