Juniperus occidentalis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Pinopsida Pinales Cupressaceae

Scientific Name: Juniperus occidentalis Hook.
Infra-specific Taxa Assessed:
Common Name(s):
English Western Juniper
Taxonomic Source(s): Farjon, A. 2010. A Handbook of the World's Conifers. Koninklijke Brill, Leiden.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2013
Date Assessed: 2011-03-08
Assessor(s): Farjon, A.
Reviewer(s): Adams, R & Thomas, P.
Juniperus occidentalis is presently increasing in abundance, spread and numbers of mature individuals. The southern subpopulations are stable, but lack of recruitment locally could pose problems following destructive events. The overall assessment of Least Concern is driven by the larger subpopulations in the north, which are all increasing.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Recorded from the western USA: California, W Idaho, NW & W Nevada, Oregon, and S Washington.
Countries occurrence:
United States (California, Idaho, Nevada, Oregon, Washington)
Additional data:
Lower elevation limit (metres):200
Upper elevation limit (metres):3100
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Locally common with subpopulations expanding in some areas. An aggressive juniper, invading grasslands in eastern Oregon. Current control/ eradication programs are unlikely to control it, as fire control is so good (and desired by the public).
Current Population Trend:Increasing
Additional data:
Continuing decline of mature individuals:No
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:In the northern part of its range (var. occidentalis) Western Juniper often forms single species stands, or it is associated with Pinus ponderosa. Here it is most frequently found on flood plains, terraces, and grassy plateaux and uplands. In E Oregon it is also spreading onto abandoned agricultural fields and rangeland, partly as a result of a decreasing frequency of wildfires. In the Sierra Nevada (var. australis) it can grow with Pinus jeffreyi, P. albicaulis, P. monticola, P. contorta, Abies magnifica, Calocedrus decurrens, and Tsuga mertensiana. The most common understorey shrub in its entire range is Seriphidium tridentatum (Artemisia tridentata); in the north also Chrysothamnus spp., Purshia tridentata, Ribes cereum, in the south Arctostaphylos spp., Ceanothus sp., and several others. The altitudinal range is 200-1,200 m a.s.l. (var. occidentalis) and 1980-3100 m a.s.l. (var. australis). In coniferous forest it usually occurs where rock outcrops cause shallow soils, at higher altitudes in the Sierras it can usually be found among granite boulders or even in crevices on bare granite domes. In the north it grows on xeric soils, often derived from volcanic rock, or from non-calcareous sediment. The climate ranges from semi-arid in the rain shadow of the Cascades (15-45 cm p/a) in the north to mesic in the Sierras, with precipitation mostly in the form of winter snow.
Continuing decline in area, extent and/or quality of habitat:No
Generation Length (years):100

Use and Trade [top]

Use and Trade: The wood of this juniper is still used locally for firewood, fence poles, corrals, etc. Its very durable wood is also used for special purposes such as furniture, interior panelling and decorative applications. Horticultural use is rare, but the species has value for landscaping of disturbed sites. There are a few cultivars known, one of these has conspicuously silvery glaucous foliage and is called 'Sierra Silver' and, at least for a time, retains the columnar or pyramidal habit of younger plants.

Threats [top]

Major Threat(s): Overall, the species is not threatened. However, for var. australis, due to extreme environmental limitations, recruitment and growth  are sporadic and extremely slow. In many subpopulations there are only old or senescent trees present; if these were all to die from stochastic events or an alien pathogen (not present now) this taxon could become threatened with extinction.

Conservation Actions [top]

Conservation Actions: This is one of the (few) conifers which is dramatically increasing its extent of occurrence and area of occupancy, mainly due to decreasing pressure from grazing by livestock, as agricultural economies and practices shift away from massive cattle raising and/or sheep herding. Where past overgrazing has greatly increased woody low shrubs such as Artemisia tridentata (“sage brush”) a nursing environment has been created providing shelter from sun and weather (and herbivores) to juniper seedlings.

Citation: Farjon, A. 2013. Juniperus occidentalis. The IUCN Red List of Threatened Species 2013: e.T42242A2965783. . Downloaded on 19 September 2017.
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