William W. Oliver and Russell A. Ryker
Ponderosa pine (Pinus ponderosa), also called western yellow pine, is one of the most widely distributed pines in western North America. A major source of timber, ponderosa pine forests are also important as wildlife habitat, for recreational use, and for esthetic values. Within its extensive range, two varieties of the species currently are recognized: Pinus ponderosa var. ponderosa (Pacific ponderosa pine) (typical) and var. scopulorum (Rocky Mountain ponderosa pine) (10). Arizona pine (P. arizonica), sometimes classified as a variety of ponderosa pine (12,36,51), is presently recognized as a separate species (45).
General: Pine Family (Pinaceae). Ponderosa pine is a large tree that lives 300 to 600 years and reaches heights of 30 to 50 m tall and 0.6 to 1.3 m in diameter. The oldest trees can exceed 70 m in height and 2 m in diameter. The bottom one-half of the straight trunk is typically without branches. The crown of ponderosa pine is broadly conical to round-shaped. The bark is characteristically orange-brown with a scaly plate-like appearance. Twigs are stout, up to 2 cm think, orange-brown, and rough. Needles are 12 to 28 cm long, thin and pointed with toothed edges, occur in bundles of three, and give a tufted appearance to the twig. Buds are up to 2 cm long, 1 cm wide, red-brown with white-fringed scale margins. Male cones are orange or yellow and are located in small clusters near the tips of the branches. The female cone is oval, woody, 8 to 15 cm long, with a small prickle at the tip of each scale. Flowering occurs from April to June of the first year, and cones mature and shed winged seeds in August and September of the second year.
Distribution: Ponderosa pine is distributed from southern British Columbia through Washington, Oregon, and California, and east to the western portions of Texas, Oklahoma, Nebraska, North Dakota, and South Dakota. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site (http://plants.usda.gov).
Habitat: Ponderosa pine trees occur as pure stands or in mixed conifer forests in the mountains. It is an important component of the Interior Ponderosa Pine, Pacific Ponderosa Pine-Douglas fir, and Pacific Ponderosa Pine forest cover types.
In the northwest, it is typically associated with Rocky Mountain Douglas fir, lodgepole pine, grand fir, and western larch. In California it is associated with California white fir, incense cedar, Jeffrey pine, sugar pine, coast Douglas fir, California black oak, and western juniper. In the Rocky Mountains and Utah, it is associated with Rocky Mountain Douglas fir, blue spruce, lodgepole pine, limber pine, and quaking aspen. In the Black Hills, it is associated with quaking aspen, white spruce, and paper birch. In Arizona and New Mexico, it is associated with white fir, Rocky Mountain Douglas fir, blue spruce, quaking aspen, gamble oak, and southwestern white pine at higher elevations and Rocky Mountain juniper, alligator juniper, and Utah juniper at lower elevations (Oliver & Riker 1990).
Shrubs and grasses typically associated with ponderosa pine within its range include ceanothus, sagebrush, oak, snowberry, bluestem, fescue, and polargrass.
Big heavy, black jack, bull pine, ponderosa white pine, Sierra brown bark pine, silver pine, western pitch pine, western red pine, western yellow pine, yellow pine, Yosemite pine.
Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: Ponderosa pine is the most widely distributed pine species in North America, ranging north-south from southern British Columbia to central Mexico and east-west from central Nebraska to the west coast (Howard 2003).
Pacific ponderosa pine (var. ponderosa) ranges from latitude 52° N. in the Fraser River drainage of southern British Columbia, south through the mountains of Washington, Oregon, and California, to latitude 33° N. near San Diego. In the northeast part of its range it extends east of the Continental Divide to longitude 110° W. in Montana, and south to the Snake River Plain, in Idaho (1,51).
Rocky Mountain ponderosa pine (var. scopulorum) extends east of the Continental Divide from latitude 48° N. in north-central Montana, southeasterly into North and South Dakota, eastern Wyoming, and as far east as north-central Nebraska. Within this area, ponderosa pine grows on the discontinuous mountains, plateaus, canyons, and breaks of the plains, with the most extensive stands found in the Black Hills of South Dakota and Wyoming (51). South of Wyoming, Rocky Mountain ponderosa pine extends south on both sides of the Continental Divide, west to Arizona, and the eastern edge of the Great Basin in Nevada, east to Texas west of the Pecos River, New Mexico, extreme northwestern Oklahoma, Colorado, and northern Mexico (36). Within this wide range, ponderosa pine is absent from a large area that includes southwestern Montana, western Wyoming, southern Idaho, and part of the Great Basin (12,61). A possible explanation for the absence is that the distribution of rainfall during the summer months prevents seedling establishment except at higher elevations, where the species has little tolerance for the shorter growing season (61).
Arizona pine (var. arizonica) is found primarily in the mountains of extreme southwestern New Mexico, southeastern Arizona, and northern Mexico (36).
- The native range of ponderosa pine.
The USDA hardiness zones for ponderosa pine range from 3 to 7. It grows on a variety of soils from shallow to deep, and from gravelly sands to sandy clay loam. It is found growing on bare rock with its roots in the cracks and crevices. It has a low tolerance to alkalinity, preferring soils with a pH of 6.0 to 7.0. It grows best in zones with 30 to 60 cm average annual precipitation on well-drained soils. Once established it also survives hot and dry conditions, exhibiting medium to good drought tolerance. Fifty percent shade reduces the growth rate significantly. It withstands very cold winters.
Ponderosa pine is a climax species at the lower elevations of the coniferous forest and a mid-successional species at higher elevations where more competitive conifers are capable of growing. It generally grows at elevations between sea level and 3,000 m. The populations at higher elevations usually occur within the southern part of its range (Oliver & Riker 1990).
Puget Lowland Forests Habitat
Cope's giant salamander is found in the Puget lowland forests along with several other western North America ecoregions. The Puget lowland forests occupy a north-south topographic depression between the Olympic Peninsula and western slopes of the Cascade Mountains, extending from north of the Canadian border to the lower Columbia River along the Oregon border. The portion of this forest ecoregion within British Columbia includes the Fraser Valley lowlands, the coastal lowlands locally known as the Sunshine Coast and several of the Gulf Islands. This ecoregion is within the Nearctic Realm and classified as part of the Temperate Coniferous Forests biome.
The Puget lowland forests have a Mediterranean-like climate, with warm, dry summers, and mild wet winters. The mean annual temperature is 9°C, the mean summer temperature is 15°C, and the mean winter temperature is 3.5°C. Annual precipitation averages 800 to 900 millimeters (mm) but may be as great as 1530 mm. Only a small percentage of this precipitation falls as snow. However, annual rainfall on the San Juan Islands can be as low as 460 mm, due to rain-shadow effects caused by the Olympic Mountains. This local rain shadow effect results in some of the driest sites encountered in the region. Varied topography on these hilly islands results in a diverse assemblage of plant communities arranged along orographically defiined moisture gradients. Open grasslands with widely scattered trees dominate the exposed southern aspects of the islands, while moister dense forests occur on northern sheltered slopes characterized by Western red cedar (Thuja plicata), Grand fir (Abies grandis), and Sword fern (Polystichum munitum) communities.
