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California oak woodland is a
plant community
A plant community is a collection or association of plant species within a designated geographical unit, which forms a relatively uniform patch, distinguishable from neighboring patches of different vegetation types. The components of each plant ...
found throughout the
California chaparral and woodlands ecoregion
An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of ...
of
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
and northwestern
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
in
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
. Oak woodland is widespread at lower elevations in
coastal California
Coastal California, also known as the California Coastline and the Golden Coast, refers to the coastal regions of the U.S. state of California. The term is not primarily geographical as it also describes an area distinguished by cultural, economic ...
; in interior valleys of the
Coast Ranges
The Pacific Coast Ranges (officially gazetted as the Pacific Mountain System in the United States) are the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico. Although th ...
,
Transverse Ranges
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa ...
and
Peninsular Ranges; and in a ring around the
California Central Valley grasslands. The dominant trees are oaks, interspersed with other broadleaf and
coniferous trees, with an understory of
grasses
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns ...
, herbs,
geophyte
A storage organ is a part of a plant specifically modified for storage of energy
(generally in the form of carbohydrates) or water. Storage organs often grow underground, where they are better protected from attack by herbivores. Plants that have ...
s, and
California native plants.
Oak savanna
An oak savanna is a type of savanna—or lightly forested grassland—where oaks (''Quercus ''spp.) are the dominant trees. The terms "oakery" or "woodlands" are also used commonly, though the former is more prevalent when referencing the Medite ...
s occur where the oaks are more widely spaced due a combination of lack of available moisture, and
low-intensity frequent fires
A fire regime is the pattern, frequency, and intensity of the bushfires and wildfires that prevail in an area over long periods of time. It is an integral part of fire ecology, and renewal for certain types of ecosystems. A fire regime describes th ...
.
The oak woodlands of
Southern California
Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban a ...
and coastal
Northern California are dominated by coast live oak (''
Quercus agrifolia
''Quercus agrifolia'', the California live oak, or coast live oak, is a highly variable, often evergreen oak tree, a type of live oak, native to the California Floristic Province. It may be shrubby, depending on age and growing location, but is ...
''), but also include valley oak (
''Q. lobata''), California black oak (
''Q. kelloggii''), canyon live oak (
''Q. chrysolepis''), and other California oaks. The foothill oak woodlands around the
Central Valley are dominated by blue oak (
''Q. douglasii'') and gray pine (''
Pinus sabiniana'').
California oak-woodland communities
* Oregon oak woodland is found in Northern California's
Klamath-Siskiyou
The Klamath Mountains ecoregion of Oregon and California lies inland and north of the Coast Range ecoregion, extending from the Umpqua River in the north to the Sacramento Valley in the south. It encompasses the highly dissected ridges, foothi ...
,
Northern Coast Ranges
The Coast Ranges of California span from Del Norte or Humboldt County, California, south to Santa Barbara County. The other three coastal California mountain ranges are the Transverse Ranges, Peninsular Ranges and the Klamath Mountains.
P ...
, and southern
Cascade Range. These woodlands are composed primarily of Oregon oak (
''Q. garryana''), interior live oak (''
Q. wislizeni''), and coast live oak, together with California black oak, canyon live oak, blue oak, Pacific madrone (''
Arbutus menziesii''), California bay (''
Umbellularia californica
''Umbellularia californica'' is a large hardwood tree native to coastal forests and the Sierra foothills of California, and to coastal forests extending into Oregon. It is endemic to the California Floristic Province. It is the sole species in th ...
''), incense cedar (''
Calocedrus decurrens
''Calocedrus decurrens'', with the common names incense cedar and California incense-cedar (syn. ''Libocedrus decurrens'' Torr.), is a species of coniferous tree native to western North America. It is the most widely known species in the genus, ...
''), coast Douglas fir (''
Pseudotsuga menziesii
The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...
''
var.'' menziesii''), Coulter Pine and ponderosa Pine (''
Pinus ponderosa'').
