Wisconsin Department of Natural Resources

Ecoregions of Wisconsin

Source: Wisconsin DNR

Date: Last Updated 5/08

James M. Omernik, Shannen S. Chapman, Richard A. Lillie, and Robert T. Dumke

ABSTRACT

Ecoregions are geographical areas within which the biotic and abiotic components of terrestrial and aquatic ecosystems exhibit different but relatively homogeneous patterns in comparison to that of other areas. As such these regions serve as a framework for ecosystem management in a holistic sense and allow integration of assessment and management activities across state and federal agencies that may have different responsibilities and missions for the same geographic areas. Most of the spatial frameworks of Wisconsin that are either termed ecoregions, or have been used for environmental management in the state, were designed to address specific aspects of resource management. In a collaborative effort with various state and federal agencies, we have attempted to define a framework to meet broader ecosystem management needs that consider both the terrestrial and aquatic components as well as the human influences and associations with other ecosystem characteristics that affect management potentials for land and water resources. The "Ecoregions of Wisconsin" consist of 27 level IV regions nested within six larger level III regions that also occupy portions of adjoining states. We provide a brief description of the primary distinguishing characteristics (such as soils, vegetation, climate, geology, physiography, water quality, hydrology and land use) within each level III and IV ecoregion, and discuss the potential applications of the ecoregion map in context of current and future directions of ecosystem management in Wisconsin.

Background

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources; they are designed to serve as a spatial framework for the research, assessment, monitoring, and management of ecosystems and ecosystem components. Special purpose maps of characteristics such as plant communities, water quality, soils, and fish distributions are necessary and have long been used for dealing with specific research and management problems. Ecoregions, on the other hand, portray areas within which there is similarity in the mosaic of all biotic and abiotic components of both terrestrial and aquatic ecosystems. Recognition, identification, and delineation of these multipurpose regions are critical for structuring and implementing integrated management strategies across federal, state, tribal and local governmental agencies that are responsible for different types of resources within the same geographical areas.

Several spatial frameworks that are either termed ecoregions, or are used for environmental resource management, have been developed for Wisconsin. Most, however, were designed to address specific aspects of resource management, rather than ecosystem management in a holistic sense. Others were not refined or subdivided adequately to meet the needs of integrated resource assessment and management across agency and program lines. The purpose of this paper is to present a mapped framework of ecological regions designed to address these broader needs. These regions are intended to complement, rather than replace, the more specific ecological classifications systems, which may remain more effective for the particular subjects they were designed to address.

Historical Definition and Use of Ecoregions of Wisconsin

Although there is general agreement on the need for an ecoregion–type framework for the research, assessment, and management of environmental resources in Wisconsin, there is considerable disagreement over which framework is the most appropriate. The most popular of the several spatial frameworks that cover Wisconsin are those developed by the U.S. Department of Agriculture (USDA) Forest Service (Bailey et al. 1994, Keys et al. 1995), Albert (1995), and the U.S. Environmental Protection Agency (EPA) (Omernik 1987, 1995a; USEPA 1999). The Forest Service and EPA frameworks are national or international in scope and are still undergoing development. Prior to the development of the Forest Service and EPA ecoregion maps, resource managers in Wisconsin used a number of mapping schemes to associate, describe, classify, and otherwise assemble the terrestrial and aquatic resources of Wisconsin into somewhat homogeneous groupings. These included works by Martin (1916) depicting geographical provinces, Finley’s (1976) original vegetation cover map, Poff’s (1970) hydro–chemical lake regions, and the map of total phosphorus in lakes in Minnesota, Wisconsin, and Michigan (Omernik et al. 1988). The more recently developed map of "Natural Divisions of Wisconsin" (Hole and Germain 1994) has also been used. These conceptual organizations of Wisconsin’s landscape, together with many other special purpose maps (e.g., geology, soils, current vegetation, and land use), were precursors to, and were used in the compilation of, the map presented in this paper.

Titled "Regional landscape ecosystems," the mapped classification by Albert (1995) was based largely on patterns of climate, geology, physiography, and soil, as well as the "natural regions" of Hole and Germain (1994), which were heavily based on potential natural vegetation and soils. The portion of the current Forest Service’s National Hierarchy of Ecological Units (Keys et al. 1995) that covers Wisconsin was derived from the work of Albert (1995) and the national classification developed by Bailey (1976). The Forest Service classification was initiated by Bailey (1976) and was fairly consistent across the country regarding scale, level of detail, and its hierarchical approach. The revised Forest Service framework (Bailey et al. 1994, Keys et al. 1995) was compiled by different regional and/or state groups and reflects spatial inconsistencies because of the different perspectives, approaches, and backgrounds of the different individuals or groups who have conducted the work. For Wisconsin, both Albert’s and the Forest Service’s classifications are weighted toward terrestrial ecosystems and forest management uses. Consideration of patterns of land use and aquatic characteristics was relatively unimportant in the development of either of these classifications. This apparent lack of attention to land use and water resource characteristics is viewed by some resource managers as a weakness in these frameworks. Conversely, the inclusion of land use and water resource characteristics into the EPA framework is sometimes viewed as a bias by terrestrial resource managers. This difference in perspectives among user groups is the foundation for a continuing debate and emphasizes the need for further dialog and evolution of all frameworks.

The USEPA framework, of which this map of Level III and IV Ecoregions of Wisconsin is a part, is based on the belief that ecological regions can be determined by identifying areas within which there is coincidence in patterns of geographic phenomena, natural and human–related, that reflect spatial differences in ecosystems and their components. This approach also recognizes that the relative importance of each of these phenomena (which include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology) varies from one region to another regardless of scale or hierarchical level. To avoid confusion with other meanings for different hierarchical levels of ecological regions a Roman numeral classification was adopted for the EPA maps and a North American ecological region framework of which they are a part (Commission for Environmental Cooperation [CEC] 1997). As with other similar state and regional mapping efforts, the process used to compile this new map of level III and IV ecoregions of Wisconsin was collaborative, involving numerous individuals representing several government agencies.

