LEVEL III AND IV ECOREGIONS OF ILLINOIS

by

Alan J. Woods

1

James M. Omernik2

Charles L. Pederson3

Brian C. Moran4

EPA/600/R-06/104

September, 2006

1

Department of Geosciences, Oregon State University

U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory

200 SW 35th Street

Corvallis, Oregon 97333

2

U.S. Geological Survey

U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory

200 SW 35th Street

Corvallis, Oregon 97333

3

Department of Biological Sciences, Eastern Illinois University

Charleston, Illinois 61920

4

Indus Corporation

U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory

200 SW 35th Street

Corvallis, Oregon 97333
2

TABLE OF CONTENTS

Page

INTRODUCTION ............................................................................................................................................................3

PRIMARY SOURCES FOR ILLINOIS ECOREGION INFORMATION ....................................................................4

REGIONAL DESCRIPTIONS .................................................................................................................................... 5-17

52. DRIFTLESS AREA ........................................................................................................................................5

52a. Savanna Section.................................................................................................................................6

52b. Paleozoic Plateau/Coulees Section...................................................................................................6

53. SOUTHEASTERN WISCONSIN TILL PLAINS ........................................................................................7

53a. Rock River Drift Plain .....................................................................................................................7

53b. Kettle Moraines .................................................................................................................................7

54. ILLINOIS/INDIANA PRAIRIES ..................................................................................................................8

54a. Illinois/Indiana Prairies ....................................................................................................................8

54b. Chicago Lake Plain ...........................................................................................................................9

54c. Kankakee Marsh ...............................................................................................................................9

54d. Sand Area...........................................................................................................................................9

54e. Chiwaukee Prairie Region .............................................................................................................10

54f. Valparaiso Morainal Complex........................................................................................................10

54g. Rock River Hills .............................................................................................................................10

71. INTERIOR PLATEAU..................................................................................................................................11

71m. Northern Shawnee Hills..................................................................................................................11

71n. Southern Shawnee Hills..................................................................................................................11

72. INTERIOR RIVER VALLEYS AND HILLS .............................................................................................12

72a. Wabash–Ohio Bottomlands............................................................................................................13

72b. Glaciated Wabash Lowlands ..........................................................................................................13

72d. Upper Mississippi Alluvial Plain....................................................................................................13

72e. Middle Mississippi Alluvial Plain .................................................................................................14

72f. River Hills........................................................................................................................................14

72g. Southern Ozarkian River Bluffs.....................................................................................................14

72i. Western Dissected Illinoian Till Plain ...........................................................................................15

72j. Southern Illinoian Till Plain ...........................................................................................................15

72k. Cretaceous Hills...............................................................................................................................16

72l. Karstic Northern Ozarkian River Bluffs........................................................................................16

72m. Wabash River Bluffs and Low Hills..............................................................................................16

73. MISSISSIPPI ALLUVIAL PLAIN...............................................................................................................17

73a. Northern Holocene Meander Belts.................................................................................................17

LIST OF REFERENCES............................................................................................................................................ 18-23

PROJECT FUNDING.......................................................................................................................................................23

PEER REVIEWERS.........................................................................................................................................................23

TABLE 1: Common and Scientific Names Cited in Text ..................................................................................... 24-26

TABLE 2: Summary Table – Characteristics of the Ecoregions of Illinois ......................................................... 27-43

FIGURE 1: Illinois Level III and IV Ecoregions (map).......................................................................................... 44-45
3

INTRODUCTION

Ecoregions denote areas of general similarity in ecosystems, and in the type, quality, and quantity of

environmental resources. They are general purpose regions that are useful for structuring and implementing

ecosystem management strategies across political boundaries (such as state lines) and across agencies (Omernik and

others, 2000). Ecoregions stratify the environment according to its probable response to disturbance, and recognize

the spatial differences in the capacities and potentials of ecosystems (Bryce, Omernik, and Larsen, 1999).

Ecoregion frameworks are useful for 1) inventorying and assessing national and regional environmental

resources, 2) setting regional resource management goals, 3) establishing geographical research frameworks, and 4)

developing regional biological criteria and water quality standards (Arkansas Department of Pollution Control and

Ecology, 1988; Bazata, 1991; Environment Canada, 1989; Gallant and others, 1989; Heiskary and Wilson, 1989;

Hughes, 1989b; Hughes and others, 1987, 1990, 1994; Larsen and others, 1986; Lyons, 1989; Ohio Environmental

Protection Agency, 1988; Plotnikoff, 1992; Rohm and others, 1987; U.S. Environmental Protection Agency, Science

Advisory Board, 1991; Warry and Hanau, 1993; Whittier and others, 1988).

Ecoregion frameworks have been developed for several countries, including the United States, Canada,

New Zealand, and the Netherlands (Bailey, 1976, 1983, 1995; Bailey and others, 1985, 1994; Biggs and others,

1990; Ecological Stratification Working Group, 1995; Klijn, 1994; Omernik, 1987, 1995a; Omernik and Gallant,

1990; U.S. Environmental Protection Agency, 2005; Wiken, 1986). The first compilation of ecoregions in the

conterminous United States by the U.S. Environmental Protection Agency (U.S. EPA) was performed at a relatively

cursory scale (1:3,168,000), and was published at a smaller scale (1:7,500,000) (Omernik, 1987). Subsequently, this

ecoregion framework was expanded to include Alaska and all of North America, revised, and made hierarchical

(Gallant and others, 1995; Omernik, 1995b; U.S. Environmental Protection Agency, 2005).

Level I is the coarsest level in the ecoregion hierarchy; it divides North America into 15 ecological regions.

Level II divides the continent into 50 regions. At level III, the continental United States contains 104 ecoregions,

whereas the conterminous United States has 84. Level IV ecological regions are further subdivisions of level III

ecoregions. The exact number of ecological regions at each hierarchical level is still changing slightly as the

framework undergoes development at the international, national, and state levels.

Detail resolution on Omernik’s (1987) ecoregion map of the conterminous United States was necessarily

limited by its rather small scale of 1:7,500,000. Subsequently, many larger scale, collaborative, state projects refined

Omernik’s original ecoregion map, and subdivided its level III ecoregions into level IV ecoregions. Completed level

IV ecoregion projects cover Alabama, Arkansas, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Indiana,

Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Mississippi, Missouri, Montana, Nebraska, Nevada,

North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South

Dakota, Tennessee, Texas, Utah, Virginia, Washington, West Virginia, Wisconsin, and Wyoming. Other state level

IV ecoregion projects are still in progress including Minnesota, New Jersey, and New Mexico. These level IV

ecoregion projects have involved state agencies, U.S. EPA regional offices, and the U.S. EPA–National Health and

Environmental Effects Research Laboratory, Western Ecology Division in Corvallis, Oregon. Projects have included

participation by the U.S. Department of Agriculture–Natural Resources Conservation Service and the U.S.

Department of Agriculture–Forest Service as part of an interagency effort to develop a common framework of

ecological regions.

In this paper we refine the level III ecoregions of Illinois, subdivide them into more detailed level IV

subdivisions, and provide descriptions and summary information for each ecoregion in the state. Illinois has 6 level

III and 25 level IV ecoregions; all but 8 continue into ecologically similar parts of adjacent states (Chapman and

others, 2001, 2002; Griffith, 1994; Omernik and others, 2000; Woods and others, 1998, 2002).

The work in Illinois was done in cooperation with U.S. EPA Region 5. The Illinois ecoregionalization

project involved personnel from several state agencies, federal agencies, and universities, including the Illinois

Environmental Protection Agency (Illinois EPA), Illinois Natural History Survey, Illinois State Geological Survey,

Illinois State Water Survey, U.S. Department of Agriculture–Natural Resources Conservation Service (NRCS), and

Eastern Illinois University. This project was partly conducted under the auspices of the Program for Cooperative

Research on Aquatic Indicators Award # CR-831682-01.

The procedures used to define Illinois ecoregions are consistent with those that were used in preceding U.S.

EPA ecoregion studies of neighboring states (Chapman and others, 2001, 2002; Griffith, 1994; Omernik and others,

2000; Woods and others, 1998, 2002). They are based on the premise that ecological regions can be identified

through the analysis of biotic and abiotic characteristics that affect or reflect differences in ecosystem quality and

integrity (Omernik, 1987, 1995a; Wiken, 1986). Spatial pattern, composition, and spatial correspondence of

physiography, natural vegetation, soil, surficial and bedrock geology, climate, land use, land cover, wildlife, and fish
4

were considered as part of the process. The relative importance of each biotic and abiotic characteristic varied from

one ecological region to another regardless of the ecoregion hierarchical level. Expert judgment was employed

throughout the selection, analysis, and classification of data to define the ecoregions. Information from the literature

and input from state and regional experts were very important to this project, as well as the earlier ones in

neighboring states. Ecoregion lines were compiled at 1:250,000-scale onto 1:250,000-scale topographic base maps.

More detailed explanations about the methods, materials, rationale, and philosophy for the ecoregionalization

process can be found in Gallant and others (1989), Omernik (1995a), and Omernik and Gallant (1990).

Evaluation of the ecoregion framework presented in this paper is a necessary future step. U.S. EPA

ecoregions have been evaluated extensively in the past, and the most meaningful of these efforts have involved the

use of measures of water quality and indices of biotic integrity (IBI’s) (Hughes, 1989a; Larsen and others, 1986,

1988; Whittier and others, 1987; Yoder and Rankin, 1995). A better tool would be a more encompassing index of

ecological integrity (IEI) (Omernik, 1995a, 1995b); although an IEI is not available yet, there is considerable interest

in at least two states to begin its development. Verification of ecoregions cannot be done by considering individual

ecosystem components; this is because the ecoregion framework was not intended to show regional patterns specific

to either the flora or fauna of terrestrial ecosystems, nor was it intended to reflect distributions of fish or aquatic

macroinvertebrates.

PRIMARY SOURCES FOR ILLINOIS ECOREGION INFORMATION

The Illinois ecoregion delineations are based on several criteria: 1) physiography, 2) natural vegetation, 3)

soil, 4) surficial and bedrock geology, 5) climate, 6) land use and land cover, and 7) regional biogeography. Primary

sources for ecoregion delineations, descriptions, and summary tabular information are listed below. A list of

references is also included in this report. Small scale maps of Illinois’ physical and cultural attributes are available from

Fehrenbacher and others (1967), Horsley (1986), Neely and Heister (1987), Nelson (1978), and Schwegman (1973).

1) Physiographic information was gathered from Bier (1980), Dahlberg and others (1985), Fenneman

(1938), Fryxell (1932), Hammond (1970), Leighton and others (1948), Neely and Heister (1987), Nelson (1978),

Schwegman (1973), Summers and others (1980), and both 1:100,000- and 1:250,000-scale topographic maps.

2) Natural vegetation information was obtained from several sources, including Gleason (1910), Neely and

Heister (1987), Schwegman (1973), Summers (1980), Szafoni and others (on-line resource), Vestal (1931), Winsor

(1987), and Wright (1968). Potential natural vegetation information came from Kuchler (1964).

3) Soil information was gleaned from many sources, including Fehrenbacher and others (1967, 1968,

1978), Mausel (1969, 1970), the State Soil Geographic (STATSGO) digital map (Natural Resources Conservation

Service, no date), official soil descriptions (Natural Resources Conservation Service (on-line resource), county soil

surveys (Natural Resources Conservation Service, various dates), Nelson (1978), Schwegman (1973), and Thorp (1968).

4) Surficial and bedrock geology information came from Illinois State Geological Survey (2000), Lineback

(1979), county soil surveys (Natural Resources Conservation Service, various dates), Nelson (1978), Richmond and

Fullerton (1983, 1991), Richmond, Fullerton, and Christiansen (1991), Richmond and Weide (1993), Schwegman (1973),

Weibel and Panno (1997), Willman and Frye (1970, 1980), and Kolata (2005) (supersedes Willman and others (1967).

5) Climate information, including growing season, precipitation, and temperature data for the 1971-2000 time

period, came from the Illinois State Climatologist Office (on-line resource).

6) Land use and land cover information came from several sources, including the land use classification of

Anderson (1970), the 2002 Census of Agriculture (National Agricultural Statistics Service (on-line resource), county

soil surveys (Natural Resources Conservation Service, various dates), the 1991-1995 land cover atlas by the Illinois

Department of Natural Resources (on-line resource “a”), the seasonal land cover map by Loveland and others

(1995), and the land cover map by Luman and others (2004) (supersedes Luman and others (1997).

7) Regional biogeographic information was derived from sources including Keys and others (1995),

McMahon and others (2001), Neely and Heister (1987), Schwegman (1973), Smith (1971), Summers and others

(1980), Vestal (1931). Distribution maps for Illinois flora and fauna came from the Center for Biodiversity at the

Illinois Natural History Survey (Illinois Natural History Survey, on-line resource). Lists of threatened and

endangered species in Illinois came from the Illinois Endangered Species Protection Board, Illinois Department of

Natural Resources (Illinois Department of Natural Resources, on-line resource “b”).

In addition, information also came from collaborators including Candice Bauer (U.S. EPA), Bill Ettinger

(Illinois EPA), Gregg Good (Illinois EPA), Ed Hammer (U.S. EPA), Mark Joseph (Illinois EPA), Don Keefer

(Illinois State Geological Survey), Laura Keefer (Illinois State Water Survey), Andrew Phillips (Illinois State

Geological Survey), Don Pitts (NRCS), Mike Retzer (Illinois Natural History Survey), and Roy Smoger (Illinois

EPA).
5

REGIONAL DESCRIPTIONS

Illinois has been divided into six level III ecoregions and 25 level IV ecoregions. Many of the boundaries of

these ecoregions are transitional, and the ecoregion map (Figure 1) should be interpreted with that in mind.

Ecoregion descriptions follow, and include differentiating criteria; their detail varies and depends on available

information. Figure 1 is the map of level III and IV ecoregions in Illinois. Table 2 contains ecoregion data

summaries in tabular format.

52 DRIFTLESS AREA

The partly forested Driftless Area (52) is underlain by carbonate-rich Paleozoic strata, and is covered by loess.

Glaciers and glacial deposits have done little to subdue Ecoregion 52’s terrain, in stark contrast to the neighboring till

plains of Ecoregions 53 and 54; characteristically, glacial till is generally absent from Ecoregion 52. Ecoregion 52

contains deeply dissected hills, rolling uplands, and flat plateau remnants; scattered caves and springs occur. Natural

lakes are fewer, stream density is greater, and stream networks are better developed than in the Southeastern Wisconsin

Till Plains (53). The Driftless Area (52) includes the highest point in Illinois, Charles Mound (1,257 feet elevation), and

the greatest relief in the state, where the Mississippi River has cut through the resistant Silurian dolomite of the Niagara

Escarpment. Mean daily low temperatures in winter are colder, and snow cover lasts longer than elsewhere in Illinois

(Changnon, 1969; Illinois State Climatologist Office, on-line resource; Nelson, 1978, p. 73).

The potential natural vegetation is maple–basswood forest and bluestem prairie; it is distinct from the

mosaic of prairie and oak–hickory forest that is native to the Central Corn Belt Plains (54), and lacks the oak–

savanna that is native to parts of the Southeastern Wisconsin Till Plains (53) (Kuchler, 1964). Ecoregion 52 is

characterized by distinctive northern plants (Neely and Heister, 1987, p. 28; Schwegman, 1973, p. 10).

Ecoregion 52 is underlain by Ordovician- and Silurian-age dolomite, limestone, and shale (Kolata, 2005).

Bedrock outcrops are common in valleys. Lead and zinc have been mined near the city of Galena since the early

19th century; more zinc is now produced than lead, but, between 1820 and 1865, this zone was the main source of

lead in the United States (Nelson, 1978, p. 222).