There are only a small number of amphibian taxa in the Puget lowland forests, namely: Cope's giant salamander (Dicamptodon copei); Monterey ensatina (Ensatina eschscholtzii); Long-toed salamander (Ambystoma macrodactylum); Western redback salamander (Plethodon vehiculum); Northwestern salamander (Ambystoma gracile); Pacific chorus frog (Pseudacris regilla); Coastal giant salamander (Dicamptodon tenebrosus); Rough-skin newt (Taricha granulosa); the Vulnerable Spotted frog (Rana pretiosa); Tailed frog (Ascopus truei); and Northern red-legged frog (Rana aurora).
Likewise there are a small number of reptilian taxa within the ecoregion: Common garter snake (Thamnophis sirtalis); Western terrestrial garter snake (Thamnophis sirtalis); Northern alligator lizard (Elgaria coerulea); Western fence lizard (Sceloporus occidentalis); Northwestern garter snake (Thamnophis ordinoides); Sharp-tailed snake (Contia tenuis); Yellow-bellied racer (Coluber constrictor); and Western pond turtle (Clemmys marmorata).
There are numberous mammalian taxa present in the Puget lowland forests. A small sample of these are:Creeping vole (Microtus oregoni), Raccoon (Procyon lotor), Southern sea otter (Enhydra lutris), Mink (Mustela vison), Coyote (Canis latrans), Black-tailed deer (Odocoileus hemionus), Pallid bat (Antrozous pallidus), and Harbour seal (Phoca vitulina).
A rich assortment of bird species present in this ecoregion, including the Near Threatened Spotted owl (Strix occidentalis), Turkey vulture (Cathartes aura), Bald eagle (Haliaeetus leucocephalus), Blue grouse (Dendragapus obscurus), as well as a gamut of seabirds, numerous shorebirds and waterfowl.
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: Ponderosa pine occurs on a wide variety of soils, usually in open areas as it is intolerant of shade. Trees can grow in pure stands, especially at lower elevations where subject to frequent forest fires, or in mixed stands with Douglas-fir and western larch at higher elevations.
Soils and Topography
Its distribution on drier sites is related closely to supplies of available soil moisture which, in turn, are related to soil textures and depth (13,20,22). In Wyoming, for instance, at the lower limits of coniferous forest, ponderosa pine is found only on coarse-textured soils of sandstone origin where the limited moisture is more readily available than on fine-textured soils of limestone origin (27). In Oregon and Washington, higher survival and growth rates of ponderosa pine have been reported for coarse-textured sandy soils than for fine-textured clayey soils (20).
Ponderosa pine stands, 51, 75, and 78 years old, growing in coarse-, medium-, and fine-textured soils in Montana, had their greatest root development in the medium-textured soils and the least in the fine-textured soils. Root concentration was more uniform in the medium-textured soils and concentration dropped off abruptly below a soil depth of 46 cm (18 in) in the fine-textured soils (13).
Depending on the locality and the horizon of the samples, soils vary from pH 4.9 to pH 9.1. The pH in the surface horizon frequently is from 6.0 to 7.0 (13).
Foliar concentrations of nitrogen and phosphorus needed for adequate growth are low in ponderosa pine compared with the associated conifers in California-Douglas-fir (Pseudotsuga menziesii), white fir (Abies concolor), sugar pine (Pinus lambertiana), and incense-cedar (Libocedrus decurrens). Foliar concentrations of 0.9 percent for nitrogen and 0.08 percent for phosphorus mark critical boundaries between nutrient deficiency and sufficiency (42). Correcting nitrogen deficiency in California and central Oregon stands has increased volume growth 30 percent (50). Because critical levels of foliar nitrogen and phosphorus are lower in ponderosa pine, while early biomass gains generally are greater, this species is judged superior in satisfying its nutritional needs on soils that by other species' standards are infertile.
Ponderosa pine is found at elevations from sea level to 3050 m (10,000 ft). From north to south the species grows at progressively higher altitudes and within more restricted elevational limits (1, 13,20,67). In Washington, the elevations for ponderosa pine are sea level to 1220 m (4,000 ft); in the Blue Mountains of northeastern Oregon, 910 to 1520 m (3,000 to 5,000 ft); in the south-central Oregon pumice area, 1460 to 2010 m (4,800 to 6,600 ft); in the northern Rocky Mountains, from 300 to 1830 m (1,000 to 6,000 ft); in the middle Rockies up to 2590 m (8,500 ft); and in the southern Rockies, up to 3050 m (10,000 ft). In California, ponderosa pine is usually found at elevations from 150 to 1070 m (500 to 3,500 ft) in the north, and from 1610 to 2230 m (5,300 to 7,300 ft) in the south.
The extent of the seasonal rainfall deficiency is evident from the July and August precipitation, usually about 25 mm (1 in) or less; in some places, as in California, July and August precipitation is often lacking. Except on coarse-textured soils, summer showers probably provide scant moisture useful to young seedlings. Total growing season precipitation may mean little because of the distribution pattern (13).
Regardless of the location where ponderosa pine grows, average annual temperatures are between 5° and 10° C (41° and 50° F), and average July-August temperatures are between 17° and 21° C (62° and 70° F). Average frost-free seasons for ponderosa pine range from 90 to 154 days in eastern Montana and South Dakota (1,63) to more than 200 days in central California. Annual extremes are from -40° to 43° C (-40° to 110° F).
Habitat & Distribution
Site preparation is needed to control competition, which compromises seedling survival and growth. Seeds are sown in late March to early April. The seed is sown for an initial density of 237 seedlings/m2 (22 seedlings/ft2). Transplant stock should be one or two years old, with less than 2 prior transplantings, and 15 to 30 cm in height. Space the plants 1 to 3 m apart depending on the site.
Initial seedling survival is reduced under moisture stress. Older seedlings can tolerate limited moisture. Competition from other vegetation should be controlled for the first three to six years until the trees become well established.
aecium of Coleosporium asterum parasitises live Pinus ponderosa
Foodplant / parasite
pycnium of Cronartium flaccidum parasitises live branch of Pinus ponderosa
Associated Forest Cover
Fires have had a profound effect on the distribution of ponderosa pine. Although the seedlings are readily killed by fire, larger trees possess thick bark, which offers effective protection from fire damage. Competing tree species, such as grand fir (Abies grandis) and Douglas-fir, are considerably less fire tolerant, especially in the sapling and pole size classes. Ponderosa pine, therefore, was able to maintain its position as a dominant seral species on large areas of middle-elevation forests in the West. Because of successful fire control during the past 50 years, many of these stands have developed understories of Douglas-fir and true firs. Type conversion has been accelerated by harvest of the ponderosa pine, leaving residual stands composed of true fir, Douglas-fir or lodgepole pine (Pinus contorta var. latifolia) (15,20). In the Pacific Northwest, forest cover types on about 2 million ha (5 million acres) are believed to have changed in the last 25 years (3).
