Invalid Unit Specified
D040 Artemisia tridentata - Atriplex confertifolia / Hesperostipa comata Cool Semi-Desert Scrub & Grassland Division

The U.S. National
Vegetation Classification
Type Concept Sentence: This division encompasses all upland shrub and grassland vegetation within the Western North American Cool Semi-desert region, primarily in the Great Basin, but extending to western margins of the Great Plains to New Mexico, northward to dry-interior southern British Columbia and south through eastern Oregon and interior California, into the mountains of northwestern Baja California, Mexico. It includes extensive shrublands dominated by Artemisia tridentata, ranging from mid to upper slopes and deep to shallow soils, and extensive Atriplex shrublands.
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Common (Translated Scientific) Name: Big Sagebrush - Shadscale Saltbush /Needle-and-Thread Cool Semi-Desert Scrub & Grassland Division
Colloquial Name: Western North American Cool Semi-Desert Scrub & Grassland
Hierarchy Level: Division
Type Concept: This division includes a variety of native and non-native shrub and herbaceous vegetation growing naturally within the cool semi-desert climate zone of western North America, centered within the many closed basins and isolated mountain ranges of the Great Basin Province. It includes extensive shrublands dominated by Artemisia tridentata, involving four main varieties, each with distinctive ecologies, ranging from mid to upper slopes and deep to shallow soils. It also includes extensive Atriplex shrublands, largely restricted to lower slopes and basins. Subshrub Artemisia species or similarly low-growing subshrubs dominate on shallow, rocky soil or heavy clay soils and in exposed rocky, subalpine settings. These species include 10 separate taxa of small sagebrush, which segregate geographically and edaphically and are diagnostic at various levels within the division. On the plateaus and mountains of the southern Great Basin, bordering on the southwestern warm deserts, are an array of distinctive shrublands including leaf-succulent Yucca and Nolina species, and a variety of shrub genera (Buddleja, Coleogyne, Mortonia, Poliomintha, etc.) not found elsewhere in this division.

Grasslands are generally patchy within this landscape, locally restricted to sandy or loamy soils and to areas with high fire frequencies. Throughout the northern and western portions of the Great Basin grasslands are predominantly cool-season species (including Achnatherum, Hesperostipa, Poa, Festuca, Elymus, Pascopyrum, and Pseudoroegneria. In the southern and eastern portions, warm-season grass genera (e.g., Pleuraphis, Bouteloua, Muhlenbergia) increase. Intermediate moisture and fire conditions have shrub-steppe, with a combination of Artemisia species and mostly perennial grasses and herbs. Early-seral shrublands dominated by Ericameria and other short-lived shrubs occur in recovering burns, cleared land, or in intermittently flooded washes. Ruderal grassland dominated and characterized by non-native Eurasian annuals (e.g., Bromus tectorum, Taeniatherum caput-medusae) and perennial grasses (e.g., Agropyron cristatum) has, through the effects of recent fire, converted many thousands of acres of native shrubland and shrub-steppe in the past 75-100 years.

This division extends south and west of the Great Basin on isolated higher elevation mountains and plateaus surrounded by lower-lying and warmer bioclimates. It also extends eastward and northward to the edge of the Great Plains in eastern Montana, Wyoming, southern Alberta and southeastern British Columbia, Canada, and the western Dakotas. This suite of shrublands and grasslands occupies mountain slopes, plateaus, hills, valleys, and alluvium (including intermittently flooded washes and fans), within a broad range of soil types. The overall climate of the range of this division is in the Koppen bioclimatic zone Mid-latitude Dry Semiarid Steppe (BSk) with smaller areas of Mid-latitude Dry Arid Desert (BWk). Stands range from high plateaus and ridges with skeletal soils to deep well-drained alluvial soils on fans and near washes and heavy clay "self-churning" Vertisols. Some grasslands (now largely extinct) were limited to loess (e.g., Palouse Prairie). Soils harboring stands of certain ruderal vegetation (e.g., Acroptilon repens, Isatis tinctoria, Sisymbrium sp.) tend to occur on previously cultivated sites where the soil profile has been disrupted.
