Pinus ponderosa

Pinaceae -- Pine family

    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.

The range of ponderosa pine extends from southern Canada into Mexico,  and from the Plains States of Nebraska and Oklahoma to the Pacific Coast.

    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.

Pinus ponderosa P. Lawson & C. Lawson:
Mexico (Mesoamerica)
United States (North America)
China (Asia)
Canada (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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).

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).

Trees to 72m; trunk to 2.5m diam., straight; crown broadly conic to rounded. Bark yellow- to red-brown, deeply irregularly furrowed, cross-checked into broadly rectangular, scaly plates. Branches descending to spreading-ascending; twigs stout (to 2cm thick), orange-brown, aging darker orange-brown, rough. Buds ovoid, to 2cm, fully 1cm broad, red-brown, very resinous; scale margins white-fringed. Leaves 2--5 per fascicle, spreading to erect, persisting (2--)4--6(--7) years, 7--25(--30)cm ´ (1--)1.2--2mm, slightly twisted, tufted at twig tips, pliant, deep yellow-green, all surfaces with evident stomatal lines, margins serrulate, apex abruptly to narrowly acute or acuminate; sheath 1.5--3cm, base persistent. Pollen cones ellipsoid-cylindric, 1.5--3.5cm, yellow or red. Seed cones maturing in 2 years, shedding seeds soon thereafter, leaving rosettes of scales on branchlets, solitary or rarely in pairs, spreading to reflexed, symmetric to slightly asymmetric, conic-ovoid before opening, broadly ovoid when open, 5--15cm, mostly reddish brown, sessile to nearly sessile, scales in steep spirals (as compared to Pinus jeffreyi ) of 5--7 per row as viewed from side, those of cones just prior to and after cone fall spreading and reflexed, thus well separate from adjacent scales; apophyses dull to lustrous, thickened and variously raised and transversely keeled; umbo central, usually pyramidal to truncated, rarely depressed, merely acute, or with a very short apiculus, or with a stout-based spur or prickle. Seeds ellipsoid-obovoid; body (3--)4--9mm, brown to yellow-brown, often mottled darker; wing 15--25mm.

Tree, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds resinous, Leaves needle-like, Leaves alternate, Needle-like leaf margins finely serrulate (use magnification or slide your finger along the leaf), Leaf apex acute, Leaves > 5 cm long, Leaves < 10 cm long, Leaves > 10 cm long, Leaves yellow-green above, Leaves yellow-green below, Leaves not blue-green, Needle-like leaves somewhat rounded, Needle-like leaves twisted, Needle-like leaf habit erect, Needle-like leaves per fascicle mostly 2, Needle-like leaves per fascicle mostly 3, Needle-like leaf sheath persistent, Twigs glabrous, Twigs viscid, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones > 5 cm long, Seed cones bearing a scarlike umbo, Umbo with obvious prickle, Bracts of seed cone included, Seeds brown, Seeds yellow, Seeds winged, Seeds unequally winged, Seed wings prominent, Seed wings equal to or broader than body.

Trees to 70 m tall; trunk to 2.5 m d.b.h. in native range; bark yellow- to red-brown, deeply and irregularly furrowed into broadly oblong, scaly plates; crown broadly conical to rounded; branchlets orange-brown, aging darker, stout, rough; winter buds red-brown, ovoid, very resinous, scales white fringed at margin. Needles tufted at apex of branchlets, spreading to erect, (2 or)3(-5) per bundle, deep yellow-green, slightly twisted, 7-25(-30) cm × (1-)1.2-2 mm, pliant, stomatal lines present on all surfaces, base with persistent sheath 1.5-3 cm, margin serrulate. Seed cones solitary or rarely paired, sessile or subsessile, mostly reddish brown, broadly ovoid when open, symmetric or asymmetric, 5-15 cm, maturing in 2 years, then soon shedding seeds, leaving rosettes of scales on branchlets. Apophyses dull or lustrous, thickened, variously raised, cross keeled; umbo usually pyramidal or truncate, rarely depressed or with a reflexed prickle. Seeds brown or yellow-brown, often mottled darker, ellipsoid-obovoid, 3-9 mm; wing 1.5-2.5 cm.

Ponderosa pine grows on soils derived from igneous, metamorphic, and  sedimentary parent materials, including quartzite, argillite, schist,  shale, basalt, andesite, granite, cinders, pumice, limestone, and  sandstone. This results in a variety of soil orders including Entisols,  Inceptisols, Mollisols, Alfisols, and Ultisols on which the species is  found throughout its extensive range.

