Common Names

Interior (Silba 1986) or Rocky Mountain (American Forests 1996) Douglas-fir; pino real colorado (Lipscomb 1993); blue Douglas-fir (Burns & Honkala 1990).

Taxonomic notes

Syn: Pseudotsuga douglasii (Lindley) Carrière var. glauca Mayr 1890 (Lipscomb 1993); P. menziesii subsp. glaucescens. P. lindleyana is also commonly treated within this variety; see that description for details.

Description

Trees to 40(-50) m; trunk to 1.2 m diam. Leaves bluish green to dark green or gray-green. Seed cones 4-7 cm; bracts spreading, often reflexed. 2n=26 (Lipscomb 1993).

Range

Canada: Alberta and British Columbia; USA: Montana, Idaho, Washington, Oregon, Nevada, Utah, Wyoming, Colorado, Arizona, New Mexico and Texas; Mexico; at 600-3000 m in conifer or mixed forests (Lipscomb 1993).

"The range of Douglas-fir is fairly continuous through northern Idaho, western Montana, and northwestern Wyoming. Several outliers are present in Alberta and the eastern-central parts of Montana and Wyoming, the largest being in the Bighorn Mountains of Wyoming. In northeastern Oregon, and from southern Idaho south through the mountains of Utah, Nevada, Colorado, New Mexico, Arizona, extreme western Texas, and northern Mexico, the distribution becomes discontinuous.

"Douglas-fir grows under a wide variety of climatic conditions [see Table, below] ... In the northern Rocky Mountains, Douglas-fir grows in a climate with a marked maritime influence. Mild continental climate prevails in all seasons, except midsummer. Precipitation is evenly distributed throughout the year, except for a dry period in July and August. In the central Rocky Mountains, the climate is continental. Winters are long and severe; summers are hot and in some parts of the region, very dry. Annual precipitation, higher on the western sides of the mountains, is mainly snow. Rainfall patterns for the southern Rocky Mountains generally show low winter precipitation east of the Continental Divide but high precipitation during the growing season. West of the Continental Divide, the rainfall is more evenly divided between winter and summer. Frost may occur in any month in the northern part of the range. Length of frost-free periods, however, varies within the central and southern Rocky Mountain regions, even at the same elevations.

"Soils within the range of Rocky Mountain Douglas-fir originated from a considerable array of parent materials. In south-central British Columbia, eastern Washington, and northern Idaho, soils vary from basaltic talus to deep bess with volcanic ash to thin residual soil over granitic or sedimentary rocks. They are mostly Vitrandepts and Xerochrepts. Parent materials in Montana and Wyoming consist of both igneous and sedimentary rocks, and locally of glacial moraines. Soils derived from noncalcareous substrates are variable in texture but consistently gravelly and acidic. A significant portion of the sedimentary rocks is limestone, which gives rise to neutral or alkaline soils ranging in texture from gravelly loams to gravelly silts. Limestones often weather into soils that are excessively well drained. Soils are Cryoboralfs of the order Alfisols, and Cryandepts and Cryochrepts of the order Inceptisols. Soils in the central and southern Rocky Mountains are very complex. They developed from glacial deposits, crystalline granitic rocks, conglomerates, sandstones, and, in the Southwest, limestones. These soils are Alfisols (Gray Wooded soils), Mollisols (Brown Forest soils), Spodosols (Brown Podzolic soils, Podzols), and Entisols.

"Generally, the variety glauca grows at considerably higher altitudes than the coastal variety of comparable latitude. ... The inland variety grows at elevations from 550 to 2440 m (1,800 to 8,000 ft) in the northern part of its range. In the central Rocky Mountains, Douglas-fir grows mostly at elevations between 1830 and 2590 m (6,000 and 8,000 ft), and in the southern Rocky Mountains, between 2440 and 2900 m (8,000 and 9,500 ft). In some localities in southern and central Arizona, Douglas-fir may be found as low as 1550 m (5,100 ft) in canyon bottoms. The highest elevation at which Douglas-fir grows in the Rocky Mountains is 3260 m (10,700 ft) on the crest of Mount Graham in southeastern Arizona.

