Intermountain Saltbush Flats

This ecological system occurs on gentle slopes and rolling plains in the northern Colorado Plateau and Uinta Basin on Mancos shale and arid, windswept basins and plains across parts of Wyoming. It is also found in eastern Wyoming in Great Plains areas and may extend north into Montana and Canada. These landscapes typically support dwarf-shrublands composed of relatively pure stands of Atriplex spp., such as Atriplex corrugata (in Colorado and Utah), Atriplex gardneri (Wyoming and Montana into Canada), or Atriplex falcata (Columbia Plateau and northern Great Basin). Other dominant or codominant dwarf-shrubs may include Artemisia longifolia, Artemisia pedatifida (very important in Wyoming, rare in Colorado stands), or Picrothamnus desertorum, sometimes with other low shrubs, such as Krascheninnikovia lanata or Tetradymia spinosa. Atriplex confertifolia or Atriplex canescens may be present but do not codominate. Artemisia tridentata ssp. wyomingensis can occur in local patches within this system. The herbaceous layer is typically sparse. Scattered perennial forbs occur, such as Oenothera spp., Phacelia spp., Sphaeralcea grossulariifolia, Stanleya pinnata, and Xylorhiza glabriuscula; perennial grasses Achnatherum hymenoides, Bouteloua gracilis (not in Wyoming), Distichlis spicata, Elymus elymoides, Elymus lanceolatus ssp. lanceolatus, Pascopyrum smithii, Pleuraphis jamesii, Poa secunda, or Sporobolus airoides may comprise the herbaceous layer. In less saline areas, there may be inclusions of grassland patches dominated by Hesperostipa comata, Leymus salinus, Pascopyrum smithii, or Pseudoroegneria spicata. Substrates are shallow, typically saline, alkaline, fine-textured soils developed from shale or alluvium and may be associated with shale badlands. Infiltration rate is typically low. In Wyoming and possibly elsewhere, inclusions of non-saline, gravelly barrens or rock outcrops dominated by cushion plants such as Arenaria hookeri and Phlox hoodii without dwarf-shrubs may be present (these are not restricted to this system). Annuals are seasonally present and may include Eriogonum inflatum, Monolepis nuttalliana, Plantago tweedyi, and the introduced annual grass Bromus tectorum. In Montana, Atriplex gardneri also occurs associated with Great Plains badlands, and determining which system it falls into may be difficult.

This ecological system typically supports dwarf-shrublands composed of relatively pure stands of Atriplex spp., such as Atriplex corrugata or Atriplex gardneri. Other dominant or codominant dwarf-shrub may include Artemisia longifolia, Artemisia pedatifida, or Picrothamnus desertorum, sometimes with a mix of other low shrubs, such as Krascheninnikovia lanata or Tetradymia spinosa. Atriplex confertifolia or Atriplex canescens may be present but do not codominate. The herbaceous layer is typically sparse. Scattered perennial forbs occur, such as Xylorhiza glabriuscula and Sphaeralcea grossulariifolia, and the perennial grasses Achnatherum hymenoides, Bouteloua gracilis, Elymus elymoides, Elymus lanceolatus ssp. lanceolatus, Pascopyrum smithii, or Sporobolus airoides may dominate the herbaceous layer. In less saline areas, there may be inclusions of grasslands dominated by Hesperostipa comata, Leymus salinus, Pascopyrum smithii, or Pseudoroegneria spicata. In Wyoming and possibly elsewhere, vegetation dominated by cushion plants such as Arenaria hookeri and Phlox hoodii without dwarf-shrubs may be present and occurs on inclusions of non-saline, gravelly barrens or rock outcrops. Annuals are seasonally present and may include Eriogonum inflatum, Plantago tweedyi, and the introduced annual grass Bromus tectorum.

