The coniferous forest biome ranges from relatively flat lake plains and outwash plains in the west, to hillier moraines in the mid-section, with rugged, rocky outcrops abutting Lake Superior. Peatlands occur in huge areas across the western and central glacial lake plains. As elevation rises eastward, soils become thinner and bedrock outcrops more prominent. Here passing glaciers caught on rugged bedrock; ice blocks broke off and were abandoned to melt slowly beneath glacial till, forming many of our "10,000 lakes."
The Ecological Classification System classifies this biome on the basis of bedrock, glacial deposits, topography, climate, and plant communities. It identifies twelve subsections, or landscape areas, described in the following paragraphs.
The Agassiz Lowlands cover a flat, poorly drained portion of Glacial Lake Agassiz. Lake sediment slowly, thinly covered the glacial till, which was as deep as 300 feet on the western edge, but much thinner at the northern and eastern edges where bedrock is occasionally exposed. Till deposits made drainage slow and inefficient, and as the lake slowly receded, peat formed over nearly 75 percent of the lowland basin. Roughly half the annual precipitation occurs during the short growing season, 98 to 100 days in duration.
Presettlement peatland communities included sedge fen, black spruce-sphagnum bog, and white cedar-black ash swamp—all well adapted to the short growing season. Low moraines and beach ridges were dominated by jack pine forest or trembling aspen-paper birch forest. Currently forestry and recreation are the primary land uses; accordingly, conservation concerns include timber harvesting and maintenance of protected peatlands and their watershed quality. Today's SNA sites protect some of the world's finest peatlands.
This gently rolling lake plain serves as transition between the extremes to the west and east of its boundaries. Soils are of clayey till up to 300 feet thick, topped with mineral lake sediment from Glacial Lake Agassiz. Peatlands up to 15 feet thick occur here, as well as better drained organic soils. Drainage is better organized than in the Agassiz Lowlands, with major rivers and several large lakes having formed.
Presettlement communities included much aspen-birch, later to be dominated by conifers. Lowland communities included sedge fen, black spruce-sphagnum bog, and white cedar-black ash swamp. Along the low glacial moraines and beach ridges grew jack pine forest and trembling aspen-paper birch forests. Early agriculture and ditching attempts were abandoned, leaving recreation and logging (aspen) for pulp mills the most common land uses today. Conservation efforts focus on protection of peatlands and their watersheds.
Gently rolling lake and till plains make up this area, with bedrock 200 to 600 feet below the surface. Moraines, a lake plain, and an outwash plain are legacies from mid-to late-Wisconsin glaciation. Sandy to clay soils have formed in the lower areas, with rich loam on hillier terrain. Drainage generally is not well developed yet, but does include the Mississippi and two large lakes, Cass and Winnibigoshish.
Presettlement communities were primarily deciduous and coniferous: white pine and red pine grew on the moraines; jack pine on the outwash and lake plains; hardwoods, close to the large lakes; and either sedge meadows or swamp forests in the lowlands. Today, aspen is the most common tree species. Forestry is a primary land use, with tourism, recreation, and lake cabins also important. Conservation concerns focus on timber harvesting and water quality.
St. Louis Moraines
Rolling to steep slopes of glacial drift shape this landscape area. Bedrock 100 to 200 feet below is a mixture of granite, volcanic, and sedimentary-based formations. Most precipitation falls during the growing season of 111 to 131 days. The Mississippi River bisects the area, with other drainage provided by small, relatively short rivers and over 66 lakes.
Forests covered the area before European settlement. White pine and red pine forests occupied the steep moraines, with northern hardwoods, aspen-birch, and mixed hardwood-pine forests situated on gently sloped moraines. Kettles and other low-lying areas supported conifer swamp and bogs. ridges grew jack pine forest and trembling aspen-paper birch forests. Early agriculture and ditching attempts were abandoned, leaving recreation and logging (aspen) for pulp mills the most common land uses today. Conservation efforts focus on protection of peatlands and their watersheds.
Forestry and recreation are primary land uses today; timber harvesting and lakeshore development are two major conservation concerns for the area.
Pine Moraines & Outwash Plains
A delight for touring "glacial detectives," this landscape area is made up of end moraines, outwash plains, till plains, and drumlin fields. Bedrock lies 200 to 600 feet below the predominantly sandy soils. The northern portion has a drift of loamy soil. Iron formations occur at the southeastern edge, and marine sandstone and shale, in the southwest. Hundreds of lakes in this area boast surface areas of more than 160 acres, including Lake Itasca, headwaters of the Mississippi.
Before settlement, sandy soils favored forests of jack pine with northern pin oak, but aspen-pine and mixed hardwood-pine forests occurred where irregular topography and wetlands provided fire protection. While some agriculture is conducted in the west, today's primary land uses are forestry and tourism: summer vacation increases area populations by a factor of 10. Conservation concerns focus on forestry, lakeshore development, and water quality.
This level to gently rolling landscape includes the lake plain of Glacial Lake Upham and a flat till plain. Bedrock lies 100 to 300 feet below. Glacial lake sediments, ground moraine, and a few low drumlin ridges make up most soils, with extensive peat formations on poorly drained deposits. Level terrain allows several major rivers to meander extensively, and few lakes occur.
Presettlement communities included lowland conifers and hardwoods, with extensive sedge meadows in the lowlands; aspen-birch forests and conifer forests of white pine and red pine blanketed the uplands. Forestry is the primary land use today, with agriculture important in some areas of the lake plain. Tourism is limited to Sandy Lake. Timber harvesting and water quality issues dominate area conservation concerns.