The major differences between this map of ecoregions of Wisconsin and those by the Forest Service and Albert lie in their methods of compilation and their intended use. Whereas the focus of the compilation of the maps by the Forest Service and Albert was on depicting regions in the terrestrial landscape that might exist in the absence of humans, the intent of this map is to show patterns of the entire ecosystem, biotic and abiotic, terrestrial and aquatic, with humans being considered as a biotic component. Until only recently, most attempts to define ecological regions did not consider patterns of human use or influence. It is now generally understood that if humans were removed from the planet the mosaic of ecosystem components would not revert to the patterns that existed in the United States before Europeans set foot on the continent or before Native Americans made their impact on the landscape. Too many plants and animals have been removed and introduced, and the land and water has been too drastically modified through activities including mining, urbanization, and channelization. Although the importance of human influence on ecosystems and their patterns is now obvious, the tendency to consider nature as if it were not part of it seems to have been the norm. Likens (1993) commented that in spite of the fact that humans live in and among ecosystems, ecologists have avoided making detailed and rigorous analyses of the effects of human activities on ecosystems and have sought out pristine or remote areas for their study. Some have stated that, at least for environmental policy, humans should not be considered as a biotic component of ecosystems (Udo de Haes and Klijn 1994). However, humans have clearly had an effect on the regional capacities of ecosystems (Holling 1994). As Meeus (1995) has written, "In the course of time each culture leaves behind its own landscape."

It has been argued that the Forest Service map depicts patterns in terrestrial ecosystems and that the EPA maps, including this one of Wisconsin, reflect patterns in aquatic ecosystems, and that there is a need for separate frameworks for both types of systems. We believe that this argument is flawed for at least two reasons. First, a truly holistic approach to ecosystem management should not consider the aquatic and terrestrial ecosystems separately. "An ’ecosystem approach’ recognizes that ecosystem components do not function as independent systems, rather they exist only in association with one another" (Omernik and Bailey 1997). Second, the approach used to define the EPA maps, including this one of Wisconsin, was not focused solely on aquatic systems, nor did it only consider patterns in lake density and quality in the map compilation process. Just as patterns of bedrock geology and physiography are of prime importance in defining level IV ecoregions in the Appalachians, surficial geology and soils are key components in Iowa, and elevational banding is critical in the mountains of western United States, for parts of the country that are covered by high densities of natural lakes, such as in most of Wisconsin, patterns in lake quality are extremely helpful in revealing ecological regions. Recognition of the spatial coincidence of differences in lake density and quality with differences in many causal and reflective characteristics, including soils, surficial geology, physiography, climate, land use, and vegetation, help in the definition of meaningful ecoregion boundaries.

The Interagency Ecoregion Mapping Effort

Recognition of the recent U.S. General Accounting Office (GAO) Report to Congress (GAO 1994) documents the need for agency–wide adoption of an ecosystem approach to resource management, and the fact that there is no common spatial ecoregion framework to implement the approach, has been documented in a recent U.S. General Accounting Office (GAO) Report to Congress (GAO 1994). Although the GAO report was primarily directed toward the need for a common federal interagency framework, the report implied the need to involve state agencies as well and stated that effective ecosystem management "will require collaboration and consensus–building among federal and nonfederal parties within the larger national land and natural resource use framework" (GAO 1994). In response to the need to identify or develop a common framework of ecological regions, a National Interagency Technical Team (NITT) on ecological mapping formed and was responsible for creating a Memorandum of Understanding (MOU) entitled "Developing a Spatial Framework of Ecological Units of the United States." This Memorandum of Understanding was signed by the heads of all of the federal resource management agencies in 1996. Reaching the objective of the Memorandum of Understanding requires recognition of the differences in the conceptual approaches and mapping methodologies that have been used to develop the most commonly used existing ecoregion–type frameworks, including those developed by the Forest Service (Bailey et al. 1994), the U.S. EPA (Omernik 1987, 1995a), and the U.S. Department of Agriculture USDA, Natural Resources Conservation Service (USDA – NRCS) (USDA – Soil Conservation Service 1981). The first task of the interagency effort is to identify ecological regions common to the three existing frameworks that also have meaning to the holistic objective to depict patterns in the mosaic of all ecosystem components, aquatic and terrestrial, as well as biotic and abiotic. These regions will be roughly at the scale of the Level III ecoregions and original Forest Service sections. While debate continues within the NITT National Interagency Technical Team on the strengths and limitations of the different agency frameworks and the value of rule– based (quantitative) and weight– of– evidence (qualitative) approaches to defining ecoregions, the group has developed a draft map of ecological regions at this general level of detail and has submitted it to a peer review journal for consideration for publication.

Important to the work and final product of the interagency effort is the understanding that the common framework of ecological regions is not meant to replace many of the existing frameworks, insofar as their uses for specific applications is concerned. Mapped classifications, such as the USDA map of Major Land Resource Areas that was based on aggregations of map units from state soils maps, and was originally intended to reflect patterns in soils properties as they relate to agricultural potential, should continue to be used for their specific applications. Likewise, state and regional maps that focus on terrestrial ecosystems for forest management uses will remain important for those purposes. However, for addressing ecosystem management in an integrated fashion across agencies and special interests, an ecoregional classification that reflects spatial patterns in the mosaic of all ecosystem components will be necessary.

Methods

We have defined ecoregions as areas of relative homogeneity in ecological systems and their components. Factors associated with spatial differences in the quality and quantity of ecosystem components, including soils, vegetation, climate, geology, and physiography, are relatively homogeneous within an ecoregion. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. Level I and level II divide the North American continent into 15 and 51 regions, respectively (CEC 1997). At level III, the continental United States contains 103 regions (United States Environmental Protection Agency [USEPA] EPA 1999). Level IV is a further subdivision of the level III ecoregions. Wisconsin contains six level III and twenty–seven level IV ecoregions. The level III descriptions contain some general characteristics of the region, emphasizing the features that make the ecoregion unique from surrounding regions. Level IV descriptions emphasize the important characteristics that make the region different from other ecoregions within the same level III ecoregion.

The approach used to compile this Wisconsin map is based on the premise that ecological regions can be identified through the analysis of the patterns of biotic and abiotic phenomena that reflect differences in ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995a). The process of defining the ecological regions involved collaboration with local experts and began with a data collection meeting held in Madison at which time ecoregionalization methods, existing regional frameworks, and other relevant source material were discussed. Based on the approaches outlined in Omernik (1987, 1995a, and 1995b) and Gallant et al. (1989, and 1995) and the materials and ideas provided by state and local collaborators and other experts, a draft map of level III and IV ecoregions of Wisconsin was developed and circulated among many of the attendees of the first meeting. A second meeting was then held in Central Wisconsin to receive reviewer comments on the draft map and attempt to reach consensus on boundary delineations among the collaborators.

