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Minnesota’s St. Croix River Valley and Anoka Sandplain

Minnesota’s St. Croix River Valley and Anoka Sandplain: A Guide to Native Habitats

Daniel S. Wovcha
Barbara C. Delaney
Gerda E. Nordquist
Thomas R. Klein
Al Epp
Copyright Date: 1995
Edition: NED - New edition
Pages: 248
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  • Book Info
    Minnesota’s St. Croix River Valley and Anoka Sandplain
    Book Description:

    Offers a fascinating landscape history of this six county region in east-central Minnesota, including detailed descriptions of the 39 varieties of native habitats which still exist there. The region includes the counties of Anoka, Chisago, Isanti, Ramsey, Sherburne, and Washington. All of the data is summarized and interpreted to provide a convenient guide for anyone interested in the natural history of the region, including landowners seeking more information on a forest or prairie on their land, persons interested in visiting native habitats in the region, government planners and resource managers, and high school biology classes. A set of five companion color wall maps is available separately.

    eISBN: 978-0-8166-8607-0
    Subjects: Biological Sciences

Table of Contents

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  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. Preface
    (pp. vii-viii)
    Daniel S. Wovcha, Barbara C. Delaney and Gerda E. Nordquist
  4. Acknowledgments
    (pp. ix-1)
  5. Part I A Landscape History of the St. Croix River Valley— Anoka Sandplain Region

    • 1. Geologic History and Major Landforms of the Region
      (pp. 4-13)

      Most of the geologic features of the Region, such as plains, hills, river valleys, and lake basins, were produced directly or indirectly by glaciers over the past 20,000 or so years. In some sense, however, the present landscape began forming about 1.1 billion years ago, when the earth’s crust parted along a rift stretching from Lake Superior, through Minnesota, to Kansas. In east-central Minnesota, lava flowed up out of the rift and hardened, forming a broad plain of basalt rock across the land (Ojakangas and Matsch 1982). So much lava poured from the rift in east-central Minnesota that the earth’s...

    • 2. Postglacial Landscape
      (pp. 14-20)

      Vegetation began to develop in the Region even before the end of the glaciation. The vegetation then changed dramatically over the next 10,000 or 11,000 years, partly in response to changes in climate and apparently also the activities of American Indians.

      The first vegetation to develop was patches of spruce trees and perhaps tundra plants around the margins of the glaciers and on buried ice blocks (E. J. Gushingpers. comm.1992, Wright 1972). By about 11,000 years ago, much of the Region was covered by boreal vegetation dominated by spruce trees, with smaller numbers of paper birch, aspen, black ash,...

    • 3. Major Vegetation Patterns at the Time of Euro-American Settlement
      (pp. 21-29)

      At the time of Euro-American settlement, the landscape of the Region was dominated by scrubby oak woodlandbrushland, or oak barrens or openings, as woodland was often called by early settlers and land surveyors in the Region. Marshes and swamps were extensive in parts of the Region, and there were also patches of prairie and forests (see map 1, inside front cover). We know this about the vegetation in part from descriptions in the journals of explorers and early Euro-American settlers but mainly from data on trees and other features of the vegetation collected in the Region between 1847 and 1857...

    • 4. Influence of European-Americans
      (pp. 30-37)

      The immigration of Euro-American settlers to the Region introduced a culture very different from that of the previous inhabitants. The pattern of consumption of plants and animals according to the local and immediate needs of a relatively small population was replaced by new patterns of use of the land and its plants and animals that were driven increasingly, as settlement proceeded, by speculation, by competition among businesses and landowners, and by trade with distant regions. This outcome was perhaps not surprising, as thousands of people migrated to the Region within a few decades, seeking wealth or at least a comfortable...

    • Summary
      (pp. 38-39)

      Landscapes are dynamic. They change over time in response to climate, geologic processes, the growth of plants, and the activities of human beings and other animals. The landscape of the St. Croix River Valley—Anoka Sandplain Region has been covered by molten rock, inundated by seas, and buried beneath glacial ice lobes perhaps thousands of feet thick. In between these tremendous events, the land was weathered and eroded, soils have built up, and communities of plants and animals have developed. In general, change has been slow, occurring over hundreds, thousands, and even millions of years.

      Although the present landscape of...

  6. Part II The Native Habitats and Natural Communities of the St. Croix River Valley– Anoka Sandplain Region

    • 5. Guide to Part II
      (pp. 42-45)

      While in principle the idea of a community of native plants and native animals is straightforward, natural communities can be denned and classified in many ways. The classification used in this book is that developed by the Natural Heritage Program of the Minnesota Department of Natural Resources (Minnesota Natural Heritage Program 1993): natural communities are classified largely in terms of their vegetation, which is influenced by such things as soil, climate, hydrology, topography, fire, interactions among plants, and interactions of plants with animals. This classification is outlined in figure 5.1. The most general division between communities, shown at the top...

