 | | Mature Utah Juniper growing on arid sandy slopes in Stone Canyon, Utah |  |
Utah Juniper
Juniperus osteosperma (Torr.) Little, Leafl. West. Bot. 5: 125, 1948.
Syn. Juniperus tetragona var. osteosperma Torr. (basionym); Sabina osteosperma (Torr.) Antoine; Juniperus californica var. utahensis Engelm.; Juniperus utahensis (Engelm.) Lemmon.
C. Michael Hogan and Michael P. Frankis
The Utah Juniper is an iconic and dominant tree endemic to the western USA, found in the Great Basin, Colorado Plateau, eastern face of the northern Rocky Mountains and Mogollon Rim, generally occupying the altitude niche of 1300 to 2600 meters. Its long lifespan and arid adaptive strategies lead to twisted picturesque forms, often featuring dead and alive portions on the same tree. Wood and berries of the species have been used for millennia by a number of Native American tribes as fuel, food and medicine.
Distribution and associations
J. osteosperma occurs in four main areas. In the Great Basin, the species is found in Nevada, southern Utah, extreme southern Idaho and California east of the Sierra Nevada. While the Utah Juniper occurs broadly in Nevada (Charlet 1996), it is generally restricted to the moderately high altitudes: specifically the Anchorite Hills, Black Canyon Range, Bird Spring Range, Belted Range, Adobe Range, Antelope Ranges, Augusta Mountains and Battle Mountain. In southern Utah, J. osteosperma is found broadly from Zion National Park, Bryce Canyon National Park, Escalante Grand Staircase National Monument, Capitol Reef National Park and eastward to Hovenweep as well as Arches and Canyonlands National Parks; all of these occurrences are typically in association with Pinus edulis. In the Mogollon Rim area of Arizona, J. osteosperma occurs in association with J. monosperma, J. deppeana and Cupressus glabra, with that association extending into northern New Mexico. In the northern Rocky Mountains J. osteosperma occurs along with Pinus edulis and J. scopulorum; east of the spine of Wyoming's Bighorn Mountains J. osteosperma is found on limestone substrate.
West of the Rocky Mountain Massif, from the Mogollon Mesa north, J. osteosperma and Pinus edulis cover vast areas of the Great Basin and Colorado Plateau with their dominant Pinyon-juniper association, J. osteosperma clearly preferring limestone substrate. There is considerable evidence that J. osteosperma is invading grassland and scrubland that existed in the 1900 era (Barbour & Billings 2000); this steady invasion may be a result of increased fire suppression, overgrazing or simply a rebound from the Native American and European settlement era where Utah Juniper was cumulatively over-harvested for firewood.
In the Madrean portion of the Rocky Mountains pygmy conifer woodlands occupy the transition area between low elevation desert and montane conifer forests. The dominant trees here are J. osteosperma, J. scopulorum and Pinus edulis, with Utah Juniper being dominant in the lower elevations and Pinyon Pine at the higher elevations.
S. currucoides is found in a number of western plant associations including Pinyon-Juniper woodland, Ponderosa Pine forest, Cedar-hemlock-Douglas-fir forest, Redwood forest, California Oak woodland, Douglas-fir forest, Juniper steppe woodland and Arizona pine forest.
 | | Utah Juniper shredding bark, near Bryce Canyon NP, Utah | |
Morphology
J. osteosperma is typically a large shrub or small tree growing to a height of 3–6 meters, rarely to 12 meters tall. The trunk is most often single and bark is thin and gray-brown in color, but becoming ash-white with age; trunk diameters of mature specimens range from 30–100 cm. Bark manifests conspicuous strip shredding and peeling in mature trees. The crown is characteristically rounded or conical and open in architecture. Young shoots are four- or six-angled, 1.5–2.5 mm diameter (Jepson 1993, Farjon 2005). The leaves are mostly six-ranked in decussate whorls of three on strong shoots, sometimes opposite and four-ranked on weaker shoots, and are closely appressed; they are scale-like with obscure glands. The pollen cones are cylindrical, 3–4.5 mm long and 2–2.5 mm broad, shedding pollen in early spring. The berry-like seed cones are spherical, (6–) 7–13 (–15) mm diameter; initially the seed cone is green, ripening to blue with a reddish tinge, but maturing to a dry state as red-brown. The cones typically contain one seed, rarely two; these are ovoid, 4–10 mm long, and strongly angled (Adams 2004, Farjon 2005). They are most often dispersed by frugivorous birds (e.g. Cedar Waxwing and American Robin) as well as certain mammals, including jackrabbits such as Black-tailed Jackrabbit and Coyote. Utah Juniper has developed an interesting deception strategy of generating a large number of hollow parthenocarpic seeds (Fuentes & Schupp 1998), leading to reduced levels of predation compared to individuals of J. osteosperma and related taxa that produce higher fractions of fertile seeds.
Taxonomy
 | | Utah Juniper berries and foliage, Zion National Park, Utah | |
Juniperus osteosperma has long been considered closely related to J. californica Carr. (Farjon 2005), even being treated as a variety of that by some early authors (e.g. Engelmann 1878); it is similar to that in many respects, sharing rather thick shoots and large, globular cones compared to other junipers in the region. It is best distinguished from J. californica in normally being monoecious (not dioecious) and the cones maturing in their second year (not first year); where they overlap locally in SE California, they are separated ecologically, with J. osteosperma on cooler, moister sites at higher altitude (Adams 2004, Farjon 2005).
