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You are here >1Up Info > Wildlife, Animals, and Plants > Plant Species > Shrub > Species: Quercus chrysolepis | Canyon Live Oak
 

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BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Quercus chrysolepis | Canyon Live Oak
GENERAL BOTANICAL CHARACTERISTICS : Canyon live oak is a rounded, spreading, sclerophyllous evergreen which grows as a large shrub or small-to-large tree [63,83,97]. Height commonly ranges from 15 to 70 feet (4.6-21.4 m), with an average maximum d.b.h. of 2.5 to 5.0 feet (0.8- 1.5 m) [72]. On exceptional sites, broad-crowned canyon live oaks can reach 100 feet (30.5 m) in height [45]. The tallest canyon live oak is measured at 106 feet (32 m) at 58.3 inches (148 cm) d.b.h., whereas the record trunk size is 128.5 inches (326 cm) d.b.h. at 72 feet (22 m) [8]. Shrublike growth forms often have multiple trunks but single-stemmed individuals are also common [59]. In relatively open stands, the dense canopy may reach nearly to the ground. However, in closed stands, crowns tend to be of smaller diameter and take up only the top one-third to one-half of the tree [72]. Canyon live oak is typically long-lived, and many plants are believed to grow to at least 250 or 300 years of age [72,97]. Undisturbed bark is smooth, scaly, and pale gray in color [63,72]. Furrows develop in stems greater than 3 inches (7.6 cm) in diameter, and the outer bark of older trunks develop variable strips [72]. The root system is typically deep [35], with roots frequently extending to at least 24 feet (7.3 m) beneath the soil surface [32]. The leathery, variable, oblong leaves of canyon live oak are green and glossy above, but golden-yellow below [45,72,83]. Leaf margins are usually smooth or entire but may be spiny-toothed, particularly when young. Leaves generally persist for at least 3 years [72]. Canyon live oak first flowers between 15 and 20 years of age. Male flowers are tawny catkins whereas female flowers are sparsely-flowered spikes. Both male and female flowers are borne on the same tree [91]. The oblong to ovoid acorns are covered with fuzzy golden scales [61,81]. Acorn size is variable, ranging from 1.0 to 3.0 inches (2.5-7.6 cm) in length [72]. The variety nana is primarily distinguished by its compact shrubby growth form. Leaves of this variety range from 0.8 to 1.6 inches (2-4 cm) in length [63]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : Both seed production and vegetative sprouting are important modes of regeneration in canyon live oak. Seed: Variable, ovate-to-ovoid acorns 1.0 to 3.0 inches (2.5-7.6 cm) in length are borne singly or in clusters [63,72]. Acorns of canyon live oak are relatively large [73] and can weigh up to 0.7 ounces (19 g) [3]. Cleaned acorns average approximately 150 per pound (330/kg) [66]. Seeds mature after two growing seasons and drop from the trees during the late summer or fall [13,41]. Prolific seed crops are produced at somewhat irregular intervals [71]. However, canyon live oak was found to have the highest mean annual production of five California oaks sampled. Approximately 19 percent of the individual canyon live oaks produced no acorns during the course of this study, whereas 43 percent produced acorns in 4 or more years. Good crops were consistently produced by this species during the 7-year period [13]. Some trees apparently produce acorns every year [91]. Acorn production by weight is often high, and yields of from 1,960 to 6,000 pounds per acre (2,195-5,200 kg/ha) have been reported [3,98]. Trees in dense stands or clumps generally produce fewer acorns than large, single trees. A single open-grown tree can produce up to 400 pounds (182 kg) of acorns annually [91]. Seed dispersal: Acorns are readily dispersed by gravity, and by many small birds and mammals. Squirrels cache acorns and are effective dispersal agents even though they consume many seeds [5]. The acorn woodpecker caches seed in trees, whereas the scrub jay hides acorns in the ground for later use [13]. Although most of these acorns are eaten, a few subsequently germinate. Germination: Germination of canyon live oak tends to be slow. Matsuda and McBride [52] observed 