Diagnostic Characteristics: In general, diagnostic taxa are divided into several main genera. Taller taxa of Artemisia (Artemisia tridentata and its subspecies Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, and Artemisia tridentata ssp. xericensis) along with Purshia tridentata characterize some parts of the division, as do shorter taxa of Artemisia (Artemisia arbuscula, Artemisia bigelovii, Artemisia nova, Artemisia rothrockii, Artemisia pygmaea, Artemisia rigida, and others) and midsize shrubby species in the Amaranth family (Atriplex, Grayia, etc.). Ruderal non-native grasses and forbs from Eurasia characterize human-disturbed stands.
Rationale for Nominal Species or Physiognomic Features: A single widespread diagnostic from each of three main macrogroups was selected to represent the breadth of the division: Artemisia tridentata in ~Great Basin-Intermountain Tall Sagebrush Shrubland & Steppe Macrogroup (M169)$$, Atriplex confertifolia in ~Great Basin Saltbush Scrub Macrogroup (M093)$$, and Hesperostipa comata in ~Great Basin-Intermountain Dry Shrubland & Grassland Macrogroup (M171)$$. In addition to these division-level diagnostics there are numerous species that tend to be limited to individual macrogroups, groups, or alliances within the division.
Classification Comments: The relatively high number of macrogroups (7) defined for this division, coupled with the relatively few diagnostic species suggest some splitting has occurred. Within Great Basin-Intermountain Dry Shrubland & Grassland Macrogroup (M171), the difference between Mojave Mid-Elevation Mixed Desert Scrub Group (G296) and Colorado Plateau Blackbrush - Mormon-tea Shrubland Group (G312) is poorly defined, with separate groups each having alliances defined by the same diagnostics (e.g., Coleogyne, Ephedra viridis). Floristic similarities across the upper elevation Mojave Desert shrublands and those of the Colorado Plateau have been discussed previously (West 1993d). Intermountain Semi-Desert Steppe & Shrubland Group (G310) is floristically similar to Intermountain Sparsely Vegetated Dune Scrub & Grassland Group (G775), since both contain diagnostics such as Ericameria nauseosa. Great Basin-Intermountain Xeric-Riparian Scrub Macrogroup (M095) is poorly described and contains elements of Great Basin Saltbush Scrub Macrogroup (M093) (Atriplex canescens), and Great Basin-Intermountain Dry Shrubland & Grassland Macrogroup (M171) (e.g., Ericameria nauseosa). It is proposed that M095 be merged into M171, and G559 into G310 (M. Reid pers comm. 2016). Great Basin-Intermountain Xeric-Riparian Scrub Macrogroup (M095), if not found to contain any other diagnostic floristic elements, should be dissolved. Similarly, Intermountain Basins Cliff, Scree & Badland Sparse Vegetation Macrogroup (M118) contains very few diagnostics as described and could possibly be dissolved. For example, Atriplex canescens, Ephedra spp., Ericameria spp., and Pseudoroegneria already characterize other alliances in other macrogroups in the division. Further consideration should be given to removing these and other alliances (e.g., Pinus ponderosa - Cercocarpus intricatus Bedrock Cliff & Canyon Wooded Scrub Alliance (A4051)) and placing them within 1.B.2.Nb Rocky Mountain Forest & Woodland Division (D194). Some alliances (e.g., Eriogonum ovalifolium - Fallugia paradoxa - Andropogon hallii Lava & Cinder Sparse Vegetation Alliance (A4053)) seem poorly defined and need more review regarding their placement in this division (e.g., Eriogonum ovalifolium most commonly forms stands in subalpine settings), and perhaps overlap in concept with members of 4.B.1.Nb Western North American Alpine Tundra Division (D043). A single alliance (Juniperus californica Mojave Scrub Alliance (A0502)) within Great Basin-Intermountain Dry Shrubland & Grassland Macrogroup (M171) may overlap in concept with types in 1.B.2.Nc Western North American Pinyon - Juniper Woodland & Scrub Division (D010), but probably has sufficient Mojavean floristics to remain here.
