Bigcone Douglas-fir

Pseudotsuga macrocarpa

BigCone_AlisonSheeheyThe bigcone Douglas-fir is an evergreen conifer found only in the mountains of southern California, from the San Rafael Mountains in Los Padres National Forest south to San Diego. It gains its name by having the largest (by far) cones of all Douglas firs. The species was discovered in 1858 by an expedition who sighted the tree in San Felipe canyon near Julian in San Diego County. Early botanical writers were perplexed by the similarities between the bigcone and other Douglas firs – the only differences being the bigcone’s extra-large cone size and growth habits.

Bigcone Douglas-fir is one of twelve “Management Indicator Species” for the Los Padres National Forest. It was selected for MIS status because they are believed to be a good indicator of the health of the ecosystem. They provide habitat for many rare wildlife species, including the California spotted owl, which depends on old-growth bigcone Douglas-firs and other conifers for survival.

Species Description

BigCone_ConeBigcone Douglas fir typically grows from 60-100 feet in height with a 2-5 foot trunk diameter and a collection of long branches giving it a sparse look. One of the largest big cone Douglas-fir trees on the Los Padres is located near Antimony Peak in Kern County, and measures more than 7 feet in diameter!

Cones are from 4-7 inches long (see photo, comparing the much larger cone of the bigcone Douglas-fir with the smaller Douglas-fir cone), with larger, thicker scales than those of other Douglas firs. The seeds are actually so large and heavy that they are probably 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, and can live to be hundreds of years old (the oldest recorded bigcone Douglas fir was over 600 years old!).

Range

bigcon1The range of the bigcone Douglas fir is about 135 miles from north to south and about 210 miles from east to west. Northern limits are near Mount Pinos in Kern County, and the headwaters of La Brea Creek in Santa Barbara County. Westernmost limits are Mission Canyon in the Santa Ynez Mountains, and Zaca Peak in the San Rafael Mountains. Older publications claimed that bigcone Douglas fir grew in central Baja California, Mexico; a more recent publication verifies that it does not. The southern limit of the species is near the small mountain town of Julian, in San Diego County. The trees can grow under a wide variety of conditions: from under 1,000 feet elevation to over 8,000 feet, and chooses different orientation and ‘neighbor species’ depending on altitudinal conditions and climatic influences.

Bigcones & Wildfire

Bigcone Douglas is one of the most fire resistant and fire adapted conifers in the world, beat only by redwoods in its ability to recover from fire. Its thick bark and the presence of numerous buds on the upper side of the branches aid in its resistance – the trees will sprout from the burnt upper crown and the apparently dead tree becomes green again the following spring! Bigcones are also usually free from bark beetle attacks post-fire.

MD_df_standThese adaptations suggest that the species has evolved to survive multiple fire events that sweep through these stands from the surrounding chaparral. A 2009 study conducted in the Los Padres National Forest looked at tree rings and fire scars on 85 bigcone Douglas-firs at 15 different sites. The earliest fire scars detected dated back to the year 1600, allowing scientists to reconstruct four centuries of fire history. The results indicated evidence of fire every 23-45 years in bigcone Douglas-fir ecosystems.