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SUB-SUBSECTIONS: None.

ELEVATION: 1,100 to 1,350 feet (335 to 411 m).

AREA: 7,530 square miles (19,510 sq km).

STATES: Minnesota.

CLIMATE: Total annual precipitation ranges from 21 inches in the west to 25 inches in the east; 40 to 50 percent occurs during the growing season (Hargrave 1992). Average annual snowfall is as light as 42 inches in the west and as heavy as 56 inches in the extreme east (Wendland et al. 1992). Growing season is short, from 98 to 111 days, and shortest near the eastern edge. Extreme minimum temperatures are -45½F (Reinke et al. 1993) or colder.

The Canadian Ecoregions Working Group (1989) maps climatic region LBst (Subhumid Transitional Low Boreal Ecoclimatic Region) as including the Glacial Lake Agassiz Lowland, on the basis of conifer dominance of both upland and lowlands. Based on the Canadian treatment, it may be justified to treat the North Shore (Superior) Highlands, the Border Lakes, the Littlefork-Vermilion Uplands, and the Agassiz Lowlands as yet another climatic region.

BEDROCK GEOLOGY: Glacial drift is shallowest at the northern and eastern edges of the lake plain, where bedrock is locally exposed (Olsen and Mossler 1982). At the western edge of the basin, where drift thicknesses are generally greatest, drift is as thick as 300 feet. The underlying bedrock is Precambrian (late Archean) in age, and includes gneiss, amphibolite, undifferentiated granite, and metamorphosed mafic to intermediate volcanic and sedimentary rocks. There are also iron formation, metasediments, and metamorphosed felsic volcanic rocks (Morey 1976).

LANDFORMS: The peatlands occupy a large glacial lake bed. The mineral substrate consists of calcareous silty till, locally with a thin veneer of lake sediments (Glaser et al. 1981, referencing Wright 1972). Sediments vary considerably in texture across the extensive lake bed. Sandy beach ridges are exposed throughout the subsection.

SOILS: Predominantly organic soils (University of Minnesota et al. 1980c, 1981b). A greater percentage of organic soils is in the center of the lake basin, with increased amounts of poorly drained mineral soils near the edges. In the northwestern portion of the basin, north of Upper Red Lake, the surface soils are often sandy; but these sandy soils are generally only 2 to 4 feet thick over loamy glacial till (University of Minnesota et al. 1980b). About 75 percent of the soils are peats in this part of the basin. In the northeastern portion of the basin (the Big Fork Area), clayey soils are more common (43 percent); organic soils make up about 32 percent and sands 18 percent of the soils (University of Minnesota et al. 1981b). As in the northwest, clays and loams underlie the sands at 2 to 4 feet.

Peat depths can exceed 15 feet (Heinselman 1963). See presettlement vegetation.

Soils are classified primarily as Hemists, Aqualfs, and Aquents (Anderson and Grigal 1984). Hemists occupy the center of the lake basin; Aqualfs and Aquents are along the margins of the basin.

PRESETTLEMENT VEGETATION: Marschner (1974) mapped much of the subsection as peatland, in which he included sedge fen, black spruce-sphagnum bog, and northern white-cedar and black ash swamp. Low moraines and beach ridges were dominated by jack pine forest or trembling aspen-paper birch forest.

Recent ecologists have classified the peatland as several distinct plant communities; the plant species present in each community reflect differences in water flow and water chemistry (Heinselman 1963, 1970; Glaser et al. 1981; Glaser 1983). Types of peatland described include raised bogs, patterned fen, as well as several bog, fen, and poor fen types. Heinselman describes several conifer-swamp types (1970).

Peat deposition began approximately 7,000 years ago in the western part of the basin, where peat deposits are now thickest, and expanded westward (Glaser et al. 1981). Many of the western deposits of sphagnum peat, only 1,000 to 2,000 years old, are relatively shallow. Spruce-fir and trembling aspen forests occupied the drier sand and gravel beach ridges and low ground-moraine ridges. Balsam fir was an overstory tree in these stands.

