Name:
Fouquieria splendens - Atriplex hymenelytra - Amaranthus watsonii North American Rock Vegetation Macrogroup
Reference:
NatureServe Biotics 2019
Description:
This macrogroup consists of near barren and sparsely vegetated landscapes on a variety of substrates across the southwestern U.S. and northern Mexico, including Baja California. It may be divided into two main groups: pavement, badlands, and outcrops or southwestern North American dunes and sandsheets. Vegetation is variable depending on environmental factors of the sites, which range from below sea level to foothill and lower montane elevations. Lower elevation sites often have herbaceous or shrub species present, whereas foothill and lower montane sites may also include scattered trees. Most of the tree species also occur in non-sparse vegetation groups. Common species of the Sonoran Desert include <i>Amaranthus watsonii, Eucnide rupestris, Ficus</i> spp., <i>Hofmeisteria</i> spp., <i>Maytenus phyllanthoides, Nicotiana obtusifolia</i>, and <i>Pleurocoronis laphamioides</i> [excluded]. In the alluvial fans and low mountains of the Mojave Desert and adjacent Sonoran Desert, differential shrubs include <i>Atriplex hymenelytra</i> and <i>Atriplex confertifolia</i> (basic to alkali substrate), <i>Nolina bigelovii, Peucephyllum schottii</i>, and <i>Pleurocoronis pluriseta</i>. Thorny and stem succulent shrubs such as <i>Echinocactus polycephalus, Fouquieria splendens, Ferocactus cylindraceus</i>, and <i>Cylindropuntia bigelovii</i> may be present. The nearly ubiquitous Mojave and Sonoran desert shrubs <i>Larrea tridentata</i> and <i>Encelia farinosa</i> are often present in rocky Mojave Desert stands, while at higher elevations in the desert mountains, <i>Eriogonum fasciculatum, Eriogonum heermannii</i>, and <i>Ericameria cuneata</i> occur. Calciphile species such as <i>Agave utahensis, Buddleja utahensis, Ephedra funerea, Petrophytum caespitosum</i>, and <i>Salvia funerea</i> occur on limestone and marble outcrops. Certain annual herbs such as <i>Perityle</i> sp. are particularly characteristic of these massive outcrops.<br /><br />Nonvascular (lichens) plants are the predominant lifeform in some desert areas of higher precipitation. Species diagnostic of desert pavements and badland clay flats or mud hills are composed primarily of ephemeral annuals, which disclose themselves only in years of favorable precipitation. Several herbaceous species such as <i>Eriogonum inflatum, Coreopsis</i> sp., and <i>Plantago ovata</i> may occur on both clay-rich flats and mud hills, or on desert pavements, while others such as <i>Chorizanthe rigida</i> and <i>Geraea canescens</i> are most characteristic of pavements (so called due to the oxidized patina which slowly accumulates on surface rocks and pebbles), which are often underlain by a cemented duripan of calcium carbonate (caliche) making them impervious to roots of larger desert shrubs. Several species of annual <i>Eriogonum</i> spp. as well as <i>Chorizanthe</i> spp. may occur on pavements in the northern Sonoran and Mojave deserts. Another suite of annual ephemeral species are diagnostic of mud hills and flats, such as <i>Coreopsis calliopsidea</i>, and <i>Eriogonum trichopes</i> (Mojave).<br /><br />Landforms include cliffs, narrow canyons, and smaller rock outcrops in desert mountains; pebbly pavement in xeric basins and alluvial fans; and upland areas around playas and washes. Sparse vegetation also occurs on special substrates such as shale or mudstone outcrops in badlands and volcanic deposits such as tuff and basal lava. Rock substrates include bedrock and unstable talus slopes in desert mountains. Some substrates, such as marine shales, are strongly alkaline and/or saline, which chemically limits plant growth. Active substrates such as scree slopes are difficult sites for plants to grow. Physical properties of substrates may also limit plant growth. Badland sites often have heavy clay soils that reduce water infiltration or availability (colloidal binding), increasing erosion rates and reducing soil moisture for plants.
Accession Code:
urn:lsid:vegbank.org:commConcept:40514-{05F9FF29-FFC3-4BB6-A6EB-15E7E18B4F37}
Plot-observations of this Community Concept:
0
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