Ponderosa pine is an integral component of three forest cover types in the West: Interior Ponderosa Pine (Society of American Foresters Type 237), Pacific Ponderosa Pine-Douglas-Fir (Type 244), and Pacific Ponderosa Pine (Type 245) (18). Interior Ponderosa Pine is the most widespread type, covering most of the range of the species from Canada to Mexico, and from the Plains States to the Sierra Nevada, and the east side of the Cascade Mountains. Ponderosa pine is also a component of 65 percent of all western forest cover types south of the boreal forest.
Major associated tree species are as follows:
Northwest. Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca), lodgepole pine, grand fir, and western larch (Larix occidentalis).
California. California white fir (Abies concolor var. lowiana), incense-cedar, Jeffrey pine (Pinus jeffreyi), sugar pine, coast Douglas-fir (Pseudotsuga menziesii var. menziesii), California black oak (Quercus kelloggii), and western juniper (Juniperus occidentalis).
Rocky Mountains and Utah. Rocky Mountain Douglas-fir, blue spruce (Picea pungens), lodgepole pine, limber pine (Pinus flexilis), and quaking aspen (Populus tremuloides).
Black Hills. Quaking aspen, white spruce (Picea glauca), and paper birch (Betula papyrifera).
Arizona and New Mexico. White fir (Abies concolor var. concolor), Rocky Mountain Douglas-fir, blue spruce, quaking aspen, Gambel oak (Quercus gambelli), and southwestern white pine (Pinus strobiformis) at higher elevations; Rocky Mountain juniper (Juniperus scopulorum), alligator juniper (J. deppeana), and Utah juniper (J. osteosperma) at lower elevations.
Genera of understory vegetation frequently found in ponderosa pine forests are as follows:
Shrubs. Arctostaphylos, Ceanothus, Purshia, Artemisia, Quercus, Rosa, Prunus, Spiraea, Symphoricarpos, Physocarpus, and Berberis.
Grasses. Agropyron, Andropogon, Bouteloua, Festuca, Muhlenbergia, and Poa.
Community composition varies widely with geographic location, soils, elevation, aspect, and successional status. Specific information is available in descriptions of various habitat and community type classifications (1,20,23,27,35,47,61,63).
Diseases and Parasites
At least 108 species of insects attack P. ponderosa var. ponderosa, and 59 species attack P. ponderosa var. scopulorum (13). The most damaging of the tree-killing insects are several species of Dendroctonus. Trees die from the combined effects of a blue stain fungus transmitted by the beetle and extensive larval consumption of the phloem. The western pine beetle (D. brevicomis) is a common cause of mortality in overmature, decadent trees within the range of ponderosa pine from Baja California, north into Oregon, Washington, western Canada, Idaho, and western Montana. During epidemics, however, apparently healthy, vigorous trees are also killed. During the drought years of the 1930's, losses from western pine beetle in the Pacific Northwest were so heavy that many foresters feared for the pine stands' continued existence. The mountain pine beetle (D. ponderosae) is the most destructive and aggressive enemy in the central and southern Rocky Mountains. During the 1894-1908 outbreak in the Black Hills of South Dakota, this insect killed between 5.7 and 11 million m³ (1 and 2 billion/fbm) of ponderosa pine (13). Tree killing by D. ponderosae has increased with the conversion of old-growth to young-growth stands in the Pacific Northwest. High stand density is believed to reduce vigor of some of the larger trees in a stand and, therefore, is an underlying factor in the occurrence of bark beetle outbreaks. D. adjunctus, D. approximatus, and D. valens are other species of the genus that often kill ponderosa pines.
Among bark beetles, Ips species are second in destructiveness only to Dendroctonus (21). Ips are present naturally in all stands, where they usually breed in slash. In abundant slash from forestry activities, Ips can kill vigorous ponderosa pine up to 66 cm (26 in) in d.b.h. when populations reach explosive levels. Eleven species of Ips have been found attacking ponderosa pine. Of these, I. latidens, I. emarginatus, I. pini, I. lecontei, and I. paraconfusus have the most impact.
Several insects mine buds and shoots, primarily of young trees. Although seldom killed, trees are retarded in growth when infestations are severe. Pine tip moths (Rhyacionia spp.) and the gouty pitch midge (Cecidomyia piniinopis) kill the buds and shoots they mine. A more insidious pest, until recently overlooked and overrated, is the western pineshoot borer (Eucosma sonomana) (21). Larvae of this species bore within the pith of the terminal shoot, stunting but seldom killing them. Shoots that are potentially more robust are more likely to be infested than are weaker shoots. Accordingly, direct comparisons of infested vs. uninfested shoot lengths will underestimate actual growth loss. Each terminal shoot infested by a larva that developed to maturity was reduced in length that year by more than 25 percent in one study (59).
The pine reproduction weevil (Cylindrocopturus eatoni), a native of California and, presumably, Oregon, can be a threat to slow-growing plantations. Its impact has declined, however, with the improvement in planting stock and control of competing vegetation.
Defoliating insects, such as the pine butterfly (Neophasia menapia) and the pandora moth (Coloradia pandora), periodically cause damage over extensive areas. The pine needle sheathminer (Zelleria haimbachi) can be locally severe in young stands.
Dwarf mistletoe (Arceuthobium vaginatum ssp. vaginatum in the Southwest, and A. campylopodium in California and the Northwest) is ponderosa pine's most widespread disease, absent only in the Black Hills (25). It seems to be particularly devastating in the Southwest, where it infects trees on about one-third of the commercial acreage. At Fort Valley Experimental Forest in northern Arizona, dwarf mistletoe has caused up to 36 percent of the mortality (55). On trees not killed, the parasite is responsible for a significant loss in growth, primarily in height, and is reported to reduce seed viability as much as 20 percent. In the Northwest, A. campylopodium has little effect on vigorous, young trees because height growth will usually exceed its upward spread, relegating the parasite to the lower crown (5).
Several diseases attack ponderosa pine roots. Black stain root disease [Leptographium (syn. Verticicladiella) wageneri] causes a diffuse dark staining of the root wood and kills roots (6). Heterobasidion annosum causes an insidious lethal root disease that is spread by airborne spores to the surfaces of freshly-cut stumps. It and L. wageneri kill trees of all ages and usually result in group mortality that is sometimes mistaken for the work of bark beetles, which are frequently secondary invaders. Armillaria sp., previously considered weak root and butt decayers, are causing increased mortality in young plantations and thinned stands where the disease can build up in dead root systems (3). Active infection centers of L. wageneri and H. annosum spread about 1 m (3 ft) per year. The rate is usually less for Armillaria sp.
The most damaging heart rot in the southern Rocky Mountains and the Black Hills is western red rot caused by Dichomitus squalens (25). It is a major cause of loss of sound wood in commercial stands. Because ponderosa pines older than 100 years have substantially greater defect, shorter rotation ages should eliminate much of the heart rot. Phellinus pini is the major heart rot in the Pacific Coast States.