Similar NVC Types:
D039 North American Warm Desert Scrub & Grassland, note: "overlaps narrowly at the southern extremes as higher mountains with D040 and lower fans and slopes of D039 interfinger, but is easily distinguished due to presence of strong diagnostics such as Larrea tridentata, Encelia farinosa, etc."
D036 North American Western Interior Brackish Marsh, Playa & Shrubland, note: "There is overlap with D036 and ~Great Basin Saltbush Scrub Macrogroup (M093)$$ in D040. However, there are generally very few phreatophytic (groundwater-dependent) species present in M093. Certain alliances, such as ~Chrysothamnus albidus Shrubland Alliance (A0834)$$ (currently within M171) are close ecologically to D036, and with further investigation, may be found to best fit there."
D031 Western North American Temperate & Boreal Freshwater Marsh, Wet Meadow & Shrubland, note: "Within D040, some of the mesic associations in ~Artemisia cana ssp. bolanderi - Artemisia cana ssp. viscidula Steppe & Shrubland Alliance (A3200)$$, in G304/M169) verge on moist meadow settings that are part of D031."
D327 Californian Scrub & Grassland, note:
Physiognomy and Structure: The vegetation contains both open to dense shrublands dominated by largely pubescent gray-green evergreen shrubs that form a canopy of from 0.5 m to 4 m in height and herbaceous species, including grasses and forbs, may be sparse or dense with or without a shrub canopy. Trees are widely scattered or absent in drier stands or early- to mid-seral stands, but in the case of Juniperus may increase in cover in stands with long fire-return intervals and relatively high annual precipitation. In rocky areas, shrublands tend to be clumped and sparse with higher proportion of small-leaved or scale-leaved species, some with photosynthetic branches (Ericameria, Ephedra). Grasslands may be dominated by midsize (Pascopyrum, Pseudoroegneria), or small (Poa, Festuca ) bunchgrasses, or by annuals which produce considerable residual dry material (e.g., Bromus, Taeniatherum, Ventenata).
Floristics: Taller taxa of Artemisia (Artemisia tridentata and its subspecies Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, and Artemisia tridentata ssp. xericensis) along with Artemisia tripartita and Purshia tridentata characterize some parts of the division, as do shorter taxa of Artemisia (Artemisia arbuscula, Artemisia bigelovii, Artemisia nova, and others) and midsize shrubby species in the Amaranth family (Atriplex, Grayia, etc.). Species of Ephedra, Ericameria, Chrysothamnus, and Eriogonum commonly occur.

The subshrub Artemisia species or similarly low-growing subshrubs dominate on shallow, rocky soil or heavy clay soils and in exposed rocky, subalpine settings (Tisdale 1994a, 1994b). These taxa include 10 separate taxa of low or small Artemisia, which segregate geographically and edaphically, including Artemisia arbuscula, Artemisia bigelovii, Artemisia nova, Artemisia rothrockii, Artemisia pygmaea, Artemisia rigida, Artemisia pedatifida, Artemisia frigida, and non-wetland Artemisia cana communities. On the plateaus and mountains of the southern Great Basin bordering on the southwestern warm deserts are an array of distinctive shrublands, including leaf-succulent Yucca and Nolina species, and a variety of shrub genera (Buddleja, Coleogyne, Mortonia, Poliomintha, etc.) not found elsewhere in this division (West 1983d).

