Sagebrush - Mountains and Plains: The Ecology of Wyoming Landscapes - page 110

Fig. 7.2. Shrublands dominated by
Wyoming big sagebrush form a mosaic
with saltbush desert shrubland in this
area west of Rawlins. Big sagebrush is
restricted to ravines, where drifting
snow accumulates and provides more
water for plant growth. the adjacent
shrubland is dominated by birdfoot
sagewort, Gardner's saltbush, western
wheatgrass, and winterfat. this area is
one of the driest in the state (see fig.
3.4). elevation 6,750 feet.

the sagebrush-dominated ecosystem is far from uni-
form. in some areas patches of sagebrush intermingle
with patches of grassland, or with patches of small
sagebrush plants intermingled with taller shrubs. this
mosaic can sometimes be attributed to fires, which burn
unevenly across the landscape, creating patches of dif-
ferent ages. the mosaic also is influenced by differences
in soils and topography. Shallow soils and windswept
ridges commonly have black sagebrush and small cush-
ion plants, whereas deeper, saline soils have birdsfoot
sage, Gardner's saltbush, and greasewood. Soils along
ephemeral creeks often support silver sagebrush. the
transitions are sometimes abrupt, due to abrupt changes
in moisture availability and soil conditions.
Many of the plants associated with sagebrush are
also found in grasslands, such as western wheatgrass,
Sandberg bluegrass, needle-and-thread grass, indian

ricegrass, pricklypear cactus, scarlet globemallow,
horsebrush, and rabbitbrush. the common animals are
often the same as well, including pronghorn, jackrabbit,
badger, coyote, Wyoming ground squirrel, grasshopper
and deer mice, several kinds of grasshoppers and spar-
rows, and many others (see table 6.1).
climate is an important factor in determining sage-
brush distribution and growth, as winter precipitation—
especially snowfall—contributes a larger proportion of
annual precipitation in the intermountain basins where
big sagebrush is common (see chapter 3). 3 in contrast,
summer rains provide most of the water on the grass-
lands of the eastern plains. Unlike rainfall in the sum-
mer, which evaporates quickly, snow is more likely to
accumulate and when it melts, the water infiltrates
to greater depths. this provides the more dependable
water supply required by big sagebrush. in the Lara-