A needle cast, Elytroderma deformans, found throughout ponderosa pine's wide range, is the most serious foliage disease (6). It is unique among the needle casts in being perennial and in its capacity to infect the host twigs, which enables it to maintain its populations even under adverse environmental conditions. Although less destructive than the alarming appearance of affected trees suggests, it can slow growth and kill trees of sawtimber size. Bark beetles are prompt to attack infected trees. Severe damage from E. deformans was reported on the Ochoco National Forest in Oregon, where 555,900 m³ (98,148,000 fbm) of dying and dead trees were removed from 1946 to 1950 (13).
Several rusts of the Cronartium coleosporioides complex are damaging to ponderosa pine. Locally, especially in the Southwest, limb rust (Peridermium filamentosum) attacks middle or upper crowns of mature trees, killing branches in both directions as it spreads (46). The western gall rust (Endocronartium harknessii) attacks ponderosa pine from the Black Hills to the Pacific Northwest (25). It infects all ages, resulting in round and pear-shaped galls, distortions, and trunk lesions. Young trees may be killed. Comandra blister rust (Cronartium comandrae) is found in all states west of the Rocky Mountains but is most common in California, Idaho, Montana, Utah, and Wyoming. It causes scattered mortality in well-stocked sapling and small pole stands. In thinned stands, however, the disease may cause substantial damage (3).
Air pollution is an increasing and vexing source of foliar damage to ponderosa pine. Ozone is the major plant-damaging constituent of photochemical oxidant air pollution. Ozone becomes concentrated enough to cause damage near the border of air basins and in the predominant summer downwind direction from heavily populated areas. Because ponderosa pine, especially var. ponderosa, is susceptible, and because it grows near areas heavily polluted, ozone damage can be great. Typical injury is a chlorotic mottling accompanied by premature abscission of old needles (6). Moderately or severely injured trees are attacked more frequently by bark beetles and Heterobasidion annosum root disease (28).
Basal fire scars are common on the thick-barked stems in old-growth ponderosa pine forests. Uncontrolled fire was common before European colonization. These surface fires consumed branches, fallen trees, understory vegetation, and some living trees. The fires burned from 1 to 47 years apart, with most at 5- to 20-year intervals (3). Low-intensity fires kept many pine forests open and parklike. They also helped to maintain ponderosa pine in areas where more tolerant climax species would have attained dominance, because saplings or larger-sized ponderosa pine are more fire resistant than many of the true firs and Douglas-fir.
Survival and growth of ponderosa pine usually are affected little if 50 percent or less of the crown is scorched in a fire. Six years after a fire in Arizona, however, no poles and only 5 percent of the sawtimber-size trees were living if more than 60 percent of the crown had been destroyed (13). Low tree vigor and cambium damage increase the likelihood of mortality. Vigorous young trees have survived, on occasion, when 100 percent of their crowns were scorched. Because buds are protected by thin long scales, late season fires cause less mortality. Continued accumulation of food reserves after diameter growth ceases in late summer also increases the ability of the tree to withstand fire injury. When crowns are scorched, young, fast-growing trees on good sites have the best chance of survival and old, slow-growing trees on poor sites the poorest chance.
Snow often injures saplings and larger trees. Stem bending and breaking from unusually wet snowfalls that overload tree crowns can seriously damage dense pole-size stands (49). Stem deformation by snow pressure and movement on mountain slopes is a threat to sapling stands (38), especially where ponderosa pine is planted above its optimum elevational limit.
Reaction to Competition
Because of ponderosa pine's intolerance of shade, it tends to grow in even-aged stands and is usually managed by that method. Uneven-aged stands might appear common throughout the drier portion of its range but are in reality a mosaic of even-aged groups. Ponderosa pines lose vigor in dense stands. On drier sites in the Pacific Northwest, trees in pole-size stands with basal area stand densities above 34.4 m²/ha (150 ft²/acre) become subject to attack by bark beetles (54).
Ponderosa pine remains physiologically young and responds to release up to age 200 in Arizona. Elsewhere, stagnated sapling stands 70 to 100 years old usually respond to thinning and seem to grow as rapidly as unstagnated trees, when crowns grow to sufficient size to take advantage of the additional growing space (3,7).
Mature ponderosa pines put down a root to depths of more than 2 m (6 ft) in porous soils, but seldom more than 1 m (3 ft) in heavy clay soils. Exceptions occur in soils underlain by rock with deep fissures, where roots have been observed along cut banks at depths of 11 to 12 m (35 to 40 ft). In open stands, lateral roots may extend 46 m (150 ft). In dense stands, however, they are limited more to the crown width. The main mass of roots is concentrated within the top 60 cm (24 in) of the soil mantle.
Life History and Behavior
Germination of ponderosa pine is epigeal (31). Moisture stress reduces seed germination as well as initial seedling survival and growth. In an Arizona study, seed germination, root penetration, root dry weight, and cotyledon length decreased as the stress increased beyond 0.7 MPa (7 bars) (55). Older seedlings, however, are able to cope with limited moisture supplies by reducing transpiration and by vigorously extending their root systems. Transpiration rate declines at soil water potentials of -0.1 to -0.2 MPa (-1 to -2 bars). At -1.0 MPa (-10 bars) the transpiration rate is only 12 percent of maximum (37). Ponderosa pine has the capacity for root growth in relatively dry soil. Nursery stock lifted in January in California had appreciable root elongation even when planted in soil with a water potential of less than -0.9 MPa (-9 bars) (62) and has survived, at least for short periods, water potentials of less than -8.0 MPa (-80 bars) in the Southwest (24).
The significance of competing vegetation as a deterrent to early survival and development of young seedlings has been clearly demonstrated. In central Idaho, soil moisture remained above the wilting point at depths below 15 cm (6 in) on areas free of competing vegetation throughout the growing season but dropped to or below that critical point on most vegetated plots (13). In loamy soils in the White Mountains in Arizona, drought is normally not a major variable in seedling survival beyond age 2, except where there is grass cover (30). Shrub competition reduced the height and diameter growth of ponderosa pine planted in northern California (43); similar growth reductions have been reported for stands in Oregon (4).
Air and soil temperatures often affect growth. Seedlings grown from seed collected in Arizona, California, and South Dakota had the best root growth in 15° C (59° F) air temperature and 23° C (73° F) soil temperature. Height growth was greatest at 23° C (73° F) temperature for air and soil (33).
On the western slopes of the Sierra Nevada, height growth of ponderosa pine started significantly later with each increase of 610 m (2,000 ft) in elevation, and the length of the growing season was significantly shorter with a 910 m (3,000 ft) increase in elevation. Rates of height and radial growth did not vary with elevation during the period of growth. At an elevation of 1520 m (5,000 ft), a 6-year average showed that ponderosa pine started radial growth on March 23 and height growth on April 26. The period of radial growth lasted 177 days; that of height growth, 97 days. Ponderosa pine started height growth before sugar pine, incense-cedar, and white fir, but not before lodgepole pine (13).
