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Desert in Bloom
| Article
# : |
10087 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
4 / 1986 |
965 Words |
| Author
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Ronald J. Kass
Ron Kass has a M.S. in botany from Brigham Young University,
Provo, Utah, and will pursue a further degree this fall. |
Deserts are defined by geographers as lands where evaporation exceeds rainfall. No specific rainfall amounts can be used as a criterion but deserts may range from extremely arid ones, like the Sahara desert in Africa, to those with sufficient moisture like the Sonoran desert in the Southwestern United States.
Water is the lifeblood of the desert ecosystem. Rainfall is highly erratic, coming in clusters of rainy days 3 to 15 times a year and, of these, only 1 to 6 may be large enough to stimulate biological activity. Thus, the desert experiences long periods of inactivity broken by periods of short bursts of reproduction.
The great deserts of the world are primarily located in two distinct belts: one near the Tropic of Cancer and the other near the Tropic of Capricorn. Their placement at these latitudes is a result of atmospheric high pressure altering the course of rainfall. In North America, the deserts are confined to the southwestern United States. At these locations, the deserts are influenced both by climatic factors and by high mountain ranges creating rain shadows on the lee side of the mountain. The major deserts of the Southwest, the Mojave, Sonoran, and Chihuahuan, are a result of these climatic and topographic factors.
A common misconception is that deserts are arid wastelands, unobscured by vegetation and inimical to both man and beast. This myth is soon dispelled if one's visit to the desert coincides with the flowering period. Flowering occurs in two distinct periods: in the early spring after the winter rains come in from the Pacific and in the late summer after the summer rains move up from the Gulf of Mexico. If the desert enthusiast is fortunate enough to be in the desert at these times, the stoic landscape can be transformed into an abundant and prolific light show of multicolored desert annuals and a myriad of showy perennial shrubs. The desert poppy (Eschscholzia mexicana) and tackstem (Calycoseris wrightii) blanket the landscape as far as the eye can see, and the incienso (Encelia farniosa) clothe the rocky hills below the towering cactus. During this time of the year, the diversity of plant and animal life is unchallenged for its beauty. Water is the premium commodity in the desert ecosystem. The ability to withstand or circumvent the scarity of it is the selective force that gives the desert its unique appeal.
Desert plants are adapted to the scarcity of water either by drought evasion or drought resistance. Annual plants (those plants that complete their life cycle in one year) persist as seeds
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