Buffalo Gap National Grasslands - Grassland Environments
There is today an enthusiastic ground swell of interest in the grasslands. Traditionally, nature lovers and outdoorspeople have turned to the mountains and the seashores for relaxation and enjoyment. Until recently, like the emigrants on the Oregon trail, most of us have hurried to get across our grasslands as quickly as possible.
While humid climates support forests and dry ones support deserts, the grasslands require a moisture level somewhere in between (semi-arid). Moreover, grasslands have a distinctive character. Unlike deserts, the vegetation forms a relatively solid cover over the ground, and unlike forests, the space is open and the view is endless.
Grasslands are one of the most extensive, productive ecosystems in the United States. In spite of the limitations imposed by climate, grasslands present tremendous diversity as they change throughout the seasons and over the years. The existence of the American grasslands is marked by irony. After many millennia of evolution, much of the grasslands were transformed to croplands within half a century by the European settlers.
Grasslands have not vanished completely. There are nearly four million acres of National Grasslands, where one can still explore native prairie.
Types of Grasslands
The largest grassland formation is a huge area covered by tallgrass, mixedgrass, and shortgrass prairies that stretches from the Mississippi River to the Rocky Mountains called the Great Plains. The names of these three grassland types are descriptive: the tallgrass prairie, which requires more moisture than the other two, is dominated by grasses that are over four feet high; the shortgrass prairie, which requires the least moisture, is dominated by grasses that are less than two feet high; the mixed grass prairie contains a mosaic of grasses, with patches of tallgrass growing in rich, wet soils, and shortgrass covering dry, rocky soils.
All grasslands have certain characteristics in common. They generally exist on flat or rolling terrain, and the annual precipitation averages between ten and forty inches. However, quantity alone does not tell the whole story. The time of year when the precipitation falls is also important. In most grasslands, precipitation is concentrated in peak periods; thus stretches of drought occur annually. Moreover, there are great fluctuations from year to year. At Buffalo Gap peak precipitation occurs during May through July and annual precipitation has varied from seven to twenty-six inches.
Because there are few obstacles to air movement, wind is another factor in the climate of grasslands, especially in the Great Plains. Here the wind seems to blow constantly. As it blows, the wind evaporates water from the soil and plants, thereby aggravating the already dry conditions.
The Grass Plant
Of all the plants of the earth, the grasses are of the greatest use to people. Almost all of our food comes—either directly or indirectly—from grasses. Many of the important crop plants are grasses: wheat, corn, rice, oats, barley, rye, and sorghum. Meat-producing animals eat crop plants originating from grasses or graze grasses on the open range. Grasses are also used extensively in landscaping around homes and parks for aesthetics and recreational purposes.
As a group, grasses are easy to recognize. However, their lack of brightly colored flowers may make them seem dull compared to wildflowers, as well as making them difficult to distinguish from each other. Thus many people find grasses confusing and simply take them for granted.
Grasses are herbaceous, that is they do not form woody tissue nor do they increase in girth as trees do. Grass flowers are small and inconspicuous, and are arranged either in tight vertical clusters called spikes or in many branched clusters called panicles.
Special Adaptations
Several characteristics of grasses represent adaptations to the grassland environment. First, the narrow leaves of grasses, arranged more or less vertically along the stem, present less surface area for evaporation of water and provide for maximum photosynthetic efficiency.
Second, a large proportion of grasses' biomass exists underground in their root systems. The extensive root system presents several advantages. In areas of sparse precipitation, the grass plants establish contact with the deeper, moister layers of soil. In addition, the large root system provides a defense against grazing, mowing, and fire. When a significant portion of the above-ground tissue of a grass plant is removed or destroyed, enough energy is stored in the root system to make new growth possible.
Third, perennial grasses' defense against grazing is a sophisticated process which involves the leaves' unusual growth system. In most plants, the actively growing cells are located at the tips of the leaves. In grasses, however, the growing center is at the base of the leaf, where it joins the stem, and the tip of the leaf is the oldest tissue. Therefore, if the upper portion of the leaves is mowed or grazed, the plant renews growth from its base.
Buffalo Gap lies within the mixed grass prairie zone and contains grass species from both the tallgrass and shortgrass communities. Forty-seven species of grasses occur regularly within its boundaries. In addition to grass species, there are several species of sedges that occur from the dry uplands to the wetlands. Sedges are similar in many respects to grasses and are frequently called grass-like. They may generally be distinguished from grasses by their triangular solid stems with leaves attached on all three sides. Two of the most common upland sedges found at Buffalo Gap are needleleaf sedge (Carex eleocharis) and threadleaf sedge (Carex fififolia).
Bibliography
The following field guides are available through the Badlands Natural History Association at the National Grasslands Visitor Center in Wall, SD
Art, Henry W. 1991, The Wildflower Gardener's Guide. Garden Way Publishing
Art, Henry W. 1988, Creating a Wildflower Meadow. Storey Country Wisdom
Gilmore, Melvin R. 1977, Uses of Plants by the Indians of the Missouri River Region
Kindscher, Kelly. 1992, Medicinal Wildplants of the Prairie. University Press Kansas
Kindscher, Kelly. 1987, Edible Wildplants of the Prairie. University Press Kansas
Van Bruggen, Theodore. 1992, Wildflowers, Grasses, and Other Plants of the Northern Plains and Black Hills, Badlands Natural History Association
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