50 germination within a 35 day period under favorable laboratory conditons. Development may be particularly delayed at higher elevations. In California, acorns germinate from November through January at lower elevations, but germination may not occur at higher elevations until January or February [51,52]. Evidence suggests that cold stratification can enhance germination of canyon live oak [16], although exposure to cold is not necessary for good germination [51]. Germination appears to be inhibited by darkness [41]. Viable acorns can be harvested 1 1/2 to 2 months prior to normal ripening, but germinate only if the tip of the pericarp is removed before planting [16]. Results of germination tests are as follows [66]: germination test temperature F duration germination (cold strat. days) day night (days) capacity (%) 0 to 60 86 68 56 to 60 56 to 75 Seedling establishment: Acorns are vulnerable to bird, mammal, and insect predators. Animals may consume large numbers of acorns, with utilization approaching 100 percent where deer, pigs, or bear occur [5]. High acorn mortality has also been attributed to mold or rot. Acorn mortality has ranged from 3 to 77 percent under carefully controlled laboratory experiments [51], suggesting that high mortality does occur under natural conditions. In some areas, competition from grasses can completely eliminate seedling establishment except in particularly moist years. Seedling establishment is typically best beneath a forest canopy. Where good establishment occurs, seedlings may be dense and evenly distributed. Large numbers of canyon live oak seedlings accumulate in some stands [91]. Growth of seedlings is typically slow [55]. Vegetative regeneration: Canyon live oak typically sprouts vigorously from the stump or rootcrown after fire or mechanical disturbance [49,72,89,97]. The subsurface rootcrown often sprouts prolifically when the canopy is only "marginally defoliated" [59,72], and even seedlings are capable of sprouting after disturbance [49]. Young, vigorous plants generally sprout readily, although older, weakened trees may fail to sprout, or may produce only a few stool sprouts. Sprout growth can be rapid. Sprouts may reach 1 to 3 feet (0.5 to 1 m) during the first year of growth [91]. Four year old sprouts 3 to 6 feet (1-2 m) in height have been observed [60]. The number of sprouts per clump is reduced as resources are concentrated on the most vigorous individuals [91]. SITE CHARACTERISTICS : Canyon live oak occurs across a wide range of climatic and topoedaphic conditions [28,49]. It grows on steep, rocky, often exposed slopes or ridges, in narrow canyon bottoms, sheltered coves, rock crevices, dry washes, and arroyos [19,28,71,73,93]. Canyon live oak often occurs in pure stands on steep slopes or bouldery canyon bottoms [49], and in continuous bands above chaparral [60]. It occasionally forms dense thickets approximately 10 to 16 feet (3-5 m) in height [17]. Canyon live oak is particularly common on slopes of 55 percent or more [8]. Soils: California oaks grow well on a variety of well-drained soils including fine-grained, cobbly, or gravelly sandy loams, or poorly developed skeletal soils. Soil pH commonly ranges from 5.6 to 7.5 with depths of 20 to 40 inches (50-100 cm) [73]. Canyon live oak occurs on fine, gravelly, rocky, or gravelly-loamy soil, and sand [83,93], but best growth occurs on rich, moist soils of canyon bottoms [72]. Parent materials vary but include diorite and gabbro in the Siskiyou Mountains [100] and serpentine in parts of the Santa Ana Mountains of California [99]. In northwestern California, canyon live oak grows on soils derived from serpentine, peridotite, and sedimentary, meta-sedimentary, and granitic rock types [91]. It generally grows well on poorly developed soils derived from granitic, metamorphic, or sedimentary parent materials [49]. Climate: Canyon live oak grows in coastal areas that receive more than 110 inches (2,780 mm) of annual precipitation, as well as in interior mountains that receive less than 6 inches (150 mm) of precipitation annually. Mean summer temperatures range from 68 to 74 degrees F (20-23 deg C) in the north, to 70 to 77 degrees F (21-25 deg C) in the south. Winter temperatures