Pinus sabiniana, gray pine
Howard, Janet L. 1992. Pinus sabiniana, gray pine. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/pinsab
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| PINSAB | gray pine | Pinus sabiniana | Life Form: Plants/Tree Kingdom: Plantae Class: Conifer Order: Pinales Family: Pinaceae Genus: Pinus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The scientific name for gray pine is Pinus sabiniana Dougl. [36,39]. There are no infrataxa [40].
Synonyms
- None.
Other Common Names
California foothill pine, foothills pine, bull pine, ghost pine.
General Distribution
Distribution of gray pine.
Gray pine is endemic to California. It is distributed from Siskiyou County south through the foothills of the Klamath, Cascade, and Coast Ranges and the Sierra Nevada to Ventura County [23,39,40]. Near its southernmost Sierra Nevada limit, gray pine is absent from a 55-mile (89-km) stretch between Kings River and the South Fork of the Tule River [23].
States and Provinces
- United States: CA
Site Characteristics
Gray pine grows on exposed, dry, rocky slopes at elevations from 100 to 6,000 feet (30-1,800 m) [23,26]. The climate is Mediterranean, with mild winters and hot, dry summers [35]. Annual mean precipitation is 21 inches (530 mm), ranging from 3 to 40 inches (76-1,000 mm) [6,40]. Eighty percent of precipitation occurs during winter and early spring. Snow falls occasionally [35]. The annual mean temperature is 61 degrees Fahrenheit (16 deg C), with maximum summer temperatures sometimes above 105 degrees Fahrenheit (41 deg C) [6,9]. Relative humidity is often 5 percent or lower in summer [9].
Plant Communities
Gray pine at the Red Hills Endangered Environmental Area, Tuolumne County, CA.
Gray pine and blue oak (Quercus douglasii) occur together over much of California's oak woodlands. The blue oak-gray pine community varies in stand density and composition, often sharing dominance with several other tree species. The understory may be mostly grasses, shrubs, or mixtures of both [16]. Pure stands of gray pine occur in localized areas of serpentine soil [21], but more often, blue oak provides more cover within the community type. At lower elevations, the blue oak-gray pine woodland grades into chaparral, valley oak (Q. lobata) woodland, or Oregon white oak (Q. garryana) woodland. At higher elevations, it mixes with California black oak (Q. kelloggii) or ponderosa pine (Pinus ponderosa) forest [16,26]. In its easternmost distribution, gray pine merges with desert communities such as western juniper (Juniperus occidentalis) and big sagebrush (Artemisia tridentata) near the Great Basin and singleleaf pinyon (P. monophylla)-California juniper (J. californica) near the Mojave Desert [16].
Plant associates: Overstory associates not mentioned in Table A1 include Coulter pine (P. coulteri), California buckeye (Aesculus californica), interior live oak (Quercus wislizenii), bigcone Douglas-fir (Pseudotsuga macrocarpa), and MacNab cypress (Cupressus macnabiana) [3,11,18,26,43].
Common shrub associates include toyon (Heteromeles arbutifolia), wedgeleaf ceanothus (Ceanothus cuneatus), chamise (Adenostoma fasciculatum), California scrub oak (Q. dumosa), desert scrub oak (Q. turbinella), California buckthorn (Rhamnus californicus), common manzanita (Arctostaphylos manzanita), birchleaf mountain-mahogany (Cercocarpus betuloides), poison-oak (Toxicodendron diversilobum), Sargent cypress (Cupressus sargentii), and hollyleaf cherry (Prunus ilicifolia) [2,3,11,24,26].
Common ground associates include slender oat (Avena barbata), California buckwheat (Erigonum fasciculatum), soft chess (Bruomus hordeaceus), ripgut brome (B. rigidus), cutleaf filaree (Erodium cicutarium), bur clover (Medicago hispida), ground lupine (Lupinus bicolor), and tarweed (Hemizonia spp.) [3,8,24].
