Print Report
A1290 Achnatherum speciosum Grassland Alliance
Type Concept Sentence: This grassland is documented from the Mojave Desert and dominated by Achnatherum speciosum, which is the sole dominant or important plant in the herbaceous layer.
Common (Translated Scientific) Name: Desert Needlegrass Grassland Alliance
Colloquial Name: Desert Needlegrass Grassland
Hierarchy Level: Alliance
Type Concept: Stands of this alliance are dominated by Achnatherum speciosum, which is the sole dominant or important plant in the herbaceous layer. Species composition varies among stands, but Achnatherum speciosum is the unifying species. Other graminoids which may be present include Achnatherum hymenoides, Elymus elymoides, Nassella cernua, Nassella lepida, and Poa secunda. Scattered emergent shrubs such as Hymenoclea salsola may be present. This uncommon grassland is documented from the Mojave Desert. It grows in very xeric conditions with hot summers and occasional freezes in the winter. This alliance requires well-drained rocky or sandy soils. It was formerly widespread, but overgrazing has decimated stands. Remaining stands occur from 600-1000 m elevation on flat ridges, lower slopes, valleys, and washes.
Diagnostic Characteristics: Vegetation appears to be endemic to the Mojave Desert and is characterized by dominance or codominance of the perennial grass Achnatherum speciosum having >50% of the total herbaceous cover.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: No Data Available
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This graminoid-dominated alliance typically is less than 1 m in height. The herbaceous layer can vary from open to fairly continuous. Scattered, emergent shrubs may be present.
Floristics: Stands of this alliance are dominated by Achnatherum speciosum (= Stipa speciosa) which is the sole dominant or important plant in the herbaceous layer. Species composition varies among stands, but Achnatherum speciosum is the unifying species. Other graminoids which may be present include Achnatherum hymenoides (= Oryzopsis hymenoides), Elymus elymoides, Nassella cernua, Nassella lepida, and Poa secunda. Scattered emergent shrubs such as Hymenoclea salsola may be present.
Dynamics: Plants of this alliance evolved in a very xeric environment with infrequent disturbance. Fires were not well-supported by the light plant cover, and grazing pressure was very light due to the low carrying capacity of the environment. The impact of cattle and sheep grazing and the consequent introduction of exotic plants such as Bromus tectorum have reduced stands of this alliance to a few dozen across its range.
Environmental Description: This grassland of the Mojave Desert grows in very xeric conditions with hot summers and occasional freezes in the winter. This alliance requires well-drained rocky or sandy soils. It was formerly widespread, but overgrazing has decimated stands. Remaining stands occur from 600 to 1000 m elevation on flat ridges, lower slopes, valleys, and washes.
Geographic Range: This alliance was once widespread throughout the Mojave Desert but has been reduced to scattered stands by overgrazing. It is reported from California and Utah.
Nations: US
States/Provinces: CA, UT
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899106
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: G4
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 | A1290 Desert Needlegrass Grassland Alliance | A1290 | 3.B.1.Ne.1.c |
| Association | CEGL003112 Desert Needlegrass Grassland | CEGL003112 | 3.B.1.Ne.1.c |
| Association | CEGL003113 Desert Needlegrass Shrub Grassland | CEGL003113 | 3.B.1.Ne.1.c |
Concept Lineage: equivalent to A.1290.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Achnatherum speciosum (Desert needlegrass grassland) Alliance (Sawyer et al. 2009) [41.090.00]
= Achnatherum speciosum Herbaceous Alliance (Evens et al. 2012)
= Achnatherum speciosum Herbaceous Alliance (Evens et al. 2014)
= Achnatherum speciosum Herbaceous Alliance (CNPS 2017) [41.090.00]
< Desert needlegrass series (Sawyer and Keeler-Wolf 1995)
>< Valley Needlegrass Grassland (#42110) (Holland 1986b)
= Achnatherum speciosum Herbaceous Alliance (Evens et al. 2012)
= Achnatherum speciosum Herbaceous Alliance (Evens et al. 2014)
= Achnatherum speciosum Herbaceous Alliance (CNPS 2017) [41.090.00]
< Desert needlegrass series (Sawyer and Keeler-Wolf 1995)
>< Valley Needlegrass Grassland (#42110) (Holland 1986b)
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