Images © by James L. Reveal, Norton-Brown Herbarium, University of Maryland, unless otherwise credited.

BSCI 124 Lecture Notes

Department of Plant Biology, University of Maryland

LECTURE 35 - BIOMES, Part 6 - Deserts
A. Cold Desert: Intermountain West

Sagebush, pinyon-juniper cold desert at Kodachrome Flat, Utah

XIIIa. Intermountain West

A. Location: In North America, the cold desert bounded by the Sierra Nevada on the west and Colorado Rockies on the east, and by the Idaho batholith of central Idaho on the north and generally a vegetational line defined by creosote bush (Larrea divaricata) - a warm desert species - and Great Basin sagebrush (Artemisia tridentata) in the south. Divided into two sections: Great Basin (west) and the Canyonlands (east).
B. Features:
- 1. Precipitation falls primarily as winter snow. Summer showers can be heavy and cause local "flash floods" in many areas.
  2. Temperature cool (rarely below -15° F) in winter and warm in summer (rarely above 100° F).
  3. Soils variable, sandy to rocky, mostly volcanic or limestone in Great Basin, mostly sandstone in Canyonlands.
  4. Valley bottoms mostly above 4000 ft (1220 m).
  5. Numerous, isolated mountain ranges (Great Basin) or volcanic peaks (Canyonlands), many more than 10,000 ft (3000 m).
  6. Vistas are dynamic and variable, even spectacular in places. Home to numerous national parks and monuments. Here is a listing just for Utah.
  7. Fire is only moderately significant; does aid in the re-establishment of grasses.
Sagebrush valley below 12,000 foot peaks of Snake Mountains, Nevada

C. Vegetation:
- 1. Sagebrush the dominate shrub; trees: pinyon (Pinus monophylla [Great Basin] or P. edulis [Canyonlands]) and juniper (Juniperus osteosperma) dominant.
  2. Saltbush (Atriplex) where alkaline and generally dry; pickleweed (Salicornia) and greasewood (Sarcobatus) where moist and alkaline are dominant shrubs.
  3. Mountain slopes with pine, spruce (Picea), fir (Abies) and aspen (Populus tremuloides) and many genera and species of often large shrubs (e.g., mountain mahogany [Cercocarpus]).
  4. Grasses more common in Canyonlands than Great Basin.
  5. Even the seemingly dirt can be a living creature! Learn about crytogamic soil in Capital Reef National Park.
Lower slopes of Pine Creek Canyon of the Toquima Range, Nevada

Upper slopes of Pine Creek Canyon of the Toquima Range, Nevada

D. Animals:
- 1. Deer, mountain lion, some bear, bobcat, coyote, fox and the jackrabbit.
  2. Raptors include eagles, hawks and falcons. Many resident birds.
E. History:
- 1. Great Basin:
  - a. Great Basin (proper) is a hydrographic basin; water does not flow to the sea. Great pluvial lakes formed during Pleistocene Ice Age leaving well-defined shores benches (see right). The Great Salt Lake is all that remains of Lake Bonneville whose depths reached over 1000 feet, and Lake Lahontan which persists as Pyramid Lake today.
    b. Vegetation of Great Basin elevationally pushed downward and pinched between ice and water of lakes; escaped south onto what is now Mojave Desert.
    c. Glacial ice restricted to tops of mountain ranges and canyon bottoms leaving numerous nunataks.
    d. Numerous endemics; several established over last 10,000 years ago in places once covered by lake water.
    e. Many animals went extinct in the area at the start of the Holocene.
  Rim of Canyonlands overlooking the Colorado River
  
  2. Canyonlands:
  - a. Area drained by Green and Colorado rivers. Glaciers in adjacent montane forest areas of the Rocky Mountains (Colorado Rockies, Uinta Mountains, Wasatch Range); water erosions resulted in deep, spectacular canyons through ancient (to pre-Cambrium) rock.
    b. Vegetation thwarted from escaping southward by elevationally higher North Rim of the Grand Canyon; narrow escape (and invasion) route via the Colorado River.
    c. Area (see below) long a desert or near desert region (last 24 million years); today home of numerous endemic species of plants and animals.
Newspaper Rock in the Canyonlands of Utah

F. Exploitation:
- 1. Great Basin:
  - a. Widespread and intense grazing from 1870-1920 destroyed much of the palatable vegetation for sheep and cattle; invasion of poisonous plants (e.g., halogeton in the 1930s) and annual European grasses means much still unusable. Grazing can still be a problem.
    b. Mining and some "off-road-vehicle" (ORV) traffic causing problems in certain areas .
  2. Canyonlands:
  - a. Grazing and mining (especially for uranium) has destroyed some areas.
    b. Heavy recreational use (bikes, ORVs, etc.) are threatening much of the region.
    c. Mining continues as a problem.