Achnatherum speciosum Herbaceous Alliance
Desert needlegrass grassland
Desert needlegrass grassland
USDA Ecological Section Map
Summary Information
- Primary Life FormHerb
- Elevation0-3400 m
- State RarityS2.2
- Global RarityG4
- DistributionCAN: BC: USA: CA, NV, CO?, NM?, OR?, WA?. Mexico? (TJM2) (USDA Plants)
- Endemic to CaliforniaNo
- Endemic to California Floristic Province and DesertsNo
- Date Added1995/11/01
Characteristic Species
Achnatherum speciosum is dominant or co-dominant in the herbaceous layer with Achnatherum hymenoides, Elymus elymoides, Nassella cernua, Nassella lepida and Poa secunda. Emergent trees and shrubs may be present at low cover, including trees Juniperus californica or Yucca brevifolia and shrubs:Ambrosia salsola, Artemisia tridentata, Coleogyne ramosissima, Ericameria cooperi, Ericameria linearifolia, Ericameria teretifolia, Grayia spinosa and Krascheninnikovia lanata.
Vegetation Layers
Herbs < 1 m; cover is open to intermittent.
Membership Rules
- Achnatherum speciosum > 50% relative cover in the herbaceous layer (Thomas et al. 2004).
Habitats
Lower slopes, swales, rocky hills, flat ridges, talus slopes, and , and in canyons, and on sandy or gravelly alluvial fans. Soils are coarse- textured with no profile development.
Other Habitat, Alliance and Community Groupings
| MCV (1995) | Desert needlegrass series |
| NVCS (2009) | Achnatherum speciosum herbaceous alliance |
| Calveg | Perennial grasses and forbs |
| Holland | Mojave mixed steppe, Native grassland |
| Munz | Creosote bush scrub |
| WHR | Desert scrub, Perennial grassland |
| CDFW CA Code | 41.090.00 |
National Vegetation Classification Hierarchy
| Formation Class | Xeromorphic Scrub and Herb Vegetation (Semi-Desert) |
| Formation Subclass | Cool Semi-Desert Scrub and Grassland |
| Formation | Cool Semi-Desert Scrub and Grassland |
| Division | Western North American Cool Semi-Desert Scrub and Grassland |
| Macro Group | Inter-Mountain Dry Shrubland and Grassland |
| Group | Southern Great Basin semi-desert grassland group |
Remarks
Achnatherum speciosum is a native, cool-season, perennial bunchgrass. It grows in large, dense clumps that have persistent leaf bases. The species reproduces asexually with tiller growth and sexually by seed. Seed crop size is closely tied to adequate moisture and temperature conditions. The grass has persistent seed and seedling banks, and seeds are self-planting (Pavek 1993c). It is often referred to as Stipa speciosa in botanical literature.
Achnatherum speciosum occurs as a species in a wider range than does the alliance. In California, for example, A. speciosum occurs west of the desert in the dry, interior South Coast ranges of Fresno Co. However, the alliance is known from relatively few stands in transmontane California. Known stands are in upper-desert settings, adjacent to stands dominated by Coleogyne ramosissima, Ericameria teretifolia, Grayia spinosa, Juniperus californica, or Yucca brevifolia. Its rarity is likely a function of the natural disturbance regimes necessary for its development. However, its rarity is also likely a function of the invasion of non-native annual grasses that have altered fire frequencies.
Achnatherum speciosum occurs as a species in a wider range than does the alliance. In California, for example, A. speciosum occurs west of the desert in the dry, interior South Coast ranges of Fresno Co. However, the alliance is known from relatively few stands in transmontane California. Known stands are in upper-desert settings, adjacent to stands dominated by Coleogyne ramosissima, Ericameria teretifolia, Grayia spinosa, Juniperus californica, or Yucca brevifolia. Its rarity is likely a function of the natural disturbance regimes necessary for its development. However, its rarity is also likely a function of the invasion of non-native annual grasses that have altered fire frequencies.