Unlike most of the other similar state and regional efforts to map level III and IV ecoregions, consensus was not reached among those invited to collaborate or confer in this project to map ecoregions of Wisconsin. The reasons for this became clear at the review meeting when the attendees were asked for their comments, suggestions, and concerns regarding the draft map and the method used to compile it. Although 70 percent or more of these people were comfortable with the product and approach, the remainder were not in agreement, generally for one or more of the following reasons: (1) A concern that the "weight of evidence" method used to compile the map was inappropriate and that a quantitative approach should have been used instead; (2) A belief that the map represented aquatic systems and that there should be separate frameworks for terrestrial and aquatic systems; (3) A belief that there should be separate frameworks for aquatic and terrestrial systems and that the aquatic framework should be based on watersheds and/or hydrologic units (see Seaber et al. 1987); (4) A concern that "tension line" (Curtis 1978) had not been followed in defining the regions; and (5) A concern that patterns of present or past land use should not be used as a tool in defining ecoregions.

The differences in perceptions over how to map ecological regions in Wisconsin as well as at the national level were not surprising given the general lack of agreement on the definitions of ecosystems (Gonzalez 1996) and ecosystem management (Lackey 1998), the disagreement over whether ecosystems are abstract concepts or areas with geographical borders (Rowe and Barnes 1994, Blew 1996, Marin 1997, Rowe 1997), Blew 1996, and Rowe and Barnes 1994), and the history of debate over regionalization and whether quantitative or qualitative techniques are more appropriate for the task (see for example Grigg 1967 and Hart 1982). However, acceptance of the approach used to develop the map of ecological regions of Wisconsin has grown. Consensus has been reached across state and federal agencies in a growing number of states (e.g., Pater et al. 1998, Woods et al. 1999, Pater et al. 1998, Chapman et al. in review), and the framework is being used, or is being strongly considered for use, for many national resource management activities, including the development of biological criteria in surface waters (Davis et al. 1996), the development of nutrient criteria in streams (USEPA 1998), and the planning, implementation, and evaluation of bird conservation (USFWS 1999).

We stress that the purpose of this paper is not to tout the advantages of one framework or approach over another, but rather to provide another step in the process of thoughtfully pursuing the debate on, and advancement of, the definition of ecosystems, the delineation of ecological regions, and ultimately more effective ecosystem management.

Descriptions

The naming of level III and level IV ecoregions was intended to associate place names with a key landscape characteristic descriptive or unique to the region. Consequently, the ecoregion names (and the map) serve an educational purpose by relating public perceptions to the environment, thus playing on the concept of "place" and allowing a connection to be made between ecoregions and the general public.

47. Western Corn Belt Plains

Once covered with tall–grass prairie, over 75 percent of the Western Corn Belt Plains is now used for cropland agriculture, and much of the remainder is in forage for livestock. A combination of nearly level to gently rolling till plains and hilly loess plains, an average annual precipitation of 63 to 89 cm, which occurs mainly in the growing season, and fertile, warm, moist soils make this one of the most productive areas of corn and soybeans in the world. The ecoregion is also of major environmental concern regarding surface and groundwater contamination from fertilizer and pesticide applications as well as livestock concentrations.

The northeastern corner of the Western Corn Belt Plains (47) is a loess– covered till plain and extends into a small area in western Wisconsin and borders the northern boundary of the Driftless Area (52). The fertile prairie soils and gentle topography of this area contributes to more intensive agriculture than in the adjacent North Central Hardwood Forests (51) and Driftless Area (52) ecoregions.

47g. Prairie Pothole Region

The Prairie Pothole Region (47g) is characterized by smooth to undulating topography, productive prairie soils, and loess– and till– capped dolomite bedrock. The potential natural vegetation (PNV) is predominantly tall grass prairie with a gradual transition eastward to more mixed hardwoods, distinguishing 47g from the greater concentration of mixed hardwoods of both 51a to the north and 51b to the east, and the mixed prairie and oak savanna of 52b to the south.

50. Northern Lakes and Forests

The Northern Lakes and Forests (50) is an ecoregion of relatively nutrient poor glacial soils, coniferous and northern hardwoods forests, undulating till plains, morainal hills, broad lacustrine basins, and areas of extensive sandy outwash plains. Soils, of this ecoregion, are formed primarily from sandy and loamy glacial drift material and generally lack the arability of those in adjacent ecoregions to the south. Ecoregion 50 also has lower annual temperatures and a frost– free period that is considerably shorter than other ecoregions in Wisconsin (Hole, 1976; U.S. (NOAA, 1974, Hole 1976). These conditions generally hinder agriculture; therefore, woodland and forest are the predominant land use/land cover.

The numerous lakes that dot the landscape are clearer, at a lower trophic state (mostly oligotrophic to mesotrophic with few eutrophic lakes), and less productive than those in ecoregions to the south. Streams of ecoregion 50 are mostly perennial, originating in lakes and wetlands; however, stream density is relatively low compared to ecoregions to the south. The Northern Lakes and Forests region is the only ecoregion in Wisconsin where acid sensitive lakes are found. Portions of the southern boundary of ecoregion 50 roughly correspond to southern most extent of lakes with alkalinity values less than 400 µeq/l (Omernik and Griffith, 1986).

50a. Lake Superior Clay Plain

The Lake Superior Clay Plain (50a) is a flat to undulating lake plain and outwash lowland. The soils of 50a are generally calcareous red clays with organic deposits in swampy areas. A dearth of lakes along with a somewhat milder climate and longer growing season, due to the climate amelioration by Lake Superior, differentiates 50a from surrounding ecoregions. Land use in 50a is predominantly woodland with some limited agriculture of hay, and small grains, and apples on Bayfield Peninsula, distinguishing 50a from most other level IV ecoregions in Northern Lakes and Forests (50) where the land use/land cover is predominantly forest and woodland. Ecoregion 50a has a PNV of boreal forest (although somewhat different than boreal forests to the north); unlike the pine barrens and pine forests of 50c, the mosaic of pine and birch in 50b, and the northern mesic forest of 50e.

