Shallow Emergent Marsh

Ecology and Physical Setting 

This is a broadly defined community type, including many herb-dominated wetlands that are seasonally flooded or saturated. Soils are variable but are mostly shallow mucks or mineral soils with a high organic content. Organic soil deposits are deep in some marshes. As the name implies, these marshes have shallow water, with rooted herbaceous plants emerging from the water. During spring flooding, water depths may be two feet or more, but water levels usually drop by summer, leaving only several inches of water or an exposed soil substrate for most of the growing season. When found in areas with calcareous bedrock, these marshes can be enriched, and can support some species more commonly associated with Rich Fens.

Shallow Emergent Marshes occur in a variety of physical settings and in association with many other wetland types. Along lake and pond shores they can form complex mosaics with other communities, including Deep Bulrush Marshes, Deep Broadleaf Marshes, Cattail Marshes, and Lakeside Buttonbush Swamps. In the floodplains of small streams, Shallow Emergent Marshes are commonly associated with Sedge Meadows, Alluvial Shrub Swamps, and Alder Swamps. Many of our beaver meadows are best classified as Shallow Emergent Marsh and, in these cases, may be in an early successional stage. Early-successional wetlands in abandoned agricultural land often resemble Shallow Emergent Marshes but may ultimately succeed to shrub or forested wetland types. 

Vegetation 

Shallow Emergent Marshes are dominated by a robust growth of grasses, sedges, and herbs. Scattered shrubs may be present but are not dominant. The physical structure of the vegetation and species composition vary from one marsh to another, resulting from differences in hydrology, available seed sources, and other factors. In most Shallow Emergent Marshes, the vegetation grows from low hummocks that barely rise above shallow water, although some plants, such as bur-reeds, are well adapted to growing in permanent shallow water. 

Dominant plants may include bluejoint grass, rice cutgrass, woolgrass, bur-reeds, sweet flag, and tussock sedge. Other common associates include Joe-pye weed, white boneset, blue vervain, flat-topped aster, white turtlehead, Canada mannagrass, and several species of sedges and rushes. Shrubs include meadowsweet, steeplebush, willows, and speckled alder. Scattered red maple saplings are probably the most common tree species present; they seldom reach maturity. 

With additional study of this broadly defined community type it may be possible to refine the classification into several more distinct natural community and successional types, based on vegetation dominants, hydrologic regime, and history of human disturbance. 

Wildlife Habitat

Shallow Emergent Marshes are very important for wildlife. But just as this community is variable in plant species composition, so is it variable in the wildlife habitat it provides. Two important factors affecting wildlife use are the depth and duration of standing water, and the juxtaposition of the Shallow Emergent Marsh with other wetland types and open water. Spring peepers and northern leopard frogs may be found in marshes with only seasonal flooding, while American bullfrogs and green frogs use marshes with permanent water. Muskrats may be found in marshes with more permanent water regimes, and beavers may build dams and lodges if there is an associated stream. Mink hunt along stream and lake shorelines and adjacent marshes for small mammals, small birds, frogs, and aquatic species. Red-winged blackbirds and swamp sparrows are common birds of Shallow Emergent Marshes. A group of species commonly called “marsh birds” nest and feed in these wetlands. These birds include Wilson’s snipe, Virginia rail, least bittern, American bittern, and sora. Shallow Emergent Marshes also provide nesting and feeding habitat for waterfowl, including mallard and blue-winged teal. Northern pike spawn in Shallow Emergent Marshes adjacent to Lake Champlain and other lakes.

The showy flowers in Shallow Emergent Marshes attract many fascinating insects. Harris’ checkerspot is a bright orange and brown butterfly always found near its host plant, flat-topped aster—a common species in Shallow Emergent Marshes. Taiga bluet, a damselfly, and belted whiteface, a dragonfly, are two common species found in grassy marshes and other open wetlands.

Related Communities 

• Sedge Meadow is dominated by one or more species of sedge and typically occurs on permanently saturated organic soils. 
   
• Cattail Marsh: Cattails are the dominant plants in these marshes. Cattail Marshes may have longer duration flooding than Shallow Emergent Marshes. 

