Pinus longaeva (Great Basin bristlecone pine) description

Pinus longaeva

D.K. Bailey 1970

Common names

Great Basin bristlecone pine (Lanner 1983), intermountain bristlecone pine (Kral 1993).

Taxonomic notes

Syn: P. aristata Engelmann var. longaeva (D.K. Bailey) Little (Kral 1993). Although there are no natural hybrids, artificial crosses with both P. aristata and P. balfouriana have shown some success (Critchfield 1977).

Description

Trees to 16 m tall and 200 cm dbh. Crown rounded or irregular; sometimes forms a krummholz at the alpine timberline. Bark red-brown, fissured with thick, scaly, irregular, blocky ridges. Branches contorted, pendent; twigs pale red-brown, aging gray to yellow-gray, puberulent, young branches resembling long bottlebrushes because of persistent leaves, closely spaced needle whorls, and uniform needle insertion angles. Buds ovoid-acuminate, pale red-brown, ca. 1 cm long, resinous. Leaves mostly 5 per fascicle, upcurved, persisting 10-43 years (among the longest persistence times known), 15-35 × 0.8-1.2 mm, deep yellow-green, with few resin splotches but often scurfy with pale scales. Abaxial surface lacks median groove but has 2 subepidermal resin bands. Adaxial surface is conspicuously whitened with stomata. Margins are entire or remotely and finely serrulate distally, apex bluntly acute to short-acuminate; sheath ca. 1 cm, soon forming rosette, shed early. Pollen cones cylindro-ellipsoid, 7-10 mm long, purple-red. Seed cones mature in 2 years, shedding seeds and falling soon thereafter, spreading, symmetric, lance-cylindric with rounded base before opening, lance-cylindric to narrowly ovoid when open, 6-9.5 cm long, purple, aging red-brown, nearly sessile; apophyses much thickened, sharply keeled; umbo central, raised on low buttress, truncate to umbilicate, abruptly narrowed to slender but stiff, variable prickle 1-6 mm, resin exudate pale. Seeds ellipsoid-obovoid; body 5-8 mm, pale brown, mottled with dark red; wing 10-12 mm (Kral 1993, R.M. Lanner e-mail 1999.12.20).

Distribution and Ecology

US: California, Nevada & Utah. Subalpine and at the upper (rarely, lower) treeline; elevations 1800-3658 m, median 3048 m (data from herbarium collections). Also see Thompson et al. (1999). Hardy to Zone 4 (cold hardiness limit between -34.3°C and -28.9°C) (Bannister and Neuner 2001).

Distribution; polygons are from USGS (1999) and point data represent herbarium records downloaded from the GBIF Network, edited to remove ornamental specimens and suspected incorrect locations; also, there are points (with photos) showing locations I have visited, and points representing other occurrence locations described in various sources. Click on points/polygons for further information.

Besides the interactive map shown above, Burchfield et al. (2021) have developed a distribution map of unprecedented accuracy, available HERE (accessed 2022.03.02). This maps shows not only the locations of all known groves, but also their extent. The procedures used to develop this map are detailed by Burchfield et al. (2021), which also discusses development of a habitat model for this species using MAXENT, a software package widely employed for modeling potential habitat for rare species. The distribution map also displays the modeled habitat areas, and supports the observation that the best and most extensive bristlecone occurrences (the White Mountains, Mt. Charleston, and the High Plateaux of southwest Utah) are also the areas of most extensive suitable habitat.

At many sites bristlecone pine shows a distinct preference for carbonate (limestone, dolomite or marble) substrates. An inventory of 66 sites by Taylor (2018) found 41 of those sites developed on carbonate rock substrates; moreover, at the arid sites where P. longaeva grows, even silicate substrates are likely to contain carbonates in the form of caliche. Bristlecones grow at remarkably high elevations. For example, on Wheeler Peak, Nevada, there are four timberlines - a lower timberline set by the heat and aridity of the valley floor desert, and above that, a timberline set by cold that defines the upper limits of piñon pine (Pinus monophylla) and juniper (Juniperus osteosperma). Still higher, there is a lower timberline of bristlecone pine defined by its tolerance of heat and drought, and above that is a final timberline beyond which winter's cold prevents even bristlecone from growing. To put that a bit more precisely, "January mean dewpoint temperature and February precipitation explain over 80% of the species distribution" (Burchfield et al. 2021).