Publications listing gray pine as a dominant or codominant species are as follows:
- A classification system for California's hardwood rangelands [2]
- Blue oak communities in California [3]
- Association types in the North Coast Ranges of California [12]
- Natural terrestrial communities of California [26]
Botanical Description
Gray pine with female and male cones, Santa Clara County, CA. (CC BY-NC 4.0)
Gray pine is a drought-tolerant, native evergreen conifer. Mature trees average from 40 to 80 feet (12-24 m) in height and from 12 to 36 inches (30-90 cm) in d.b.h. [38,40]. Trees usually maintain a pyramidal growth form until the pole stage. Mature trees typically have multiple trunks [40]. Gray pine is self-pruning, and lower branches are often a considerable distance above the understory [35]. Gray pine grows a deep taproot where soil depth permits [4,40]. In hardpan soils, it develops a spreading, shallow root system with a weak taproot extending through the duripan [40]. The bark of young trees is thin [40], while older trees have thick bark [35]. Needles grow from 8 to 12 inches (20-30 cm) long and are shed every 2 to 3 years [39]. Gray pine's heavily spined female cones are among the largest and most massive in the genus. Fresh cones average from 0.7 to 1.5 pounds (0.3-0.7 k), and may exceed 2.2 pounds (1 kg) [40]. The cones are typically from 6 to 12 inches (15-30 cm) long. They do not form an abscission layer and are retained long after seeds are shed. The hard-coated, heavy seeds are from 0.6 to 1.0 inch (15-25 mm) long and have short-winged seeds [17,38,39]. The lifespan of gray pine is unclear because most older specimens were cut by early settlers, but it is believed to be 200+ years [40].
Raunkiaer Life Form (Raunkiaer 1934)
- Phanerophyte
Seasonal Development
The seasonal development of gray pine is as follows:
| Event | Date Range |
|---|---|
| Growth starts | March to April [35] |
| Pollination | March to April [15,40] |
| Fertilization | Spring following pollination [40] |
| Cones mature | September to October [40] |
| Seeds dispersed | October to February [40] |
Regeneration Processes
Gray pine cones.
Gray pine produces seed at 10 to 25 years of age [33]. It is a consistent seed producer, with large crop outputs at 2- to 3-year intervals [40]. Gray pine has delayed seed dispersal [10,46]. Cones open slowly, shedding seed over a period of several months [40]. Seeds are disseminated by animals, gravity, and water [1,40]. Scrub jay and acorn woodpecker are the most effective animal disseminators [40].
Seeds require cold stratification for approximately 30 days prior to germination [27,33]. The exact stratification period varies with ecotype. Seedbank-stored seed remains viable for up to 5 years [33]. Germination rates improve when the seed is scarified and increase greatly when the nuclear cap is removed [40,48]. Germination is epigeal [33]. Seedlings establish best on bare mineral soil under partial shade. Most first-year growth occurs in the taproot. Subsequent top growth is rapid; early growth rates of gray pine are among the most rapid of all conifers. Rate of top growth averages 28 inches (70 cm) per year for the first 8 years of life [40].
Gray pine does not reproduce vegetatively [40].
Successional Status
Blue oak-gray pine communities are fire climax and are replaced by ponderosa pine or other coniferous forests in the absence of fire [16,26,32]. Gray pine readily establishes from seed on disturbed sites and is common in all seral stages of the blue oak-gray pine community [30]. Young trees tolerate partial shade [40]. Mature trees are shade intolerant [25].
Immediate Fire Effects
Moderate-severity fire kills a substantial number of gray pine. The prescribed fire in Glenville (see Fire Ecology or Adaptations) killed 83 percent of gray pine present. All surviving gray pine were large trees [35].