Grasslands are generally patchy within this landscape, locally restricted to sandy or loamy soils and to areas with high fire frequencies. Throughout the northern and western portions of the Great Basin grasslands are predominantly cool-season species, including Achnatherum (= Stipa), Hesperostipa, Poa, Festuca, Elymus, Pascopyrum, and Pseudoroegneria (Tisdale 1994c). In the southern and eastern portions, warm-season grass genera (e.g., Pleuraphis, Bouteloua, Muhlenbergia) increase. Intermediate moisture and fire conditions have shrub-steppe, with a combination of Artemisia species and mostly perennial grasses and herbs (West 1983c, Young et al. 2007b). Early-seral shrublands dominated by Ericameria and other short-lived shrubs occur in recovering burns, cleared land, or in intermittently flooded washes. Ruderal grassland dominated and characterized by non-native Eurasian annuals (e.g., Bromus tectorum, Taeniatherum caput-medusae) and perennial grasses (e.g., Agropyron cristatum) has, through the effects of recent fire, converted many thousands of acres of native shrubland and shrub-steppe in the past 75-100 years (Johnson 1986d, Updike et al. 1990, Whisenant 1990, Petersen 2003).

Ruderal non-native grasses and forbs from Eurasia characterize human-disturbed stands
Dynamics: The current dynamics within this division are products of both natural and anthropogenic disturbance. Natural fire frequencies in the division are variable. Summer thunderstorms generate thousands of lightning strikes annually. Despite the sensitivity of most of the dominant shrub species to fire (Callison et al. 1985, Updike et al. 1990), historically fire did not burn extensive areas of Great Basin upland scrub due to lower fuel cover and natural rocky fuel breaks. Fire frequently burned more continuous stands of grasslands in the Palouse Prairie of eastern Washington (now largely converted to agriculture) and on the borders of the shortgrass prairie in eastern Montana, Wyoming, and north-central Colorado. Stands of Artemisia arbuscula (low sagebrush) in mountainous areas and scattered rocky upland shrublands were subject to small infrequent fires and local effects of drought, rockfall, and avalanches. The extensive basin margin stands of Atriplex canescens (saltbush) were affected by drought and disease and limited fire (due to lack of herbaceous fuels). Currently, with the advent of extensive invasive species, such as Bromus tectorum, Ventenata dubia, Taeniatherum caput-medusae, and a variety of taller annual forbs such as Sisymbrium sp., Descurainia sp., Centaurea sp., and Salsola tragus, fires carry more continuously through many of the shrublands of this division, causing widespread type-conversion (Johnson 1986, Updike et al. 1990, Whisenant 1990, Petersen 2003). Grazing intensity in some areas has increased flashy annual herb cover relative to shrub cover. Subtle combinations of fire suppression and climatic shifts to slightly moister conditions in part of the region are responsible for expansion of conifers such as Juniperus occidentalis (Miller et al. 2008) or Abies concolor (Vale 1975) into parts of this division.
Environmental Description: This division includes extensive shrublands dominated by Artemisia tridentata, involving four main varieties, each with distinctive ecologies, ranging from mid- to upper slopes and deep to shallow soils (Meyer and Monsen 1992, McArthur 1994). It also includes extensive Atriplex shrublands, largely restricted to lower slopes and basins (Billings 1949).

Climate: The overall climate of the range of this division is in the Köppen bioclimatic zone Mid-latitude Dry Semiarid Steppe (BSk) with smaller areas of Mid-latitude Dry Arid Desert (BWk)

Soil/substrate/hydrology: With few exceptions, vegetation in this division tends to avoid regularly flooded or saturated low-lying landscapes (Ganskopp 1986). Stands range from high plateaus and ridges with skeletal soils to deep well-drained alluvial soils on fans and near washes and heavy clay "self-churning" Vertisols. Certain vegetation, such as the Artemisia arbuscula ssp. longiloba alliance, is restricted to heavy clay soils derived from volcanic rock. The Atriplex corrugata alliance is limited to sites with shale-derived clay soils. Some were limited to loess (e.g., Palouse Prairie, now largely eliminated by human conversion to agriculture). Soils harboring stands of certain ruderal vegetation (e.g., Acroptilon repens, Isatis tinctoria, Sisymbrium sp.) tend to occur on previously cultivated sites where the soil profile has been disrupted.