Much like Pinus albicaulis, bristlecone pine largely relies on corvids, especially Clark's nutcrackers, to gather and disperse their seeds (Lanner 1988). The seed is quite large relative to its wing, and even the strong winds of the high mountains are unlikely to convey a seed to a distant and suitable seedbed.

Stringham et al. (2015) provide an excellent short review of bristlecone pine ecology, covering its autecology, community ecology, importance to wildlife, conservation status, and threats. Rather than quote the entire review, I simply refer you to it (pages 843-848).

Bristlecones have been wrapped up in the climate change debate for decades. As is true of many trees growing at their upper elevational limits, their growth is very sensitive to growing-season temperature, and their great age (discussed below) has allowed reconstruction of climate variability with precise calendar accuracy across a span of thousands of years. LaMarche and Mooney (1972) noted fluctuations in the upper timberline and documented higher timberlines 2,000 to 4,000 years earlier. LaMarche and Hirschboeck (1984) showed that by large volcanic eruptions could produce large and persistent global climate effects, demonstrable by their effects on bristlecone growth (Salzer and Hughes [2007] did further work with this idea). In 1998, climate reconstructions based on a variety of proxies, including bristlecone pines, were used to generate the famous "hockey stick" graph that produced some of the strongest evidence that had yet been published demonstrating recent global warming (Mann et al. 1998); significantly, bristlecones have lately been growing faster than ever before (Salzer et al. 2009). Anthropogenic global climate change is now a generally accepted theory, and more recent studies show that it is already a problem for bristlecones, reducing their effectiveness as competitors with Pinus flexilis (Smithers et al. 2017), besides the simple fact that for trees that grow on mountaintops, moving uphill is not an effective way to avoid a warming environment.

Remarkable Specimens

The largest known specimen is found on the northeast ridge of Mount Charleston in the Spring Mountains outside of Las Vegas, Nevada; this single-trunked tree is 368 cm dbh and 15.8 m tall (Robert Van Pelt e-mail 2004.02.04).

The oldest known living specimen is an unnamed tree, its location kept secret, but somewhere in the White Mountains of California. The tree was sampled by Schulman in the 1950s but its great age, 5,067 years, was not determined until laboratory work (counting and crossdating) was completed by Tom Harlan in 2012 (Brown 2013). The tree is quite healthy; the stated age corresponds to the growing season of 2019.

Until 2012, the oldest known tree was "Methuselah" tree, 4,789 years, age verified by crossdating, also sampled by Schulman (in 1957) with results worked up by Harlan. I'm not sure when that age was determined, but it seems likely the tree had 4,789 rings (crossdated) in the summer of 1957, in which case the tree was 4,855 years old in 2023. It is still alive.

An age of 4,844 years was determined post-mortem (after being cut down) for specimen WPM-114 from Wheeler Peak, NV. The age is largely crossdated (Brown 1996). The fact that this tree was cut down caused, as might be imagined, quite a scandal. The story can be found recounted, from different points of view, at several sites on the Internet.

Also see the page on Conifer Longevity.

Bristlecones share with a few other ancient pines the ability to adopt a strip-bark morphology. In strip-bark trees, the bark has died back from most of the tree's circumference, leaving a strip of living cambium (and bark) that usually runs up the protected leeward side of the trunk. The exposed dead wood then takes the brunt of windblown ice crystals and sand. These gradually wear away the exposed wood, and in time the tree rings that recorded the tree's youth may be entirely worn away by this process (Valmore C. LaMarche, 1985, pers. comm.). Some researchers believe the strip-bark habit is one adaptation that has allowed the bristlecones to reach such great age; by restricting their growth to a narrow strip of living tissue, they can produce a thicker annual ring in response to a given increment of annual net productivity, and thus maintain a thicker and healthier layer of cambium and sapwood.

Ethnobotany

Occasionally one finds places in the Great Basin where bristlecone pine was used by Euroamericans during the early settlement period, e.g. by prospectors and miners for housing and basic tools. Formerly, there was also some economic exploitation of Pinus flexilis as a timber species in Nevada (now remembered only in place names like White Pine County), and in some forests P. longaeva grows as a forest tree along with Pinus flexilis and Abies concolor; in these areas it may have been incidentally harvested. An example of this use is provided by Sargent (1879) who describes extensive harvest of P. longaeva on Prospect Mountain near Eureka, Nevada, formerly a site of intensive mining activity. Sargent reports "Formerly the whole summit of this mountain was very generally covered with this species, but with few exceptions the trees have all been cut to supply the mines with it, for which purpose the strong and very close-grained, tough wood of this species is preferred to that of any other Nevada tree. The specimens seen were fifteen to thirty feet high, with trunks often two feet in diameter, pyramidal in outline, their lower branches still remaining; so that at a little distance they might readily be mistaken for spruces." The only aboriginal use I have found described for P. longaeva is that the Shoshone people used a poultice of heated pitch on sores and boils (Train et al. 1941).

