Desert Ecosystems•Desert- an arid region with little or no vegetation •Deserts in North America are located on the western side and run into Mexico.o Receive little or no water(less than 10 inches per year)o Are in a rain shadow of the mountains

There are 4 main deserts in North America:1. Great Basin Desert2. Mojave Desert3. Sonoran Desert4. Chihuahuan Desert

1. Great Basin Desert• Largest in North America (between Rocky and

Sierra Nevada Mountains)• Covers most of Nevada and parts of Utah, Oregon,

and Idaho • A cold desert because it is relatively high in altitude• Most precipitation is in the form of snow fall

– Not all of it melts into the ground because it evaporates in the spring

• Plants include:A. Sagebush- a desert bush; does not grow in salty

areas

B. Salt Bush- a desert bush; does grow in salty area

– Plant in the same family such as spinach– Salty because the H₂O evaporates and

leaves the salt behind.

•Has playas- lakes that are temporarily dry for most of the year

•Deep soil on valley floor because of years of mountain erosion

Other Plants and Animals• Plains prickly pear cactus: grows low to ground• Mormon tea• Greasewood • Blackbrush• Snakewood, ect.

Animals- eat grasses and increase amount of sagebush• Mule deer

• Pronghorn antelope

Ecological Threats• Introduction and spread of alien, invasive species• cheat-grass brome

Mojave Desert

• Covers a wide range of vegetation types.• Northern parts are like the Great Basin.• The southern parts resemble the Sonoran Desert• Contains “Death Valley”

– Very hot– 4.3cm of rain per year

Distinctive Features• Yucca- huge plant that grows to tree like proportions• Cacti- chollas & small cacti

– Has to be frost tolerant because of snowfall and ice

• 250types of spring flowers– 80% of these only grow in the Mojave

Sonoran Desert• Different types of soils because of the different types of rocks.• Succulents can survive because there is no frost.• Rain two times per year:

– Long rains in winter– Downpours in summer.

• Bajadas- slopes where mountain erosion accumulates– Soils are deep and lots of plants grow on them– The loose soil holds an abundance of water

• Washes- rivers that carry water down from the mountains– Dry for most of the year yet the soil still remains moist

Chihuahuan Desert• Over Northern Mexico and southern part of USA including west Texas and

parts of New Mexico and Arizona• At high altitude (1,000-1,500m)• Summers are hot winter are relatively cool with night frost• Rainfall is relatively high (20-30cm) – almost all in summer• Nearly 80% has calcium rich soils because of lime stone

– Indicates it was once under the ocean– Has small cacti and frost tolerate grasses

• Major Vegetation• Low Areas

– Creosote bush/ Tar bush

• Upper areas– Bajadas– Yucca (Spanish daggers – sharp leaves)

• High Areas– More bushes and small trees– H2O is more abundant in the valley floor

Highest• True trees

– Pines, oaks, junipers

• Microbes– Lichens, Fungi, Cyanobacteria

General Desert Information• Deserere comes from the word deserere( Latin for abandoned)• A desert will form if the rate of precipitation is less than the rate of

evaporation• Not all deserts are hot, there are some in the polar regions• Largest desert is the Sahara

– Size of the US and stretches across north Africa

• Most of central Australia is desert• Southern Africa has the Namib and Kalahari desert and Kalahari Bushmen• Most desert are not sandy ( rocks ,pebbles ,and gravel)• Dust Devils- Warm air rises quickly in an area and as it leaves, the other air

rushes in to fill the space and carries sand with it.

Animals of the Desert•Snakes• Rattlesnakes• Mojave rattlesnake• Lives in the Mojave Desert• Length 2-4 ft• Is considered one of the most venomous

snakes in the U.S. • Venom is neurotoxin

• Western Diamondback Rattlesnake• Range is Central/West Texas to Southern

New Mexico/California• Length 3-5ft but some can get as long as 7• Venom is hemotoxin

Animals Cont.• Lizards– Gila Monster

• Range is the southwest US and Mexico• Venom is a neurotoxin

– Venomous spit• Length

– Up to 2 ft.

• Arachnids– Scorpion

• Venom is a neurotoxin• Various species throughout the US

– Tarantula• Widespread through out the southwest US• Can get 3-4 inches in size• Can live 10 to 12 years

Hi Danny!