6-4 Desert Biomes
What Are the Major Types of Deserts? Hot, Medium, and Cold
A desert is an area where evaporation exceeds precipitation. Annual precipitation is low and often scattered unevenly throughout the year. Deserts have sparse, widely spaced, mostly low vegetation.
The largest deserts are found in the interiors of continents, far from moist sea air and moisture-bearing winds. Other, more local deserts form on the downwind sides of mountain ranges because of the rain shadow effect
Tropical deserts are hot and dry most of the year. They have few plants and a hard, windblown surface strewn with rocks and some sand. They are the deserts we often see in movies.
In temperate deserts, daytime temperatures are high in summer and low in winter and there is more precipitation than in tropical deserts. The sparse vegetation consists mostly of widely dispersed, drought-resistant shrubs and cacti or other succulents adapted to the lack of water and temperature variations.
In cold deserts, winters are very cold, summers are warmer, and precipitation is low. The polar deserts of Canada and other northern nations are characterized by receiving less than 250 millimetres (10 inches) of precipitation per year, and the mean temperature of the warmest month is less than 10°C.
In the semiarid zones between deserts and grass- lands, we find semidesert. This biome is dominated by thorn trees and shrubs adapted to long dry spells followed by brief, sometimes heavy rains.
How Do Desert Plants and Animals Survive? Get Water Any Way You Can
Adaptations for survival in hot deserts have two themes. One is beat the heat and the other is every drop of water counts.Succulent plants, such as the saguaro cactus, have three adaptations. They have no leaves, which can lose water by evapotranspiration. They store water and synthesize food in their expandable, fleshy tissue. And they reduce water loss by opening their pores to take up carbon dioxide only at night.
Evergreen plants conserve water by having wax- coated leaves that minimize evapotranspiration. Others, such as annual wildflowers and grasses, store much of their biomass in seeds that remain inactive, sometimes for years, until they receive enough water to germinate.
Most animals of hot deserts are small. Some beat the heat by hiding in cool burrows or rocky crevices by day and coming out at night or in the early morning. Others become dormant during periods of extreme heat or drought.
Adaptations for survival in a polar desert revolve around combating the effects of cold and dryness. Plants are extremely low to take advantage of warmth at the surface of the ground, and to avoid the drying effect of wind.