PROTECTING WISCONSIN'S BIODIVERSITY

 
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Northern Wet Forest

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Photo by Rich Staffen

 

Counties with Mapped NHI Occurrences

Northern wet forest encompasses a group of weakly minerotrophic to strongly acidic, conifer-dominated peatlands located mostly north of the Tension Zone. The dominant trees are black spruce (Picea mariana) and tamarack (Larix laricina). Jack pine (Pinus banksiana) is a significant component in parts of the type's range. This community is found primarily in kettle depressions or partially filled basins, on glacial outwash landforms, moraines, and till plains, where the water table is near the surface or where drainage is somewhat impeded. The community also occurs along the margins of lakes and low-gradient streams. On the wetter side of the moisture gradient, this community tends to grade into muskeg, open bog, or poor fen. On the drier side, the spruce-tamarack swamps may grade into nutrient-rich swamp forests of northern white-cedar (Thuja occidentalis) or black ash (Fraxinus nigra), if a source of nutrient-enriched groundwater is present. In much of the type's current range the adjacent uplands are still forested, most often with second-growth stands of northern hardwoods, pine, or aspen. A minerotrophic moat (or "lagg") may occur at the upland-wetland interface, and can support a diverse assemblage of tall shrubs, swamp hardwoods, and "rich" swamp conifers such as northern white-cedar.

Northern wet forests were widespread and relatively common historically, although due to the landforms with which they were associated, they did not typically occur in large patches in Wisconsin. Northern wet forests remain relatively common in much of their range today. WDNR's Natural Heritage Inventory (NHI) Program has split northern wet forest into two types (black spruce swamp and northern tamarack swamp, described below) to better reflect community variability. Community composition and water chemistry were used as the primary factors that differentiate the types. Because the NHI Program's older inventory information did not consider those factors when classifying coniferous wetlands, northern wet forest (Curtis 1959) has been retained as a type.

 
 
 
Key Environmental Factors

Black spruce swamp represents the more acid "bog" forests. The understory is characterized by a deep, continuous carpet of sphagnum mosses. Other representative plants include ericaceous shrubs such as leatherleaf (Chamaedaphne calyculata), Labrador-tea (Rhododendron groenlandicum), creeping snowberry (Gaultheria hispidula), small cranberry (Vaccinium oxycoccos), and herbs that are adapted to or tolerant of saturated substrates and high acidity, such as swamp false Solomon's-seal (Maianthemum racemosum), three-seeded bog sedge (Carex trisperma), and boreal bog sedge (Carex magellanica). A deep accumulation of Sphagnum mosses partially isolates the plant assemblage from the influence of mineral-enriched groundwater, limiting composition to a relatively small group of specialists, and also limiting the growth of trees. Black spruce swamp is widespread in much of northern Wisconsin, locally common in the central part of the state, and occurs in disjunct outliers as far south as Columbia and Ozaukee Counties.

Northern tamarack swamp is a less acid, wet conifer forest community that can support nutrient-demanding understory plants that are also tolerant of relatively high pH levels. Tamarack is the dominant tree, sometimes to the virtual exclusion of other tree species. In some stands, hardwoods such as paper birch (Betula papyrifera), red maple (Acer rubrum), black ash (Fraxinus nigra), and American elm (Ulmus americana) occur as canopy associates, saplings, or subcanopy trees. The understory may be more diverse and structurally complex than in the more acid spruce-dominated swamps, and sometimes features a well-developed tall shrub layer composed of plants with relatively high nutrient demands such as speckled alder (Alnus incana), alder-leaved buckthorn (Rhamnus alnifolia), mountain holly (Ilex mucronata), and common winterberry (Ilex verticillata). Ericaceous shrubs and many sedge species are usually present, and in the "poorer" swamps dominate their respective strata. The bryophytes may include more minerotrophic Sphagnum mosses, as well as additional genera of mosses that do not usually occur in the acid bog forests. Stands that receive groundwater seepage may support plants such as skunk-cabbage (Symplocarpus foetidus), marsh-marigold (Caltha palustris), cinnamon fern (Osmunda cinnamomea), and royal fern (Osmunda regalis).

Wildlife Action Plan

Species of Greatest Conservation Need (SGCN) are associated with habitats (or natural communities) and places on the landscape. Understanding relationships among SGCN, natural communities and ecological landscapes help us make decisions about issues affecting SGCN and their habitat and how to respond. Download the Wildlife Action Plan association score spreadsheet to explore rare species, natural communities and ecological landscape associations

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 Wisconsin Wildlife Action Plan because lack of information can threaten our ability to successfully preserve and care for natural resources.

For more information, contact

Ryan O'Connor
Conservation Biologist
tel:+1-608-354-2383