University of Minnesota
University of Minnesota
College of Biological Sciences
Mixed hardwood forest.Lowland hardwood forest.White Cedar trees.

Hardwood and conifer swamps

Swamps are tree or shrub dominated wetland. Woody plants stand upon deep black organic substrate with water-saturated soils, and have standing water throughout all or much of the growing season. On the open end such communities generally grade into fens or marshes, and on the dry end into lowland hardwood forest. Types in this category include White Cedar Swamp, Minerotrophic Tamarack Swamp, Black Ash Swamp, Mixed Hardwood Swamp, Alder Swamp and Mixed Shrub Swamp. These communities vary primarily in the dominants that are present. The groundlayers are similar and are characterized by ferns, sedges, grasses, and forbs that inhabit marshes and fens. Click for images of hardwood and conifer trees and common upland and lowland shrubs of Cedar Creek.

White Cedar Swamp

While White Cedar is a common tree in both shallow-soiled uplands and peaty lowlands of northern Minnesota, a White Cedar Swamp is a rare community this far south in Minnesota. The largest tracts of Thuja occidentalis (White Cedar) at Cedar Creek surround the knolls in the vicinity of Cedar Bog Lake. Other tracts can be found near Ice Lake and south of the Lab. At Cedar Creek they occur on firm, black, woody peat in the transition zone between uplands and lowlands. Young individuals are found invading adjacent wooded swamps. Athyrium angustum (Lady Fern) is a common fern and Gymnocarpium dryopteris (Oak Fern) a characteristic one. Characteristic forbs are Coptis groenlandica (Goldthread), Mitella nuda (Bishops Cap), and Arisaema triphyllum (Jack-in-the-Pulpit). Mosses and lichens are abundant. Scattered sphagnum hummocks and uprooted cedars provide refuges for such plants as Linnaea borealis (Twinflower) and Gaultheria hispidula (Creeping Snowberry). Several species of orchids (Platanthera spp, Cypripedium spp) also find this damp, shady habitat inviting. The intervening pools provide habitat for Calla palustris (Wild Calla), Menyanthes trifoliata (Buckbean), and Polygonum arifolium (Halberd-leaved Tearthumb).

White-tailed deer find the cedar swamp a good place to yard up during the winter. The cedars provide shelter and abundant winter browse. Snowshoe hares used to inhabit the cedar swamps of Cedar Creek. They all but disappeared in the mid 1970s. Bobcats were fairly common at that time.

Minerotrophic tamarack swamp

Larix laricina (Tamarack) is the dominant tree in this community. The Tamaracks sit upon a thick, black, organic substrate and are difficult to walk through because of dense sapling and shrub growth. Paper Birch, Yellow Birch, young White Cedar, White Pine, Red Maple may be present. Rhus vernix (Poison Sumac), Ilex verticillata (Winterberry), Alnus incana (Speckled Alder), Cornus stolonifera (Red Osier Dogwood), and Salix bebbiana (Bebb’s Willow) are common shrubs. Great Dismal Swamp is a large tract of minerotrophic tamarack swamp in North Section. Other tracts can be found along the creek, in Channel Marsh south of the Lab and in Bridge Marsh east of the Lab. The groundlayer is patchy and is dominated by a variety of sedges and grasses as well as such characteristic marshland forbs as Caltha palustris (Marsh marigold), Calla palustris (Wild Calla), and Lysimachia thrysiflora (Tufted Loosestrife).

Black Ash Swamp

Narrow bands of Black Ash Swamp fringe the white cedars around Cedar Bog Lake, the uplands of North Section, and smaller patches can be found south of the Lab along the fringes of Channel Marsh. They lie at the edge of wooded uplands and receive nutrient rich groundwater seepage. Substrate is water-saturated black organics. The dominant tree is Fraxinus nigra (Black Ash). Flowers of this ash frequently have gall like deformities caused by a mite. A characteristic though uncommon understory species at Cedar Creek is Symplocarpus foetidus (Skunk Cabbage).

Mixed hardwood swamp

Hardwood swamps at Cedar Creek are dominated by Red Maple, Yellow Birch, and Black Ash. A dominant tree of this community in the past was Ulmus americana (American Elm). Very few American Elms remain at Cedar Creek after the loss of most of these trees to Dutch Elm Disease in the 1970s and 1980s. Most occurrences of mixed hardwood swamp are along the margin of Cedar Creek and Norris Cabin Drainage. This community type is not very extensive and at Cedar Creek commonly grades into Alder Swamp.

Alder swamp

Alder swamps are dominated by the tall (ca.3-4 meter) shrub Alnus incana (Speckled Alder). A few stems of red maple, paper birch, black ash or red elm may poke up through the alder canopy. Below the alders are plants common to various wetland types—Marsh Marigold (Caltha palustris), Marsh fern (Thelypteris palustris), Lake sedge (Carex lacustris), Carex leptalea, Miterwort (Mitella nuda)—but no species that are especially unique to this community. Depending on water level changes, this community seems to be able to shift readily toward sedge fen (wetter) or mixed hardwood swamp (drier).

Mixed shrub swamp

This wooded wetland community is dominated by Cornus stolonifera (Red-osier Dogwood), Salix discolor (Pussy Willow), Salix bebbiana (Bebb’s Willow), and Rhus vernix (Poison Sumac). These generally grade into sedge fens, alder or tamarack swamps. The most extensive tracts occur along the margins of Cedar Creek, Ice Lake Drainage, Fish Lake Drainage, and in Channel Marsh south of the Lab. These habitats are rather inhospitable. The shrubby component though low growing (ca 1-2 meters in height) can be so dense as to be almost impenetrable. Travel difficulties are compounded by standing water and the tussocky uneven nature of the terrain. The best time to visit is late winter, skiing atop a crust of snow. One is not bothered by hordes of biting flies; but it is rather difficult to develop a floral list at this time. Typha latifolia (Cattail), Phragmites australis (Tall Reed Grass), and Carex stricta (Tussock Sedge) are three of the more noticeable graminoid elements.