The stratigraphic record indicates that the peatlands supported forests in the past, but that with peat accumulation, muskeg is becoming the dominant vegetation (Heinselman 1963). This record details several changes in forest vegetation that correspond to climatic changes (Heinselman 1970).

NATURAL DISTURBANCE: Fire occurred on the peatlands. Insect infestations, such as spruce budworm, probably lead to fires. Water level fluctuations, caused both by short-term climatic changes and by beaver dams, probably contributed to tree mortality. Windthrow was common on the poorly drained mineral soils.

PRESENT VEGETATION AND LAND USE: Trembling (quaking) aspen is best developed as both forest stands and as individual trees in this subsection, and it has been heavily harvested for pulp (David Grigal, personal communication). Aspen is probably the best developed forest type on the uplands, and it probably was also common in the presettlement. Logging of conifer forests also occurred.

In the past, attempts were made to farm parts of the peatlands (Heinselman 1963). Ditches were dug along section lines, but were not effective.

High-quality examples of the following plant communities are represented in this subsection: black spruce bog, black spruce swamp, boreal hardwood-conifer forest, lowland hardwood forest, rich fen, tamarack swamp, northern white-cedar swamp, upland northern white-cedar forest, white pine forest.

RARE PLANT COMMUNITIES: None identified to date.

RARE PLANTS: All the rare species within this subsection have a northern, boreal distribution. Achillea sibirica (Siberian yarrow), Arethusa bulbosa (dragon's mouth), Cladium mariscoides (twig-rush), Cypripedium arietinum (ram's-head lady's-slipper), Drosera anglica (English sundew), Drosera linearis (linear-leaved sundew), Juncus stygius var. americanus (bog-rush), Nymphaea tetragona (small white water-lily), Ranunculus lapponicus (Lapland buttercup), Xyris montana (yellow-eyed grass).

RARE ANIMALS: Mammals: Synaptomys borealis (northern bog lemming); Birds: Ammodramus caudacutus (sharp-tailed sparrow), Charadrius melodus (piping plover), Coturnicops noveboracensis (yellow rail), Grus canadensis (sandhill crane).

NATURAL AREAS: Minnesota: State Natural Areas: Caldwell Brook Cedar Swamp, Gustafson's Camp, Lost River Peatland, Luxemberg Peatland, Mulligan Lake Peatland (Scientific and Natural Area), Myrtle Lake Peatland, North Black River Peatland, Pine and Curry Island, Pine Creek Peatland, Red Lake Peatland, South Black River Peatland, Sprague Creek Peatland, Winter Road Lake Peatland.

PUBLIC LAND MANAGERS: State Forests: Beltrami Island, Big Fork, Koochiching, Lake of the Woods, Lost River, Northwest Angle, Pine Island, Red Lake; Wildlife Management Areas: Border, Grygla, Red Lake, Roseau River, Thief Lake; National Forests: Chippewa.

CONSERVATION CONCERNS: Maintaining the protected peatlands and the quality of their watersheds is a priority. Glacial Lake Agassiz peatland and Lost Lake peatlands were identified as critical landscapes for biodiversity by the Minnesota Heritage Program.

BOUNDARIES: The western edge of the subsection includes shallow peatlands along the west side of Lower Red Lake. Further west, there are wet prairies, and the uplands contain bur oak as well as trembling aspen. In the east, the subsection meets the ground moraine of the Erskine moraine (Des Moines lobe).

Figure 35.—Subsection X.12: Winter Road Lake Peatland State Natural Area, Lake of the Woods County, Minnesota. Large patterned peatlands occupy the flat, poorly drained topography of Glacial Lake Agassiz. The wetter portions of the peatland, called flarks, are dominated by Carex lasiocarpa and other sedges, while the drier portions, called strings, are dominated by shrubs. Scattered small black spruce and tamarack occur within the peatland, often where there are low ridges of mineral soil. Minnesota Department of Natural Resources photo by B. Coffin.