closed-cone species. Discontinuous populations occur from southwestern
Oregon south through the Klamath, Cascade, and Coast ranges and the
Sierra Nevada. Stands in the South Coast Ranges are widely disjunct,
occurring in the Santa Ana and west San Bernadino mountains, at Cuesta
Pass, San Luis Obisbo County, and near Encinada, Baja California
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
Occurrence in North America
Knobcone pine is a rapidly growing, native tree from 20 to 40 feet (6-12
m) tall and 13.5 to 23 inches (34-58 cm) in d.b.h. [13,41]. The crown
is dense and broad when young, becoming open when mature. Trees
typically have multiple trunks with thin bark [36,42]. Excavtion of
knobcone pine roots in the Santa Ana Mountains showed that vertical
roots grew to bedrock in the shallow soil. Average root depth was 10.4
inches (26.2 cm) . Roots in less restrictive sites are reported as
"wide and deep" .
Trees produce female cones in groups of four or five, all firmly
attached to stout branches in a tight whorl. The asymmetrical cones are
arched in configuration, as are the individual ovuliferous scales.
Cones remain closed and attached to the tree for life [40,48]. The
enclosed seeds are small and light, with thin seed coats and long seed
wings [15,41]. The lifespan of knobcone pine is relatively short. Some
trees reach ages of 75 to 100 years , but in a typical 60-year-old
stand, over half the pines are dead .
California Montane Chaparral and Woodlands Habitat
This taxon can be found in the California montane chaparral and woodlands, a near coastal ecoregion in Central and Southern California, USA. This ecoregion is disjunctive, with a major element in Southern California and another along the Monterey County coast. The ecoregion encompasses most of the Transverse Range that includes the San Bernardino Mountains; San Gabriel Mountains; portions of the Santa Ynez and San Rafael Mountains; Topatopa Mountains; San Jacinto Mountains; the Tehachapi, Greenhorn, Piute, and Kiavah Mountains that extend roughly northeast-southwest from the southern Sierra Nevada; and the Santa Lucia Range that parallels the coast southward from Monterey Bay to Morro Bay.
The California montane chaparral and woodland ecoregion consists of a complex mosaic of coastal sage scrub, lower chaparral dominated by chamise, upper chaparral dominated by manzanita, desert chaparral, Piñon-juniper woodland, oak woodlands, closed-cone pine forests, yellow pine forests, sugar pine-white fir forests, lodgepole pine forests, and alpine habitats. The prevalence of drought-adapted scrub species in the flora of this ecoregion helps distinguish it from similar communities in the Sierras and other portions of northern California. Many of the shared Sierra Nevadan species typically are adapted to drier habitats in that ecoregion, Jeffrey Pine (Pinus jeffreyi) being a good example.
Oak species are an important component of many chaparral and forest communities throughout the ecoregion. Canyon Live Oak, Interior Live Oak, Tanbark Oak (not a true Quercus species), Engelmann Oak, Golden-cup Oak, and Scrub Oak are some examples. Mixed-conifer forests are found between 1371 to 2896 meters elevation with various combinations and dominance of incense cedar, sugar pine, and white fir, Jeffrey Pine, Ponderosa Pine, and mountain juniper. Subalpine forests consist of groves of Limber Pine (Pinus flexilis), Lodgepole Pine, and Jeffrey Pine. Very old individual trees are commonly observed in these relict subalpine forests. Within this zone are subalpine wet meadows, talus slope herbaceous communities, krumholz woodlands, and a few small aspen groves.
In addition to these general vegetation patterns, this ecoregion is noted for a variety of ecologic islands, communities with specialized conditions that are widely scattered and isolated and typically harbor endemic and relict species. Examples include two localities of Knobcone Pine (Pinus attenuata) on serpentine soils, scattered vernal pools with a number of endemic and relict species, and isolated populations of one of North America’s most diverse cypress floras, including the rare Gowen Cypress (Cupressus goveniana goveniana) restricted to two sites on acidic soils in the northern Santa Lucia Range, Monterey Cypress (Cupressus macrocarpa) found only at two coastal localities near Monterey Bay, and Sargent Cypress (Callitropsis sargentii LR/LC) restricted to serpentine outcrops. Monterey Pine (Pinus radiata) is also restricted to three coastal sites near Monterey Bay.
