These forested wetland communities primarily occurs in the Central Sand Plains Ecological Landscape on the bed of Glacial Lake Wisconsin along the upper reaches of low gradient headwaters streams and at the wetland-upland interface on the margins of the large acid peatlands that are prominent features in central Wisconsin. Soils are peat over acidic sands. Small, disjunct white pine-red maple swamps can also occur rarely in other areas of the state in areas with similar soils and geology, such as on sandy glacial lake plains and outwash valleys.
As the name suggests, the canopy is dominated by eastern white pine (Pinus strobus) with a subcanopy of red maple (Acer rubrum). Yellow birch (Betula allegheniensis) and tamarack (Larix laricina) can also present in lesser amounts, though some sites grade into tamarack-dominated peatlands. Common understory shrubs are speckled alder (Alnus incana), common winterberry (Ilex verticillata), huckleberry (Gaylussacia baccata), and, in the low shrub layer, bristly dewberry (Rubus hispidus). In the ground layer, cinnamon fern (Osmunda cinnamomea) is often abundant. Other common herbaceous plants include skunk cabbage (Symplocarpus foetidus), gold thread (Coptis trifolia), starflower (Trientalis borealis), partridge berry (Mitella repens), Canada mayflower (Maianthemum canadense), and two disjuncts from the eastern United States, bog fern (Thelypteris simulata) and long sedge (Carex folliculata). Sphagnum mosses and liverworts are common and, in some sites, can form an almost continuous carpet over extensive areas.
Seepages and spring runs are often present in these swamps, providing important microhabitats for invertebrates, herptiles, and plants. This community occupies a landscape position between wet acid peatlands forested with tamarack and black spruce (Picea mariana), and dry, upland Central Sands pine-oak forests. Transitions to the upland forests can be abrupt, with a sudden shift in the dominance of understory composition of wetland shrubs, herbs, and mosses, to dominance by bracken fern (Pteridium aquilinum), blueberries (Vaccinium angustifolium and V. myrtilloides), and Pennsylvania sedge (Carex pensylvanica). White pine-red maple swamps support an unusual mix of faunal species with high conservation value (e.g., Red-shouldered Hawk, amphibians, reptiles, and many species of neotropical migrant birds) due in part to their spatially variable microsites, high levels of ground cover, connectivity between wetland and upland communities, and uncommon structural features including large conifers and coarse woody debris.
