Name:
Carnegiea gigantea - Stenocereus thurberi - Ambrosia dumosa Mojave-Sonoran Semi-Desert Scrub Macrogroup
Reference:
NatureServe Biotics 2019
Description:
This broad macrogroup encompasses warm temperate to subtropical semi-desert climates of the southwestern U.S. and adjacent Sonora and central to northern Baja California, Mexico. The vegetation is diverse and is characterized by a sparse to moderately dense layer (1-50% cover) of xeromorphic, evergreen or drought-deciduous, microphyllous or broad-leaved shrubs and/or succulent species, especially cacti, rosette stem succulents such as agaves, and sarcocaulescent trees and shrubs. <i>Larrea tridentata</i> is often present to dominant with <i>Ambrosia dumosa</i> throughout much of the range of this macrogroup, and occurs on finer-textured mid to lower bajadas. On upper bajadas with coarser soils, where more moisture is available, these shrubs are mixed with increasing higher diversity of cacti and other shrubs. In areas of limited moisture, the mixed shrubs can be seen following washes or shallow braided channels across alluvial fans. Species composition changes across this vast desert area. <i>Ambrosia dumosa, Ephedra aspera, Eriogonum fasciculatum, Yucca brevifolia</i>, or <i>Yucca schidigera</i> are diagnostic in the northern most portion known as the Mojave Desert. The Arizona Upland portion of the Sonoran Desert is characterized by <i>Carnegiea gigantea</i> with shrub layers dominated by <i>Parkinsonia microphylla</i> or <i>Larrea tridentata</i>. <i>Fouquieria splendens, Olneya tesota</i>, and many cacti species are often present. The subtropical central Gulf of California coast and adjacent portions of the lower Colorado River valley region are characterized by <i>Bursera microphylla, Jatropha cuneata, Pachycereus</i> spp., and <i>Stenocereus thurberi</i>. In coastal Baja and adjacent southern California, <i>Agave shawii, Bergerocactus emoryi, Euphorbia misera, Ferocactus viridescens, Lycium californicum, Cylindropuntia californica var. parkeri, Opuntia littoralis, Cylindropuntia prolifera</i>, and <i>Yucca schidigera</i> are diagnostic and often dominant species.<br /><br />In addition, this macrogroup includes areas of sparsely to moderately vegetated warm semi-desert dunes, sandsheets, and sandy plains characterized by <i>Abronia villosa, Croton wigginsii, Dicoria canescens, Eriogonum deserticola, Helianthus niveus, Oenothera deltoides, Palafoxia</i> spp., and <i>Panicum urvilleanum</i> often with <i>Achnatherum hymenoides, Achnatherum speciosum</i>, and <i>Pleuraphis rigida</i>. Numerous other species may be present in this diverse macrogroup. In the Arizona Upland of the Sonoran Desert, stands occur on the lower slopes of mountains, foothills, hillsides, mesas, and upper bajadas. Stands form the vegetation matrix in broad valleys, lower bajadas, plains and low hills in the Mojave, Sonoran and Lower Colorado deserts. Stands also occur in coastal plains found on both sides of the Gulf of California and along the central Baja California coast, with a depauperate extension north along immediate coastal bluffs and xeric slopes intermittently to southern California, including the more southerly Channel Islands (San Clemente, Catalina, Santa Barbara, and Anacapa). Elevation ranges from -75 to 1800 m. Climate is semi-arid to arid and season of precipitation varies regionally. The annual precipitation in the Sonoran Desert has a 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 precipitation has a markedly unimodal distribution with most precipitation falling in the winter months associated with winter storm tracks reaching the desert from the Pacific Ocean in the Mojave Desert. In contrast, in central Baja California, climate is extremely arid with mean annual precipitation of less than 100 mm, which occurs mostly in the summer-early fall season (monsoon). Precipitation is augmented by summer fog drip near the coast. Inland Sonoran stands are also extremely arid with mean annual precipitation of less than 100 mm, which occurs mostly in the summer-early fall season (monsoon). Extended drought is common which favors plants with water storage. Substrates are variable, but typically shallow, well-drained, rocky or gravelly coarse-textured soils derived from colluvium or alluvium, except for the sand deposit sites included in the macrogroup. Parent material is usually gravelly alluvium and colluvium, derived from basalt and other igneous or metamorphic rocks.
Accession Code:
urn:lsid:vegbank.org:commConcept:40498-{390FA164-562E-45CC-9646-74F5EB34957F}
Plot-observations of this Community Concept:
0
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