The ecoregion is also home to a few endemic or near-endemic mammalian vertebrates, such as the White-eared Pocket Mouse (Perognathus alticolus EN), a mammal known only to two disjunct mountain ranges in southern California: San Bernardino Mountains in San Bernardino County (ssp. alticolus), and the Tehachapi Mountains, in Kern, Ventura, and Los Angeles counties. The near-endemic fossorial Agile Kangaroo Rat (Dipodomys agilis) is found in the southern disjunctive unit of the ecoregion, and is known only to the Los Angeles Basin and foothills of San Gabriel and San Bernardino mountains in Ventura, Los Angeles, and Riverside counties north to Santa Barbara County and through the southern Sierra Nevada, including Mount Pinos, Tehachapi and San Gabriel mountains, and northern San Fernando Valley. Non-endemic mammals found in the ecoregion include Botta's Pocket Gopher (Thomomys bottae) and Trowbridge's Shrew (Sorex trowbridgii). Some larger vertebrate predators can be found in the ecoregion, including Puma (Puma concolor), Bobcat (Lynx rufus), Coyote (Canis latrans), and Ringtails (Bassariscus astutus).
The ecoregion boasts five endemic and near-endemic amphibians, largely Plethodontid salamanders. Some specific salamander taxa found here are the endemic Tehachapi Slender Salamander (Batrachoseps stebbinsi VU), known from isolated sites in the Caliente Creek drainage, Piute Mountains, and Kern County, California along with scattered populations in the Tehachapi Mountains to Fort Tejon, Kern County; the near-endemic Blackbelly Slender Salamander (Batrachoseps nigriventris); the Monterey Ensatina (Ensatina eschscholtzii); the Channel Islands Slender Salamander (Batrachoseps pacificus), endemic to a narrow range restricted solely on Anacapa, Santa Cruz, Santa Rosa, and San Miguel islands; and the Arboreal Salamander (Aneides lugubris), found only in California and Baja California. A newt found here is the Coast Range Newt (Taricha torosa). Anuran taxa in the ecoregion include the Foothill Yellow-legged Frog (Rana boylii NT); the Southern Mountain Yellow-legged Frog (Rana muscosa EN), a California endemic occurring in several disjunctive populations; and the Northern Red-legged Frog (Rana aurora).
The California montane chaparral and woodlands ecoregions contains a number of reptiles such as the Coast Horned Lizard (Phrynosoma coronatum), who ranges from Northern California to Baja California. Also found here is the Sagebrush Lizard (Sceloporus graciosus); the Western Fence Lizard (Sceloporus occidentalis); the Southern Alligator Lizard (Elgaria multicarinata); and the Side-blotched Lizard (Uta stansburiana). The Two-striped Garter Snake (Thamnophis hammondii) is a restricted range reptile found near-coastally from Monterey County, California southward to Baja California.
The California Condor once inhabited much of the ecoregion, with the western Transverse Range acting today as a refuge for some of the last wild populations, after considerable conservation efforts, especially in the Los Padres National Forest. The Heermann's Gull (Larus heermanni NT) is found in coastal areas of the ecoregion.
Habitat and Ecology
Comments: On Sierra Juárez it grows at 250-1200 m altitude, rocky, gravelly-sandy soil, with winter anual rainfall of 600 mm aprox. Hot temperatures in the summer and snow and frezzing in the winter.
The climate in which knobcone pine grows is mediterranean, characterized
by wet, mild winters and hot, dry summers. Fog drip often precipitates
heavily beneath pines during summer months in coastal regions,
ameloirating the effects of hot weather . The pines grow at
elevations between sea level and 5,500 feet (1,676 m) .
Soil parent materials are usually of volcanic origin ; serpentine is
the most common substrate [18,29]. Soils are typically shallow, rocky,
infertile, ultramafic, acid, and/or dry. They may contain levels of
magnesium, chromium, nickel, and/or cobalt that are toxic to most plants
. Calcium, nitrogen, and phosphorus are usually deficient .
Soil pH at a knobcone pine site in the Santa Ana Mountains was 5.0 .
Water-retaining capacity of knobcone pine soils are often favorable to
its growth. The average saturation percentage of serpentine soils is
nearly double that of adjacent chaparral . Slope angles range
between 0 and 38 degrees but are most commonly steep and subject to
continual erosion. Knobcone pine communities often occur along fault
blocks where earthquake activity has produced fresh serpentine
Plant associates: Overstory associates not listed in Distribution and
Occurrence include Monterey pine, Coutler pine (Pinus coulteri), Digger
pine (P. sabiniana), sugar pine (P. lambertiana), shore pine (P.
contorta spp. contorta), bigcone Douglas-fir (Pseudotsuga macrocarpa),
Pacific madrone (Arbutus mensiesii), tanoak (Lithocarpus densiflora),
giant chinkapin (Chrysopelis chrysophylla), incense-cedar (Libocedrus
decurrens), Pacific yew (Taxus brevifolia), tecate cypress (Cupressus
forbesii), Santa Cruz cypress (C. abramsiana), and MacNab cypress (C.
