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A3499 Juniperus occidentalis Shrubby Woodland Alliance
Type Concept Sentence: This woodland and savanna alliance is characterized by diagnostic tree species Juniperus occidentalis that forms an open to moderately dense tree layer with an understory dominated by an open to dense shrub layer (commonly Artemisia tridentata). It occurs on the Columbia Plateau extending from southwestern Idaho, along the eastern foothills of the Cascades, south to the Modoc Plateau of northeastern California.
Common (Translated Scientific) Name: Western Juniper Shrubby Woodland Alliance
Colloquial Name: Western Juniper Shrubby Woodland
Hierarchy Level: Alliance
Type Concept: Vegetation of this woodland alliance is characterized by an open to moderately dense canopy of Juniperus occidentalis with a moderately dense to dense shrub layer. Juniperus occidentalis is typically the only tree species, although Pinus ponderosa may be present in some stands. Pinus jeffreyi may occasionally occur in stands of this alliance in extreme northeastern California. The tree form of Cercocarpus ledifolius may occasionally codominate. The shrub layer is dominated by Artemisia tridentata as the most common shrub; others are Cercocarpus ledifolius (shrub form), Chrysothamnus viscidiflorus, Ericameria nauseosa, Purshia tridentata, Ribes cereum, and Symphoricarpos oreophilus. A sparse to moderately dense herbaceous layer may be present that is typically dominated by graminoids such as Carex filifolia, Festuca idahoensis, Poa secunda, and Pseudoroegneria spicata. This woodland alliance is found on the Columbia Plateau and extends to the northern and western margins of the Great Basin, from southwestern Idaho to the eastern foothills of the Cascades, and south to the Modoc Plateau of northeastern California. Stands range in elevation from under 200 m along the Columbia River in central Washington to over 1800 m in southwestern Idaho. Generally soils are medium-textured, with abundant coarse fragments, and derived from volcanic parent materials. In central Oregon, the center of distribution, all aspects and slope positions occur. Where this alliance grades into relatively mesic forest or grassland habitats, these woodlands become restricted to rock outcrops and escarpments having xeric soils.
Diagnostic Characteristics: This woodland alliance has an open to dense tree canopy dominated by Juniperus occidentalis. The understory is characterized by an open to dense shrub layer dominated by characteristic species Artemisia tridentata, Cercocarpus ledifolius (shrub form), Chrysothamnus viscidiflorus, Ericameria nauseosa, Purshia tridentata, Ribes cereum, and Symphoricarpos oreophilus. A sparse to moderately dense herbaceous layer may be present that is typically dominated by graminoids such as Carex filifolia, Festuca idahoensis, Poa secunda, and Pseudoroegneria spicata. Shrub cover is generally greater than 20% or exceeds herbaceous cover.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: No Data Available
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Stands in this alliance are characterized by an open canopy (10-60% cover) of evergreen scale-leaved trees which vary widely in density due to edaphic conditions. A patchy to continuous layer of evergreen and winter-deciduous shrubs is often present, mixed with scattered perennial bunch grasses, forming a grassland/shrubland mosaic.
Floristics: Vegetation included in this alliance is characterized by a short (<20 m tall), open to moderately dense canopy of Juniperus occidentalis with a moderately dense to dense shrub layer. Juniperus occidentalis is typically the only tree species, although Pinus ponderosa may be present in some stands. Pinus jeffreyi may occasionally occur in stands of this alliance in extreme northeastern California. The tree form of Cercocarpus ledifolius or Quercus garryana may occasionally be present to codominate. The shrub layer is dominated by Artemisia tridentata as the most common shrub; other shrubs may include Amelanchier alnifolia, Cercocarpus ledifolius (shrub form), Chrysothamnus viscidiflorus, Ericameria nauseosa, Prunus emarginata, Prunus virginiana, Purshia tridentata, Ribes cereum, Ribes velutinum, Symphoricarpos oreophilus, and Tetradymia spp. A sparse to moderately dense herbaceous layer may be present that is typically dominated by graminoids such as Bromus carinatus, Carex filifolia, Carex rossii, Festuca idahoensis, Hesperostipa spp., Koeleria macrantha, Poa secunda, and Pseudoroegneria spicata. No forbs dominate, although species such as Achillea millefolium, Arabis holboellii, Collinsia parviflora, Eriophyllum lanatum, Gayophytum diffusum, Geum triflorum, Phacelia heterophylla, and Senecio integerrimus may be present.
Dynamics: Throughout much of the range of this alliance, Juniperus occidentalis populations are expanding into contiguous Artemisia shrub-steppe. The reasons for this are not entirely clear, but Juniperus occidentalis has been documented to germinate and grow preferentially under the canopy of Artemisia and other shrubs (Everett 1986). Burkhardt and Tisdale (1969) noted that larger, older trees are often associated with rock outcrops, while younger trees are prevalent on adjacent alluvial soils. This pattern has also been observed in northeastern California (Barbour and Major 1977). This pattern has been interpreted to mean that Juniperus occidentalis is colonizing out from rocky refuges which offer shelter from fire, and that the recent expansion of Juniperus occidentalis woodlands can be linked to fire suppression.
