hrub Swamps are common in Vermont but are extremely variable. Shrubs are perennial woody plants that are generally less than 20 feet tall and have multiple S stems and branches low on the stem. Shrub swamps have more than 25 percent shrub cover and generally little or no tree cover. The variability of shrub swamps in Vermont is caused by many factors, including climate, hydrologic regime, degree of mineral enrichment from surface or groundwater, and past land use. Of these factors, human land use may most complicate our under- standing of the current condition and potential successional trends of particular shrub swamp types. It seems clear that some of our shrub-dominated swamp communities, such as Buttonbush Swamps and Sweet Gale Shoreline Swamps, are strongly controlled by flooding. They will likely persist for centuries in the absence of catastrophic distur- bance events. Although some of our alder-dominated swamps may persist for decades or centuries, it seems equally clear that many will succeed to forested wetland over relatively short periods. Many of our alder-dominated wetlands have had past agricul- tural uses.
HOW TO IDENTIFY Shrub Swamp Natural Communities Read the short descriptions that follow and choose the community that fits best. Then go to the page indicated and read the full community profile to confirm your decision. Alluvial Shrub Swamp: A swamp with mineral, alluvial soils found in the flood- plains of small rivers. Speckled alder is dominant, but black willow trees are abundant in some sites. Characteristic herbs include ostrich fern, riverbank wild-rye, Virginia wild-rye, and wild cucumber. Go to page 376. Alder Swamp: Speckled alder is typically dominant, or at least present in these common swamps found throughout the state. They have organic or organic-rich mineral soils that remain saturated for much of the year. Go to page 379. Sweet Gale Shoreline Swamp: A common swamp on peaty shores of small ponds and along the edges of slowly moving streams. The substrate is a mat of sedgy peat and roots, commonly floating in shallow water. Sweet gale, meadow-sweet, leatherleaf, and hairy-fruited sedge are common. Go to page 382. Buttonbush Swamp: A swamp dominated by buttonbush occurring either adjacent to large lakes as part of deep marsh wetland complexes or in isolated depressions. The organic soils are saturated throughout the year and typically flooded in the spring and early summer. Go to page 384.
ShrubIntroduction Swamps / 375 ALLUVIAL SHRUB SWAMP
ECOLOGY AND PHYSICAL SETTING Alluvial Shrub Swamps are common in the floodplains of many of our smaller rivers and streams. These floodplains are inundated by overbank stream flows at least once per year. This high flood frequency is partly responsible for the long-term maintenance of a shrub-dominated community that can tolerate repeated inundation during the growing season. There are few tree species that can tolerate this type of stress. The alluvial soils of this community are typically sandy or silty loams and are deposited by flood waters as they slow down and lose energy when they expand into the flat floodplains. The majority of this alluvial deposition occurs directly adjacent to the top of the stream bank, with less deposition farther from the stream channel. The typical result of this alluvial process is the formation of a narrow, DISTRIBUTION/ABUNDANCE raised levee at the top of the bank, with gentle slopes Alluvial Shrub Swamps downward tilting away from the river. These soils do not occur on smaller rivers have distinct horizon development due to the frequent throughout Vermont. These addition of alluvium. Alluvial Shrub Swamps commonly and related communities are found across the eastern grade into alder swamps, sedge meadows, or marshes that United States and Canada. may occur on soils with a greater organic content farther from the river. These adjacent wetland types may receive some alluvial deposition, but alluvium does not dominate soil formation as it does in the Alluvial Shrub Swamp. Alluvial Shrub Swamps may also grade into floodplain forests, to which they may succeed over time. As with all floodplain communities, the river or stream is the dominant force in natural disturbance. The stream channel migrates across the floodplain over time, eroding soils and vegetation in one area and depositing soils in another. Unusually long duration flooding may kill even the tolerant alders and willows that dominate this community.
376 / Wetland, Woodland, Wildland ALLUVIAL SHRUB SWAMP
Beaver may create temporary impound- These swamps also provide important ments and cut substantial amounts of habitat and cover for river otter, mink, woody vegetation for food and dam muskrat, and beaver. Wood turtles may use construction. this community and grassy openings within it, along with the associated stream and VEGETATION nearby uplands. This community is typically dominated by speckled alder, which grows as scattered VARIANTS plants or forms dense thickets and reaches This is a broadly defined community heights of 10 to 12 feet. In some examples, with no variants recognized at this time. black willow may be dominant and form an open canopy (less than 60 percent cover) RELATED COMMUNITIES up to 50 feet tall. It is common to see Riverine Floodplain Forest: Alluvial scattered black willow trees over an Shrub Swamps share many similarities with alder-dominated shrub layer. Boxelder Riverine Floodplain Forests. The several may also be types of present, as floodplain may species forest all have of shrub a more closed willows. The canopy and climbing vine, typically are virgin’s bower, not flooded as is commonly frequently as present. the Alluvial The Shrub Swamps. herbaceous Alder layer of Swamp: Alder Alluvial Shrub Swamps Swamps has typically have many organic or similarities organic-rich with some mineral soils floodplain Wood turtles feed in grassy openings of Alluvial Shrub Swamps. that remain forests. saturated for Several species that are highly characteristic much of the year, whereas soils of Alluvial of floodplains occur in this community, Shrub Swamps may dry out considerably including ostrich fern, riverbank wild-rye, between flooding events. Virginia wild-rye, and wild cucumber. Other common herbs include tall meadow rue, CONSERVATION STATUS AND Jack-in-the-pulpit, Joe-pye weed, and MANAGEMENT CONSIDERATIONS several species of asters and goldenrods. Streamside wetlands and riparian areas Bryophytes are typically sparse or absent are very important movement corridors for due to the annual deposition of alluvial many wildlife species. Although most soils. riparian wetlands such as Alluvial Shrub Swamps are protected by State and Federal ANIMALS wetland regulations, continued fragmenta- Alluvial Shrub Swamps provide impor- tion of these wetlands and corridors tant breeding habitat for many species of threatens the long-term integrity of terres- migratory birds, including alder flycatcher, trial and aquatic wildlife populations. veery, gray catbird, common yellowthroat, Agriculture in Vermont’s smaller river yellow warbler, and Wilson’s warbler (rare). valleys has eliminated many floodplain Green heron may use Alluvial Shrub communities, including Alluvial Shrub Swamps, along with streamside marshes. Swamps.
Shrub SwampsProfile / 377 ALLUVIAL SHRUB SWAMP
PLACES TO VISIT CHARACTERISTIC PLANTS Wenlock Wildlife Management Area, Ferdinand, Vermont Department of Fish TREES and Wildlife (VDFW) Occasional to Locally Abundant Species Victory Basin Wildlife Management Area, Black willow – Salix nigra Victory, VDFW Boxelder – Acer negundo South Bay Wildlife Management Area, SHRUBS AND VINES Coventry, VDFW Abundant Species Nulhegan Basin, Lewis, U.S. Fish and Speckled alder – Alnus incana Wildlife Service Occasional to Locally Abundant Species Willows – Salix spp. Virgin’s bower – Clematis virginiana Meadow-sweet – Spiraea alba var. latifolia
HERBS Abundant Species Ostrich fern – Matteuccia struthiopteris Occasional to Locally Abundant Species Riverbank wild-rye – Elymus riparius Virginia wild-rye – Elymus virginicus Wild cucumber – Echinocystis lobata Tall meadow rue – Thalictrum pubescens Jack-in-the-pulpit – Arisaema triphyllum Joe-pye weed – Eupatorium maculatum Flat-topped aster – Aster umbellatus Purple-stemmed aster – Aster puniceus Rough-stemmed goldenrod – Solidago rugosa Late goldenrod – Solidago gigantea Bluejoint grass – Calamagrostis canadensis
INVASIVE EXOTIC PLANTS Goutweed – Aegopodium podagraria Japanese knotweed – Polygonum cuspidatum Moneywort – Lysimachia nummularia
RARE PLANTS Auricled twayblade – Listera auriculata Wild garlic – Allium canadense
378 / Wetland, Woodland, Wildland ALDER SWAMP
ECOLOGY AND PHYSICAL SETTING This is our most common shrub-dominated wetland. Alder Swamps vary in size from less than one acre to over 1,000 acres. This community is very broadly defined and includes a substantial amount of variability. Additional study of these wetlands is needed. Alder Swamps occur in a variety of physical settings, including the margins of lakes and ponds, poorly drained depressions and basins, and in the backwater floodplains of rivers and streams. The soils of Alder Swamps are generally saturated throughout the growing season and experience some degree of seasonal flooding. In some situations, they are permanently flooded, with the majority of the woody vegetation growing on drier hummocks. The soils vary from deep organic muck deposits in some of the wettest swamps to mineral soils with a high organic content in the driest DISTRIBUTION/ABUNDANCE swamps, depending largely on the permanence of soil This common community saturation or inundation. occurs throughout Vermont Alder Swamps commonly occur in association with other and eastern North America. wetland types, including Alluvial Shrub Swamps, Sedge Meadows, marshes, and beaver-influenced wetlands. The narrow, wet lagg zone adjacent to peatlands is also com- monly an alder-dominated swamp. Some Alder Swamps may succeed to forested wetland communities over time, whereas others may be more stable. The stability of shrub dominance in a particular swamp is probably closely related to the hydrologic regime of the wetland. Long duration or frequent flooding will favor the more tolerant shrub species and tend to prevent most tree species from maturing. It may also be difficult for tree seedlings to penetrate the dense shrub canopy of many shrub swamps, thereby delaying succession to forested
Shrub SwampsProfile / 379 ALDER SWAMP
An extensive Alder Swamp along the meandering Nulhegan River. wetlands. Human land use history, includ- sedge, bluejoint grass, long-haired sedge, ing the type of agricultural use and the time Canada mannagrass, fowl mannagrass, of abandonment, may be very important purple-stemmed aster, cinnamon fern, clues in developing an understanding of sensitive fern, and Joe-pye weed. Sphag- successional trends for individual Alder num moss, other mosses, and liverworts Swamps. may be abundant in some swamps but others swamps may have few bryophytes. VEGETATION The bryophytes of Alder Swamps need In most Alder Swamps, speckled alder is additional study. the dominant tall shrub, often forming dense, nearly impenetrable thickets. Other ANIMALS common shrubs that may be present in Alder Swamps may provide important varying amounts include shrub willows, breeding habitat for many species of dogwoods, wild raisin, northern arrow- migratory birds, including alder flycatcher, wood, and sapling red maple. In warmer swamp sparrow, veery, gray catbird, regions of Vermont, other shrubs may common yellowthroat, yellow warbler, and become abundant in these swamps, American woodcock. Beaver, snowshoe including highbush blueberry, spicebush, hare, and star-nosed mole may all be found and poison sumac. In Alder Swamps that in shrub swamps. Spotted salamander, receive calcareous groundwater enrich- wood frog, and gray treefrog are commonly ment, species such as alder-leaved buck- encountered amphibians. thorn, shrubby cinquefoil, and red-osier dogwood may be present. VARIANTS Common herbs in Alder Swamps are as This is a broadly defined community variable as the swamps themselves, but a with no variants recognized at this time. few ubiquitous species include tussock
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RELATED COMMUNITIES CHARACTERISTIC PLANTS Alluvial Shrub Swamp: This commu- nity is also dominated by speckled SHRUBS alder but has mineral alluvial soils and Abundant Species herbaceous species such as ostrich fern Speckled alder – Alnus incana and wild-ryes that are characteristic of Occasional to Locally Abundant Species floodplains. Common pussy willow – Salix discolor Silky willow – Salix sericea Bebb’s willow – Salix bebbiana CONSERVATION STATUS AND Woolly-headed willow – Salix eriocephala MANAGEMENT CONSIDERATIONS Black willow – Salix nigra Alteration of the natural hydrologic Red-osier dogwood – Cornus sericea regime is probably the greatest threat to Silky dogwood – Cornus amomum this wetland type. Construction of artificial Wild raisin – Viburnum nudum var. cassinoides impoundments and ponds affect many Red maple – Acer rubrum Alder Swamps, resulting in a loss of shrub Northern arrowwood – Viburnum dentatum habitat for wildlife. As some shrub swamps var. lucidulum are successional communities on wet, Smooth alder – Alnus serrulata abandoned agricultural land, there may Highbush blueberry – Vaccinium corymbosum be a decline in the abundance of Alder Spicebush – Lindera bezoin Swamps as these areas become forested Maleberry – Lyonia ligustrina over time. Alder Swamps are also created Poison sumac – Toxicodendron vernix as part of the cycle in beaver wetlands. Alder-leaved buckthorn – Rhamnus alnifolia Shrubby cinquefoil – Potentilla fruticosa
PLACES TO VISIT HERBS Halfmoon Cove, Colchester, Vermont Occasional to Locally Abundant Species Department of Fish and Wildlife (VDFW) Tussock sedge – Carex stricta Wenlock Wildlife Management Area, Drooping sedge – Carex crinita Ferdinand, VDFW Bluejoint grass – Calamagrostis canadensis Victory Basin Wildlife Management Area, Canada mannagrass – Glyceria canadensis Victory, VDFW Fowl mannagrass – Glyceria striata Purple-stemmed aster – Aster puniceus Rock River Wildlife Management Area, Cinnamon fern – Osmunda cinnamomea Highgate, VDFW Sensitive fern – Onoclea sensibilis Nulhegan Basin, Lewis, U.S. Fish and Joe-pye weed – Eupatorium maculatum Wildlife Service RARE AND UNCOMMON PLANTS Auricled twayblade – Listera auriculata
Shrub SwampsProfile / 381 SWEET GALE SHORELINE SWAMP
ECOLOGY AND PHYSICAL SETTING Sweet Gale Shoreline Swamps are common along the peaty shores of small ponds and along the edges of slowly moving streams. This type of shrub swamp typically grows as a floating mat of vegetation that extends over pond or stream waters, although in some cases the vegetation is rooted in a mineral substrate. A pioneering community, Sweet Gale Shoreline Swamp is frequently a narrow zone between open water and other wetland types – often peatlands – land- ward. In many swamps, the substrate is a permanently saturated sedgy peat, supported and held together by the network of shrub roots and sedge rhi- zomes. Near the water’s edge, this fibrous, floating matrix may not be strong enough to support a person, but further back from the open water the peat is more likely to be grounded and safe for tentative, exploratory steps. This community is probably best viewed from a canoe. Although sweet gale itself is commonly associated with calcium-rich wetland habitats, including fens, Sweet Gale Shoreline Swamps can occur in non- calcareous bedrock areas as well. This apparent contradiction may be explained in part by the relative availability of calcium and other dissolved minerals in this particular shoreline habitat. Even low concentrations of dissolved minerals in streams and ponds provide an DISTRIBUTION/ undepletable supply for those plants ABUNDANCE whose roots are in contact with Sweet Gale the water. Shoreline Swamps Beaver impoundments are the most are most common common form of natural disturbance to in northeastern Vermont but do this community. occur elsewhere. This community is VEGETATION found throughout This shrub swamp community is all the northern dominated by sweet gale, but speckled New England states. alder and meadow-sweet may also be common. Leatherleaf is a common assoc- iate and may dominate in especially boggy conditions or on the margins of more acid surface waters. In more mineral-rich shoreline habitats, stunted northern white cedar saplings may be present. Red maple saplings are common in low abundance.
382 / Wetland, Woodland, Wildland SWEET GALE SHORELINE SWAMP
Sedges are abundant, especially hairy- with calcareous groundwater seepage. They fruited sedge and tussock sedge. Other may also occur as pioneering mats along common herbs include bluejoint grass, pond shores. In these cases, Intermediate marsh cinquefoil, swamp candles, marsh Fens are distinguished from Sweet Gale St. John’s-wort, and common cattail. The Shoreline Swamps by the lack of shrub bryophyte component of this community dominance and flooding that is less frequent needs additional study, but commonly and of shorter duration. includes Sphagnum teres, Sphagnum subsecundum, and Calliergon stramineum. CONSERVATION STATUS AND Bryophytes may be sparse to absent in MANAGEMENT CONSIDERATIONS some examples of this community. Human alteration of the hydrologic regime of associated ponds and streams ANIMALS are the primary threat to this community. Sweet Gale Shoreline Swamps may Conservation work to protect examples of provide breeding and nesting habitat for this community will need to focus on the common yellowthroat, northern waterthrush, ecological processes that maintain both the and red-winged blackbird. On remote aquatic systems and the other wetlands ponds, common loons may also nest in this occurring in the wetland complex. community. Mink are likely to use this shoreline community for cover and while PLACES TO VISIT searching for green frogs or small mammals, South Stream Wildlife Management Area, such as masked shrew, meadow vole, and Pownal, Vermont Department of Fish star-nosed mole. There are several species and Wildlife (VDFW) of rare dragonflies that are associated with Ferdinand Bog, Ferdinand, West Mountain boggy streams and that may be found in this Wildlife Management Area VDFW community, including forcipate emerald, Island Pond Bog, Brighton, Brighton State Kennedy’s emerald, and oscillated emerald. Park, Vermont Department of Forests, Parks, and Recreation VARIANTS None recognized at this time. SELECTED REFERENCES AND RELATED COMMUNITIES FURTHER READING Intermediate Fen: These fens are Crum, H. 1988. A Focus on Peatlands and dominated by hairy-fruited sedge and a rich Peat Mosses. University of Michigan Press, bryophyte flora and are typically associated Ann Arbor.
CHARACTERISTIC PLANTS
SHRUBS Occasional to Locally Abundant Species Abundant Species Bluejoint grass – Calamagrostis canadensis Sweet gale – Myrica gale Marsh cinquefoil – Potentilla palustris Meadow-sweet – Spiraea alba var. latifolia Swamp candles – Lysimachia terrestris Leatherleaf – Chamaedaphne calyculata Marsh St. John’s-wort – Triadenum fraseri Occasional to Locally Abundant Species Common cattail – Typha latifolia Speckled alder – Alnus incana Three-way sedge – Dulichium arundinaceum Swamp rose – Rosa palustris BRYOPHYTES Red-osier dogwood – Cornus sericea Occasional to Locally Abundant Species Willow – Salix spp. Moss – Sphagnum teres Red maple saplings – Acer rubrum Moss – Sphagnum subsecundum HERBS Moss – Calliergon stramineum Abundant Species RARE AND UNCOMMON PLANTS Hairy-fruited sedge – Carex lasiocarpa Creeping sedge – Carex chordorrhiza Tussock sedge – Carex stricta Marsh mermaid-weed – Proserpinaca palustris
Shrub SwampsProfile / 383 BUTTONBUSH SWAMP
ECOLOGY AND PHYSICAL SETTING Buttonbush Swamps are our wettest shrub swamps. They occur adjacent to larger lakes and ponds in association with Deep Bulrush Marshes and Wild Rice Marshes, and in oxbow ponds and backwater depressions of our larger rivers. They also occur in small, isolated depressions where the water table drops slowly during the spring and summer. Buttonbush Swamps are permanently saturated and are typically flooded for at least the early part of the growing season. Deep organic muck soils are typical, resulting from the permanent saturation of the substrate. In swamps that become drier by summer, there may be only shallow organic horizons over mineral soil. Most of our largest Buttonbush Swamps occur along the edges of Lake Champlain. Here, they form distinctive circular clones in a mosaic of deepwater marshes that are DISTRIBUTION/ABUNDANCE clearly visible in aerial photographs. In years when the lake Buttonbush Swamps level remains high into the summer, even some of the flood- are scattered in the warmer tolerant buttonbush may succumb. Scattered throughout the regions of Vermont, with the warmer regions, Buttonbush Swamps are not found in the largest examples adjacent to Lake Champlain. They occur colder regions of the state. throughout eastern North America. VEGETATION Buttonbush is often the only woody plant occurring in these swamps. Its low, spreading and sprawling habit, with exposed roots above the soil, opposite or whorled leaves, and dense round heads of flowers and fruits give these swamps a very distinctive appearance. Leatherleaf and meadow-sweet may also be present. In some lakeside settings adjacent to floodplain forests, saplings of silver maple and green ash are common. Herbaceous plant diversity is variable from swamp to swamp. In the wettest swamps, herbs are sparse, if they are present at all. An occasional marsh fern may grow from the
384 / Wetland, Woodland, Wildland BUTTONBUSH SWAMP
fibrous base of buttonbush shrubs, or there VARIANTS may be a few plants of common water Buttonbush Basin Swamp: This plantain or floating pondweed in the variant is known in Vermont only from standing water. Common duckweed is isolated basins in the southern part of the abundant in some of these wet swamps. In state but it is more abundant farther south. swamps with less standing water, species Most known examples occur in kettle hole diversity may be higher and include such depressions in glacial outwash, especially species as water-willow, giant bur-reed, in southeastern Vermont. Due to the very wild rice, marsh mermaid-weed, three-way permeable soils in these examples, the sedge, and broad-leaved arrowhead. In the small, isolated basins have shallow standing driest swamps or in dry years when the water in the spring that may drop to well muddy swamp bottoms become exposed, below the ground surface by late summer. several species of annual beggar’s ticks may Other examples occur in isolated bedrock become established. The moss depressions that drain poorly and