Also known as forested ridge and swale, this community complex is closely associated with Great Lakes shorelines. Series of narrow sandy ridges alternate with low swales, parallel to the lakeshore. The vegetation on the dry ridges can vary from open herbaceous or shrub communities on the semi-stabilized dunes closest to the shoreline, to dry forests dominated by pines (Pinus spp.) and oaks (Quercus spp.) farther inland, to mixed mesophytic forests of northern hardwoods or hemlock-hardwoods farthest from the shore. In a few locations, some of the ridges may support a boreal forest association that includes pines, white spruce (Picea glauca), balsam fir (Abies balsamea), and paper birch (Betula papyrifera). This may be at least partially due to the influence of the Great Lakes on local climate, creating conditions that are relatively cool and moist during the growing season. For additional details on associated communities, see northern dry forest, northern dry-mesic forest, northern mesic forest, and Great Lakes dune.
Water depth is a controlling factor in the swales, which are typically deeper and more open near the shoreline, supporting marsh or sedge meadow communities. Farther away from the lake, an alder-dominated shrub community may develop, and still farther inland forested wetlands of swamp hardwoods, bog conifers, or northern white cedar (Thuja occidentalis) may be present. Only the deepest swales closest to the shore may be in contact with Great Lakes water. Most of the swales receive water via small streams or groundwater seepage from areas upslope. The wetland communities that might be part of this complex include submergent marsh, emergent marsh, interdunal wetland, alder thicket, northern wet forest, northern wet-mesic forest, and northern hardwood swamp.
In Wisconsin, this community complex is best developed along Lake Michigan. The parallel ridges and swales offer exceptionally complex and diverse habitats for wetland, upland, and Great Lakes shoreline plants, and support rich assemblages of amphibians, reptiles, and breeding and migrating birds. A few ridge and swale systems also occur on the Lake Superior coast.
