Chapter 7Desert 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

PAVEMENT – hard desert floor is exposed (hard-baked sand and rock)

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)

Anza-Borrego Desert State Park, Texas

Badlands National Park, South Dakota

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

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)

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

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

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

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.

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

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

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

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,

CHAPTER 7 VOCABULARY

LEACHING

PAVEMENT

SUCCULENT

NOCTURNAL

RAINSHADOW EFFECT

DESERTIFICATION

PREMAFROST

MIGRATION

CLIMATOGRAM