Print Report

A3282 Carnegiea gigantea - Parkinsonia microphylla - Prosopis velutina Desert Scrub Alliance

Type Concept Sentence: This Sonoran Desert scrub occurs on hillsides, mesas and upper bajadas in southern Arizona and extreme southeastern California. The vegetation is characterized by a diagnostic sparse, emergent tree layer of Carnegiea gigantea (3-16 m tall) and/or a sparse to moderately dense canopy codominated by xeromorphic deciduous and evergreen tall shrubs Parkinsonia microphylla and Larrea tridentata, with Prosopis velutina, Olneya tesota, and Fouquieria splendens less prominent.

Common (Translated Scientific) Name: Saguaro - Yellow Paloverde - Velvet Mesquite Desert Scrub Alliance

Colloquial Name: Saguaro - Yellow Paloverde - Velvet Mesquite Desert Scrub

Hierarchy Level:  Alliance

Type Concept: This Sonoran Desert scrub is characterized by a diagnostic sparse, emergent tree layer of Carnegiea gigantea (3-16 m tall) and/or a sparse to moderately dense canopy codominated by xeromorphic deciduous and evergreen tall shrubs Parkinsonia microphylla and Larrea tridentata, with Prosopis velutina, Olneya tesota, and Fouquieria splendens (less prominent). Other common shrubs and dwarf-shrubs present include Acacia greggii, Ambrosia deltoidea, Ambrosia dumosa (in drier sites), Calliandra eriophylla, Encelia farinosa, Jatropha cardiophylla, Krameria erecta, Lycium spp., Menodora scabra, Psilostrophe cooperi, Simmondsia chinensis, Tetracoccus hallii, Zinnia grandiflora, and many cacti, including Echinocereus spp., Ferocactus spp., Cylindropuntia bigelovii, Opuntia engelmannii, and Cylindropuntia fulgida (both cholla and prickly-pear). The sparse herbaceous layer is composed of perennial grasses and forbs with annuals seasonally present and occasionally abundant. Stands occur on rocky slopes of hills, mesas, and alluvial fans. Elevation is typically below 1220 m. Sites have gentle to steep slopes. Substrates are generally coarse-textured, shallow, gravelly loams.

Diagnostic Characteristics: This Sonoran Desert scrub is characterized by deciduous and evergreen tall shrubs Parkinsonia microphylla, Olneya tesota, Prosopis velutina, with wide-ranging shrubs Fouquieria splendens and Larrea tridentata present to codominant. Also diagnostic is a sparse, emergent tree layer of Carnegiea gigantea (3-16 m tall).

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Further study is needed to review literature and document and describe other stands and classify them into new vegetation associations. Stands in California and Mexico where Carnegiea gigantea is reported to occur by Barbour and Major (1977), Benson (1982), Malusa (2003), and Sawyer et al. (2009) especially need investigation.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance includes vegetation that has a sparse but diagnostic and very conspicuous emergent giant cacti layer (5-15 m tall). The dominant vegetation is a sparse to moderately dense woody layer of extremely xeromorphic, drought-deciduous and evergreen, short and tall shrubs 0.5-5 m tall. Many of these shrubs are arborescent cacti. A sparse dwarf-shrub layer (<0.5 m) may also be present. The herbaceous layer is generally sparse with scattered perennial grasses and forbs. Annual grasses and forbs are seasonally present and occasionally abundant.

Floristics: This Sonoran Desert scrub is characterized by a diagnostic sparse, emergent tree layer of Carnegiea gigantea (3-16 m tall) and/or a sparse to moderately dense canopy codominated by xeromorphic deciduous and evergreen tall shrubs Parkinsonia microphylla and Larrea tridentata, with Prosopis velutina, Olneya tesota, and Fouquieria splendens (less prominent). Other common shrubs and dwarf-shrubs present include Acacia greggii, Ambrosia deltoidea, Ambrosia dumosa (in drier sites), Calliandra eriophylla, Encelia farinosa, Jatropha cardiophylla, Krameria erecta, Lycium spp., Menodora scabra, Psilostrophe cooperi, Simmondsia chinensis, Tetracoccus hallii, Zinnia grandiflora, and many cacti, including Echinocereus engelmannii, Echinocereus spp., Ferocactus spp., Cylindropuntia bigelovii (= Opuntia bigelovii), Opuntia engelmannii, Cylindropuntia fulgida (= Opuntia fulgida), Cylindropuntia leptocaulis (= Opuntia leptocaulis), and Cylindropuntia spinosior (= Opuntia spinosior) (both cholla and prickly-pear). The very sparse herbaceous layer is dominated by perennial grasses and forbs with annuals seasonally present and occasionally abundant. Grass species include Bouteloua eriopoda, Dasyochloa pulchella (= Erioneuron pulchellum), Muhlenbergia porteri, Pleuraphis mutica (= Hilaria mutica), and Setaria macrostachya. Forb species include Allionia incarnata, Justicia longii (= Siphonoglossa longiflora), and Sphaeralcea ambigua. Ferguson (1950) described stands in this shrubland alliance with a mean of 20% total vegetation cover.