Life History Traits of the Principal Species
| Achnatherum speciosum | |
|---|---|
| Life forms | Polycarpic perennial; herb |
| Seed storage | Soil |
| Seed longevity | Medium |
| Mode of dispersal | Animal; wind |
| Germination agents | None |
| Mode of sprouting | Underground structures |
| Survivability after fire/disturbance | Fire-hardy; high sprouter |
| Disturbance-stimulated flowering | No |
| Reproductive range | 1-50 years |
| Recruitment | Low |
| Regional variation | Low |
Fire Characteristics
Stands appear associated with past burns that occur in the late summer or fall. The stands occupy areas where fire frequencies are moderate to relatively high, such as in the borderland between desert and chaparral types. Individuals of Achnatherum speciosum survive fires, sprout rapidly, set seed, and colonize burned areas more rapidly than the formerly dominant shrubs (Humphrey 1974). However, the presence of Bromus rubens, Schismus spp., and other non-natives increases fire frequencies, and the invasive qualities of these species impose a decline on the importance of this bunchgrass.
| Fire return interval | Medium |
| Seasonality | Late summer-fall |
| Size/extent | Small to large; up to stand size |
| Complexity | Low to moderate |
| Intensity | Low to moderate |
| Severity | High |
| Type | Surface |
| Regional knowledge | Mojave Desert |
Regional Status
- Mojave Desert (322Ag). Stands are generally open and may contain annual native wildflower displays. Surrounding shrub vegetation is generally well stocked with Achnatherum speciosum, suggesting that with appropriate fire intensity and frequency, grass stands could increase (Thomas et al. 2004). Regular grazing occurs in some of these stands at Tejon Ranch; at the current stocking rate, they appear to be viable. Antelope Valley stands are generally small (< 30 ha) and are interspersed among larger stands of Ericmeria linearifolia, Juniperus californica, and Yucca brevifolia alliances. California Vegetation Information System (CVIS 1995) has plot data on file from Kern and Los Angeles Cos. The grass has invaded lands cleared for agriculture (Desert Workshop 2000).
- Sierra Nevada (M261Er). The few stands known are at the southern and eastern base of the Tehachapi Mountains. They occur in similar circumstances to western Mojave stands of the Antelope Valley. Some are within wind farm holdings and have been impacted by associated development.
- Southeastern Great Basin (341Ff). The only known stands in the section occur in the Panamint Mountains, adjacent to stands of Artemisia tridentata and Coleogyne ramosissima alliances. The irregular boundaries of the stands suggest they are defined by the extent of old burns. Stands are generally < 50 ha.
Management Considerations
This alliance is currently rare but may have been more common prior to the invasion of non-native grasses and under different fire regimes. Old rangeland records in the western Mojave Desert suggest Achnatherum speciosum was once common and widespread (Desert Workshop 2000). Intensive sheep grazing over 100 years ago may have reduced its range.
In its natural state, the alliance was probably a relatively short-lived but important type associated with small, irregularly occurring fires in mid- to upper-elevation desert shrub types. Stands of associated shrublands with a significant component of A. speciosum should be identified and monitored for a better understanding of the shrub/grassland relationships to perpetuate this phase of natural desert systems.
Associations
- Achnatherum speciosum Shrub [1], [2], [3], [4]
References
- [1] Keeler-Wolf, T.;Thomas, K. 2000
- [2] Evens, J.M.;Sikes, K.;Hastings, D.;Ratchford,J.S. 2014
- [3] Buck-Diaz, J.;Harbert, B.;Evens, J. 2011
- [4] Buck-Diaz, J.;Ratchford, J.;Evens, J. 2013
- Humphrey, R.R. 1974
- Keeler-Wolf, T.;Evens, J.M.;Solomeshch, A.I.;Holland, V.L.;Barbour, M.G. 2007
- Menke, J.;Reyes, E.;Hepburn, A.;Johnson, D.;Reyes, J. 2013
- Pavek, D.S. 1993c
- Reid, M.S.;Schulz, K.A.;Cormer, P.J.;Schindel, M.H.;Culver, D.R.;Sarr, D.A.;Damm, M.C. 1999
- Sawyer, J.O.;Keeler-Wolf, T. 1995
- Thomas, K.;Franklin, J.;Keeler-Wolf, T.;Stine, P. 2004
- Tueller, P.T.;Tausch, R.J.;Bostick, V. 1991
- Vasek, F.C.;Thorne, R.F. 1977
- VegCAMP (CDFW Vegetation Classification and Mapping Program);AIS, 2013