Picea breweriana (weeping spruce) description

Picea breweriana

S. Watson 1885

Common names

Weeping spruce, Brewer's spruce (Peattie 1950).

Taxonomic notes

Syn: P. brewerana.

P. breweriana is sympatric with Picea engelmannii at one location, on the slopes of Russian Peak (Sawyer and Thornburgh, 1969, 1970, cited by Ledig et al. 2005). It does not occur particularly close to Picea sitchensis; at their closest approach, populations are separated by 18.5 km and several hundred meters of elevation (Waring et al. 1975, cited by Ledig et al. 2005). No hybrids with either P. engelmannii or P. sitchensis have been observed in habitat (Sawyer and Thornburgh 1969, cited by Ledig et al. 2005), and repeated attempts at controlled pollination have failed to produce hybrids between P. breweriana and other spruces (Gordon 1986, cited by Ledig et al. 2005). Phylogenies based on molecular markers suggest that P. breweriana may stand alone in the genus with no close relatives (sources in Ledig et al. 2005).

Description

"Trees to 40 m; trunk to 150 cm diam., typically buttressed; crown conic. Bark gray to brown. Branches drooping; twigs pendent, elongate, slender, gray-brown, finely pubescent. Buds gray-brown, 5-7 mm, apex rounded. Leaves 1.5-3 cm, flattened or broadly triangular in cross section (abaxial surface rounded or slightly angular), rather rigid, abaxial surface dark green with stomatal bands absent, adaxial surface glaucous with conspicuous stomatal bands separated by slight ridge or angle, apex blunt (especially on older leaves)." Seed cones dark red-purple ripening red-brown, cylindrical, 6.5-12 (-14) cm; scales fan-shaped, 15-20 × 15-20 mm, rigid, margin at apex entire to slightly erose (Taylor 1993).

Leaves radial all around pendulous shoots, somewhat flattened down onto level shoots; pendulous shoots tend to have longer leaves (2-3 cm) than level shoots (1.5-2.5 cm). Young trees do not show pendulous branchlets until about 10-20 years old, and until then are open with level shoots and shorter leaves (1.5-2 cm); they can be confused with Picea omorika at this age.

Range

USA: SW Oregon and NW California at (530-)1000-2300 m in montane to subalpine forests of the Siskiyou Mountains (Waring et al. 1975). See map at left. The species is distributed from 22 to 145 km from the coast, in scattered populations, of which the northernmost, at Iron Mountain, is disjunct by 29 km (Ledig et al. 2005).

Waring et al. (1975) attributed its ecological success to its ability to "compete well with sparse vegetation in infertile or unbalanced soils developed from ultrabasic materials." Thus it is, like Pinus jeffreyi and Juniperus communis var. jackii, exceptionally well adapted to the serpentine-derived soils that have been responsible for so much of the unique endemic flora of the Klamath-Siskiyou Mountains.

P. breweriana grows with at least 15 other conifers (Waring et al. 1975), two of the most common being Pseudotsuga menziesii and Abies magnifica var. shastensis (in fact, the Klamath Mountains may contain the highest naturally-occurring conifer diversity that can be found within a small area, such as a square kilometer, anywhere on earth). Some of the associated conifers attain greater height and older ages, so Brewer spruce is often found in the subcanopy (Ledig et al. 2005). P. breweriana is also susceptible to fire, so it often occurs in relatively open stands on rocky and infertile soils, which are less prone to hot fires (Thornburgh 1990, cited by Ledig et al. 2005).

P. breweriana is subject to logging and other anthropogenic disturbances. Projected climate change may adversely affect it and other montane and subalpine species in the Klamath Mountains. The highest peaks in the Klamath Mountains are about 2750 m elevation, so there is little space available for P. breweriana to migrate higher in elevation (Ledig et al. 2005).

See also Thompson et al. (1999). USDA hardiness zone 6.

Big tree

Height 41.8 m, dbh 220 cm, crown spread 13.4 m, data from 1999, in Shasta-Trinity National Forest, CA (American Forests 2008).

Oldest

Reportedly its maximum age 900 years (Cowley 2000, cited by Ledig et al. 2005). I do not know the basis for this claim.

Dendrochronology

Ethnobotany

Observations

It is most easily seen in the wild at Castle Crags State Park, CA (Vladimir Dinets, e-mail 10-Jan-1998). Another good stand is at the Indian Creek Brewer Spruce Special Interest Area in Klamath National Forest, California. It is rated one of the best existing stands of this species and is close to a major paved road. The location is at 41° 59' N, 123° 31' W. In this stand, Brewer spruce grows with codominant white fir (Abies concolor) and secondary noble fir (Abies procera), Douglas-fir (Pseudotsuga menziesii), and sugar pine (Pinus lambertiana) (Keeler-Wolf 1990).