Some shrub associates are Eastwood manzanita (Arctostaphylos
glandulosa), pinemat manzanita (A. nevadensis), chamise, chaparral
whitethorn (Ceanothus leucodermis), wartleaf ceanothus (C. papillosus
var. rowaenus), wedgeleaf ceanothus (C. cuneatus), leather oak (Quercus
durata), chaparral currant (Ribes malvaceum var. viridifolium), Sargent
cypress (Cupressus sargentii), chaparral pea (Pickeringia montana), and
huckleberry (Vaccinium spp.) [6,14,42,44,46].
Ground cover associates include Carey balsamroot (Balsamorhiza
deltoidea), Hooker balsamroot (B. hookeri), fire reedgrass
(Calamagrostis koeleroides), houndstongue hawkweed (Hieracium
cynoglossoides var. nudicaule), big deervetch (Lotus crassifolius),
showy phlox (Phlox speciosa), and brome grasses (Bromus spp.) [14,41,46].
Key Plant Community Associations
The knobcone pine community occupies a transitional position between
chaparral and woodland and higher elevation forests. Because of its
patchy distribution, it is usually surrounded by other communities. At
lower elevations, it is most often associated with chamise (Adenostoma
fasciculatum)-manzanita (Arctostaphylos spp.) communities and various
oak (Quercus spp.) woodlands. At higher elevations, it is associated
with a variety of coniferous communities (see SAF Cover Types) .
Within the knobcone pine community, the pines are usually widely spaced.
The community is sometimes described as woodland rather than as forest
. On favorable sites, knobcone pine forms dense, even-aged stands
or dwarfed thickets. Understory herbaceous species are usually
fire-followers and endemics. Shrubs occur individually or in small
patches between pines. Mosaics of chaparral, woodland, knobcone pine,
and other coniferous forests sometimes occur due to topographical and
substrate differences [32,41,44].
Publications listing knobcone pine as a dominant species are as follows:
Vegetational types of the San Bernadino Mountains 
Vegetation of the San Bernadino Mountains 
A vegetation classification system applied to southern California 
Mixed evergreen forest 
Vegetation of the Siskiyou Mountains, Oregon and California 
An introduction to the plant communities of the Santa Ana and San
Jacinto Mountains 
The closed-cone pines and cypresses 
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
K006 Redwood forest
K009 Pine - cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K026 Oregon oakwoods
K028 Mosaic of K002 and K026
K029 California mixed evergreen forest
K030 California oakwoods
K034 Montane chaparral
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
215 Western white pine
229 Pacific Douglas-fir
233 Oregon white oak
234 Douglas-fir - tanoak - Pacific madrone
244 Pacific ponderosa pine - Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
249 Canyon live oak
250 Blue oak - Digger pine
255 California coast live oak
Habitat & Distribution
Fire Management Considerations
Fire is essential for the completion of knobcone pine's life cycle.
Cones of senescent or dead trees must be opened by fire to perpetuate
the groves before trees succumb and add the unopened cones to the
decomposing litter .
Plant Response to Fire
quickly germinates with late winter or early spring rains .
Seedlings continue to establish over a period of several years as cones
slowly open and release seeds. Aerial photographs taken at postfire
year 16 of a burn on Cerro Miracielo, Baja California, showed that
saplings had established throughout the burn .
Immediate Effect of Fire
Crown fire kills knobcone pine of all size classes and vaporizes the
resin sealing their cones [13,41]. The effect of surface fires on
mature trees is undocumented. The thin bark, however, probably provides
little protection from all but low-severity surface fire. Saplings are
killed by surface fire. Fire is not a threat to young trees, however,
since the preceding stand-replacing fire has removed most of the fuel
load . Cones are extremely fire resistant and are seldom consumed
by fire .
Tree without adventitious-bud root crown
Crown residual colonizer (on-site, initial community)
Knobcone pine is an obligate fire type with a strict closed-cone habit.
This adaptation, along with the general absence of animal agents that
might open cones, leaves the species dependent upon stand-replacing
crown fire for reproduction. Continued production and accumulation of
cones throughout the life of a tree assures that large quantities of
seed are released when fire opens cones. The open, multitrunked growth
form of knobcone pine promotes fire crowning .
