Natural Resources
Conservation Service
Ecological site F091XY006WI
Wet Clayey Lowland
Last updated: 9/27/2023
Accessed: 12/22/2024
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 Laurentian-Acadian Herbaceous Wetlands
Wetland Forest Habitat Type Classification System for N. Wisconsin (Kotar and Burger, 2017): The sites of this ES keyed out to one habitat type: Fraxinus nigra/Onoclea (FnOn)
WDNR Natural Communities (WDNR, 2015): This ES is most similar to Northern Hardwood Swamp described by the WDNR, but may coincide with and overlap some of the WDNR wetland communities in different states depending on past hydrology.
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
Wet Clayey Lowland sites are an uncommon site located in the southern portion of MLRA 91X in depressions and drainageways on lake plains and outwash plains. These sites are characterized by very deep, very poorly or poorly drained soils that formed primarily in clayey lacustrine. Some sites have stratified sandy and clayey lacustrine, and others have a sandy outwash mantle over the clayey lacustrine deposits. Sites are subject to occasional ponding. Soils remain saturated for long periods during the growing season and meet hydric soil requirements. Soils range from strongly acid to neutral.
The parent materials of Wet Clayey Lowlands 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. Wet Clayey Lowlands are found in locations far enough from the river valleys of these old proglacial streams to have not been washed away or capped.
Wet Clayey Lowland sites have finer textures than Wet Sandy and Loamy Lowland sites. These finer textures often provide higher pH and available water capacity than sandy and loamy materials.
Associated sites
| F091XY002WI |
Mucky Swamp Mucky Swamp sites consist of deep, highly decomposed organic matter, primarily of herbaceous origin. Some sites have mineral soil contact. They occur on drainageways, depressions, and floodplains that receive stream or groundwater discharge. They are very poorly drained and are neutral to strongly acid. They may be adjacent to Wet Clayey Lowland sites, occurring in wetter areas lower on the drainage sequence. |
|---|---|
| F091XY008WI |
Moist Clayey Lowland The soils within this site formed in a sandy outwash mantle over clayey lacustrine deposits over sandy lacustrine deposits, or loamy glaciofluvial deposits over clayey lacustrine deposits. Soils are very deep and are somewhat poorly drained. They occur in slightly drier areas higher on the drainage sequence than Wet Clayey Lowland sites. |
| F091XY013WI |
Clayey Upland These sites form in clayey lacustrine deposits, often with a sandy or loamy mantle. Soils are very deep and moderately well to well drained. They occur in drier areas higher on the drainage sequence than Wet Clayey Lowland sites. |
Similar sites
| F091XY002WI |
Mucky Swamp Mucky Swamp sites consist of deep, highly decomposed organic matter, primarily of herbaceous origin. Some sites have mineral soil contact. They occur on drainageways, depressions, and floodplains that receive stream or groundwater discharge. They are very poorly drained and are neutral to strongly acid. The vegetative communities found on Wet Clayey Lowland sites are sometimes also found on Mucky Swamp sites. |
|---|---|
| F091XY003WI |
Floodplain These sites occur in depressions and flats on floodplains. They form in sandy to silty alluvium and are somewhat poorly to very poorly drained. They are subject to flooding. The vegetative communities found on Wet Clayey Lowland sites are sometimes also found on frequently flooded Floodplain sites. |
| F091XY005WI |
Wet Sandy and Loamy Lowland These sites occur on depressions and drainageways on outwash plains and lake plains. They primarily form in sandy outwash are subject to some flooding. Soils are very deep and poorly or very poorly drained. They are saturated for much of the year. The vegetative communities found on Wet Clayey Lowland sites are sometimes also found on Wet Sandy and Loamy Lowland sites. |
Table 1. Dominant plant species
| Tree |
(1) Fraxinus nigra |
|---|---|
| Shrub |
(1) Alnus incana |
| Herbaceous |
(1) Carex |
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Ecosystem states
State 1 submodel, plant communities
| 1.1A | - | Large-scale canopy disturbance, mortality in canopy layer. |
|---|---|---|
| 1.1C | - | Large-scale natural disturbance or tree harvesting, causing swamping of the site. |
| 1.2A | - | Slow accumulation of living and dead sphagnum moss layer. |
| 1.2B | - | Large-scale natural disturbance or tree harvesting, causing swamping of the site. |
| 1.3A | - | Colonization by trees with tolerance for prolonged ponding. |