Great Lakes Moist Sub-boreal Balsam Fir-Spruce Forest

This ecological system represents the mesic southern or subboreal eastern boreal forest, ranging from northwestern Ontario to eastern Canada's Atlantic provinces and extending into the U.S. in northeastern Minnesota, Isle Royale, and near-coastal areas of Lake Superior shores in northern Wisconsin and Michigan. The low-elevation forests are dominated by Picea glauca and Abies balsamea. Picea mariana is often present, along with occasional Pinus banksiana. Codominant boreal hardwoods include Populus tremuloides and Betula papyrifera. Northern hardwoods, such as Acer saccharum and Tilia americana are relatively minor. The shrub and herb layers are variable, decreasing as the percent conifer cover increases. Common shrub species include Acer spicatum, Alnus viridis, Corylus cornuta, Diervilla lonicera, and Lonicera canadensis. The moss layer ranges from discontinuous to continuous. These upland forests typically occur on loamy soils over bedrock in scoured bedrock uplands and loamy, rocky, or sandy soils on glacial moraines, till plains and outwash plains, and moisture conditions range from well-drained to somewhat poorly drained. Wetter sites may contain Alnus incana ssp. rugosa, Calamagrostis canadensis, and Equisetum spp. This is the matrix forest type in many parts of its range. This group may include earlier-successional patches, in which Populus spp. and Betula spp. are dominant or mixed with Picea and Abies, that will develop into spruce-fir forests. Blowdown with subsequent gap regeneration is the most frequent form of natural disturbance, with large-scale fires important at longer return intervals. Insect infestations, in particular by Choristoneura fumiferana (spruce budworm), also can impact this group.

Picea glauca typically dominates on drier sites or is codominant with Abies balsamea on more mesic sites. In some mesic to wet-mesic examples, Abies balsamea dominates. This group includes several successional stages, including earlier-successional patches in which Populus spp. and Betula spp. are dominant. Mid-successional stands often contain stands mixed with Picea and Abies, that will develop into spruce-fir forests. The shrub and herb layers are variable, decreasing as the percent conifer cover increases. Common shrub species include Acer spicatum, Corylus cornuta, Diervilla lonicera, and Lonicera canadensis. The composition and density of the herbaceous layer can vary among associations and location. Typically, Aralia nudicaulis, Eurybia macrophylla, Clintonia borealis, and Maianthemum canadense are common understory species. The moss layer ranges from discontinuous to continuous. Wetter sites may contain Alnus incana ssp. rugosa, Calamagrostis canadensis, and Equisetum spp. Additional diagnostic shrub and herb species of this subboreal type will be added through further analyses.

These upland forests typically occur on loamy soils over bedrock in scoured bedrock uplands and loamy, rocky, or sandy soils on glacial moraines, till plains and outwash plains (Minnesota DNR 2003). Moisture conditions range from well-drained to somewhat poorly drained. Climate typically is characterized by cool, even temperatures, shorter growing season, and deep and sometimes severe winter snowfall. In the southern part of their range in the Great Lakes states, they occur along northern Great Lakes shorelines and on islands in Lake Superior. Cold temperate to boreal. Soils are typically neutral to acidic, shallow sandy, sandy-loam, or loamy-sand. Some examples occur on heavier, mesic silty or clay loams that are more alkaline in nature. Along Great Lakes shorelines, these soils overlay limestone or volcanic bedrock.

These forests are affected by windthrow, insect defoliation, and infrequent fires. Forests closer to the Great Lakes shorelines occur on shallower soils and are more likely to experience more serious windthrow and snap-off of larger trees. Mammalian herbivory also can impact forest stands. Selective herbivory by white-tailed deer and moose (Alces americanus) can alter the composition and structure and favor browse-tolerant species such as Picea glauca. These forests typically regenerate from gap-phase dynamics.

This system ranges in Canada from northwestern Ontario (possibly eastern Manitoba) to eastern Canada's Atlantic provinces and extending into the U.S. in northeastern Minnesota, Isle Royale, and near-coastal areas of Lake Superior shores in northern Wisconsin and Michigan. Its range westward is marked by a shift towards greater Picea glauca dominance and lower Abies balsamea dominance.