The Loess Hills of Western Iowa: a Problem in Phytogeography

Based upon personal observations over a four year period, a preliminary overview of the phytogeographical significance of the prairies of the Loess Hills of western Iowa is discussed, concentrating upon a few representative taxa. A number of Great Plains vascular plant species reach the easternmost edge of their ranges in the Loess Hills. Climatic changes during the Holocene Period, especially during the Hypsithermal Interval, have had great effects upon the vegetation of the Great Plains and upon the xerophytic components of the Loess Hills. In addition, recent extended drought episodes have affected the flora. It is postulated that the Missouri River system has served, and may still serve, as a major migratory route for many of the Great Plains species found in the Loess Hills