    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.

Throughout the range of ponderosa pine, soil moisture is the variable  most often limiting growth, especially in summer when rainfall is  deficient. For the east slope of the Rockies, the Black Hills, Utah, and  the Southwest, however, summer rains occur, although the Southwest  regularly experiences scanty May-June precipitation. In eastern Oregon and  Washington, average annual precipitation ranges from 355 to 760 mm (14 to  30 in), much of it snow (30). July, August, and September are dry; average  rainfall is less than 25 mm (1 in). In Montana, east of the Continental  Divide, average annual precipitation in ponderosa pine forests ranges from  280 to 430 mm (11 to 17 in), with 125 to 250 mm (5 to 10 in) received  during the May-to-August period (1). In the Black Hills of South Dakota,  average annual precipitation is 410 to 710 mm (16 to 28 in), with up to  330 mm (13 in) received from May to August (67). In northern Arizona, 150  mm. (6 in) of the total growing season precipitation of 205 mm (8 in)  occurs in July and August, after the May-June dry period. The west slope  of the northern Sierra Nevada in California, where annual rainfall reaches  1750 mm (69 in), may be the wettest area supporting ponderosa pine in any  quantity (13).

    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).

Systems

• Terrestrial

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.

Cultivated. Henan (Jigong Shan), Jiangsu (Nanjing Shi), Jiangxi (Lu Shan), Liaoning [native to W North America]

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.

Foodplant / parasite
aecium of Coleosporium asterum parasitises live Pinus ponderosa

Foodplant / parasite
pycnium of Cronartium flaccidum parasitises live branch of Pinus ponderosa

Ponderosa pine can be either a climax or a seral species (18,27,47,61).  It is a climax species at the lower limits of the coniferous forests, and  a seral species in higher elevation mesic forests where more competitive  conifers are capable of growing. In climax forests, ponderosa pine stands  often contain many small, even-aged groups rather than a true uneven-aged  structure.

    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).

Rabbits and hares injure or kill many  seedlings, and pocket gophers are especially destructive. In areas where  pocket gopher populations are high all seedlings and many saplings may be  destroyed. Squirrels and porcupines attack sapling and pole-size trees  and, although rarely killing them, deform the stems on which they feed.  Repeated browsing by deer has stunted seedlings for 50 years or more  (13,55). In the absence of regulation, sheep and cattle have damaged  reproduction by trampling, bedding, and occasional browsing (13).

    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.

In the Sierra Nevada mixed conifer type  in California, growth of advance regeneration of ponderosa pine was  compared to that of associates beneath various overstory stand densities  (data on file at Pacific Southwest Forest and Range Experiment Station,  Redding, CA). Even beneath a light overstory stand casting 47 percent  shade, ponderosa pine saplings grew only about half as rapidly as their  associates (Douglas-fir, sugar pine, white fir, and incense-cedar) and  about half of that expected for fully lighted pines. Relative to  associates elsewhere within its range, ponderosa pine is more shade  tolerant than western larch but less tolerant than grand fir and western  white pine (40). Overall, it is most accurately classed as intolerant of  shade.

    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).

The ability of ponderosa pine seedlings to grow  vigorous taproots is one reason for their tenacity on severe sites where  associated species often fail. Within a few months of germination, roots  can penetrate to depths of 50 cm (20 in) or more in loosened and watered  soil (32). This rapid root growth is essential to ponderosa pine's  apparent adaptation to the climate of the Southwest. There, seeds do not  germinate until the soil is continuously warm and moist. These conditions  are not present until summer rains begin, usually in July. Root growth was  uninhibited by grass as long as moisture was abundant (34). Taproots  penetrate to about half that depth or less under average conditions in the  field. Annually, for the next 2 years, lateral roots may double or triple  in length.

    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.

Ponderosa pine does not reproduce  naturally by vegetative methods. It can be propagated by rooting and  grafting, but success decreases rapidly when scions are taken from trees  older than 5 years (64).

Throughout ponderosa pine's range, except  in the Black Hills and the west side of the Sierra Nevada, natural  regeneration is sporadic. Successful natural regeneration is thought to be  the result of the chance combination of a heavy seed crop and favorable  weather during the next growing season. Soil texture, plant competition,  and seedbed conditions are other common determinants of survival of young  seedlings (13).

    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).