50b. Minnesota/Wisconsin Upland Till Plain

The Minnesota/Wisconsin Upland Till Plain (50b) is an undulating stagnation and ground moraine plain, with broad areas of hummocky, acid, loamy and sandy till and outwash. Ecoregion 50b has fewer lakes than ecoregions to the east, but a greater lake density than ecoregion 50a to the north. Extensive wetlands – –in areas of poorly drained soils, peat over acid sedge and woody peat soils– – are scattered throughout the ecoregion and are common in hummocky areas. The till plain of 50b supports a PNV mosaic of red and white pine, conifer swamps, and aspen/white birch/pine forests. Woodland and forest cover the majority of the ecoregion, although there is some limited agriculture with feed–grains and potatoes as the main crops. This region also has one of the lowest densities of roads in the state.

50c. St. Croix Pine Barrens

The St. Croix Pine Barrens (50c) ecoregion is characterized by mostly jack pine, concentrations of red and white pine forests and barrens, well– drained, pink sandy soils. Ecoregion 50c has a greater concentration of lakes, a higher percentage of clear lakes, and lakes with a lower trophic state than in surrounding ecoregions. The sandy soils and pine barren vegetation distinguishes ecoregion 50c from the silty lake plain and boreal forests of 50a and the till plain and more deciduous forest mosaic of 50b.

50d. Ontonagon Lobe Moraines and Gogebic Iron Range

The rolling to hilly, bedrock–controlled and collapsed moraines consisting of loamy till, much of it shallow over igneous and metamorphic rock, distinguish the Ontonagon Lobe Moraines and Gogebic Iron Range (50d) ecoregion from surrounding regions. Rock outcrops increase from very few in the southern portion of this ecoregion to abundant in the north. Likewise, the topography changes from rolling in the southern portion, to hilly in the north. Perennial streams are common, and there are fewer lakes than in ecoregions to the south, but more than adjacent ecoregion 50a. The PNV of 50d is a mosaic of hemlock/sugar–maple/pine forests, swamp conifers, and cedar/hemlock forests. This represents a transition from the boreal forests of ecoregion 50a to the mix of hardwoods and conifer forests of ecoregion 50e. Historic mining of iron and copper occurred along the northern and northwestern edge of this region.

50e. Chequamegon Moraine and Outwash Plain

Irregular plains and stagnation moraines, broad areas of hummocky topography, pitted glacial outwash, numerous kettle lakes, and abundant swamps and bogs characterize the Chequamegon Moraine and Outwash Plain (50e) ecoregion. This region has more poorly developed drainage than ecoregions to the west. The soils are coarse, acid, loamy, and sandy–loam mixed; – –different from the pink sandy soils of ecoregion 50c and the more rocky and silty soils of ecoregion 50g.

50f. Blue Hills

The Blue Hills (50f) ecoregion is characterized by greater relief and a higher concentration of lakes than most surrounding ecoregions, and it contains lakes with generally lower lake trophic states than those of adjacent ecoregions to the east, south, and southwest. End moraines, hummocky hills and depressions, along with areas of Precambrian intrusives, are common to 50f, as compared to the predominantly rocky ground moraines in 50g to the east. Periodic outcrops of pink quartzite have influenced the topography of the region. Ecoregion 50f supports a PNV of hemlock/sugar maple/yellow birch, white pine and red pine forests, a transition from predominantly hemlock/sugar maple/pine forests of ecoregions in the east to sugar–maple/basswood/oak forests, and prairie vegetation of ecoregion 51 to the west.

50g. Chippewa Lobe Rocky Ground Moraines

Much of the Chippewa Lobe Rocky Ground Moraines (50g) ecoregion is comprised of productive but rocky soils, scattered wetlands, extensive eskers and drumlins, and outwash plains. Ecoregion 50g has a considerably lower density of lakes that generally have higher trophic states than the surrounding ecoregions in 50. The rocky soils of 50g are a contrast to the well–drained loamy soils in 50f and the sandy soils in 50i. Ecoregion 50g also supports a PNV mosaic of northern mesic forest (hemlock/sugar maple/yellow birch/white and red pine) and wetland vegetation (swamp conifers/white cedar/black spruce), as compared to the predominantly red and white pine forest of ecoregion 50i and the much lower hemlock component of ecoregions 50f and 50h.

50h. Perkinstown End Moraine

The Perkinstown End Moraines (50h) ecoregion is characterized by hilly to rolling collapsed moraines with outwash sand and gravel, and Precambrian intrusives. Relief in this ecoregion is greater than that of the surrounding regions. The soils of 50h are coarse, loamy, and moderate to well drained, over till, in contrast to the more silty, rocky and poorly drained soils of 50g to the south. In addition, ecoregion 50h has fewer lakes than adjacent level IV ecoregions in the Northern Lakes and Forests (50) ecoregion.

50i. Northern Highlands Lakes Country

The Northern Highlands Lakes Country (50i) ecoregion is distinguished from surrounding ecoregions by pitted outwash, extensive glacial lakes (many of which are shallow), and wetlands. In contrast to other ecoregions in the Northern Lakes and Forests (50) ecoregion, Ecoregion 50i contains a much higher density of lakes of generally lower trophic state and lower alkalinity values (hence, greater sensitivity to acidification). The region has soils that are more gravelly, sandy, well to excessively drained, and developed in deep, acid drift. Ecoregion 50i supports a PNV of white and red pine forests, some pine barrens, and jack pine to the south; unlike the predominantly hardwood forests of surrounding ecoregions.

50j. Brule and Paint Rivers Drumlins

The Brule and Paint Rivers Drumlins (50j) ecoregion has extensive eskers and drumlinized ground moraines, pitted and unpitted outwash, wetlands, large glacial lakes, and a lower density of lakes than in adjacent ecoregion 50i. Lake trophic state is very low with a higher percentage of oligotrophic and mesotrophic lakes than most Level IV ecoregions in the Northern Lakes and Forests (50) ecoregion. Soils of the region range from fine to coarse, poor to well drained, and loamy and silty with extensive organic deposits, differing from the sandy, more acid soils in adjacent ecoregions. The PNV is sugar–maple/basswood forest and hemlock/sugar–maple forest, as compared to the more coniferous forests of 50i and the pine and oak barrens of 50k.

