Knobcone Pine

Pinus attenuata , mostly a chaparral species, bears cones at an early age. Its seed crops are heavy, and a hot fire permits the seeds to be released. It forms hybrids with P . muricata and P . radiata .

Shrubs or trees to 24m; trunk to 0.8m diam., usually straight; crown mostly narrowly to broadly conic. Bark purple-brown to dark brown, shallowly and narrowly fissured, with irregular, flat, loose-scaly plates, on upper sections of trunk nearly smooth. Branches ascending; twigs slender, red-brown. Buds ovoid to ovoid-cylindric, dark red-brown, aging darker, ca. 1.5cm, resinous; scale margins fringed, apex attenuate. Leaves 3 per fascicle, spreading or ascending, persisting 4--5 years, (8--)9--15(--20)cm ´ (1--)1.3--1.8mm, straight or slightly curved, twisted, yellow-green, all surfaces with fine stomatal lines, margins serrulate, apex abruptly conic-subulate; sheath (1--)1.5--2cm, base persistent. Pollen cones ellipsoid-cylindric, 10--15mm, orange-brown. Seed cones maturing in 2 years, serotinous, long-persistent, remaining closed for 20 years or more, or opening on burning, in whorls, hard and heavy, very asymmetric, lanceoloid before opening, ovoid-cylindric when open, 8--15cm, yellow- or pale red-brown, stalks to 1cm; apophyses toward outside base increasingly elongate, mammillate or raised-angled-conic, downcurved near base, scarcely raised on branchlet side, rhombic; umbo central, low-pyramidal, sharp, upcurved. Seeds compressed-oblique-obovoid; body ca. 6--7mm, nearly black; wing narrow, to 20mm. 2 n =24.

Fire successional on dry slopes and foothills of Sierra Nevada and the Cascade and Coast ranges; 300--1200m; Calif., Oreg.; Mexico in Baja California.

Pinus tuberculata Gordon 1849, not D.Don 1836

knobcone pine

More info for the terms: seed, tree

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]. Excavation 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) [41]. Roots in less restrictive sites are reported as
"wide and deep" [36].

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 [14], but in a typical 60-year-old
stand, over half the pines are dead [41].

Knobcone pine is the most widely distributed of the West Coast
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 Bernardino mountains, at Cuesta
Pass, San Luis Obispo County, and near Ensenada, Baja California
[14,21,32,44].

More info for the terms: cover, crown fire, fire regime, forest, litter, natural, seed, tree

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 [41].

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 [41].

Natural fires are probably less frequent in knobcone pine forests than
in other western closed-cone communities [25]. The infertile sites
where knobcone pine occurs support little undercover. Litter layers
are usually moderate [13]. 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) [17]. The average interval between fires is
undocumented.

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the term: litter

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 [40].

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More info for the term: phanerophyte

Phanerophyte

More info for the terms: cover, fresh, serpentine soils, shrub

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,
ameliorating the effects of hot weather [41]. The pines grow at
elevations between sea level and 5,500 feet (1,676 m) [44].

Soil parent materials are usually of volcanic origin [43]; 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
[44]. Calcium, nitrogen, and phosphorus are usually deficient [43].
Soil pH at a knobcone pine site in the Santa Ana Mountains was 5.0 [43].
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 [41]. 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
escarpments [41].

Plant associates: Overstory associates not listed in Distribution and
Occurrence include Monterey pine, Coulter pine (Pinus coulteri), gray
pine (P. sabiniana), sugar pine (P. lambertiana), shore pine (P.
contorta spp. contorta), bigcone Douglas-fir (Pseudotsuga macrocarpa),
Pacific madrone (Arbutus menziesii), tanoak (Lithocarpus densiflora),
giant chinkapin (Chrysolepis chrysophylla), incense-cedar (Calocedrus
decurrens), Pacific yew (Taxus brevifolia), tecate cypress (Hesperocyparis
forbesii), Santa Cruz cypress (H. abramsiana), and MacNab cypress (H.
macnabiana) [26,27,28,44].

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].

