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CEGL001705 Hesperostipa comata Great Basin Grassland

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: Needle-and-Thread Great Basin Grassland

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: This semi-arid grassland occurs on the Great Basin and Colorado Plateau and high plateaus of southern Utah, east into the western slope of the southern Rocky Mountains. The vegetation is characterized by a relatively sparse to moderate herbaceous layer (10-40% cover) that is strongly dominated by the medium-tall, cool-season bunchgrass Hesperostipa comata, but it may also include stands with less than 10% total vegetation cover. Low cover of other grasses, such as Achnatherum hymenoides, Achnatherum lettermanii, Aristida purpurea, Elymus elymoides, Koeleria macrantha, Leymus salinus, Pleuraphis jamesii, Poa fendleriana, or Sporobolus cryptandrus, may be present. However, Bouteloua eriopoda is not present. Forb cover ranges from sparse to moderate and may be diverse. Associated forbs include Balsamorhiza sagittata, Hymenopappus filifolius, Machaeranthera canescens, Sphaeralcea coccinea, Vicia americana, and species of Antennaria, Astragalus, Cryptantha, Eriogonum, Gilia, and Lappula. Scattered shrubs and dwarf-shrubs may be present with less than 5% total cover. Common species include Artemisia tridentata, Chrysothamnus viscidiflorus, Ericameria nauseosa, Gutierrezia sarothrae, Krascheninnikovia lanata, Opuntia polyacantha, and Symphoricarpos oreophilus. The widespread introduced annual grass Bromus tectorum often contributes significant cover in disturbed stands. Some stands have high cover of biological soil crusts. Stands are found on a variety of sites, such as on point bars, stream terraces, in sand-filled potholes in slickrock washes, on plains, valleys, canyon floors, gentle hillslopes, knolls and bluffs, mesatops, and plateau parks. Sites are generally flat to gently sloping, but occasionally are steep (to 53% slope). Soils are variable and range from sand to silty clay. The unvegetated surface has moderate to high cover of bare soil with sparse to moderate cover of litter. Fires may be important in maintaining these grasslands by reducing woody cover, but burning during the growing season could also damage Hesperostipa comata plants.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This association is largely known and described from National Park Service inventory efforts in the Colorado Plateau. It is composed of relatively pure Hesperostipa comata grasslands in the Intermountain West. The similar associations are distinguished by the codominance by other grass species or presence of a shrub layer.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available

Floristics: This association is characterized by a relatively sparse to moderate herbaceous layer (10-40% cover) that is strongly dominated by the medium-tall, cool-season bunchgrass Hesperostipa comata, but it may also include stands with less than 10% total vegetation cover. Low cover of other grasses, such as Achnatherum hymenoides, Achnatherum lettermanii, Aristida purpurea, Bouteloua gracilis, Elymus elymoides, Koeleria macrantha, Leymus salinus, Muhlenbergia pungens, Pleuraphis jamesii, Poa fendleriana, Poa secunda, Sporobolus airoides, Sporobolus contractus, or Sporobolus cryptandrus, may be present. However, Bouteloua eriopoda is not present. Forb cover ranges from sparse to moderate and may be diverse. Associated species include Artemisia campestris, Artemisia dracunculus, Artemisia ludoviciana, Balsamorhiza sagittata, Cirsium arizonicum, Cryptantha crassisepala, Hymenopappus filifolius, Machaeranthera canescens, Sphaeralcea coccinea, Vicia americana, and species of Antennaria, Astragalus, Eriogonum, Gilia, and Lappula. Scattered shrubs and dwarf-shrubs may present with less than 5% total cover. Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. vaseyana, Atriplex canescens, Chrysothamnus depressus, Chrysothamnus viscidiflorus, Ericameria nauseosa, Gutierrezia sarothrae, Krascheninnikovia lanata, Opuntia polyacantha, Purshia tridentata, Ribes cereum, and Symphoricarpos oreophilus have been reported from this grassland. The widespread introduced annual grass Bromus tectorum often contributes significant cover in disturbed stands. Several other exotic species may be present to abundant and include Salsola tragus, Bassia scoparia (= Kochia scoparia), Poa pratensis, Sisymbrium altissimum, and Tragopogon dubius. Some stands have high cover of cryptogams on the soil, including Enchylium tenax (= Collema tenax), Tortula ruralis, Tetramelas papillatus (= Buellia papillata), and Gyalolechia bracteata (= Fulgensia bracteata) (Kleiner and Harper 1977).

Dynamics:  These grasslands are dominated by relatively deep-rooted grasses that use soil moisture below 0.5 m during the typically dry summers. The coarse-textured soils allow for rapid infiltration and storage of winter and summer precipitation (Kleiner 1968, Daubenmire 1970, Kleiner and Harper 1977, Thilenius et al. 1995). However, during the severe drought of 2002, there was widespread die-off of Hesperostipa comata throughout the northern Colorado Plateau (J. Coles pers. obs. 2005). Fires when the grasses are dormant may be important in maintaining these grasslands by reducing woody cover. However, burning during the growing season generally kills or severely damages Hesperostipa comata plants. After fire, regeneration of this non-rhizomatous bunchgrass is by seed and may take many years to reach pre-fire densities (FEIS 1998).
Environmental Description:  This grassland occurs on the Great Basin and Colorado Plateau east into the western slope of the southern Rocky Mountains. Stands are found a variety of sites, such as on point bars, stream terraces, in sand-filled potholes in slickrock washes, on plains, valleys, canyon floors, gentle hillslopes, knolls and bluffs, mesatops, and plateau parks. Sites are generally flat to gently sloping, but occasionally are steep (to 53% slope). Elevation ranges from 1250-2683 m. The unvegetated surface has moderate to high cover of bare soil with sparse to moderate cover of litter. Biological soil crusts are often present with low cover. Soils are variable and include sand, cobbles, sandy, silt and clay loams and silty clay. Common parent materials are sandstones and shale that have been eroded and redistributed in alluvial and eolian deposits, but include Tertiary volcanic rocks. Fires may be important in maintaining these grasslands by reducing woody cover, but burning during the growing season could also damage Hesperostipa comata plants.
Geographic Range: This grassland is found on the west slope of the Colorado Rocky Mountains, on the Colorado Plateau and in the Great Basin in Colorado and Utah, and probably occurs in adjacent states.

Nations: US

States/Provinces:  AZ, CO, NV, UT


Confidence Level: High

Confidence Level Comments: No Data Available
Grank: G2G4

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.1 Yellow Rabbitbrush - Blackbrush / Indian Ricegrass Dry Shrubland & Grassland Macrogroup M171 3.B.1.Ne.1
Group 3.B.1.Ne.1.c James'' Galleta - Indian Ricegrass - Needle-and-Thread Semi-Desert Grassland Group G311 3.B.1.Ne.1.c
Alliance A1270 Needle-and-Thread Grassland Alliance A1270 3.B.1.Ne.1.c
Association CEGL001705 Needle-and-Thread Great Basin Grassland CEGL001705 3.B.1.Ne.1.c
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Stipa comata dominated grassland (Kleiner and Harper 1977)
Concept Author(s): K.A. Schulz

Author of Description: K.A. Schulz and J. Coles

Acknowledgements: No Data Available

Version Date: 07-14-16
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