There is also some limited, recent use of the species in horticulture. For instance, Pinus longaeva 'Cherry Lady' is a dwarf cultivar that was originally discovered as a witches' broom by late Franz Etzelstorfer and Jörg Kohout during a 2006 trip to the USA.

The bristlecone has been an uncommonly popular tree in modern culture. Examples shown here (at right) include a postage stamp, beer, and a Lassie episode. It's also a microprocessor, any number of private businesses (film production, décor, weapons, real estate, logistics, health services, motels, sportswear, finance, and more), and a frequent subject for arts in every medium. I suspect this is because the bristlecone pine is synonymous with longevity and beauty in the face of extreme adversity.

Overall, though, the principal human use of this species has been scientific, in the field of dendrochronology. Pinus longaeva is generally regarded as the longest-lived of all sexually reproducing, nonclonal species, with many individuals known to have ages exceeding 4,000 years. Due to the resinous wood and extremely cold and arid habitat, decay of dead wood is extremely slow, and wood lying on the ground in some stands has ages exceeding 10,000 years. This has permitted building a continuous chronology from the present back to 6828 BC for trees in the White Mountains of California/Nevada (Hughes and Graumlich 1996); recent work suggests that this record may soon be extended to establish a chronology spanning 10,359 years, i.e. essentially the entire Holocene (Salzer et al. 2019). The long White Mountains chronology has been used, among other things, to calibrate the radiocarbon timescale (the rate of radiocarbon production in the atmosphere is not constant over time, thus the need for calibration). The species has been widely used in dendroclimatic reconstruction, most famously figuring in the popular debate over anthropogenic global warming, and in several classic studies of timberline ecology.

It is appropriate to note here that several of history's most noteworthy dendrochronologists have spent a large part of their lives studying this, the oldest and perhaps the hardiest of all the world's trees, in its remote mountain habitat. Edmund Schulman (1909-1958) is generally credited as the first person to discover the trees' great age, certainly the first to study the phenomenon. Pritchett (2021) provides an engaging discussion of the events surrounding the late 1940's/early 1950's discovery of great age among the bristlecones, and Schulman's eventual scientific studies in the White Mountains. C. Wesley Ferguson worked closely with geochronologists to use ancient bristlecone wood to develop the radiocarbon timescale calibration. He also discovered and sampled many stands of very old trees (Ferguson 1969). Hal Fritts (1969) studied the relationship between bristlecone pine ring widths and climate variation. Valmore C. LaMarche (1969) did pioneering work studying how bristlecones survive in an extraordinarily high, dry, cold environment, and went on to use the tree-ring record from bristlecones to provide estimates of climatic change over the past several thousand years (LaMarche and Mooney 1967, 1972; LaMarche 1973, 1978). Donald A. Graybill was a pioneer in research efforts to discover evidence of global warming in the bristlecone pine record (LaMarche et al. 1984). He also assembled a very extensive collection of bristlecone tree-ring data. The close association between bristlecones and dendrochronologists (a mutualism, we might say) has been touched on by a number of authors, notable Cohen (1998).

Observations

The best-known place to see bristlecones is in the Inyo National Forest of California, where the U.S. Forest Service maintains an interpretive trail through an exceptional bristlecone grove (with a web site). In Great Basin National Park (Nevada), the National Park Service provides similar facilities, albeit in a much less remarkable grove. Other popular locations to see the trees include Bryce Canyon National Park (Utah) and Cedar Breaks National Monument (Utah), which again are not among the finer groves in terms of size or tree age. More memorable sights can be had for a little more effort on the ridges around Charleston Peak, outside Las Vegas, Nevada; a Google search will turn up a variety of sites providing information on these trails. This may be the best of all places to see the species, because you first encounter it as saplings in understory gaps in a forest with Pinus ponderosa, Pinus monophylla, and Abies concolor, among others; it occurs in mixed forest with these species as you climb the mountain, until at the highest elevations it grows alone as very old and contorted individuals; and in that forest grows the largest specimen of this species known.

