Native Grassland of Southwestern Iowa

Studies of the prairie by the writer and Fitzpatrick during 1922-33 were both extensive and intensive. They were extensive in that they included an area of 60,000 sq. mi. in western Iowa, eastern Nebraska and portions of the four adjoining states. They were intensive in that a record of the kinds and distribution of grasses, the abundance and relative importance of forbs, and other pertinent data were ascertained and recorded separately for each of 135 selected areas. Since most of these prairies were examined two or more times each growing season, and many repeatedly during a five-year period, a clear, concise description of each was secured. In this study it soon became clear that the vegetation receiving an annual rainfall of 30-32 in. was better developed in many ways than that in the drier areas westward and northward with 25-29 in. mean annual precipitation. Some of these differences were pointed out by Weaver avid Fitzpatrick (1932. 1934) but the prairie was considered in its entirety and space did not permit descriptions of individual prairies. Further studies of the prairie as affected by the great drought of the 1930's (Weaver and Albertson 1936, 1944) and the history of their degeneration under grazing (Weaver and Hansen 1941 ) emphasized the importance of the isohyet of 32 in. as marking the place of beginning of rapid change from the mesic prairies of southwestern Iowa to the more xeric ones northward and westward. During the first quarter of the present century prairie hay for horses was still in considerable demand. But this was rapidly decreased with the general use of the automobile and especially the farm tractor. Not only did the need for hay decrease, but also the prairie was readily broken by use of plow and tractor. Moreover, the farmer could now easily cultivate his expanding fields of maize. Several fine remaining Iowa prairies some of 80 or more acres were broken during our earlier study and many others since that time. Indeed, it seems that all will vanish (Hayden 1946). Therefore it was decided to write the description of a typical tract of wellwatered Iowa prairie that was visited many times (luring and since 1929. Names of grasses are according to Hitchcock and Chase (1950) revised Manual of the Grasses of the United States. Other scientific names follow Gleason's (1.952) New Britton and Brown Illustrated Flora.