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NATURALIST'S GUIDE TO THE AMERICAS 



2. IOWA 

 BY L. H. PAMMEL 



I. PHYSIOGRAPHIC CONDITIONS AND 

 ORIGINAL BIOTA 



Iowa was originally an oak grove 

 savanna state intersected by streams. 

 The lowlands, bottoms, and adjacent 

 hill slopes were in great part covered 

 with deciduous trees. In order to 

 understand its flora and fauna we must 

 take into account the various drift 

 sheets which covered most of Iowa. 



The Kansas drift sheet covered the 

 entire state with the exception of a 

 little portion in northeastern Iowa and 

 Dr. Kay now tells us that even this 

 area did not escape the ice. The typi- 

 cal Kansas topography is well shown in 

 southern Iowa in Henry and Monroe 

 counties. The topography is much 

 dissected, the surface features conform- 

 ing to the drainage lines. There are 

 large flat areas which before the advent 

 of man were prairies. These areas 

 conform to the original plane before 

 erosion occurred. The soil consists of 

 a blue boulder clay which is often quite 

 compact. A clayey silt, loessial in 

 character, veneers the surface. A sec- 

 ond drift sheet, the Iowa, occurs in 

 northeastern Iowa. This in Linn, Buch- 

 anan and adjacent counties is charac- 

 terized by the numerous very large 

 boulders. One of the largest of these in 

 Floyd County near Nashua is perhaps 

 the largest boulder in the Mississippi 

 valley. There are many peat patches 

 and the lakes, if any, are reduced to 

 small ponds. The streams are shallow 

 and the flood plain as well as the ad- 

 jacent uplands were covered with a 

 deciduous forest. There is little of 

 topographic form. The hills are gentle 

 and rise but little above the flood plain 

 of the streams. There is very little 

 erosion. The soil is a yellow calcareous 

 clay veneered with sand and humus. 

 The Illinoian drift covers only a small 

 part of the state in the region of Bur- 

 lington. The Wisconsin drift, the most 

 recent of the drift sheets is charac- 



terized by its rolling hills. It extended 

 into Iowa in the form of a great lobe 

 entering the state in a southeastern 

 direction in the western part on the 

 Iowa Minnesota boundary a little west 

 of the lake region in Osceola County, 

 and on the east, at Clear Lake Cerro 

 Gordo County, in a southwesterly 

 direction to Polk County. This area 

 abounded in lakes. Many of these 

 have been drained. Some 50 of them 

 still remain. Lake Okoboji, Spirit Lake, 

 Storm Lake, Clear Lake, Silver Lake, 

 Twin Lakes and Wall Lake are in the 

 Wisconsin drift sheet. It is in this 

 area that peat bogs are most numerous, 

 some of them covering 300 to 400 acres. 

 In such bogs occur typical northern 

 bog .plants like the swamp thistle (Cir- 

 sium muticum), bog willow (Salix 

 pedicellaris}, and beaked willow (S. 

 rostratd). The state was dissected by 

 the following streams; the Des Moines, 

 Little Sioux, Iowa, Cedar, Oneota and 

 Skunk, all of which have their source in 

 the lake region of the Wisconsin drift. 

 The Little Sioux drains to the Missouri 

 and has its source in the lake region of 

 Dickinson County. 



II. BIOTA 



The greater part of the state was 

 prairie and before extensive drainage 

 began there were many sloughs espe- 

 cially in the Wisconsin drift sheet. In 

 this area there is also much morainic 

 material. On the shores of most of the 

 lakes was a narrow fringe of deciduous 

 trees and shrubs and the red cedar. 

 (Juniperus virginiana). The timbered 

 area around most of these lakes has 

 been much reduced in size. 



There are very few evergreens in the 

 state. The red cedar has the widest 

 distribution. This species extends all 

 the way across the state, especially in 

 the north. Not so far west in the south 

 half of the state. White pine (Pinus 

 strobus) occurred originally in small 

 belts and isolated groves. Isolated 

 areas of white pine occurred in Alla- 

 makee, Winneshiek, Clayton and Dub- 

 uque counties with a few isolated groves 



