Quercus kelloggii Newb.  

California black oak is a component of six forest cover types  (11). It is the prime constituent of California Black Oak  (Society of American Foresters Type 246) and a major component in  two others: Douglas-Fir-Tanoak-Pacific Madrone (Type 234) and  Pacific Ponderosa Pine-Douglas-Fir (Type 244). Black oak becomes  important in Sierra Nevada Mixed Conifer (Type 243) and Pacific  Ponderosa Pine (Type 245) after severe disturbance or fire. The  oak is a minor component in Canyon Live Oak (Type 249).

    The successional status of California black oak is not clear. It  has been implied that the species was climax because the type in  which it was a part represented a degree of mesophytism between  that of the chaparral and the conifer forest (7). The species was  also thought to be more a persistent subclimax than climax.

    California black oak, or its fossilized equivalent (Quercus  pseudolyrata), was much more widespread in past ages than  now. Fossil remains indicate that the species was abundant in  sedimentary deposits near Spokane and Ellensburg, WA, in the John  Day Valley and Blue Mountains of Oregon, and in northwestern  Nevada (6). These deposits date back to the Miocene epoch of 12  to 26 million years ago. Increasing aridity is the probable cause  for the smaller natural range of black oak today.

    The most common botanical associate of black oak is ponderosa pine  (Pinus ponderosa var. ponderosa). The two species  intermingle over vast acreages, except that black oak is found at  lower elevations, on sites too poor to support pine, and in  certain areas within the redwood region of California where pine  does not grow. Another exception is that this oak is rarely found  in Interior Ponderosa Pine (Type 237) (11). In California and  Oregon, therefore, where the natural ranges of the two species  coincide, ponderosa pine sites generally are fertile ground for  black oak. And black oak sites are almost always fertile ground  for ponderosa pine.

    At lower elevations, black oak often serves as a nurse tree to  conifers. Ponderosa pine, Douglas-fir (Pseudotsuga  menziesii), and incense-cedar (Libocedrus decurrens) seedlings  often become established beneath the sheltering crowns of large  black oaks while adjacent ground remains bare (2).

    A rule-of-thumb is that black oak never grows through a stand of  ponderosa pine but can grow through brush (9). Without  disturbance, black oak is eventually crowded out of the best  sites and remains only as scattered remnants in mixed-conifer  forests. Here it often exists on "islands" of soil or  terrain not favorable for natural regeneration of conifers.

    Black oak grows individually or in groves, some of which are quite  extensive. Usually each grove is of one age-class, the result of  sprouting after fire (34). Rarely does it exist as an understory,  especially beneath a closed canopy. The species is usually a  component of hardwood stands or of mixed hardwood and conifer  forests. Tanoak (Lithocarpus densiflorus) and Pacific  madrone (Arbutus menziesii) are the most common hardwood  associates of black oak. Other hardwood associates at lower  elevations are Oregon white oak (Quercus garryana), interior  live oak (Q. wislizenii), coast live oak (Q.  agrifolia), Engelmann oak (Q. engelmannii), and  blue oak (Q. douglasii). At higher elevations  Pacific dogwood (Cornus nuttallii), bigleaf maple (Acer  macrophyllum), California-laurel (Umbellularia  californica), and canyon live oak (Quercus chrysolepis)  intermix with California black oak.

    Besides ponderosa pine, conifer associates at low elevations are  knobcone pine (Pinus attenuata), Monterey pine (P. radiata),  Digger pine (P. sabiniana), and redwood (Sequoia  sempervirens). At intermediate elevations within the natural  range of California black oak are California white fir (Abies  concolor var. lowiana), grand fir (A. grandis),  incense-cedar, Coulter pine (Pinus coulteri), sugar  pine (P. lambertiana), giant sequoia (Sequoiadendron  giganteum), Douglas-fir, California torreya (Torreya  californica), and bigcone Douglas-fir (Pseudotsuga  macrocarpa). At higher elevations black oak intermingles with  western juniper (Juniperus occidentalis) and Jeffrey pine  (Pinus jeffreyi).

    Shrub associates include at least 30 species, some of the most  important of which are greenleaf manzanita (Arctostaphylos  patula), whiteleaf manzanita (A. viscida), deerbrush  (Ceanothus integerrimus), bear-clover (Chamaebatia  foliolosa), oceanspray (Holodiscus discolor), Brewer  oak (Quercus garryana var. breweri), Sierra  coffeeberry (Rhamnus rubra), Sierra gooseberry (Ribes  roezlii), and poison-oak (Toxicodendron diversilobum).  In parts of Shasta and Trinity Counties, and perhaps  elsewhere, black oak itself takes a shrub form. The stands so  formed usually are dense and tangled-ideal habitat for deer and  upland game.