Environmental Description: This woodland alliance is found on the Columbia Plateau and extends to the northern and western margins of the Great Basin, from southwestern Idaho to the eastern foothills of the Cascades, and south to the Modoc Plateau of northeastern California. Throughout the range the climate is semi-arid, with 23-36 cm of precipitation annually, and a maximum in winter. The temperature regime is cool summer-continental, with a wide range in diurnal temperatures and night frosts through most of the year. Summer lightning storms and associated fire are common in the environments where this type occurs and are presumably important in structuring the vegetation. Stands often occur on moderate slopes (25-30%) on southern to southwestern aspects, but can occur on all aspects and gentle to steep slopes. Elevations range from under 200 m along the Columbia River in central Washington to over 1800 m in southwestern Idaho. Substrates are generally well-drained and moderately deep, medium-textured soils with abundant coarse fragments, and derived from volcanic parent materials. Where this type grades into relatively mesic forest or grassland habitats, the vegetation becomes restricted to rock outcrops or escarpments with excessively drained soils.
Geographic Range: This woodland alliance is found largely in the Columbia Plateau and occurs along the northern and western edges of the Great Basin from southern California north to central Washington and east to southwestern Idaho. The areas of broadest distribution are central Oregon and the Modoc Plateau of northeastern California. Both areas lie just east of the Cascade Range and have extensive moderate-elevation terrain with gentle topography. This alliance is found west of the Cascade-Sierra axis in the upper Klamath Basin, where it occurs in the rainshadow of the Klamath Mountains.
Nations: US
States/Provinces: CA, ID, NV?, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899621
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 1 Forest & Woodland Class | C01 | 1 |
| Subclass | 1.B Temperate & Boreal Forest & Woodland Subclass | S15 | 1.B |
| Formation | 1.B.2 Cool Temperate Forest & Woodland Formation | F008 | 1.B.2 |
| Division | 1.B.2.Nc Western North American Pinyon - Juniper Woodland & Scrub Division | D010 | 1.B.2.Nc |
| Macrogroup | 1.B.2.Nc.1 Singleleaf Pinyon - Utah Juniper - Western Juniper Intermountain Woodland Macrogroup | M896 | 1.B.2.Nc.1 |
| Group | 1.B.2.Nc.1.b Western Juniper Open Woodland Group | G248 | 1.B.2.Nc.1.b |
| Alliance | A3499 Western Juniper Shrubby Woodland Alliance | A3499 | 1.B.2.Nc.1.b |
| Association | CEGL000723 Western Juniper / Mountain Big Sagebrush Woodland | CEGL000723 | 1.B.2.Nc.1.b |
| Association | CEGL000725 Western Juniper / Curl-leaf Mountain-mahogany / Bluebunch Wheatgrass Woodland | CEGL000725 | 1.B.2.Nc.1.b |
| Association | CEGL000726 Western Juniper / Curl-leaf Mountain-mahogany - Mountain Snowberry Woodland | CEGL000726 | 1.B.2.Nc.1.b |
Concept Lineage: This alliance is composed of 3 shrub-dominated understory associations from Old Alliance II.A.4.N.a. Juniperus occidentalis Woodland Alliance (A.535). A.535 (in part)
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: > Juniperus occidentalis / Cercocarpus ledifolius / Festuca idahoensis - Agropyron spicatum Plant Association (Johnson and Clausnitzer 1992)
- Barbour, M. G., and J. Major, editors. 1977. Terrestrial vegetation of California. John Wiley and Sons, New York. 1002 pp.
- Barrows, J. S., E. W. Mogren, K. Rowdabaugh, and R. Yancik. 1977. The role of fire in ponderosa pine and mixed conifer ecosystems. Final report, Cooperative report between the National Park Service and Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. 101 pp.
- Burkhardt, J. W., and E. W. Tisdale. 1969. Nature and successional status of western juniper vegetation in Idaho. Journal of Range Management 22:264-270.
- Burkhardt, J. W., and E. W. Tisdale. 1976. Causes of juniper invasion in southwestern Idaho. Ecology 57:472-484.
- Dealy, J. E. 1975. Ecology of curl-leaf mahogany (Cercocarpus ledifolius Nutt.) in Oregon and adjacent areas. Unpublished dissertation, Oregon State University, Corvallis. 168 pp.
- Driscoll, R. S. 1964a. Vegetation-soil units in the central Oregon juniper zone. Research Paper PNW-19. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR. 60 pp.
- Everett, R. L., compiler. 1986. Proceedings pinyon-juniper conference: 1986 January 13-16, Reno, NV. General Technical Report INT-215. USDA Forest Service, Intermountain Research Station, Ogden, UT. 581 pp.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Johnson, C. G., and R. R. Clausnitzer. 1992. Plant associations of the Blue and Ochoco mountains. R6-ERW-TP-036-92. USDA Forest Service, Pacific Northwest Region, Wallowa-Whitman National Forest. 163 pp. plus appendices.
- ORNHP [Oregon Natural Heritage Program]. No date. Unpublished data files. Oregon Natural Heritage Program, The Nature Conservancy, Portland, OR.
- Youtie, B. A., and A. H. Winward. 1977. Plants and plant communities of the John Day Fossil Beds National Monument. Unpublished report to USDI National Park Service, John Day. 71 pp.