Many variables cause seedling mortality. Ponderosa pine seedlings less than 36 days old were more susceptible to minimum night temperatures (lower than -5° C (23° F)) than were lodgepole pine seedlings. But by 2 months of age, differences in tolerance did not exist (8). During winters with little snow cover, 1- and 2-year-old seedlings suffered damage and killing from frost. In the Southwest, natural regeneration on fine-textured soils is almost non-existent because of frost-heaving (24). Damage is lessened by heavy cover and early summer germination of seeds, which gives a longer establishment period. Ordinarily, older seedlings are hardy in severe winter temperatures, but occasionally they suffer "winter killing" of foliage (a desiccation process) if the temperature drops suddenly when drying winds and frozen ground are present. Also, 1- to 3-month-old seedlings are killed by stem temperatures of about 54° C (130° F) and higher. Ponderosa pine is more successful in resisting high soil surface temperature with increasing age; 110-day-old seedlings can successfully withstand instantaneous temperatures of 58° to 82° C (136° to 180° F) (13). Also, it can withstand higher temperatures than its associates in the Northwest-Douglas-fir, grand fir, and Engelmann spruce (Picea engelmannii) (56).
Seed Production and Dissemination
In eastern Washington, Idaho, and western Montana, 16 species of insects have been identified as causing seed losses of ponderosa pine (14). They destroyed up to 95 percent of the cone crop, but most areas sampled suffered losses ranging from 30 to 60 percent. In central Arizona, abortion, ponderosa pine cone beetles (Conophthorus ponderosae), and ponderosa pine coneworms (Dioryctria sp.) were the three most important causes of cone mortality (57). Usually the proportion of seeds lost to insects is highest when crops are small.
Ponderosa pine seeds are consumed by a great many birds and small mammals such as mice, chipmunks, and tree squirrels. In years of low cone production, the potential seed crop may be severely reduced. Squirrels clip many of the cone bearing twigs, destroying flowers and conelets (13).
Specific gravity of cones containing ripe seed can be predicted. Cone collectors should consult local authorities before picking, however, because specific gravity of ripe cones varies from 0.80 in Arizona to 1.00 in the Black Hills.
The number of seeds per cone varies greatly among regions and ranges from only 31 seeds in northern Arizona (55) to 70 in central California (13). Weight of cleaned seeds varies from 15,200 to 50,700/kg (6,900 to 23,000/lb) and averages 26,500/kg (12,000/lb) (31).
Ponderosa pine seeds are not disseminated naturally over extensive distances. In central Oregon, seedfall at 37 m (120 ft) was only 22 percent of the seedfall at the west edge of a cleared area, and at 120 m (396 ft) it was only 8 percent (3). Nearly all seeds are disseminated by early November. In a good seed year as many as 852,050 seeds per hectare (345,080/acre) may reach the ground (19).
Flowering and Fruiting
In Colorado, at 2710-m (8,900-ft) elevation, during a 9-year period, female conelets emerged on or about June 18 and only about 36 percent of them survived until the beginning of the second year. Flowering is correlated closely with the passing of freezing weather (13).
Growth and Yield
Diameter growth can be rapid and remain fairly constant for long periods provided trees are given adequate growing space. In California, on productive sites, free-growing trees can reach 66 cm (26 in) in d.b.h. in 30 years or 22 cm. (8.7 in) per decade (data on file at Pacific Southwest Forest and Range Experiment Station, Redding, CA). In central Oregon, where sites are less productive, trees 13 to 51 cm (5 to 20 in) in d.b.h. and from 19 to 36 years old can grow 12 cm (4.9 in) in d.b.h. per decade if free of intertree competition (3). Trees in a virgin stand in Arizona grew 29 mm (1.14 in) on the average during a 10-year period, but trees in a cutover stand grew 43 mm (1.68 in) (55).
Vegetative competition can restrict diameter growth markedly whether it be from neighboring trees or understory shrubs. In the central Oregon study, trees completely surrounded by understory shrubs grew only 9 cm (3.5 in) per decade. Those trees with no competitive ground cover averaged 12 cm (4.7 in) of growth per decade. In California on a droughty, skeletal soil, severe shrub competition reduced diameter growth to less than half that of competition-free trees. Insect damage, which was greater on the trees competing with shrubs, accounted for some of the growth depression (44). Stagnation in diameter, and often in height, represents a serious problem in densely stocked stands throughout the species' range, but especially on poor sites.
Height growth is most rapid in the pole and young sawtimber size classes to about 60 years. In the Pacific Northwest, dominant trees in stands of moderate density grow from 0.24 to 0.46 m (0.8 to 1.5 ft) annually between the ages of 20 to 60 years on timber-producing sites (2). Rate of growth declines gradually at older ages. Arizona trees of 160 years or older (determined at breast height) grow little in height (55). Height growth increases with site productivity and is more sensitive to stand density than was once believed.
Representative yields of ponderosa pine from a normal yield table for sites of various productivities are given in table 1 (39). For extensive natural stands, table values should be reduced by 25 percent or more because of roads, rock outcrops, steep slopes, openings, and other unproductive areas.
Table 1- Total volume inside bark of ponderosa pine 1.5 cm (0.6 in) and larger in d.b.h. (39) Site index at base age 100 years¹ Age 18 m or 60 ft 27 m or 90 ft 37 m or 120 ft 46 m or 150 ft yr m³/ha 20 28 94 168 262 40 122 238 396 588 60 192 340 570 861 80 238 413 696 1060 100 273 472 794 1204 120 308 518 868 - 140 336 556 928 - yr ft³/acre 20 400 1,350 2,400 3,750 40 1,750 3,400 5,650 8,400 60 2,750 4,850 8,150 12,300 80 3,400 5,900 9,950 15,150 100 3,900 6,750 11,350 17,200 120 4,400 7,400 12,400 - 140 4,800 7,950 13,250 - ¹Height of dominant and codominant trees of average d.b.h. Old-growth ponderosa pine produces clear, high-grade lumber, but young trees typically are limby. Natural pruning develops slowly. An average clear length of only 3.5 m (11.5 ft) was recorded in 250-year-old stands in central Idaho (13).
Molecular Biology and Genetics
Within var. scopulorum, the Rocky Mountain race comprises the northeast portion of the species' range. It is characterized by compact foliage, 2-needle fascicles, and better growth in trials east of its natural range. The Rocky Mountain race joins the Southwestern race along a broad, ill-defined front through southern Colorado, Utah, and Nevada. The Southwestern race has relatively open foliage, low proportions of 2-needle fascicles, and resins with distinctive monoterpene composition.
Results from a provenance study of 45-year-old trees in northern Idaho and a study of 30-year-old trees in Oregon and Washington (60) showed that 36 percent of the variation in the height of the trees was associated with seed source. A clinal variation was evident in the increase of height from sources in an east-to-west direction. This variation was related to September-through-June precipitation. Clinal variation in a latitudinal and altitudinal direction was related to April-May temperatures. Incidence of animal damage and of frost injury was related, also, to seed source.