Postfire Regeneration Strategy (Stickney 1989)
- Tree without adventitious-bud root crown
- Ground residual colonizer (on-site, initial community)
- Secondary colonizer - on-site seed
- Secondary colonizer - off-site seed
Fire Adaptations
Fire is a natural component of the blue oak-gray pine community [1]. Historically, these woodlands burned at 15- to 30-year intervals [1]. Fires were typically intense but of light or moderate severity, with vegetation and fuels extremely dry in summer [9,28]. Researchers at the San Joaquin Experimental Range in O'Neals, California, noted fire surface temperatures near woody vegetation of 1,200 degrees Fahrenheit (650 deg C) in a blue oak-gray pine community with a mixed-grass and sparse brush understory [28]. A prescribed fire in a blue oak-gray pine community in Glenville, Kern County, generated subsurface temperatures of 156 degrees Fahrenheit (69 deg C) at a depth of 2 inches (0.8 cm) below ground [35].
Gray pine is highly flammable. The needles contain ether extracts [5]. It is a heavy resin producer, with the wood, bark, cones, and needle sheaths all containing pitch [35,40]. Congealed flows of resin that have dripped from wounds are common on gray pine. Consequently, it is susceptible to fire damage [40].
Gray pine has two adaptations which enable it to survive fire. First, some large trees will withstand moderate-severity fire. Mature trees with thick bark and self-pruned trunks are best able to avoid fatal scorching [35]. Secondly, seed regeneration is favored following fire. Fire creates a favorable bare mineral soil seedbed, and heat scarification of the woody seedcoat increases germination rates [40].
Plant Response to Fire
Information regarding postfire recovery of gray pine is sparse. Keeley [30] reported a gray pine seedling density of 133 per acre (54/ha) following a wildfire of unreported severity at Bartlett Springs, Lake County. Percentage cover provided by gray pine in a blue oak-gray pine community often decreases when fires are frequent. Many blue oak ecotypes sprout following fire, and under a regime of frequent fire, rapidly growing blue oak sprouts interfere with gray pine seedling growth [16,26].
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name on the Advanced Search page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
Gray pine is increasing in blue oak-gray pine communities due to fire suppression and lack of blue oak regeneration [14]. Rangeland managers are reporting an increase of chaparral brush invading grassy understories of blue oak-gray pine woodlands, also because of fire suppression [8]. Timber species are invading the woodlands as well [26]. Prescribed burning would help restore the blue oak-gray pine community to a more desirable species balance. Managers, however, should be alerted to the regeneration capacity of blue oak ecotypes within their area. See the blue oak FEIS Species Review for further information.
Fire managers recommend broadcast burning of blue oak-gray pine woodlands in spring after grasses have dried, usually late May, or in fall after the first rains. Fires are set with drip torches and permitted to burn downslope. There should be little or no wind. Recommended relative humidity range during spring is 30 to 35 percent; recommended ambient air temperature is between 70 to 80 degrees Fahrenheit (21-27 deg C). In fall, recommended relative humidity is 25 to 30 percent. Fall temperatures of 70 to 75 degrees Fahrenheit (21-24 deg C) are suggested [1].
If the woodlands contain a chaparral understory, upslope strip burning during winter and early spring is recommended. At this time, chaparral brush is fully green and grass shoots are from 2 to 3 inches (0.8-1.2 cm) high. Acceptable ranges of humidity are from 25 to 30 percent; acceptable temperature ranges are from 70 to 75 degrees Fahrenheit (21-24 deg C) [1].
Dwarf-mistletoe is eliminated from an infected area following a stand-replacing fire [31].
Bark beetles (Arhopalus asperatus) have been observed attacking severely scorched gray pine within hours following fire [45].
Federal Status
No special status.
Other Status
No entry.
Importance to Wildlife and Livestock
The blue oak-gray pine community is preferred habitat for black-tailed deer, California quail, and mourning dove [9]. Gray pine seeds are an important diet item for various birds and rodents. California scrub jay, acorn woodpecker, and California gray squirrel are major seed consumers [40]. Livestock also eat the seeds. High concentrations of resins and terpenes render gray pine browse unpalatable [42].
Palatability and Nutritional Value
The percent composition of gray pine seeds is as follows [47]:
| Nutrient | Percent |
|---|---|
| Protein | 25.0 |
| Fat | 49.4 |
| Carbohydrate | 17.5 |
Kcal/100g: 571.
