Present-Day Environments and Climate Change - Mountains and Plains: The Ecology of Wyoming Landscapes - page 28

Sheridan

Powder River Basin

Big Horn
Basin

Cody

Gillette

Worland

Newcastle

Wind River
Basin

Casper

Lander

Great
Divide
Basin

Green
River
Basin

Rawlins

Rock
Springs

Laramie

Cheyenne

0 50 100 km

≥ 9,000 ft ≥ 7,000 ft 5,000 ft

0 50 100 miles

Fig. 3.1. General topographic map of Wyoming with the
names of selected towns and intermountain basins. elevation
is given as number of feet above sea level. See fig. 1.2 for the

names of mountain ranges and other basins. Adapted from
Martner (1986).

elevation in determining plant and animal distribution
patterns.
Based on elevation, topography, geologic charac-
teristics, and location with regard to the continental
Divide, several ecological regions can be identified. the
Great Plains characterize the eastern third of Wyoming,
with elevations ranging from 3,125 to 7,524 feet. Sum-
mer precipitation is more frequent on the plains than
farther west. Grasslands are the most common vegeta-
tion type, and there is evidence to suggest that bison
were more numerous there than in the Great Basin of
Utah and nevada. 3 With more bison, plants on the
Great Plains evolved adaptations to withstand grazing
from large herbivores; hence, they are more tolerant of
livestock grazing than are plants in the Great Basin.

to the west of the Great Plains is a region of moun-
tains and intermountain basins (see figs. 1.2 and 3.1).
the continental Divide passes through the middle
of this region, splitting west of Rawlins to form the
Great Divide Basin, which has no drainage to either
the Pacific or Atlantic oceans. the Divide around this
closed basin is relatively low, about 7,000 feet above sea
level, and is characterized by sagebrush steppe rather
than the coniferous forest or alpine tundra typical to
the north and south. For this reason, the Pony express,
various wagon trails, and the first transcontinental
railroad passed through the area in the 1800s. Most of
the basins range in elevation from about 3,960 to 7,260
feet, with the highest basins in the south (see figs. 1.1
and 3.1).