| Desolate,
forbidding? There was never a country that in its good
moments
was more beautiful. Even in drought, duststorm or blizzard
it is the reverse of monotonous, once you have submitted
to it. |
Wallace Stegner, Wolf Willow
|
| The
Grasslands |
The first
settlers traveling west across the prairie may not have noticed
the gently rolling hills and purple-red vistas. Theirs was a
difficult journey of incredible monotony over trackless grassland.
Even today, the prairie landscape inspires little more than
a casual glance out the car window. Perhaps, though, it is worth
knowing that of the four major types of natural vegetation communities,
the grasslands is the largest - 24% of the earth's vegetation.
Grasslands or prairies once covered one third of the continent.
Wind Cave National Park offers the opportunity to explore a
remnant of this once vast ecosystem.
The conditions
that led to the present grassland are relatively recent.
From
the middle Miocene (about 15 million years ago) through the
Holocene (about 8,000 years ago) the climate changed, causing
a gradual shift in vegetation from semi-open woodlands
to
open grassland. As the amount of water evaporated exceeded
the amount of water precipitated, these grasses, which
are
better adapted to arid climates, out-competed the trees and
shrubs of the forest.
|
| Mixed
Grass Prairie |
Wind Cave
National Park is located where the grasslands meet the ponderosa
pine forests of the uplifted Black Hills. Here, there is blending
of the tall grass prairie species of the eastern Great Plains
and the short grass species of the western Great Plains. These
eastern and western prairies are differentiated by the types
of forbs (herbaceous plants) and grasses found there. Each
type reflects the amount of available moisture which decreases
from
east to west. The species composition is determined by the
climate, fire frequency, and the degree and frequency of
grazing. The
mixed grass prairie is an ecotone that results where species
composition is constantly shifting between the tall and
short
grass prairies. |
| The
Prairie Plants |
A plant
community is the result of biotic factors (vegetation genetics,
grazing), abiotic factors (climate, mineral soil, moisture)
and their interactions. Since abiotic factors vary in even small
areas, habitat gradients are produced. Because of this, many
unique plant communities result such as big bluestem grass growing
in depressions and needle-and-thread grass growing on eroded
hillsides.
There
are approximately 140 million acres of mixed grass prairie
in North America. Although grasses provide the most material
(80 to 90% biomass), only 20% of the plant species are grasses.
The rest are forbs which add to the diversity of forage, important
for browsing animals like the pronghorn.
|
| Plant
Adaptation |
Grasses
are able to maximize their growth and production even with constantly
changing environments. They send more than half of their tissue
or their roots, below the ground. This helps build and hold
soil and creates a food store that the plants use during dominate
periods such as winter or during droughts. Grasses have also
adapted to pressure from grazing. Silica is assimilated by the
plant into its cell walls. This makes the leaves coarse and
less palatable. Also, the growing parts are at the base of the
plant, so cropping off the top will not kill the plant. When
the photosynthesizing tissue is removed by grazing, the rate
of photosynthesis within the uneaten tissue is increased. |
| Growing
Seasons |
In response
to wide temperature fluctuations, grasses have evolved to cool-
and warm-season species. Cool-season grasses, such as needle-and-thread
grass, grow well in the spring and fall when the temperatures
are cooler and more water is available. Warm-season grasses,
such as blue grama, await the summer months. They grow best
in high temperatures. |
| Surviving
the Winter |
By winter
the aerial portions of grasses have died and most of the plants'
energy has been transferred to the root system. What remains
is known as standing dead, the dry carpet of grass that crunches
underfoot. This dead material is an important source of food
for the grazing animals throughout the winter. It also provides
fuel for periodic fires. |
| Prairie
Fires |
Fires burn
the built up layers of dead material from previous years. It
is fire that has helped shape the grassland community by killing
competing trees and shrubs, effectively maintaining the balance
between the forest and prairie. During a fire, most of the grass
remains unharmed in the ground. After the fire, grasses benefit
as more space, light and water become available for more growth. |
| The
Future of the Prairie |
The prairie
is home to a variety of plants and animals. It is a place where
deer, coyotes, pronghorn, prairie dogs, eagle, hawks and other
wildlife flourish. The prairie is not only valued for its biodiversity,
but for the wide-open space and magnificent beauty found there.
With the westward advance and agricultural development of the
grasslands it has become difficult to understand the prairie
ecosystem. Continued management is needed to maintain and understand
it. Wind Cave National Park and other protected areas offer
us a glimpse of this vanishing community and an opportunity
to understand it better. |
| Additional
Reading |
The
Prairie World. David Costello. Thomas Y. Crowell Company,
New York, 1969.
The Shortgrass Prairie. Ruth Carol Cushman & Stephen
R. Jones. Pruett Publishing Company, 1988.
A Tour on the Prairies. Washington Irving. Pantheon
Books, New York. 1967.
Giants in the Earth. Ole Rolvaag. Harper, New York,
1987. |
| Other
Places to Visit |
Badlands
National Park, P.O. Box 6, Interior, SD 57750
Buffalo
Gap National Grasslands, P.O. Box 425, Wall, SD 57790
Theodore Roosevelt National
Park, P.O. Box 7, Medora, ND 58645
Agate Fossil Beds National
Monument, P.O. Box 427, Gering NE 69341
Toad Stool Park, within the Ogalala National Grassland. P.O.
Box 13A9, Chadron, NE 69337 |
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