In the Atacama Desert, one of the world's driest, some moisture is available, but it is limited to certain zones. Coastal regions below 3,280 feet (1,000 meters) receive regular fog (called camanchacas). Rainfall is so low in the Atacama Desert that even cacti (which normally store water) can hardly acquire enough water from rainfall alone, so many plants, including bromeliads, receive a portion of their water from the fog. At midelevation areas there is no regular fog; thus, there is almost no plant cover. At higher elevations, the rising air has cooled sufficiently to produce moderate amounts of rainfall, although the vegetation is still desertlike. Shrubs typically grow near streambeds, where their roots can reach a permanent source of water.
The Atacama Desert often appears barren, but when a good dose of moisture becomes available ephemerals change its appearance, seemingly overnight. Ephemerals are typically annuals that remain dormant in the dry soil as seeds. When moisture increases, they quickly germinate, grow, flower, and set seed before dry conditions prevail again. In the days and weeks following a good rain, many grasses appear and provide a backdrop for endless varieties of showy flowers, many endemic to (found only in the region of) the Atacama Desert. Among the showier flowers are species of Alstroe-meria (commonly called irises, although they are actually in the lily family) and Nolana (called pansies, although they are members of a family found only in Chile and Peru). Conditions in the Patagonian desert are less harsh. The vegetation ranges from tussock grasslands near the Andes to more of a shrub-steppe community farther east. Needlegrass is especially abundant throughout Patagonia, and cacti are a common sight. In the shrub-steppe community in the eastern Patagonian desert, the shrubs quilembai and the cushionlike colapiche are common. Where the soil is salty, saltbush and other salttolerant shrubs grow.
See also: Tropical Savanna Biome, Tropical Forest Biome, Mediterranean and Temperate Forest Biomes
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