Lakes and rocky ridges typify this landscape area, which includes part of the Boundary Waters Canoe Area. The area takes its name from the many large lakes—over 300 larger than 160 acres—scattered along the Minnesota-Canada border. Many rest in stream valleys enlarged long ago by passing glacial ice masses. Thin soils and glacially eroded bedrock mold irregular slopes, craggy outcrops—and Eagle Mountain, the highest point in Minnesota. Soils are mostly coarse and loamy, though sandy, clayish soils are found on the western portion.
Presettlement vegetation was primarily forest, including jack pine, white pine-red pine, and hardwood-conifer—all fire-dependent communities. White pine-red pine forests clustered around lakeshores, with jack pine forests filling in drier areas. These forest communities persist today in roughly the same distributions, relatively undisturbed by logging. Conservation concerns focus on high recreational use, timber harvesting, and mercury levels in lakes.
This slim but unique landscape area is dominated by the Giants Range, a granite ridge 200 to 400 feet high, thinly covered with glacial drift. Minnesota's three-way Continental Divide intersects the summit of this ridge. Just to the south lies an iron formation heavily mined in the mid-twentieth century. A variety of moraines, outwash plains, and sandy lake plains complete the landscape, along with over 35 lakes of 160 acres or more in surface area. Bedrock—gneiss, granite, volcanic and sedimentary rock—is exposed in end moraines and outwash plains, but otherwise covered by glacial drift ranging from very thin to over 100 feet deep. The growing season is 106 to 121 days, with annual precipitation evenly distributed.
White pine-red pine forest, aspen-birch forest, mixed hardwood-pine forest made up presettlement plant communities, with jack pine barrens on the uplands. Conifer bogs, swamps, and open bogs occupied wetlands. Forest management and recreation are the primary land uses today, and conservation efforts focus on timber harvesting and water quality.
A drumlin field dominates this landscape area. Drumlin ridges average about a mile long and a quarter-mile wide, extending 50 feet high. Upland soils are well drained, with gravelly, sandy loams. Between drumlins, poorly drained soils support either conifer swamps or bogs. Wetlands are larger and more common in the northeast, where headwaters for a number of rivers begin their southwesterly flow. Along the eastern edge of the area lie the excessively drained sands of an outwash plain, which historically supported white pine-red pine forest, jack pine forest, and aspen-birch forest, with small conifer bogs or swamps scattered in lower areas. The level outwash plain is broken only by steep slopes along the Cloquet River.
Much of this land today is in public ownership, with forestry the dominant land use. Upland sites support quaking aspen in mixed or fairly pure stands, with some balsam fir occurring as well. With extensive access to public lands, recreation and hunting are also popular. In the past, windthrow and forest fires along drumlin ridges were primary disturbances; today it's timber harvesting and water quality that dominate conservation efforts.
This landscape area runs along the North Shore of Lake Superior, which moderates area climate and drainage. Along the southern portion lies a clay lake plain thinly covered with till, leaving massive exposures of bedrock. Lakes are few, with only 20 larger than 160 acres. Many streams form in the highland, flow 10 to 15 miles to Lake Superior, and cascade to the Lake below. Precipitation is slightly more than surrounding landscape areas, with the lake effect producing about 10 inches more snow than just five miles inland. The growing season lakeside is about 10 days longer than at the same latitude just six miles inland.
Presettlement forests were of aspen-birch, white pine-red pine, mixed hardwood-pine, and conifer bogs and swamp. Mixed hardwood-pine forest with sugar maple grew along the clay lake plain, and mixed hardwood-pine followed the ridgetops within 6 to 10 miles of the shoreline. Today forestry, tourism, and mining are the primary land uses.
Glacial Lake Superior Plain
This tiny landscape area 400 feet above Lake Superior covers a boundary of the ancient Glacial Lake Superior and corresponds to a larger area in Wisconsin. Once a glacial lake bed, its 50- to 10-foot deep clay soil distinguishes it from surrounding areas. No lakes are found here; however, gently rolling topography gives way to many narrow, V-shaped river valleys up to 150 feet deep, heading into Lake Superior with their load of eroded sediment. Bedrock is a mix of sedimentary rock, sandstone, and shale rich in copper. The lake effect here produces up to 10 inches more snow than just five miles inland, and a growing season about 10 days longer.
Formerly covered entirely by forest, the area was described by early explorers as "pine flats" of hemlock, spruce, fir, cedar, and white pine. Today more yellow birch occurs here than in the rest of the state. Forestry and hunting-oriented recreation are the most important land uses, though significant portions are totally undeveloped. The outstanding trout population of the Nemadji River draws many fishing enthusiasts. Conservation efforts focus on timber harvesting and the maintenance of trout habitat.
Mille Lacs Uplands
Mille Lacs Lake is set amidst gently rolling till plains and drumlin fields. Drumlin ridges alternate with shallow peatlands south and southwest of Mille Lacs. One large end moraine formed the dam responsible for Mille Lacs, and in the northeast, another series of end moraines marks later activity by the Superior Lobe. Glacial drift lies 100 to 300 feet deep over bedrock, with dense till slowing water movement throughout the area. Extensive wetlands characterize this young drainage system, which has many rivers and 100 lakes over 160 acres, most on end moraines. The growing season varies significantly, ranging from 97 in the north to 135 days in the south.
Before settlement, maple-basswood forests grew along the south, with coniferous hardwood and mixed conifer-hardwood forests covering the rest. Peatlands communities included sedge-fen, black spruce-sphagnum, or white cedar-black ash. Today agriculture is conducted on the western and southern portions, with forestry and recreation in the central and eastern portions. Many of Pine County's heavy forests are undisturbed, though no large white pine stands remain: dense till limits root development to just 20 to 40 inches, subjecting larger trees to windthrow. Current concerns include heavy recreational use, timber harvesting, old-growth forests, and water quality.