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A3180 Atriplex obovata - Atriplex cuneata Scrub Alliance
Type Concept Sentence: This alliance occurs in the northern Chihuahuan Desert and Colorado Plateau from western Texas, south-central and northwestern New Mexico, and northeastern Arizona and is dominated or codominated by Atriplex obovata.
Common (Translated Scientific) Name: Mound Saltbush - Valley Saltbush Scrub Alliance
Colloquial Name: Mound Saltbush - Valley Saltbush Scrub
Hierarchy Level: Alliance
Type Concept: This alliance occurs in the northern Chihuahuan Desert and Colorado Plateau from western Texas, south-central and northwestern New Mexico, and northeastern Arizona. The vegetation is characterized by a sparse to moderately dense dwarf-shrub layer that is dominated or codominated by Atriplex obovata. Some occurrences may have a dense understory of perennial grasses. Shrub associates may include scattered Atriplex confertifolia, Ericameria nauseosa, Isocoma drummondii, Gutierrezia sarothrae, Prosopis glandulosa var. torreyana, Opuntia spp., or Suaeda spp. The herbaceous layer ranges from moderately dense to absent, and is usually dominated by perennial grasses such as Sporobolus airoides and Pleuraphis jamesii. Other associated species may include Achnatherum hymenoides, Bouteloua gracilis, Elymus elymoides, and Sporobolus cryptandrus. Stands are known from mesas, plains, floodplains, valley bottoms, alluvial flats, lower to upper hillslopes, often in a "badlands" landscape. Soils are generally shallow, poorly developed, and alkaline.
Diagnostic Characteristics: Shrub and shrub-herbaceous scrub vegetation where Atriplex obovata is the principal shrub with cover of 10-60%. Pleuraphis jamesii and Sporobolus airoides typically form an open to dense herbaceous layer.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This alliance includes associations which are considered shrub-dominated, as well as one that is considered shrub-herbaceous which was previous attributed to former Sporobolus airoides - (Pleuraphis jamesii) Shrub Herbaceous Alliance (A.1532).
This alliance often occurs in "badlands" landscapes adjacent to barren and sparsely vegetated areas and may include vegetation that may be too sparse to be classified as a dwarf-shrubland. Further study is needed throughout its range, especially to assess the effects of livestock grazing on vegetation structure.
This alliance often occurs in "badlands" landscapes adjacent to barren and sparsely vegetated areas and may include vegetation that may be too sparse to be classified as a dwarf-shrubland. Further study is needed throughout its range, especially to assess the effects of livestock grazing on vegetation structure.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation in this alliance is dominated by sparse to moderate cover of facultatively deciduous dwarf-shrubs with a sparse to dense perennial graminoid layer.
Floristics: The vegetation is characterized by a sparse to locally moderately dense dwarf-shrub layer (10-60% cover) that is dominated or codominated by Atriplex obovata (3-40% cover). Shrub associates may include scattered Atriplex confertifolia, Atriplex canescens, Artemisia bigelovii, Ericameria nauseosa, Gutierrezia sarothrae, Isocoma drummondii, Opuntia spp., Prosopis glandulosa var. torreyana, or Suaeda spp. The herbaceous layer ranges from moderately dense to absent (0-50% cover) and is usually dominated by perennial grasses such as Sporobolus airoides and Pleuraphis jamesii. Other associated species may include Achnatherum hymenoides, Bouteloua gracilis, Elymus elymoides, and Muhlenbergia torreyi. Forb cover is sparse and typically includes Astragalus spp. and Sphaeralcea coccinea.
Dynamics: Grazing has significantly impacted much of the vegetation in the Rio Puerco basin of northwestern New Mexico, which has had a long history of settlement and heavy livestock use. With proper livestock management and time, palatable species such as Sporobolus airoides may increase and Opuntia spp. may decline (Francis 1986).
Environmental Description: Elevation ranges from 1500-1850 m. Stands are known from mesas, plains, floodplains, valley bottoms, alluvial flats, lower to upper hillslopes, often in a "badlands" landscape. Soils are generally shallow, poorly developed, and alkaline. Textures range from fine sandy loam to silty clay loam and clay (Henrickson 1974, Francis 1986, TNC 1997b) which are often saline or gypseous. Parent materials include alluvium and colluvium derived from igneous or sedimentary materials such as basalt, shale, and clay. There is high cover of bare soil. Typically, areas have been severely degraded by erosion.
Geographic Range: Communities in this alliance are described from the southeastern part of the Colorado Plateau in the upper Rio Puerco watershed in northwestern New Mexico and Arizona; the Trans-Pecos region in Brewster County, western Texas; and in south-central New Mexico. The alliance probably also occurs in Utah and Chihuahua and Coahuila, Mexico.
Nations: MX?,US
States/Provinces: AZ, MXCHH?, MXCOA, NM, TX, UT
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899305
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: No Data Available
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