1. The Tropical Desert Biome

2. Characteristics of a Tropical Desert The tropical desert is an environment of extremes: very hot and very cold. The latitude and longitude of the desert is 27.7° N, 8.1°W Deserts cover 33% of the earth’s surface. Desert Locations: Coastal Chile and Peru Southern Argentina Southwest Africa North Africa Arabia and Iran Pakistan and Western India Baja California and interior Mexico

3. Why is this area called the “Tropical Desert”? The tropical desert has the highest percentage of sunshine of any climate and the highest daytime temperature of any climate. The mean annual temperature is 64.4°F. This atmosphere allows for little rainfall and in some years, none at all. The location of the tropical desert severely inhibits the chance of precipitation. The descending air of the subtropics warms and dries out the air not allowing for condensation to occur. In turn, the desert receives little precipitation annually. The tropical desert is also linked with the rain shadow that does not allow for much rain to reach the desert areas.

4. Animal Life and Plant Life Animal Life: Nocturnal carnivores Burrowers Kangaroo rats Insects Reptiles Birds Plant Life: Ground-hugging shrubs Short woody trees Cactus

5. Climate The Tropical Desert has an “arid” (severe lack of water) climate. The annual precipitation is less than half the annual potential evapotranspiration (the sum of evaporation and plant transpiration from the earth’s land surface to the atmosphere) Precipitation: irregular and unreliable Average Rainfall: 25 centimeters annually In many deserts, the rain for one year falls in one downfall. The desert is too far from a source of water to receive significant rainfall. The relative humidity can drop to 10% or less which causes evaporation. Temperature: highest mean annual temperature of any climate Average Temperature: 90°F (the average temperature does not reach below 64.4°F during any month of the year) High temperatures are a result of the high sun angles and the high percentage of sunshine of any climate. The tropical desert is primarily cloud-free. This causes a large loss of heat at night and gain of heat quickly during the day.

6. Biomass and Productivity What is Biomass? The total dry weight of all organic matter in plants and animals in an ecosystem. What is Productivity? The rate at which radiant energy is used by producers to form organic substances as food for consumers. Of all of the biomes, the desert biome is the least productive. The desert’s net productivity is less than 200 kilocalories per square meter every year compared to 9000 kilocalories per square meter in other biomes like the tropical rain forest. In relation to the productivity, the desert has a low biomass. Because of the scarcity of water, the desert has a lack of biodiversity resulting in low biomass.

7. Threats to the Biome Developments by humans like cities (Phoenix, Tuscon, Las Vegas) cause severe threats to the stability of the desert biome. High levels of grazing can destroy or alter native plant communities, and the grazing animals can trample and kill a variety of desert plants and animals. Irrigation also poses a threat to the water supply that the desert has. If water is not supplied in enough abundance to flow off the land and carry away salts then those salts will build up, leading to salinization of soil. Salt levels may become too high to support plants. Off-road vehicle use may kill or crush pants while driving or disrupt soil leading to wind erosion. Global warming affects the temperature of the already hot desert. But, this slight change in temperature can alter the precipitation of the desert.

8. Animals and Adaptation Desert Spiny Lizard: This lizard is has large, pointed, keeled, and overlapping scales Adaptations: The desert spiny lizard is well camouflaged to sneak up on prey. The lizard also primarily lives in shaded areas and hibernates in the winter to avoid hot conditions in the desert. Male desert spiny lizards are able to puff up and arc their backs to avoid predators. Also, their tails regrow when they are injured.

9. Plants and Adaptation Prickly Pear: The prickly pear is a cactus that has flat pads and cylindrical segments that are lightly spined. Adaptations: The prickly pear developed defense structures by reducing leaves to take on the form of spines. The coating of the plant with a thick waxy cuticle reduces water loss in the desert. The water storage in the stem is also a critical adaptation for survival in the heat. Plants must adapt to the desert climate that provides little water for survival.

10. The Cold Desert Biome

11. Characteristics of a Cold Desert The cold desert is characterized as a desert because of the extreme poverty of life. The cold desert is an environment of extremes just like the tropical deserts except that the cold desert receives snowfall rather than rainfall. The latitude and latitude of the cold deserts range from 15° S to 60° S and 70° W to 80° W. The majority of the snowfall occurs in the winter and occasionally in the short summers. The cold deserts cover 5 million square kilometers of land on earth. Locations: Antarctica Central Asia Greenland * Antarctica is the world’s largest desert

12. Climate Like the tropical desert, the cold desert experiences a high percentage of sun and strong winds throughout the year. But, the cold desert has continuous permafrost that makes it inhospitable for a lot of wildlife. The dry air of the cold deserts does not hold much water vapor and makes rainfall almost impossible. Scientists have determined that some cold deserts, like Antarctica, have not received rainfall in up to 4 million years. Precipitation: snow rather than rain Average Snowfall: 15-26 centimeters The heaviest snowfall is in the winter. Precipitation also occurs heavily in the spring between April and May. Occasionally, it will snow in the fall. Temperature: cold winters and moderately warm summers Average Temperatures: 21-26° C During the winter, the temperatures will fall below -2° C.

13. Animal Life and Plant Life Animal Life: Moose Arctic fox Pygmy armadillo Long-eared jackrabbit Polar bears Plant Life: Grasses Mosses Flowers

14. Biomass and Productivity The cold desert is slightly more productive than the tropical desert because of the snow that moistens the soil and provides a source of water. The cold desert has a net primary productivity of 600 kilocalories per square meter every year. Because of the barren nature of this biome, productivity and biodiversity are limited. Since biodiversity is limited, so is biomass. The cold desert is also the lowest of the biomes based on biomass.

15. Threats to the Biome One of the major threats to the cold desert biome is the elevation of airborne pollutants such as DDT and PCB’s. The human threat of gas and oil development also threatens the cold desert biome. For many years, humans have been pushing to use the polars as sources of oil, but, so far, it has been untouched. The cold desert is also threatened by global warming. As the earth heats, the permafrost melts and the ecosystem therefore collapses. * The permafrost also contains significant amounts of dead plant material. The more that the permafrost melts, the more decay that occurs. This then releases even more CO2 into the atmosphere.

16. Animals and Adaptation Polar Bear: The polar bears live much of their life on the sea ice of the cold deserts. Adaptations: The polar bear’s white coat is filled with water repellant hairs and a dense undercoat that covers their feet. Polar bears have short, thickly covered snouts and ears that retain heat from their environment. Polar bears also have extremely sensitive noses that can sense things up to 20 miles away and 1 foot underneath the ice.

17. Plants and Adaptation Saxifrage: Saxifrage is a small plant that develops leaves close to the ground and typically inhabit the arctic environment. Adaptations: Saxifrage thrives in the desert biome by growing roots deep into the soil where the heat from the summertime can be absorbed to stay alive. It is also protected in the winter by a blanket of snow that limits exposure to cold temperatures and strong winds

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