Print Report

A3182 Artemisia tridentata ssp. wyomingensis Mesic Steppe & Shrubland Alliance

Type Concept Sentence: This mesic shrubland and steppe alliance is found in the western United States and southwestern Canada and is characterized by an open to dense (10-70% cover) shrub layer that is dominated (or codominated with at least 40% relative cover in mixed stands) by Artemisia tridentata ssp. wyomingensis. Common associates include Atriplex confertifolia, Artemisia frigida, Krascheninnikovia lanata, Purshia tridentata, and Symphoricarpos longiflorus.

Common (Translated Scientific) Name: Wyoming Big Sagebrush Mesic Steppe & Shrubland Alliance

Colloquial Name: Wyoming Big Sagebrush Mesic Steppe & Shrubland

Hierarchy Level:  Alliance

Type Concept: This mesic shrubland and steppe alliance is found in the western United States and southwestern Canada and is characterized by an open to dense (10-70% cover) shrub layer that is dominated (or codominated with at least 40% relative cover in mixed stands) by Artemisia tridentata ssp. wyomingensis. Common associates include Atriplex confertifolia, Artemisia frigida, Krascheninnikovia lanata, Purshia tridentata, and Symphoricarpos longiflorus. The herbaceous stratum can be diverse and have open to dense cover, but perennial graminoids typically total >20% cover. Characteristic dominant species are Balsamorhiza sagittata, Hesperostipa comata, Pascopyrum smithii, Poa secunda, and Pseudoroegneria spicata. Stands occur on flat to steeply sloping upland sites. Sites with little slope tend to have deep soils, while those with steeper slopes have shallow to moderately deep soils. Soil texture is loam, sandy loam, or clay loam with coarse fragments common in the soil profile.

Diagnostic Characteristics: This mesic steppe and shrubland alliance has an open to moderately dense conspicuous shrub layer dominated by diagnostic shrub Artemisia tridentata ssp. wyomingensis. Associated shrubs include Atriplex confertifolia, Artemisia frigida, Purshia tridentata, and Krascheninnikovia lanata. The herbaceous layer ranges from open to moderate cover, but perennial graminoids typically total >20% cover. Characteristic dominant species are Balsamorhiza sagittata, Hesperostipa comata, Pascopyrum smithii, Poa secunda, and Pseudoroegneria spicata.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This mesic shrubland and steppe alliance occurs as large patch/matrix stands in relatively mesic northern latitudes. However, in semi-arid landscapes in more southern latitudes, it frequently occurs in smaller patch stands restricted to relatively mesic sites, such as swales and basins, that receive additional moisture from surrounding slopes and at higher elevations.

Associations with undetermined subspecies of Artemisia tridentata from old alliances Artemisia tridentata Shrubland Alliance (A.829) and Artemisia tridentata Shrub Herbaceous Alliance (A.1521) were reviewed and placed into either ~Artemisia tridentata ssp. wyomingensis Mesic Steppe & Shrubland Alliance (A3182)$$ or ~Artemisia tridentata ssp. tridentata - Artemisia tridentata ssp. xericensis Mesic Steppe & Shrubland Alliance (A3183)$$. More review would increase confidence of placement. ~Artemisia tridentata ssp. wyomingensis - Peraphyllum ramosissimum / Festuca idahoensis Shrubland (CEGL001048)$$ was placed in this alliance (A3182) instead of Artemisia tridentata - Mixed Shrub Dry Shrubland Alliance (A3198)$$ because it is a relatively mesic shrubland, and the current concept of the association only requires Peraphyllum ramosissimum be present to codominant (1-20% cover), so it is not a reliable Artemisia tridentata - mixed shrub stand. Currently, this alliance includes stands in North Dakota In the northwestern Great Plains.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance is characterized by an open to dense (10-70%) cover of microphyllous evergreen shrubs, usually 0.3-1 m in height, although in Washington the shrubs may be up to 2 m tall. Cespitose graminoids are usually dominant, often matching, and sometimes exceeding, the shrubs in height or cover. Forb species may be frequent, but are usually of low canopy cover. With increasing summer rain in the eastern portion of the range, there is a corresponding increase in the proportion of sod-forming grasses as compared to bunchgrasses. Undisturbed stands in Washington and Oregon may have a nearly continuous cryptogamic soil crust of mosses and lichens.