    Except on the fringe of black oak's natural range, especially at  the lowermost elevations, most shrubs generally are not  competitive, nor particularly abundant over most of the forest  land where black oak grows. After heavy cutting or fire, however,  some of the more aggressive shrubs often compete strongly with  black oak sprouts.

    When compared with 15 of its most common shrub associates in the  Klamath Mountains of northern California, black oak ranked ninth  in need of soil moisture, third in demand on soil nutrients,  eighth in terms of tolerance, and first in rapidity of sprouting  (32). The species is able to withstand high moisture stress (37)  and to become established and grow well on harsh sites where few  other species are capable.

More info for the terms: competition, cover, frequency, litter, mast, presence, tree

California black oak is a critical species for wildlife. Oaks (Quercus spp.) may be the single most important genus used by wildlife for food and cover in California forests and rangelands [60,253], and California black oak occupies more total area in California than any other oak species [31]. Its acorns are the largest of the western oaks [27], and are heavily consumed by livestock, mule deer, feral pig, rodents, mountain quail, wild turkey, jays, and woodpeckers [87,139]. California black oak and mixed-oak woodlands are important wildlife habitat. In riparian oakwoods of the Central and North Coast Ranges, for example, California black oak and associated oaks form riparian corridors within agricultural areas. A night-camera survey in a mixed-oak riparian woodland in Napa County's wine country showed that many predators, including striped skunk, bobcat, coyote, gray fox, and mountain lion, used the oak woodland corridors extensively. Predator usage was significantly greater (P=0.03) in wide, undisturbed corridors compared to narrow or denuded corridors [99].

The leaves and berries of Pacific mistletoe, which commonly infects California black oak, are important foods for a variety of birds and small mammals (review by [76]).

Cattle make heavy use of California black oak for food and cover [180,212]. They browse California black oak leaves and stems, and forage for acorns on trees and on the ground [212]. California black oak-mixed oak woodlands are important rangelands [245]. A Blodgett Forest Research Station study of forage use by free-range cattle found consumption of California black oak peaked in June (17.8% of diet), with use extending to August (10.2% of diet) [113]. Cattle may consume much of the California black oak acorn crop in some years. To reduce competition for acorns between mule deer and cattle, Kie and Loft [114] recommend removing cattle from oak rangelands during acorn drop.

Mule deer: California black oak woodlands and forests provide mule deer (Columbian black-tailed deer) cover and habitat [118]. Mule deer browse California black oak [207,212], and acorns are important mule deer forage. Mule deer use of California black oak browse peaks in summer and is lowest in winter [131]. They rely on the acorns after acorn drop: California black oak acorns constitute an average of 50% of the fall and winter diets of Columbian black-tailed deer in high mast years [195]. Fawn survival rates generally increase or decrease with the size of California black oak acorn crops [42]. Mule deer eat the acorns from fall through spring. On the Tehama Deer Range of California, California black oak acorns constituted a mean of 27.8% of the October mule deer diet and 21% of the April diet [147]. California black oak acorns are especially important in early spring just before and during snowmelt [147], when new green forage is still scarce.

Other large mammals: American black bear use California black oak forest types heavily for spring, summer, and fall cover [42]. American black bears and northern raccoons eat California black oak acorns [139]. Ponderosa pine-California black oak forests provide habitat for mountain lions and other large predators [221]. Foothill oak woodlands with a California black oak component provide prime mountain lion hunting grounds [52].

Small mammals: Chipmunks and squirrels make heavy use of acorns (Quercus spp.) [139]. California black oak acorns comprise about 50% of the fall and winter diets of western gray squirrel during high mast years [195]. Plant communities with a substantial California black oak component are good habitat for rodents. California black oak and white fir are the principal tree species associated with northern flying squirrels in the San Bernardino Mountains, where the squirrels are at the southern edge of their range. On the Plumas National Forest, 37% of long-eared chipmunk, 54% of Townsend's chipmunk, 36% of yellow-pine chipmunk, and 50% of golden-mantled ground squirrel habitat use was on early seral conifer burns where the dominant vegetation was California black oak and mixed chaparral species [253]. California black oak provides cover for dusky-footed woodrats, a major prey item for California spotted owls [270].

