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A3148 Yucca brevifolia Wooded Scrub Alliance

Type Concept Sentence: The vegetation is characterized by an emergent (up to 13 m tall) and typically abundant Yucca brevifolia layer over a shrub-dominated understory layer and/or a perennial graminoid-dominated layer. It is generally limited to the Mojave Desert, but may extend into the transition zone with the southern Great Basin.

Common (Translated Scientific) Name: Joshua Tree Wooded Scrub Alliance

Colloquial Name: Joshua Tree Wooded Scrub

Hierarchy Level:  Alliance

Type Concept: This alliance is generally limited to the Mojave Desert, but may extend into the transition zone with the southern Great Basin. The vegetation is characterized by an emergent (up to 13 m tall) and open canopy of Yucca brevifolia over an open to moderately dense short-shrub layer and/or a perennial graminoid-dominated layer. Yucca brevifolia must be evenly distributed with over 1% total cover. Emergent Quercus turbinella, Pinus monophylla, or Juniperus spp. may be present, but have less than 1% cover. Shrub and ground layers are variable. Shrub species may include Artemisia tridentata, Chrysothamnus viscidiflorus, Coleogyne ramosissima, Ephedra nevadensis, Eriogonum fasciculatum, Larrea tridentata, Lycium andersonii, Cylindropuntia acanthocarpa, Salazaria mexicana, Tetradymia axillaris, and Yucca schidigera. If present, the herbaceous layer is usually open to intermittent and is dominated by perennial grasses, such as Achnatherum speciosum, Pleuraphis jamesii (above 1400 m), Pleuraphis rigida, or Poa secunda, and seasonal annuals. Other graminoid species may include Achnatherum hymenoides or Muhlenbergia porteri. Forb cover is mostly from seasonal annuals. Stands are found on gentle to moderate alluvial fans, slopes and ridgetops. Stands occur at mid-elevations ranging from 750 to 2150 m. Soil types and elevation limit the distribution of the vegetation. Soils are derived from colluvial or alluvial deposits and have variable textures, ranging from gravel, coarse sand or loamy, to fine silt.

Diagnostic Characteristics: Yucca brevifolia evenly distributed at >1% cover with Juniperus and/or Pinus spp. <1% absolute cover in the tree canopy (Thomas et al. 2004).

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: The concept and description of this alliance are based on classification work done by Thomas et al. (2004) on the Mojave Ecosystem Mapping Project and Sawyer et al. (2009), and this concept has not yet been expanded to include current vegetation classification projects in the Mojave Desert and Grand Canyon. The original concept was made to include ~Yucca brevifolia - Juniperus osteosperma / Artemisia tridentata Wooded Shrubland (CEGL002744)$$, but this is noted to be a Great Basin element. Stands of vegetation with relatively sparse cover of Yucca brevifolia are included in this wooded herbaceous alliance because of the results of quantitative analysis of a large number of stands conducted by Keeler-Wolf and Thomas (2000). Although cover of Yucca brevifolia was variable, the analysis showed that even 1% cover is a good indicator for this mid- to upper-elevation Mojave Desert vegetation type as long as the cover is evenly distributed and trees species such as Pinus monophylla, Juniperus californica, or Juniperus osteosperma have less than 1% cover. The indicator species, Yucca brevifolia, is recognized at a lower cover level (<1%) than is standard for a wooded herbaceous alliance in the USNVC because of Thomas et al.''s (2004) research.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation in this alliance has an sparse to open emergent xeromorphic tree canopy (up to 12 m in height) above an open to sparse(or absent) shrub layer that is less than 3 m tall. The ground layer may be sparse to moderately dense is often dominated by perennial graminoids with sparse to abundant cacti. Annuals may be seasonally present.

Floristics: This desert vegetation is characterized by an emergent (up to 13 m tall) and open canopy of Yucca brevifolia over an open to moderately dense short shrub layer and/or a perennial graminoid-dominated layer. Yucca brevifolia must be evenly distributed with over 1% total cover (Keeler-Wolf and Thomas 2000). Emergent Quercus turbinella, Pinus monophylla or Juniperus spp. may be present, but have less than 1% cover (Sawyer et al. 2009). Shrub and ground layers are variable. Shrub species may include Artemisia tridentata, Chrysothamnus viscidiflorus, Coleogyne ramosissima, Ephedra nevadensis, Eriogonum fasciculatum, Larrea tridentata, Lycium andersonii, Cylindropuntia acanthocarpa (= Opuntia acanthocarpa), Salazaria mexicana, Tetradymia axillaris, and Yucca schidigera. Other shrubs present may include Ambrosia dumosa, Ericameria cooperi, Ericameria nauseosa, Ericameria linearifolia, Gutierrezia microcephala, Hymenoclea salsola, Krascheninnikovia lanata, Sphaeralcea ambigua, and/or Yucca baccata. If present, the herbaceous layer is usually open to intermittent and is dominated by perennial grasses, such as Achnatherum speciosum, Pleuraphis jamesii (above 1400 m), Pleuraphis rigida, or Poa secunda, and seasonal annuals. Other graminoid species may include Achnatherum hymenoides or Muhlenbergia porteri. Forb cover is mostly from seasonal annuals (Thomas et al. 2004).