50k. Wisconsin/Michigan Pine and Oak Barrens

Irregular outwash plains and moraines, sandy and sandy–loam soils over outwash, sandy and loamy till, and peat deposits in depressions characterize the Wisconsin/Michigan Pine and Oak Barrens (50k) ecoregion. The features are a contrast to the extensive eskers and drumlins, and more loamy and silty soils of adjacent ecoregion 50j. Also, unlike the hardwood forests of ecoregion 50j to the west, 50k supports a PNV of white/red pine forests, jack pine forests, and oak forests and barrens. Land use in 50k is predominantly woodland, although some mixed agriculture is found. More frost– free days occur in 50k than in adjacent eastern ecoregions, due to the ameliorating effect of Lake Michigan and Green Bay, contributing to the greater agricultural component of the land cover/land use. In addition, 50k has more shallow bedrock than surrounding regions,; with areas of exposed Precambrian basalt and granite.

50l. Menominee Ground Moraine

The Menominee Ground Moraine (50l) ecoregion is characterized by an undulating ground moraine with drumlins and swamps. The uplands consists of loamy soil over calcareous loamy till (some over dolomite); the lowland areas are muck. The region is dominantly woodland and woodland swamp, but there is a significant agricultural presence. PNV of the region is beech/sugar maple/hemlock and swamp conifer, a contrast to the white/red pine, jack pine, and oak forests of neighboring 50k.

51. North Central Hardwood Forests

The North Central Hardwoods Forests (51) ecoregion is transitional between the predominantly forested Northern Lakes and Forests (50) and the agricultural ecoregions to the south. Nearly level to rolling till plains, lacustrine basins, outwash plains, and rolling to hilly moraines comprises the physiography of this region. The land use/land cover in this ecoregion consists of a mosaic of forests, wetlands and lakes, cropland agriculture, pasture, and dairy operations. The growing season is generally longer and warmer than that of ecoregion 50 to the north, and the soils are more arable and fertile, contributing to the greater agricultural component of the land use. Lake densities are generally lower here than in the Northern Lakes and Forests, and lake tropic states tend to be higher, with higher percentages in eutrophic and hypereutrophic classes. Stream density is highly variable, with some areas having virtually no streams – –in wetland and kettle terrain– – to others with high densities of perennial streams.

51a. St. Croix Pitted Stagnation Moraines

The St. Croix Pitted Stagnation Moraines (51a) is a region of ground and stagnation moraines with broad irregular areas of hummocky topography. Soils are silty and loamy, with sandy loamy till commonly underlain by a substratum of acid sand and gravel glacial outwash. There are more lakes in 51a than in ecoregions to the east and south, and lake trophic states, although generally higher than in the region to the north, are lower than in the bordering ecoregion to the southeast. Land use in this region is a mix of agriculture and woodland, in contrast to the mostly woodland and forest land cover of ecoregions to the north, and the greater amounts of agriculture in ecoregions to the southeast. The PNV of 51a ranges from aspen/birch/pine forest, oak–maple forests, and sugar–maple/birch/pine forests and represents a transition from the pines of 50b to the tall grass prairie and oak forests of 47g.

51b. Central Wisconsin Undulating Till Plain

The Central Wisconsin Undulating Till Plain (51b) ecoregion has a greater percentage of agricultural land use than adjacent Ecoregion 51a. The land cover mosaic of woodland and agriculture includes large areas of cropland that produce; silage corn, oats, barley, and some apples. Ecoregion 51b has fewer lakes, with higher trophic states, than adjacent level IV ecoregions in ecoregion 51. The undulating to rolling irregular plains of sandy loam till and outwash sands also distinguish this ecoregion from the stagnation moraines of ecoregion 51a to the west and the lacustrine sand plains of ecoregion 51c to the south. This ecoregion ranges from areas in the far east that are underlain with igneous metamorphic rock outcrops to areas in the west and southwest which that are underlain by sandstone and shale, which also outcrops with sandstone, comprising roughly 70 percent of the total area. The region supports a transitional PNV mosaic of oak, hemlock/sugar maple/yellow birch, and white pine/red pine forests in the north, and more sugar maple/basswood/oak forests to the south.

51c. Glacial Lake Wisconsin Sand Plain

Compared to adjacent ecoregions, the Glacial Lake Wisconsin Sand Plain (51c) is an area of little relief. The droughty outwash, lacustrine, and slopwash sands, sand buttes, and stream bottom and wetland soils support a PNV of jack pine/scrub–oak forests and barrens, along with sedge meadows, and conifer swamps, which characterize this flat sandy lake plain. This PNV is in contrast to the predominantly white and black oak vegetation of ecoregion 51d. The region is also distinguished by its more extensive wetlands and a lack of natural lakes. Most of the existing lakes have been constructed for use in cranberry production. Land use in this region consists of woodland and agriculture with crops including mainly cranberries, strawberries, and potatoes.

51d. Central Sand Ridges

The Central Sand Ridges (51d) ecoregion has the highest density of lakes with the lowest trophic states of all level IV ecoregions in the North Central Hardwood Forests (51). Pitted glacial outwash – – with extensive eskers and drumlins– –, ice contact deposits, rolling ground moraines, and steep end moraines distinguish this region from the flat lake plain of adjacent ecoregion 51c. The dry, sandy, and loamy till soils of the region support a PNV of oak savanna (white oak, black oak, and bur oak) with areas of sedge meadows,; unlike the wetland vegetation and pine or oak barrens of ecoregion 51c and the mosaic of hemlock/beech/maple forests, and mixed conifers of northern ecoregion 51e.

51e. Upper Wolf River Stagnation Moraine

The Upper Wolf River Stagnation Moraine (51e) ecoregion is characterized by the hummocky ground and end moraines, and pitted outwash, in contrast to the level till plains of ecoregion 51f to the east and the irregular till plain of ecoregion 51b to the west. This region supports a PNV mosaic of hemlock/beech/sugar–maple, wetland vegetation, and mixed conifers, as compared to the predominantly oak forests of 51d to the south. Land use in 51e is mixed agriculture/woodland with a larger area of intact forest than adjacent level IV ecoregions in the North Central Hardwoods Forests (51). This is due to land use practices within the Menominee Indian Reservation; more forest cover is still intact, and agricultural practices are less significant. The lake trophic state in 51e is generally higher than in 51d to the south.

