The New International Encyclopædia/Prairie

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PRAIRIE (Fr. prairie, It. prateria, from ML. prataria, meadowland, from Lat. pratum, meadow). In general, an undulating, grass-covered plain, as distinguished from a forested plain on the one hand and a semi-arid region or steppe on the other. The name is applied more specifically to the extensive plain which stretches from southern Michigan and western Ohio across Indiana, Illinois, Missouri, Iowa, Wisconsin, and Minnesota, thus including almost the entire area between the Ohio and the Missouri-Mississippi rivers. West of the Missouri River this level expanse is continued by the Great Plains to the base of the Rocky Mountains, while on the east it merges imperceptibly into the Alleghany Plateau. Its surface is unbroken by marked elevations, but the monotony is relieved by the broad undulations and by the channels of the streams tributary to the Ohio, Mississippi, and Missouri, which have been worn down in places so as to expose vertical walls or bluffs 100 feet or more in height. The elevation above sea-level ranges from 300 to 1500 feet. The prairies are underlaid by Paleozoic sandstones and limestones in nearly horizontal position; but the surface formation is largely of glacial origin and consists of boulder clay and sand more or less rearranged and decomposed by weathering and erosion. A fine sandy deposit resembling the loess of China occurs over wide areas in the Mississippi Valley. The prairies are characterized by a heavy rich soil admirably adapted for the growth of cereals, and while formerly covered only with grass and supporting herds of buffalo and deer, they have been brought under a high state of cultivation. As to the characteristics of their vegetation, prairies may be divided into two general groups: climatic, which include typical portions of the western part of the Mississippi Valley; and edaphic, which are smaller and are developed almost without exception from swamps. Among the theories commonly held to account for the treelessness of the great Western prairies are: (1) the lack of sufficient rainfall; (2) the grazing of animals and the action of fire; and (3) the excessive transpiration, due to wind—all of which prevent the growth of trees. In apparent proof of the first theory, trees gradually disappear as the distance from the seaboard increases, and this change is paralleled by a gradual reduction in the rainfall; of the second, trees have appeared in some parts of Kansas and Nebraska, where cattle-grazing and prairie fires have been stopped; of the third, transpiration is so great, especially during winter, that certain trees cannot be successfully grown unless in situations sheltered from the winds. Perhaps all of these theories are more or less tenable. See United States; Indiana; Illinois; etc.