Natural Resources
Conservation Service
Ecological site F090BY001WI
Poor Fen
Last updated: 11/16/2023
Accessed: 11/13/2024
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): 090B–Central Wisconsin Thin Loess Dissected Till Plain
The Wisconsin and Minnesota Thin Loess MLRA, Northern and Southern Parts (90A and 90B) correspond closely to the North Central Forest and the Forest Transition Ecological Landscapes, respectively. Some of the following brief overview is borrowed from the Wisconsin Department of Natural Resources ecological landscape publications (2015).
The Wisconsin and Minnesota Thin Loess MLRA, Northern and Southern Parts (90A and 90B) is an extensive glacial landscape that comprised of over 11.1 million acres (17,370 sq mi) throughout central and northern Wisconsin – about 27% of the total land area in the state. This glacial landscape is comprised of a heterogenous mix of loess-capped ground moraines, end moraines with eskers and ice-walled lake plains, and pitted, unpitted, and collapsed outwash plains sometimes interspersed with drumlins from the Illinoian and Pre-Illinoian glaciations. The entire area has been glaciated and nearly all of it is underlain by dense glacial till that impedes drainage. An extensive morainal system – the Perkinstown end moraine – spans most of the width of northern Wisconsin and divides the Northern and Southern Parts of this large landscape. This moraine, which has been sliced by outwash in many places, marks the southernmost extent of the Wisconsin glaciation (Wisconsin’s most recent glacial advance).
North of the Perkinstown morainal system is a loess plain, with a loess mantle 6-24 inches thick. The northernmost edge of this landscape is an undulating till and outwash plain with materials deposited by the Chippewa Lobe. Drumlins are common in the northern and northeastern portions. The drumlins are oriented towards the southwest and formed during a glacial episode prior to the most recent glacial advance. Some are covered with glacial till. Pitted, unpitted, and collapsed outwash plains fill the spaces between drumlins. Detached from the major land mass to the northeast is the hummocky Hayward collapsed end moraines, where swamps, ice-walled lake plains, and eskers are common.
Most of the MLRA to the south of the Perkinstown morainal system is an extensive ground moraine with some proglacial stream features including pitted outwash plains, terraces, and fans. A layer of loess 6-47 inches thick covers much of the area. Like the Northern Part, all areas of the Southern Part of this MLRA were glaciated, although the southcentral portion is a relatively older till plain with materials from the Illinoian and pre-Illinoian glaciations, not the most recent Wisconsin glaciation. The landforms in the southcentral portion are highly variable. Much of the area topography is controlled by underlying bedrock. Sandstone outcrops and pediments can be found here. Some of the most southern portions of the MLRA are mixed glacial deposits and residuum.
The land surface of the southeastern portion was formed by many small glacial advances and retreats. Morainal ridges protrude through an erosional, pitted outwash-mantled surface. These parallel ridges run in a northeast to southwest orientation and are dissected by many steams.
The continental climate of this MLRA is typical of northcentral Wisconsin, with cold winters and warm summers. The southern boundary of this MLRA straddles Wisconsin’s Tension Zone, a zone of transition between Wisconsin’s northern and southern ecological landscapes. Historically, the mesic forests were dominated by eastern hemlock (Tsuga canadensis), sugar maple (Acer saccharum), and yellow birch (Betula alleghaniensis).
Classification relationships
Relationship to Established Framework and Classification Systems:
Wetland Forest Habitat Type Classification System for Northern Wisconsin (Kotar and Burger, 2017): All four visited sites in this ES keyed out to one habitat type: Picea mariana - Larix laricina [PmLLe]
Biophysical Settings (Landfire, 2014): Much of this site is mapped as Boreal Acidic Peatland Forest, Boreal Acidic Peatland Herbaceous, Boreal Acidic Peatland Shrubland, Central Interior and Appalachian Swamp Shrubland, and Laurentian-Acadian Alkaline Conifer-Hardwood Swamp Forest
WDNR Natural Communities (WDNR, 2015): This ES is most similar to the Black Spruce Swamp, Northern Wet Forest, and Northern Tamarack Swamp communities
Hierarchical Framework Relationships:
Major Land Resource Area (MLRA): Wisconsin and Minnesota Thin Loess and Till (Northern and Southern Parts - 90A and 90B)
USFS Subregions: St. Croix Moraine (212Qa), Hayward Stagnation Moraines (212Xf), Glidden Loamy Drift Plain (212Xa), Central-Northwest Wisconsin Loess Plains (212Xd), Perkinstown End Moraine (212Xe), Brule and Paint Rivers Drumlinized Ground Moraine (212Xc), Green Bay Lobe Stagnation Moraine (212Ta)
Small sections occur in Green Bay Lobe Stagnation Moraine (212Ta), Central Wisconsin Moraines and Outwash (222Kb), Bayfield Sand Plains (212Ka), Athelstane Sandy Outwash and Moraines (212Tc)
Wisconsin DNR Ecological Landscapes: North Central Forest, Forest Transition, Northwest Lowlands
Ecological site concept
The Poor fen ecological site is scattered throughout MLRA 90A and 90B in drainageways and depressions on moraines, outwash, lake, and till plains. These sites are characterized by very deep, very poorly drained soils formed in thick organic deposits underlain by glacial till, glacial outwash, or alluvium. Sites are subject to frequent ponding in the spring and fall. Soils remain saturated during the growing season and meet hydric soils requirements. Water is primarily received form precipitation and runoff from adjacent uplands with little groundwater discharge and stream inflow. Soils range from extremely acid to strongly acid.