Mollisols and, especially, Alfisols are common in the Driftless Area (52). Soils formed from loess or, on

steepest slopes, from residuum and thin loess (Natural Resources Conservation Service, various dates). Loess thins

eastward from over 300 inches on bluffs along the Mississippi River to less than 100 inches; it is thinnest on steepest

slopes (Fehrenbacher and others, 1968, Figure 2).

Mixed land uses are a characteristic of the Driftless Area (52); cropland in Ecoregion 52 is not as extensive

as in Ecoregions 47 and 54 (Chapman and others, 2002), whereas forests are more widespread than in adjacent parts

of Ecoregions 47, 53, and 54. Today, land use in Ecoregion 52 largely reflects physiography; typically, agriculture is

found on uplands, a mixed assemblage of woodland and agriculture occurs on lowlands, and forests grow on steep

slopes, in canyons, and in riparian areas. Pastureland, mixed farms, and dairies occur; principal crops are feed grains

and forage for dairy cattle and other livestock.

Upland forests are most extensive on steep slopes; basswood, red oak, and sugar maple dominate mesic

slopes, whereas black oak and white oak are common on drier sites. Floodplain forests are dominated by American

elm, green ash, and silver maple (Schwegman, 1973, p. 10).

Perennial, spring-fed, cool water streams are common, but intermittent streams are found in ravines. Stream

quality ranges from fair to excellent. Upper reaches of the Apple River system have excellent quality, gravel riffles,

and clear pools (Smith, 1971, p. 4). Principal water quality issues in Ecoregion 52 as a whole are siltation

(particularly in downstream reaches) and pollution from livestock and dairy farms. Reservoirs generally have high

trophic states (Omernik and others, 2000).

Amphibian and reptile species richness is much greater than on the forested stream slopes of the Western

Dissected Illinoian Till Plain (72i) (Smith, 1961, p. 12).
6

52a Savanna Section

The partly forested hills of the Savanna Section (52a) contain flat plateau remnants, broad ridge tops,

narrow valleys, and buttes capped by resistant dolomite. Ecoregion 52a includes Charles Mound, the highest point in

Illinois at 1,257 feet elevation. Valley bottoms are narrower and ridges are less pronounced than in Ecoregion 52b.

Natural lakes are fewer, stream density is greater, and stream networks are better developed in Ecoregion 52a than in

the Southeastern Wisconsin Till Plains (53).

Alfisols are common, but Mollisols also occur. Upland soils are mostly well-drained. They developed from

loess or, on steepest slopes, from the residuum of underlying dolomite, limestone, and shale (Kolata, 2005); glacial

till-derived soils are generally absent in contrast to the neighboring Rock River Drift Plain (53a) where they are

extensive (Natural Resources Conservation Service, various dates).

In the early 19th century, dry to mesic prairies (often dominated by little bluestem and side-oats grama) and

oak savanna were widespread on rolling uplands and flat plateau remnants. Steeper slopes were covered by upland

hardwood forests (Schwegman, 1973, p. 10).

Today, land use in Ecoregion 52a reflects physiography; agriculture is found on the uplands, a mix of

woodland and agriculture occurs in lowland areas, and forests grow in canyons and on steep slopes. Pastureland is

common, and farms and dairies occur (Natural Resources Conservation Service, various dates). Overall, agriculture

is more common, and forest cover is less extensive, than in the more rugged Paleozoic Plateau/Coulees Section

(52b).

52b Paleozoic Plateau/Coulees Section

Ecoregion 52b is a rugged, deeply dissected, loess-covered plateau that is mostly forested; typically, relief

is greater, ridges are sharper, and hill slopes are steeper and more densely forested than in the Savanna Section (52a)

or in neighboring parts of Ecoregions 53 and 54. The greatest relief in Illinois occurs in Ecoregion 52b, where the

Mississippi River cuts through the resistant Silurian carbonates of the Niagara Escarpment (Nelson, 1978, p. 53).

This ragged escarpment is not always prominent; nevertheless, it separates the cropland-dominated Western Corn

Belt Plains (47) from the mixed land use of the Driftless Area (52).

Alfisols are common, but Mollisols also occur (Natural Resources Conservation Service, various dates).

Upland soils are mostly well-drained. They developed from loess or, on steep slopes, from the residuum of

underlying dolomite, limestone, and shale (Kolata, 2005); soils derived from glacial till are generally absent.

In the early 19th century, Ecoregion 52b was mostly covered by upland hardwood forest dominated by

sugar maple, basswood, and red oak, but loess hill prairies were found on steep, southwesterly facing river bluffs

(Schwegman, 1973, p. 10); overall, potential natural vegetation was distinct from the Savanna Section (52a) or the

Central Corn Belt Plains (54), where bluestem prairie was much more common (Kuchler, 1964).

Today, a mix of forest and agriculture occurs, with agriculture mostly confined to lowlands and flatter

hilltops. The decommissioned Savanna Army Depot covers about 13,000 acres, and supports over thirty endangered

or threatened plants and animals (Suloway and others, 1996).
7

53 SOUTHEASTERN WISCONSIN TILL PLAINS

Ecoregion 53 in Illinois is composed of nearly level to hilly till plains, nearly level outwash plains, and

hummocky to hilly morainal areas. Lakes and marshes are much more common than in the Central Corn Belt Plains (54)

or the Driftless Area (52), and the terrain is usually flatter than in Ecoregion 52. Drainage conditions vary with soil texture,

terrain, and stream network development. Dark-colored Mollisols and, especially, light-colored Alfisols are common, and

were derived from eastwardly thinning loess, westwardly thinning glacial drift, glacial outwash, residuum, or alluvium.

Histosols occur in depressional morainal areas, and developed from herbaceous organic deposits.

Ecoregion 53 naturally supports a mosaic of vegetation types, and acts as a vegetal transition between the

hardwood forests and oak savannas of ecoregions to the west, and the tall-grass prairies that originally dominated

Ecoregion 54 to the south (Omernik and others, 2000, p. 91). The potential natural vegetation is a mix of oak

savanna, bluestem prairie, maple–basswood forest, and oak–hickory forest (Kuchler, 1964). At the time of

settlement, forests were common on moraines, along water courses, and on dissected uplands, whereas prairie

occurred on level to rolling uplands (Schwegman, 1973, p. 11-12).

Today, more than half of Ecoregion 53 is used for agriculture; forests, wetlands, and home sites make up

the remaining area. Pastureland is found throughout the ecoregion. Cropland, on the other hand, occurs in the Rock

River Drift Plain (53a), but is uncommon in eastern morainal areas. Main crops are forage and feed grains

supporting local dairy and livestock farms, but cash-grain farming is also important.

Aquatic habitats include clear, well vegetated natural lakes, clear gravel-bottomed creeks, and wetlands,

including bogs, fens, and marshes. Such habitat diversity helps to explain why aquatic species diversity in Ecoregion

53 is naturally higher than in many other nearby ecoregions.

53a Rock River Drift Plain

The Rock River Drift Plain (53a) is principally composed of till and outwash plains. It is nearly level to

hilly, and is physiographically distinct from the hummocky, lake- and marsh-studded Kettle Moraines (53b). Stream

networks are better developed and more integrated in Ecoregion 53a than in the younger Kettle Moraines (53b). The

soils of the Rock River Drift Plain (53a) typically developed from glacial till, outwash deposits, loess, or alluvium;

in contrast, glacial deposits are generally absent from the neighboring Driftless Area (52).

In the early 19th century, oak savanna, prairie, and, on fire-protected dissected uplands and along water

courses, forest occurred (Kuchler, 1964; Neely and Heister, 1987, p. 28; Schwegman, 1973, p. 10-11).

Today, more than half of Ecoregion 53a is cropland; main crops are forage and feed grains supporting dairy

operations and livestock, but cash-grain farming is also important. Overall, cropland is much more common than in

Ecoregion 53b, but is less common than in the Rock River Hills (54g) or the Illinois/Indiana Prairies (54a).

53b Kettle Moraines

Ecoregion 53b is a poorly drained, hilly to hummocky morainal area that is characterized by many lakes,

conspicuous glacial landforms, and wetlands including bogs, fens, and marshes. Drainage networks are less integrated

and more poorly developed than on the older till and outwash plains of Ecoregion 53a. Lakes in Ecoregion 53b are

typically larger and more concentrated than to the south in the Valparaiso Morainal Complex (54f), and much more

common than in neighboring Ecoregions 53a, 54e, and 54a. Characteristically, soils are largely derived from thick lateWisconsinan glacial drift; loess deposits, if they occur, are thin. Alfisols are common, but Mollisols and Histosols also

occur (Natural Resources Conservation Service, various dates). Overall, organic soils are more extensive than

elsewhere in Illinois, and Mollisols are less common than in Ecoregions 53a and 54a.

In the early 19th century, moraines were covered by savanna, prairie, and especially, forest, whereas

depressions commonly contained wetlands (Vestal, 1931, p. 209; Schwegman, 1973, p. 12). Overall prairie was much

rarer than in neighboring Ecoregions 54a, 54e, and 54f.

Today, tracts of timber and nonforested wetlands remain, but there are many summer resorts and permanent

homes near lakes. Bogs in Illinois are limited to poorly drained depressions of the northeastern Valparaiso morainal

system, and include northern and eastern floristic elements (Schwegman, 1973, p. 11-13).

Ecoregion 53b tends to have a higher concentration of lakes with lower trophic states than in the rest of the

Ecoregion 53 (Omernik and others, 2000, p. 92). Some lakes, including Cedar, Channel, Grass, and Loon lakes,

contain a rich variety of native fish species. However, many other lakes contain introduced sport fishes (Smith,

1971, p. 5). The blue-spotted salamander is restricted to the morainic systems of northeastern Illinois (i.e.,

Ecoregions 53b and 54f) (Neely and Heister, 1987, p. 28). The banded killifish, blackchin shiner, and pugnose

shiner are now found exclusively in Ecoregion 53b (Illinois Natural History Survey, on-line resource); the former

two species are presently listed as threatened in the state, whereas the latter is endangered in Illinois (Illinois

Department of Natural Resources, on-line resource “b”).
8

54 CENTRAL CORN BELT PLAINS

Ecoregion 54 in Illinois is composed of vast glaciated plains that were once largely covered by prairies, but

that are now dominated by agriculture. Wisconsinan-age till is extensive; older, Illinoian-age, glacial deposits are

found in the west. Extensive, nearly level till, lake, and outwash plains with scattered sand sheets and dunes occur.

Dissection is greatest in the west on the Illinoian till plain portion of Ecoregion 54, where enough time has elapsed

since the Illinoian Glacial Stage to develop an integrated drainage network; overall, however, the Central Corn Belt

Plains (54) is less dissected than the Interior River Valleys and Hills (72). Concentric morainal ridges occur, and

become especially conspicuous in areas glaciated by Wisconsinan ice sheets.

In the early 19th century, level uplands were dominated by tall-grass prairie; no other level III ecoregion in

Illinois had as much prairie as Ecoregion 54 at the time of settlement (Neely and Heister, 1987, p. 28 and 30;

Schwegman, 1973, p. 14-15). Scattered groves of trees and marshes also occurred on level uplands, and river valleys

and moraines were mostly forested.

Dark, fertile soils are characteristic of the Central Corn Belt Plains (54) (Woods and others, 1998). Mollisols are

common, and contrast with the Alfisols that are common in neighboring ecoregions where forest was naturally more

extensive including the Driftless Area (52), Western Dissected Illinoian Till Plain (72i), Southern Illinoian Till Plain

(72j), and Kettle Moraines (53b) (Fehrenbacher and others, 1967, fig. 14; Horsley, 1986, fig. 5.6). Soils derived

from loess are found in the west over Illinoian till deposits; loess is thickest downwind of the major floodplains.

Soils derived primarily from drift are found in central and eastern areas on Wisconsinan till plains. Soils derived

from relatively recent deposits of till, loess, or alluvium are not strongly developed, lack claypans, and are richer in

minerals than older soils (Schwegman, 1973, p. 6).

In the early 19th century, poorly drained land, ponds, and swamps were common where morainal barriers, lowlying or flat land, or poorly developed drainage networks occurred (Nelson, 1978, p. 51). Subsequently, to make the

land more suitable for cropland and settlement, extensive parts of the Illinoian and Wisconsinan till plains in

Ecoregion 54 have been tiled, ditched, and tied into existing drainage systems. In so doing, once abundant aquatic

habitats have been modified, reduced in size, or eliminated, and nearly all of the original prairies have been replaced

by agriculture.

Today, cropland is extensive, and livestock farming is important. Main crops are corn and soybeans; cattle, sheep,

poultry, and, especially, hogs are raised, but are not as dominant as farther west in the drier Western Corn Belt Plains

(47) (Woods and others, 1998).

Agriculture has affected stream chemistry, turbidity, and habitat. Streams in the loess-mantled western part of

Ecoregion 54 are more turbid, and have less fish species diversity, than eastern areas (personal communication with

Mike Retzer, 2005).

54a Illinois/Indiana Prairies

The vast, glaciated, flat to rolling plains of Ecoregion 54a are characterized by dark, very fertile soils that

developed under tall-grass prairie; in addition, marshes and wet prairies naturally occurred in poorly drained areas,

and forests grew on concentric moraines and floodplains. Overall, at the time of settlement, trees were less common

than in the Southeastern Wisconsin Till Plains (53) and Interior River Valleys and Hills (72), and native vegetation

was distinct from the hardwood forests that covered the drift plains of Ecoregions 55 and 56 in Indiana

The soils of the Illinois/Indiana Prairies (54a) are typically rich in organic material, and developed from

loess, glacial drift, or lacustrine sediments. Soils derived from loess occur primarily in the west over Illinoian till

deposits; loess is thickest downwind of the major floodplains, and generally thins eastward (Fehrenbacher and

others, 1967, fig. 9). Younger soils derived primarily from Wisconsinan drift are found in central and eastern areas

on the Wisconsinan till plain; they lack the claypans that characterize many soils in the Southern Illinoian Till Plain

(72j) (Schwegman, 1973, p. 6). Mollisols are common and characteristic; they are distinct from the Alfisols that

dominate the Driftless Area (52), Western Dissected Illinoian Till Plain (72i), Southern Illinoian Till Plain (72j), and

Kettle Moraines (53b), where more extensive forests naturally occurred (Fehrenbacher and others, 1967, fig. 14;

Horsley, 1986, fig. 5.6).

At the time of settlement, poorly drained land, ponds, and swamps were common. Poor drainage was

especially pronounced in the youngest, most recently glaciated parts of the Wisconsinan till plain. However, even on

much older, more dissected till plains in the west where drainage systems are comparatively well integrated, many

lowlands between moraines were naturally wet or seasonally covered by standing water (Nelson, 1978, p. 42).

Subsequently, extensive parts of the Illinoian and Wisconsinan till plains have been tiled, ditched, and tied into the
9

existing drainage system to make the land more suitable for cropland and settlement. In the process, marshes and

pothole lakes were drained, and once abundant waterfowl were displaced (Schwegman, 1973, p. 14).

Nearly all of the original prairies have now been replaced by agriculture. Corn and soybeans are the main

crops; cattle, sheep, poultry, and, especially, hogs are also raised, but they are not as dominant as farther west in the

drier Western Corn Belt Plains (47) (Woods and others, 1998). Agriculture has affected stream chemistry, turbidity,

and habitat.

Western streams on the Illinoian till plain have fewer species, tend to dry up sooner during drought periods,

and have lower gradients, more clayey beds, and fewer gravel riffles than eastern streams on the Wisconsinan till

plain (personal communication with Roy Smoger, 2005). Similar macroinvertebrate assemblages occur in western

and eastern parts of Ecoregion 54a (personal communication with Mark Joseph, 2005).