51f. Green Bay Till and Lacustrine Plain

Green Bay Till and Lacustrine Plain (51f) is a transitional ecoregion characterized by wetlands, a mix of outwash and loamy recessional moraines, with many areas of outwash plains in the northwest, lake plains and ground moraines in the south, and ground moraines throughout the rest of the region. The PNV of the region represents a shift from the predominantly northern hardwoods and conifer swamps along the lake shore to the maple/basswood/oak forests and oak savanna to the south. The red sandy, loamy soils of this ecoregion are similar to some southern areas in the northern Wisconsin/Michigan Pine Barrens (50k); however, due to the generally milder climate (because of proximity to Lake Michigan), the growing season is more favorable and much of the area has been cleared of natural vegetation and replaced by agriculture.

51g. Door Peninsula

The Door Peninsula (51g) ecoregion is a lake shore region with ground moraines. The longer growing season and shallow fertile, calcareous loamy till soils of this ecoregion support a mixed woodland/agriculture land use. Crops in this ecoregion are mostly orchard and fruit crops, including apples and cherries. The bedrock geology of 51g is shallower than other ecoregions in 51, and consists primarily of Silurian bedrock. In recent years this region has become a popular tourism area.

52. Driftless Area

The hilly uplands of the Driftless Area (52) ecoregion easily distinguish it from surrounding ecoregions. Much of the area consists of a loess–capped plateau with deeply dissected streams. Also called the Paleozoic Plateau, because there is evidence of glacial drift in this region, the glacial deposits have done little to affect the landscape compared to the subduing influences in adjacent ecoregions. Livestock and dairy farming are major land uses and have had a major impact on stream quality. In contrast to the adjacent glaciated ecoregions, the Driftless ecoregion has few lakes, most of which are reservoirs, with generally high trophic states, and a stream density and flow that is generally greater than regions to the east.

52a. Savanna Section

Topography in the Savanna Section (52a) of the Driftless Area is different than the rest of the level III ecoregion because of its characteristic broad relatively level ridge tops and narrow steep sided valley bottoms. Elsewhere in the dissected Driftless Area the landform mosaic comprises relatively broad, flat valley bottoms with steep sharper crested ridges or a pattern of nearly equal amounts of flatter areas in the valley bottoms and interfluves. The soils are well drained silty loess over residuum, dolostone, limestone, or sandstone. Land use patterns in the Driftless Area also follow spatial differences in slope; hence, 52a is predominantly agriculture on the uplands and some mixed woodland/agriculture in lowland areas. The PNV of the region is a mosaic of oak forests and savannas, large prairie grassland areas, and some sugar maple/basswood/oak forests. The region is also know known for past lead and zinc mining.

52b. Coulee Section

Dissected slopes and open hills with most of the gentle slope on the lowland characterize the Coulee Section (52b) ecoregion. Soils are well drained silty loess over residuum, limestone, sandstone or shale, with soils over quartzite in the Baraboo Hills area. Land use in the region is predominantly mixed agriculture/woodland, with most of the agriculture occurring on the lowlands and more level hilltops. The PNV of ecoregion 52b is a mosaic of oak forests, prairie, with larger areas of sugar maple/basswood/oak forests than in 52a.

53. Southeastern Wisconsin Till Plains

The Southeastern Wisconsin Till Plains (53) ecoregion supports a mosaic of vegetation types and represents a transition between the hardwood forests and oak savannas of the ecoregions to the west and the tall–grass prairies of the Central Corn Belt Plains (54) to the south. Like the Corn Belt Plains (54) ecoregion, land use in the Southeastern Wisconsin Till Plains (53) is mostly cropland, but the crops have historically been largely forage and feed grains to support dairy operations, rather than corn and soybeans for cash crops. The ecoregion has a higher plant hardiness value than in ecoregions to the north and west, a different mosaic of soils than western ecoregions, and flatter topography. There are fewer lakes here than in ecoregions to the north, but considerably more than in the western Driftless Area (52) and the southern Central Corn Belt Plain (47). The region also has a relatively high aquatic species diversity.

53a. Rock River Drift Plain

The Rock River Drift Plain (53a) ecoregion has numerous small creeks, a greater stream density and fewer lakes than in ecoregions to the north and east. Glaciation of this region is much older, late Pliocene – early Pleistocene, than in surrounding ecoregions. The drift mantle is thin and deeply weathered with leached soils developed from a silt–loam cap of loess over glacial drift. Steeper topography and broad outwash plains with loamy and sandy soils also characterize this region.

53b. Kettle Moraines

The Kettle Moraines (53b) ecoregion contains a higher concentration of lakes with lower trophic states than in the rest of the level III ecoregions of the Southeastern Wisconsin Till Plains (53). The soils are clayey to the east, especially along the Lake Michigan shore, and more sandy to the west, but generally less clayey than the soils in ecoregion 53d to the north. The region also contains extensive ground and end moraines and pitted outwash with belts of hilly moraines and generally has greater relief than ecoregion 53d to the northeast.

53c. Southeastern Wisconsin Savanna and Till Plain

The till plains of the Southeastern Wisconsin Savanna and Till Plain (53c) ecoregion support a mix of agriculture (cropland, and dairy operations) and woodland. Crops include forage crops to support the dairy operations and a wide range of truck and specialty crops. Most of the original vegetation has been cleared with forested areas remaining only on steeper end moraines and poorly drained depressions. Irregular till plains, end moraines, kettles, and drumlins are common, and wetlands are found throughout the region, especially along end morainal ridges. PNV of this region is transitional with a mosaic of sugar maple, basswood, oak to the east, and an increasing amount of white, black, and bur oak, oak savanna, prairie, and sedge meadows toward the west.

53d. Lake Michigan Lacustrine Clay Plain

The Lake Michigan Lacustrine Clay Plain (53d) ecoregion is characterized by red calcareous clay soil, lacustrine and till deposits, and a flat plain. The topography of this ecoregion is much flatter than ecoregions to the south, and there are fewer lakes, but with the lakes have generally higher trophic states, than in adjacent level IV ecoregions in (50) and (51). Soils are generally silty and loamy over calcareous loamy till, with muck and loamy lacustrine soils in low–lying areas. Ecoregion 53d has prime farmland with a longer growing season and more fertile soils than surrounding ecoregions. Agriculture has a different mosaic of crops, with more fruit and vegetable crops, than that of ecoregion 53c. The PNV of this region is beech/sugar maple/basswood/red and white oak forests with a greater concentration of beech than other ecoregions in 53.