Birds: Many seed predators consume California black oak acorns, and California black oak is a preferred foraging substrate for many birds [5,166]. Acorn-consuming songbirds include blackbirds, chickadees, crows, goldfinches, larks, Clark's nutcrackers, nuthatches, sapsuckers, and thrashers [139]. California black oak acorns form a majority of the acorn woodpecker's diet in some areas [137,205]. The acorns are important in the fall diet of band-tailed pigeons [173,223], comprising 3.2% of their September diet and 7.7% of their November diet [147]. All of 68 bird species observed in oak woodlands of the Tehachapi Mountains of California used California black oak for part of their foraging activities. The acorn woodpecker, the northern oriole, and the Nashville warbler showed greatest preference for California black oak [29]. In a mixed-conifer forest on the Blodgett Research Station, red-breasted and chestnut-back chickadees foraged on California black oak significantly more than expected (P<0.05) based upon California black oak's frequency [1,39]. A Blodgett Forest Research Station study of bark-foraging birds showed the pileated woodpecker made high use of California black oak branches while hawking [166]. As a guild, insect-gleaning birds preferred (preference value L=0.05) California black oak more than expected based on availability [5]. Morrison and others [39] express concern that managing only for pines in mixed-conifer forests may reduce population densities of chickadees and other gleaning birds that depend on California black oak and other hardwoods for food and cover.

Protected animals: California black oak woodlands are important habitat for several rare and threatened species. California black oak provides diversity and nesting and other cover for California spotted owls [164,228,265] and flammulated owls [146]. A Sierra National Forest-Sequoia Kings Canyon National Park study showed California spotted owls in mixed-oak woodlands nested in California black oaks more often than expected (P<0.05) based on California black oak's relative abundance [175]. In a study of Sierra Nevada fisher populations, fishers in mixed-conifer-California black oak habitat had smaller home ranges than fishers in Sierra lodgepole pine (Pinus contorta var. murrayana) or Jeffrey pine habitats. The authors suggested that fisher home range requirements were smaller in mixed forest because California black oak and other montane oaks increased habitat quality [270,276]. Stewart and others [237] discuss habitat needs of sensitive-listed southern California herptiles in mixed-conifer forests with a California black oak component.

Arthropods: The bole and limbs of California black oak are habitat for many arthropods species. Some of these arthropods are important to gleaning and other insectivorous birds [39]. Schowalter and Zhang [217] provide a compilation of arthropod family assemblages found on branches of California black oak and associated woody species on the Teakettle Experimental Forest.

Tree cavities filled with rainwater or detritus form unique habitat for aquatic- or detritus-based invertebrate communities. Mosquitoes are among the insects that live in rain-filled California black oak cavities during the larval stage. Some invertebrates are largely or entirely restricted to cavities in California black and other oaks during a portion of their life cycle. Woodard and others [274] detail invertebrate species presence and food chains in cavities of California black and other oaks in Mendocino County, California.

Palatability/nutritional value: California black oak browse is highly palatable to cattle and mule deer, but is less valuable for other ungulates [212]:

California black oak acorns have a high concentration of lipids [149]. They provide little nutrition for herbivore growth and bone-building but are an excellent source of energy due to the high fat content [212]. California black oak leaves may provide the highest food value of all the western oak browse for fattening cattle [136].

California black oak acorns are highly palatable to livestock and mule deer. In a study in the Cuyamaca Mountains of southwestern California, mule deer preferred California black oak acorns over any other forage. Mule deer would search through forest litter for acorns even during spring, when new, palatable sprouts and herbs were readily available [37]. Mean nutritional values of California black oak acorns are given below (review by [59]):

Scrivner and others [218] provide a mineral analysis of California black oak acorns collected on the Hopland Field Station.

Cover value: Wildlife use California black oak heavily for cover. California black oak provides valuable shade for livestock and wildlife during the hot summer months [59]. Cavities in California black oak provide den or nest sites for owls, woodpeckers, tree squirrels, and American black bears [60,271]. Cavity nesters also use oracle oak [271]. For further information, see Importance to Livestock and Wildlife.

Fire is black oak's worst enemy. Crown  fires kill trees of all ages and ground fires are often fatal.  Only a little radiative heat kills the cambium and only a small  amount of flame along the trunk leaves long vertical wounds. Bark  thickness on mature trees varies from 2 to 5 cm (1 to 2 in), but  even the thickest bark provides little insulation to fire. Scars  from burning can become a point of entry for fungi. On larger  trees, repeated fires often enlarge old scars, sometimes toppling  the tree. Fluctuations in weather also cause injury. Heavy, wet  snow breaks branches and stems, particularly at forks, and sudden  high temperatures following cool wet weather severely injure  leaves (25).

