Bigcone Douglas-fir

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The Bigcone Douglas-fir, Pseudotsuga macrocarpa, is an evergreen conifer native to the mountains of southern California, occurring from the San Rafael Mountains in central Santa Barbara County and the southwest of the Tehachapi Mountains of southwestern Kern County, south to Julian in San Diego County. It is notable for having the largest (by far) cones in its genus, hence the name.

Contents

Description

Pseudotsuga macrocarpa, Bigcone Douglas-fir, typically grows from 15-30 m (50-100 feet) in height and 0.5-1.5 m (2-5 feet) in trunk diameter. The growth form is straight, with a conical crown from 12-30 m (40-100 feet) broad, and a strong and spreading root system. The bark is deeply ridged, composed of thin, woodlike plates separating heavy layers of cork; bark of trees over 1 m (3 feet) in diameter is from 15-20 cm (6-8 inches) thick. The main branches are long and spreading with pendulous side shoots.

The leaves are needle-like, 2.5-5 cm (1-2 inches) long, are shed when about 5 years old. The female cones are from 10-18 cm (4-7 inches) long, larger and with thicker scales than those of other douglas-firs, and with exserted tridentine bracts. The seeds are large and heavy, 10 mm long and 8 mm broad, with a short rounded wing 12 mm long; they may be bird or mammal dispersed as the wing is too small to be effective for wind dispersal. Trees start producing seeds at about 20 years of age.

The largest known Bigcone Douglas-fir is 53 m (173 feet) tall, 231 cm (91 inches) in diameter, and is estimated to be from 600 to 700 years of age.

Distribution

Pseudotsuga macrocarpa is restricted to the California montane chaparral and woodlands and California coastal sage and chaparral ecoregions of California. It prefers a Mediterranean climate, characterized by hot dry summers and wet, mild winters. Annual rainfall during a 30-year period on a Bigcone Douglas-fir site in the San Gabriel Mountains averaged 75 cm (30 inches) and ranged from 25-125 cm (10-50 inches). Bigcone Douglas-fir occurs between 300-2,700 m (1,000-8,000 feet). At low elevation, it occurs near streams in moist, shaded canyons and draws where aspects are mostly north and east. At elevations from 1,350-1,700 m (4,440-5,600 feet), aspects include south- and east-facing slopes. At these elevations, it also grows on sloping hillsides, ridges, and benches. At higher elevations, it occurs on south and west aspects on all types of terrain. The average angle of slope on which it grows is 35 degrees, ranging from level to 90 degrees, although these extremes are uncommon.

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