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G293 Carnegiea gigantea - Parkinsonia microphylla - Ambrosia deltoidea Mixed Cacti Desert Scrub Group

Type Concept Sentence: This Sonoran Desert group 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, summer-deciduous tall shrub Parkinsonia microphylla and evergreen Larrea tridentata, with Prosopis sp., Olneya tesota, and Fouquieria splendens less prominent. It occurs on hillsides, mesas and upper bajadas in southern Arizona and extreme southeastern California.

Common (Translated Scientific) Name: Saguaro - Yellow Paloverde - Triangle Bur-ragweed Mixed Cacti Desert Scrub Group

Colloquial Name: Sonoran Paloverde - Mixed Cacti Desert Scrub

Hierarchy Level:  Group

Type Concept: This group 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, summer deciduous tall shrub Parkinsonia microphylla and evergreen Larrea tridentata, with Prosopis sp., Olneya tesota, and Fouquieria splendens less prominent. Other common shrubs and dwarf-shrubs include Acacia greggii, Ambrosia deltoidea, Ambrosia dumosa (in drier sites), Calliandra eriophylla, Jatropha cardiophylla, Krameria erecta, Lycium spp., Menodora scabra, Simmondsia chinensis, and many cacti, including Ferocactus spp., Echinocereus spp., and Opuntia spp. (both cholla and prickly-pear). The sparse herbaceous layer is composed of perennial grasses and forbs with annuals seasonally present and occasionally abundant. On slopes, plants are often distributed in patches around rock outcrops where suitable habitat is present. Outliers of this succulent-dominated group occur as "Cholla Gardens" in the southern and eastern Mojave Desert in California. In this area, the group is characterized by Cylindropuntia bigelovii, Fouquieria splendens, and other succulents, but it lacks Carnegiea gigantea and Parkinsonia microphylla, which are typical farther east.

Diagnostic Characteristics: This tropical/subtropical vegetation group is characterized by a number of species representing Shreve''s "Arizona Upland." Carnegiea gigantea, Olneya tesota, Cylindropuntia bigelovii, Parkinsonia microphylla, and Ambrosia deltoidea are diagnostic of this vegetation group, although, with the exception of Parkinsonia microphylla and Ambrosia deltoidea, generally do not typically dominate the shrub layer. Species sensitive to frost such as Ferocactus spp. and many other cacti are typically present and characterize this tropical/subtropical group. Larrea tridentata is generally present to dominant, but is nearly ubiquitous in the warm southwestern deserts. Common desert shrubs Prosopis spp. and Fouquieria splendens are characteristic, but also occur widely across the southwestern warm desert in other groups.

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 vegetation group is characterized by an open to moderately dense tropical/subtropical, xeromorphic evergreen and deciduous shrub layer with mixed cacti present to dominant, and sometimes with emergent tree cacti. The herbaceous layer is usually sparse.

Floristics: This wooded shrubland group includes the iconic saguaro cacti "forests" of the Sonoran Desert that are characterized by a diagnostic, emergent tree layer of Carnegiea gigantea (3-16 m tall) with sparse to moderately dense, xeromorphic, deciduous and evergreen shrub layers dominated by Parkinsonia microphylla or Larrea tridentata. Often Prosopis sp., Olneya tesota, and Fouquieria splendens are present, although usually less prominently. There are typically many cacti present, including species of Echinocereus, Escobaria, Ferocactus, Mammillaria, and Opuntia (both cholla and prickly-pear). These mixed cacti are diagnostic even when saguaro is sparse or absent. Other common shrubs and dwarf-shrubs include Acacia greggii, Ambrosia deltoidea, Ambrosia dumosa (in drier sites), Calliandra eriophylla, Jatropha cardiophylla, Krameria erecta, Lycium spp., Menodora scabra, and Simmondsia chinensis. The sparse herbaceous layer is composed of perennial grasses and forbs with annuals seasonally present and occasionally abundant. On slopes, plants are often distributed in patches around rock outcrops where suitable habitat is present. Outliers of this succulent-dominated group occur as "Cholla Gardens" in the southern Mojave Desert in California. In this area, the group is characterized by Cylindropuntia bigelovii (= Opuntia bigelovii), Fouquieria splendens, and other succulents, but it lacks the Carnegiea gigantea and Parkinsonia microphylla which are typical farther east.

Dynamics:  No Data Available
Environmental Description:  This Sonoran Desert group occurs on lower slopes of mountains, foothills, hillsides, mesas, upper bajadas, and less commonly in valleys and plains in southern Arizona and extreme southeastern California. Elevations range from 150-1070 m (Shreve and Wiggins 1964). Climate is arid. Summers are hot and winters rarely have freezing temperatures. Freezing winter temperatures limit the elevation and northern extent of these stands. The northern stands are restricted to the warmer southern and southwestern slopes; in the southern extent in Mexico, Carnegiea gigantea is restricted to northern slopes and ephemeral drainages (Benson 1982). Mean annual precipitation is 28 cm at Tucson, Arizona, but can vary greatly from year to year. Annual precipitation has bimodal distribution with about half of the rain falling during July to September and a third falling from December to March. Farther west, the proportion of summer precipitation decreases until there is not enough summer moisture to sustain Carnegiea gigantea (Barbour and Major 1977). Sites have gentle to steep slopes. Substrates are generally shallow, well-drained, gravelly, coarse-textured soils. Parent material is usually gravelly alluvium and colluvium, derived from basalt and other igneous or metamorphic rocks.
Geographic Range: This warm desert scrub group is found in southern Arizona, southeastern California and Sonora, Mexico. Outlier stands occur in the eastern Whipple Mountains of California near Parker Dam.

Nations: MX,US

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


Confidence Level: Moderate

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
Alliance A3283 Jojoba - Crucifixion-thorn - Eastern Mojave Buckwheat Desert Scrub Alliance A3283 3.A.2.Na.4.c
Concept Lineage: G294 merged into G293 (KAS 4-12-13)

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Arizona Upland: Cercidium-Opuntia region (Shreve and Wiggins 1964)
= Palo Verde - Cactus (507) (Shiflet 1994)
= Paloverde-Mixed Cacti ("Arizona Upland") Series - 154.12 (Brown et al. 1979)
> Paloverde-Mixed Cacti ("Arizona Upland") Series, Mixed scrub-Cercidium microphyllum-Olneya tesota mixed scrub Association - 154.127 (Brown et al. 1979)
> Paloverde-Mixed Cacti-Mixed Scrub on Bajadas Natural Community (Hall et al. 2001)
> Paloverde-Mixed Cacti-Mixed Scrub on Rocky Slopes Natural Community (Hall et al. 2001)
Concept Author(s): D.E. Brown, C.H. Lowe, and C.P. Pase (1979)

Author of Description: K.A. Schulz

Acknowledgements: T. Keeler-Wolf

Version Date: 11-05-15
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