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Why Does Jeffrey Pine Grow Here

Jeffrey Pine

Pinus jeffreyi

Jeffrey pine was discovered in 1852 in the Shasta Valley of California by Scottish botanist, John Jeffrey. It was first classified as a variety of ponderosa pine due to its physical resemblance and the similarity of its geographic range. Although it is closely related to ponderosa pine and produces wood of equal structure and quality, it is a distinct species which can be distinguished from ponderosa pine based on its bark, needles, buds, and cones.

Jeffrey pine may live 400 to 500 years and can attain immense size. On the best sites, individuals typically grow to 4 to 6 feet in diameter and 170 to 200 feet in height. The largest Jeffrey pine recorded in the western Sierra Nevada had a diameter of 7.5 feet and a height of 175 feet.

Range

Jeffrey pine is found primarily in California. It extends north through the Klamath Mountains into southwestern Oregon, across the Sierra Nevada into western Nevada, and south to the Transverse and Peninsular Ranges and into northern Baja California.

Jeffrey pine grows well on harsh and infertile sites. It is tolerant of drought, like ponderosa pine but is better adapted to cold weather since it requires a shorter growing season. These characteristics allow it to grow well and out-compete other conifers on cold, dry, or infertile sites.

Jeffrey pine grows in a diverse range of climatic conditions. Cold winters largely determine its presence in the Klamath, western Sierra Nevada, and southern California ranges. Precipitation, which falls mostly in the winter season, ranges from as little as 15 inches per year in the eastern Sierra to 60 inches in the western Sierra and Klamath ranges. Jeffrey pine can occupy many sites from the edges of moist, high mountain meadows to arid slopes bordering deserts. It also grows over a wide range of elevations. Since it is cold hardy, Jeffrey pine competes well at high elevation sites, while its drought tolerance allows it to occupy drier, low-elevation, infertile sites.

Jeffrey pine grows on a wide variety of well-drained soils which are derived from many parent materials. In the northwest portion of its range, Jeffrey pine is found primarily on infertile soils. Typical infertile soils are mostly shallow and fine, fine-loamy, and clay-textured gravelly surface soils. It can be found at elevations as low as 200 feet.

In the northeast, central, and southern portions of its range, climate and elevation determine its distribution, rather than soil type. Jeffrey pine typically grows on granitic and volcanic soils in the Sierra Nevada, with coarse soil texture, as gravelly sandy loams or loamy coarse sands. Jeffrey pine grows at elevations from 1,600 to over 9,000 feet.

Regeneration

Jeffrey pine regenerates sexually through seed production over a two-year cycle. Trees flower in June and July of the first year, and cones mature in the summer of the second year. Most seeds are shed in September and October. Seeds typically fall only about 100 feet from the parent tree, although fall storms with high winds may carry seeds up to 1/2 mile away.

On the west side of the Sierra Nevada, seed crops are borne every 2 to 8 years. Trees may start to bear cones as early as eight years old, but typical seed bearers are 30+ years old and 60 to 180 feet tall. Seeds are both disseminated and eaten by insects, birds, and small mammals such as mice, chipmunks, and tree squirrels. Seeds germinate quickly in the spring.

Regeneration of Jeffrey pine by seed or replanting may fail due to poor seedbeds, sparse seed crops, poor seed dissemination, seed predators, cutworms, and diseases. Seedlings establish most successfully on bare mineral soil. A major cause of regeneration failure is competition for moisture from other vegetation. Heavy competition from brush, grasses, and sedges for soil water can be lethal to Jeffrey pine seedlings in the dry summer period, while shade from shrubs can slow growth of surviving seedlings.

In plantations, Jeffrey pine grows less rapidly than ponderosa pine during the sapling stage but more rapidly in the pole stage, thus, balancing out over time. On the best sites, Jeffrey pine can grow to impressive size. By contrast, stand productivity is low for Jeffrey pine on infertile sites, sometimes growing sparse stands in which 300-year-old trees are less than 100 feet tall.

Growth

Volume yield data specific to Jeffrey pine have not been collected. Because of similarities with ponderosa pine, including the assumption that it grows to the same age and maximum size, ponderosa pine volume figures are used.

