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G248 Juniperus occidentalis Open Woodland Group
Type Concept Sentence: This woodland and savanna group is centered on the Columbia Plateau and extends from the eastern foothills of the Cascades and the Modoc Plateau across the northern margin of the Great Basin and is characterized by an open to closed canopy of Juniperus occidentalis that is sometime codominated by Cercocarpus ledifolius and typically has a shrubby understory dominated by Artemisia tridentata.
Common (Translated Scientific) Name: Western Juniper Open Woodland Group
Colloquial Name: Columbia Plateau Western Juniper Open Woodland
Hierarchy Level: Group
Type Concept: This woodland group is found on the Columbia Plateau and extends to the northern and western margins of the Great Basin, from southwestern Idaho, along the eastern foothills of the Cascades, south to the Modoc Plateau of northeastern California. Juniperus occidentalis is typically the only tree species with Pinus monophylla absent. Pinus ponderosa or Pinus jeffreyi may be present in higher elevation stands. The tree form of Cercocarpus ledifolius may occasionally codominate. In the understory, Artemisia tridentata is the most common shrub; others are Cercocarpus ledifolius (shrub form), Chrysothamnus viscidiflorus, Ericameria nauseosa, Purshia tridentata, Ribes cereum, and Tetradymia spp. Graminoids commonly include Carex filifolia, Festuca idahoensis, Poa secunda, and Pseudoroegneria spicata. This group occurs over a wide elevation range from under 200 m along the Columbia River in central Washington to over 1500 m in the Blue Mountains. In the middle of its distribution in central Oregon, stands occur on all aspects and slope positions. Older woodlands are generally found in rocky areas where fire frequency is low. Generally soils are medium-textured, with abundant coarse fragments, and derived from volcanic parent materials. Throughout much of its range, fire exclusion and removal of fine fuels by grazing livestock have reduced fire frequency and allowed Juniperus occidentalis seedlings to colonize adjacent alluvial soils and expand into the shrub-steppe and grasslands. Juniperus occidentalis savanna may occur on the drier edges of woodlands where trees are intermingling with or invading the surrounding grasslands and where local edaphic or climatic conditions favor grasslands over shrublands. Where this group grades into relatively mesic forest or grassland habitats, these woodlands become restricted to rock outcrops or escarpments with excessively drained soils.
Diagnostic Characteristics: Juniperus occidentalis is the diagnostic and typically dominant species of this woodland and savanna group. This juniper species is largely restricted to the Columbia Plateau ecoregion. Cercocarpus ledifolius may codominate some stands. Pinus monophylla is not present in this region. The understory of stands included in this group is variable and ranges from perennial grass-dominated tree savannas and open woodlands to open and moderately dense woodlands with a shrub-dominated understory to wooded shrublands with a sparse Juniperus occidentalis tree layer (5-10% cover).
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This woodland group includes two very different ecological types. There are old-growth Juniperus occidentalis woodlands with trees and stands often over 1000 years old, with large, fairly well-spaced trees with rounded crowns. There are also large areas where juniper has expanded into sagebrush steppe and bunchgrass-dominated areas, with young, pointed-crowned trees growing closely together. Currently, these two very different types are about equally distributed across the landscape, with Juniperus occidentalis continuing to expand, either from the combination of fire exclusion, past grazing or climate change. Juniperus occidentalis has also expanded into Pinus ponderosa and Pinus ponderosa - Pinus contorta stands in central Oregon. These two types correspond to the Juniperus occidentalis-dominated portion of the persistent pinyon-juniper woodlands (open to denser of tree canopy occurring on shallow rocky soils) and wooded shrublands (open tree canopy with well-developed shrub stratum and variable grass-forb cover) described by Romme et al. (2009).
Woodland stands dominated by Juniperus grandis (= Juniperus occidentalis var. australis) occur in the subalpine Sierra Nevada and forested uplands of the northern Coast Ranges of California, southward to San Bernardino, San Gabriel and various desert mountain ranges and westward into Nevada are included in ~Sierra-Cascade Cold-Dry Subalpine Woodland Group (G243)$$.
