North American Prairie

The North American Prairies

The term prairie derives from the French and was the word French trappers and explorers gave to the sea of grass they encountered in the center of North America. As a vegetation type, the prairie is divided into three formations:

  • Tall grass prairie. The easternmost section of the North American grasslands, the tall grass prairie extends into regions of humid climate.  With the extermination of the bison and the suppression of prairie fires in the late 1800s, that part of the prairie that had not been put under the plow reverted to oak-hickory forest in the US and to aspen woodland in the north, in Canada. Today prairie preserves are managed with controlled burns.

    The tall grass prairie gets its name from the upright bluestemsEEvakyatuibakjdkjahfkjahfYouwwillCTTTT that reach heights of 6 feet or more by late summer. Their roots may extend to depths of 9 feet or more, binding the soil and enriching it with organic matter as roots die back at the end of the growing season. The above-ground parts of the plants also die down in winter and are converted to abundant humus when bacterial action begins in the spring.

    Three herb layers are apparent in the tall grass prairie, each characterized by relatively high species diversity. Both sod-forming and bunch grasses are present. Perennials are abundant and varied; different species bloom at different times during the growing season contributing to an ever-changing palette of colors. Bluestems comprise the uppermost herb layer. Other, shorter upright grasses an intermediate layer. Species such as the grama grasses (Bouteloua spp.) make up the lowest, ground-hugging layer. 

  • The mixed prairie. Centrally positioned between the tall grass and short grass prairies.  It has two layers of grasses and, one reaching about 12 inches above the ground surface, the other, more open, about 48 inches. Both bunch and sod-forming grasses are present. Roots extend to depths of about 5 feet. The soils are dark brown.

  • Short grass prairie. The westernmost and driest part of the North American grasslands, the short grass prairie occupies regions with 10 to 12 inches of precipitation a year. A single herb layer exists and consists primarily of bunch grasses some 12 to 18 inches high. They have relatively shallow root systems. Soils are lighter brown than those under the other two formations. These grasslands are used today as rangeland for cattle. Due to excellent game management practices some states with short grass prairie still have large populations of pronghorn. Elk, feral horses, and mule deer also share the range with cattle. Bison still occur but are privately owned or are maintained on special federal reserves.