54b Chicago Lake Plain

The Chicago Lake Plain (54b) lies between Lake Michigan and the Valparaiso Morainal Complex (54f),

and characteristically has a lake-modified climate. Ecoregion 54b is now dominated by the Chicago urban area, but,

originally, it was the bed of glacial Lake Chicago. Flat or nearly flat land is extensive, but paleo-beach ridges, sand

dunes, paleo-sand bars, paleo-spits, bluffs, and both morainal and bedrock ridges occur. Stream dissection and relief

are minimal, and natural drainage is typically poor. Soils are young, and were primarily derived from lacustrine

sediments, beach deposits, outwash material, and glacial till (Natural Resources Conservation Service, various

dates). Prairies, fens, and marshes were common at the time of settlement, and scrub-oak forests grew on sandy

ridges (Schwegman, 1973, p. 13-14). Today, nearly all of the natural vegetation has been replaced by urban

development.

The Chicago Lake Plain (54b) can be differentiated from neighboring inland areas by its lake-moderated

climate, unique terrain, physiographic history, present land use, and native beach-dune plant communities. The

Michigan Lake Plain (56d) has higher dunes, more woodlands, and less urban-industrial activity than Ecoregion

54b.

54c Kankakee Marsh

Prior to the 19th century, the nearly level plains and bottomlands of Ecoregion 54c were subject to

intermittent or permanent flooding, and were dominated by unique northern swamp forests containing pin oak, wet

prairies, and bulrush–cattail marshes (Fryxell, 1932, p. 26; Vestal, 1931; Woods and others, 1998). Natural drainage is

very poor. Since settlement, nearly all of Ecoregion 54c has been artificially drained and converted to agriculture; one

of the only remnants of natural vegetation that still remains is a narrow corridor of forested wetlands along the

Kankakee River (Woods and others, 1998). Much of the Kankakee River system has been straightened and deepened to

increase channel gradient and capacity (Fryxell, 1932, p. 26-27). Ditches are common. Corn, soybeans, and hay are

grown on artificially drained, sandy soils. Livestock farming also occurs.

54d Sand Area

Ecoregion 54d consists of disjunct, sandy outwash plains, and is distinguished from adjacent ecoregions by

its extensive sand plains, relict dunes, mix of natural vegetation, natural soil drainage properties, irrigation needs,

and stream characteristics. The Sand Area (54d) received vast amounts of medium textured glaciofluvial material

from melting glaciers. Before vegetation could establish itself, strong westerly winds formed discontinuous sand

dunes (Nelson, 1978, p. 45). Mixed oak savanna, scrub oak forests, and dry sand prairie then stabilized low dunes.

Dry sand prairie is native on sand sheets. Moister areas had mesic or wet prairies, whereas lowest, wettest sites were

covered by marshes (Schwegman, 1973, p. 13-16). Today, scrub forest remains on nutrient-poor, sandy, excessively

drained dune soils. Elsewhere, cropland and pastureland occur. Crops on sandy outwash plains require irrigation,

whereas drainage ditches are common in poorly drained areas.

The outwash deposits serve as aquifers. Plentiful, easily accessible ground water occurs in Ecoregion 54d,

and is an important local source for irrigation and for stream flow. As a result, streams in the Sand Area (54d)

generally have cooler summer stream temperatures and greater summer flow than in the Illinois/Indiana Prairies

(54a). Undisturbed streams are typically clear and well-vegetated, and have sand-bottomed pools, gravel riffles, and

a sand loving fish community; fishes like the least darter, ironcolor shiner, and weed shiner occur (personal

communication with Mike Retzer, 2005; Illinois Natural History Survey, on-line resource; Schwegman, 1973, p. 16;

Smith, 1971, p. 5); the ironcolor shiner is listed as threatened in Illinois, whereas the weed shiner is endangered in

the state (Illinois Department of Natural Resources, on-line resource “b”). Other streams and rivers, including the

Green River, have been highly modified, thereby degrading natural habitat (Nelson, 1978, p. 66; personal

communication with Mike Retzer, 2005).
10

54e Chiwaukee Prairie Region

The lake and till plains of Ecoregion 54e are found near the Lake Michigan shore, and contain beaches,

sand dunes, swales, low sandy beach ridges, and bluffs; physiography is distinct from the neighboring Valparaiso

Morainal Complex (54f) and Kettle Moraines (53b). Ecoregion 54e was once covered by distinctive tall-grass

prairies, scrub oak forests, fens, marshes, sand prairies, and sand savannas that supported a diverse fauna. Today,

cropland and residential, commercial, and industrial development dominate Ecoregion 54e; most of the natural

prairies are gone. Nonetheless, important recreation and conservation areas occur, including Illinois Beach State

Park, Illinois Beach Natural Area, and Illinois Dunes Natural Area. Ecoregion 54e is part of an important migratory

route for birds. Remaining marshes contain several species that are threatened or endangered in Illinois, such as the

marsh speedwell and the eastern prairie-fringed orchid; the latter is also listed as federally threatened species (Illinois

Department of Natural Resources, on-line resource “b”; Illinois Natural History Survey, on-line resource; U.S. Fish and

Wildlife Service, on-line resource). In Illinois, the common tern breeds in only a few places near Lake Michigan,

including Ecoregion 54e, and is listed as endangered in Illinois (Illinois Department of Natural Resources, on-line

resource “b”; Schwegman, 1973, p. 13).

54f Valparaiso-Wheaton Morainal Complex

Ecoregion 54f is a hilly, hummocky to rolling area containing moraines, kames, eskers, and outwash plains.

Characteristically, the Valparaiso Morainal Complex (54f) is studded with small lakes and marshes, and lacks a well

integrated drainage system. Lake size and density are less than in the physiographically similar Kettle Moraines

(53b), but are much greater than in the physiographically distinct Illinois/Indiana Prairies (54a) and Chicago Lake

Plain (54b). Soils are largely derived from thick, late-Wisconsinan glacial drift; loess deposits, if they occur at all, are

only thin. Alfisols are common; Mollisols also occur, but are less common than in Ecoregions 53a, 54a, 54b, and 54c.

In the early 19th century, prairie and forest dominated the moraines, and swamp white oak forests and

marshes occurred in poorly drained areas. Overall, prairie once covered slightly more than half of Ecoregion 54f.

Subsequent fire suppression has reduced the number of prairie openings, thereby increasing forest density

(Schwegman, 1973, p. 12).

Today, pastureland is common and, particularly in the east near Chicago, urban and suburban development

is accelerating. However, wooded areas, lakes, and wetlands are still common. The spotted turtle in Illinois is

restricted to the Valparaiso Morainal Complex (54f), and is listed as endangered in the state (Illinois Department of

Natural Resources, on-line resource “b”; Illinois Natural History Survey, on-line resource).

54g Rock River Hills

Ecoregion 54g is mostly composed of agriculturally dominated, rolling hills and undulating plains;

however, more rugged, partly forested ridges, ravines, and bluffs occur in the southeast and northwest. Physiography

is strongly influenced by the underlying limestone, dolomite, and sandstone; it is not significantly masked by the

region’s thin mantle of glacial till. Caves occur in limestone and dolomite. Most soils were derived from loess, but

other soils in major valleys typically developed from glacial outwash or alluvium, and still others were derived from

till or residuum (Natural Resources Conservation Service, various dates).

In the early 19th century, dry, shortgrass prairies characteristic of Ecoregion 52 were found on undulating

to rolling uplands, and transitioned into mesic prairies dominated by big bluestem and Indian grass. Dry or mesic

upland forests grew on ridge slopes and on fire-protected uplands, Canada yew–yellow birch forests grew on cool

bluffs and in ravines, and floodplain forests occurred on bottomlands (Schwegman, 1973, p. 14). Native flora is

influenced by bedrock, with several species confined to areas underlain by sandstone (Schwegman, 1973, p. 14).

Today, more than half of Ecoregion 54g is used as cropland; livestock farming is also important, and forest

remnants are largely confined to steep slopes and riparian areas. Main crops include corn, soybeans, and wheat.

Field tiles are normally used for drainage. Cropland is more common than in Ecoregions 52 and 53, but is much less

extensive than in the Illinois/Indiana Prairies (54a).
11

71 INTERIOR PLATEAU

In Illinois, Ecoregion 71 is composed of mostly forested, rugged hills that contain bluffs, ravines, and, in

the south, karst features. Crestal elevations, local relief, and forest density are greater, and land use is much

different, than in the broad, agriculturally-dominated plains of Ecoregion 72j to the north. Physiography, natural

drainage conditions, and native vegetation are all distinct from the Wabash–Ohio Bottomlands (72a). Soils are

primarily derived from loess and residuum of underlying sandstone, siltstone, shale, and limestone; on valley floors,

alluvial soils occur. Soils derived from glacial till are not typical or common in Ecoregion 71, in strong contrast to

the Central Corn Belt Plains (54) and Southern Illinoian Till Plain (72j) (Natural Resources Conservation Service,

various dates). However, thin, discontinuous till, deposited by Illinoian-age ice at its maximum extent, occurs in

some northernmost areas (Lineback, 1967). The potential natural vegetation of Ecoregion 71 in Illinois is oak–

hickory forest (Kuchler, 1964). Today, the Interior Plateau (71) in Illinois remains mostly forested, and National

Forest land is extensive. In addition, pastureland, hayland, limestone glades, and some cropland occurs.

71m Northern Shawnee Hills

The rugged, forested Northern Shawnee Hills (71m) ecoregion is composed of a high, south-facing

sandstone escarpment, as well as cliffs, bluffs, ravines, and canyons. It is underlain by massive Pennsylvanian

sandstone, siltstone, and shale, and is largely unglaciated. Ecoregion 71m is physiographically and lithologically

distinct from the lower, less rugged, carbonate-rich, Karstic Southern Shawnee Hills (71n).

Soils in Ecoregion 71m were largely derived from loess or residuum (Natural Resources Conservation

Service, various dates); they are not very productive because they have been leached of nutrients through time, lack

organic material, typically are steeply sloping, and often contain fragipans that impede internal drainage and

discourage root penetration (Nelson, 1978, p. 105; Schwegman, 1973, p. 27).

At the time of settlement, the Northern Shawnee Hills (71m) ecoregion was entirely forested; few if any

prairies occurred (McManis, 1964, p. 6).

Today, considerable forest remains, mostly within the Shawnee National Forest; pastureland, hayland, and

some cropland also occurs. Upland forests are typically dominated by white oak, black oak, and shagbark hickory.

Cool, shaded ravines support mesic forests composed of trees including red oak, beech and sugar maple, and contain

relict plant species with northern affinities (Neely and Heister, 1987, p. 31; Schwegman, 1973, p. 28). Floodplain

forests of bottomlands are dominated by sycamore, black walnut, Kentucky coffeetree, sugarberry, and honey locust.

High gradient, clear streams occur; pools typically have rock bottoms, and riffles have gravel bottoms.

Streams support several distinctive fishes including rock bass, black redhorse, banded sculpin, blackspotted

topminnow, spottail darter, and stripetail darter (Smith, 1971, p. 7; Schwegman, 1973, p. 28); in Illinois, the latter

three species are restricted to the southern part of the state (Illinois Natural History Survey, on-line resource).

Ecoregion 71m shares a number of fish species (mostly darters) with the Crawford–Mammoth Cave Uplands (71a)

in Kentucky (personal communication, 2005, Mike Retzer).

71n Southern Shawnee Hills

Ecoregion 71n is composed of hills that are mostly underlain by limestone and sandstone, and that are

characterized by karst. Caves, sinkhole plains, sinkhole ponds, and springs occur, and are especially common in

areas underlain by Mississippian Salem, St. Louis, and Ste. Genevieve limestones (Weibel and Panno, 1997).

Ecoregion 71n is both physiographically and lithologically distinct from the neighboring, higher, more rugged

Northern Shawnee Hills (71m).

At the time of settlement, the Southern Shawnee Hills (71n) ecoregion was mostly forested, but, unlike

Ecoregion 71m, limestone glades with dry prairies probably occurred (Schwegman, 1973, p. 27-28). The Southern

Shawnee Hills (71n) ecoregion contains flora from the Appalachian Mountains, Great Plains, Mississippi Alluvial

Plain, and Ozark Mountains (personal communication, 2005, Mike Retzer).

Today, many limestone glades and extensive forest remain, mostly within the Shawnee National Forest.

Pastureland, hayland, and some cropland also found in Ecoregion 71n, and are more common than in Ecoregion 71m.

Dry upland forests contain blackjack oak, post oak, scarlet oak, pignut hickory, and white oak. Cool, shaded ravines are

covered in mesic forests containing red oak, beech, and sugar maple (Schwegman, 1973, p. 27-28). Floodplain forests

are found in bottomlands. Limestone glades are dominated by little bluestem and side-oats grama, and contain southern

flora (Schwegman, 1973, p. 28).

Streams are typically clear, and are often fed by cold springs; pools have rock bottoms, and riffles have gravelly

bottoms (Smith, 1971, p. 7; Schwegman, 1973, p. 28). However, small intermittent streams that are not spring-fed also

occur (Smith, 1971, p. 7).
12

72 INTERIOR RIVER VALLEYS AND HILLS

Ecoregion 72 in Illinois is comprised of old till plains, hills, forested river bluffs, major rivers, and valleys

containing levees, oxbow lakes, islands, and scattered sand sheets and dunes. Ecoregion 72 is veneered by eastwardly

thinning loess (Fehrenbacher and others, 1967, fig. 9). Its wide, flat-bottomed valleys are filled with alluvium,

outwash, aeolian, or lacustrine deposits. Illinoian-age glacial deposits and land forms are extensive, but

Wisconsinan-age glacial deposits are absent in contrast to Ecoregion 54 (Lineback, 1979). Over half of the once flat

till plain has been strongly dissected since the retreat of ice; enough time has elapsed since the end of the Illinoian

Glacial Stage to form hills and integrate drainage systems in Ecoregion 72 (Fenneman, 1938, p. 510; McManis,

1964, p. 10; Nelson, 1978, p. 41-42).

The Interior River Valleys and Hills (72) ecoregion is a transitional area between the more forested Ozark

Highlands (39), and the flatter, less dissected, more extensively cropped, and much less forested Central Corn Belt

Plains (54). Within and between the major river systems of Ecoregion 72, considerable variability in water quality,

stream conditions, and aquatic biota occur, and fish species can be limited to certain river systems (Smith, 1971).

The potential natural vegetation of well-drained upland areas is a mosaic of oak–hickory forests and

bluestem prairies (Kuchler, 1964). At the time of settlement, forest was much more common in Ecoregion 72 than in

Ecoregion 54a. Prairies were discontinuous, but were usually found in undulating to rolling parts of Ecoregion 72

(McManis, 1964, p. 8-9); however, they were not nearly as extensive as in Ecoregion 54. Groves containing pin oak,

post oak, swamp white oak, and blackjack oak grew on flat to nearly level, poorly drained uplands with clay-rich

soils (Vestal, 1931, p. 214; Schwegman, 1973, p. 21). Beech–maple forests naturally occurred in mesic ravines

along the Vermilion River (Schwegman, 1973, p. 24). Bottomland hardwood forests and swamps are native on

poorly drained, nearly level sites along the major rivers.

Soils are mostly Alfisols that typically developed from several feet of loess; they contrast with the

Mollisols that dominate the Central Corn Belt Plains (54) (Fehrenbacher and others, 1967, fig. 9; Horsley, 1986, fig.

5.6). Claypans, which restrict root penetration and the movement of groundwater, occur in strongly developed soils,

and are associated with post oak flatwoods in south central Illinois (Schwegman, 1973, p. 5); they are not common

to the north in Ecoregion 54.