No regular periodicity has  been observed in the seed production of ponderosa pine over its entire  range. In California, west of the Sierra Nevada, medium seed crops are  borne on an average of every 2 to 3 years. The average interval between  heavy cone crops is 8 years. Good cone crops are produced every 3 years in  the Black Hills (7), every 3 to 4 years in the Southwest (55), and every 4  to 5 years in the Pacific Northwest (3). Observations over 23 years in  Montana show ponderosa pine to be a poor seeder west, and a fair seeder  east, of the Continental Divide, with only one good crop. The species  bears cones as early as 7 years and continues to produce good seeds to at  least 350 years. Seeds from trees aged 60 to 160, however, are more viable  than those of younger or older trees. In California, trees more than 64 cm  (25 in) in d.b.h. were the best producers. In central Idaho, mature and  overmature trees growing at an elevation of 1680 m (5,500 ft) produced  lower quality seeds than similar trees at 1220 m (4,000 ft), and open  grown trees produced heavier crops of larger cones than stand grown trees  (13).

    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).

Ponderosa pine is monoecious. At  pollination the male strobili, borne in short, dense clusters, are 2 to 3  cm (0.8 to 1.2 in) long and female conelets are 2.5 cm (1 in) long. In  western Montana, central Idaho, and eastern Oregon, at elevations from 910  to 1830 m (3,000 to 6,000 ft), flowering generally begins between May 1  and 10. Pollen is shed May 25 to June 15, cones reach a full size of 8 to  15 cm (3 to 6 in) July 20 to August 10 of the next year, seed is ripe  August 20 to September 5, cones begin to open September 1 to 13, and seed  is shed until November. On the east and west sides of the Sierra Nevada in  California, at an elevation of 1830 m (6,000 ft), however, cones develop  about 2 weeks later (13). In northern Arizona, near Flagstaff, pollen is  shed between June 10 and 20 (55), but at an elevation of 910 m (3,000 ft)  on the west slope of California's Sierra Nevada, pollen has been collected  as early as April 15; May 11 was average for a 7-year period. Also on the  west slope of the Sierra Nevada, pollen is shed an average of 8 days later  for each 300 m (1,000 ft) rise in elevation (13).

    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).

Ponderosa pine grows to impressive size. Stems  263 cm (103.5 in) in d.b.h. and 70.7 m (232 ft) in height have been  recorded (13). Diameters at breast height of 76 to 127 cm (30 to 50 in)  and heights of 27.4 to 39.6 m (90 to 130 ft) are common throughout most of  its range. Trees often reach ages of 300 to 600 years.

    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).

Population Differences    Ponderosa pine shows distinct geographic variations over its widespread  range. Within and between var. ponderosa and var. scopulorum,  provenance studies (51,65,66) have shown genetic variation in growth,  stem form, needle length, survival, initiation of leader growth, seasonal  pattern of root growth potential, ability to germinate under moisture  stress (41), biotic and abiotic damage (17,26,52), monoterpene production  (58), nutrient status (29,68), and isozymes (10). This wealth of  information on genetic diversity was summarized and interpreted recently  (10). It suggests that var. ponderosa consists of three major  geographic races and var. scopulorum of two major geographic  races. Within var. ponderosa, the Pacific race is found in  California northward from the Transverse Ranges and west of the Sierra  Nevada and Cascade Range into northern Oregon. Pacific race pines have  relatively large needles, cones, and seeds, and are rapid growing and  least cold hardy in tests to date. The North Plateau race extends  northward along the eastside of the Sierra Nevada and Cascade Range and  east to the Continental Divide in Montana. Like the Pacific race, it has  open, plume-like foliage, 3-needle fascicles and isozyme characteristics.  But the North Plateau race has needles with thickened layers of hypoderm  and sunken stomata, and is indistinguishable from the Rocky Mountain race  in monoterpene characteristics. Least well understood, but distinct in  monoterpene production, is the Southern California race.

    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.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Specimens with Barcodes: 35
Species With Barcodes: 1

Year Assessed

• Needs updating

Assessor/s

Reviewer/s

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

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).

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.

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 1^oC 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 20^oC. Alternating greenhouse temperatures of 21-25^oC during the day and 16-18^oC 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 –15^oC.

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.

In ponderosa pine forests, timber production, livestock grazing, and  recreation are the principal land uses. Ponderosa pine forests are found  at low elevations offering year-round recreation, and they frequently  border forest highways where esthetic values are high. They provide  habitats for various wildlife species. Abert's and Kaibab squirrels  usually live in the ponderosa pine forests (55). Snags in the mature pine  forest provide a large number of species with nesting and roosting sites.  Big game, such as deer and elk, also use the pine forests for food and  shelter.

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.