Ponderosa pine varies markedly in its resistance to cold. In a test of 298 individual tree progenies planted in Michigan, all 2-year-old seedlings of California origin suffered severe injury from cold (66). Progenies from British Columbia, Washington, eastern Oregon, Arizona, and southern New Mexico suffered light damage. No damage was reported for progenies from the remainder of the species' range. Essentially the same pattern was found in the northern Idaho study in 10- to 15-year-old trees (65).
Elevational. variation has been studied intensively in central Idaho (53) and in California (9). On the west slope of the Sierra Nevada in California, seeds collected from trees growing at elevations of 40 to 2130 m (125 to 7,000 ft) were planted at altitudes of 290, 830, and 1720 m (950, 2,730, and 5,650 ft) above sea level. The general trend was that early growth was most rapid for mid-elevation sources and least rapid for high-elevation sources, regardless of the elevation of the plantation. But by 29 years, at the high-elevation plantation, sources from high elevations had overtaken sources from low elevations and had nearly caught up to sources from middle elevations. Middle and low elevation sources, especially the latter, suffered stem and leader damage from snow and wind, which significantly reduced their growth superiority. Wood specific gravity decreased with increasing elevation of parent source regardless of where the source was planted (16). No elevational effect was discerned in tracheid length, although individual differences were found. Differences were recognized, also, in total height and diameter, and in the seasonal growth pattern (42) for families within elevational zones. Genetic diversity among populations, both in California and central Idaho, was readily interpretable as adaptive variation. Results of both studies suggest that for selective breeding of a wide-ranging species with distinct elevational differentiation, such as ponderosa pine, superior progenies can be obtained from selection within the optimum elevational zone of best geographic sources. In central Idaho, the recommended elevational zone is ± 180 m (600 ft).
Hybrids Natural crosses of ponderosa pine with Jeffrey pine have been observed in California where their ranges overlap, but they are rare. Where the two species grow in the same stand, different flowering times and other reproductive barriers restrict crossing (11). Ponderosa pine crosses with Pinus montezumae and P. arizonica, and rarely with P. engelmannii (45). Introgressive hybridization has been observed with P. washoensis.
In addition to the natural hybrids, artificial crosses have been obtained with a number of other hard pine species, including P. durangensis.
Barcode data: Pinus ponderosa
Statistics of barcoding coverage: Pinus ponderosa
Public Records: 8
Specimens with Barcodes: 35
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1998Lower Risk/least concern (LR/lc)
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Widely distributed in mountainous regions from British Columbia far into Mexico (including northern Sonora and Chihuahua) and from California to Nebraska, in many places forming great forests. Grows in rather open forests, but forms fairly dense stands on the higher slopes. Harvested for timber, particularly in northern Sonora and Chihuahua where it occurs between 6000 and 8000 ft alt. As a native, long-lived tree species, few populations may be showing some decline, especially from increased severity of fire events and overharvesting in some areas, however the species is still considered common and wide-ranging.
Global Long Term Trend: Unknown
Comments: Pinus ponderosa arid-forest communities are predicted to expand into areas currently occupied by other conifer and grassland communities (Joyce et al. 2001).
Comments: Dwarf mistletoe (Arceuthobium spp.) is a serious disease of ponderosa pine with infection rates up to 33% in some areas (Howard 2003). Dwarf mistletoe alters tree form, suppresses growth, and reduces volume and overall wood quality of its host (Epp & Tardif 2004). Mountain pine beetles (Dendroctonus ssp.) and bark beetles (Ips spp.) are also serious pests of ponderosa pine with regular infestations occurring over centuries of time. However, beetle epidemics combined with environmental conditions such as prolonged drought has resulted in increased pine mortality in many regions (Howard 2003). Older age classes of ponderosa pine are being lost from stands (Howard 2003), however this doesn't represent a loss in genetic diversity in tree species (Hamrick 2004).
Pests and potential problems
Approximately 200 insect species affect ponderosa pine from its cone stage to maturity. Pine cone beetles cause tree death by transmitting blue stain fungus to the tree. Their larvae also consume the phloem, restricting the flow of nutrients to the top of the tree.
Western pine beetle is a common cause of death for older trees, drought stressed trees, and even healthy, vigorous trees during epidemics.
Bark beetles are naturally present in all stands. Harvesting methods that leave large amounts of logging slash can allow bark beetle populations to explode and kill vigorous trees up to 0.5 m in diameter.
The ponderosa pine budworm, also known as the sugar-pine tortrix, eats new needles on trees in New Mexico and Colorado. Several years’ worth of damage will affect the health of the tree. Early research suggests that some insecticides may help to control infestations.
Dwarf mistletoe is the most widespread parasite that causes branch and stem deformation. It germinates on ponderosa pine branches and forces its roots into the phloem of the host branch, creating stem cankers that leave the wood weak and unsuitable for use as lumber. This weakens the tree and leaves it susceptible to fungal infections and insect attacks. Root diseases, rusts, trunk decays, and needle and twig blights also cause significant damage.
Biological Research Needs: More research still is needed on how forest management can reduce the incidence and spread of disease and pests. Research should be conducted if harvest intensity is exceeding capacity for regrowth.
Cultivars, improved and selected materials (and area of origin)
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Ponderosa pine is propagated by seed. Cones are ready for collection in October and November when they turn reddish brown. Mature seed is firm and brown in color. Cones should be dried on canvas tarp in a well-ventilated area immediately after they have been collected. The seeds will drop from the cones as they dry.
Several germination methods for ponderosa pine have been utilized, each with their own variations. In general, seeds undergo an imbibation treatment before stratification. Seeds are placed in mesh bags and soaked in cold running water for 48 hours. One variation is to soak the seeds in a 40% bleach solution for 10 minutes with hand agitation prior to placing them under running water. The mesh bags are place in plastic bags and stored at 1oC for 2 to 8 weeks. They should be checked daily for mold. Seeds are sown into containers and covered with media. The media should be kept moist throughout germination. Germination will occur at an average greenhouse temperature of 20oC. Alternating greenhouse temperatures of 21-25oC during the day and 16-18oC at night is an appropriate environment for germinating seeds. Germination will occur in approximately 15 days.
Seedlings are thinned and watered daily throughout the establishment phase. They should not be moved outdoors until after the last frost of the year.
Seeds can be dried to between 5 and 8% moisture and placed in airtight plastic bags, then stored for long periods of time in freezers set at –15oC.
Ponderosa pine can be over-irrigated in poorly drained soils, or drowned out on high water table sites.
It responds well to thinning, which should be done as stands become older to develop larger crowns, resulting in heavier seed crops for wildlife. More forage for deer and elk become available from associated plants by opening the canopy. The use of repellents or other control measures may be necessary to prevent overuse of the trees by rodents.
Ponderosa pine is resistant to fire due to its thick bark. Low intensity surface fires control competitive species like scrub oak and shade-tolerant conifers. Ponderosa pine seedlings can also survive low intensity burns.
Relevance to Humans and Ecosystems
Uses: FIBER, Building materials/timber
Comments: One of the most important timber trees of northern Sonora and Chihuahua (Record and Hess, 1943).