Today, less than half of Ecoregion 72 is in cropland, whereas about 30 percent is in pastureland, and the

remainder is in forest. Forests are now most commonly found on steeper slopes. Patterns of land use are more varied

in Ecoregion 72 than in adjacent ecoregions to the north, east, and west, where corn and soybean farming is

extensive (Chapman and others, 2002; Woods and others, 1998). Nearly all of the flat, cultivated uplands in

Ecoregion 72 have been tiled and tied into the stream system to improve drainage (Nelson, 1978, p. 51-52). Stream

water quality and aquatic habitat have been degraded or disturbed by ditching and draining, crop and livestock

production, sheet erosion from cultivated slopes, and strip mining.

In the Mississippi River system, turbidity, current, and volume all increase significantly downstream of its

junction with the Missouri River; resultant changes in the aquatic biota also occur, helping to differentiate the Upper

Mississippi Alluvial Plain (72d) from the Middle Mississippi Alluvial Plain (72e) (Chapman and others, 2002). Fish

communities also vary by stream system, helping to differentiate the Wabash–Ohio Bottomlands (72a) and Wabash

Lowlands (72b) from the Upper Mississippi Alluvial Plain (72d) and Middle Mississippi Alluvial Plain (72e)

(Smith, 1971); the bluebreast darter is found only in Ecoregion 72b and is endangered in Illinois, whereas the dusky

darter, greenside darter, mountain madtom, and river chub (endangered in Illinois) are limited to the Wabash-Ohio

river systems (Illinois Natural History Survey (on-line resource); Illinois Department of Natural Resources (on-line

resource “b”); Schwegman, 1973).

Ecoregions 72g and 72l act as the transition between the Interior River Valleys and Hills (72) and the

Ozark Highlands (39); they contain many Ozarkian and southern plants and animals that are rare or absent elsewhere

in Illinois (Neely and Heister, 1987, p. 30).
13

72a Wabash–Ohio Bottomlands

Ecoregion 72a is composed of poorly drained floodplains, low terraces, oxbow lakes, meander scars,

sloughs, and scattered low dunes, and was once covered by bottomland forests, wet and mesic prairies, marshes, and

swamps (Schwegman, 1973, p. 24; Vestal, 1931, p. 215). Bottomland forests contain pin oak, bur oak, Shumard oak,

swamp white oak, and other species with affinities to more southerly ecoregions (see Table 2). Wet and mesic

prairies were dominated by tall grasses, while marshes supported cord grass and river bulrush. Swamps dominated

by bald cypress and water tupelo were most common in the Cache River Basin. Physiography, natural drainage

conditions, and native vegetation are all distinct from nearby Ecoregions 71m, 71n, 72j, 72k, and 72m. Low gradient

streams with silt or sand bottoms occur, and are inhabited by Ohio River-type fish fauna (Woods and others, 2002).

Valley train deposits, alluvium, slackwater deposits, lacustrine deposits, and loess cover the area (Nelson,

1978, p. 59-60; Lineback, 1979). Outcrops of bedrock are rare, and never form cliffs like those that flank the Upper

Mississippi Alluvial Plain (72d) and the Middle Mississippi Alluvial Plain (72e) (Schwegman, 1973, p. 23).

Today, some woodlands, marshes, and swamps remain, but most have been cleared and drained for

agriculture. Land use is affected by seasonally high water tables and localized flooding. Soybeans, corn, and wheat

are the main crops, and livestock farming occurs. There are numerous oil and gas wells.

72b Glaciated Wabash Lowlands

Ecoregion 72b in Illinois is a till plain that is dissected by rugged, forested ravines. Alfisols and Mollisols

occur and were derived from loess, glacial till, or alluvium. In the early 19th century, prairie and dry upland forest

occurred on undulating to rolling till plains, floodplain forests grew on bottomlands, and beech–maple forests were

found in ravines flanking the Vermilion River and its tributaries (Schwegman, 1973, p. 24). Native beech–maple

forests are a characteristic of the Glaciated Wabash Lowlands (72b) in Illinois; at the time of settlement, beech–

maple forests were extensive in Indiana and Ohio, but they protruded only slightly into Illinois along the Vermilion

River (Woods and others, 1998; Schwegman, 1973, p. 24). Today, nearly all of the level upland areas have been

cleared for cropland and pastureland, but forests remain in steep ravines (Illinois Department of Natural Resources,

on-line resource “a”). Main crops are corn, soybeans, wheat, and hay (National Agricultural Statistics Service, 1997).

Surface mining of coal has been extensive.

72d Upper Mississippi Alluvial Plain

Ecoregion 72d encompasses the broad floodplains and low river terraces of the Mississippi River and its major

tributaries above the Mississippi’s confluence with the Missouri River, including much of the Illinois River. Levees,

oxbow lakes, islands, and scattered sand sheets and dunes occur. Soils were mostly derived from thick, silty and clayey

alluvium, and are usually poorly drained. Others soils developed from sandy outwash. Both the alluvial plain and the

river channel have been heavily modified in the last 100 years.

Prior to the 19th century, bottomland forests, prairies, and marshes were common. Bottomland forests were

adapted to prolonged flooding, and dominated by silver maple, American elm, and green ash (Schwegman, 1973, p.

17); fewer tree species occurred than in the bottomlands of the Upper Mississippi Alluvial Plain (72d) than in the

Middle Mississippi Alluvial Plain (72e) (Schwegman, 1973, p. 26). Mesic and wet prairies occurred on wide

bottomlands, and dry prairie grew on the sand sheets (Schwegman, 1973, p. 17-18).

Today, the natural vegetation has largely been replaced by agriculture. Corn and soybeans are the major

crops. Long reaches of the Mississippi River have been channelized, and many low dams with locks have been

constructed upstream of St. Louis. Turbidity, current, and volume in the Mississippi River increase abruptly at its

confluence with the Missouri River (Chapman and others, 2002). Resultant changes in the aquatic biota occur, and

help to differentiate the Upper Mississippi Alluvial Plain (72d) from the Middle Mississippi Alluvial Plain (72e). The

Mississippi River in Ecoregion 72d lacks distinctive, silt-tolerant, fish species that characteristically occur

downstream in the more turbid waters of Ecoregion 72e (Schwegman, 1973, p. 26).
14

72e Middle Mississippi Alluvial Plain

Ecoregion 72e encompasses the floodplains and low river terraces of the Mississippi River from its

confluence with the Missouri River to Thebes Gorge, just north of the Ohio River. Bottomlands are broad, and were

formed by glacial flood waters (Schwegman, 1973, p. 26). Levees, meander scars, oxbow lakes, islands, spring-fed

swamps, and sloughs occur. Both the alluvial plain and the river channel have been significantly modified in the last

century by human activities.

Prior to settlement, bottomland forests, prairies, marshes, and, in the south, bottomland swamps were

common in the Middle Mississippi Alluvial Plain (72e). Its bottomland forests were adapted to prolonged flooding,

and contained a few southern lowland species; more tree species naturally occurred in Ecoregion 72e than in the

Upper Mississippi Alluvial Plain (72d) (Schwegman, 1973, p. 26-27).

Today, nearly all of the original prairies, marshes, swamps, and forests have been drained and converted to

cropland or pastureland. Soybeans, corn, and wheat are the main crops.

Turbidity, current, and volume in the Mississippi River increase abruptly at its confluence with the Missouri

River (Chapman and others, 2002). Resultant changes in the aquatic biota occur, and help to differentiate the Middle

Mississippi Alluvial Plain (72e) from the Upper Mississippi Alluvial Plain (72d). Ecoregion 72e contains a distinctive

fish assemblage of silt-tolerant plains species that are not found upstream in Ecoregion 72d (Schwegman, 1973, p.

26). Several species of fish have not been found elsewhere in Illinois, including the flathead chub, sicklefin chub,

sturgeon chub, plains minnow, and the Alabama shad; the bantam sunfish, listed as threatened in Illinois, is

restricted to spring-fed swamps such as those that occur in Ecoregion 72e (Illinois Natural History Survey, on-line

resource; Schwegman, 1973, p. 26).

72f River Hills

The dissected and forested hills, bluffs, cliffs, and ravines of Ecoregion 72f flank the floodplains of the

Mississippi, Illinois, and lower Sangamon rivers in west central Illinois. Ecoregion 72f is characteristically underlain

by limestone and sandstone, and is deeply covered by loess (Fehrenbacher and others, 1967, fig. 9, Schwegman,

1973, p. 24). Most of Ecoregion 72f was glaciated by pre-Wisconsinan ice (Lineback, 1979). Areas of karst occur,

and are most abundant in unglaciated areas of Ecoregion 72f in Calhoun County (Weibel and Panno, 1997).

Sugar maple, basswood, and red oak are common on mesic sites, whereas black and white oaks occur on

drier sites, and post oak is found near ridge tops. Floodplain forests grow on bottomlands, and are dominated by

silver maple, cottonwood, hickories, and sycamore. Ecoregion 72f is part of an extensively forested habitat corridor

along the Mississippi River. Wooded valleys in Ecoregion 72f are important nighttime roosting areas for wintering

bald eagles (Neely and Heister, 1987, p. 30).

72g Southern Ozarkian River Bluffs

Ecoregion 72g is composed of rugged, loess-capped bluffs and ravines that flank the Mississippi River in

southwestern Illinois. It is part of a nearly continuous, forested river corridor that promotes the northward dispersal

of southern fauna.

Today, considerable forest remains in Ecoregion 72g, mostly within the Shawnee National Forest;

prevailing land use and associated environmental issues are distinct from those in nearby, agriculturally-dominated

regions such as the Middle Mississippi Alluvial Plain (72e). Scattered loess hill prairie occurs on bluff tops and

some slopes, but is much less common than in Ecoregion 72l (Schwegman, 1973, p. 25). The upland forests of

Ecoregion 72g are species-rich, and contain oaks, sugar maple, bitternut hickory, and basswood. Floodplain forests

contain American elm, cottonwood, white oak, red oak, sycamore, and river birch. Plants adapted to acidic soil,

including shortleaf pine and azalea, are found on steep, cherty slopes; they are absent from Ecoregion 72l, where

acidic soils are generally lacking (Schwegman, 1973, p. 6).

The Southern Ozarkian River Bluffs (72g) is underlain by Paleozoic cherty limestone that is more resistant

to erosion and groundwater solution than the limestone of the Karstic Northern Ozarkian River Bluffs (72l); as a

result, Ecoregion 72g is more rugged, has more surface drainage, and has much less karst than Ecoregion 72l

(Schwegman, 1973, p. 24). Soils in Ecoregion 72g are usually Alfisols. they developed from thick loess on bluff

tops, and thin loess, acidic residuum, or colluvium on steep slopes (Natural Resources Conservation Service, various

dates). Ecoregion 72g is driftless unlike Ecoregion 72l which is partly mantled by Illinoian till (Lineback, 1979).

Distinctive amphibian and reptile species occur, and are characterized by Ozarkian and southern flora that

are absent from the River Hills (72f) (Schwegman, 1973, p. 24; Smith, 1961, p. 12-13). In Illinois, the scarlet snake is

known to occur only in Ecoregion 72g, and the spring cavefish is limited to a few areas in southern Illinois including

Ecoregion 72g. The flat-headed snake is listed as threatened in Illinois, and occurs in both Ecoregions 72 and 72g; it

is found nowhere else in the state (Schwegman, 1973, p. 25; Illinois Natural History Survey, on-line resource).
15

72i Western Dissected Illinoian Till Plain

Ecoregion 72i is a well dissected, pre-Wisconsinan till plain with broad, nearly level interfluves, and many

forested slopes, ravines, and floodplains. It is generally more dissected and forested than the Illinois/Indiana Prairies

(54a), and is physiographically distinct from the broad flats and hills of the Southern Illinoian Till Plain (72j). The

Western Dissected Illinoian Till Plain (72i) is capped with loess and till, and is underlain by Pennsylvanian and

Mississippian limestone, sandstone, shale, and coal; outcrops are common in valleys and ravines (Schwegman, 1973,

p. 19). Alfisols are common, and are low in organic matter, acidic, and well-drained. Mollisols also occur, but are

less extensive than in Ecoregion 54a; they developed in thick loess (Natural Resources Conservation Service,

various dates).

In the early 19th century, oak–hickory forests covered well-drained slopes, whereas more mesic sites

supported white oak, red oak, and basswood (Schwegman, 1973, p. 19). Prairies were found on nearly level

interfluves (Nelson, 1978, p. 104). Marshes and wet prairie also occurred, but were less common than in the Central

Corn Belt Plains (54).

Today, cropland and pastureland have almost entirely replaced the native prairies; corn and soybeans are

the main crops. Steep slopes and ravines remain largely wooded, but forested acreage is less than it was at the time

of settlement. Artificial drainage is less extensive than in neighboring Ecoregions 54a; partially as a result, nitrate

concentrations in the surface waters of Ecoregion 72i tend to be lower than in Ecoregion 54a (personal

communication, 2005, Charles Pederson). Sheet erosion can be severe on cultivated slopes.

72j Southern Illinoian Till Plain

Ecoregion 72j is a partly dissected till plain that was once covered by forests and prairies. Broad flats,

rolling hills, and subdued moraines are common. Towards the south, the terrain becomes more hilly as glacial till

thins and bedrock approaches the surface (Nelson, 1978, p. 42; Schwegman, 1973, p. 21). Overall, dissection is

greater, moraines are less prominent, and forests are naturally more extensive than in the Illinois/Indiana Prairies

(54a). Ecoregion 72j is physiographically different from the Western Dissected Illinoian Till Plain (72i). The

underlying Paleozoic sandstone, limestone, coal, and shale is mantled by loess and Illinoian-age glacial till; younger

Wisconsinan-age till is absent, in contrast to Ecoregion (54) where it is extensive (Lineback, 1979; Kolata, 2005).

Upland soils in the Southern Illinoian Till Plain (72j) are clayey or silty, derived from loess and till, and have poor

internal drainage. Impervious fragipans or claypans are common and characteristic. Soils are droughty during dry

periods, excessively wet during the spring, and acidic (Natural Resources Conservation Service, various dates;

Nelson, 1978, p. 105; Schwegman, 1973, p. 21). Claypans are much more common, and natural drainage is poorer,

than in the Western Dissected Illinoian Till Plain (72i). Overall soil quality and productivity are lower than in the

Central Corn Belt Plains (54) (Mausel, 1970, p. 135).

In the early 19th century, about 40% of the well-drained uplands in Ecoregion 72j were covered by prairies.

The remaining uplands were covered by scattered trees, groves, and forests (Schwegman, 1973, p. 22). Groves

containing pin oak, post oak, swamp white oak, and blackjack oak are native to nearly level, poorly drained uplands

with clay-rich soils. Oak–hickory forests occurred on relatively dry valley slopes. Mesic forests containing red oak,

elm, basswood, and walnut dominated low morainal ridges (Vestal, 1931, p. 214-215).

Today, nearly all of the original prairies in Ecoregion 72j, and most of its original forests (especially in the

south) have been converted to agriculture. Soybeans, corn, and wheat are the primary crops, and livestock farming is

important. Forests are now largely confined to side slopes and river bottoms that are unsuitable for farming. Natural

soil wetness conditions in Ecoregion 72j are generally unfavorable for crops, and, therefore, nearly all of the

ecoregion’s flat and nearly level uplands have been tiled to improve drainage. Soybeans are better adapted to

drought than corn, and can mature even when spring planting is delayed by field wetness; as a result, soybean

acreage exceeds that of corn in the Southern Illinoian Till Plain (72j) (Nelson, 1978, p. 105; National Agricultural

Statistics Service, 1997). Sheet erosion can be severe on cultivated slopes.

