Pinus edulis

Pinyon pine

Pinaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Coniferophyta (conifers). Class - Pinopsida. Order - Pinales. Family - Pinaceae (pine). Genus - Pinus L. Species - Pinus edulis Engelm.

Ecology: Pinyon pine is intolerant of shade in all but the seedling stage of its growth. "Nurse plants" are sometimes required during this stage to protect the seedlings from excessive drying and heating. Pinyon-juniper stands have slow succession rates. Pinus edulis occurs as an early to late-seral or climax species. The general successional recovery after fire in dense stands of pinyon-juniper begins with the establishment of annuals, a stage that may peak in the 2nd and 3rd postfire years. A perennial grass stage follows, in which perennials are more abundant than annuals, with a shrub stage developing soon after. The re-establishment of trees during the shrub stage then leads to the pinyon-juniper climax, presuming no further fire occurrence. The edible seeds of Pinus edulis are gathered from native stands and marketed commercially.

Identification

Trees dioecious, to 20 m, single-stemmed (rarely multistemmed); crown conic to occasionally rounded. Bark brown, exfoliating in thin strips, that of small branchlets (5--10 mm diam.) smooth, that of larger branchlets exfoliating in plates. Branches spreading to ascending; branchlets erect to flaccid, 3--4-sided in cross section, ca. 2/3 or less as wide as length of scalelike leaves. Leaves light to dark green but often glaucous blue or blue-gray, abaxial gland elliptic, conspicuous, exudate absent, margins entire (at 20 and 40); whip leaves 3--6 mm, not glaucous adaxially; scalelike leaves 1--3 mm, not overlapping to overlapping by not more than 1/5 their length, keeled to rounded, apex obtuse to acute, appressed or spreading. Seed cones maturing in 2 years, of 2 distinct sizes, generally with straight peduncles, globose to 2-lobed, 6--9 mm, appearing light blue when heavily glaucous, but dark blue-black beneath glaucous coating when mature (or tan beneath glaucous coating when immature), resinous to fibrous, with (1--)2(--3) seeds. Seeds 4--5 mm.

Threats

Fire effects: Mature Pinus edulis trees are short with open crowns, but they do not self-prune their dead branches. The accumulated fuel in the crowns, thin bark, and the relative flammability of the foliage make individual trees susceptible to fire. Fire opens pinyon-juniper stands, increases diversity and productivity in understory species, and creates a mosaic of stands of different sizes and ages across the landscape. In addition, fire maintains the boundaries between the woodlands and adjacent shrub- or grasslands. Where stand-replacing fires do occur and potential seed sources are removed, dispersal of Pinus edulis seeds by animals becomes particularly important in the reestablishment of tree seedlings.

Reproduction

Seed Production - The pollen of Pinus edulis is carried for miles by the wind. Pinus edulis is generally monoecious. The upper crown of Pinus edulis tends to bear more ovulate than staminate cones and the opposite is true of the lower crown, though there may be broad overlap. Some dioecious individuals do occur. Pinus edulis may start bearing cones at 25 years. Good seed production occurs on trees that are 75 to 100 years old, with maximum seed production occurring on trees 160 to 200 years of age. Large seed crops are produced every 3 to 7 years and are adversely impacted by water stress.

Seedling Establishment - In general, Pinus edulis has short-lived seeds. As a result, seeds form only a temporary seed bank, with most seeds germinating the spring following dispersal. Pinus edulis seeds generally germinate in the shade of a tree or shrub rather than in open grassland. Germination occurs in response to moisture and moderate temperatures of 18-24 deg C. It occurs in the spring after snowmelt and/or warming temperatures. Reproduction of Pinus edulis is generally sparse and scattered due to removal of seeds by birds and mammals, and seedling establishment is dependent on chance dispersal to favorable sites and ample rainfall.

Vegetative Regeneration - none.

Species Distribution

Citation

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

Flora of North America
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

Silvics of North America
Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA.

USGS Plant Species Range Maps
Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97. Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.