Pinus ponderosa description

Pinus ponderosa

Douglas ex Lawson et C.Lawson 1836

Common names

Ponderosa pine, yellow pine, pino real, pinabete (Elmore and Janish 1976); western yellow, bull, black Jack, western red, western pitch, big, heavy, Sierra brownbark, western longleaf or ponderosa white pine (Peattie 1950); pin à bois lourd (Kral 1993).

Taxonomic notes

Discovered by David Douglas in 1826 near what is now Spokane, Washington (Little 1980) and described by Lawson in 1836. Since that time, the taxonomy of the ponderosa complex has been the subject of continuing dispute. The classification used here is sufficiently distinctive that it has not yet received formal description, but it does represent the fruits of considerable scholarship conducted by Lauria (1991, 1996a, 1996b) and Frankis (previously unpublished).

Forestry studies indicate the existence of four distinct taxa termed 'races' (Weidmann 1939, Critchfield 1984, Conkle and Critchfield 1988) or 'ecotypes' (Wells 1964). These taxa are morphologically distinct (Lauria 1991, 1996a, 1996b) and would normally be treated as subspecies, but most have not been formally described at this rank. They have all been described at species rank in the past. The following names, not all of which have been formally published, here used here:

P. ponderosa subsp. ponderosa. The 'North Plateau' group includes populations formerly assigned to P. washoensis H. L. Mason & Stockwell (which is arguably a distinct taxon at the varietal rank), as well as those conventionally assigned to P. ponderosa subsp. ponderosa from British Columbia, western Montana, Idaho, and Washington, Oregon, California & Nevada east of the Cascades crest.

P. ponderosa subsp. benthiama (not published). The 'Pacific' group includes populations formerly assigned to Pinus benthamiana Hartweg (1847) from the Sierra Nevada and west of the Cascade crest in California, Oregon and Washington.

P. ponderosa subsp. brachyptera (not published). The 'South Rockies' group includes populations formerly assigned to Pinus brachyptera Engelmann (1848) from Arizona and New Mexico. In the far south of those states, it is replaced by Pinus arizonica (q.v.).

Pinus ponderosa subsp. scopulorum (Engelmann) E. Murray. The 'North Rockies' group, currently-described, is widely distributed to the east and north of the above-named taxa.

Description

Trees to 18-39(72) m with 80-120(250) cm diameter, 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 2 cm thick), orange-brown, aging darker orange-brown, rough. Buds ovoid, to 2 cm, 1 cm broad, red-brown, very resinous; scale margins white-fringed. Needles 2-5 per fascicle, spreading to erect, persisting (2)4-6(7) years, 7-25(30) cm × (1)1.2-2 mm, 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 1.5-3 cm, base persistent. Staminate cones ellipsoid-cylindric, 1.5-3.5 cm, yellow or red. Ovulate 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, 5-15 cm, 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)4-9 mm, brown to yellow-brown, often mottled darker; wing 15-25 mm (Little 1980, Kral 1993).

Range

Canada: S British Columbia, E to US: SW North Dakota, S to trans-Pecos Texas and W to S California; also in Mexico: Baja California and Sonora (Little 1980, Kral 1993). Mostly in the mountains, in pure stands or mixed conifer forests (Little 1980). See also Thompson et al. (1999).

Ponderosa pine presents one of the best examples of the superb adaptation to wildfire that characterizes much of the genus Pinus. Studies in the Gila Wilderness area of Arizona and New Mexico have found that due to frequent summer lightning storms and the accumulation of pine needles on the forest floor, low intensity surface fires may travel through ponderosa stands with an average frequency of once every three years. These frequent burns discourage competitive species such as scrub oak and shade tolerant conifers. Adult ponderosa are unharmed by such fires due to their thick, fire resistant bark, while ponderosa seedlings also have an excellent chance of surviving these low-intensity burns. In the historical period, an enthusiastic program of fire suppression has virtually eliminated these small, frequent fires. As a consequence, shrubs and shade-tolerant conifers have invaded many ponderosa stands while thick accumulations of highly combustible fuels have built up on the forest floor. Now, when a fire does occur, it is likely to be extremely destructive, destroying vast stands of prime forest. Since the mid-1970s, some forest managers have attempted to reintroduce low intensity fire to this ecosystem, but their efforts are often thwarted both by a "Smokey the Bear" mentality ingrained in the public mind, and by the high cost of monitoring prescribed fire in an ecosystem that has accumulated high fuel loads.

The same problem can also be viewed from a historical perspective. Early travelers in the West often commented on the vast, parklike stands of ponderosa pine that they encountered. There are tales of stands of giant trees separated by grassy swards, with no other understory vegetation. Many of these stands were so open and level that a carriage could easily be driven through them, and some writers report stands of this character so extensive that they took days to ride across. Such a stand is shown in the photograph at left, taken in the woods near Whitney, Oregon in about 1900. That forest was logged over long ago. It is still possible to see such a forest, but to do so you must go to Mexico, specifically to the Sierra San Pedro Martír in Baja California. Thot is a forest of Pinus lambertiana, Pinus jeffreyi, Pinus coulteri and Abies concolor var. lowiana, but the open character and giant trees are highly reminiscent of pioneer accounts of Pinus ponderosa forests of the West. Interestingly, very similar accounts describe early historical forests of Pinus palustris in the southeastern U.S., although the trees were not so massive as those seen in the photograph at left. In each of these forests, the giant trees and open understory were a legacy of frequent, low-intensity fire that excluded competitors, discouraged root rot fungi, and maintained an optimum growing environment for the dominant canopy tree species.

Big tree

See subspecies benthamiana.

Oldest

Very similar maximum ages are attained in subspecies scopulorum and ponderosa.

Dendrochronology

Ethnobotany

The most commercially important western pine (Little 1980). Extensive harvest has eliminated vast acreages of old growth ponderosa.

Observations

See the subspecies descriptions.

Remarks

This is the most widely distributed and common pine in North America. Quail, squirrels and many other kinds of wildlife consume the seeds, and nutcrackers and chipmunks cache them, thereby helping to bring forth new pines (Little 1980).

Although it is currently the most abundant pine in the west, Ponderosa may have been virtually absent from the west during the glacial and pluvial climates that characterized most of the Pleistocene epoch. In these periods, which account for 80 to 90 percent of the last two million years, ponderosa has only been found to occur along the Mogollon Rim in central Arizona. However, the morphological and genetic diversity of the species suggests that other Pleistocene refugia are likely to have occurred in California and probably elsewhere.

Ponderosa pine (Pinus ponderosa) is the state tree of Montana (Kral 1993).

Citations

M.P. Frankis contributed much to the development of this page in Dec-1998.