Ecology and Physical Setting
Red Maple-Northern White Cedar Swamps are one of Vermont’s wetland treasures. The large, spectacular examples found in Cornwall Swamp, Salisbury Swamp, and the other swamp complexes in the Otter Creek floodplain are unmatched anywhere else in the region. Red Maple-Northern White Cedar Swamps occupy over 4,000 acres in the Otter Creek floodplain, with about 1,800 acres in Cornwall Swamp alone.
Red Maple-Northern White Cedar Swamps occur in areas of calcareous bedrock. They are primarily associated with the floodplains of larger rivers in the Champlain Valley, although examples also occur adjacent to Lake Champlain and the lower Black and Barton Rivers, and rarely in isolated basins. This natural community often occurs as part of a larger wetland complex and may grade into Northern White Cedar Swamp, Red Maple-Black Ash Seepage Swamp, or Maple-Green Ash Swamp.
Northern white cedar is not well adapted to extended periods of flooding. It occurs near the limits of flooding or in portions of swamp complexes that are flooded for shorter periods. Seasonal flooding may play a role in mineral enrichment of the large Red Maple-Northern White Cedar Swamps of river floodplains by depositing fine-textured alluvium that is rich in calcium. Groundwater discharge may also be responsible for providing mineral-rich water to these wetlands.
The organic soils of Red Maple-Northern White Cedar Swamps are permanently saturated, well-decomposed mucks with depths from five to over 16 feet. The shallow-rooted trees are susceptible to windthrow, which creates small canopy openings and microtopography. The resulting hollows and hummocks are well-developed, with hollows often large and water filled, and hummocks equally large and supporting most of the woody plant growth. Travelling through a Red Maple-Northern White Cedar Swamp often involves a series of precarious leaps from one hummock to the next.
Vegetation
Red Maple-Northern White Cedar Swamps are characterized by a tall, emergent tree layer of red maple and scattered white pine that extends above a shorter and more closed canopy dominated by northern white cedar, black ash, and red maple. Other tree species that vary in their abundance from swamp to swamp include yellow birch, paper birch, balsam fir, swamp white oak, red and black spruce, and tamarack. American elm is an occasional species that was likely much more common before Dutch elm disease became prevalent.
Shrubs are generally sparse. Sapling regeneration of cedar, red maple, and black ash can be common. The most frequently occurring shrubs are winterberry holly, dwarf raspberry, red-osier dogwood, and alder-leaved buckthorn, but poison sumac and the rare swamp fly honeysuckle are characteristic.
Herbs are also sparse because of the dense forest canopy and the abundance of water-filled hollows. Ferns are common, especially in the drier hollows. Typical species include royal fern, sensitive fern, cinnamon fern, and marsh fern. Other common herbs include Canada mayflower, northern bugleweed, fowl mannagrass, sarsaparilla, starflower, naked mitrewort, pedunculate sedge, goldthread, and bunchberry. The rare nodding trillium is characteristic of this community, though it is never abundant.
Bryophytes carpet large areas of the hummocks, but the hollows generally contain too much standing water to support bryophyte growth. The most abundant species on the hummocks are common fern moss, shaggy moss, and stair-step moss. On the edges of wet hollows, the mosses Calliergon cordifolium and Rhizomnium punctatum are common.
Wildlife Habitat
The large size, the seasonal flooding from associated rivers, the large pools, and the mix of cedar and hardwoods are defining factors for wildlife habitat in Red Maple-Northern White Cedar Swamps. Mink and wood turtle venture from riparian areas deep into these swamps in search of prey and plant foods. The cedar in the swamp canopy provides winter cover and food for white-tailed deer. Breeding birds include northern waterthrush, winter wren, veery, white-throated sparrow, Canada warbler, and great crested flycatcher. Examples of these swamps that are flooded in the spring, such as in the extensive Otter Creek floodplain, provide important staging areas for many species of migrating waterfowl. Red Maple-Northern White Cedar Swamps also provide habitat for two rare amphibians. The large pools provide breeding habitat for blue-spotted salamanders, and four-toed salamanders thrive and nest in the moist hummocks and hollows of sphagnum and other mosses.
Related Communities
- Northern White Cedar Swamps have a closed canopy of northern white cedar with few or no hardwood species present. They are closely associated with calcium-rich groundwater, and they do not flood.
- Red Maple-Black Ash Seepage Swamps have hardwood canopies and abundant groundwater seepage, and they do not flood. They are sometimes found in swamp complexes with Red Maple-Northern White Cedar Swamps.
Conservation Status and Management Considerations
The Champlain Valley and Lake Memphremagog lowlands, the two regions where this community is most common, have been largely converted to agricultural use. Wetlands, including some Red Maple-Northern White Cedar Swamps, were also cleared, ditched, and drained. Most of the remaining swamps have little if any upland forest buffer. Runoff from agricultural land carries excess nutrients that can degrade water quality and alter species composition. Restoration of forested buffers along swamps and feeder streams would help trap and filter nutrients, keeping them out of the wetland. Logging has been a historical use of many Red Maple-Northern White Cedar Swamps, both for cedar posts and for firewood. However, sustained heavy logging can alter surface water hydrology and stop the formation of hummocks and hollows associated with blowdowns of individual trees. Alterations to the flooding regimes of these swamps could dramatically shift species composition. Several examples are partially conserved. Additional conservation is needed to protect these valuable systems.