Biogeography: The genus Artemisia is well represented with 29 species largely endemic to the Great Basin Province and within the range of the division, about 42% of all North American Artemisia (fide BONAP 2010). Atriplex is represented by 21 species (23% of the North American total Atriplex species). Ericameria is represented by 7 or 8 species (about 20% of the genus in the continent). Several genera of rosaceous shrubs (Coleogyne, Fallugia, Purshia) are largely endemic to the vegetation in this division. Other widespread cool semi-desert shrub genera found in Eurasia include Ephedra and Krascheninnikovia, and grass genera such as Elymus, Poa, and Festuca.
Geographic Range: This division occurs from south-central Alberta, south through the Great Basin of western North America to the plateaus and mountains of New Mexico and westward to dry-interior southeastern British Columbia and the western Dakotas (West 1988), and south through eastern Oregon and interior California, into the mountains of northwestern Baja California, Mexico. Throughout most of the northern and central range this vegetation occurs below 1800 m, but in the southern portion it may exist in subalpine settings of over 3000 m.
Nations: CA, MX, US
States/Provinces: AB, AZ, BC, CA, CO, ID, MT, MXBC, NM, NV, OR, UT, WA, WY
US Forest Service Ecoregions (2007)
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Plot Analysis Summary:
Confidence Level: High
Confidence Level Comments:
Grank: GNR
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Concept Lineage:
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Synonomy: = Great Basin desertscrub (Turner 1982c) [is equivalent except for the inclusion of Sarcobatus vermiculatus.]
? Intermountain Valleys and Lower Mountain Slopes (West and Young 2000)
= North American Temperate Desert and Semi-desert (West 1983f) [See also treatments within this reference.]
Concept Author(s): N.E. West (1983f)
Author of Description: T. Keeler-Wolf and M.S. Reid
Acknowledgements:
Version Date: 06Jan2016
References:
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  • Billings, W. D. 1949. The shadscale vegetation zone of Nevada and eastern California in relation to climate and soils. The American Midland Naturalist 42(1):87-109.
  • BONAP [The Biota of North America Program]. 2010. North American Plant Atlas. The Biota of North America Program, Chapel Hill, NC. [http://www.bonap.org/napa.html]
  • Callison, J., Jr., J. D. Brotherson, and J. E. Bowns. 1985. The effects of fire on the blackbrush (Coleogyne ramosissima) community of southwestern Utah. Journal of Range Management 38(6):535-538.
  • Dillman, A. C. 1946. The beginnings of crested wheat grass in North America. Journal of the American Society of Agronomy 38:237-250.
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  • Ganskopp, D. C. 1986. Tolerances of sagebrush, rabbitbrush, and greasewood to elevated water tables. Journal of Range Management 39(4): 334-337.
  • Johnson, K. L., editor. 1986d. Crested wheat grass: Its values, problems and myths. Symposium proceedings; October 3-7, 1983. Utah State University, Logan, UT.
  • McArthur, E. D. 1994. Ecology, distribution, and values of sagebrush within the Intermountain Region. Pages 347-351 in: Proceedings: Ecology and management of annual rangelands. General Technical Report INTGTR-313. USDA Forest Service, Intermountain Research Station, Ogden, UT.
  • Meyer, S. E., and S. B. Monsen. 1992. Big sagebrush germination patterns: Subspecies and population differences. Journal of Range Management 45:87-93.
  • Miller, R. F., R. J. Tausch, E. D. McArthur, D. D. Johnson, and S. C. Sanderson. 2008. Age structure and expansion of piñon-juniper woodlands: A regional perspective in the Intermountain West. Research Paper RMRS-RP-69. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO. 15 pp.
