General information

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

MLRA notes

Major Land Resource Area (MLRA): 091X–Wisconsin and Minnesota Sandy Outwash

The Wisconsin and Minnesota Sandy Outwash MLRA is the most extensive glacial outwash system in the northern half of Wisconsin. The total land area of the Wisconsin portion is just under 1.4 million acres (2,170 sq miles). The northern half is a former spillway for Glacial Lake Duluth. The flowing meltwater from the draining lake has left behind thick deposits of drift and carved a terraced river valley now occupied by the St. Croix and Bois Brule Rivers.

The northeastern section – the Bayfield hills – is a collapsed outwash plain where drift deposits are thick. Lacustrine materials from Glacial Lake Duluth line the northeastern tip. Moving southwest, the landscape transitions into a large pitted outwash plain. This is an area of extensive kettle holes, and, where the underlying till is less permeable, kettle lakes with some interspersed morainic hills and ridges. The glacial drift deposits are thinner in the southwestern section, although there is still no documented surface bedrock within this MLRA.

The St. Croix and Bois Brule rivers share a channel that lines much of the northwestern border of this MLRA. In some places, the underlying reddish-brown sandy loam till of the Copper Falls Formation is exposed along cut riverbanks, though most of it is covered by a mantle of outwash. Glacial lakes deposited pockets of fine-textured lacustrine materials, most of which were washed away or buried by glacial outwash and meltwater flowing through the channel. East of the channel, some of the silty and clayey lakebed deposits are found near the surface, where they impede drainage and contribute to the formation of extensive wetlands.

Historically, the area supported extensive jack pine (Pinus banksiana), scrub, and oak forests and barrens. The northern portion also supported stands of red pine (Pinus resinosa) and eastern white pine (Pinus strobus) as well. Marsh and sedge meadow, wet prairies, and lowland shrubs dominated the extensive wetland complexes in the southern tip of this MLRA (Finley, R., 1976).

Classification relationships

Relationship to Established Framework and Classification Systems:
Biophysical Settings (Landfire, 2014): This ES is largely mapped as Laurentian-Acadian Northern Hardwoods Forest and Eastern Cool Temperate Pasture and Hayland

Habitat Types of N. Wisconsin (Kotar, 2002): The sites of this ES keyed out to two habitat types: Acer rubrum/Vaccinium-Rubus pubescens (ArVRp); Acer saccharum/Athyrium (AAt)
WDNR Natural Communities (WDNR, 2015):

Hierarchical Framework Relationships:
Major Land Resource Area (MLRA): Wisconsin and Minnesota Sandy Outwash (91X)

USFS Subregions: Bayfield Sand Plains (212Ka)

Wisconsin DNR Ecological Landscapes: Northwest Sands

Ecological site concept

The Moist Clayey Lowland ecological site is found in the southern portion of MLRA 91X on outwash plains, lake plains, and ground moraines. These sites are characterized by very deep, somewhat poorly drained soils formed primarily in clayey lacustrine deposits. Sites have a sandy or loamy mantle on top of the clayey lacustrine deposits. Precipitation, runoff from adjacent uplands, and groundwater discharge are the primary sources of water. Soils range from strongly acid to slightly alkaline.

The parent materials of Moist Clayey Lowland sites were deposited by old glacial lakes, including Glacial Lake Grantsburg. Rushing meltwater from large, proglacial streams during and after Wisconsin’s more recent glaciation – including one that occupied today’s St. Croix River valley – eroded or capped most of the silty and clayey lacustrine materials from the glacial lakes. Moist Clayey Lowland sites are found in locations far enough from the river valleys of these old proglacial streams to have not been washed away or thickly-capped.

Moist Clayey Lowland sites have finer textures than Moist Sandy and Loamy Lowland sites. The finer texture often supports higher pH and available water capacity than sandy and loamy materials. The somewhat poor drainage differs this ecological site from other clayey sites.

Associated sites

Similar sites

Table 1. Dominant plant species