Photo by Emmet Judziewicz
State Rank: S2 Global Rank: GNR what are these ranks?
Steep clay bluffs border stretches of the Great Lakes shorelines and are less commonly found inland on the lower portions of streams draining into Lakes Superior and Michigan. These clay seepage bluffs are also called alkaline clay bluff. Vegetative cover can range from dense forests of red pine (Pinus resinosa), white pine (Pinus strobus), northern white-cedar (Thuja occidentalis), and paper birch (Betula papyrifera), to bare clay with only a few weedy herbs present. Buffalo-berry (Shepherdia canadensis) is a characteristic shrub, but more typically, alders (Alnus incana and A. viridis), as well as rank herbs such as Canada goldenrod (Solidago canadensis) and pearly everlasting (Anaphalis margaritacea) are dominant. Both native and exotic pioneers such as fireweed (Epilobium angustifolium) and Canada thistle (Cirsium arvense) are common, especially on the more unstable sites.
It is the semi-stabilized "weeping" bluffs that are of the greatest biological interest. Golden sedge (Carex aurea), gentians, orchids, and calciphilic fen species may colonize such sites, which can be local repositories of rare or otherwise noteworthy plant species.
Henry Chandler Cowles, regarded as the founder of plant ecology, studied this bluff environment at the end of the 19th century. He noted "there can be almost no other habitat in our climate which imposes such severe conditions upon vegetation as an eroding clay bluff." Temperature extremes, sun and wind exposure, and the variable consistency of clay soils (from mush to concrete as they dry) severely inhibit establishment by pioneer plants. During periods of erosion, Cowles felt "all vegetation is impossible."
The following Species of Greatest Conservation Need are listed according to their level of association with the Clay Seepage Bluff natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.
Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.
| Mammals | Score | |
|---|---|---|
| Big Brown Bat | Eptesicus fuscus | 1 |
| Little Brown Bat | Myotis lucifugus | 1 |
Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.
The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.
| Scientific Name | Common Name | Score |
|---|---|---|
| Astragalus neglectus | Cooper's Milkvetch | 2 |
| Packera indecora | Plains Ragwort | 2 |
| Parnassia palustris | Marsh Grass-of-Parnassus | 2 |
| Salix planifolia ssp. planifolia | Tea-leaved Willow | 1 |
| Trisetum melicoides | Purple False Oats | 1 |
| Trisetum spicatum | Spike Trisetum | 1 |
The following Ecological Landscapes have the best opportunities to manage for Clay Seepage Bluff, based on the Ecological Landscapes of Wisconsin Handbook.
| Ecological Landscape | Opportunity |
|---|---|
| Central Lake Michigan Coastal | Important |
| Northern Lake Michigan Coastal | Important |
| Southern Lake Michigan Coastal | Important |
| Superior Coastal Plain | Important |
Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.
Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.
Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.
Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.
Threats/issues and conservations actions for natural communities
The following are additional considerations for Clay Seepage Bluff in Ecological Landscapes with opportunities for protection, restoration, and/or management. For more information, see the Wildlife Action Plan.
Clay ravines that open to the Lake Michigan shore should be surveyed thoroughly to assess those sites that are most intact and support rare species. Fairy Chasm State Natural Area (Ozaukee County) and Fischer Creek State Recreation Area (Manitowoc County) contain examples of this community. Deer damage is severe in this Ecological Landscape and shoreline development limits conservation opportunities. The county management of one mile of state-owned shoreline near the mouth of Fischer Creek will potentially provide a good degree of protection to the bluffs at that site.
Opportunities are few here, scattered among privately owned, localized sites near lower Green Bay or along Lake Michigan.
Examples of alkaline clay bluff may be found in Milwaukee and Racine counties. Cliffside Park (Racine County) may be the best place to see the Lake Border moraines as they tower above the blue waters of Lake Michigan. Here the eroding clay bluffs are slowly entering the earliest stages of ravine formation, providing an opportunity to witness a dynamic landscape process in an urban area. Localized stretches of the clay bluffs in southern Milwaukee County (e.g., Warnimont Park) support rare plants.
Continuing interest in permanent and seasonal home development and other construction along the Lake Superior shoreline may pose a threat to this community here, but there are some protected examples on public lands near the City of Superior. Past logging practices have badly damaged many of the clay bluffs in this region, which still exhibit signs of severe disturbance.
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Semi-stable slumping clay bluffs can support unusual assemblages of vascular plants, mostly herbs of low stature and sometimes rare species.
Photo by Emmet Judziewicz.
Clay seepage bluff with bare soil and sparse vegetation above Fish Creek in Bayfield Co.
Photo by Ryan O'Connor.
Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.