HotCold Deserts

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Hot/Cold Deserts
Chihuahuan Desert
Mojave Desert
Sonoran Desert
Great Basin Desert
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Hot/Cold Deserts
-contained within a geological region called the
Basin and Range Province
-based on floristic composition and distribution

-geologic history of a region, the soil and
mineral conditions
-elevation and the patterns of precipitation
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What is a Desert?
Area that receives less than 10 inches of
precipitation a year
In some deserts, the amount of evaporation is
greater than the amount of rainfall
14 of world's terrestial environment
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Sonoran Desert
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Sonoran Desert
-covering 120,000 square miles
-hottest of our North American deserts
-distinctly bimodal rainfall pattern produces a
high biological diversity
-Freezing conditions can be expected for a few
nights in winter
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Sonoran Desert
-Trees are usually well developed
-riparian woodlands composed of Fremont
Cottonwood and various willows
-understory consists of numerous layers of
smaller woody shrubs
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Saguaro Cactus (Cereus giganteus)
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Fonquieria splendens
Ocotillo
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Black-Collared Lizard
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The RoadrunnerGeococcyx californianus
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San Pedro River
most extensive, healthy riparian ecosystem
remaining in the desert Southwest
-82 species of mammals -12 species of fish -47
species of reptiles and amphibians -100 species
of breeding birds -250 species of migrant and
wintering birds
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Chihuahuan Desert
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Big Bend National Park, Texas
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Chihuahuan Desert
-the largest desert in North America covering
more than 200,000 square miles
-elevations between 3,500 and 5,000 feet
-limestone and calcareous soils are common
-less than 10 inches of rainfall yearly
-cool winter temps, very HOT summer temps
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Chihuahuan Desert
-largely known as a SHRUB desert
-Yuccas, agaves and Creosote Bushes are the
characteristics plants
-White-thorn Acacia and Ocotillo are also large
conspicuous plants
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Creosote BushLarrea tridentata
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Collared Peccary(Javelina Tayaussa Musk
Hog) Peccary angulatus
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White-Nosed Coati (Coatimundi)
Nasua narica
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Mojave Desert
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Mojave Desert
-occupies more than 25,000 square miles
-average annual precipitation of less than 5
inches
-Freezing temperatures occur in winter, while
summers are hot, dry and windy
-some do not consider the Mojave a desert
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Mojave Desert
-hosts about 200 endemic plant species found in
neither of the adjacent deserts
-trees are few, both in numbers and diversity
- Creosote Bush, Big Sagebrush, and Blackbush are
common shrubs
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Joshua Tree Yucca brevifolia
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Gila MonsterHeloderma suspectum
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Great Basin Desert
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Great Basin Desert
-covers an arid expanse of about 190,000 square
miles (largest US desert)
-more northern latitude, as well as higher
elevations (4,000 to 6,500 feet)
- 7-12 inches annually, is more evenly
distributed throughout the year
-Winter precipitation often falls as snow
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Great Basin Desert
-vegetation is low and homogeneous
-Typical shrubs are big sagebrush, blackbrush,
shadscale, Mormon-tea and greasewood
-only occasional yuccas and very few cactus
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Mormon Tea (Ephedra)
Blackbrush
Shadscale (Atriplex)
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Desert Animal Survival
-Avoiding Heat
-Dissipating Heat
-Retaining Water
-Acquiring Water
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Desert Plant Survival
-altering their physical structure xerophytes,
phreatophytes
- Reproductive adaptations annuals, perennials
-Sonoran Desert, seed densities average between
5,000 and 10,000 per square meter
-eliminating leaves -- replacing them with
thorns, greatly reducing leaf size to eliminate
transpiration (loss of water to the air), waxy
leaves, upright position
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C4 photosynthesis- stomata close during the day
to decrease water loss and prevent CO2 uptake
(uses stored CO2 in bundle sheath to carry out
photosynthesis during day)
CAM- Crassulean Acid Metabolism--organic acids
made at night (stomata are open) during the day
CO2 is released and incorporated into sugar
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Sonoran Desert--native toads and frogs
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Desert amphibians such as the Mexican spadefoot
can go from egg to tadpole to young spadefoot in
less than two weeks.
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Great Plains toads in copulation, or amplexus
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The Colorado River toad is the largest native
toad in the Western United States.
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A bullfrog munches on a bat
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Great Plains toad
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A large male bullfrog like this one can weigh
more than 400 grams