Cold Desert

Percipitation in winter/spring predominantly as snow (60%)

winter low -8C (17F) to 30C (86F)

Elevation & Area of the Great Basin Desert

>1200 m

550,000 km² - largest NA desert

Geographical Features of the Great Basin Desert

Internal drainage - development of playas (high in salt and minerals)

Ancient Lakes: Lake Bonneville (Utah area, no water present - Bonneville Salt Flats) & Lake Lahontan (Western Nevada, water still present)

Subregions of the Great Basin Desert

1. Sagebrush Steppe - dominant species sagebrush>grasses>>saltbrush; greater diversity, marginal zone between arid and semi-arid
2. Great Basin Sagebrush Zone - dominant species sagebrush>>>grasses=saltbush; low diversity and productivity - homogenous habitat, more arid, MOST COMMON ZONE
3. Salt Desert Scrub - dominant species saltbush>>sagebrush=grasses; usually saline, presence of halophytes (Chenopodiaceae family)

Sonoran Warm Desert

Bimodal rainfall (winter 30-60% and summer 40-70%)

Winter low 1-9C (34-48)

Summer high 35-41C (95-106)

-warmest desert based on average yearly temperatures

Mild Desert - generally more humid, shorter drought periods, longer growing seasons, no freezing temps

Elevation and Area of the Sonoran Desert

>600 m

area: 256,000 km² third largest desert

Geographical Features of the Sonoran Desert

Large latitude gradient: 23-35N

Extreme habitat diversity: mountain ranges, internal and external drainage, valleys, internal and coastal regions, sand dunes, lava flows, alluvial fans and bajadas

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Subregions of the Sonoran Desert

1. Lower Colorado Valley/River
2. Arizona Uplands
3. Central Gulf Coast
4. Vizcaino Region
5. Magdalena Region
6. Plain of Sonora
7. Sonoran Foothill (not truly considered a desert)

Lower Colorado Valley/River

hottest, most arid region

surrounded by mountains - rainshadow desert

interior drainage - alluvial fans and bajadas

Dominant species Ambrosia and Larrea - presence of winter/spring annuals; few trees no columnar cacti

Arizona Upland

Higher elevation - cooler, wetter

High diversity - Parkinsonia florida & Opuntia (highly diverse); winter and summer annuals; columnar cacti

Central Gulf Coast

Coastal Desert - very dry with absorption through fog and aerial deposition

Many odd/unique life forms - "fat" tree desert (stem succulent) w/few shrubs

Dominant species: Bursera (Elephant tree) & Jatropha (Lomboy tree)

Vizcaino Region

Coastal Desert - arid; water deposits via marine air/fog (dry and salty)

Dominant species - Ambrosia and agave (leaf succulents)

Presence of epiphytes (surface growing species) - Tillandsia (Ball moss)

Magdalena Region

Coastal Desert - water absorption via marine air/fog

Dominant Species - Lysiloma (Palo Blanco) & Stenocerus

-more cactus less agave

Plains of Sonora

Interior Region (on mainland)

Many Fabaceae trees

Dominant species Olneya (ironwood) & Encilia (brittlebush)

Chihuahuan Warm Desert

Summer precipitation

Winter low: -1 to 8C (30-46F)

Summer high: 35-40C (95-105F)

droughts are generally mild - summer rainfall & cold winter prevents dessication

Elevation and Area of the Chihuahuan Desert

 Elevation: 1000-1300 m

Area: 500,000 km² second largest NA desert

Geographical Features of the Chihuahuan Desert

Large Latitude gradient: from tropics to temperate

Lays between two mountian ranges: rainshadow desert, interior desert, and tradewind desert

-internal and external drainage

Presence of alluvial fans and bajadas

Calcareous soil: Gypsum & Limestone from ancient bedrock - favors grasses, yucca, agave and cacti

Subregions of Chihuahuan Desert

1. Lower Bajada - dominant species Larrea & Flourensia cernua (restricted to Chihuahuan Desert)
2. Mid Bajada - dominant species Yucca & Agave lecheguilla (indicator species of Chihuahuan Desert)
3. Upper Bajada - rocky, higher elevations; dominant species Yucca & Agave (Fouquieria splendens)
4. Upper-Most Bajada - Highest diversity of Yucca and Agave (Nolina texana)

Mojave Warm Desert

Precipitation: winter/spring

Winter lows: 2-6C (36-43F)

Summer highs: 41-46 (106-115F)

Windy

Elevation and Area of the Mojave Desert

Elevation 600m-1200m

Area: 141,000 km²

-smallest desert

Geographical Features of the Mojave

Transitional Desert within the borders of the Great Basin Seciton and Sonoran Section

Internal (Mojave River & Amargosa River) and External Drainage (Colorado River)

No Subregions of Mojave Desert

-dominant species of the Mojave

High diversity of annual plants

Trees in riparian areas

Joshua Tree (Yucca brevifolia) - Endemic to Mojave, found at higher elevation (900-1280m)

Dominat species Larrea and Ambrosia