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Maple-Green Ash Swamp

Ecology and Physical Setting illustration of maple green ash swamp

The rattling chorus of leopard frogs, tufts of fringed sedge arching above flooded hollows, and water-stained, buttressed tree trunks let you know you’re in a Maple-Green Ash Swamp. Most of these swamps are found in the Champlain Valley, where they mostly occur adjacent to Lake Champlain. They also occur in isolated depressions and in the floodplains of rivers like Otter Creek. The common hydrologic characteristics are extended spring flooding, and saturated soils during the remainder of the growing season. The soils of Maple-Green Ash Swamps are typically deep, well-decomposed organic deposits, but shallow organic and mineral soils are present in some areas. The ground surface in most of these swamps has distinct hummocks and water-filled hollows. 

Maple-Green Ash Swamps adjacent to Lake Champlain are typically located in former bays of the lake that are filled with organic soil deposits and are now separated from the lake by sand or shale berms. In these settings, deepwater marshes commonly occur lakeward of the forested swamp and may include scattered young trees. These pioneering young trees, as well as the larger, well-established trees on the lakeward side of the swamp may be killed by especially long duration spring or early summer flooding. It is common to see dead trees at the lower, lakeward limits of these swamps. Rising lake levels over the past century may partly explain this. Lakeside Floodplain Forests are commonly present on the slightly higher elevations and mineral soils landward of the swamps.

Along Otter Creek, Maple-Green Ash Swamps occur on deep organic soils that are within the active floodplain of the river. These swamps are adjacent to riverine floodplain forests, which occur on the alluvial soils of the river levees. Farther away from the river and at elevations that are flooded for shorter periods, the Maple-Green Ash Swamps may grade into Red Maple-Black Ash Seepage Swamps or Red Maple-Northern White Cedar Swamps. Maple-Green Ash Swamps also occur in isolated depressions underlain with fine-textured mineral soils that drain slowly. In such basins, spring runoff accumulates and standing water may be present for significant periods of the spring. This creates a flooding regime similar to that found in swamps adjacent to Lake Champlain or Otter Creek. These basins may have organic or mineral soils, depending on the duration of soil saturation. 

Vegetation 

The forest structure of Maple-Green Ash Swamps can resemble that of floodplain forests, especially when silver maple is the dominant tree and forms a high canopy of spreading crowns. In other cases, the canopy may be dominated by red maple and/or Freeman’s maple, a hybrid between the two soft maples. Green ash is an important component of the canopy in all sites and may dominate in some. Other trees include cottonwood, swamp white oak, yellow birch (on hummocks), slippery elm, American elm, and occasionally black ash.

maple green ash swampThe shrub layer is typically well developed. Along with seedlings and saplings of the overstory tree species, shrubs include winterberry holly, American black currant, silky dogwood, red-osier dogwood, poison sumac, highbush blueberry, and nannyberry. The herb layer is diverse and varies with the amount of microtopographic relief. The most common herbs are sensitive fern, fringed sedge, Tuckerman’s sedge, and hop sedge. Bryophytes are abundant and may form nearly continuous cover on hummocks, with sphagnum moss especially abundant.

Wildlife Habitat

Situated adjacent to Lake Champlain or in floodplains of larger rivers, Maple-Green Ash Swamps are near the permanent water needed for overwintering by northern leopard frogs and green frogs. Both frogs forage in these swamps, especially in the deeper pools. Leopard frogs breed in the standing water of deep pools. The rare blue-spotted salamander and four-toed salamander are found in the moist and mossy portions of these swamps, in areas with less flooding.

Mature swamps with large trees near the lake or a river are important for the cavity-nesting wood duck, hooded merganser, common merganser, and common goldeneye. Despite their name, common goldeneyes are rare breeders in Vermont. They are sensitive to human disturbance and their greatest breeding success has been in swamps and floodplains along the northern portion of Lake Champlain. Black-crowned night herons are rare colonial breeders in Vermont, nesting most often on Lake Champlain islands where there are no mammalian predators. These beautiful herons roost in trees and swamps near water and may be seen hunting for small fish, frogs, or other small aquatic animals in shallow waters. Other breeding birds of these swamps include northern waterthrush, yellow warbler, great crested flycatcher, and the rare blue-gray gnatcatcher and red-shouldered hawk.

Related Communities 

  • Red Maple-Black Ash Seepage Swamp is dominated by red maple and black ash, and typically lacks the silver maple and green ash found in Maple-Green Ash Swamps. Herbs and shrubs indicate groundwater seepage, the primary source of water in these swamps. There is little or no spring flooding.