I can also recommend the grove on the slopes of Duckwater Mountain in the White Pine Mountains of central-eastern Nevada, shown in some of the photos at right; however it will take some stamina and probably a high-clearance vehicle to get there. A more accessible and also very memorable grove is on the summit ridge of Cave Mountain, southeast of Ely, Nevada. A steep road passable for light trucks and sturdy sedans climbs to a communications complex on the summit of this peak and affords access to spectacular groves of ancient bristlecone and limber (Pinus flexilis) pines, as well as much younger trees, including a closed-canopy forest containing young bristlecone pine and white fir (Abies concolor). Such ecological diversity cannot be found at the popular groves mentioned above.

Clicking on the distribution map above will also show some other sites where I have found the species. I can recommend bristlecone-hunting as a pleasant and (mostly) relaxing exercise that will inevitably introduce you to some very nice country. I have met many tree-lovers who agree that this tree does not grow anyplace that is less than gorgeous. Perhaps that is why I have never found a botanical garden or arboretum that owns a specimen.

Remarks

A wealth of information on this species is available at the Bristlecone Pine Home Page Among other things, it provides a description of the incident that culminated with cutting down the oldest living tree ever found.

This species is one of the primary hosts for the dwarf mistletoe Arceuthobium cyanocarpum (Hawksworth and Wiens 1996).

This is currently the only species of North American white pine that remains unaffected by White pine blister rust (Cronartium ribicola), an introduced fungal disease (though the southern subspecies of foxtail pine, P. balfouriana subsp. austrina, has also not been affected to date) (Vogler et al. 2006, Maloney 2011).

Although now it is the archetypal high mountain pine, during Pleistocene glaciopluvial intervals bristlecones occurred at much lower elevations, in some cases covering valley floors that are now vegetated only by sagebrush (Artemisia tridentata) and similar shrubs. Evidence for this is mainly derived from analysis of macrofossils found in ancient packrat middens, which are remarkably common in the Great Basin. These valley floor forests commonly included Juniperus communis, Picea engelmannii, and Pinus flexilis along with Pinus longaeva. Naturally, as this happened within a large and heterogeneous area, the full picture is considerably more complex (Grayson 2011, pp. 163-169).

Bristlecones have also informed another field concerned with great age: gerontology. Telomeres are structures at the ends of the chromosome that play a critical role in cell division. Organisms with longer telomeres can sustain more cycles of cell division, and organisms with higher activity of the enzyme telomerase can better repair shortened telomeres. Pinus longaeva has significantly longer telomeres and higher telomere activity than more short-lived pine species (P. taeda, P. palustris, P. resinosa). Watson and Riha (2010) note that “the rate of molecular evolution in trees and shrubs with long generation times is slower when compared to related herbaceous plants with shorter generation times ... One explanation for this observation is that plant meristematic cells possess robust DNA repair and genome maintenance mechanism.” This is an active research area among genontologists seeking to discover ways to use plant genes to make humans live longer.

Citations

Brown, Peter. 2013. Rocky Mountain Tree-Ring Research, OLDLIST. http://www.rmtrr.org/oldlist.htm, accessed 2013.03.15.

Burchfield, D. R., O. W. De Groff, S. G. Kitchen, D. A. Charlet, D. H. Page, C. I. Millar, D. J. Merkler, G. W. Taylor, H. G. Ortiz, and S. L. Petersen. 2021. A comprehensive distribution map and habitat suitability model for Great Basin bristlecone pine (Pinus longaeva D.K. Bailey). Pages 58-99 in Burchfield, D. R., Assessment of Great Basin Bristlecone Pine (Pinus longaeva D.K. Bailey) Forest Communities Using Geospatial Technologies. Ph.D. dissertation, Brigham Young University.

Cohen, Michael P. 1998. A garden of bristlecones. Reno, NV: University of Nevada Press.

Critchfield, William B. 1977. Hybridization of foxtail and bristlecone pines. Madroño 24(4):193-212. Available: Biodiversity Heritage Library, accessed 2021.12.19.

Ferguson, C.W. 1969. A 7104-year annual tree-ring chronology for bristlecone pine, Pinus aristata, from the White Mountains, California. Tree-Ring Bulletin 29(3-4):3-29.

Fritts, Harold C. 1969. Bristlecone pine in the White Mountains of California, growth and ring-width characteristics. Papers of the Laboratory of Tree-Ring Research No.4. Tucson: University of Arizona Press.

Grayson, Donald K. 2011. The Great Basin: A Natural Prehistory. University of California Press.