54. Central Corn Belt Plains

Prairie communities were native to the glaciated plains of the Central Corn Belt Plains, and they were a stark contrast to the hardwood forests that grew on the drift plains of ecoregions to the east. Beginning in the nineteenth century, the natural vegetation was gradually replaced by agriculture. Farms are now extensive on the dark, fertile soils of the Central Corn Belt Plains, and mainly producinge, corn and soybeans, cattle, sheep, poultry, and, especially hogs, are also raised, but they are not as dominant as in the drier Western Corn Belt Plains to the west. Agriculture has affected stream chemistry, turbidity, and habitat. The extent of Central Corn Belt Plains (54) ecoregion in Wisconsin is contained within a small area in the southeastern portion of the state. Land use of the ecoregion continues to change, from exclusively agriculture to a pattern with an increasing amount of urban and industrial land.

54e. Chiwaukee Prairie Region

The Chiwaukee Prairie Region (54e) ecoregion is characterized by intensive agriculture, prairie soils, loess capped loamy till, and lacustrine deposits. The soils of ecoregion 54e are fertile, and generally more productive than those of ecoregion 53 to the north and west. The PNV of the Chiwaukee Prairie Region is predominantly tall–grass prairie, in contrast to the southern mesic forest and oak savanna of the adjacent region to the north and west. Most of the natural prairie vegetation of ecoregion 54e has been replaced with cropland or urban and industrial land cover.

Applications

The ecoregion framework outlined in this paper will be particularly supportive of the more holistic approaches to natural resources conservation emerging in Wisconsin because it considers elements of the entire ecosystem, terrestrial and aquatic, abiotic and biotic, including humans. These contemporary approaches to environmental stewardship, collectively termed ecosystem management by some practitioners, strive to reconcile the conservation of ecological integrity and biological diversity with the availability of economic opportunities and livable communities. The overall goal is sustainable ecological, social, and economic systems. Ecoregions can provide a framework to which pertinent socio–economic and demographic information may be linked using geographic information systems.

The finding of common ground among socio–economic and ecological considerations is increasingly being undertaken through stakeholder partnerships. Participants in these endeavors generally have diverse interests, values, and technical knowledge; therefore, processes and tools – – such as ecological classification systems – –developed for these new management approaches should consider this circumstance. The ecoregions defined herein are intended to be broadly understandable and acceptable due to their inclusive nature. Furthermore, they are named with consideration for widespread recognition by resource managers and publics alike. Nonetheless, this ecological framework must be considered dynamic and subject to refinement with ongoing use and increased understanding in the spatial nature of ecosystems.

The Wisconsin Department of Natural Resources (DNR) prepared a report for its resource managers in May 1995 titled "Wisconsin’s Biodiversity as a Management Issue" (DNR 1995). The report recommended (page 31) that DNR manage at a landscape scale which that involves determining both spatial and temporal scales appropriate to the problem or project and then assessing implications at larger and smaller scales. Furthermore, the DNR biodiversity report proposed that ecoregions be determined for Wisconsin for use in developing management goals. These goals would "meet a wide variety of diverse ecological and socio–economic needs, including the conservation of biodiversity.".

In response to the need to define ecoregion boundaries, in 1998 the agency initiated a project to identify Ecological Landscapes of Wisconsin (DNR 1999). The ecological landscape units defined in the 1998–99 effort followed the U.S. Department of Agriculture (USDA) Forest Service’s National Hierarchy Framework of Ecological Units and were designed primarily to assist regional and statewide efforts for maintaining and restoring natural communities. However, consideration was also given to broader ecosystem planning and communications applications. Ecological, social, and institutional data plus management opportunities were to be assembled for each of the 17 ecological landscape units. The Ecological Landscapes of Wisconsin map has many similarities (e.g., some boundaries lines and units are similar in position and shape) to the level III and IV ecoregion map presented in this paper, leaving the impression that the two maps are redundant. However, while both maps contain similarities, their differences reflect different origins and purposes. The Ecological Landscape map was designed by the DNR’s Land Ecosystem Management Planning Team for the exclusive purpose of defining "areas similar in ecology and management opportunities.". The delineation of area boundaries on the Ecological Landscape map was influenced by a tendency to mesh the map units into the hierarchical units defined in the Forest Service’s National Hierarchy mapping system. As mentioned previously, the National Hierarchy mapping was directed primarily towards forestry ecosystems and paid little consideration to land use, hydrology, and water quality, which are of critical importance to aquatic ecosystems. Recognizing the emphasis given to terrestrial ecosystems in their National Hierarchy maps, the Forest Service designed a separate framework for aquatic ecosystems (Maxwell et al., 1995).

The ecoregions described in this paper were, on the other hand, developed to facilitate ecosystem management in a more holistic sense and define regions of similar patterns in the mosaic of terrestrial, aquatic, biotic, and abiotic ecosystem components with humans being considered as part of the biota. The intent was to define "general purpose" regions to allow the various state (and federal) agencies and programs with different interests and missions to integrate their assessment, management, and reporting activities. The framework was not intended to replace narrower or special purpose frameworks or maps that may be better suited for addressing specific issues. Also, the level III and IV ecoregion framework described in this paper will augment the set of ecological landscapes by providing counterpart ecoregions that are more broadly defined and linked to the international framework – –Ecological Regions of North America (CEC 1997).

The DNR has also identified administrative areas termed Geographic Management Units (GMUs), which represent a compromise among ecoregions, watershed management units, and jurisdictional/political boundaries. These GMUs cannot serve the same ecological purposes as a strictly ecological framework but likely have advantages for working collaboratively with stakeholder partnerships. Ecoregions as planning entities tend to encourage ecological thinking, which most often must be then transferred to socio–political contexts for implementation. Effective use of these various spatial networks critically depends on the development of "cross–walking" capability using GIS technologies.