average 37 to 41 degrees F (3-5 deg C) in the north, and 41 to 45 degrees F (5-7 deg C) in the south. Average growing season length ranges from 160 to 230 days [91]. Elevation: Canyon live oak grows from near sea level to 9,000 feet (2,740 m) [49]. Generalized elevational ranges are as follows [10,61,72,93,91]: from 5,300 to 8,500 feet (1,615-2,591 m) in AZ 1,000 to 5,000 feet (300-1,500 m) in northern Sierra, CA 2,500 to 9,000 feet (750-2,740 m) in southern Sierra, CA 4,100 to 6,300 feet (1,250-1,920 m) in eastern Mohave, CA 3,280 to 6,888 feet (1,000-2,100 m) in n. Baja CA, Mexico 1,600 to 5,000 feet (500-1,500 m) in southwestern OR SUCCESSIONAL STATUS : Canyon live oak is an important component of many early seral communities, primarily because of rapid, prolific sprouting. In the northern portion of its range, canyon live oak is prominent in early seral community on good sites, but it is eventually outcompeted and disappears from climax stands [91]. In many areas, canyon live oak is a primary colonizer on rocky crevices and talus piles [17,81]. Once established on these harsh sites, it generally persists for long periods of time [17]. This oak often dominates brushfields created by burning or logging, and although these brushfields develop soon after disturbance, they may persist for decades. Relatively long-lived brushfields made up of vigorous, shade-tolerant sprouters such as canyon live oak can slow the rate of forest succession by interfering with conifer regeneration [22]. Canyon live oak is long-lived, and shade-tolerant when young [72,97]. These attributes enhance its importance in a variety of later seral or climax communities. It commonly persists as a subordinate species in climax stands on dry, open forested sites. Canyon live oak occurs as a climax dominant on steep, rock-walled canyons [91]. In bigcone Douglas-fir-canyon live oak forests of southern California, disturbances such as fire can cause some internal shifts in species composition, but the community itself changes little [49]. Canyon live oak, although present in seral stages, appears to persist in climax or even postclimax stands. Bigcone Douglas-fir forests may be replaced by canyon live oak woodlands or live oak chaparral under a regime of frequent fires. A period of at least 40 to 70 years may be required for bigcone Douglas-fir to grow beyond 16 to 30 foot (5-9 m) tall stands of canyon live oak. It may take "many centuries" for bigcone Douglas-fir to again assume dominance after a relatively intense fire. In the absence of fire, bigcone Douglas-fir slowly grows above canyon live oak and eventually replaces it [55]. Canyon live oak is generally regarded as an important species in many fire-maintained disclimax chaparral communities of southern California [17]. Actual postfire stand turnover is often minimal because of the prolific sprouting ability of this plant. Oak typically grows from 3 to 10 feet (1-3 m) within 15 to 30 years after fire or other disturbance, and dense closed canopy stands 15 to 30 feet (5-10 m) in height develop within approximately 30 years [59]. Open canyon live oak woodlands are converted into live oak chaparral if burned at frequent intervals [37,49]. Although the growth form becomes much more shrublike, the species itself persists, and the community reverts to an oak woodland if it is subsequently protected from fire [49]. Tree-sized canyon live oaks are generally present only in areas which have not burned within 50 years [58]. SEASONAL DEVELOPMENT : Canyon live oak flowers from April to June [64,93]. Acorns mature after two seasons, with ripening time largely dependent on elevation and growing conditions [71,72]. Acorns generally ripen after mid-August, although some annual variation has been observed [71]. Immature acorns which have been damaged by wind, hail, rain, or insects begin to fall from the tree as early as May [56]. Ripe, undamaged acorns of canyon live oak are dispersed during the fall [41]. Individual leaves of this evergreen frequently remain on the tree for at least 3 years [72], with leaf fall generally occurring in early summer [59].

Related categories for Species: Quercus chrysolepis | Canyon Live Oak

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