"Rocky Mountain Douglas-fir grows in extensive pure stands, uneven- and even-aged, in southern Idaho and northern Utah and in western Montana as a broad belt between ponderosa pine and spruce fir zones. At high elevations or northerly latitudes, more cold-tolerant mountain hemlock (Tsuga mertensiana), whitebark pine (Pinus albicaulis), true firs (Abies spp.), Engelmann spruce (Picea engelmannii), western white pine (Pinus monticola), and lodgepole pine (Pinus contorta) gradually replace Douglas-fir. ...

"Wherever Douglas-fir grows in mixture with other species, the proportion may vary greatly, depending on aspect, elevation, kind of soil, and the past history of an area, especially as it relates to fire. This is particularly true of the mixed conifer stands in the southern Rocky Mountains where Douglas-fir is associated with ponderosa pine, southwestern white pine (Pinus strobiformis), corkbark fir (Abies lasiocarpa var. arizonica), white fir (Abies concolor), blue spruce (Picea pungens), Engelmann spruce, and aspen (Populus spp.).

"Principal understory species associated with variety glauca differ within its range. In the northern part, they are common snowberry (Symphoricarpos albus), white spirea (Spirea betulifolia), ninebark (Physocarpus malvaceus), and pachistima (Pachistima myrsinites). In the central part, they are true mountain-mahogany (Cercocarpus montanus), squaw currant (Ribes cereum), chokeberry (Prunus virginiana), big sagebrush (Artemisia tridentata), western serviceberry (Amelanchier alnifolia), and bush rockspirea (Holodiscus dumosus); in the southern part they are New Mexico locust (Robinia neomexicana), Rocky Mountain maple (Acer glabrum), and oceanspray" (Burns & Honkala 1990).

Table 1. Climatic data for [three] regional subdivisions of the range of [Rocky Mountain] Douglas-fir (Source: Burns & Honkala 1990).

Region	Mean temperature		Frost-free period	Mean precipitation
	July	January		Annual	Snow fall
	°C	°C	days	mm	cm
Rocky Mountains: Northern	14 to 20	-7 to 3	60 to 120	560 to 1020	40 to 580
Rocky Mountains: Central	14 to 21	-9 to -6	65 to 130	360 to 610	50 to 460
Rocky Mountains: Southern	7 to 11	0 to 2	50 to 110	410 to 760	180 to 300

Big Tree

The tallest, and largest in the state of Idaho, is a tree near Clarkia 67.4 m tall and 179 cm dbh. The largest specimen known in Washington is 53.3 m tall and 191 cm dbh, and grows in the Umatilla National Forest. In British Columbia, the largest known trees are 45.7 m tall and 185 cm dbh for a tree near Princeton, and 37.5 m tall and 194 cm dbh for a tree near Bridesville (Robert Van Pelt e-mail 4-Feb-2004).

Oldest

A crossdated age of 1275 years for specimen BIC 63 from N NM collected by Henri Grissino-Mayer (Brown 1996). I believe this is from a living tree, collected in the late 1980s or early 1990s.

Dendrochronology

Early work by Schulman (1941) established the suitability of the species for analysis and began the collection of numerous chronologies from the American Southwest. Brubaker and Graumlich collected several chronologies from Washington in the 1980s.

Ethnobotany

Observations

Some fine stands are in the Okanogan area of Washington, for instance along the road from Winthrop to Mount Tiffany and along the trails into the southern Pasayten Wilderness. It is also common in the Rockies (from Idaho and Montana south to Arizona). Large trees are fairly common; for instance, I once found a specimen 170 cm in diameter in a riparian area of the Chiricahua Mtns. of SE Arizona, and stands with many trees over 100 cm dbh occur atop the Santa Catalina Mtns. in Arizona.

Remarks

Citations

Schulman, E. 1941. Douglas fir chronology in Santa Catalina Mountains, Arizona. Tree-Ring Bulletin 7(3):18-19. Available online at www.treeringsociety.org/TRBTRR/TRBvol7_3.pdf (accessed 2006.06.05).

See Also

MacKinnon et al. (1992).

FEIS database.