Fire creates seedbed conditions favorable for germination and seedling
recruitment. It temporarily raises soil pH and increases soil nutrient
content, particularly phosphorus and nitrogen. A longer-term benefit of
fire to the species is the retrogressive role it plays in soil genesis.
By removing litter and ground cover vegetation, fire contributes to soil
erosion. Wind-felling of fire-killed trees results in further churning
up of nutrient-deficient soils. Most plant species cannot compete with
knobcone pine on such poor sites. The discontinuous nature of
serpentine prevents all the pines in an area from being killed by any
one fire .
Natural fires are probably less frequent in knobcone pine forests than
in other western closed-cone communities . The infertile sites
where knobcone pine occurs support little undercover. Litter layers
are usually moderate . A 20-year-old plantation in the San Dimas
Experimental Forest, southern California, produced 10.9 tons of forest
floor per acre (24.5 t/ha) . The average interval between fires is
More info for the terms: competition, cover
Obligate Initial Community Species
Knobcone pine is a shade-intolerant pioneer species [9,36,40]. Fire
creates the conditions necessary for its continued survival. Old
knobcone pine stands, undisturbed for 60 or more years, will show signs
of invasion and competition from surrounding communities because the
resultant soil genesis and organic matter deposition have begun to
reduce or cover the restrictive barriers produced by serpentine .
In the absence of fire, knobcone pine is replaced by chaparral shrub
species at lower elevations and other conifers at higher elevations
Knobcone pine reproduction is controlled exclusively by fire; trees
occur in even-aged stands dating back to the last fire [42,43]. Unlike
other closed-cone species whose cones open with hot weather, upon
falling, or with age, unburned knobcone pine cones remain closed even
after trees have decayed and fallen. Cones are sealed with a hard resin
that requires high temperatures (average: 397 degrees Fahrenheit [203
deg C]) to liquefy, boil, and vaporize. Cone scales open gradually
following heating. The first seeds fall within 1 to 12 hours after
fire, when the ground has cooled. The arched scales continue to slowly
expand and drop seed for at least 4 postfire years. Scales partially
contract during periods of rain or other high relative humidity, but
resume expansion when relative humidity drops . The small, light
seeds are wind dispersed. Knobcone pine has the greatest seed wing
length:seed size ratio of all the California closed-cone pines, allowing
for seed dispersal well beyond the edges of a fire . Santa Ana
foehn winds, which blow during periods of low relative humidity, spread
seed for great distances. Seed wings from charred or scorched cones
often have fire-seared tips, causing seeds to fall in a slower spin than
seeds with unburned wing tips. Seeds with burned wings fall closer to
the parent tree. Birds aid in disseminating some seed. Steller and
scrub jays, attracted to partially opened cones, pound them heavily to
extract seeds. This results in additional seed dropping to the ground.
Hairy and downy woodpeckers may also jar seed from cones as they work
over burned stems in search of insects . Western grey squirrel are
sometimes able to chew through unopened cones and may disseminate small
amounts of seed .
Trees begin seed production between 10 and 12 years of age. Average
production of trees over 20 years old is 176 cones per tree .
Limited tests show seed viability does not decline with age. Seeds
enclosed in cones for 27  and 60  years have proved viable.
Following release, seeds require cold stratification for 60 days [3,19].
Germinative capacity of seeds from mechanically opened cones has varied
from 57 to 91 percent [19,41]. Hot fire probably kills some seed.
Laboratory tests show that germination rates of seed from mechanically
opened cones are greater than those of cones opened by oven heat
treatment. Seeds may require a rise from normally low soil pH for
germination, and fire creates such a condition . Knobcone pine
germinates earlier than other pines. Tested against Coulter and sugar
pines, it was the first of the three species to germinate .
Seedlings require bare mineral soil for establishment. They are drought
tolerant, with a strong tendency toward deep rooting . Seedlings
establishing on fertile sites compete poorly with chaparral shrubs and
other tree species. Knobcone pine seedlings, however, can tolerate
nutrient-deficient soils which restrict the growth of most competitors
[14,29,41]. Knobcone pine does not vegetatively reproduce .
Growth Form (according to Raunkiær Life-form classification)
Life History and Behavior
Molecular Biology and Genetics
Barcode data: Pinus attenuata
Statistics of barcoding coverage: Pinus attenuata
Public Records: 5
Specimens with Barcodes: 11
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Pinus attenuata has an extensive extent of occurrence and is still numerous in certain parts of its range, especially in the northern counties of California. In certain areas close to urbanization fire prevention and suppression is likely to affect this species negatively in future, so a limited decline percentage is suspected for the future. However, this seems insufficient in relation to the global population size to place this species under threat or even to mark it as Near Threatened.