An even more impressive, but less accessible stand is preserved in the Rock Creek Butte Research Natural Area on the Klamath National Forest (41° 33' N, 123° 38' W). Some trees in this stand are 122 cm dbh and 40 m tall, and are thought to be over 400 years old. The main stand is on the NW and NE sides of Rock Creek Butte, and covers about 75 ha. Along with Brewer spruce, it contains large Douglas-fir (Pseudotsuga menziesii) and smaller noble fir (Abies procera), along with secondary white fir (Abies concolor), sugar pine (Pinus lambertiana), western white pine (Pinus monticola), and incense-cedar (Calocedrus decurrens). Western yew (Taxus brevifolia) occurs in the understory (Keeler-Wolf 1990).

In Oregon, it can be found at the Brewer Spruce Research Natural Area; see the link for details.

Remarks

Named for its discoverer, William Henry Brewer (1828-1910), a professor of agriculture at Yale University in Connecticut.

P. breweriana has been found in Miocene and Pliocene and Miocene sediments in Idaho and Nevada, central Oregon, and central California (Wolfe 1964, cited in Ledig et al. 2005). The fossil species (Picea sonomensis Axelrod), synonymous with P. breweriana, is recorded in the Oligocene Creede Flora of southwest Colorado (Axelrod 1987, cited in Ledig et al. 2005). Its distribution seems to have shrunk along with other components of the Arcto-Tertiary flora as mountain building, especially in late Miocene along the west coast, resulted in widespread drier climates in what is now the western U.S. Cool moist forests were largely restricted to the coast and higher elevations (Whittaker 1961, cited in Ledig et al. 2005). The Klamath Geomorphological Province, where P. breweriana is endemic, is filled with relictes of the Arcto-Tertiary flora (Whittaker 1960 and Sawyer and Thornburgh 1977, both cited by Ledig et al. 2005).

Although of limited distribution, the species is listed as low risk, not threatened because it is not exploited for timber and a significant fraction of its range is formally protected, e.g. within the Siskiyou Wilderness.

This is a highly ornamental species, with long curtains of strikingly pendulous branchlets from upswept or level branches. Slow growing and difficult to establish in cultivation, it is highly prized in British horticulture, but its low climate tolerance limits the regions in the USA which it can be grown successfully.

"The presence of alkaloids from two distinct biosynthetic pathways, one of which is, so far, novel for conifers, underscores the uniqueness of the species" (Schneider et al. 1995, cited by Ledig et al. 2005).

Citations

Cowley, A. 2000. California's biggest trees: a cultural and economic resource. Northern California Society of American Foresters, Porterville, CA.

Gordon, A.G. 1986. Breeding, genetics and genecological studies in spruce for tree improvement in 1983 and 1984, Sault Ste. Marie, Ontario. Pp. 112-116 in C.W. Yeatman and T.J.B. Boyle (eds.), Proceedings of the Twentieth Meeting of the Canadian Tree Improvement Association, part 1. Quebec City, Quebec.

Ledig, F.T., P.D. Hodgskiss, and D.R. Johnson. 2005. Genic diversity, genetic structure, and mating system of Brewer spruce (Pinaceae), a relict of the Arcto-Tertiary forest. American Journal of Botany 92:1975-1986. Available: http://www.amjbot.org/cgi/content/full/92/12/1975, accessed 2007.05.19.

Sawyer Jr., J.O. and D.A. Thornburgh. 1969. Ecological reconnaissance of relict conifers in the Klamath Region. USFS, Pacific Southwest Coop-Aid Grant no. 7, contract no. 21-52.

Sawyer Jr., J.O. and D.A. Thornburgh. 1970. The ecology of relict conifers in the Klamath Region, California. USFS, Pacific Southwest Coop-Aid Grant no. 9, contract no. 21-52.

Sawyer Jr., J.O. and D.A. Thornburgh. 1977. Montane and subalpine vegetation of the Klamath Mountains. Pp. 699-732 in M.G. Barbour and J. Major (eds.), Terrestrial vegetation of California. New York: John Wiley.

Thornburgh, D. 1990. Picea breweriana Wats. Brewer spruce. Pp. 181-186 in

Burns and Honkala 1990.

Waring, R.H., W.H. Emmingham, and S.W. Running. 1975. Environmental limits of an endemic spruce, Picea breweriana. Canadian Journal of Botany 53: 1599-1613.

Whittaker, R.H. 1960. Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monographs 30: 279-338.

Whittaker, R.H. 1961. Vegetation history of the Pacific Coast states and the "central" significance of the Klamath Region. Madroño 16: 5-23.

Wolfe, J.A. 1964. Miocene floras from Fingerrock Wash southwestern Nevada . USGS Professional Paper 454-N.

This page co-edited with Michael P. Frankis (1998.12).