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Wednesday, March 12, 2014

Wildlife Wednesday: Bigcone Douglas Fir

Bigcone Douglas fir in its natural habitat in the Dick Smith Wilderness
For this week’s Wildlife Wednesday we are going to look at a species that isn’t technically wildlife, nor does it occur on Tejon Ranch. What could possibly be that awesome? The topic for this post is the bigcone Douglas fir (Pseudostuga macrocarpa), of course! Many will be familiar with the bigcone’s cousin, Douglas fir (Pseudotsuga menziesii), which is common in forests throughout the west. Bigcone Douglas fir on the other hand, is endemic to California and only occurs from San Diego to Kern counties. 

The most obvious characteristic that makes this tree distinct is its cone. Essentially, it looks like a P. menziesii cone on steroids. The bigcone Douglas fir cone can be up to 7” long and sports the familiar three-pointed “mouse-tails” that can also be found on P. menziesii cones. In addition to its cones, the bigcone Douglas fir can be distinguished by its short needles and interesting growth form. Ronald M. Lanner sums it up pretty well in Conifers of California when he says, “Within its range, what appear to be the masts and spars of old square-riggers, arising from a ravine or a steep mountain slope, can only be an old-growth stand of bigcone-spruces [bigcone Douglas fir].” (Lanner, 1999 pg. 163)

Normal Douglas fir (P. menziesii) cone. Photo courtesy of Jordan Swank


P. macrocarpa cone. Does the name make more sense now?

Scot's nearest bigcone is just a few minutes' walk from his house
 One of the most interesting aspects of this amazing plant to us at the Conservancy is its range. Bigcone Douglas fir is known to occur from the Peninsular Ranges of eastern San Diego County, through the Transverse Ranges into Santa Barbara County. All told, this adds up to an approximately 315mi north-south range, making P. macrocarpa a true southern Californian (Gause, 1966).
Within its range the bigcone can be found at a variety of elevations (900-7,400’) (Gause, 1966; Lanner 1999). Most typically, this tree will be seen clinging onto steep slopes and ridgetops. The interesting thing is that despite having plenty of seemingly suitable habitat for this species on Tejon Ranch, no one at the Conservancy has seen it here. A quick check on Calflora yields one sighting from 1932 that we have not yet verified. 

For as much as we like to talk about the incredible diversity of Tejon Ranch, it can also be interesting to think about what species are absent. Why is it that we see bigcone Douglas fir at Ft. Tejon State Park just west of I-5, but not east of I-5? At my home in Pine Mountain Club, a five-minute walk leads me to a stately bigcone. For the armchair ecologist, it is possible to develop several theories about this absence: is it possible that the movements of the San Andreas Fault pushed blocks of land containing bigcone Douglas fir next to areas that did not have it historically? A look at the tree’s distribution shows its presence on both sides of the Fault, possibly debunking that theory. What if the Antelope Valley side of the ranch is just too dry to support these trees and the Tehachapis represent a barrier to their dispersal north? Maybe we just haven’t looked hard enough, or in the right places. 

Whatever the answer truly is, it will take some serious study to fully understand the dynamics of this tree’s distribution. Until that answer comes, we will keep our eyes trained on the ridges in hopes of seeing this spectacular California endemic.

Gause, Gerald W. 1966. Silvical Characteristics of Bigcone Douglas-fir (Pseudotsuga macrocarpa [Vasey] Mayr). Berkeley, Calif, Pacific SW Forest & Range Exp. Sta.
Lanner, Ronald M. 1999. Conifers of California. Los Olivos: Cachuma Press.