     
  • Lakeside Floodplain Forest typically occurs at a slightly higher elevation, sometimes within the same former lake cove. Lakeside Floodplain Forests have mineral soils that are not saturated throughout the growing season.

Conservation Status and Management Considerations 

Most known examples of this rare community type are associated with Lake Champlain and Otter Creek. The flooding regimes of these water bodies shape the species composition and ecological characteristics of the swamps. In order to maintain these flooding regimes, the naturally-forming beach berms and river levees should be maintained or restored.    

Several Maple-Green Ash Swamps are protected on conserved lands.

Distribution/ Abundance map of Vermont with locations on natural community

Maple-Green Ash Swamps are known from the Champlain Valley, with similar communities described from New York. Closely related communities occur in southern New England.

Characteristic Plants

Trees 

Abundant Species

Red maple – Acer rubrum

Silver maple – Acer saccharinum

Green ash – Fraxinus pennsylvanica

Freeman’s maple – Acer ×freemanii

Occasional to Locally Abundant Species

Cottonwood – Populus deltoides

Yellow birch – Betula alleghaniensis

Slippery elm – Ulmus rubra

American elm – Ulmus americana

Swamp white oak – Quercus bicolor

Black ash – Fraxinus nigra

Bur Oak – Quercus macrocarpa

Shrubs and Vines

Abundant Species

Winterberry holly – Ilex verticillata

Occasional to Locally Abundant Species

American black currant – Ribes americanum

Silky dogwood – Cornus amomum

Red-osier dogwood – Cornus sericea

Poison sumac – Toxicodendron vernix

Highbush blueberry – Vaccinium corymbosum

Nannyberry – Viburnum lentago

Riverbank grape – Vitis riparia

Black elderberry – Sambucus nigra

Canada yew – Taxus canadensis

Herbs

Abundant Species

Sensitive fern – Onoclea sensibilis

Fringed sedge – Carex crinita

Occasional to Locally Abundant Species

Spotted touch-me-not – Impatiens capensis

Retrorse sedge – Carex retrorsa

Hop sedge – Carex lupulina

Tuckerman’s sedge – Carex tuckermanii

False nettle – Boehmeria cylindrica

Tall meadow rue – Thalictrum pubescens

Marsh fern – Thelypteris palustris

Cinnamon fern – Osmundastrum cinnamomeum

Bluejoint grass – Calamagrostis canadensis

Tufted loosestrife – Lysimachia thyrsiflora

Common beggar’s-ticks – Bidens frondosa

Nodding bur marigold – Bidens cernua

American water horehound – Lycopus americanus

Northern bugleweed – Lycopus uniflorus

Stout woodreed – Cinna arundinacea

Drooping bulrush – Scirpus pendulus

Rare and Uncommon Plants

Yellow water-crowfoot – Ranunculus flabellaris

Nodding trillium – Trillium cernuum

Gray’s sedge – Carex grayi

False hop sedge – Carex lupuliformis

Cyperus-like sedge – Carex pseudocyperus

Loesel’s twayblade – Liparis loeselii

Foxtail sedge – Carex alopecoidea

Cattail sedge – Carex typhina

Associated Animals

Gray treefrog – Hyla versicolor 

Northern leopard frog – Lithobates pipiens

Green frog – Lithobates clamitans

Northern waterthrush – Parkesia noveboracensis 

Yellow warbler – Setophaga petechia 

Great crested flycatcher – Myiarchus crinitus 

Veery – Catharus fuscescens 

Red-eyed vireo – Vireo olivaceus 

Wood duck – Aix sponsa 

Hooded merganser – Lophodytes cucullatus 

Common merganser – Mergus merganser 

Mallard – Anas platyrhynchos 

Rare and Uncommon Animals

Blue-spotted salamander – Ambystoma laterale

Four-toed salamander – Hemidactylium scutatum

Indiana bat – Myotis sodalis

Red-shouldered hawk – Buteo lineatus

Blue-gray gnatcatcher – Polioptila caerulea 

Black-crowned night-heron – Nycticorax nycticorax

Common goldeneye – Bucephala clangula 

Appalachian brown – Lethe appalachia

Places to Visit 

Mud Creek Wildlife Management Area, Alburgh, Vermont Fish and Wildlife Department (VFWD)



Alburgh Dunes State Park, Alburgh, Vermont Department of Forests, Parks, and Recreation (VDFPR)



North Hero State Park, North Hero, VDFPR 



Halfmoon Cove Wildlife Management Area, Colchester, VFWD



Cornwall Swamp, Cornwall and Whiting, VFWD and The Nature Conservancy



Rossetti Beach Natural Area, Colchester, Lake Champlain Land Trust