  • Neal, D. L. 1994. Bitterbrush--SRM 210. Page 19 in: T. N. Shiflet, editor. Rangeland cover types of the United States. Society for Range Management, Denver, CO.
  • Peterson, E. B. 2003. Mapping percent-cover of the invasive species Bromus tectorum (cheatgrass) over a large portion of Nevada from satellite imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno. Nevada Natural Heritage Program, Carson City, NV.
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  • Tisdale, E. W. 1994b. Low sagebrush--SRM 406. Pages 45 in: T. N. Shiflet, editor. Rangeland cover types of the United States. Society for Range Management, Denver, CO.
  • Tisdale, E. W. 1994c. Bluebunch wheat grass--SRM 101. Page 1 in: T. N. Shiflet, editor. Rangeland cover types of the United States. Society for Range Management, Denver, CO.
  • Tisdale, E. W. 1994d. Basin big sagebrush--SRM 401. Page 40 in: T. N. Shiflet, editor. Rangeland cover types of the United States. Society for Range Management, Denver, CO.
  • Turner, R. M. 1982c. Great Basin desertscrub. Desert Plants 4:145-155.
  • Updike, D. R., E. R. Loft, and F. A. Hall. 1990. Wildfires on big sagebrush/antelope bitterbrush range in northeastern California: Implications for deer populations. Pages 41-46 in: Proceedings of a symposium on cheat grass invasion, shrub die-off and other aspects of shrub biology and management. General Technical Report INT-276. USDA Forest Service, Intermountain Research Station, Odgen, UT.
  • Vale, T. R. 1975. Invasion of big sagebrush (Artemisia tridentata) by white fir (Abies concolor) on the southeastern slopes of the Warner Mountains, California. Great Basin Naturalist 35:319-324.
  • West, N. E. 1983a. Great Basin-Colorado Plateau sagebrush semi-desert. Pages 331-349 in: N. E. West, editor. Temperate deserts and semi-deserts. Ecosystems of the world, Volume 5. Elsevier Publishing Company, Amsterdam.
  • West, N. E. 1983c. Western Intermountain sagebrush steppe. Pages 351-374 in: N. E. West, editor. Temperate deserts and semi-deserts. Ecosystems of the world, Volume 5. Elsevier Publishing Company, Amsterdam.
  • West, N. E. 1983d. Colorado Plateau-Mohavian blackbrush semi-desert. Pages 399-412 in: N. E. West, editor. Temperate deserts and semi-deserts. Ecosystems of the world, Volume 5. Elsevier Publishing Company, Amsterdam.
  • West, N. E. 1988. Intermountain deserts, shrub steppes, and woodlands. Pages 207-230 in: M. G. Barbour and W. D. Billings, editors. North American terrestrial vegetation. Cambridge University Press, New York.
  • West, N. E., and J. A. Young. 2000. Intermountain valleys and lower mountain slopes. Pages 255-284 in: M. G. Barbour and W. D. Billings, editors. North American Terrestrial Vegetation, second edition. Cambridge University Press, Cambridge.
  • West, N. E., editor. 1983f. Ecosystems of the World. Volume 5: Temperate deserts and semi-deserts. Elsevier Publishing Company, Amsterdam.
  • Whisenant, S. G. 1990. Changing fire frequencies on Idaho's Snake River Plains: Ecological and management implication. Pages 4–10 in: Proceedings: symposium on cheatgrass invasion, shrub die-off, and other aspects of shrub biology and management. General Technical Report INT-276. USDA Forest Service, Intermountain Research Station, Ogden, UT.
  • Young, J. A., C. D. Clements, and H. C. Jansen. 2007b. Sagebrush steppe. Pages 587-608 in: M. G. Barbour, T. Keeler-Wolf, and A. Schoenherr, editors. Terrestrial vegetation of California, third edition. University of California Press, Berkeley, CA.