Poor fen sites have low pH that differentiates it from Organic ecological sites. The low pH is caused by limited interaction with groundwater that may be enriched with carbonates. In addition, the groundwater discharging into Poor fen sites is likely passing through surrounding parent materials that are acidic (i.e. outwash sand). Sites that are acid bogs have very little interaction with groundwater and receive most of their water from precipitation and runoff from adjacent uplands, both of which tend to be quite acidic. The low pH limits vegetative growth.
Associated sites
F090BY005WI |
Wet Sandy Lowland Wet Sandy Lowland consist of deep sandy deposits derived from a mixture of outwash, alluvium, and lacustrine sources. They form in seasonally ponded depressions and are saturated long enough for hydric conditions to occur. Some sites are wetlands. These sites occur slightly higher on the drainage sequence than Poor fen sites. |
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F090BY009WI |
Moist Sandy Upland Moist Sandy Lowland primarily consist of deep, sandy deposits from outwash, alluvium, lacustrine, and till. They sandy deposits may have a loamy mantle or be underlain by loamy deposits. The finer materials can cause episaturation and allow the site to remain moist for some of the growing season. They are drier and occur higher on the drainage sequence than Poor fen sites. |
F090BY013WI |
Sandy Upland Sandy Upland consist of deep sandy and loamy deposits of outwash, alluvium, till, and residuum. Soils are primarily sand and loamy sand and have a seasonally high water table within 80 inches, though they don't remain saturated for extended periods. They are much drier and occur higher on the drainage sequence than Poor fen sites. |
F090BY019WI |
Dry Sandy Upland Dry Sandy Upland consist of primarily sandy deposits of various origin. Loamy deposits are also present in many soils. They may have a seasonally high water table within two meters of the surface, though they do not remain saturated for sustained periods. They are much drier and occur higher on the drainage sequence than Poor fen sites. |
Similar sites
F090BY002WI |
Mucky Swamp Like Poor fen sites, Mucky Swamp sites consist of herbaceous organic materials, sometimes with mineral soil contact. They are also very poorly drained, permanently saturated wetlands. Organic Nonacid sites are more alkaline than Poor fen sites because they receive more stream and groundwater. Additionally, adjacent sites may have more calcareous parent materials than those adjacent to Poor fen sites. These differences are reflected in the vegetative communities, with Organic Nonacid having improved growing conditions over Poor fen. |
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F090BY003WI |
Sandy Floodplain Sandy Floodplain sites are found exclusively on floodplains in sandy and sometimes silty alluvium. These sites are somewhat poorly to poorly drained and are subject to flooding. Some sites may be saturated for long enough for hydric conditions to occur. Unlike Poor fen sites, they receive most of their water from streamflow. They are much less acidic and slightly drier than Poor fen sites. Growing conditions are improved. |
F090BY005WI |
Wet Sandy Lowland Wet Sandy Lowland consist of deep sandy deposits derived from a mixture of outwash, alluvium, and lacustrine sources. They form in seasonally ponded depressions and are saturated long enough for hydric conditions to occur. These sights occupy slightly higher landscape positions than Poor fen sites. The vegetative communities they support are slightly drier and more nutrient-demanding than those supported by Poor fen sites. |
Table 1. Dominant plant species
Tree |
(1) Picea mariana |
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Shrub |
(1) Ledum groenlandicum |
Herbaceous |
(1) Sphagnum |
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