Index of Species Information

SPECIES:  Pinus attenuata


SPECIES: Pinus attenuata
AUTHORSHIP AND CITATION : Howard, Janet L. 1992. Pinus attenuata. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [].

ABBREVIATION : PINATT SYNONYMS : NO-ENTRY SCS PLANT CODE : PIAT COMMON NAMES : knobcone pine TAXONOMY : 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]. LIFE FORM : Tree FEDERAL LEGAL STATUS : No special status OTHER STATUS : NO-ENTRY


SPECIES: Pinus attenuata
GENERAL DISTRIBUTION : 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 Bernadino mountains, at Cuesta Pass, San Luis Obisbo County, and near Encinada, Baja California [14,21,32,44]. ECOSYSTEMS : FRES20 Douglas-fir FRES21 Ponderosa pine FRES27 Redwood FRES28 Western hardwoods FRES34 Chaparral - mountain shrub STATES : CA OR MEXICO BLM PHYSIOGRAPHIC REGIONS : 1 Northern Pacific Border 2 Cascade Mountains 3 Southern Pacific Border 4 Sierra Mountains KUCHLER PLANT ASSOCIATIONS : 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 SAF COVER TYPES : 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 - Digger pine 255 California coast live oak SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : 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 Bernadino Mountains [14] Vegetation of the San Bernadino 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]


SPECIES: Pinus attenuata
WOOD PRODUCTS VALUE : There is no commercial market for knobcone pine wood [11]. IMPORTANCE TO LIVESTOCK AND WILDLIFE : 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]. PALATABILITY : NO-ENTRY NUTRITIONAL VALUE : NO-ENTRY COVER VALUE : NO-ENTRY VALUE FOR REHABILITATION OF DISTURBED SITES : 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]. OTHER USES AND VALUES : NO-ENTRY OTHER MANAGEMENT CONSIDERATIONS : Knobcone pine populations are currently stable. The species is apparently not subject to heavy insect or disease attack [44]. It may become infected with dwarfmistletoe (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 dwarfmistletoe. 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].


SPECIES: Pinus attenuata
GENERAL BOTANICAL CHARACTERISTICS : 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) [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]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : 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]. SITE CHARACTERISTICS : 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 [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, 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. 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]. SUCCESSIONAL STATUS : 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]. SEASONAL DEVELOPMENT : Seeds germinate from early February through late March, depending on elevation [47]. Pollination occurs from March until May [33].


SPECIES: Pinus attenuata
FIRE ECOLOGY OR ADAPTATIONS : 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. POSTFIRE REGENERATION STRATEGY : Tree without adventitious-bud root crown Crown residual colonizer (on-site, initial community)


SPECIES: Pinus attenuata
IMMEDIATE FIRE EFFECT ON PLANT : 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]. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : 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]. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : NO-ENTRY 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 [40].


SPECIES: Pinus attenuata
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