Jeffrey pine responds well to silvicultural treatments. A study in northeastern California found Jeffrey pine's average diameter and height growth increased 167 and 62 percent respectively during the first 5 years after thinning. Removal of brush, grasses, and sedge in one northeastern California plantation increased average growth of poles by 38 percent in one five-year period.

Jeffrey pine has a deep, vigorous taproot in its juvenile through mature stages. Lateral roots are strong and extensive and may grow to distances greater than tree height. Because of its vigorous root system, the tree is considered wind firm compared to other associated species. Because Jeffrey pine grows in a wide range of soil and climate types, it is associated with many other tree and understory species.

Jeffrey pine typically occurs in pure stands along the eastern slope of the Sierra Nevada. It predominates on south slopes with granitic soils and outnumbers ponderosa pine in the eastern Sierra Nevada, the Transverse and Peninsular ranges. In the northern Sierra Nevada and into the southern Cascade Range, it occurs in more mixed stands with ponderosa pine, incense cedar, white fir, and western juniper.

Jeffrey pine is moderately resistant to fire and shares many of the same adaptations to fire as ponderosa pine. Seedlings regenerate well on bare mineral soil cleared of litter by fire. Although seedlings are killed by fire, larger trees possess thick, corky bark and thick bud scales that withstand high temperatures and protect the tree from fire damage. Its open crown and erect bole free of lower limbs, which might form a fuel ladder, also minimize damage to mature trees in low-severity fires in well-spaced stands. Damaged Jeffrey pine trees are very susceptible to insect damage.

Fire has a profound influence on the distribution of Jeffrey pine. In the past, frequent low-intensity fires kept many pine forests open and park like and helped to maintain Jeffrey and ponderosa pine in areas where more shade-tolerant species would have predominated.

Jeffrey pine is shade intolerant and only occasionally regenerates beneath a canopy. Because of this intolerance to shade, Jeffrey pine often grows in even-aged patches which are vulnerable to overcrowding. Thinning of one 55-year-old stand with 11,000 eight-foot saplings per acre tripled diameter growth and increased height growth 67 percent in 5 years.

As with ponderosa pine, nearly every even-aged and uneven-aged silvicultural system has been applied to Jeffrey pine management, with variable levels of success. Treatments that allow full sunlight for regeneration and adequate room for growth are the most successful.

Damaging Agents

Squirrels, mice, voles, and birds help to disseminate Jeffrey pine seed, consuming large amounts of seed in the process. Biological agents attacking Jeffrey pine include two needle diseases, a limb canker, at least five different rusts, three root diseases and various heart rots. The worst disease of Jeffrey pine is caused by western dwarf mistletoe.

Insects that damage Jeffrey pine are as numerous as diseases. They include twig and needle scales, defoliators, borers, and tip moths, bark beetles, and cone and seed feeders. The Jeffrey pine beetle, which is common throughout its range, is the single worst enemy of the Jeffrey pine and has caused extensive mortality in mature stands. Weather extremes and human activity can also be damaging.

Uses

Jeffrey pine pitch was distilled for turpentine early in the century. The primary use now is for lumber. Low-grade trees are processed into dimensional lumber and other products for the construction market. High-grade lumber is an important raw material for molding, mill work, cabinets, doors, and windows. For commercial use, no distinction is made between the wood of Jeffrey pine and ponderosa pine.

Jeffrey pine forests are also important for providing wildlife cover for birds, small mammals and big game. The species has exhibited potential for revegetation of acid mine waste sites in northeastern California. It was found to be well adapted to a sulfur mine spoil site that was high in acidity and low in nitrogen availability.

This text was largely summarized from an article originally by James L. Jenkinson Plant Physiologist, USFS Pacific Southwest Forest and Range Experiment Station, Berkeley, CA.that appears in Burns, Russell M., and Barbara H. Honkala, tech. coords. 1990. Silvics of North America: 1. Conifers. Agriculture Handbook 654. U.S. Department of Agriculture, Forest Service, Washington, DC. vol. 1, 675 p.

Interested readers are referred to the original article for more detailed and technical information and references

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Publication of this series was in part funded by the
California Department of Forestry and Fire Protection
under Contract numbers 8CA96027 and 8CA96028

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