Climate: Climate is temperate and semi-arid. Summers are generally hot, and freezing temperatures are common in the winter. Mean annual precipitation ranges from 13-33 cm. In Montana and Wyoming, approximately two-thirds of the annual precipitation falls in spring and early summer. In Colorado and Utah, over half the precipitation occurs in the late summer monsoons as high-intensity thunderstorms.

Physiography/landform: This ecological system occurs in the intermountain western U.S. on gentle slopes and rolling plains on semi-arid, windswept plains and basins. Elevation ranges from 1150-2200 m. Stands occur on shale outcrops and plains and are nearly flat to moderately steep.

Soils/substrate/hydrology: Substrates are shallow to moderately deep, typically saline, alkaline, poorly developed, fine-textured soils but range from sandy loam to clay and may be gravelly. Soil are developed from shale, alluvium, and bentonite and may be associated with shale badlands. Infiltration rate is typically low and erosion rates are high because of poor infiltration and high runoff. In Wyoming and possibly elsewhere, inclusions of non-saline, gravelly barrens or rock outcrops may be present.

These are highly saline-tolerant and drought-tolerant shrublands. Atriplex corrugata- and Atriplex gardneri-dominated shrublands are the most saline-tolerant of the Mancos shale plant communities studied by Branson et al. (1976). Gardner's saltbush has an extensive, highly branched root system, and tolerates poor site conditions (Reed 1993b). Stands are characterized by bare ground and young to mature shrubs that have re-sprouted or established from nearby seed. Although very slow-growing, these shrubs can completely dominate these extremely saline sites (Branson et al. 1976). They are true evergreen dwarf-shrubs retaining leaves for several years. This plant utilizes winter soil moisture, beginning new growth in March when the soils are relatively warm and moist. It flowers in April and by mid-July fruits are shattered (Branson et al. 1976). If the soils dry out in midsummer, it can go dormant until the late summer monsoon rains begin. Disturbance is characterized by very wet periods that contribute to high shrub mortality every 100 years on average.

Shrub cover may be patchy and discontinuous, but cover is higher than Inter-Mountain Basin Shale Badland (CES304.789). These shrublands typically occur on flatter slopes with less severe erosion than those occupied by badland communities. This system does not have a fire regime due to discontinuous fuel (LANDFIRE 2007a). Fire can occur in conjunction with wet years possibly once every 100 years on average. Most species of Atriplex sprout after fire, recovering fully within 2 to 3 years from root sprouts (Wright 1980).

LANDFIRE developed a VDDT model for this system which has two classes (LANDFIRE 2007a, BpS 2310660):
A) Early Development 1 All Structures (10% of type in this stage): Shrub cover is 0-5%. Characterized by bare ground and young shrubs that have re-sprouted or established from nearby seed. May find some ephemeral forbs or grasses at this stage. Disturbance is characterized by very wet periods that contribute to high shrub mortality every 100 years on average. Succession to class B after 12 years.

B) Late Development 1 All Structures (90% of type in this stage): Characterized by mature shrubs (10-20% cover). Typically lacks understory vegetation. Sites at this stage are very patchy with discontinuous shrubs. Same disturbance as in class A.

The naturally sparse plant cover along with fine-grained salt soils make these shrublands particularly vulnerable to water and wind erosion, especially where vegetation has been depleted by grazing or disturbances (CNHP 2010). The dwarf-shrub Atriplex gardneri is very resilient and has been used to stabilize soils and to reclaim disturbed sites. It had one of the highest survival rates of all shrubs planted on processed oil shale in the Uinta Basin in Utah and was one of only two species to establish on coal mine spoils in Wyoming (Reed 1993b). Sites are arid and harsh with high winds and substrates that are typically highly erodible, saline, alkaline clays and silty clay soils low in phosphorous, nitrogen, and potassium. Sites are susceptible to accelerated erosion and soil loss. Sites are harsh and few other species can grow on them.

This system occurs on gentle slopes and rolling plains in the northern Colorado Plateau and Uinta Basin on Mancos shale and arid, windswept basins and plains across parts of Wyoming, and possibly into Montana and Canada.