The concentrations of several essential minerals in gray pine seeds are available [47].
Cover Value
No entry.
Value for Rehabilitation or Restoration of Disturbed Sites
Gray pine has been planted on a limited basis for erosion control. Commercial nursery stock is unavailable. Seedlings have been established on rehabilitation sites by planting 1- or 2-year-old bareroot stock grown from locally collected seed [27,29]. Gray pine is an appropriate choice for planting in soils with calcium imbalances. It will grow well on both serpentine soil, where calcium is deficient, and on limestone soil, where calcium is abundant. In addition, it will grow on xeric sites where establishment of other tree species is difficult [40].
Other Uses
Gray pine seeds were important in the diet of California Indians [40].
Gray pine wood has minor commercial value. It is used for making railroad ties, box shook, pallet stock, and chips. Poor form, high resin content, and high proportions of compression wood result in low stumpage prices. The mechanical strength properties of the wood have been detailed [49]. Gray pine is expensive to log due to low stand density [40].
Other Management Considerations
Gray pine is considered an undesirable weed tree by many rangeland managers. Production and quality of forage growing under gray pine is less than that growing under blue oak. Additionally, gray pine provides little shade for livestock during hot summer months [13,22,40]. It has been extensively cut within the last century in order to clear rangeland areas [40].
Diseases: Prominent diseases of gray pine include western gall rust (Periderium harknessii) and dwarf-mistletoe (Arceuthobium occidentale and A. campylopodum forma campylopodum) [1,20,31,40]. Western gall rust forms galls on gray pine throughout its range but rarely causes serious damage. Dwarf-mistletoe is a particularly damaging and widespread disease [40]. It infects trees of all ages, causing reduced tree vigor or death. Left uncontrolled, infection can increase sixty-fold within 10 years [20]. Arceuthobium occidentale also infects Douglas-fir (Pseudotsuga menziesii) and bigcone Douglas-fir, while A. campylopodum forma campylopodum can infect Coulter, Jeffrey (Pinus jeffreyi), Monterey (P. radiata), and ponderosa pines [20,31]. Dwarf-mistletoe is controlled by cutting infected trees or removing infected branches [31].
Gray pine is the specific host for Ips spinifer. This bark beetle generally attacks fire- or drought-weakened trees. Heavy resin production by healthy trees provides a strong defense against most species of bark beetles. Gray pine is host to a variety of cone, twig, and foliage insects, but the damage they cause is usually minor [40].
Gray pine growing in hardpan is susceptible to windthrow under waterlogged soil conditions [40].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES20 Douglas-fir
- FRES21 Ponderosa pine
- FRES27 Redwood
- FRES28 Western hardwoods
- FRES29 Sagebrush
- FRES34 Chaparral - mountain shrub
- FRES35 Pinyon - juniper
- FRES42 Annual grasslands
BLM Physiographic Regions (Bernard and Brown 1977)
- 3 Southern Pacific Border
- 4 Sierra Mountains
- 7 Lower Basin and Range
Kuchler Plant Associations (Kuchler 1964)
- K005 Mixed conifer forest
- K006 Redwood forest
- K009 Pine - cypress forest
- K010 Ponderosa shrub forest
- K011 Western ponderosa forest
- K023 Juniper - pinyon woodland
- K024 Juniper steppe woodland
- K028 Mosaic of K002 and K026
- K029 California mixed evergreen forest
- K030 California oakwoods
- K033 Chaparral
- K034 Montane chaparral
- K035 Coastal sagebrush
- K038 Great Basin sagebrush
- K048 California steppe
SAF Cover Types (Eyre 1980)
- 233 Oregon white oak
- 234 Douglas-fir - tanoak - Pacific madrone
- 238 Western juniper
- 239 Pinyon - juniper
- 244 Pacific ponderosa pine - Douglas-fir
- 245 Pacific ponderosa pine
- 246 California black oak
- 247 Jeffrey pine
- 248 Knobcone pine
- 249 Canyon live oak
- 250 Blue oak - gray pine
- 255 California coast live oak
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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