Woodland stands dominated by Juniperus grandis (= Juniperus occidentalis var. australis) occur in the subalpine Sierra Nevada and forested uplands of the northern Coast Ranges of California, southward to San Bernardino, San Gabriel and various desert mountain ranges and westward into Nevada are included in ~Sierra-Cascade Cold-Dry Subalpine Woodland Group (G243)$$.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This woodland and savanna group has an open to dense canopy that includes two very different tree canopy structures: (1) an old-growth Juniperus occidentalis woodland with large, fairly well-spaced trees with rounded crowns, and (2) relatively young, often dense junipers trees with pointed crowns. The structure of the understory ranges from perennial grass-dominated tree savannas and open woodlands to shrublands with a very open tree canopy (wooded shrublands) and open to moderately dense woodlands with a shrub-dominated understory. Cover of understory species sharply declines when tree canopy cover exceeds 40% (Young et al. 1982). Many of the tree savannas have a sparse shrub layer present.
Floristics: Stands have a typically open tree canopy that is dominated by Juniperus occidentalis trees, although Pinus ponderosa or Pinus jeffreyi may be present in some stands. Pinus monophylla is not present in this region. The tree form of Cercocarpus ledifolius may occasionally codominate. In the understory, Artemisia tridentata is the most common shrub; others are Purshia tridentata, Ericameria nauseosa, Cercocarpus ledifolius (shrub form), Chrysothamnus viscidiflorus, Ribes cereum, and Tetradymia spp. Graminoids commonly include Carex filifolia, Festuca idahoensis, Poa secunda, and Pseudoroegneria spicata.
Dynamics: Juniperus occidentalis is a long-lived tree that can exceed 3000 years in age in rocky, fire-protected areas such as along rimrock (Waigchler et al. 2001, Thorne et al. 2007). These fire-sensitive trees do not sprout following fire and are typically killed by moderate to severe fires (Tirmenstein 1999h, Sawyer et al. 2009). Young junipers have thin bark and are readily killed by surface fires (Martin et al. 1978), whereas mature trees with thicker bark are described as "moderately resistant" (Fowells 1965). Reproductive age begins at about 20 years, peaks after 50 years and continues for many years (Miller and Rose 1995, Tirmenstein 1999h). Following stand-replacing fire, recovery time is relatively slow and depends on stand maturity, the size and season of burn, fire severity and juniper mortality, the persistence of the seeds in the seed bank, location of seed source, the presence of animal dispersers such as Clark''s nutcrackers, competition from herbaceous species and shrubs, and the amount of post-fire precipitation (Burkhardt and Tisdale 1976, Tirmenstein 1999h). Large burns and long distances from seed sources slow recovery rates because seed dispersal is dependent on water and animals (Tirmenstein 1999h).
Environmental Description: This woodland group is found on the Columbia Plateau and extends to the northern and western margins of the Great Basin. Elevations range from under 200 m along the Columbia River in central Washington to over 1500 m. In central Oregon, the center of distribution, all aspects and slope positions occur. Old-growth stands are largely restricted to rocky outcrops, upper slopes and ridges, and rims of mesa and canyon that are fire-safe. Younger seral stands have invaded adjacent shrublands and grasslands and now occur on lower slopes, valleys and plains. Soils are generally medium-textured, with abundant coarse fragments, and derived from volcanic parent materials. Where this group grades into relatively mesic forest or grassland habitats, these woodlands become restricted to dry sites such as rock outcrops or escarpments with excessively drained soils. Soil/substrate/hydrology: Soils are generally 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 group grades into relatively mesic forest or grassland habitats, these woodlands become restricted to dry sites such as rock outcrops or escarpments with excessively drained soils.