    • 6. Deciduous Forests
      (pp. 46-61)

      Deciduous forests are upland communities with a nearly continuous canopy of tall, mature, broad-leaved trees, such as oak, basswood, elm, maple, aspen, and birch, that produces shady, relatively moist conditions in the understory. Deciduous forests historically covered much of the landscape of eastern North America, stretching westward as far as the Mississippi River, where they gave way to the prairies of the central plains. The St. Croix River Valley—Anoka Sandplain Region lay in the area of transition between forest and prairie. At the time of Euro-American setdement deciduous forests covered only about 13% of the Region, mainly in the...

    • 7. Mixed Coniferous-Deciduous Forests
      (pp. 62-66)

      Mixed coniferous-deciduous forests are upland communities dominated by pines interspersed with deciduous trees such as oak, maple, aspen, and birch. Mixed coniferousdeciduous forests were widespread throughout the coniferous forest zone of Minnesota (see the map on page 3), just reaching into the northern fringes of the Region in Isanti and Chisago counties before Euro-American settlement and logging (see map 1).

      According to General Land Office survey bearing tree records from the 1840s and 1850s, white pine occurred sporadically across the northeastern third of the Region. At some locations, dense patches of white pine trees may have covered more than 10...

    • 8. Deciduous Woodlands
      (pp. 67-71)

      Deciduous woodlands are upland communities composed of a tree canopy, ranging from 10 to 70% in cover, above a dense layer of shrubs or young oak or aspen sprouts. They develop where frequent fires, bedrock outcrops, or steep slopes prevent the formation of a closed forest canopy.

      Before Euro-American settlement, deciduous woodlands were widespread in parts of the deciduous forest zone of Minnesota (see the map on page 3), such as on the Anoka sandplain and parts of the St. Croix moraine (see figs. 3.1 and 3.5). At present, two kinds of deciduous woodland communities occur in the Region: oak...

    • 9. Deciduous Savannas
      (pp. 72-79)

      The deciduous savannas of midwestern North America are upland communities of scattered trees, typically oaks, above a ground layer of prairie grasses and forbs. Deciduous savannas occur mostly within the transition zone between the central prairies and the eastern deciduous forests; in Minnesota, they occur primarily in areas where prairies historically merged with oak and aspen forests within the deciduous forest zone (see the map on page 3).

      Most of the savannas of the Midwest were naturally maintained by fire and periodic grazing. In the absence of fire, they tend to develop into brushy oak woodlands as taller woody plants...

    • 10. Upland Prairies
      (pp. 80-92)

      Native grasslands once extended eastward across the Great Plains and into western and southern Minnesota, interrupted only by rivers, wetlands, and in some areas, lakes. Farther eastward into Minnesota, as well as into parts of Wisconsin, Illinois, Indiana, Michigan, and Ohio, they became increasingly interspersed with woodlands and forests. The native grasslands of Minnesota and states to the east were generally tallgrass prairies. Mixed grass prairie and short grass prairie (or steppe) occurred to the west where the climate is drier. In Minnesota, prairies that might otherwise have succeeded to woodland or forest in the prairie-forest transition zone (see the...

    • 11. Floodplain Forests
      (pp. 93-97)

      Floodplain forests are composed of deciduous trees and herbs that develop on mineral soil on river floodplains and are adapted to prolonged flooding, severe erosion, and sedimentation. In the St. Croix River Valley—Anoka Sandplain Region, large floodplain forests once were common along the Mississippi River downstream from Fort Snelling and on the St. Croix River upstream from Stillwater, with narrow stands along the Rum, Sunrise, and Elk rivers (see map 1 and fig. 3.4). They covered about 1% of the landscape in the 1800s. Because so many rivers join together in this Region, floodplain forests have long been used...

    • 12. Hardwood Swamps
      (pp. 98-106)

      Hardwood swamps are forested wetland communities on black, organic soil, dominated by trees that have shallow root systems and can survive nearly continuous soil saturation. Major tree species are black ash, red maple, American elm, and yellow birch. At the time of Euro-American settlement, hardwood swamps commonly bordered shallow wetlands across much of the Anoka sandplain and the Grantsburg sublobe till plain (see figs. 3.1 and 3.4).

      The Region’s hardwood swamps have been altered in many ways since the mid- 1800s, particularly those adjacent to farmland. They have been grazed during drought years. They have been drained for pasture and...

    • 13. Conifer Swamps
      (pp. 107-115)

      Conifer swamps are forested wetland communities that develop on organic soils in shallow basins and are dominated by tamarack, black spruce, or white cedar. In Minnesota, conifer swamps occur mainly in the conifer-hardwood forest zone (see the map on page 3). In the mid-1800s, tamarack swamps were common in the Region, but black spruce swamps and white cedar swamps were rare, reaching the very southern limit of their range in Minnesota here.