The ecoregions described in this paper can serve research and education purposes as well as management functions. Ecoregions can provide a basis for the collection and organization of biogeophysical data such as that being contemplated under the new DNR initiative entitled the Aquatic and Terrestrial Resources Inventory. They can also provide a framework for the development of indices of ecological integrity and other parameters that reveal the status of our landscape. Ecoregions can assist habitat suitability analyses and studies of landscape patterns that look at fragmentation and habitat corridor issues. These investigations can be helpful in designating recovery strategies for threatened and endangered species such as the timber wolf.

Ecoregions can serve an educational function by improving awareness of ecosystem spatial scales and their nested hierarchy. Ecological classification per se helps us appreciate the interconnectedness and dependency among ecosystems and also helps us learn more about the elasticity of ecological systems and their responses to natural and human–induced disturbances. Ecoregions provide a suitable context for deliberations of ecosystem opportunities and limitations plus a basis for identifying future desired conditions expressed as ecosystem goals and objectives. Ecoregion frameworks help provide an understanding of the "big picture" for local initiatives and also the converse; they should be viewed not just as an analytical tool but a tool for learning ecological relationships and concepts.

Management actions can be benefited by the use of ecoregions. The protection and preservation of sensitive areas and critical resources can employ ecoregions as a basis for examining the patterns and distributions of these elements across broad suitable landscapes to avoid actions that cause isolation effects but instead encourage connectedness. Some natural communities such as pine–oak barrens and grasslands occurred in widely distributed units in presettlement Wisconsin. An evaluation of current opportunities can benefit from an assessment of potential sites within the context of their respective ecoregions. Although grassland restoration might be considered in several ecoregions (e.g., Prairie Pothole Region, Savanna Section, Rock River Drift Plain, Kettle Moraines, Southeastern Wisconsin Savanna and Till Plain, and Chiwaukee Prairie Region) based on historic presence, an analysis of opportunities and limitations for the various ecoregions may suggest better potential for building a viable (i.e., sustainable) matrix of grasslands within one or two of these regions. This type of analysis is probably improved by the use of ecoregions that consider land use among their determining factors.

Ecoregions can help structure water resource assessment and management programs in Wisconsin. Watersheds, as landscape units, are generally well understood by various publics and are often used as the basis for water resource programs. Watersheds are critical as research units because they help identify areas of influence on water quality relative to a particular point. However, watersheds seldom correspond to areas with which there is similarity in the factors that cause or reflect differences in the quality and quantity of water (Omernik and Bailey 1997, Griffith et al. 1999). In contrast, ecological regions define areas of similarity in mosaics of these factors and hence depict areas of reduced variability in capacities, potentials, and responses to land management activities. A more refined analysis of the characteristics associated with spatial differences in water quality is yielded by consideration of ecological regions within and across watershed boundaries. Here again the incorporation of land use as a component of this ecological classification system is important to its use in exploring non–point source water quality issues, developing reference site data, defining biogeophysical criteria, and setting goals for watersheds, especially larger units such as the Wisconsin and Mississippi River basins.

In 1999, the Forest Service undertook a reassessment of "roadless areas" and road building in national forests. The protection of roadless areas can impact water quality, biological diversity, forest health, and recreational opportunities. Concerns were raised on how management of the Nicolet–Chequamegon Forest in Wisconsin might be altered by the assessment. The Forest was evaluated under a similar study (RARE– –Roadless Area Review and Evaluation) in the 1970’s (U.S. Forest Service 1979). A contemporary assessment of opportunities for designation of roadless areas or similar management units such as wilderness or natural areas could involve a look at the size and distribution of potential sites across various ownerships by ecoregions.

We believe that the level III and IV ecoregion map presented herein is the most integrated ecological framework developed for Wisconsin. It is nested within an international system and has excellent potential for structuring environmental monitoring and management activities. Because of its widespread development and comprehensive nature, the framework is particularly suited to multidisciplinary, interagency work. The map can enhance collaborative ecosystem research, monitoring, planning, and management. It can also provide a foundation for conducting bioassessments, establishing environmental standards, and reporting such as the 305(b) reports and also State of the Environment reports to their legislature and publics. Clearly, this ecoregion framework has many potential applications, but they will not be realized unless the map is added to the tool kit of Wisconsin resource managers and used along with other tools to meet the challenges of contemporary management of natural resources.

Acknowledgments

We wish to acknowledge the many individuals who provided materials and ideas that were used to distinguish the ecoregions and delineate their boundaries. Particularly deserving of mention is Dave Hvizdak. Jim Addis should be recognized for his help in initiating the project and providing partial support. We thank Darrell Zastrow, Gerald Bartelt, Joe Kovach, Dave Hvizdak, and Gordon Matzke for their critical comments of earlier drafts of the manuscript. Partial support was also provided by the U.S. Environmental Protection Agency, Region V REMAP program. The Wisconsin Department of Natural Resources provided additional funding.

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– – 1968. Aeolian silt and sand deposits of Wisconsin

– – 1996. Bedrock geology of Wisconsin

– – 1986. General land use/ land cover

– – 1989. Groundwater contamination susceptibility in Wisconsin

– – 1964. Glacial deposits of Wisconsin

– – 1995. Hydric soils in Wisconsin (STATSGO data)

– – 1979. Major land use

– – 1990. Plant hardiness zone map: Wisconsin

– – 1995. Potential gravel source areas: Wisconsin (STATSGO data)

– – 1996. Potential prime farmland in Wisconsin (STATSGO data)

– – 1983. Thickness of unconsolidated material in Wisconsin

James M. Omernik1, Shannen S. Chapman2, Richard A. Lillie3, and Robert T. Dumke4

Affiliations/Address:

1 James M. Omernik. Blurb. Address: U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, 200 S. W. 35th St., Corvallis, OR 97333. Email:

2 Shannen S. Chapman. Blurb. Address: Dynamac Corporation, 200 S.W. 35th St., Corvallis, OR 97333. Email:

3 Richard A. Lillie. Blurb. Address: Wisconsin Department of Natural Resources, Bureau of Integrated Science Services, Fish and Habitat Section, 1350 Femrite Drive, Monona, WI 53716. Email:

4 Robert T. Dumke. Blurb. Address: Wisconsin Department of Natural Resources, Office of the Secretary, 101 S. Webster St., Box 7921, Madison, WI 53707 (Retired). Email: