Thunder River Swamp

State Natural Area (No. 488)

Location: Within the Chequamegon-Nicolet National Forest. Oconto County. T33N-R17E Sections 2, 10, 11, 14, 15. 638 acres.

Access: The site occupies 9 square miles in the northeast corner of Oconto County, approximately 4 miles north and 8 miles east of Lakewood, Wisconsin. From Highway 32 and County F in Lakewood, go east and north on County F 3.1 miles, then east on Smyth Road 4 miles, then north on Holt Ranch Road 0.7 miles, then east on Bucks Ranch Road 1 mile, then north on N. Fork Road 2.1 miles. Walk east into the site.

Description: The Thunder River Swamp complex contains both upland and lowland areas of exceptional quality. Three habitat types (PMV, ATM, and AQVib) are found within 260 acres of upland forest. One of the included stands contains minimally disturbed old growth white pine, and is a known nesting site for red-shouldered hawks and great blue heron. The high quality lowland swamps found here are mostly white cedar with smaller areas of mixed conifer swamp and alder thickets and support numerous rare plant species. The best quality cedar swamp is located at the south end of the complex, along the Thunder River. The canopy here is white cedar, with less understory balsam fir and black spruce than other areas. The groundlayer is especially diverse. The Thunder River and three unnamed creeks, with associated narrow riparian communities, occur along or within the swamps of the complex. One small stream begins with a large spring pond headwater and continues for a mile and a half, connecting with the North Fork of the Thunder River. Another connects with Caldron Falls Reservoir. Upland areas include both northern dry-mesic and northern mesic forest. The northern dry-mesic forest is dominated by white pine, sugar maple, and paper birch with red maple, and aspen. Also present is a northern mesic forest of paper birch, red oak, and sugar maple. Several large stands within this forest, typed as "cedar-aspen-paper birch", are a matrix of small conifer swamp and mixed upland hardwood areas. Thunder River Swamp is owned by the US Forest Service and was designated a State Natural Area in 2007.