Erosion control: Ponderosa pine is a rapid growing tree with the ability to firmly anchor into most soil types. For this reason, it is suitable for use as a windbreak species. It can also be used with other natives to provide cover and erosion control on rehabilitated sites.
Ethnobotanic: Native Americans used various parts of ponderosa pine for medicinal, building and
household, food, and ceremonial purposes. Needles were used as dermatological and gynecological aids.
They were also used to reduce coughs and fevers. The pitch was used as an ointment for sores and scabby skin, backaches, rheumatism, earaches, inflamed eyes, and as a sleeping agent for infants. The boughs of the plant were used in sweat lodges for muscular pain, as decoctions for internal hemorrhaging, and as infusions for pediatric treatments.
The roots of ponderosa pine were used to make blue dye and needles were used as insulation for underground storage pits. The wood was used extensively for fence posts, boards for general construction, and to fabricate snowshoes. Single logs were used to make dugout canoes. Bark was used to cover houses.
Most parts of the plant were used for food, including the pitch, seeds, cones, bark, buds, and cambium. The pollen and needles were used in healing ceremonies.
Ornamental value: Ponderosa pine has a lush green color and pleasant odor that makes it popular for ornamental plantings. It has been planted, sometimes out of its natural range, because of its aesthetic qualities. Ponderosa pine is used as borders of forested highways, but is not planted within the right-of-way. The large stature of the tree limits its use to open spaces.
Wildlife: Red-winged blackbirds, chickadees, mourning doves, finches, evening grosbeak, jays, Clark's nutcracker, nuthatches, rufous-sided towhee, turkeys, chipmunks and squirrels consume the seeds of ponderosa pine. Blue and spruce grouse use ponderosa pine needles for nesting material. Mice, porcupines, and other rodents use the bark for nesting material. The trees are also important to various birds for cover, roosting and nesting sites.
Wood production: Ponderosa pine is one of the most important timber species in the western United States. The annual production of ponderosa pine is ranked third behind Douglas fir and hem-fir. Approximately 1.3 billion board feet of ponderosa pine lumber is produced annually out of Oregon, the largest supplier in the United States. It is popularly used for the construction of buildings.
Willamette Valley Ponderosa Pine
The Willamette Valley Ponderosa Pine is a variant of the Ponderosa Pine native to the Willamette Valley in the Northwestern United States. It is adapted for Western Oregon's wet winter and dry summer.
The Willamette Valley ponderosa variant only grows on the valley floor, unlike the Douglas fir, which grows on hillsides, and the wood is softer and easier to mill than the native hardwoods. Because of this, when early settlers used wood from the trees to build homes and cleared land for agriculture, the variant's population was "decimated". Prior to restoration efforts, the pine survived only in scattered stands between Hillsboro and Cottage Grove. The Lewis's woodpecker and the slender-billed nuthatch (a subspecies of the white-breasted nuthatch) nest in the tree and rely on it for food–their populations were reduced along with that of the pine.
- Ryan, Catherine (March 28, 2012). "Loggers Give Unique Oregon Ponderosa Pine a Lifeline". High Country News. Retrieved March 12, 2015.
- The Nature of Cedar Mill: Willamette Valley Ponderosa Pine
- Ponderosa Returns to the Willamette Valley
- Bark Beetles and Willamette Valley Ponderosa Pine: Populations, Geographical Distribution and Management Recommendations
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Pinus ponderosa, commonly known as the ponderosa pine, bull pine, blackjack pine, or western yellow pine, is a very large pine tree species of variable habitat native to the western United States and Canada. It grows in various erect forms from British Columbia southward and eastward through 16 western states and has been successfully introduced in temperate regions of Europe. It was first seen and collected in 1826 in eastern Washington near present-day Spokane. On that occasion, David Douglas misidentified it as Pinus resinosa (red pine). In 1829, Douglas concluded that he had a new pine among his specimens and coined the name Pinus ponderosa for its heavy wood. In 1836, it was formally named and described by Charles Lawson, a Scottish nurseryman. It is the official state tree of Montana.
P. ponderosa is a large coniferous pine (evergreen) tree. The bark helps to distinguish it from other species. Mature to over-mature individuals have yellow to orange-red bark in broad to very broad plates with black crevices. Younger trees have blackish-brown bark, referred to as "blackjacks" by early loggers. Ponderosa pine's five subspecies, as classified by some botanists, can be identified by their characteristically bright, green needles (contrasting with blue-green needles that distinguish Jeffrey pine). The Pacific subspecies has the longest—19.8 cm or 7.8 in—and most flexible needles in plume-like fascicles of three. The Columbia ponderosa pine has long—12.0–20.5 cm or 4.7–8.1 in—and relatively flexible needles in fascicles of three. The Rocky Mountains subspecies has shorter—9.2–14.4 cm or 3.6–5.7 in—and stout needles growing in scopulate (bushy, tuft-like) fascicles of two or three. The Southwestern subspecies has 11.2–19.8 cm or 4.4–7.8 in, stout needles in fascicles of three (averaging 2.7–3.5). The central high plains subspecies is characterized by the fewest needles (1.4 per whorl, on average); stout, upright branches at narrow angles from the trunk; and long green needles—14.8–17.9 cm or 5.8–7.0 in—extending farthest along the branch, resembling a fox tail. Needles are widest, stoutest, and fewest (averaging 2.2–2.8) for the species.
Sources differ on the scent of P. ponderosa, but it is more or less of turpentine, reflecting the dominance of terpenes (alpha- and beta-pinenes, and delta-3-carene). Some state that it has no distinctive scent.
The National Register of Big Trees lists a ponderosa pine that is 235 ft (72 m) tall and 324 in (820 cm) in circumference. In January 2011, a Pacific ponderosa pine in the Rogue River–Siskiyou National Forest in Oregon was measured with a laser to be 268.35 ft (81.79 m) high. The measurement was performed by Michael Taylor and Mario Vaden, a professional arborist from Oregon. The tree was climbed on October 13, 2011, by Ascending The Giants (a tree climbing company in Portland, Oregon) and directly measured with tape-line at 268.29 ft (81.77 m) high. This is now the tallest known pine. The previous tallest known pine was a sugar pine.
This species is grown as an ornamental plant in parks and large gardens.
Use in nuclear testing
During Operation Upshot–Knothole in 1953, a nuclear test was performed in which 145 ponderosa pines were cut down by the United States Forest Service and transported to Area 5 of the Nevada Test Site, where they were planted into the ground and exposed to a nuclear blast to see what the blast wave would do to a forest. The trees were partially burned and blown over.
Ecology and distribution
P. ponderosa is a dominant tree in the Kuchler plant association, the Ponderosa shrub forest. Like most western pines, the ponderosa generally is associated with mountainous topography. However, in Nebraska it is found on banks of the Niobrara River. Scattered stands occur in the Willamette Valley of Oregon and in the Okanagan Valley and Puget Sound areas of Washington. It is found in the Black Hills of South Dakota; on foothills and mid-height peaks of the northern, central, and southern Rocky Mountains; in the Cascade Range; in the Sierra Nevada; and in the maritime-influenced Coast Range. In Arizona, it predominates on the Mogollon Rim and is scattered on the Mogollon Plateau and on mid-height peaks in Arizona and New Mexico. It does not extend into Mexico.
