1. Introduction to desert environments
Arid desert land occupies as much as 33% of the global terrestrial surface, much of which surrounds the equator. The Sahara desert alone occupies the same square acreage as the United States. Arid climates are defined by the significant absence of rainfall. Within this climate zone are three generally accepted subcategories: hyper-arid regions, which receive less than 100 mm annual rainfall, arid regions, which receive 100e300 mm annual rainfall and subarid
regions, which can receive up to 800 mm annual rainfall. Of these three subcategories, arid is the most common, occupying 14.6% of the world’s land area (FOA Forest, 1989). While rainfall averages are useful in generalizing the arid climate, there are also vast exceptions in drought/rainfall cycles. The Atacama Desert in Chile suffered a 400-year drought, interrupted
in 1971 by a torrential downpour. The Atacama, one of the driest deserts in the world, is considered the physiological dryness limit for life (Davila et al., 2008). What little precipitation does occur in such harsh environments is not always available to the species. After dusk, near or below freezing temperatures can freeze and lyse plant cells. Hot deserts typically experience diel temperature ranges from 0 C to 37 C, while cold deserts such as those in Greenland, can fluctuate from as little as 0 C to 4 C. The Hopq Desert in China experiences minimum temperatures below 30 C and high temperatures above 40 C (Wang et al., 2013).