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Chapter 7

Chapter 7. Desert and Tundra. DESERTS. RECEIVE LITTLE RAIN – 10-25 cm per year SOIL IS RICH IN MINERALS – but poor in organic material (nutrients) because there is NO LEACHING – rain that carries minerals deeper into the soil SOIL is loose and dry and blows away easily in the wind

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Chapter 7

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  1. Chapter 7 Desert and Tundra

  2. DESERTS • RECEIVE LITTLE RAIN – 10-25 cm per year • SOIL IS RICH IN MINERALS – but poor in organic material (nutrients) because there is NO LEACHING – rain that carries minerals deeper into the soil • SOIL is loose and dry and blows away easily in the wind • PAVEMENT – hard desert floor is exposed (hard-baked sand and rock)

  3. DESERT TYPES TWO TYPES IN NORTH AMERICA • COOL DESERTS –to the east of mountain ranges in the north western U.S. Ex: Sierra Nevada, Rocky Mountains • HOT DESERTS – in the southern U.S. (Ex: Arizona, New Mexico, western Texas, Mexico) Badlands National Park, South Dakota Anza-Borrego Desert State Park, Texas

  4. DESERT CLIMATE • Very Low Rainfall – 10-25 cm in any single year • Most deserts receive less than 10 cm • Few short thunderstorms with long dry periods • Temperature Variation – great variation due to lack of moisture in the air Ex: freezing cold at night and searing hot during the day

  5. DESERT PLANTS • Must be able to Absorb and Hold Water in thick spongy tissues (Ex: Cacti or Aloe vera which are succulents) • Adapt to Prevent Water Loss (spines on cactus are modified leaves) • Have broad shallow roots (cacti) or very deep tap roots (mesquite and Joshua tree)

  6. DESERT ANIMALS • Many types of animals: insects reptiles, birds and mammals. • Insects and reptiles have thick outer shells (scorpion, tarantula) or scales (gila monster) to protect them from the harsh climate and retain water • Mammals either stay underground during the day (kangaroo rat) or have adaptations like the long ears of the fennec which help to release heat from their bodies

  7. DESERT FORMATION • Deserts are on every continent except Antarctica • Desert belts form on either side of the equator • Sun rays heat the air at the equator causing rapid evaporation followed by repeated rainfall • The dry air that’s left after the rain moves towards the poles • This causes deserts to form

  8. DESERT FORMATION RAINSHADOW EFFECT – • In the U.S. winds move from the west coast toward the east coast • Moist air from the Pacific passes over the Sierra Nevada mountains - the cold air forces the water out and leaves cool dry air to continue towards the east. • The cool dry air takes any moisture from the soil east of the mountains and causes deserts to form

  9. DESERTIFICATION • Regions near deserts that are not as dry are called SEMIARID (partially dry). • HUMAN ACIVITY such as overgrazing, deforestation, bad farming practices all cause vegetation loss. Climate change and drought also cause desertification. • Lack of vegetation causes soil erosion, leaving hard packed dirt and rocks exposed. • This changes weather patterns, heats the air and land and starts desert formation. • Spreading deserts are found in Africa, China, Europe (Spain), South America, the Caribbean and the U.S. Results in between 6 and 12 million square kilometers of soil loss.

  10. TUNDRA • COLD, WINDY DRY REGION • LOCATED JUST BELOW THE NORTH POLE • ALASKA, CANADA, GREENLAND, ICELAND, NORWAY, SIBERIA, ASIA • LARGEST BIOME IN AREA – 10% OF THE EARTH’S SURFACE • LIMITED BIODIVERSITY – FRAGILE AND UNSTABLE ECOSYSTEM

  11. TUNDRA FACTS • Less than 25 cm precipitation (mostly snow and ice) per year • Air temperature rarely rises above 10oC (50o F) which is the limiting factor for this biome • PERMAFROST – only the top layer (~ 8 cm) of soil ever defrosts - the rest stays frozen • Rainfall can’t soak into the ground forms marshes and bogs instead • Plants stay low to the ground and do not recover quickly

  12. TUNDRA PLANTS • Short growing season (60 days) • Mosses, lichens, low shrubs and grasses – few trees (willows and birch) are very small • Roots are shallow, because of PERMAFROST • Have to be able to survive long cold winters with no light for 6 months

  13. TUNDRA ANIMALS • Many tundra animals migrate (long-distance seasonal travel) with the weather and the food sources like migrating birds. • Arctic hare, lemmings, ground squirrel, caribou, musk oxen, puffin, snow goose, arctic loon • Few predators: Arctic fox, polar bears, snowy owl, wolverines, wolves,

  14. CHAPTER 7 VOCABULARY • LEACHING • PAVEMENT • SUCCULENT • NOCTURNAL • RAINSHADOW EFFECT • DESERTIFICATION • PREMAFROST • MIGRATION • CLIMATOGRAM

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