- 1998Lower Risk/least concern (LR/lc)
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Southwestern Oregon to northern Baja California (Mexico), in scattered localities. In Mexico, it is quite rare in Mexico, where it is one of three pine species native to Baja California. Small populations near Ensenada should be protected and could serve as a source of seed for test plantings in the state of Baja California Norte. In the U.S. it occurs primarily in SW Oregon, with small populations in California.
Knobcone pine populations are currently stable. The species is
apparently not subject to heavy insect or disease attack . It may
become infected with dwarfmistletoe (Arceuthobium campylopodum), but the
literature is inconsistent on severity of infection. Mathiasen and
Hawksworth  believe that it is immune to such infestation. Kimmey
 reported it as "rarely infested" with western dwarf mistletoe (A.
campylopodum f. campylopodum), while Hempel  stated that it is
"often infected" with dwarfmistletoe. There are unconfirmed reports of
infestation in southwestern Oregon .
Feral pigs, which damage trees by tusking trunks with their canines,
commonly attack knobcone. Trees so tusked are often girdled for
distances of 3 to 4 inches (8-14 cm) up the trunk, resulting in death of
the tree. The motivation for this behavior in swine is unknown .
Relevance to Humans and Ecosystems
Value for rehabilitation of disturbed sites
areas with shallow, ultramafic, or sandy dry soils [8,13]. Survival and
growth rates are favorable. Plantation seedlings used for erosion
control in southern California attained heights of about 15 feet (4.6 m)
in 10 years. Trees are usually planted on-site from bareroot nursery
seedlings, although knobcone pine can be cloned if cuttings are taken
from trees less than 5 years of age. Seed collection and processing
techniques and details on seedling care are outlined in the literature
Importance to Livestock and Wildlife
cones deter most seed predators, although the western grey squirrel
consumes some seed. Jays eat seeds of opened cones [41,48].
The knobcone pine, Pinus attenuata, (also called Pinus tuberculata) is a tree that grows in mild climates on poor soils. It ranges from the mountains of southern Oregon to Baja California with the greatest concentration in northern California and the Oregon-California border.
The knobcone pine (Pinus attenuata) crown is usually conical with a straight trunk. It reaches heights of 8–24 metres (26–79 ft). However, it can be a shrub on especially poor sites. It prefers dry rocky mountain soils. The bark is smooth, flaky and gray-brown when young, becoming dark gray-red-brown and shallowly furrowed into flat scaly ridges. The twigs are red-brown and often resinous.
The leaves are in fascicles of three, needle-like, yellow-green, twisted, and 9–15 cm (about 3.5–6 in) long. The cones are 8–16 cm long and clustered in whorls of three to six on the branches. The scales end in a short stout prickle. The cones remain closed for many years until a fire opens them and allows reseeding. As a result, the cones may even become embedded in the trunk as the tree grows.
- Conifer Specialist Group, 1998
- Chase, J. Smeaton (1911). Cone-bearing Trees of the California Mountains. Chicago: A. C. McClurg & Co. p. 99. LCCN 11004975. OCLC 3477527. LCC QK495.C75 C4, with illustrations by Carl Eytel - Kurut, Gary F. (2009), "Carl Eytel: Southern California Desert Artist", California State Library Foundation, Bulletin No. 95, pp. 17-20 retrieved Nov. 13, 2011
- Moore, Gerry; Kershner, Bruce; Craig Tufts; Daniel Mathews; Gil Nelson; Spellenberg, Richard; Thieret, John W.; Terry Purinton; Block, Andrew (2008). National Wildlife Federation Field Guide to Trees of North America. New York: Sterling. p. 85. ISBN 1-4027-3875-7.
- Gymnosperm Database, 2008
- eNature Field Guides, 2007
- C. Michael Hogan, 2008
- Conifer Specialist Group (1998). Pinus attenuata. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006.
- eNature Field Guides (2007) Knobcone Pine
- Gymnosperm Database (2008) Pinus attenuata
- C. Michael Hogan (2008) Blue Oak: Quercus douglasii, GlobalTwitcher.com, ed. Nicklas Stromberg
Names and Taxonomy
attenuata Lemm. [21,33,36]. There are no subspecies or varieties. The
distributions of knobcone and Monterey (P. radiata) pines overlap in
Santa Cruz County, where they produce the hybrid P. X attenuradiata
Stockw. & Right [21,33,35].