Dynamics:  Ecological factors determining the occurrence of Carnegiea gigantea are complex. Major limiting factors are cold winters and dry summers. According to Benson (1982) Carnegiea gigantea is killed by extended frosts and does not occur above 1370 m. Furthermore, because its seeds only germinate, and seedlings and adults mostly grow during the summer monsoon season, the lack of summer moisture restricts it from the Mojave Desert. Benson (1982) also states that moisture and shade are vital to seed germination and seedling establishment. In Arizona, north slopes are generally too cold for Carnegiea gigantea to germinate. Therefore, the best sites are mesic microsites on warm exposures where there is shade and a slight depression to concentrate precipitation. This shade may be in the form of rocks or shrubs called "nurse" plants which protect the seedlings from drying out in the sun, and possibly from frost and predation (Benson 1982, Brown 1982a). As it grows, Carnegiea gigantea may interfere with the "nurse" plant and cause dieback in the stems of shrubs such as Parkinsonia or possibly damage itself (Brown 1982).
Environmental Description:  This desert scrub occurs in the Sonoran Desert on rocky slopes of hills, mesas, and alluvial fans. In the Colorado Desert it is restricted to hillsides and upper bajadas sites in southwestern Arizona and extreme southeastern California. Plants are often distributed in patches around rock outcrops where suitable habitat is present. Elevation is typically below 1220 m. Climate is arid. Summers are hot and winters rarely have freezing temperatures. Freezing winter temperatures limit the elevation and northern extent of these stands. These northern stands are restricted to warmer southern and southwestern slopes. In the southern extent in Mexico, Carnegiea gigantea is restricted to north slopes (Benson 1982). Mean annual precipitation is 28 cm, but can vary greatly from year to year. Annual precipitation has a bimodal distribution. At Tucson, Arizona, one-half of the annual rain falls between July and September and one-third falls from December to March. Further west the proportion of summer precipitation decreases (Barbour and Major 1977). This precipitation boundary is roughly the Colorado River with the exceptions of the eastern slopes of the Whipple Mountains which receive enough rain during the summer monsoons for Carnegiea gigantea to occur. In the more arid portions of its range, such as lower elevation sites in the Lower Colorado Valley, Carnegiea gigantea is restricted along stream channels where there is additional soil moisture from runoff from higher ground (Brown et al. 1979). Sites have gentle to steep slopes. Parent material is usually gravelly alluvium and colluvium, derived from basalt and other igneous or metamorphic rocks. Substrates are generally coarse-textured, shallow, gravelly loams. Caliche is often present on the soil surface and the undersides of rocks. Adjacent stands are a matrix of Sonoran Desert shrublands typically dominated by Larrea tridentata or Ambrosia spp. or riparian shrubland codominated by Prosopis velutina, Parkinsonia microphylla, or Olneya tesota.
Geographic Range: Shrublands included in this alliance occur in the Sonoran Desert in southern Arizona, in the Whipple Mountains in southeastern California, and in adjacent Sonora and Baja California, Mexico.

Nations: MX,US

States/Provinces:  AZ, CA, MXBCN, MXSON, NV


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.A Warm Desert & Semi-Desert Woodland, Scrub & Grassland Subclass S06 3.A
Formation 3.A.2 Warm Desert & Semi-Desert Scrub & Grassland Formation F015 3.A.2
Division 3.A.2.Na North American Warm Desert Scrub & Grassland Division D039 3.A.2.Na
Macrogroup 3.A.2.Na.4 Saguaro - Organ Pipe Cactus - Burrobush Mojave-Sonoran Semi-Desert Scrub Macrogroup M088 3.A.2.Na.4
Group 3.A.2.Na.4.c Saguaro - Yellow Paloverde - Triangle Bur-ragweed Mixed Cacti Desert Scrub Group G293 3.A.2.Na.4.c
Alliance A3282 Saguaro - Yellow Paloverde - Velvet Mesquite Desert Scrub Alliance A3282 3.A.2.Na.4.c
Association CEGL001340 Catclaw Acacia - Yellow Paloverde Shrubland CEGL001340 3.A.2.Na.4.c
Association CEGL001375 Yellow Paloverde - Creosotebush Shrubland CEGL001375 3.A.2.Na.4.c
Association CEGL001389 Saguaro / Velvet Mesquite Wooded Shrubland CEGL001389 3.A.2.Na.4.c
Concept Lineage: This alliance includes old alliances III.A.5.N.e. Carnegiea gigantea Wooded Shrubland Alliance (A.885); III.A.5.N.a.; III.A.5.N.c. Parkinsonia microphylla Shrubland Alliance (A.883); and III.B.3.N.a. Acacia greggii Shrubland Alliance (A.1036), in part

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Ambrosia deltoidea-Carnegia gigantea-mixed scrub Association (154.122) (Brown 1982a) [included in Sonoran Desertscrub, Paloverde-Mixed Cacti ("Arizona Upland") Series.]
> Parkinsonia microphylla (Foothill palo verde desert scrub) Alliance (Sawyer et al. 2009) [33.150.00]
> Parkinsonia microphylla Shrubland Alliance (Evens et al. 2014)
> Simmondsia chinensis (Jojoba scrub) Provisional Alliance (Sawyer et al. 2009) [33.005.00]
= Simmondsia chinensis-mixed scrub Association (154.123) (Brown et al. 1979) [within the Paloverde-Mixed Cacti ("Arizona Upland") Series.]
> Arizona Woodland (#75400) (Holland 1986b) [included in the Sonoran thorn woodlands. This alliance lacks Carnegiea gigantea.]
= Creosote-Crucifixion-thorn Series (Brown 1982a) [from central Arizona.]
= Foothill Palo Verde-Saguaro Series (Sawyer and Keeler-Wolf 1995)
= Jojoba-Mixed Scrub Series (Brown 1982a) [from central Arizona.]
= Sonoran Desert scrub (Warren and Treadwell 1980) [Jojoba - False Mesquite - Prickly Pear Association]
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz

Acknowledgements: No Data Available

Version Date: 12-18-14
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