Canyon Live Oak

''Quercus chrysolepis'', commonly termed canyon live oak, canyon oak, golden cup oak or maul oak, is a North American species of evergreen oak. Its leaves are a glossy dark green on the upper surface with prominent spines; a further identification arises from the leaves of canyon live oak being geometrically flat.

The species is found in Mexico and in the western United States, notably in the California Coast Ranges. It is often found near creeks and drainage swales growing in moist cool microhabitats.

Description

''Quercus chrysolepis'' is an evergreen tree with significant-sized spreading, horizontal branches, and a broad, rounded crown; it attains a height of 6–30 meters (20–100 feet) and often forms as a shrub. The trunk diameter typically ranges from . Exceptionally large specimens are found in the mountains of Southern California, and rank among the largest oaks in North America. The largest known in the San Bernardino Mountains measures high, with a trunk circumference of and a crown spread of . The bark is grayish brown, and rather smooth or sometimes scaly.

The elliptical to oblong leaves are in length and about half as wide; they are short-pointed at the tip, and rounded or blunt at base. Although the leaves appear generally flat, they may have edge margins slightly turned under, typically with spiny teeth, particularly on young twigs. These leathery leaves are a glossy dark green above, with a nether surface a dull golden down, often becoming gray and nearly glabrous the second year.

Both male and female flowers appear on the same plant. The male flowers droop in catkins, and the female flowers originate from leaf axils, usually singly.

Acorns occur solitarily or in pairs, exhibiting lengths of 2–5 cm; these fruits are variable in size and shape, but generally ovoid, turban-like with a shallow, thick cup of scales densely covered with yellowish hairs; the stalk is barely evident.

Taxonomy

The species is placed in ''Quercus'' section ''Protobalanus''.

Distribution and habitat

''Q. chrysolepis'' is found in a variety of forest communities in the southwestern United States. It is common in the mountainous regions of California (Sierra Nevada, Coast Ranges, Klamath Mountains, Cascades, San Gabriel Mountains, etc.) with additional populations in the Siskiyou Mountains of southwestern Oregon, western Nevada, northern Baja California, Arizona, southwestern New Mexico, and Chihuahua. Southwestern New Mexico population are most likely the result of introgression from ''Quercus palmeri'' to ''Q. chrysolepis''. Those populations tend to be intermediate in overall morphology, but all lack the diagnostic trichomes and biochemical markers of ''Q.'' ''palmeri''; they are best classified as ''Q. chrysolepis'' affinity ''Q. palmer''.

Canyon live oak is tolerant of a variety of soil types, including very rocky or cobbly environments. It is hardy to cold temperatures down to −11 °F, and will grow in neutral to moderately acidic soils with pH ranges of 4.5 to 7.5. An example of very rocky and serpentine soil tolerance is the species occurrence at the Cedars of Sonoma County, California. Canyon live oak grows at elevations of about in southwestern Oregon; in Northern California, from ; and in Southern California, up to approximately . ''Q. chrysolepis'' can be the dominant tree on steep canyon walls, especially in locations of shallow rocky soils. In areas of moderate to high rainfall, it occurs on south facing slopes, and in the hotter, drier parts of its distribution, on northerly slope faces.

Fossil data supports a much wider distribution throughout the western U.S. during the early Holocene period.

Ecology

The species is often sympatric with ''Quercus agrifolia'' and several other oak species. It is more shade tolerant than Pacific madrone but not as much as the associated Douglas-fir, tanoak, and golden chinkapin. After forest fires, canyon live oak regenerates vigorously by basal sprouting, and the clonal diversity of this species has been shown to be high. It is typically succeeded by other species except in more extreme dry and rocky climates, being exceptionally drought tolerant.

The acorns are consumed by a variety of wildlife as diverse as acorn woodpecker, California ground squirrel, dusky-footed wood rat, western harvest mouse and black-tailed deer. There seems to be little difference in food preference by wildlife among different oaks. Extensive hybridization of ''Q. chrysolepis'' has been documented with several other sympatric oak species, probably to a greater extent than for any other ''Quercus'' species. The ability of ''Q. chrysolepis'' to compete with other dominant trees within its range has been analyzed from the standpoint of leaf architecture and photosynthetic capability. The study results explain that, in low light environments, ''Q. chrysolepis'' out-competes species with superior leaf size and crown mass per unit volume by its greater photosynthetic efficiency and leaf lifespan.J. C. Hunter, ''Correspondence of environmental tolerances with leaf and branch attributes for six co-occurring species of broadleaf evergreen trees in northern California'', Journal: Trees – Structure and Function, Volume 11, Number 3, Pages 169–175, January, 1997; Springer, Berlin / Heidelberg, ISSN 0931-1890

Canyon live oak gives functional habitat for many fauna by providing perching, nesting, resting, or foraging sites for numerous species of birds, and shade and cover for diverse other mammals. Young ''Q. chrysolepis'' is a readily available browse. Canyon live oak woodlands serve as excellent mountain lion habitat because of the large population of deer frequenting these areas. Many species forage on canyon live oak foliage including black-tailed jackrabbit, beaver, brush rabbit, red-backed vole, Sonoma chipmunk, cactus mouse, deer mouse, and porcupine. Pocket gophers often feed on the cambium of young canyon live oaks.

In southern California, ''Q. chrysolepis'' is the food plant of a small moth, '' Neocrania bifasciata''.

Allergenicity

The pollen of the canyon live oak is a severe allergen. Pollination occurs in spring.

Uses

The acorns are edible. Native Americans used them as a food staple after leaching the tannins. Its roasted seed is also used as a coffee substitute.

The wood is strong, being referred to as 'maul oak' by European-American settlers who employed it for sledgehammers and wedges. It is sometimes used in paneling and especially as firewood.

References

External links

*
*

{{Taxonbar, from=Q138446

chrysolepis
Trees of Northern America
Flora of California
Flora of the Klamath Mountains
Flora of the Sierra Nevada (United States)
Natural history of the California chaparral and woodlands
Natural history of the California Coast Ranges
Natural history of the Channel Islands of California
Natural history of the Peninsular Ranges
Natural history of the San Francisco Bay Area
Natural history of the Santa Monica Mountains
Natural history of the Transverse Ranges
Trees of mild maritime climate
Trees of Mediterranean climate
Plants described in 1854
Taxa named by Albert Kellogg
Garden plants of North America
Drought-tolerant trees
Ornamental trees
Oaks of Mexico