* Blue oak woodland is found in the inner coast ranges and the Sierra Nevada foothills, surrounding the Central Valley. It forms "one of the largest ecosystems in California".
Primary species are blue oak (
''Q. douglasii'') and interior live oak (or on west facing slopes facing the exterior ranges, particularly in Contra Costa and Alameda counties, coast live oak takes interior live oak's place), together with valley oak, canyon live oak, California scrub oak (''
Q. berberidifolia''), gray pine, California buckeye (''
Aesculus californica
''Aesculus californica'', commonly known as the California buckeye or California horse-chestnut, is a species of buckeye native to California and southwestern Oregon.
Description
It is a large deciduous shrub or small tree, up to tall, w ...
''), and western redbud (''
Cercis occidentalis
''Cercis occidentalis'', the western redbud or California redbud (syn. ''Cercis orbiculata'' — Greene), is a small tree or shrub in the legume family, Fabaceae. It is found across the American Southwest, from California to Utah and Arizona.
I ...
'').
* Coast live oak woodland is widespread in northern and southern California, and is dominated by coast live oak (
''Q. agrifolia''), together with California buckeye, Pacific madrone, California bay, and California walnut (''
Juglans californica
''Juglans californica'', the California black walnut, also called the California walnut, or the Southern California black walnut, is a large shrub or small tree (about 20-49 feet tall) of the walnut family, Juglandaceae, endemic to Southern Calif ...
'').
*Interior live oak woodland is found in north and south mountain ranges of California. It is dominant by interior live oaks(''Q. wislizeni),'' blue oaks, foothill pine and shrubs in common with blue oak woodland.
* Valley oak woodland is found in the interior valleys of northern, central and southern California, and is dominated by valley oak (
''Q. lobata'') and coast live oak, together with gray pine and Coulter pine (''
Pinus coulteri
The Coulter pine or big-cone pine, ''Pinus coulteri'', is a native of the coastal mountains of Southern California in the United States and northern Baja California in Mexico. Isolated groves are found as far north as Clearlake, California on the ...
'').
* Island oak woodland is found on the
California Channel Islands
The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. The four Northern Channel Islands are part of the Transverse Ranges geologic province, and ...
, and is made up primarily of island oak (''
Q. tomentella'') and coast live oak, together with canyon live oak, MacDonald scrub oak (''Q. berberidifolia'') hybridized with valley or other oaks), Catalina ironwood (''
Lyonothamnus floribundus
''Lyonothamnus'' is a monotypic genus of trees in the rose family containing the single living species ''Lyonothamnus floribundus'', which is known by the common name Catalina ironwood, and the subspecies ''L. f.'' ssp. ''aspleniifolius'' and '' ...
''), and
bishop pine
''Pinus muricata'', the bishop pine, is a pine with a very restricted range: mostly in California, including several offshore Channel Islands, and a few locations in Baja California, Mexico. It is always on or near the coast.
In San Luis Obispo ...
(''Pinus muricata'').
* Engelmann oak woodland is found in a few locations in the northern
Peninsular Ranges of
Southern California
Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban a ...
, including the
Santa Rosa Plateau
The Santa Rosa Plateau is an upland plateau and southeastern extension of the Santa Ana Mountains in Riverside County, southern California. It is bounded by the rapidly urbanizing Inland Empire cities of Murrieta and Temecula to the northeast an ...
and
San Gabriel Mountains foothills. It consists mostly of Engelmann oak (''
Q. engelmannii'') together with coast live oak.
Status and future of California oak woodlands
Blue oak woodlands cover about of the state, and of this area about 79%, or , shows no evidence of past cutting of trees.
Recent research by the
University of Arkansas
The University of Arkansas (U of A, UArk, or UA) is a public land-grant research university in Fayetteville, Arkansas. It is the flagship campus of the University of Arkansas System and the largest university in the state. Founded as Arkansas ...
Tree-Ring Laboratory has studied several unlogged stands of blue oak woodlands, and suggests that the state may harbor over of such
old growth forest
An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological feature ...
s. This would make California's oak woodlands some of the most extensive old growth forests left in the state. However, most oaks of full tree size are more than one hundred years old, and few saplings are ever produced, because cattle often tear the plants to pieces.
The Oaks 2040 survey estimates that of California oak woodlands are seriously threatened by 2040 as a
burgeoning state population makes ever more use of the wildland. This comprehensive survey includes oak woodland maps and inventory data for the ten oak types found in California. By evaluating this new information against current State of California economic growth projections, the location and extent of oak woodlands most at risk of development are identified.
Management practices, such as the
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
(or the lack thereof) can lower
soil fertility and nutrient level. A study performed by the
University of California, Davis
The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The inst ...
found that the prominent presence of oak trees in California oak woodlands creates areas of soil that are optimal for new growth.
The
Bureau of Land Management partnered with the California Biodiversity Council to carry out the Agreement on Biological Diversity, started in 1991, to protect and expand the following oakland wood areas:
King Range National Conservation Area
The King Range is a mountain range of the Outer Northern California Coast Ranges System, located entirely within Humboldt County on the North Coast of California.
Geography
Much of the mountain range's area is protected within the King Range N ...
, Cache Creek Management Area,
Yuba River
The Yuba River is a tributary of the Feather River in the Sierra Nevada and eastern Sacramento Valley, in the U.S. state of California. The main stem of the river is about long, and its headwaters are split into three major forks. The Yuba Rive ...
Watershed in Inimim Forest, Consumes River Preserve, and
Fort Ord
Fort Ord is a former United States Army post on Monterey Bay of the Pacific Ocean coast in California, which closed in 1994 due to Base Realignment and Closure (BRAC) action. Most of the fort's land now makes up the Fort Ord National Monument, ...
. The methods used to ensure a healthy future for the California oak woodlands include maintenance and restoration of
old-growth forests
An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological featur ...
,
watershed management Watershed management is the study of the relevant characteristics of a watershed aimed at the sustainable distribution of its resources and the process of creating and implementing plans, programs and projects to sustain and enhance watershed fu ...
and improvement, protection of
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
, protection of wildlife species that have cultural and environmental value to the area, restoration of
valley oaks, and the habitat maintenance of “special status botanical species” and select endangered species.
Examples of occurrence
The headwaters area of
Yulupa Creek
Yulupa Creek is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed March 10, 2011 southeast-flowing perennial stream that rises on the southeastern flanks of the northern Sonoma Mountains ...
in
Annadel State Park
Trione-Annadel State Park is a state park of California in the United States. It is situated at the northern edge of Sonoma Valley and is adjacent to Spring Lake Regional Park in Santa Rosa. It offers many recreational activities within its prop ...
is cited as one of the best examples of California oak woodlands. Much of this woodland is a relatively pristine
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
with considerable
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
. An unusual characteristic of this Annadel forest is the high content of undisturbed
prehistoric bunch grass
Tussock grasses or bunch grasses are a group of grass species in the family Poaceae. They usually grow as singular plants in clumps, tufts, hummocks, or bunches, rather than forming a sod or lawn, in meadows, grasslands, and prairies. As perennia ...
understory
In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abo ...
, testifying to the absence of historic
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
or other
agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...
.
The
Morro Bay
Morro Bay (''Morro'', Spanish for "Hill") is a seaside city in San Luis Obispo County, California. Located on the Central Coast of California, the city population was 10,757 as of the 2020 census, up from 10,234 at the 2010 census. The town ...
watershed, located in Northern California, is an example of a coast live oak ecosystem. This sub-category of California oak woodland consists primarily of coast wild oak and are predominantly found in coastal regions, but can extend to foothill ecosystems.
Ecology of California oak woodlands
The composition and characteristics of California oak woodlands varies across the state, but are defined by three main oak species throughout coastal regions:
coastal live oak,
Englemann oak, and
Oregon white oak
''Quercus garryana'' is an oak tree species of the Pacific Northwest, with a range stretching from southern California to southwestern British Columbia. It is commonly known as the Oregon white oak or Oregon oak or, in Canada, the Garry oak. It ...
.
The concentration of each of these oak species correlates with the location of the woodland throughout California.
In southern and central areas, the predominant oak species is coastal live oak which grow on coastal valleys and foothills. In drier regions within this range, coastal wild oak is associated with
foothill pine,
valley oak and
blue oak; whereas wetter areas are defined by
tanoak
''Notholithocarpus densiflorus'', commonly known as the tanoak or tanbark-oak, is a broadleaf tree in the family Fagaceae, and the type species of the genus ''Notholithocarpus''. It is native to the far western United States, particularly Oregon ...
,
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 that is found in Mexico and in the western United States, notably in the California Coast Ranges. This ...
and
California bay. Coastal live oak woodland found in Southern California is associated with valley oak similar to drier northern sites, but also sees
interior live oak
''Quercus wislizeni'', known by the common name interior live oak, is an evergreen oak, highly variable and often shrubby, found in many areas of California in the United States continuing south into northern Baja California in Mexico. It genera ...
,
Coulter pine
The Coulter pine or big-cone pine, ''Pinus coulteri'', is a native of the coastal mountains of Southern California in the United States and northern Baja California in Mexico. Isolated groves are found as far north as Clearlake, California on the ...
and
California black walnut.
Outside of the southern ranges of coastal wild oak are small areas of oak woodland characterized by Englemann oak. These sites can coincide with coastal live oak, however they can also occur as stands composed almost entirely of Englemann oak.
Northern, wetter regions of California are populated with oak woodlands formed from Oregon white oak. These woodlands are associated interior live oak and canyon live oak similar to coastal live oak woodlands, but differ with
Pacific madrone
''Arbutus menziesii'' or Pacific madrone (commonly madrone or madrona in the United States and arbutus in Canada), is a species of broadleaf evergreen tree in the family Ericaceae, native to the western coastal areas of North America, from Br ...
and
California black oak.
The variety of
canopy
Canopy may refer to:
Plants
* Canopy (biology), aboveground portion of plant community or crop (including forests)
* Canopy (grape), aboveground portion of grapes
Religion and ceremonies
* Baldachin or canopy of state, typically placed over an ...
density which results from the diversity of tree species found in different woodland regions causes a wide range of understory grass and shrub density, and plant type. An example of this can be seen by the commonality of annual grasses in open woodlands, a phenomenon that is not seen in dense woodland areas.
All three oak species which characterize California oak woodlands can be defined as "long-lived, slow-growing trees."
The frequent fires seen within the region have resulted in species such as coastal live oak and Englemann oak (which grow in drier, more fire prone regions) to have developed a resistance to low-intensity fires. This resiliency has resulted in coastal live oak emerging as the predominant species in cleared regions, as the trees have higher
fitness to survive compared to less resistant, deciduous oaks. The same cannot be said for Oregon white oak, which populate traditionally wetter, less fire-prone regions, resulting in the trees having little built-up fire resistance. Because of the lack of fires in these northern regions, white oaks can have the threat of being outgrown by
conifers growing in the understory.
California oak woodland habitats contain some of the most wildlife in California. More than half of the species of terrestrial vertebrates in California are found in oak woodlands. This includes more than 120 species of mammals, 147 species of birds, and 60 species of amphibians or reptiles. The most diversity occurs when there is both multiple levels of vegetation heights and varied spacing between vegetation to create complex habitat structure both vertically and horizontally because there are more places for species that live in different layers of the vegetation.
Among these species, the
California quail
The California quail (''Callipepla californica''), also known as the California valley quail or Valley quail, is a small ground-dwelling bird in the New World quail family. These birds have a curving crest or '' plume'', made of six feathers, tha ...