Geographic Range: This woodland and savanna group is found along the northern and western margins of the Great Basin, from southwestern Idaho, along the eastern foothills of the Cascades, south to the Modoc Plateau of northeastern California. It also occurs in scattered localities of northern Nevada and south-central Washington.
Nations: US
States/Provinces: CA, ID, NV, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.833247
Confidence Level: Moderate
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 |
| Alliance | A3500 Western Juniper Grassy Open Woodland Alliance | A3500 | 1.B.2.Nc.1.b |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Juniperus occidentalis Zone (Franklin and Dyrness 1973)
= Northern Juniper Woodlands (Holland and Keil 1995)
= Western Juniper: 238 (Eyre 1980)
= Northern Juniper Woodlands (Holland and Keil 1995)
= Western Juniper: 238 (Eyre 1980)
- Barbour, M. G., and J. Major, editors. 1988. Terrestrial vegetation of California: New expanded edition. California Native Plant Society, Special Publication 9, Sacramento. 1030 pp.
- Burkhardt, J. W., and E. W. Tisdale. 1976. Causes of juniper invasion in southwestern Idaho. Ecology 57:472-484.
- Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
- Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
- Fowells, H. A, compiler. 1965. Silvics of the forest trees of the United States. Agriculture Handbook No. 271. USDA Forest Service, Washington, DC. 762 pp.
- Franklin, J. F., and C. T. Dyrness. 1973. Natural vegetation of Oregon and Washington. General Technical Report PNW-8. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR. 417 pp.
- Holland, V. L., and D. J. Keil. 1995. California vegetation. Kendall/Hunt Publishing Company, Dubuque, IA. 516 pp.
- 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.
- Martin, R. E., J. E. Dealy, and D. L. Caraher, editors. 1978. Proceedings of the western juniper ecology/management workshop; January 1977; Bend, OR. General Technical Report PNW-74. USDA Forest Service, Pacific Northwest Range and Forest Experiment Station, Portland, OR.
- Miller, R. F., and J. A. Rose. 1995. Historic expansion of Juniperus occidentalis (western juniper) in southeastern Oregon. The Great Basin Naturalist 55(1):37-45.
- Romme, W. H., C. D. Allen, J. D. Balley, W. L. Baker, B. T. Bestelmeyer, P. M. Brown, K. S. Eisenhart, M. L. Floyd, D. W. Huffman, B. F. Jacobs, R. F. Miller, E. H. Muldavin, T. W. Swetnam, R. J. Tausch, and P. J. Weisberg. 2009. Historical and modern disturbance regimes, stand structures, and landscape dynamics in pinon-juniper vegetation of the western United States. Rangeland Ecology & Management 62:203-222.
- Sawyer, J. O., T. Keeler-Wolf, and J. Evens. 2009. A manual of California vegetation. Second edition. California Native Plant Society, Sacramento CA. 1300 pp.
- Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.
- Thorne, R. F., A. A. Schoenherr, C. D. Clements, and J. A. Young. 2007. Transmontane coniferous vegetation. Pages 574-586 in: M. G. Barbour, T. Keeler-Wolf, and A. A. Schoenherr, editors. Terrestrial vegetation of California. Third edition. University of California Press, Berkeley.
- Tirmenstein, D. 1999h. Juniperus occidentalis. In: Fire Effects Information System [Online]. USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). [http://www.fs.fed.us/database/feis/] (accessed 31 August 2015).
- Volland, L. A. 1976. Plant communities of the central Oregon pumice zone. USDA Forest Service R-6 Area Guide 4-2. Pacific Northwest Region, Portland, OR. 113 pp.
- Waigchler, W. S., R. F. Miller, and P. S. Doescher. 2001. Community characteristics of old-growth western juniper woodlands in the pumice zone of central Oregon. Journal of Range Management 52:1-14.
- Young, J. A., R. A. Evans, J. D. Budy, and A. Torell. 1982. Cost of controlling maturing western juniper trees. Journal of Range Management 35(4):437-442.