The northern crayfish frog, eastern fence lizard, ground skink, and broadheaded skink are common in the

Southern Illinoian Till Plain (72j), but are rare in the Illinois/Indiana Prairies (54a) (Illinois Natural History Survey,

on-line resource). Sanctuaries providing nesting habitat for the greater prairie chicken, listed as endangered in

Illinois, have been established in Ecoregion 72j (Illinois Department of Natural Resources, on-line resource “b”;

Schwegman, 1973, p. 22).
16

72k Cretaceous Hills

Ecoregion 72k is composed of unglaciated, steep to rolling hills that are characteristically underlain by

unconsolidated sands, gravels, and clays of Cretaceous- and Tertiary-age. The Cretaceous Hills (72k) is

lithologically distinct from other ecoregions in Illinois. Upland soils are derived from loess and, locally, from

unconsolidated sediments (Schwegman, 1973, p. 28-29).

In the early 19th century, forests containing upland oaks, black gum, hickories, and tuliptree, were common.

Mesic prairies occurred locally on wide stream bottoms, and dry prairies were found on eastern uplands (Schwegman,

1973, p. 29).

Today, steeper slopes remain mostly wooded. Elsewhere, the land has been converted to livestock farms,

general farms, and cropland growing corn, wheat, hay, and soybeans.

The range of the spotted dusky salamander in Illinois, listed as endangered in the state, is largely restricted

to Ecoregion 72k (Illinois Department of Natural Resources, on-line resource “b”; Illinois Natural History Survey, online resource).

72l Karstic Northern Ozarkian River Bluffs

Ecoregion 72l includes loess-mantled Mississippi River bluffs, ravines, and karst features that developed on

underlying limestone; nowhere else in Illinois are there as many sinkholes, sinkhole ponds, and caves (Weibel and

Panno, 1997). Ozarkian limestone glade flora, well developed karst, and distinctive amphibian and reptile

assemblages characterize the ecoregion.

The Karstic Northern Ozarkian River Bluffs (72l) is underlain by Mississippian limestone that is less

resistant to erosion and groundwater solution than the cherty limestone of the neighboring Southern Ozarkian River

Bluffs (72g); as a result, Ecoregion 72l has less rugged topography, better developed karst, and less surface drainage

than Ecoregion 72g (Schwegman, 1973, p. 24).

Soils are typically Alfisols. They developed from thick loess on bluff tops, and from thin loess, colluvium,

or residuum on steep slopes (Natural Resources Conservation Service, various dates).

Potential natural vegetation is mostly oak–hickory forest (Kuchler, 1964); in addition, loess hill prairies

were once common on loess-covered bluff tops and steep slopes in Ecoregion 72l, but were rare in neighboring

Ecoregion 72g. The native flora includes a distinctive assemblage of Ozarkian limestone glade species; Ozarkian

flora is absent from the River Hills (72f) to the north (Schwegman, 1973, p. 25).

Today, steeper slopes remain mostly wooded. Elsewhere, the land has been converted to pastureland and

cropland; corn, wheat, soybeans, and hay are the main crops. Apple and peach orchards occur.

Ecoregion 72l is a part of an important, forested habitat corridor along the Mississippi River. The

coachwhip, a snake listed as endangered in Illinois, is restricted to Ecoregion 72l (Illinois Department of Natural

Resources, on-line resource “b”; Illinois Natural History Survey, on-line resource). The flat-headed snake is listed as

threatened in Illinois, and occurs in both the Karstic Northern Ozarkian River Bluffs (72l) and the Southern

Ozarkian River Bluffs (72g); it is found nowhere else in the state (Schwegman, 1973, p. 25; Illinois Natural History

Survey, on-line resource).

72m Wabash River Bluffs and Low Hills

Ecoregion 72m is composed of partly forested, low bluffs along the Wabash River. Alfisols are common,

and are characteristically derived from thick loess (Natural Resources Conservation Service, various dates).

Ecoregion 72m is lower, less rugged, and less wooded than the hills and bluffs along the Mississippi River in

Ecoregions 72f, 72l, and 72g, but more wooded, rugged, and deeply loess-covered than Ecoregions 72a and 72j.

In the early 19th century, dry upland forests (dominated by black oak and hickories), mesic upland forests

(dominated by white oak, red oak, and sugar maple), floodplain forests, and mesic prairies occurred in Ecoregion

72m (Schwegman, 1973, p. 23).

Today, forests are still common in Ecoregion 72m on steeper slopes and in ravines; flatter areas are

cultivated. Main crops are corn, wheat, soybeans, and hay.
17

73 MISSISSIPPI ALLUVIAL PLAIN

Ecoregion 73 is a nearly flat, alluvial plain that extends along the Mississippi River from southern Illinois

to the Gulf of Mexico. Temperature and precipitation increase from north to south. Bottomland deciduous forests

and bottomland swamps largely covered Ecoregion 73 in Illinois before they were cleared for cultivation

(Schwegman, 1973, p. 29). Cropland is now widespread, and livestock farming occurs; soybeans, corn, and wheat

are the main crops.

73a Northern Holocene Meander Belts

Ecoregion 73a encompasses the broad, flat to nearly flat floodplains, low terraces, islands, and meander

belts of the Mississippi River that occur downstream of Thebes Gorge, near the confluence of the Mississippi and

Ohio rivers. Swales, abandoned channels, oxbow lakes, sloughs, natural levees, and point bars occur. Ecoregion 73a

was never glaciated, but, instead, was heavily influenced by flood waters from melting glaciers to the north. Soils

are derived from Recent alluvium, and are naturally fertile; they are generally clay-rich except along the rivers.

Potential natural vegetation is southern floodplain forest; it is distinct from the oak–hickory forest of nearby upland

Ecoregions 71n, 72k, and 72q (Kuchler, 1964). At the time of settlement, Ecoregion 73a was mostly covered by

bottomland deciduous forests and, on frequently flooded sites, by bottomland swamps (Schwegman, 1973, p. 29).

Natural vegetation includes southern species that are at or near their northern distributional limit, including bald

cypress and tupelo gum (Woods and others, 2002).

Today, most of the forests and swamps in Ecoregion 73a in Illinois have been cleared and drained for

agriculture (Illinois Department of Natural Resources, on-line resource “a”). Cropland is now widespread, and livestock

farming occurs; soybeans, corn, and wheat are the main crops (National Agricultural Statistics Service, 1997). Only

scattered remnants of bottomland forests and bottomland swamps still occur, and they are largely confined to

islands, oxbows, the insides of levees, and, especially, conservation areas. Undrained areas are typically subject to

seasonal flooding.
18

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22

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23

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Indiana and Ohio (2-sided color poster with map, descriptive text, summary tables, and photographs): Reston,

Virginia, U.S. Geological Survey, scale 1:500,000.

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2005, Ecoregions of Oklahoma (color poster with map, descriptive text, summary tables, and photographs):

Reston, Virginia, U.S. Geological Survey (scale 1:1,250,000).

Woods, A.J., Omernik, J.M., Martin, W.H., Pond, G.J., Andrews, W.M., Call, S.M., Comstock, J.A., and Taylor.

D.D., 2002, Ecoregions of Kentucky. (2-sided color poster with map, descriptive text, summary tables, and

photographs): Reston, Virginia, U.S. Geological Survey, scale 1:1,000,000.

Wright, H.E., Jr., 1968, History of the prairie peninsula in Bergstrom, R.E., editor, The Quaternary of Illinois:

University of Illinois College of Agriculture Special Publication 14, p. 78-88.

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Davis, W.S., and Simon, T.P. (eds.), Biological assessment and criteria, tools for water resource planning and

decision making: Boca Raton, Florida, Lewis Publishers, p. 109-144.

PROJECT FUNDING

This project to refine existing EPA level III ecoregions in Illinois and subdivide them into level IV ecoregions

was partly conducted under the auspices of the Program for Cooperative Research on Aquatic Indicators Award # CR831682-01.

PEER REVIEWERS

Chris Lant, Professor (Executive Director of Universities Council on Water Resources, Co-director of the

Environmental Resources and Policy Program), Department of Geography, Southern Illinois University; Andy

Rorick, Geologist, U.S. Forest Service; Michael Sublett, Professor, Department of Geography-Geology, Illinois

State University.
24

TABLE 1: COMMON AND SCIENTIFIC NAMES CITED IN TEXT

AMPHIBIANS AND REPTILES

Blue-spotted salamander Ambystoma laterale

Broadheaded skink Eumeces laticep

Coachwhip Masticophis flagellum

Spotted dusky salamander Desmognathus conanti

Eastern fence lizard Sceloporus undulatus

Ground skink Scincella laterali

Northern crayfish frog Rana areolata

Flat-headed snake Tantilla gracilis

Scarlet snake Cemophora coccinea

Spotted turtle Clemmys guttata

BIRDS

Common tern Sterna hirundo

Greater prairie chicken Tympanuchus cupido

FISH

Alabama shad Alosa alabamae

Banded killifish Fundulus diaphanus

Banded sculpin Cottus carolinae

Bantam sunfish Lepomis symmetricus

Blackchin shiner Notropis heterodon

Black redhorse Moxostoma duquesnei

Bluebreast darter Etheostoma camuru

Blackspotted topminnow Fundulus olivaceus

Cypress darter Etheostoma proeliare

Flathead chub Platygobio gracilis

Greenside darter Etheostoma blennioides

Harlequin darter Etheostoma histrio

Ironcolor shiner Notropis chalybaeus

Least darter Etheostoma microperca

Mountain madtom Noturus eleutherus

Plains minnow Hybognathus placitus

Pugnose shiner Notropis anogenus

River chub Nocomis micropogon

River redhorse Moxostoma carinatum

Rock bass Ambloplites rupestris

Sicklefin chub Macrhybopsis meeki

Small mouth bass Micropterus dolomieu

Spottail darter Etheostoma squamiceps

Spring cavefish Forbesichthys agassizi

Stripetail darter Etheostoma kennicotti

Sturgeon chub Macrhybopsis gelida

Weed shiner Notropis texanus
2

5

VEGETATION

AmericanelmUlmusamericana

AmericanlotusNelumbolutea

BaldcypressTaxodiumdistichum

BasswoodTiliaamericana

BeechFagusgrandifolia

BigbluestemAndropogongerardii

BitternuthickoryCaryacordiformis

BlackcherryPrunusserotina

BlackgumNyssasylvatica

BlackjackoakQuercusmarilandica

BlackoakQuercusvelutina

BlackwalnutJuglansnigra

BlackwillowSalixnigra

BlueberryVacciniumspp.

BluejointgrassCalamagrostiscanadensis

BoxelderAcernegundo

BulrushScirpusspp.

BuroakQuercusmacrocarpa

CanadayewTaxuscanadensis

CatalpaCatalpaspeciosa

CattailTyphalatifolia

CherrybarkoakQuercuspagoda

CinnamonfernOsmundacinnamomea

CommonreedPhragmitescommunis

CottonwoodPopulusdeltoides

CranberryOxycoccusmacrocarpus

CucumbertreeMagnoliaacuminata

Drummond’sredmapleAcerrubrumvar.drummondii

DwarfbirchBetulapumila

Easternprairie-fringedorchidPlatantheraleucophaea

FallwitchgrassLeptolomacognatum

GamagrassTripsacumdactyloides

GreenashFraxinuspennsylvanica

HackberryCeltisoccidentalis

Heart-leavedtragiaTragiacordata

HoneylocustGleditsiatriacanthos

IndiangrassSorghastrumnutans

JunegrassKoeleriacristata

KentuckycoffeetreeGymnocladusdioica

KingnuthickoryCaryalaciniosa

LadyfernAthyriumfilix-femina

LeatherleafChamaedaphnecalyculata

LittlebluestemSchizachyriumscoparium

MarshspeedwellVeronicascutellata

MockernuthickoryCaryatomentosa

OhiobuckeyeAesculusglabra

OvercupoakQuercuslyrata

PecanCaryaillinoensis

PignuthickoryCaryaglabra

PickerelweedPontederiacordata

PinoakQuercuspalustris

PitcherplantSarraceniapurpurea

PostoakQuercusstellata

PlainsbuttercupRanunculusrhomboideus

PorcupinegrassStipaspartea
26

VEGETATION (continued)

Prairie cord grass Spartina pectinata

Prairie dropseed Sporobolus heterolepis

Pumpkin ash Fraxinus profunda

Red buckeye Aesculus pavia

Red oak Quercus rubra

River bulrush Scirpus fluviatilis

Royal fern Osmunda regalis

Sand dropseed Sporobolus cryptandrus

Scarlet oak Quercus coccinea

Sedge Cyperaceae (various species)

Shagbark hickory Carya ovata

Shingle oak Quercus imbricaria

Shortleaf pine Pinus echinata

Shumard oak Quercus shumardii

Side-oats grama Bouteloua curtipendula

Silver maple Acer saccharinum

Slippery elm Ulmus rubra

Sphagnum moss Sphagnum spp.

Sugarberry Celtis laevigata

Sugar maple Acer saccharum

Sundew Drosera spp.

Swamp chestnut oak Quercus michauxii

Swamp cottonwood Populus heterophylla

Swamp white oak Quercus bicolor

Sweet gum Liquidambar styraciflua

Switch grass Panicum virgatum

Sycamore Platanus occidentalis

Tamarack Latrix laricina

Tuliptree Liriodendron tulipifera

Tupelo gum Nyssa aquatica

Water locust Gleditsia aquatica

White ash Fraxinus americana

White birch Betula papyrifera

Wild blue sage Salvia azurea

White oak Quercus alba

White pine Pinus strobus

Winterberry Ilex verticillata

Yellow birch Betula alleghaniensis
27

TABLE 2: SUMMARY TABLE – CHARACTERISTICS OF THE ECOREGIONS OF ILLINOIS

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

52a.

Savanna

Section

283 Hills dominated by broad ridge tops;

flat plateau remnants and high,

mound-like erosional remnants

occur. Valley bottoms are narrow.

Cool, clear, perennial, spring-fed

streams and a few caves occur.

800-1257/

100-250

Thin to thick Quaternary loess,

dolomitic limestone residuum,

and calcareous shale residuum.

Loess depth is commonly 100

to 200 inches. Ordovician and

Silurian limestone, dolomite,

and shale. Mounds are capped

with resistant dolomite.

Uplands: Mostly

Alfisols (Hapludalfs);

also Mollisols

(Hapludolls).

Floodplains and low

terraces: Entisols

(Fluvaquents,

Udifluvents).

On uplands: Fayette, Palsgrove, Dubuque,

Lacrescent, Rozetta, Eleroy, Newglarus,

Lamoille. Upland soils are derived from

loess or residuum, not from glacial till,

and are well-drained. On floodplains and

low terraces: Wakeland, Dorchester.

52b.

Paleozoic

Plateau/

Coulees

Section

363 Rugged, deeply dissected plateau.

Hills, loess-capped river bluffs,

canyons, ravines, and valleys occur,

along with a few caves and springs.

Includes the Niagaran Escarpment;

north-facing slopes of the

escarpment are steeper than southfacing slopes which are cut by

narrow valleys that deepen with

increasing distance from the crest of

the escarpment. Cool, clear,

perennial, spring-fed streams occur.

600-1100/

200-475

Thin to thick Quaternary loess

and dolomitic limestone

residuum. Commonly, loess is

200 to 300 inches thick on hills

and bluffs along the Mississippi

River. Silurian and Ordovician

limestone, dolomite, and shale.

Bedrock outcrops are common

along the major water courses.

Uplands: Mostly

Alfisols (Hapludalfs);

also, Mollisols

(Hapludolls).

Floodplains and low

terraces: Entisols

(Fluvaquents,

Udifluvents) and

Alfisols (Albaqualfs).

On uplands: Fayette, Dubuque, Lamont,

Palsgrove, Sparta. Upland soils are

derived from loess or residuum, not from

glacial till, and are well-drained. On

floodplains and low terraces: Wakeland,

Dorchester, Zwingle.
28

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

52a.