have Drepanocladus aduncus is commonly standing water in the spring and early found attached to the exposed roots and summer. Although stems of buttonbush these two geologic near water level and settings are very is apparently well different, the resulting adapted to seasonal hydrologic regimes inundation. More are very similar. study of the Buttonbush domi- bryophyte flora nates, but other of Buttonbush shrubs may be Swamps is needed. present, including ANIMALS speckled alder, highbush blueberry, Buttonbush winterberry holly, Swamps provide The unmistakable flowerhead of buttonbush. leatherleaf, and good brood cover maleberry. Herbs for wood ducks, mallards, and black ducks, include three-way sedge, cinnamon fern, and also provide occasional nesting habitat. marsh fern, and rice cutgrass. There can be Other birds that use Buttonbush Swamps a lush moss carpet include Virginia rail, red-winged blackbird, if there are hummocks above the high and cedar waxwing. Common moorhen water level, dominated by several species may be present during times of the year of Sphagnum (S. palustre, S. subtile, S. when there is standing water. Black terns magellanicum, S. squarrosum). There may use Buttonbush Swamps at Missisquoi be large areas of black, mucky substrate National Wildlife Refuge and may nest in that is bare of bryophytes between the old plant debris that accumulates at the hummocks. shrub bases. Jefferson’s salamander, spotted salamander, and wood frog are some of the RELATED COMMUNITIES amphibians found in this community. Alder Swamp: This broadly defined community is dominated by speckled alder and has a hydrologic regime with less standing water. Sweet Gale Shoreline Swamp: This shrub swamp community occurs primarily on peaty soils with mineral enrichment and is typically found along the shores of small ponds or streams flowing through peatlands.
Shrub SwampsProfile / 385 BUTTONBUSH SWAMP
CONSERVATION STATUS AND CHARACTERISTIC PLANTS MANAGEMENT CONSIDERATIONS SHRUBS Buttonbush Swamps that occur adjacent Abundant Species to lakes and ponds and in the backwaters Buttonbush – Cephalanthus occidentalis of river floodplains are maintained by Occasional to Locally Abundant Species specific hydrologic conditions. Hydrologic Leatherleaf – Chamaedaphne calyculata alterations that lead to shorter or longer Meadow-sweet – Spiraea alba var. latifolia periods of flooding or changes in the depth Silver maple – Acer saccharinum of flooding are likely to result in a change Green ash – Fraxinus pennsylvanica in species composition. Clearcutting and HERBS gravel mining adjacent to the Buttonbush Occasional to Locally Abundant Species Basin Swamp variants are also expected to Marsh fern – Thelypteris palustris adversely affect these swamps. Common water plantain – Alisma plantago- aquatica PLACES TO VISIT Floating pondweed – Potamogeton natans Missisquoi National Wildlife Refuge, Common duckweed – Lemna minor Swanton and Highgate, U.S. Fish and Water-willow – Decodon verticillatus Wildlife Service Giant bur-reed – Sparganium eurycarpum Rock River Wildlife Management Area, Wild rice – Zizania aquatica Highgate, Vermont Department of Fish Three-way sedge – Dulichium arundinaceum and Wildlife (VDFW) Broad-leaved arrowhead – Sagittaria latifolia Sensitive fern – Onoclea sensibilis Sand Bar Wildlife Management Area, Rice cutgrass – Leersia oryzoides Milton, VDFW Water parsnip – Sium suave Dead Creek Wildlife Management Area, Beggar’s ticks – Bidens spp. Addison, VDFW J. Maynard Miller Town Forest, Vernon BRYOPHYTES Helen W. Buckner Memorial Preserve Occasional to Locally Abundant Species at Bald Mountain, West Haven, Moss – Drepanocladus aduncus Moss – Leptodictyum riparium The Nature Conservancy RARE AND UNCOMMON PLANTS Marsh mermaid-weed – Proserpinaca palustris Yellow water-crowfoot – Ranunculus flabellaris
Dark patches of Buttonbush Swamp contrast with the bright green marsh communities at the Missisquoi River delta.
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