P. ponderosa needles are the only known food of the caterpillars of the gelechiid moth Chionodes retiniella. Blue stain fungus, Grosmannia clavigera, is introduced in sapwood of P. ponderosa from the galleries of all species in the genus Dendroctonus.
Modern forestry research has identified five different taxa of P. ponderosa, with differing botanical characters and adaptations to different climatic conditions. Four of these have been termed "geographic races" in forestry literature. Some botanists historically treated some races as distinct species. In modern botanical usage, they best match the rank of subspecies and have been formally published.
- Pinus ponderosa subsp. critchfieldiana Robert Z. Callaham subsp. novo (Pacific ponderosa pine)
- Range & climate: western coastal parts of Washington State; Oregon west of the Cascade Range except for the southward-extending Umpqua–Tahoe Transition Zone; California except for both that transition zone and the Transverse-Tehahchapi Mountains Transition zone in southern California and Critchfield's far Southern California Race. Mediterranean hot, dry summers in California; mild wet winters with heavy snow in mountains.
- P. ponderosa subsp. ponderosa Douglas ex C. Lawson – (Columbia ponderosa pine).
- Range & climate: southeast British Columbia, eastern Washington State and Oregon east of the Cascade Range, Arizona, northwestern Nevada, Idaho and west of the Helena, Montana, transition zone. Cool, relatively moist summers; very cold, snowy winters (except in the very hot and very dry summers of central Oregon, most notably near Bend, which also has very cold and generally dry winters).
- P. ponderosa subsp. scopulorum (Engelm. in S.Watson) E. Murray, Kalmia 12:23, 1982 (Rocky Mountains ponderosa pine).
- Range & climate: east of the Helena, Montana, transition zone, North & South Dakota, but not the central high plains, Wyoming, Nebraska, northern and central Colorado and Utah, and eastern Nevada. Warm, relatively dry summers; very cold, fairly dry winters.
- Pinus ponderosa subsp. brachyptera Engelm. (Southwestern ponderosa pine)
- Range & climate: Four corners transition zone including southern Colorado, southern Utah, northern and central New Mexico and Arizona, westernmost Texas, and a single disjunct population in the far northwestern Oklahoma panhandle. The Gila Wilderness contains one of the world's largest and healthiest forests. Hot with bimodal monsoonal rainfall; wet winters and summers contrast with dry springs and falls; mild winters.
- Pinus ponderosa subsp. readiana Robert Z. Callaham subsp. novo (Central High Plains ponderosa pine)
- Range & climate: southern South Dakota and adjacent northern Nebraska and far eastern Colorado, but neither the northern and southern high plains nor the Black Hills, which are in subsp. scopulorun. Hot, dry, very windy summers; continental cold, wet winters.
Distributions of the subspecies in the United States are shown in shadow on the map. Distribution of ponderosa pine is from Critchfield and Little. The closely related 5-needled Arizona pine (Pinus arizonica) extends southward into Mexico.
Before the distinctions between the North Plateau race and the Pacific race were fully documented, most botanists assumed that ponderosa pines in both areas were the same. When a botanist and a geneticist from California found in 1948 a distinct tree on Mt. Rose in western Nevada with some marked differences from the ponderosa pine they knew in California, they described it as a new species, Washoe pine Pinus washoensis. However, subsequent research proved this to be merely one of the southern-most outliers of the typical North Plateau race of ponderosa pine.:30–31
An additional variety, tentatively named P. ponderosa var. willamettensis, found in the Willamette Valley in western Oregon, is rare. This is likely just one of the many islands of Pacific subspecies of ponderosa pine occurring in the Willamette Valley and extending north to the southeast end of Puget Sound in Washington.
|Common name||Pacific||Columbia||Rocky Mountains||Southwestern||Central High Plains|
|Years needles remain green||3.9±0.25, N=30||4.7±0.14, N=50||5.7±0.28, N=23||4.3±0.18, N=24||4.7±0.18, N=5|
|Foliage length on branch (cm)||25.1±2.4, N=30||26.2±2.2, N=50||21.1±1.7, N=23||21.8±2.7, N=24||42.2±6.7, N=5|
|Needle length (cm)||19.8±0.44, N=30||16.8±0.29, N=48||11.2±0.27, N=23||14.7±0.45, N=24||15.6±0.57, N=5|
|Needles per fascicle||3.0±0.00, N=30||3.0±0.00, N=48||2.6±0.06, N=23||3.0±0.03, N=24||2.4±0.11, N=5|
|Needle thickness||45.9±0.49, N=30||47.8±0.51, N=48||46.4±0.68, N=23||44.8±0.87, N=24||49.7±0.61, N=5|
|Branches per whorl||4.4±0.13, N=30||3.7±0.11, N=50||3.0±0.17, N=23||3.4±0.25, N=23||2.3±0.11, N=5|
|Branch angle (° from vertical)||56±1.8, N=30||51±1.7, N=50||50±2.3, N=23||48±3.1, N=24||36±1.9, N=5|
|Seed cones length (mm)||101.4±2.48, N=25||88.7±1.24, N=36||70.7±2.20, N=22||74.9±2.51, N=20||71.1±2.46, N=5|
|Seed cones width (mm)||77.1±1.35, N=25||71.6±0.73, N=36||61.5±1.08, N=22||62.6±1.77, N=20||63.3±2.18, N=5|
|Seed cone form W/L||0.80±0.03, N=25||0.84±0.03, N=36||0.90±0.02, N=22||0.86±0.02, N=20||0.90±0.03, N=5|
|Seed length (mm)||7.5±0.08, N=23||7.6±0.16, N=14||6.3±0.09, N=17||6.4±0.18, N=16||7.0±0.12, N=5|
|Seed width (mm)||4.9±0.05, N=23||4.9±0.08, N=14||4.1±0.05, N=17||4.3±0.09, N=16||4.5±0.10, N=5|
|Seed + wing length (mm)||32.3±0.58, N=23||24.8±0.62, N=14||22.9±0.63, N=17||23.3±0.68, N=15||23.1±0.78, N=5|
|Mature cone color||apple green to yellow green||green & red-brown to dk. purple||green & red-brown to dk. purple||green & red-brown to dk. purple|
Names of taxa and transition zones are on the map.
Numbers in columns were derived from multiple measurements of samples taken from 10 (infrequently fewer) trees on a varying number of geographically dispersed plots.
Numbers in each cell show calculated mean ± std. error and number of plots.
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Ponderosa pine ( Pinus ponderosa ) is the state tree of Montana.
Names and Taxonomy
Comments: The taxonomy of the ponderosa pine complex is not completely resolved (Flora of North America 1993). There are morphological and distributional overlaps, and disagreement regarding the geographical boundaries of varieties of ponderosa pine. Hybridization also occurs between all three varieties. (Howard 2003).