Conservation Status and Management Considerations 

Shallow Emergent Marshes provide important wetland functions, and they need protection, both through regulation and through education. Many have been converted to agricultural uses or are used for pasture. Non-native invasive plants pose a particular threat to Shallow Emergent Marshes, which often have a history of natural or human disturbance. Purple loosestrife is common in this community, often becoming established in the disturbed soils of wet pastures and spreading to adjacent wetlands. The native strain of reed canary grass was once a component of this community, but today almost all the reed canary grass we see is of European origin. This European strain forms near monocultures in some marshes and produces a dense thatch that limits germination of other species. Research indicates that the ability of this strain to form monocultures is the result of its high genetic diversity (Lavergne and Molofsky 2007). 

Distribution/Abundance 

Shallow Emergent Marshes are found throughout Vermont, and similar communities occur across the Northeast and adjacent Canada.

Characteristic Plants

Shrubs

Occasional Species
Meadowsweet – Spiraea alba
Steeplebush – Spiraea tomentosa
Common pussy willow – Salix discolor
Bebb’s willow – Salix bebbiana
Speckled alder – Alnus incana
Red maple – Acer rubrum

Herbs

Abundant Species
Bluejoint grass – Calamagrostis canadensis
Rice cutgrass – Leersia oryzoides
Woolgrass – Scirpus cyperinus
Black-green bulrush – Scirpus atrovirens
Giant bur-reed – Sparganium eurycarpum
American bur-reed – Sparganium americanum
Tussock sedge – Carex stricta

Occasional to Locally Abundant Species

Joe-pye weed – Eutrochium maculatum
White boneset – Eupatorium perfoliatum
Blue vervain – Verbena hastata
Flat-topped aster – Doellingeria umbellata
Purple-stemmed aster – Symphyotrichum puniceum
White turtlehead – Chelone glabra
Canada mannagrass – Glyceria canadensis
Pointed broom sedge – Carex scoparia
Stipitate sedge – Carex stipata
Fox sedge – Carex vulpinoidea
Hoary sedge – Carex canescens
Bristly sedge – Carex comosa
Nodding bur marigold – Bidens cernua
Water horsetail – Equisetum fluviatile 
Common soft rush – Juncus effusus
Short-tailed rush – Juncus brevicaudatus
Canadian rush – Juncus canadensis
Sweet flag – Acorus calamus
Swamp candles – Lysimachia terrestris 
Swamp milkweed – Asclepias incarnata

Non-Native Invasive Plants

Reed canary grass – Phalaris arundinacea
Purple loosestrife – Lythrum salicaria
Flowering rush – Butomus umbellatus
Phragmites – Phragmites australis ssp. australis
Yellow iris – Iris pseudacorus

Rare and Uncommon Plants

Barbed-bristle bulrush – Scirpus ancistrochaetus
Mild water-pepper – Persicaria hydropiperoides
Tapering rush – Juncus acuminatus
Bristly crowfoot – Ranunculus pensylvanicus
Twig rush – Cladium mariscoides 
Cyperus-like sedge – Carex pseudocyperus

Associated Animals

Spring peeper – Pseudacris crucifer 
Gray treefrog – Hyla versicolor 
Northern leopard frog – Lithobates pipiens
American bullfrog – Lithobates catesbeianus 
Green frog – Lithobates clamitans
Painted turtle – Chrysemys picta
American beaver – Castor canadensis 
Muskrat – Ondatra zibethicus 
Mink – Neovison vison 
Meadow vole – Microtus pensylvanicus
Meadow jumping mouse – Zapus hudsonius
Red-winged blackbird – Agelaius phoeniceus 
Swamp sparrow – Melospiza georgiana 
Wilson’s snipe – Gallinago delicata 
Virginia rail – Rallus limicola 
Mallard – Anas platyrhynchos 
Northern pike – Esox lucius 
Harris’ checkerspot – Chlosyne harrisii
Taiga bluet – Coenagrion resolutum 
Belted whiteface – Leucorrhinia proxima

Rare and Uncommon Animals

Eastern ribbonsnake – Thamnophis sauritus
Common watersnake – Nerodia sipedon
Least bittern – Ixobrychus exilis
American bittern – Botaurus lentiginosus 
Sora – Porzana carolina 
Blue-winged teal – Anas discors 
Green-winged teal – Anas crecca 

Places to Visit 

Victory Basin Wildlife Management Area, Victory, Vermont Fish and Wildlife Department

Abbey Pond, Ripton, Green Mountain National Forest

Ethan Allen Homestead, Burlington, Winooski Valley Park District