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County Line Swamp

Back to Northern Lake Michigan

Counties: Oconto


County Line Swamp, 8 Nov. 2000. Black ash on border of Marinette and Oconto Counties. Photograph, E.J. Judziewicz.

Site Description

County Line Swamp is located on the border of Marinette and Oconto counties along the western shore of Green Bay. It is a large lacustrine swamp of considerable diversity. Topography is a controlling factor in determining natural community composition. Before heavy logging and extensive ditching took place, this swamp was dominated by cedar and tamarack. These disturbances and changes in the site's hydrology have facilitated the invasion of large areas by reed canary grass, glossy buckthorn and purple loosestrife.

Currently, most of the site is a mosaic of open-canopied wetlands dominated by various trees depending on the local conditions and historical disturbance. Dominants include small diameter black ash, alder, lake sedge and reed canary grass. There are hundreds of small "islands" of upland hardwoods (white birch, red maple, red oak and trembling aspen) in the swamp, presumably where sand is close to the surface and elevations are slightly higher than in the adjoining lowland forest. In the southernmost portion there are areas of more intact, maturing (4'-10') hardwood swamp dominated by black ash with cedar as a canopy associate and a brushy understory dominated by alder.

Given its large size and pivotal location, this site provides important habitat for a variety of species (especially birds) even though much of it has been highly disturbed. Despite limited inventory efforts, many rare animal and plant species are known from this site.

Additional Comments

Despite continued negative impacts from past disturbance, this site encompasses the largest stand of swamp hardwoods on either of Wisconsin's Great Lakes shorelines. Size, strategic location and the diverse biota present also contribute to its significance. County Line Swamp is a high priority for increased protection, restoration of diminished features, and more detailed inventory attention.

Text describing this site was published previously in a 2002 DNR publication entitled “A Data Compilation and Assessment of Coastal Wetlands of Wisconsin’s Great Lakes” by E.J. Epstein, A. Galvin and W.A. Smith.

NOAA logo Wisconsin Coastal Management Program logo This project was funded by the Wisconsin Coastal Management Program and the National Oceanic and Atmospheric Administration, Office of Ocean and Coastal Resource Management under the Coastal Zone Management Act.

Last revised: Wed, 20 Jun 2012 17:21:12 CDT