Savanna

Section

Mesic/

Udic, Aquic

34-36/

155-160

5-27/

56-84

Potential natural vegetation: bluestem prairie and maple–

basswood forest. On rolling uplands: in the early 19th century,

dry to mesic prairies often dominated by little bluestem and

side-oats grama (contained northern Great Plains plant species

including plains buttercup, and June grass) and oak savanna.

On mesic hill slopes: upland hardwood forest dominated by

sugar maple, basswood, and red oak. On drier sites: white oak

on thin, droughty, clayey residual soils, and black oak on

ridge tops and rocky cliffs. On cliffs along major streams:

white pine, Canada yew, and white (i.e., canoe) birch. On

floodplains: forests dominated by silver maple, American elm,

and green ash.

Agriculture is found on the uplands, mixed

woodland-agriculture occurs in lowland

areas, and forests are found on steep slopes

and along streams. Pastureland is

common, mixed farms and dairies occur,

and woodlots are found in steepest areas.

Principal crops are feed grains and forage

for dairy cattle and other livestock.

52b.

Paleozoic

Plateau/

Coulees

Section

Mesic/

Udic, Aquic

34-36/

160

4-28/

60-84

Potential natural vegetation: maple–basswood forest. On

mesic upland sites: upland hardwood forest dominated by

sugar maple, basswood, and red oak. On drier sites: upland

hardwood forest dominated by black oak and white oak. On

cliffs and in shaded ravines: white pine, Canada yew, and

white (i.e., canoe) birch. On steep, southwesterly facing bluffs

above the Mississippi River floodplain: loess hill prairies

dominated by little bluestem and side-oats grama. On

floodplains: forests dominated by silver maple, American elm,

and green ash.

Mostly forest, with agriculture largely

confined to level and gently sloping

lowlands and hilltops. Canyons and steeper

slopes are forested. The decommissioned

Savanna Army Depot covers about 13,000

acres, and supports 32 endangered or

threatened plants and animals.

Approximately 9,400 acres have or will be

transferred to the U.S. Fish and Wildlife

Service’s Upper Mississippi River

Wildlife and Fish Refuge.
29

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

53a.

Rock

River

Drift Plain

609 Glaciated, nearly level to hilly till

plains and outwash plains. Broad

valleys occur.

700-1100/

50-250

Quaternary glacial till, outwash

deposits, thin to thick loess,

residuum, and alluvium.

Ordovician dolomite,

limestone, and shale.

Uplands: Alfisols

(Hapludalfs) and

Mollisols

(Argiudolls).

Floodplains and low

stream terraces:

Mollisols

(Endoaquolls,

Argiudolls).

On uplands: Flagg, Tama, Pecatonica,

Fayette, Ogle, Palsgrove, Ashdale,

Edmund, Rockton. On floodplains and low

stream terraces: Flagler, Warsaw,

Comfrey, Selma.

53b.

Kettle

Moraines

680 Glaciated, hummocky to hilly area

with steeply sloping moraines,

outwash plains, closed depressions,

mounds, level areas, and many

wetlands and natural lakes. The

drainage network is not well

integrated.

675-1050/

less than

50-150

Wisconsinan-age glacial till,

outwash gravels, and thin loess

(less than 20 inches). Silurian

and Ordovician dolomite,

limestone, and shale.

Mostly Alfisols

(Hapludalfs,

Epiaqualfs); also,

Mollisols (Argiudolls,

Endoaquolls),

Histosols

(Haplosaprists).

Morley, Markham, Elliott, Houghton,

Nappanee, Ashkum, Marsh, Fox, Beecher,

Corwin, Miami, Montmorenci, Boyer,

Montgomery, Zurich, Odell, Grays,

Littleton, Proctor. Poorly drained, organic

soils are common in closed depressions.
30

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

53a.

Rock

River

Drift Plain

Mesic/

Udic, Aquic

35-38/

156-160

9-27/

60-83

Potential natural vegetation: bluestem prairie, maple–

basswood forest, and oak savanna. On level and rolling

uplands: dry prairies (dominants: little bluestem and side-oats

grama), mesic prairie (dominants: big bluestem, Indian grass,

and prairie dropseed), and wet prairie (dominants: prairie cord

grass, bluejoint grass, and big bluestem). In the early 19th

century, forest was abundant in more dissected upland areas

and along water courses. On fire protected slopes of dissected

uplands: dry upland forests (dominants: black oak, white oak,

bur oak, and black cherry) and mesic upland forests

(dominants: sugar maple, basswood, slippery elm, and red

oak). On bottomlands: floodplain forests (dominants: silver

maple, black willow, cottonwood, American elm, and green

ash).

Cropland, pastureland, and woodlots.

More than half is used as cropland. Forage

and feed grains for dairy operations and

livestock farms are the primary land uses;

cash-grain farming is also an important

activity. Corn and soybeans are the main

crops.

53b. Kettle

Moraines

Mesic/

Udic, Aquic

35-38/

160-170

11-28/

61-83

Potential natural vegetation: oak–hickory forest, oak savanna,

and bluestem prairie. In the early 19th century, savanna,

prairie, and, especially, forest occurred on moraines.

Wetlands, including bogs, fens, seeps, sedge meadows, and

marshes, were and are common. Bogs contain plants adapted

to acidic conditions including leatherleaf, blueberry,

cranberry, ferns, orchids, pitcher plant, sundew, winterberry,

dwarf birch, and tamarack.

Forest, pastureland, and wetland.

Homesites are especially common on

moraines and near lakes. Ecoregion 53b is

an important recreation area, and includes

Chain O’ Lakes.
31

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

54a.

Illinois/

Indiana

Prairies

19557 Glaciated, flat to rolling plains with

terminal and recessional moraines,

prairie potholes, and old lake beds.

450-1000/

25-275

Thin to thick Quaternary loess

(less than 20 to more than 60

inches), Wisconsinan-age till,

Illinoian-age glacial till (in the

west), outwash deposits,

lacustrine sediments, and

alluvium. Loess is thickest

downwind of major

floodplains, and thins eastward.

Paleozoic sedimentary rocks.

Bedrock is usually deeply

buried by glacial drift, but a

few outcrops of sandstone

occur along the larger rivers

such as the Fox and Illinois.

On uplands: Mollisols

(Argiudolls,

Endoaquolls,

Hapludolls). On

floodplains and low

terraces: Mollisols

(Hapludolls,

Endoaquolls).

On uplands: Flanagan, Catlin, Drummer,

Tama, Joy, Raub, Sable, Muscatine, Ipava,

Bryce, Swygert, Elliott, Ashkum,

Clarence. Soils typically are high in

organic content. Soils derived from loess

primarily occur in the west over Illinoian

till deposits. Younger soils derived

primarily from drift are found in central

and eastern areas on the Wisconsinan till

plain. On floodplains and low terraces:

Lawson, Sawmill, Radford. Natural

drainage is poor.

54b.

Chicago

Lake Plain

439 Nearly level to flat, paleo-lake plain

containing beach ridges, swales,

sand dunes, paleo-spits, paleo-sand

bars, bluffs, and both morainal and

bedrock ridges. Stream dissection,

relief, and slope angles are all low.

580-650/

10-90

Quaternary lacustrine

sediments, beach deposits,

outwash deposits, and glacial

till. Silurian sedimentary rock.

Mollisols

(Endoaquolls),

Entisols

(Udipsamments),

Alfisols (Hapludalfs).

Milford, Gilford, Oakville, Selma,

Coloma, Spinks. Urban land is extensive.

Very poorly- and poorly drained soils are

common on flat plains.

54c.

Kankakee

Marsh

11 Nearly level to depressional plain and

bottomlands. The bottomlands along

the Kankakee River are generally

sandy, flat, and until recently, very

marshy and flood-prone. Scattered

low sand dunes occur.

600-650/

less than

20-50

Quaternary outwash deposits,

organic material, sand flats, and

alluvium. Silurian dolomite.

Mollisols

(Endoaquolls,

Hapludolls).

Gilford, Hoopeston. Natural drainage is

very poor.
Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

54a. Illinois/

Indiana

Prairies

Mesic/

Udic, Aquic

35-41/

160-187

9-35/

62-88

Potential natural vegetation: a mosaic of bluestem prairie and

oak–hickory forest. In the early 19th century, mesic prairie

(dominants: big bluestem, Indian grass, prairie dropseed,

switch grass, and little bluestem), wet prairie (dominants:

prairie cord grass, sedges, and bluejoint grass), and, on gravel

moraines, kames, and loess-covered river bluffs, dry upland

prairie (dominants: little bluestem and side-oats grama) were

common; additionally, oak–hickory forest (dominants: black

oak, white oak, and shagbark hickory) grew on dry, upper

morainal slopes, and maple–oak forest (dominants: red oak,

sugar maple, and American elm) were found on more mesic

sites. Prairie groves contained bur oak, American elm, and

hackberry, and were subjected to recurrent fires. Sycamore,

silver maple, and cottonwood are native to floodplains.

Bulrushes, sedges, cattails, and common reed dominated

prairie potholes and marshes.

Mostly converted to cropland. Corn,

soybeans, and wheat are the major crops;

livestock farming is also important.

Steepest land is used as pastureland or

hayland. Extensive parts of the till plain

have been tiled, ditched, and tied into the

original drainage system to make the land

suitable for cropland and settlement; in the

process, poorly drained land, ponds, and

swamps have been converted to

agriculture. Narrow corridors of riparian

forest occur. Agriculture has affected

stream chemistry, turbidity, and habitat.

Coal mining occurs.

54b.

Chicago

Lake Plain

Mesic/

Aquic, Udic

36-38/

170-173.

Climate is

moderated by

Lake Michigan.

14-31/

63-85

Potential natural vegetation: a mosaic of bluestem prairie and

oak–hickory forest. Dry prairies, mesic prairies, wet prairies,

sand prairies, fens, marshes, floodplain forests, and, on sandy

ridges, scrub-oak forests were common prior to settlement.

Mostly urbanized.

54c.

Kankakee

Marsh

Mesic/

Aquic, Udic

37/

173

13-31/

64-85

Potential natural vegetation: a mosaic of bluestem prairie and

oak–hickory forest. At the time of settlement, northern swamp

forests (dominant: pin oak), wet prairies, bulrush–cattail

marshes, and on scattered, low sand dunes, black oak, white

oak, and sand prairies occurred.

Mostly cleared and drained for cropland;

livestock farming also occurs. Corn,

soybeans, and hay are the main crops. A

narrow corridor of forested wetlands

remains along the Kankakee River. The

Kankakee River and many of its tributaries

have been straightened and deepened so as

to increase both their gradient and

capacity. Ditches are common..
Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

54d.

Sand Area

1978 Discontinuous and low sand dunes,

disjunct sandy outwash plains,

discontinuous sand sheets, sandy

ridges, and swales. Clear, low

gradient, sand-bottomed streams

occur. Summer stream flow from

outwash deposits is cool and

plentiful.

450-900/

less than

25-100

Quaternary windblown sand,

outwash sand and gravel

deposits, silty and clayey quiet

water deposits, limestone

residuum, and alluvium.

Paleozoic shale, limestone,

dolomite, and coal. Limestone

outcrops are common along the

Kankakee River.

Entisols

(Udipsamments),

Mollisols (Hapludolls,

Endoaquolls,

Argiudolls), Alfisols

(Hapludalfs).

Oakville, Watseka, Kankakee, Plainfield,

Selma, Sparta, Maumee, Gilford,

Bonfield, Dakota, Onarga, Bloomfield,

Hoopeston, Rockton, Plattville, Ade. On

sandy ridges, very rapidly permeable,

droughty soils are characteristic and are

prone to wind erosion. Low-lying,

depressional areas are usually poorly

drained.

54e.

Chiwaukee

Prairie

Region

52 Lake and till plains with beaches,

well developed sand dunes, low

beach ridges, swales, and bluffs.

580-800/

less than

10-75

Quaternary nearshore lake

deposits, beach deposits, glacial

till, thin loess, alluvium,

outwash deposits, and

colluvium. Silurian limestone,

dolomite, and some shale.

Alfisols (Hapludalfs,

Endoaqualfs).

Fox, Zurich, Boyer, Grays, Morley,

Wauconda, Markham.

54f.

Valparaiso

Morainal

Complex

1755 Glaciated, hilly, hummocky to

rolling area containing moraines,

kames, eskers, rolling till plains,

outwash plains, kettle holes, and

ravines. Drainage network is not

well integrated. Small lakes and

marshes are common.

550-1200/

50-300

Wisconsinan-age glacial till and

Quaternary lake deposits, thin

loess (less than 20 inches), and

alluvium. Ordovician and

Silurian dolomite, limestone,

and shale. Bedrock is generally

deeply buried by glacial drift,

but outcrops occur along some

of the streams.

Alfisols (Epiaqualfs,

Hapludalfs), Mollisols

(Endoaquolls,

Argiudolls),

Inceptisols

(Eutrudepts).

Morley, Markham, Ashkum, Frankfort,

Blount, Beecher, Nappanee, Elliott, Bryce,

Miami, Hennepin.
34

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

54d. Sand Area

Mesic/

Udic, Aquic

34-38/

165-182

9-33/

62-87

Potential natural vegetation: a mosaic of bluestem prairie and

oak–hickory forest. At the time of settlement, Ecoregion 54d

was largely covered by prairie or mixed oak savanna. On

well-drained, upland sandy sites: dry sand prairie dominated

by little bluestem, fall witch grass, sand dropseed, June grass,

and porcupine grass. On low dunes and sandy ridges: scrub

oak forest and mixed oak savanna (dominants: black oak,

blackjack oak, and white oak) and dry sand prairie. On moist

or wet sites: mesic prairie (dominants: big bluestem, Indian

grass, prairie dropseed, switch grass, and little bluestem), wet

prairie (dominants: prairie cord grass, sedges, and bluejoint

grass), or marshes (dominants: bulrushes, sedges, cattails, and

common reed).

Mostly converted to cropland or used as

pastureland. On sandy outwash plains,

crops require irrigation from ground

water-fed central pivot irrigation systems.

In poorly drained areas, drainage ditches

are common. On excessively drained, low

nutrient dune soils: scrub forest or

pastureland. Locally, vegetation that once

stabilized dunes has been removed,

thereby reactivating dunes. Extensive strip

mining for Pennsylvanian-age coal occurs.

54e.

Chiwaukee

Prairie

Region

Mesic/

Udic, Aquic

34-36/

170

12-29/

61-82

Potential natural vegetation: bluestem prairie and oak savanna.

Tall-grass prairies, scrub oak forests, sand prairies, sand

savannas, fens, and marshes are native.

Nearly all of the natural prairie vegetation

has been replaced by cropland or urban and

industrial development. Some woodland

remains, and is often associated with dunes.

Important conservation and recreation areas

occur, including Illinois Beach State Park,

Illinois Beach Natural Area, and Illinois

Dunes Natural Area. Ecoregion 54e is part

of an important bird migration route. Its

marshes are habitat for several state

threatened and endangered species.

54f.

Valparaiso

Morainal

Complex

Mesic/

Aquic, Udic

34-40/

160-172

11-31/

61-85

Potential natural vegetation: a mosaic of oak–hickory forest

and bluestem prairie. In the early 19th century, prairie covered

slightly more than half of Ecoregion 54f. On well-drained

gravel moraines: dry prairies (dominants: little bluestem and

side-oats grama) and dry upland forests (dominants: bur oak

and white oak). On moister uplands: mesic forests (dominants:

sugar maple, basswood, red oak, and white ash). On poorly

drained uplands: swamp white oak forests. In marshes:

cattails, bulrushes, and common reed are native. On

bottomlands: floodplain forests (dominants: silver maple,

green ash, and American elm). Subsequent fire suppression

has reduced the number of prairie openings, thereby

increasing forest density.