    California black oak is especially susceptible to fungi. Heart rot  of the bole and large limbs of living trees, caused mainly by two  pathogens, Inonotus dryophilus and Laetiporus  sulphureus, is the principal damage (24). These rots enter  the tree through broken branches or open wounds resulting from  fire or logging. Both fungi often reduce the bole and large limbs  of older, decadent trees to mere shells. The hedgehog fungus (Hydnum  erinaceus) also is found in the heartwood of living trees and  Polyporus adustus in the sapwood, though neither is  prevalent.

    By the time a natural black oak stand is 85 years old, the  proportion of infected trees begins to increase rapidly. Almost  40 percent of trees 110 to 120 years old show incipient heart rot  (21). Rotation age of stands grown for wood products could be  influenced by this incidence-age relationship.

    Another serious pathogen, Armillaria mellea, causes decay  of the roots and butt of older decadent black oak. Sometimes it  weakens the root system so much that the tree topples over on a  perfectly calm, still day (36). This pathogen is indigenous in  black oak, but younger vigorous trees do not seem to be affected  by it.

    A comparatively recent damaging agent to black oak in the San  Bernardino Mountains of southern California is air pollution.  Although the oak appears less susceptible to air pollution damage  than associated conifers, radial growth has decreased in some  trees (12). Where high ambient oxidant air pollution levels are  chronic, damage to California black oak is expected to be  significant (26).

    One virulent pathogen that black oak escapes, and indeed is  resistant to, is Heterobasidion annosum (14). For this  reason, California black oak is being planted in numerous  infection centers in southern California forests where conifers  are dead or dying.

    California black oak is prone to several leaf diseases including  the oak leaf fungus (Septoria quercicola), oak  anthracnose (Gnomonia veneta), powdery mildews (Microsphaera  and Sphaerotheca spp.), a leaf blister fungus (Taphrina  caerulescens), a leaf rust (Cronartium spp.),  and true mistletoe (Phoradendron villosum subsp. villosum).  Damage from each of these pests has not been determined but  loss of growth increment probably is minor.

    Animal damage to black oak is mostly from browsing. Foliage is  eaten during all seasons, but especially in spring when new  growth is tender and in winter when twigs are eaten. Deer eat  acorns, seedlings, sprouts, and foliage. Even in midsummer, newly  germinated seedlings with acorns attached often are consumed (8).  Occasionally, browsing is fatal. In Mendocino County, CA, for  example, a deer population of 1/2.4 ha (1/6 acres) almost  eliminated oak over large areas of the Coast Range. Cattle also  browse black oak, but in national forests, at least, their  numbers are declining.

    Many insects derive sustenance from black oak. The damage is  usually secondary, reducing growth but seldom killing trees.  Among sucking insects, the pit scales (Asterolecanium minus  and A. quercicola) have the greatest potential for  damage (4). The most destructive insect, however, is probably the  carpenterworm (Prionoxystus robiniae), whose larvae mine  the wood of trunk and limbs and cause injuries that appear later  as defects in lumber (16).

    Other insects are capable of heavy damage, especially when  infestations become epidemic. The Pacific oak twig girdler (Agrilus  angelicus) is the most damaging insect to oak in southern  California during drought years (4). In northern California, the  California oakworm (Phryganidia californica) is noted for  defoliating trees. So is the fruit-tree leafroller (Archips  argyrospila) which, in 1968, caused heavy damage throughout a  wide area in the Sacramento River drainage.

Several attributes qualify the wood of California black oak for  commercial use: attractive grain and figure for paneling and  furniture, hardness and finishing qualities for flooring, and  strength properties for pallets, industrial flooring, and other  uses (19). The forks of open-grown black oaks were put to good  use in the 1870-80's in Mendocino County.

    Those of specific dimensions were used as "naturally  assembled" ship keels and ribs. Wood products currently  produced are high grade lumber and pallets, industrial timbers,  sawdust for mulching, and bulk and prepackaged firewood. The wood  is prized for fuelwood and in some areas unrestricted cutting is  eliminating oak stands.

    Although not presently utilized, black oak acorns, high in edible  oils, are a potential source for thousands of tons of human food  (38).