Floristics: Shrubs are conspicuous in this alliance, but herbaceous species usually have equal or greater cover. The vegetation included in this alliance is characterized by an open to moderately dense (10-70% cover) shrub layer that is dominated (or codominated with at least 40% relative cover in mixed stands) by Artemisia tridentata ssp. wyomingensis. Common associated shrubs are Artemisia frigida, Chrysothamnus spp., Ericameria spp., Gutierrezia sarothrae, Krascheninnikovia lanata, Peraphyllum ramosissimum, and Symphoricarpos longiflorus. The herbaceous stratum can be diverse and have open to moderate cover, but perennial graminoids typically total <20% cover. The most widespread and common species are Pseudoroegneria spicata, which occurs from the Columbia Basin to the Northern Rockies, and Pascopyrum smithii, which is more common in the northwestern Great Plains. Other locally abundant grass associates include Achnatherum thurberianum (= Stipa thurberiana) (in the western portion of the range), Achnatherum hymenoides (= Oryzopsis hymenoides), Bouteloua curtipendula, Bouteloua gracilis, Carex filifolia, Elymus lanceolatus, Hesperostipa comata (= Stipa comata), Koeleria macrantha, Leymus ambiguus, and Poa secunda. Forbs form a minor and highly variable portion of this vegetation. Recurrent species include Achillea millefolium, Balsamorhiza sagittata, Camelina microcarpa, Erigeron spp., Opuntia spp., Phlox spp., and Sphaeralcea coccinea. Mosses and lichens, such as Selaginella densa and Tortula ruralis, may occur on bare ground. Where there is supplemental moisture or where the vegetation grades into forest, emergent needle-leaved evergreen or cold-deciduous trees may be scattered through these shrub-steppe communities. Recurrent tree associates include Juniperus occidentalis, Juniperus osteosperma, Juniperus scopulorum, Pinus contorta, Pinus edulis, Pinus flexilis, Pinus ponderosa, and Populus tremuloides.

Dynamics:  Stands in this alliance represent the moister communities of the Artemisia tridentata ssp. wyomingensis-dominated communities in ~Great Basin-Intermountain Tall Sagebrush Steppe & Shrubland Macrogroup (M169)$$. Shrub densities typically increase with overgrazing of the bunchgrass component or with increasing summer drought (West 1983c). Artemisia tridentata is inhibited by fire, and excessive grazing may decrease fire frequency due to consumption of herbaceous forage, resulting in increased shrub density. Conversely, invasion by non-native annual grasses (e.g., Bromus tectorum, Bromus arvensis) may increase fire frequency sufficiently to eliminate the shrubs from the stands (Daubenmire 1970). With a change in fire frequency, species composition will be altered as well (West 1983c). With a high fire frequency (every 2-5 years), perennial grasses and shrubs are eliminated and non-native annual grasses dominate. At fire-return intervals of 10-30 years, short-lived resprouting shrubs such as Chrysothamnus or Tetradymia spp. dominate. At fire intervals of 30-70 years, a mixture of perennial bunchgrasses and shrubs is maintained. Finally, in the complete absence of fire, deep-rooted shrubs such as Artemisia tridentata become the theoretical dominants.
Environmental Description:  This mesic steppe and shrubland alliance is found in the western United States and southwestern Canada from the Columbia River Basin south and east across the Great Basin. Climates range from semi-arid in the western Great Basin to subhumid in the Rocky Mountains and northern plains. The amount and reliability of growing-season moisture increase eastward and with increasing elevation. The associations in this alliance occur in somewhat wetter areas of the range of Artemisia tridentata ssp. wyomingensis, generally with over 25 cm annual precipitation or with a significant proportion falling in the growing season. These communities occur at elevations of less than 1000 m in the Columbia Basin and northern Great Plains to over 2500 m in the Rocky Mountains and Great Basin ranges. The alliance occurs on flat to steeply sloping upland sites. Sites with little slope tend to have deep soils, while those with steeper slopes have shallow to moderately deep soils (USFS 1992). Soil texture is loam, sandy loam, or clay loam (Hansen and Hoffman 1988), which allows ample shallow rainfall storage and percolation of snowmelt. Coarse fragments are common in the soil profile. Hironaka et al. (1983) reported that most of their Artemisia tridentata ssp. wyomingensis habitat types occurred on calcareous soils, often with some form of a cemented duripan or silica-hardpan at about 1 m in depth.

