Atriplex

Chenopodiaceae

• Large desert playas tend to be defined by vegetation rings that form around their margins, with salinity as the key selecting factor. As you move along the lower bajada slopes or sandy flats approaching a playa, creosote bush typically drops out quite abruptly. This boundary for the creosote closely approximates the geologic lakebed and lies well beyond the existing playa. While residual salinity may be one factor in limiting the occurrence of creosote bush, more important is the fine texture of the lakebed soils which provides poor mixing of soil gases. Below this boundary, creosote bush is replaced by a community called saltbush scrub with a dominance of various species of saltbush. These saltbush habitats typically exhibit loamy soils with low levels o residual salinity originating from evaporation out of the geological lakebed.
• The saltbushes form the genus Atriplex in the goosefoot family or Chenopodiaceae. Some recent evolutionary studies place this family within a broader concept of the Amaranthaceae. Saltbushes as a group have a global pattern of distribution in saline coastal and interior arid habitats. While widely present in warm deserts, saltbush species attain increased importance in cold temperate desert ecosystems. Most shrubby, saltbush species are dioecious, meaning that there are separate male and female plants. Bot male and female flowers are relatively nondescript and appear during the warm late spring and summer months.
• The leaves of most woody Atriplex species exhibit morphological and physiological characteristics which are adaptive in a hot, dry environment. Steeply angled leaves reduce midday solar interception yet result in relatively high interception when solar angles are low and atmospheric humidity is relatively high. Another morphological characteristic critical to their ecological success in saline soils is the presence of specialized multicellular hairs on the leaf surfaces which limit the effects of the potentially toxic accumulation of salts in their tissues. Each of these hairs has a stalk and an inflated tip called the bladder cell. These shrubs control tissue salt levels by sequestering sodium, potassium, and chloride ions in membrane-bound vacuoles within these bladder cells. The eventual rupture of bladder cells releases these salts back into the environment. Light reflectance from the surface of bladder cells covering the leaf surface fives saltbush species their characteristic silvery color. Live a vertical leaf orientation, these silvery bladder cells reduce incident solar radiation during the summer months, increasing the efficiency of water use, and additionally limiting the absorption of potentially damaging ultraviolet light.
• Most species of saltbush utilize C₄ metabolism, one of the specialized mechanisms of carbon fixation. In these shrubs the C₄ metabolism is not utilized to produce unusually high rates photosynthesis but instead to allow the plants to use water efficiently. This metabolism allows saltbushes to extend their growth well into the summer months when other competing shrub species have lost their leaves and become dormant. Depending on conditions of soil salinity and moisture availability, there are at least seven Atriplex shrub species that attain localized dominance. Identifying these is challenging as they are all non-descript gray shrubs and lack showy flowers. "California Desert Plants, Philip W Rundel, Robert J Gustafson, Michael E Kauffmann."