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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
231 Port-Orford-cedar
232 Redwood
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 - gray pine
255 California coast live oak

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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):

FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES27 Redwood
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: forest, 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
K033 Chaparral
K034 Montane chaparral

More info for the terms: fuel, stand-replacing fire, surface 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 [30]. Cones are extremely fire resistant and are seldom consumed
by fire [41].

More info for the term: seed

Knobcone pine is unpalatable browse [13]. The heavily spiked, closed
cones deter most seed predators, although the western grey squirrel
consumes some seed. Jays eat seeds of opened cones [41,48].

More info for the terms: cover, forest, herbaceous, shrubs, woodland

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) [44].
Within the knobcone pine community, the pines are usually widely spaced.
The community is sometimes described as woodland rather than as forest
[24]. 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 Bernardino Mountains [14]
Vegetation of the San Bernardino Mountains [31]
A vegetation classification system applied to southern California [34]
Mixed evergreen forest [38]
Vegetation of the Siskiyou Mountains, Oregon and California [46]
An introduction to the plant communities of the Santa Ana and San
Jacinto Mountains [42]
The closed-cone pines and cypresses [44]

More info for the term: tree

Tree

More info for the terms: severity, tree

Knobcone pine populations are currently stable. The species is
apparently not subject to heavy insect or disease attack [44]. It may
become infected with dwarf-mistletoe (Arceuthobium campylopodum), but the
literature is inconsistent on severity of infection. Mathiasen and
Hawksworth [23] believe that it is immune to such infestation. Kimmey
[16] reported it as "rarely infested" with western dwarf mistletoe (A.
campylopodum f. campylopodum), while Hempel [12] stated that it is
"often infected" with dwarf-mistletoe. There are unconfirmed reports of
infestation in southwestern Oregon [10].

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 [4].

CA OR MEXICO

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Seeds germinate from early February through late March, depending on
elevation [47]. Pollination occurs from March until May [33].

More info for the term: seed

Fire-opened cones remain attached to standing dead trees. Released seed
quickly germinates with late winter or early spring rains [47].
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 [32].

More info for the terms: crown residual colonizer, root crown

Tree without adventitious-bud root crown
Crown residual colonizer (on-site, initial community)

More info for the terms: cone, seed, shrubs, stratification, tree

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 [41]. 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 [15]. 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 [41]. Western grey squirrel are
sometimes able to chew through unopened cones and may disseminate small
amounts of seed [42].

Trees begin seed production between 10 and 12 years of age. Average
production of trees over 20 years old is 176 cones per tree [41].
Limited tests show seed viability does not decline with age. Seeds
enclosed in cones for 27 [45] and 60 [41] 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 [41]. Knobcone pine
germinates earlier than other pines. Tested against Coulter and sugar
pines, it was the first of the three species to germinate [47].
Seedlings require bare mineral soil for establishment. They are drought
tolerant, with a strong tendency toward deep rooting [47]. 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 [19].

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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

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More info for the terms: competition, cover, shrub

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 [41].
In the absence of fire, knobcone pine is replaced by chaparral shrub
species at lower elevations and other conifers at higher elevations
[1,41].

The currently accepted scientific name of knobcone pine is Pinus
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].

More info for the term: seed

Knobcone pine is planted for riparian and watershed rehabilitation in
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
[13,19].

There is no commercial market for knobcone pine wood [11].

Tree, Shrub, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds resinous, Leaves needle-like, Leaves alternate, Needle-like leaf margins finely serrulate (use magnification or slide your finger along the leaf), Leaf apex acute, Leaves > 5 cm long, Leaves < 10 cm long, Leaves yellow-green above, Leaves yellow-green below, Leaves not blue-green, Needle-like leaves somewhat rounded, Needle-like leaves twisted, Needle-like leaf habit erect, Needle-like leaves per fascicle mostly 3, Needle-like leaf sheath persistent, Twigs glabrous, Twigs viscid, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones > 5 cm long, Seed cones bearing a scarlike umbo, Umbo with obvious prickle, Bracts of seed cone included, Seeds black, Seeds winged, Seeds unequally winged, Seed wings prominent, Seed wings equal to or broader than body.

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.