Hughes, M. K. and L. J. Graumlich. 1996. Climatic variations and forcing mechanisms of the last 2000 years. Volume 141. Multi-millenial dendroclimatic studies from the western United States. NATO ASI Series, 109-124.

LaMarche Jr., Valmore C. and Harold A. Mooney. 1967. Altithermal timberline advance in western United States. Nature 213:980-982.

LaMarche Jr., Valmore C. 1969. Environment in relation to age of bristlecone pines. Ecology 50(1):53-59.

LaMarche Jr., Valmore C. and Harold A. Mooney. 1972. Recent climatic change and development of the bristlecone pine (Pinus longaeva Bailey) krummholz zone, Mt. Washington, Nevada. Arctic and Alpine Research 4(1):61-72.

LaMarche Jr., Valmore C. 1973. Holocene climatic variations inferred from tree line fluctuations in the White Mountains, California. Quaternary Research 3:632-660.

LaMarche Jr., Valmore C. 1978. Tree-ring evidence of past climatic variability. Nature 276:334-338.

LaMarche Jr., Valmore C. and Katherine K. Hirschboeck. 1984. Frost rings in trees as records of major volcanic eruptions. Nature 307:121–126.

LaMarche Jr., Valmore C., D. A. Graybill, Harold C. Fritts, and Martin R. Rose. 1984. Increasing atmospheric carbon dioxide: tree-ring evidence for growth enhancement in natural vegetation. Science 225:1019-1021.

Lanner, Ronald M. 1988. Dependence of Great Basin bristlecone pine on Clark's nutcracker for regeneration at high elevations. Arctic and Alpine Research 20(3):358-362.

Maloney, P. E. 2011. Incidence and distribution of white pine blister rust in the high-elevation forests of California. Forest Pathology 41(4):308–316.

Mann, Michael E., Raymond S. Bradley, and Malcolm K. Hughes. 1998. Global-scale temperature patterns and climate forcing over the past six centuries. Nature 392(6678):779–787.

Pritchett, Daniel W. 2021. Finding Methuselah: New light on an old story. Tree-Ring Research 77(1):20-31.

Salzer, M. W., and M. K. Hughes. 2007. Bristlecone pine tree rings and volcanic eruptions over the last 5000 yr. Quaternary Research 67(1):57–68.

Salzer, M. W., M. K. Hughes, A. G. Bunn, and K. F. Kipfmueller. 2009. Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes. Proceedings of the National Academy of Sciences 106(48):20348–20353.

Salzer, Matthew W., Charlotte L. Pearson, and Christopher H. Baisan. 2019. Dating the Methuselah Walk bristlecone pine floating chronologies. Tree-Ring Research 75(1):61-66.

Sargent, C. S. 1879. The forests of central Nevada. American Journal of Science and Arts 17:417-426. Available: Biodiversity Heritage Library, accessed 2022.01.20.

Smithers, B. V., M. P. North, C. I. Millar, and A. M. Latimer. 2018. Leap frog in slow motion: Divergent responses of tree species and life stages to climatic warming in Great Basin subalpine forests. Global Change Biology 24:e442-e457.

Stringham, T. K., P. Novak-Echenique, P. Blackburn, C. Coombs, D. Snyder, and A. Wartgow. 2015. Final Report for USDA Ecological Site Description State-and-Transition Models, Major Land Resource Area 28A and 28B Nevada. University of Nevada Reno, Nevada Agricultural Research Report 2015-01. Available http://forestry.nv.gov/wp-content/uploads/2017/03/MLRA28_DRG24A.pdf, accessed 2019.07.15, now defunct.

Taylor, G. W. 2018. An ecological and distributional analysis of Great Basin bristlecone pine (Pinus longaeva). M.S. Thesis, Dept. of Plant and Wildlife Sciences, Brigham Young University.

Train, Percy, James R. Henrichs and W. Andrew Archer. 1941. Medicinal Uses of Plants by Indian Tribes of Nevada. Washington DC: U.S. Department of Agriculture (page 117).

Vogler, D. R., A. Delfino-Mix, and A. W. Schoettle. 2006. White pine blister rust in high-elevation white pines: screening for simply-inherited, hypersensitive resistance. www.fs.fed.us/rm/pubs_other/rmrs_2006_volger_d001.pdf, accessed 2014.09.07.

Watson, J.M. and K. Riha. 2010. Telomeres, aging, and plants: From weeds to Methuselah - a mini-review. Gerontology 4:327-338.