In eastern Idaho and western Wyoming, Artemisia tridentata ssp. wyomingensis occupies somewhat dry, low-elevation sites, while Artemisia tridentata ssp. tridentata or Artemisia cana occupy deep alluvial soils of drainage bottoms at low elevation, and Artemisia tridentata ssp. vaseyana occupies cooler, moister upland sites at higher elevation. In addition to Artemisia tridentata and Artemisia cana, other associated vegetation types include Atriplex confertifolia, Ericameria spp., or Chrysothamnus spp. shrublands, Abies grandis, Pinus contorta, Pinus ponderosa, Populus tremuloides, or Pseudotsuga menziesii forests, Pinus - Juniperus woodlands, or mesic herbaceous communities.
Geographic Range: This mesic alliance occurs from northeastern California and eastern Oregon across the Great Basin, Utah and habitats of the Rocky Mountains.. Associations are also reported from the intermountain parks of Colorado, and from British Columbia, Canada. The alliance has not been reported from either Arizona or New Mexico but may occur there.

Nations: CA,US

States/Provinces:  AB?, AZ?, BC?, CA, CO, ID, MT, NM?, NV, OR, UT, WA, WY


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 3 Desert & Semi-Desert Class C03 3
Subclass 3.B Cool Semi-Desert Scrub & Grassland Subclass S11 3.B
Formation 3.B.1 Cool Semi-Desert Scrub & Grassland Formation F033 3.B.1
Division 3.B.1.Ne Western North American Cool Semi-Desert Scrub & Grassland Division D040 3.B.1.Ne
Macrogroup 3.B.1.Ne.3 Big Sagebrush - Threetip Sagebrush - Antelope Bitterbrush Steppe & Shrubland Macrogroup M169 3.B.1.Ne.3
Group 3.B.1.Ne.3.b Basin Big Sagebrush - Threetip Sagebrush - Antelope Bitterbrush Big Sagebrush Steppe & Shrubland Group G302 3.B.1.Ne.3.b
Alliance A3182 Wyoming Big Sagebrush Mesic Steppe & Shrubland Alliance A3182 3.B.1.Ne.3.b
Association CEGL000994 Wyoming Big Sagebrush / Arrowleaf Balsamroot Shrubland CEGL000994 3.B.1.Ne.3.b
Association CEGL001009 Wyoming Big Sagebrush / Bluebunch Wheatgrass Shrubland CEGL001009 3.B.1.Ne.3.b
Association CEGL001047 Wyoming Big Sagebrush / Western Wheatgrass Shrub Grassland CEGL001047 3.B.1.Ne.3.b
Association CEGL001048 Wyoming Big Sagebrush - Wild Crabapple / Idaho Fescue Shrubland CEGL001048 3.B.1.Ne.3.b
Association CEGL001049 Wyoming Big Sagebrush / Sandberg Bluegrass Shrubland CEGL001049 3.B.1.Ne.3.b
Association CEGL001050 Wyoming Big Sagebrush - Antelope Bitterbrush / Bluebunch Wheatgrass Shrubland CEGL001050 3.B.1.Ne.3.b
Association CEGL001051 Wyoming Big Sagebrush / Needle-and-Thread Shrubland CEGL001051 3.B.1.Ne.3.b
Association CEGL001535 Wyoming Big Sagebrush / Bluebunch Wheatgrass Shrub Grassland CEGL001535 3.B.1.Ne.3.b
Association CEGL005478 Wyoming Big Sagebrush / Idaho Fescue Shrubland CEGL005478 3.B.1.Ne.3.b
Association CEGL005479 Threetip Sagebrush / Thurber''s Needlegrass Shrubland CEGL005479 3.B.1.Ne.3.b
Concept Lineage: This alliance includes some associations in old alliances III.A.4.N.a. Artemisia tridentata ssp. wyomingensis Shrubland Alliance (A.832) and V.A.7.N.e. Artemisia tridentata ssp. wyomingensis Shrub Herbaceous Alliance (A.1527).

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< Big Sagebrush Series (Sawyer and Keeler-Wolf 1995)
>< SRM Cover Type #314 - Big Sagebrush-Bluebunch Wheatgrass (Shiflet 1994)
>< SRM Cover Type #315 - Big Sagebrush-Idaho Fescue (Shiflet 1994)
= SRM Cover Type #403 - Wyoming Big Sagebrush (Shiflet 1994)
< SRM Cover Type #612 - Sagebrush - Grass (Shiflet 1994)
>< Western Shrub and Grasslands Combinations: 55: Sagebrush-Steppe (Artemisia-Agropyron) (Küchler 1964)
>< Western Shrub: 38: Great Basin Sagebrush (Artemisia) (Küchler 1964)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz

Acknowledgements: We have incorporated significant descriptive information previously compiled by D. Sarr.

Version Date: 12-18-14
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