Mostly growing urban and suburban

developments, but wooded areas,

wetlands, and pastureland are common.
35

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

54g.

Rock

River Hills

1878 Glaciated, mostly rolling hills and

undulating plains; more rugged areas

occur in the northwest and southeast,

and contain ridges, ravines, and

bluffs. Tributaries to the Rock River

have cut narrow valleys through

bedrock. Caves and springs occur.

610-1000/

50-325

Thick Quaternary loess (more

than 60 inches), thin glacial till,

glacial outwash, residuum,

lacustrine deposits, and

alluvium. Ordovician and

Silurian dolomite, limestone,

and sandstone. Bedrock

outcrops are common.

On uplands: Mollisols

(Argiudolls,

Hapludolls,

Endoaquolls), Alfisols

(Hapludalfs), Entisols

(Quartzipsamments).

On floodplains and

low terraces:

Mollisols (Hapludolls,

Endoaquolls,

Argiudolls).

On uplands: Tama, Griswold, Muscatine,

Joy, Ogle, Sable, Winnebago, Fayette,

Rozetta, Downs, Plano, Boone. On

floodplains and low terraces: Lawson,

Comfrey, Jasper.

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

71m.

Northern

Shawnee

Hills

589 Largely unglaciated, rugged hills

with cliffs, bluffs, ravines, and

canyons. High gradient, clear

streams occur, and typically have

pools with rock bottoms and riffles

with gravel bottoms.

360-830/

150-450

Thin to thick Quaternary loess,

residuum, colluvium, and in

northernmost areas, thin and

discontinuous Illinoian-age till.

Pennsylvanian sandstone,

siltstone, and shale. Bedrock

outcrops are common.

Alfisols (Fragiudalfs,

Hapludalfs),

Inceptisols

(Dystrudepts).

Grantsburg, Zanesville, Hosmer, Alford,

Wellston, Muskingum, Berks. Fragipans

occur.

71n.

Southern

Shawnee

Hills

768 Unglaciated hills with bluffs and

ravines that are characterized by

many caves, sinkhole plains,

sinkhole ponds, and springs. There

are many clear, cold, spring-fed,

perennial creeks. However, small

intermittent streams that are not fed

by springs also occur. Typically,

pools have rock bottoms and riffles

have gravel bottoms.

350-670/

100-200

Thin to thick Quaternary loess,

residuum, colluvium, and

alluvium. Mississippian

limestone, shale, and sandstone.

Igneous intrusions and

mineralized faults containing

fluorspar occur in the east.

Bedrock outcrops are common.

Alfisols (Fragiudalfs,

Hapludalfs,

Paleudalfs). On

floodplains: Entisols

(Fluvaquents),

Inceptisols

(Eutrudepts).

Hosmer, Grantsburg, Zanesville, Bedford,

Baxter, Wellston. On floodplains:

Wakeland, Haymond. Fragipans occur.
36

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

54g.

Rock

River Hills

Mesic/

Udic, Aquic

34-37/

159-167

8-29/

60-85

Potential natural vegetation: mostly a mix of bluestem prairie and

oak–hickory forest; in rugged northwest, maple–basswood forest.

On level and rolling uplands: dry prairie (dominants: little

bluestem and side-oats grama), mesic prairie (dominants: big

bluestem, Indian grass and prairie dropseed), and wet prairie

(dominants: prairie cord grass, bluejoint grass, and big bluestem).

On dissected upland slopes and on fire-protected sites: dry upland

forests (dominants: black, white, and bur oaks, and black cherry)

and mesic upland forests (dominants:sugar maple, basswood,

slippery elm, and red oak). On cool, north-facing bluffs: Canada

yew and yellow birch. On bottomlands: floodplain forests

(dominants: silver maple, black willow, cottonwood, American

elm, and green ash). In marshes: cattails, bulrushes, and sedges.

Mostly cropland, but livestock farming is

also an important land use. Forest

remnants occur on steep slopes and in

riparian areas. Main crops include corn,

soybeans, and wheat. Field tiles are

normally used for drainage.

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

71m.

Northern

Shawnee

Hills

Mesic/

Udic

46/

185-192

21-41/

67-89

Potential natural vegetation: oak–hickory forest. Few, if any,

prairies occurred prior to settlement. Upland forests are

dominated by white oak, black oak, and shagbark hickory. On

dry sites: forests contain blackjack, post and scarlet oaks. In

sheltered ravines: mesic forests of red oak, beech, sugar

maple, tuliptree, bitternut hickory, white ash, black walnut,

and basswood. On bottomlands: floodplain forests.

Mostly forest; National Forest land is

extensive. Pastureland, hayland, and

cropland also occur. Forestry and recreation

are important land uses. Stream quality in

larger streams is typically good to excellent.

71n.

Southern

Shawnee

Hills

Mesic/

Udic

46/

185-192

22-42/

67-89

Potential natural vegetation: oak–hickory forest. Limestone

glades with dry prairies (dominant: little bluestem) occurred prior

to settlement. Includes flora from the Great Plains, Appalachians,

Ozarks, and Mississippi Alluvial Plain. On dry uplands: forests

with blackjack, post, scarlet, and white oaks, and pignut hickory.

In sheltered ravines: mesic forests of red oak, beech, sugar maple,

tuliptree, bitternut hickory, white ash, basswood, and black

walnut. On bottomlands: floodplain forests. Limestone glades:

little bluestem, side-oats grama, and southern plants (e.g., wild

blue sage and heart-leaved tragia). In acidic seep springs: sedges,

royal fern, lady fern, and cinnamon fern; also sphagnum moss.

Forest, agriculture, and many limestone

glades occur. Livestock grazing, forestry,

hay production, cropland agriculture, and

recreation are important land uses. Corn

and soybeans are the major crops. Quarries

and, in the east, mines occur.
37

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

72a.

Wabash–

Ohio

Bottomlands

1514 Nearly level floodplains and low

terraces. Oxbow lakes, meander

scars, sloughs, and scattered low

dunes occur. Streams have low

gradients, and silt or sand bottoms.

310-480/

less than

50

Quaternary alluvium, outwash

deposits, slackwater deposits,

loess, and lacustrine deposits.

Bedrock outcrops are rare.

Mollisols (Hapludolls,

Endoaquolls,

Argiaquolls), Alfisols

(Endoaqualfs,

Fragiudalfs, Hapludalfs,

Epiaqualfs), Inceptisols

(Endoaquepts,

Dystrudepts, Eutrudepts),

Entisols (Fluvaquents,

Udifluvents).

Armiesburg, Ginat, Zipp, Darwin,

Petrolia, Wakeland, Emma, Belknap,

Carmi, Sciotoville, Bonnie, Cape,

Patton, Reesville, Hurst, Nolin, Shoals,

Stonelick, Genesee, Disco, Westland,

Titus. Poorly drained soils are

common. Extensive areas have been

tiled to improve drainage.

72b.

Glaciated

Wabash

Lowlands

263 Glaciated, undulating to rolling,

dissected till plain with rugged

ravines, floodplains, and terraces

along the Vermilion River and its

tributaries. Many streams have

gravel bottoms, and riffles are

common.

500-700/

25-175

Thin to thick Quaternary loess

(less than 20 to 60+ inches),

glacial till, outwash deposits,

and alluvium. Pennsylvanian

shale, sandstone, limestone, and

coal.

Alfisols (Epiaqualfs,

Hapludalfs), Mollisols

(Endoaquolls,

Argiudolls, Hapludolls).

Fincastle, Sabina, Drummer, Blount,

Morley, Sable, Raub, Sawmill, Landes,

Shaffton.

72d.

Upper

Mississippi

Alluvial

Plain

1886 Broad floodplains and low terraces

of the Mississippi River (and its

major tributaries) upstream of the

confluence with the Missouri River.

Levees, oxbow lakes, islands,

disjunct sand sheets, and scattered

dunes occur. In Ecoregion 72d, the

lower Illinois River is more sluggish

and has more backwater lakes than

the Mississippi River.

420-600/

less than

50

Quaternary alluvium, outwash

deposits, and slackwater

deposits. Paleozoic sedimentary

rock. Bedrock is deeply

covered by Quaternary

sediments.

Mollisols (Hapludolls,

Endoaquolls), Inceptisols

(Eutrudepts).

Lawson, Darwin, Beaucoup, Titus,

Genesee, Sawmill. Clayey, poorly

drained soils are common. but loamy,

moderately well-drained or welldrained soils occur.

72e.

Middle

Mississippi

Alluvial

Plain

654 Broad floodplains and low terraces

of the Mississippi River. Levees,

oxbow lakes, islands, spring-fed

swamps, disjunct sand sheets, and

scattered dunes occur. Bottomlands

are broad and were partly formed by

glacial flood waters. Typically, this

part of the Mississippi River

downstream of the Missouri River

and upstream of Thebes Gorge is

very muddy.

350-420/

less than

50

Quaternary alluvial, outwash,

and slackwater deposits.

Paleozoic sedimentary rock.

Bedrock is deeply covered by

Quaternary sediments.

Mollisols (Hapludolls,

Endoaquolls), Inceptisols

(Endoaquepts).

Lawson, Beaucoup, Darwin, Karnak,

Ware, Medway, Cairo. Clayey, poorly

drained soils are common. but loamy or

sandy, moderately well-drained to

well-drained soils occur.
Level IV

Ecoregion

Soil

Temp./

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

72a.

Wabash–

Ohio

Bottomlands

Mesic/

Aquic,

Udic

42-48/

187-193

19-43/

66-89

Potential natural vegetation: mostly southern floodplain forest. On

bottomlands: floodplain forests (containing: pin, bur, Shumard,

overcup, cherrybark, swamp white, and swamp chestnut oaks, and

sweet gum), river edge forests (dominants: black willow, cottonwood,

sycamore, and silver maple), wet prairies (dominants: prairie cord

grass, sedges, and bluejoint grass), and in the south near the

Mississippi River, swamps (with swamp cottonwood, Drummond’s

red maple, water locust, and, especially in the Cache River Basin, bald

cypress and tupelo gum). In sloughs and meander scars: marshes

(dominants: prairie cord grass and river bulrush). On better-drained

low terraces: shagbark hickory and tuliptree.

Mostly cleared and drained for

agriculture, but some woodlands,

marshes, and swamps remain. Land use

is influenced by seasonally high water

tables and localized flooding. Main

crops are soybeans, corn, and wheat.

Livestock farming occurs. There are

numerous oil and gas wells in

Ecoregion 72a.

72b.

Glaciated

Wabash

Lowlands

Mesic/

Aquic,

Udic

40/

184-186

17-35/

63-87

Potential natural vegetation: oak–hickory forest, mosaic of bluestem

prairie and oak–hickory forest, and beech–maple forest. In the early 19th

century, prairie and dry upland forest (dominants: oaks and hickories)

were found on nearly level uplands, and beech forest occurred in the

mesic ravines along the Vermilion River.

Nearly level uplands have been cleared

for cropland and pastureland, but

forests remain in steep ravines. Main

crops are corn, soybeans, wheat, and

hay. Extensive surface coal mines occur.

72d.

Upper

Mississippi

Alluvial

Plain

Mesic/

Aquic,

Udic

35-39/

162-188

7-36/

60-88

Potential natural vegetation: oak–hickory forest. Native on floodplains:

bottomland forests (dominants: silver maple, American elm, and green

ash with pin oak, pecan, bur oak, sycamore, honey locust, hickories, and

black walnut), mesic prairies (dominants: big bluestem, Indian grass,

prairie dropseed, switch grass, and little bluestem), wet prairies

(dominants: prairie cord grass, sedges, and bluejoint grass), and marshes

(dominants: river bulrush and cattail). Native on sand sheets: dry prairie

(dominants: little bluestem, fall witch grass, sand dropseed, June grass,

and porcupine grass). Native on low dunes: scrub oak forest.

Mostly cleared and drained for

agriculture, but scattered forest

remnants occur especially on islands

and inside of levees. Main crops are

corn and soybeans. The Mississippi

River has been extensively

channelized, and numerous low dams

with locks have been constructed.

72e.

Middle

Mississippi

Alluvial

Plain

Mesic/

Aquic,

Udic

39-47/

188-193

19-41/

67-91

Potential natural vegetation: oak–hickory forest. Prior to settlement,

species-rich bottomland forests, wet prairies (dominants: prairie cord

grass, sedges, and bluejoint grass), mesic prairies (dominants: big

bluestem, Indian grass, prairie dropseed, little bluestem, and switch grass),

marshes (dominants: river bulrush, cattail, pickerelweed, and American

lotus), and bottomland swamps were common. On clay-rich floodplain

soils: bottomland forests (dominants: pin oak, overcup oak, Shumard oak,

and cherrybark oak) and, in the south, bottomland swamps (dominants:

pumpkin ash, swamp cottonwood, Drummond’s red maple, and water

locust). On sandy soils of floodplains: bottomland forests (dominants:

silver maple, ashes, American elm, honey locust, sugarberry, and pecan).

On loamy soils in the south: beech, basswood, and red buckeye.

Nearly all of the original forests,

prairies, and marshes have been

drained and converted to cropland or

pastureland. Main crops are soybeans,

corn, and wheat. Both the alluvial plain

and the river channel have been

significantly modified in the last 100

years.
39

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

72f.

River Hills

2815 Hills, bluffs, cliffs, and ravines

flanking the Mississippi, lower

Illinois and lower Sangamon rivers.

Ecoregion 72f is mostly glaciated,

rugged, and dissected. Areas of karst

occur. Caves and sinkhole ponds are

most abundant in the unglaciated

areas of Calhoun County.

425-800/

50-375

Thick Quaternary loess (more

than 60 inches) and glacial till

(mostly pre-Wisconsinan-age).

Paleozoic sedimentary rocks

dominated by limestone and

sandstone. Bedrock outcrops

are common in the bluffs and

cliffs.

Alfisols (Hapludalfs,

Endoaqualfs).

Seaton, Fayette, Stronghurst, Rozetta,

Hickory, Clarksdale.

72g.

Southern

Ozarkian

River

Bluffs

212 Mostly unglaciated, rugged bluffs

and ravines along the Mississippi

River.

320-1000/

100-680

Thin to thick Quaternary loess,

colluvium, residuum, and

alluvium. Paleozoic cherty

limestone, dolomite, and shale.

Bedrock outcrops are common

in bluffs and ravines. Ecoregion

72g is driftless and mostly

unglaciated; however, the

ecoregion’s northern tip was

covered by Illinoian ice.

Alfisols (Paleudalfs,

Hapludalfs).

Goss, Alford, Baxter. On steep bluffs,

soils are thin and developed from thin

loess or acidic residuum and colluvium.

On bluff tops, soils have developed from

thick loess.

72i.

Western

Dissected

Illinoian

Till Plain

6946 Glaciated, dissected till plain with

broad, nearly level interfluves,

ravines, and floodplains. Stream

gradients are greater in the northern

part of Ecoregion 72i than in the

southern portion.

490-820/

50-200.

Relief is

greater in

the north

than in the

south.

Thick Quaternary loess (more

than 60 inches) and preWisconsinan-age glacial till.

Pennsylvanian and

Mississippian limestone,

sandstone, shale, and coal.

Bedrock outcrops are common

in the valleys and ravines.

On uplands: Mostly

Alfisols (Hapludalfs,

Endoaqualfs); also

Mollisols (Argiudolls,

Argiaquolls,

Endoaquolls).

Clay, Harrison, Clinton, Rozetta, Hickory,

Herrick, Keomah, Ipava, Tama, Virden,

Muscatine, Sable. Prairie soils are high in

organic matter and developed in several

feet of loess. Sheet erosion can be severe

on cultivated slopes.
40

Level IV

Ecoregion

Soil

Temp./

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

72f.