J. osteosperma is also morphologically similar to J. occidentalis Hook., with the latter having smaller female cones which are blue-black without a reddish tinge; the two species occasionally hybridize in the wild. Recently, one study has suggested that the southern subspecies J. occidentalis subsp. australis Vasek may be genetically closer to J. osteosperma than to J. occidentalis subsp. occidentalis; to avoid paraphyly in J. occidentalis, they raised J. occidentalis subsp. australis to a separate species as J. grandis R.P.Adams (Adams et al. 2006), but this interpretation is not yet widely accepted (Earle 2009).
Juniperus scopulorum is also difficult to discriminate from J. osterosperma, but the cones of the former are smaller, more soft and juicy, the shoots are slenderer, and the bark is reddish brown. J. monosperma is quite similar to J. osteosperma, although the distributions overlap only in central Arizona. The former taxon grows more as a shrub or small tree without a the distinct upright trunk of J. osteosperma, and the J. monosperma crown is spreading and often scraggly.
Ecology
J. osteosperma characteristically occurs on arid flats, plateaus, hillsides, and the lower montane settings. This tree is most often found on dry rocky soils, and is common associated with one or more taxa of Pinyon pines, including Pinus edulis and P. monophylla. In some southern parts of the Utah Juniper's range, it overlaps the occurrence of the desert Elephant tree, Bursera microphylla. (Hogan) Characteristic shrub species found in the same Pinyon-juniper understory are: Giant Sagebrush (Artemisia tridentata), Mormon Tea (Ephedra viridis), Rubber Rabbitbrush (Chrysothamnus nauseosus) and Roundleaf Buffaloberry (Shepherdia rotundifolia).
Utah Juniper invokes an arid environment adaptation of shutting off water to certain limbs in order to conserve water (Williams 2000). While the affected limbs may die, the remainder of the tree has a higher chance of survival and future seed production.
Due to the low grass and forb fuel mass within the Pinyon-Juniper association, fires are not frequent within natural areas of this association; consequently, the typical age distribution of J. osteosperma is one of uneven age, with some specimens attaining ages of at least 400 years.
A number of bird species are commonly associated with Pinyon-Juniper woodland; prominent among these are the Pinyon Jay (Gymnorhinus cyanocephalus), Mountain Bluebird (Sialia currucoides), Juniper Titmouse (Baeolophus ridgwayi), Gray Vireo (Vireo vicinior), Ash-throated flycatcher (Myiarchus cinerascens) and the raptor Ferruginous Hawk (Buteo regalis).
Prehistory
While the pre-Holocene vegetation palette of the Great Basin and Colorado Plateau was quite low in biodiversity, J. osteosperma was not present in that era (Bennett 1997); in fact, Utah Juniper did not appear in the Holocene landscape here until approximately 5000 BC. It likely occupied a much narrower range around the Mogallon Rim prior to the Holocene, and slowly spread north after the glacial retreat.
Native American prehistorical wood fuel use of various Juniperus species has been deduced from charcoal layers in Navajo habitation sites from Black Mesa in Arizona (Hastorf & Popper 1989). Navajo peoples also used extracts from the species as an analgesic and a dermatological remedy (Moerman 1997). The Havasupai people used J. osteosperma not only for firewood, but also as a building material and as dried food. The Hopi are known to have used extracts from the species as a gynocological aid as well as the berries for food, while Acoma peoples are known to have used the berries to concoct a soup.
References
* Adams, R. P. (2004). Junipers of the World: The genus Juniperus. Trafford Publishing ISBN 1-4120-4250-X.
* Adams, R. P., Nguyen, S., Morris, J. A., & Schwarzbach, A. E. (2006). Re-examination of the taxonomy of the one-seeded, serrate leaf marginated Juniperus of Southwestern United States and northern Mexico (Cupressaceae). Phytologia 88 (3): 299-309.
* Barbour, M. G. & Billings, W. D. (2000). North American terrestrial vegetation, 2nd ed, 708 pages. ISBN-13: 9780521559867
* Bennett, K. D. (1997). Evolution and ecology: the pace of life, Cambridge University Press, 241 pages
* Charlet, D. A. (1996). Atlas of Nevada conifers: a phytogeographic reference, 320 pages.
* Earle, C. J. (2009). Juniperus occidentalis on the Gymnosperm Database.
* Engelmann, G. (1878). The American junipers of the section Sabina. Trans. St. Louis Acad. Sci. 3: 583-592.
* Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4.
* Fuentes, M. & Schupp, E. W. (1998). Empty seeds reduce seed predation by birds in Juniperus osteosperma. Evolutionary Ecology 12 (7): 823-827.
* Hastorf, C. A. & Popper, V. S. (1989). Current Paleoethnobotany: Analytical Methods and Cultural Interpretations of Archaeological Plant Remains. University of Chicago Press.
* Hogan, C. Michael (2009) Elephant Tree: Bursera microphylla, GlobalTwitcher.com, ed. N. Stromberg
* Jepson Manual. (1993). Juniperus osteosperma, University of California, Berkeley
* Moerman, D. E. (1997). Native American ethnobotany. Timber Press, 927 pages. ISBN-10: 0881924539
* Williams, D. B. (2000). Naturalists Guide to Canyon Country. 192 pages
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