Distribution/Abundance 
Red Maple-Northern White Cedar Swamps occur primarily in the lowlands of western Vermont, although several examples have been identified in the northeastern portion of the state. Swamp communities of northern white cedar and hardwoods occur from northern Michigan to Maine, and in scattered locations south to Connecticut.
Characteristic Plants
Trees
Abundant Species
Red maple – Acer rubrum
Northern white cedar – Thuja occidentalis
Black ash – Fraxinus nigra
Occasional to Locally Abundant Species
Yellow birch – Betula alleghaniensis
White pine – Pinus strobus
Paper birch – Betula papyrifera
Balsam fir – Abies balsamea
Swamp white oak – Quercus bicolor
Red spruce – Picea rubens
Black spruce – Picea mariana
Tamarack – Larix laricina
American elm – Ulmus americana
Shrubs and Vines
Abundant Species
Winterberry holly – Ilex verticillata
Alder-leaved buckthorn – Rhamnus alnifolia
Poison sumac – Toxicodendron vernix
Occasional to Locally Abundant Species
Poison ivy – Toxicodendron radicans
Red-osier dogwood – Cornus sericea
Wild raisin – Viburnum nudum var. cassinoides
Labrador tea – Rhododendron groenlandicum
Highbush blueberry – Vaccinium corymbosum
Speckled alder – Alnus incana
Herbs
Abundant Species
Royal fern – Osmunda regalis
Sensitive fern – Onoclea sensibilis
Cinnamon fern – Osmundastrum cinnamomeum
Marsh fern – Thelypteris palustris
Canada mayflower – Maianthemum canadensis
Northern bugleweed – Lycopus uniflorus
Fowl mannagrass – Glyceria striata
Naked mitrewort – Mitella nuda
Dwarf raspberry – Rubus pubescens
Pedunculate sedge – Carex pedunculata
Goldthread – Coptis trifolia
Bunchberry – Cornus canadensis
Occasional to Locally Abundant Species
Crested wood fern – Dryopteris cristata
Tall meadow rue – Thalictrum pubescens
White turtlehead – Chelone glabra
Marsh bedstraw – Galium palustre
Three-seeded sedge – Carex trisperma
Bristle-stalked sedge – Carex leptalea
Two-seeded sedge – Carex disperma
Starflower – Lysimachia borealis
Sarsaparilla – Aralia nudicaulis
One-sided pyrola – Orthilia secunda
Hog-peanut – Amphicarpaea bracteata
Foamflower – Tiarella cordifolia
Bryophytes
Abundant Species
Common fern moss – Thuidium delicatulum
Stair-step moss – Hylocomium splendens
Shaggy moss – Rhytidiadelphus triquetrus
Moss – Calliergon cordifolium
Moss – Rhizomnium punctatum
Occasional to Locally Abundant Species
Schreber’s moss – Pleurozium schreberi
Moss – Sphagnum warnstorfii
Moss – Sphagnum centrale
Moss – Sphagnum girgensohnii
Tree moss – Climaceum dendroides
Three-lobed bazzania – Bazzania trilobata
Liverwort – Plagiochila porelloides
Rare and Uncommon Plants
Lily-leaved twayblade – Liparis lilifolia
White adder’s mouth – Malaxis monophyllos var. brachypoda
Ram’s head lady’s slipper – Cypripedium arietinum
Eastern Jacob’s-ladder – Polemonium vanbruntiae
Nodding trillium – Trillium cernuum
Swamp fly honeysuckle – Lonicera oblongifolia
Mountain fly honeysuckle – Lonicera villosa
Thin-flowered sedge – Carex tenuiflora
Green adder’s mouth – Malaxis unifolia
Yellow bartonia – Bartonia virginica
Small yellow lady’s slipper – Cypripedium parviflorum var. makasin
Showy lady’s slipper – Cypripedium reginae
Loesel’s twayblade – Liparis loeselii
Foxtail sedge – Carex alopecoidea
Davis’ sedge – Carex davisii
Associated Animals
Mink – Neovison vison
Masked shrew – Sorex cinereus
White-tailed deer – Odocoileus virginianus
Northern waterthrush – Parkesia noveboracensis
Winter wren – Troglodytes hiemalis
Brown creeper – Certhia americana
Veery – Catharus fuscescens
White-throated sparrow – Zonotrichia albicollis
Canada warbler – Cardellina canadensis
Great crested flycatcher – Myiarchus crinitus
Rare and Uncommon Animals
Blue-spotted salamander – Ambystoma laterale
Four-toed salamander – Hemidactylium scutatum
Wood turtle – Glyptemys insculpta
Red-shouldered hawk – Buteo lineatus
Places to Visit
Cornwall Swamp, Cornwall, Vermont Fish and Wildlife Department (VFWD) and The Nature Conservancy
Leicester Junction and Brandon Swamps, Brandon Swamp Wildlife Management Area, Brandon, VFWD
Tinmouth Channel Wildlife Management Area, Tinmouth, VFWD
South Bay Wildlife Management Area, Coventry, VFWD