Grasslands - Mountains and Plains: The Ecology of Wyoming Landscapes - page 83

Chapter 6 Grasslands

Grasslands are characteristic of the plains east of
the Rocky Mountains and in several intermountain
basins (see fig. 1.5). Some have been plowed for crop
production—mostly winter wheat—but large areas of
native vegetation can still be found (fig. 6.1). Prong-
horn are common. Diversity is added to the landscape
by scattered woodlands of ponderosa pine, limber pine,
and juniper on outcrops of resistant bedrock, and by
sand dunes and badlands (see chapters 8 and 9).
Most grasslands in Wyoming have been classified
into two categories. one, known as shortgrass prairie,
is found only in the southeast corner of the state and
has buffalo grass and blue grama as co-dominants. 1 the
other, mixed-grass prairie, covers a larger area (about
17 percent), extending northward into Montana. Usu-
ally mixed-grass prairie does not have buffalo grass.
Sometimes the grasses in both types of grassland grow
in small clumps and are known as bunch grasses, most
notably blue grama, junegrass, Sandberg bluegrass, and
indian ricegrass. others, such as western wheatgrass and
prairie sandreed, have rhizomes and are sod formers. 2
Grasses provide most of the biomass in grasslands, but
forbs, succulents, and small shrubs provide most of the
plant diversity. 3
Mixed-grass prairie often has 50 or more differ-
ent kinds of plants in an area as small as 2 or 3 acres.
common species include blue grama, indian ricegrass,
junegrass, needle-and-thread grass, Sandberg bluegrass,
western wheatgrass, needleleaf sedge, threadleaf sedge,
fringed sagewort, Hood's phlox, pricklypear cactus,

scarlet globemallow, and various species of milkvetch
and locoweed. Foothill grasslands at slightly higher
elevations may have some of the same species, but
others are more typical, such as bluebunch wheatgrass.
Some plants are good indicators of soil characteristics.
For example, sandy soils often have an abundance of
indian ricegrass, prairie sandreed, sand dropseed, sand
sagebrush, and yucca, whereas saline soils have alkali
sacaton, fourwing saltbush, greasewood, and inland
saltgrass. the most common soil types of upland
grasslands, known as Aridisols, have accumulations of
sand, silt, clay, and organic matter along with varying
amounts of lime (calcium carbonate), gypsum (hydrated
calcium sulfate), or various soluble salts. in swales and
along drainages, where plant growth is comparatively
high for a longer period of time each year, the soils have
more organic matter and are known as Mollisols (see
appendix B).
Some grasslands merge—gradually or abruptly—into
shrublands dominated by sagebrush or woodlands dom-
inated by juniper, limber pine, or ponderosa pine. Silver
sagebrush is common on sandy soils, in swales, and
along drainages; Wyoming big sagebrush is common
in the intermountain basins (see chapter 7). Sand sage-
brush is common on dunes, such as near torrington,
though it is less widespread in Wyoming than in east-
ern colorado. Around the world, shrubs are invading
grasslands in a surprising number of places, a trend that
has been attributed to various combinations of factors,
including less frequent fires, excessive grazing by large

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