Dynamics:  Natural fire regimes may have been altered because of grazing by livestock and fire suppression over the last 100 years, causing a reduction in fire frequency. This may allow the presence of relatively fire-intolerant species such as Artemisia tridentata, Coleogyne ramosissima, or Larrea tridentata in stands of this alliance (Keeler-Wolf and Thomas 2000).
Environmental Description:  This Mojave Desert alliance is found on alluvial fans, gentle to moderate alluvial fans, slopes and ridgetops. Stands occurs at mid-elevations ranging from 750 to 2150 m (Sawyer et al. 2009). Climate is semi-arid. Annual precipitation varies from 4 to 20 cm, and summer droughts are typical. Soil types and elevation limit the distribution of the vegetation. Soils are derived from colluvial or alluvial deposits and have variable textures, ranging from gravel, coarse sand or loamy, to fine silt. Some stands have bimodal soils with both coarse- and fine-textured layers (Keeler-Wolf and Thomas 2000).
Geographic Range: This alliance is generally limited to the Mojave Desert, but may extend into the transition zone with the southern Great Basin.

Nations: US

States/Provinces:  AZ, CA, NV, UT?


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNR

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.a Joshua Tree - Eastern Mojave Buckwheat - Rough Joint-fir Mixed Desert Scrub Group G296 3.B.1.Ne.1.a
Alliance A3148 Joshua Tree Wooded Scrub Alliance A3148 3.B.1.Ne.1.a
Association CEGL002725 Joshua Tree / Big Galleta Wooded Grassland CEGL002725 3.B.1.Ne.1.a
Association CEGL002744 Joshua Tree - Utah Juniper / Big Sagebrush Wooded Shrubland CEGL002744 3.B.1.Ne.1.a
Association CEGL003116 Joshua Tree Wooded Shrubland CEGL003116 3.B.1.Ne.1.a
Association CEGL005294 Joshua Tree / Blackbrush Wooded Shrubland CEGL005294 3.B.1.Ne.1.a
Association CEGL005776 Joshua Tree / (Desert Almond, Mexican Bladdersage) Wooded Shrubland CEGL005776 3.B.1.Ne.1.a
Association CEGL005777 Joshua Tree / Creosotebush - Mojave Yucca / Big Galleta Wooded Shrubland CEGL005777 3.B.1.Ne.1.a
Association CEGL005778 Joshua Tree / Water Jacket - Nevada Joint-fir Wooded Shrubland CEGL005778 3.B.1.Ne.1.a
Association CEGL005779 Joshua Tree / Buckhorn Cholla Wooded Shrubland CEGL005779 3.B.1.Ne.1.a
Concept Lineage: A.884, in part

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Yucca brevifolia (Joshua tree woodland) Alliance (Sawyer et al. 2009) [33.170.00]
= Yucca brevifolia Wooded Shrubland Alliance (Evens et al. 2014)
= Yucca brevifolia Woodland Alliance (Evens et al. 2012)
= Yucca brevifolia Woodland Alliance (Thomas et al. 2004)
= Yucca brevifolia Woodland Alliance (CNPS 2017) [33.170.00]
>< Joshua Tree Series: PSW-45 Type (Paysen et al. 1980)
>< Joshua Tree Woodland (Cheatham and Haller 1975)
>< Joshua Tree Woodland (#73000) (Holland 1986b)
= Joshua tree series (Sawyer and Keeler-Wolf 1995)
>< Mojave Mixed Steppe (#34220) (Holland 1986b)
>< Mojave Mixed Woody Scrub (#34210) (Holland 1986b)
Concept Author(s): K.A. Thomas et al. (2004)

Author of Description: K.A. Schulz

Acknowledgements: We have incorporated significant descriptive information previously compiled by M. Schindel.

Version Date: 04-24-18
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