      Since settlement, the Region’s conifer swamps have been altered to varying degrees by logging, draining, flooding, invasion by nonnative plants, and nutrient inputs from farms and surrounding developed...

    • 14. Shrub Swamps
      (pp. 116-122)

      Shrub swamps are shallow wetland communities dominated by tall shrubs such as speckled alder, pussy willow, and red-osier dogwood. They tend to occur in wetlands that are too wet or frequently flooded for conifer or hardwood swamps to develop, yet they do not tolerate the deeper water that typically supports marsh communities. Shrub swamps sometimes originate after the tree canopy of a forested swamp has been destroyed, commonly by flooding or windstorms.

      The historic distribution of shrub swamps in the Region is not entirely clear, because the General Land Office surveyors did not always distinguish them from wet meadow, marsh,...

    • 15. Emergent Marshes
      (pp. 123-129)

      Emergent marshes are wetland communities dominated by herbaceous plants such as cattails, arrowhead, bulrushes, and sedges that stand above the water level (fig. 15.1). Emergent marshes usually develop in deeper water than wet meadow and fen communities and in most years, have standing water throughout the growing season. Most of the marsh plants root in mineral or mucky substrates at the bottom of the wetland, although cattails can form floating rafts composed of their buoyant rhizomes.

      The presettlement extent and species composition of emergent marsh communities in the Region are unclear because the General Land Office survey notes of the...

    • 16. Wet Meadows and Fens
      (pp. 130-142)

      Wet meadows and fens make up a broad class of shallow wedand community types whose main shared characteristic is a herbaceous cover dominated by medium- or narrowleaved grasses and sedges. Communities included here range from wet prairie swales that are dry in summer to shallow peatlands, called fens, dominated by spongy mosses or a carpet of sedges. They differ from emergent marshes in that broad-leaved sedges, arrowhead, or cattails are usually not dominant. Also, wet meadow and fen plants grow on peat or mineral soils rather than in standing water, as in marshes.

      Wet meadow and fen communities were common...

    • 17. Bedrock and Beach Communities
      (pp. 143-156)

      Bedrock and beach communities are sparsely vegetated communities that occur on cliffs, areas of bare rock, and lake and river beaches. The extreme environmental conditions of these places—such as thin, droughty soils or high rates of erosion or sedimentation—prevent the development of dense or long-lived vegetation. Instead, bedrock and beach communities tend to have a sparse cover of perennial plants that are adapted to repeated disturbance or to poor, droughty soils, or an ephemeral cover of annual plants that quickly colonize patches of newly exposed ground.

      Five bedrock and beach communities are present in the Region: moist cliff,...

    • 18. Aquatic Habitats
      (pp. 157-160)

      Aquatic habitats occur in lakes and rivers where there is permanent, usually deep, surface water. Although the variation may not always be readily apparent to the eye, the Region’s aquatic habitats vary greatly, much like the upland and wetland habitats described in previous chapters. Differences in features of the major landforms (see map 3) cause variation in water fertility, water clarity, and bottom texture among the Region’s rivers and (especially) lakes. In addition, there is variation within individual lakes and rivers in water depth, in the texture and composition of the bottom, in the availability of oxygen, in the slope...

    • Summary and Outlook
      (pp. 161-165)

      Landscapes and the habitats they contain change continuously under the influence of geologic processes, climate, and the plants and animals that live within them. The landscape and habitats of the St. Croix River Valley—Anoka Sandplain Region are no exception. Millions of years of change are recorded in the bedrock now underlying the Region. Evidence of tremendous glacial forces is recorded across the surface of the landscape. Layers of pollen and plant material in bog and lake sediments tell of changes in the vegetation over the past 12,000 years, from spruce parkland to prairie to woodland-brushland and deciduous forests. Accounts...

  7. PART III A Guide to Selected Sites in the Region

      (pp. 167-203)

      This guide and the accompanying maps highlight 35 sites where one can go to see some of the best examples of the native habitats in the Region. The landscape is constantly changing because of natural disturbances such as flooding or drought, natural processes of succession, and widespread human activity. Consequently, some of the site descriptions presented here will eventually become outdated. In addition, some habitats, such as maple-basswood forest, dry prairie, and mesic prairie, are not well represented in this guide because no large or high-quality examples occur on public land. Nevertheless, each of the places described here, even if...

  8. Appendix 1. County Checklist of Birds, Mammals, Amphibians, and Reptiles in the Region
    (pp. 205-214)
  9. Appendix 2. Sources of Additional Information
    (pp. 215-216)
  10. Glossary of Technical Terms
    (pp. 217-220)
  11. Bibliography
    (pp. 221-224)
  12. Index
    (pp. 225-234)
  13. Back Matter
    (pp. 235-237)