BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus agrifolia | Coast Live Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Coast live oak is a native, drought-resistant, evergreen tree.  It is
typically from 20 to 40 feet (6-12 m) tall, occasionally reaching up to
80 feet (24 m) in height.  Trees usually range from 1 to 4 feet (0.3-1.2
m) in d.b.h.  Open-grown crowns are broad and dense, with foliage often
reaching the ground.  Trunks are usually short, forking into large,
wide-spreading branches.  Trees in dense stands have irregular crowns
and few lower branches.  The bark of young trees is smooth, developing
deep furrows with age.  The inner bark and cork layers are thick
[22,67].  The root system is composed of a deep taproot, usually
nonfunctional in large trees; several deep main roots tapping
groundwater; extensive horizontal root branches; and surface-feeding
roots [19,66].  Coast live oak stands are typically from 40 to 110 years
of age [22].  Individual trees may live over 250 years [67].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Flowering of coast live oak is triggered by warm temperature.  This is
in contrast to many other black oaks, which flower in response to
photoperiod [85].  Trees are wind pollinated.  Information on the age of
sexual maturity and maximum production of acorns is lacking.  Coast live
oak retains its acorns longer than other California oaks.  Most of its
acorns are dropped in fall, but some remain attached to trees until
spring.  This is an adaptive advantage because these acorns are less
likely to be consumed by ground-dwelling seed predators.  Animals such
as squirrels, magpie, and scrub jay, however, consume tree-borne acorns.
Acorns fall beneath the parent plant or are disseminated by various
birds and rodents.  Seed-caching animals such as scrub jay and
California ground squirrel are important to species survival, as acorns
buried by these animals are most likely to develop into seedlings [15].
Coast live oak is the only black oak in California whose acorns develop
in 1 year [10,67].  There is no dormancy requirement, and acorns
germinate 15 to 50 days after falling [12,32,55].  Reports of seed
viability vary.  Griffin [32] found 100 percent viability of acorns
collected in Carmel Valley, while Mirov and Kraebel [55] reported 73
percent germination in acorns collected in Berkeley.  Acorns with low
moisture content show higher rates of germination and produce taller
seedlings than do acorns with high moisture content, but unviable seed
is not a serious problem for this species [41,59].  Predation of fallen
acorns, however, is very high, and loss of potential trees is
considerable.  Acorn predators may consume 100 percent of a year's mast.
Acorn predation and loss of seedlings to herbivory have been cited as
the primary cause of current recruitment failure in southern California
populations of coast live oak [59].

Seedling survival rates are low.  At sites on the Central and South
Coast ranges, the current sapling-to-tree ratios are 1:3 or worse [57].
Seedling top-growth is slow under natural conditions, with early
development concentrated on rapid, early root growth [49].  Black-tailed
deer cause considerable mortality of young trees.  Griffin [32] found
seedlings on the most favorable sites at the Hastings Natural History
Reservation of Carmel Valley required a minimum of 20 years to grow
above the browse line.  Livestock also limit recruitment.  Natural
establishment of coast live oak resumed in Solstice Canyon Park in the
Santa Monica Mountains once cattle were removed [64].  Mortality also
results from root hebivory by pocket gopher and feral pig, and from
drought [15,63].  At the Hastings Natural History Reservation, survival
of 2-year-old seedlings protected from herbivory was 69 percent.  By the
fourth year, however, 100 percent of these seedlings had succumbed to
drought [32].  Recruitment is best among germinants growing in shade.
Eighty percent of seedlings found on sites in the Santa Ynez Valley of
Santa Barbara County were growing under purple sage (Salvia leucophylla)
or California sagebrush (Artemisia californica).  Another 15 percent
were under mature coast live oak.  Mortality due to herbivory was
considerably higher among seedlings under parent trees [13].  Under
ideal conditions, coast live oak is capable of rapid growth.  Nursery
seedlings have attained heights of 5 to 8 feet (15.2-24.4 m) in 2 years
[81].

Vegetative:  Coast live oak sprouts from the root crown and trunk
following cutting or burning [22,66,67].


SITE CHARACTERISTICS : 
Coast live oak occurs in a mediterranean climate, characterized by mild,
wet winters and hot, dry summers.  Climate severity is modified near the
coast, where trees receive more annual precipitation than do inland
populations [22].  Trees generally occur on mesic sites such as north
slopes, alluvial terraces, and canyon bottoms [11].  In riparian areas,
coast live oak occurs in swales or on upper banks [24,51].

Soil textures vary with site.  Low-elevation coastal populations of
coast live oak generally grow in loam, while higher elevation coastal
populations are associated with shaley clay-loam soil.  Inland
populations are found in sandy soil [22].  Trees on the southern
California islands grow in clay or clayey loam [18].  Coast live oak
will tolerate serpentine soils [27].

The elevational range for northern populations of coast live oak is sea
level to 3,000 feet (914 m) and for southern populations, sea level to
5,000 feet (1,524 m).

Associated overstory species not previously mentioned include tanoak
(Lithocarpus densiflora), birchleaf mountain-mahogany (Cerocarpus
betuloides), Monterey pine (Pinus radiata), and California boxelder
(Acer negundo ssp. californicum) [1,9,14,26,53].

Understory associates:  Common shrub associates include California
blackberry (Rubus ursinus), poison-oak (Toxicodendron diversilobum),
ocean spray (Holodiscus discolor), coffeeberry (Rhamnus californica),
toyon (Heteromeles arbutifolia), chamise (Adenostoma fasciculatum),
California scrub oak (Quercus dumosa), manzanita (Arctostaphylos spp.),
California wild grape (Vitis californica), California sagebrush, and
jimbush ceanothus (Ceanothus sorediatus).  Herbaceous associates include
black sage, purple sage, brakenfern (Pteridium aquilinum), California
buckwheat (Eriogonum fasciculatum), brome (Bromus spp.), wild oat (Avena
fatua), Mediterranean barley (Criteston marinum spp.  gussoneanum),
smallflower melicgrass (Melica californica), gland cinquefoil
(Potentilla glandulosa), and common yarrow (Achillea millefolium)
[1,19,29,30,70].

Micorrhizal associates:  Coast live oak is commonly infected with
Dothiorelli querci and Phytophthora cinnamomi [82].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Coast live oak is tolerant of shade throughout its life [67].  Its
successional status varies.  Where their ranges overlap, deciduous trees
such as blue and California black oaks are seral to coast live oak, and
coast live oak represents the climax stage of coastal oak woodlands [6].
McBride [50] , however, reported that coast live oak is seral to the
evergreen California bay in some areas of coastal northern California.
In mixed evergreen forest, the coast live oak phase is seral to a
coniferous element that was removed by logging or fire.  On steep slopes
or poor sites within this belt, coast live oak represents a topographic
or edaphic climax [4].



SEASONAL DEVELOPMENT : 
The seasonal development of coast live oak is as follows:

     growth begins:  February [56]
     catkins emerge:  March - April [56,58]
     leaves emerge:  February - April [56,58]
     old leaves shed: after new leaf emergence in spring [67]
     acorns ripen:  September - October [55]
     damaged acorns aborted: August - October [59]
     acorns drop:  from onset of winter storms through May [15,56]         

Related categories for Species: Quercus agrifolia | Coast Live Oak