River Hills

Mesic/

Udic,

Aquic

36-39/

169-185

13-37/

63-87

Potential natural vegetation: mostly oak–hickory forest; also a mosaic of

bluestem prairie and oak–hickory forest. On dry sites: forests (dominants: black

oak and white oak). On mesic sites: forests (dominants: sugar maple, basswood,

red oak, hackberry, slippery elm, and black walnut). On and near ridge tops: post

oak. On bottomlands along streams: floodplain forests (dominants: silver maple,

hickories, cottonwood, and sycamore). On steep slopes and loess-covered bluff

tops: hill prairies (dominants: little bluestem and side-oats grama).

Mostly forest. National Forest

land is extensive. Wooded

valleys are important roosting

area for wintering bald eagles.

Ecoregion 72f is part of an

important, forested habitat

corridor along the Mississippi

River.

72g.

Southern

Ozarkian

River

Bluffs

Mesic/

Udic

45-47/

192-193

21-43/

67-89

Potential natural vegetation: mostly oak–hickory forest. On uplands:

extensive, species-rich forests containing red oak, white oak, black oak, sugar

maple, bitternut hickory, and basswood. On steep, cherty slopes: flora tolerant

of acidic soil conditions, such as shortleaf pine, azalea, and farkleberry. On

bottomlands: floodplain forests (containing: white oak, red oak, sycamore,

American elm, river birch, and cottonwood). On loess-covered bluff tops and

some slopes: scattered loess hill prairies (dominants: little bluestem and sideoats grama).

Mostly forest; also scattered

loess hill prairies, and peach

and apple orchards. Forestry

and recreation are primary land

uses. Ecoregion 72g is part of

an important, forested habitat

corridor along the Mississippi

River.

72i.

Western

Dissected

Illinoian

Till Plain

Mesic/

Udic,

Aquic

36-39/

170-187

11-36/

63-88

Potential natural vegetation: mostly oak–hickory forest; also a mosaic of

bluestem prairie and oak–hickory forest. On well-drained slopes in dissected

areas: forests (dominants: black oak, white oak, and shagbark hickory). On

more mesic slopes: forests (dominants: white oak, red oak, and basswood). On

broad, near level interfluves such as near Carthage, Bushnell, and Carrollton:

extensive prairie (dominants: big bluestem, Indian grass, prairie dropseed, and

switch grass). On fine textured soils and on prairie margins: post oak and

blackjack oak. On bottomlands of major streams: floodplain forests

(dominants: silver maple, American elm, ashes, and box elder). Marshes and

wet prairie occurred.

Forest and agriculture. Slopes

and ravines remain mostly

wooded. Nearly level

interfluves, that were once

covered by prairie, are now

used as cropland or livestock

farms. Main crops are corn and

soybeans. Strip mining for coal

occurs locally.
41

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

72j.

Southern

Illinoian

Till Plain

11577 Glaciated, partly dissected, flat to

rolling till plains that become

more hilly to the south where

bedrock is closer to the surface.

Low Illinoian-age moraines

occur. Major streams have broad

floodplains.

380-800/

10-100

Thin to thick Quaternary loess

(10-60 inches), Illinoian-age

glacial till, and alluvium.

Paleozoic (mostly

Pennsylvanian) sandstone,

limestone, coal, and shale.

Bedrock is near the surface in

the south.

On uplands especially in

the north: Alfisols

(Hapludalfs, Albaqualfs,

Natraqualfs, Natrudalfs,

Endoaqualfs). Uplands

especially in the south and

on side slopes and some

flats in the north: Alfisols

(Fragiudalfs, Endoaqualfs,

Albaqualfs). On floodplains

and low terraces: Mollisols

(Hapludolls, Endoaquolls),

Inceptisols (Eutrudepts,

Endoaquepts), Entisols

(Fluvaquents).

Uplands especially in the north: Hoyleton,

Cisne, Huey, Darmstadt, Oconee,

Cowden, Piasa; clayey, slowly- and very

slowly-permeable soils are common.

Impervious fragipans and claypans occur.

Uplands especially in the south and on

side slopes and some flats in the north:

Ava, Bluford, Wynoose. Impervious

fragipans occur. On floodplains and low

terraces: Lawson, Beaucoup, Darwin,

Haymond, Belknap, Wakeland, Petrolia.

Nearly all of the flat uplands are now tiled

to improve drainage.

72k.

Cretaceous

Hills

233 Unglaciated, rolling hills. 310-560/

50-250

Thin to thick Quaternary

loess, residuum, colluvium,

and alluvium. Unconsolidated

Cretaceous and Tertiary sand,

gravel, and silt.

Alfisols (Fragiudalfs,

Hapludalfs), Ultisols

(Fragiudults).

Hosmer, Lax, Alford, Stoy. Fragipans

occur.

72l.

Karstic

Northern

Ozarkian

River

Bluffs

361 Partly glaciated, bluffs and

ravines along the Mississippi

River with well developed karst,

including numerous caves,

sinkholes, sinkhole ponds, and

springs.

400-760/

50-350

Thick Quaternary loess (more

than 60 inches) and some

Illinoian-age till.

Mississippian limestone,

sandstone, and siltstone.

Alfisols (Hapludalfs). Most

soils developed from thick

loess, but on steep river

bluffs, thin soils have

developed from residuum.

Alford, Menfro, Westmore, Neotoma.

72m.

Wabash

River

Bluffs and

Low Hills

749 Low bluffs along the Wabash

River.

400-700/

less than

50-100

Thick Quaternary loess

(mostly more than 60 inches),

outwash material, and

Illinoian-age glacial till.

Mostly Pennsylvanian

limestone; also sandstone,

shale, and coal. Bedrock

outcrops sometimes occur in

the river bluffs and stream

cuts.

Alfisols (Fragiudalfs,

Hapludalfs, Endoaqualfs).

Hosmer, Stoy, Hickory, Weir. Fragipans

occur.
42

Level IV

Ecoregion

Soil

Temp./

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual

(days)

Mean

Temperature

January minmax/ July minmax (

o

F)

Vegetation Land Cover and Land Use

72j.

Southern

Illinoian

Till Plain

Mesic/

Aquic,

Udic

39-45/

187-192

17-40/

65-88

Potential natural vegetation: mostly oak–hickory forest; also bluestem prairie and

oak–hickory forest. Prior to settlement, both forest and prairie were present. On

better-drained, nearly level uplands: forests (containing black oak, shingle oak,

mockernut hickory, and shagbark hickory) and mesic tall-grass prairie (dominants:

big bluestem, Indian grass, prairie dropseed, switch grass, and little bluestem). On

nearly level, clay-rich soils of poorly drained uplands: flatwood forests (containing

post, swamp white, blackjack, and pin oaks). On relatively dry south- and westfacing valley slopes: forests (dominants: white, shingle, and black oaks). On more

mesic valley slopes: forests (containing hickories, white ash, basswood, sugar

maple, black cherry, slippery elm, black walnut, and oaks). On morainal ridges:

mesic forests (containing red oak, elm, walnut, and basswood). On Kaskaskia

River’s broad bottomlands: floodplain forests (dominants: silver maple, willows,

sycamore, and American elm) and some wet prairie (dominants: prairie cord grass,

sedges, and bluejoint grass). On bottomlands of smaller streams: floodplain forests

(dominants: pin and shingle oaks with white oak, red oak, hickories, black walnut,

river birch, and cottonwood). Marshes were associated with the stream floodplains.

Agriculture and forest. Nearly all of

the flat land has been converted to

cropland or pastureland. Forests are

now concentrated in areas unsuited

to farming, such as steep slopes,

ravines, and riparian areas. Main

crops are soybeans, corn, and wheat.

Extensive parts of the till plain have

been tiled, ditched, and tied into the

original drainage system to make the

land suitable for cropland and

settlement.

72k.

Cretaceou

s Hills

Mostly

Mesic/

Udic

47-48/

190-192

24-42/

68-89

Potential natural vegetation: mostly oak–hickory forest. Prior to settlement, forests

were extensive, but some mesic prairies occurred on wide stream bottoms and dry

prairie were found on eastern uplands. On uplands: forest (black, white, cherrybark,

and red oaks, black gum, tuliptree, shagbark hickory, pignut hickory). In the west,

beech are common. On broad stream bottoms: mesic prairies (dominants: big

bluestem, Indian grass, and gama grass).

Agriculture and forest. Steep slopes

remain mostly wooded. Elsewhere,

land has been converted to livestock

farms, cropland, and general farms.

Main crops are corn, wheat, hay and

soybeans.

72l.

Karstic

Northern

Ozarkian

River

Bluffs

Mesic/

Udic

40-45/

189-192

21-40/

67-91

Potential natural vegetation: mostly oak–hickory forest; also a mosaic of bluestem

prairie and oak–hickory forest. Prior to settlement, forests were extensive, and loess

hill prairies were common on loess-covered bluff tops and steep slopes. On ridge

tops: forests (dominants: white oak, black oak, and hickories). On more mesic sites:

forests (dominants: red oak, sugar maple, basswood, and Ohio buckeye). On

bottomlands of streams: floodplain forests (containing white oak, red oak, sycamore,

American elm, river birch, and cottonwood). On steep slopes and loess-covered

bluff tops: loess hill prairies (dominants: little bluestem and side-oats grama).

Forest and agriculture. Steep slopes

remain mostly wooded, but

elsewhere pastureland, cropland,

and orchards occur. Main crops are

corn, wheat, soybeans, hay, apples,

and peaches. Ecoregion 72l is part

of an important, forested habitat

corridor along the Mississippi River.

72m.

Wabash

River

Bluffs and

Low Hills

Mesic/

Udic,

Aquic

40-46/

187-190

19-41/

66-89

Potential natural vegetation: mostly oak–hickory forest; also bluestem prairie and

oak–hickory forest. Prior to settlement, dry upland forests (dominants: black oak and

hickories), mesic upland forests (dominants: white oak, red oak, and sugar maple),

floodplain forests (dominants: silver maple, cottonwood, willows, sycamore, and

American elm), and limited amounts of mesic prairie (dominants: big bluestem,

Indian grass, prairie dropseed, switch grass, and little bluestem).

Forest and agriculture. Steep slopes

and ravines remain mostly wooded.

Elsewhere cropland and livestock

farming occur. Main crops are corn,

wheat, soybeans, and hay.
43

Level IV

Ecoregion

Area

(square

miles)

Physiography

Elevation/

Local

Relief

(feet)

Surficial and Bedrock

Geology

Soil Order

(Great Group)

Common Soil Series

73a.

Northern

Holocene

Meander

Belts

109 Unglaciated, broad floodplains, low

terraces, islands, and meander belts.

Swales, abandoned channels, oxbow

lakes, sloughs, natural levees, and

point bars occur.

300-340/

0-25

Quaternary alluvium. Inceptisols

(Endoaquepts),

Mollisols

(Endoaquolls),

Entisols

(Fluvaquents).

Karnak, Jacob, Cairo, Belknap, Bonnie.

Clayey, poorly- and very poorly drained

soils are common and naturally fertile.

Level IV

Ecoregion

Soil

Temperature/

Moisture

Regimes

Precipitation

Mean annual

(inches)/

Frost Free

Mean annual (days)

Mean

Temperature

January min-max/

July min-max (

o

F)

Vegetation Land Cover and Land Use

73a.

Northern

Holocene

Meander

Belts

Predominantly

Mesic/

Aquic

47/

193

24-42/

68-89

Potential natural vegetation: southern floodplain forest. Prior

to settlement, bottomland forests and bottomland swamps

were extensive. On clay-rich soils of floodplains: species-rich

bottomland forests (containing Shumard oak, cherrybark oak,

swamp white oak, swamp chestnut oak, pin oak, overcup oak,

kingnut hickory, shagbark hickory, bitternut hickory, ashes,

sweet gum, black gum, honey locust, sugarberry, pecan, black

cherry, and catalpa). On coarser-textured floodplain soils with

less impaired drainage: bottomland forests (containing beech,

tuliptree, and cucumber tree). In areas subject to frequent or

prolonged flooding: bottomland swamps (containing bald

cypress and tupelo gum).

Nearly completely cleared and drained for

agriculture; only scattered, bottomland

forests and swamps remain on islands,

oxbows, insides of levees, and, especially,

in conservation areas. Cropland is now

widespread. Main crops are soybeans,

corn, and wheat. Livestock farming also

occurs. Land use in undrained areas is

influenced by seasonal flooding.
44

FIGURE 1

ILLINOIS LEVEL III AND LEVEL IV ECOREGIONS

52 Driftless Area

52a Savanna Section

52b Paleozoic Plateau/Coulee Section

53 Southeastern Wisconsin Till Plains

53a Rock River Drift Plain

53b Kettle Moraines

54 Central Corn Belt Plains

54a Illinois/Indiana Prairies

54b Chicago Lake Plain

54c Kankakee Marsh

54d Sand Area

54e Chiwaukee Prairie Region

54f Valparaiso-Wheaton Morainal Complex

54g Rock River Hills

71 Interior Plateau

71m Northern Shawnee Hills

71n Southern Shawnee Hills

72 Interior River Valleys and Hills

72a Wabash-Ohio Bottomlands

72b Glaciated Wabash Lowlands

72d Upper Mississippi Alluvial Plain

72e Middle Mississippi Alluvial Plain

72f River Hills

72g Southern Ozarkian River Bluffs

72i Western Dissected Illinoian Till Plain

72j Southern Illinoian Till Plain

72k Cretaceous Hills

72l Karstic Northern Ozarkian River Bluffs

72m Wabash River Bluffs and Low Hills

73 Mississippi Alluvial Plain

73a Northern Holocene Meander Belts

Level III ecoregion boundary

Level IV ecoregion boundary

State boundary

County boundary

PRINCIPAL AUTHORS: Alan J. Woods (Oregon State University), James M. Omernik (U.S. Geological

Survey), Charles L. Pederson (Eastern Illinois University), and Brian C. Moran (Indus Corporation).

COLLABORATORS AND CONTRIBUTORS: Candice Bauer (U.S. Environmental Protection Agency),

Bill Ettinger (Illinois Environmental Protection Agency), Gregg Good (Illinois Environmental Protection

Agency), Ed Hammer (U.S. Environmental Protection Agency), Mark Joseph (Illinois Environmental

Protection Agency), Don Keefer (Illinois State Geological Survey), Laura Keefer (Illinois State Water

Survey, Charles Pederson (Department of Biological Sciences, Eastern Illinois University), Andrew

Phillips (Illinois State Geological Survey), Don Pitts (U.S. Department of Agriculture–Natural Resources

Conservation Service), Mike Retzer (Illinois Natural History Survey), and Roy Smoger (Illinois

Environmental Protection Agency.
Joliet

Galena

Chicago

Rockford

Galesburg

Springfield

Bloomington

Mount Vernon

La Salle

Carbondale

St. Louis

Rock Island

54a

72j

72i

54f

54g

72f

72i

72a

71n

54d

72d

72d

53b

54d

72e

72e

71m

53a

54d

54b

52b

72l

72m

52a

72k

71n

54e

71m

54c

72f

72f

72f

72b

72d

54a

72a

72f

72d

72d

54d

72f

72m

73a

72m

72m

54a

72a

72a

72a

72a

30 0 30 60 km.

15 0 15 30 mi.

Albers Equal Area Projection

Standard Parallels 38 ̊30'N and 41 ̊30'N

Central Meridian 89 ̊30'W

F I G U R E 1

I L L I N O I S L E V E L I I I A N D L E V E L I V E C O R E G I O N S

WISCONSIN

INDIAN

A

KENTUCKY

MISSOURI

MISSOURI

IOWA

IOWA

72g