(''Callipepla californicus''),
Beechey ground squirrels (''Spermophilus beecheyi''),
Botta pocket gopher (''Thomomys bottae mewa''),
Audubon cottontail (''Sylvilagus audubonii vallicola''), deer (''Odocoileus'' spp),
bobcat (''Lynx rufus californicus''),
coyote (''Canis latrans'') and the
Pacific rattlesnake
''Crotalus oreganus'', commonly known as the (northern) Pacific rattlesnake, Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. . is a venomous pit viper species found in western North ...
(''Crotalus viridis oreganus'') can commonly be found in California oak woodlands.
Aspects of the California oak woodland that are important for wildlife of these habitats are habitat corridors, snags and downed wood.
Natural vegetation create habitat corridors that connect the patches of habitat that host species. Habitat corridors provide protection and food for animals that migrate between patches such as deer, mountain lions, bobcats, or gray foxes.
Snags are the standing wood that is left when trees die and are home to wood-eating insects that are food for animals such as birds. Snags provide temporary refuge for small birds, bats, swallows, salamanders, and lizards. Similarly, downed wood provide refuge for animals that require moist areas, such as amphibians, cover for nesting of multiple species of birds, and areas for dens for larger snags.
See also
*
California chaparral and woodlands
*
Oak savanna
An oak savanna is a type of savanna—or lightly forested grassland—where oaks (''Quercus ''spp.) are the dominant trees. The terms "oakery" or "woodlands" are also used commonly, though the former is more prevalent when referencing the Medite ...
*
Cedar hemlock douglas-fir forest
Cedar may refer to:
Trees and plants
*''Cedrus'', common English name cedar, an Old-World genus of coniferous trees in the plant family Pinaceae
*Cedar (plant), a list of trees and plants known as cedar
Places United States
* Cedar, Arizona
* ...
*
California native plants
*
Blue Oak Ranch Reserve
The Blue Oak Ranch Reserve, a unit of the University of California Natural Reserve System, is an ecological reserve and biological field station in Santa Clara County, California. It is located on in the Diablo Range, northwest of Mount Hamilt ...
*
Dehesa
A ''dehesa'' () is a multifunctional, agrosylvopastoral system (a type of agroforestry) and cultural landscape of southern and central Spain and southern Portugal; in Portugal, it is known as a ''montado''. Its name comes from the Latin 'defens ...
, a type of managed oak ecosystem in Spain
References
{{reflist
General bibliography
* Dallman, Peter R. (1998). ''Plant Life in the World's Mediterranean Climates.'' California Native Plant Society–University of California Press; Berkeley.
* Gaman, Tom and Firman, Jeffrey (2006). ''Oaks 2040: The Status and Future of Oaks in California.'' Published by the California Oak Foundation, Oakland.
* Pavlik, Bruce M., Pamela C. Muick, Sharon G. Johnson, and Marjorie Popper (1991). ''Oaks of California.'' Cachuma Press and the California Oak Foundation;
Los Olivos, California
Los Olivos (; Spanish language, Spanish for "the olive trees") is an unincorporated area, unincorporated community in the Santa Ynez Valley of Santa Barbara County, California, United States. Tourism is popular in this rural area which is an ag ...
.
* Schoenherr, Allan A. (1992). ''
A Natural History of California
Allan A. Schoenherr (February 6, 1937 – May 31, 2021) was a Californian author, ecologist, and naturalist. He is the author of the widely used reference book, '' A Natural History of California''.
He received his PhD in zoology at Arizona Stat ...
.'' University of California Press; Berkeley.
External links
Californiaoaks.org , Oaks 2040: The Status and Future of Oaks in CaliforniaUCanr.org , University of California Oak Woodland Management Program
California chaparral and woodlands
Plant communities of California
*
*Oak
*Oak
*Oak
C