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Coastal Plants from Cape Cod to Cape Canaveral
By Irene H. Stuckey Lisa Lofland Gould
The University of North Carolina Press Copyright © 2001 University of North Carolina Press
All right reserved.
Preface Coastal areas have served human beings for thousands of years. The ocean and its edges provide food for people, livestock, and wildlife; embayments furnish safe harbor for commercial and recreational vessels; beaches offer recreation and relaxation; breezes off the ocean provide cooling in the summer; and warm ocean waters moderate the coastal climate through the winter. Coastal habitats are also usually places of great beauty. It is small wonder that nearly two-thirds of the world's human population is located in coastal regions. The coastal zone has also been a convenient place to build highways and railroads, dump garbage, and discharge sewage effluent.
Human use of salt marshes along the eastern coast of the United States has a long history and serves as a good example of how coastal systems have been treated. The European settlers allowed livestock to graze on the marshes, and people have cut marsh grasses for hay up to the present time (see the entry for salt hay grass [Spartina patens]). But from colonial times to the mid-twentieth century, as populations grew along the East Coast and fewer people farmed the land, more people considered salt marshes to be wasteland that was merely a breeding ground for mosquitoes. Thousands of acres of marsh were filled, ditched, drained, or used as dumps. Some of the New England states lost as much as 30-50 percent of their original saltmarsh area.
Beginning in the 1930s, duck hunters recognized the importance of marshes-both salt and fresh-in providing waterfowl habitat. Serious interest in saving salt marshes began in Florida after World War II ended and sportsfishermen returned to their favorite activity. They soon realized that the catches of sailfish were declining and sought to determine where the fish lived during its juvenile stages. The fishermen requested help from marine biologists, but it was not until the 1950s that a juvenile sailfish was discovered in a Florida tidal salt marsh. The fish was only slightly longer than 1 inch (2.5 cm), but it had the characteristic sail along the dorsal fin and a long, slender, pointed beak. It was obviously a juvenile sailfish.
With the discovery that salt marshes served as nurseries for fish and shellfish, people began to recognize their value and to conduct research on how salt marshes function. In the early 1960s, Eugene Odum, along with students and colleagues at the University of Georgia, began decades of seminal work in saltmarsh functioning (e.g., Odum and de la Cruz 1967, Teal 1981). During the same period, Massachusetts and Rhode Island passed laws protecting coastal wetlands. Several other New England, Middle Atlantic, and southern states followed suit in the 1970s, at the same time that federal wetland regulations were being developed; now every state along the eastern seaboard has regulations protecting coastal wetlands. Restorative measures were begun in several states in the 1970s and 1980s. Saltmarsh restoration projects are peaking now, along with an understanding of the many functions of salt marshes, although these efforts are progressing more slowly than many people would like.
Interest in saving the salt marshes stimulated interest in the plants that grow in and around them. Higher plants are not particularly tolerant of salt, but some plant families contain a fairly large number of species that can grow and reproduce in varying levels of salinity. These include grasses and sedges and members of the goosefoot and aster families. Other families also contain a few species that can tolerate salinity. Although considerable research has been conducted on the tolerance of plants to salt, scientists have reached no agreement about whether plants that live in saline habitats require salt or whether they simply have developed internal mechanisms that allow them to tolerate it. More research is required to answer this question.
In addition to salt marshes, many different aquatic, wetland, and terrestrial habitats, including beaches, rocky shores, dunes, forests, and freshwater areas, can be found along the Atlantic coast of North America. These habitats are part of a variety of ecosystems. An ecosystem is made up of communities of organisms (plants, animals, fungi, etc.) and the physical environment they inhabit. The organisms in an ecosystem interact with one another and with the physical environment to form a functioning unit for the flow of energy and the cycling of materials.
A habitat is a location where a particular species is normally found-some scientists call it an organism's "address." Each ecosystem may contain many different habitats in which organisms can live. Saltmarsh ecosystems, for example, include areas that are flushed daily by tides, as well as areas that are inundated only by the highest tides of the month or the year. Different organisms inhabit those different areas-with some overlap-although they are all considered components of the same ecosystem. Some organisms can thrive and reproduce in several different habitats, as long as each habitat provides the appropriate combination of environmental factors. For example, northern bayberry (Myrica pensylvanica) may be found growing on coastal dunes, in scrub thickets or woodlands, or along the borders of ponds or salt marshes.
For plants to occupy a certain habitat, light, water, temperature, nutrients, and a substrate on which to grow (such as sand, soil, muck, peat, water, or even another plant) must be within the range of those plants' tolerance. Even a common plant will disappear from a habitat if an essential environmental factor shifts beyond the plant's range of tolerance. Some species of goldenrod, such as gray goldenrod (Solidago nemoralis), flourish in full sun but gradually disappear when surrounding trees and shrubs grow large enough to shade the area. Rose pogonia (Pogonia ophioglossoides) is another example; this orchid sometimes grows abundantly in freshwater wetlands but will not survive if the wetland soil is drained artificially. In general, common plants tend to be broadly adapted, whereas rare ones survive only where certain narrowly defined environmental conditions exist.
A Look at Coastal Habitats
Beaches and Mudflats
Beaches are sloping habitats composed of loose particles in direct contact with a body of water. They are generally dominated by mineral particles no more than 10 inches (25.4 cm) in diameter and lack significant vegetation cover. In addition to sand, gravel, and cobbles, fragments of mollusk shells or other sea creatures may form a substantial proportion of some beaches (such as the beach at the Cape Hatteras National Seashore in North Carolina).
Most sand beaches on the Atlantic coast are composed primarily of quartz grains. Beautiful sand beaches may be seen in such places as the Cape Cod National Seashore in Massachusetts, Sandy Hook National Recreation Area in New Jersey, Chincoteague National Wildlife Refuge in Virginia, Cumberland Island National Seashore in Georgia, and Canaveral National Seashore in Florida. The shore below the Point Judith Lighthouse in Narragansett, Rhode Island, is a good place to view a cobble beach. Cobble beaches with particles that are flattened are sometimes called shingle beaches; such beaches can be found in a few places within the book's range, including the Melville Public Fishing Area in Portsmouth, Rhode Island, and elsewhere along the western shore of Aquidneck Island, Rhode Island.
Coastal shores dominated by stones greater than 10 inches (25.4 cm) in diameter are uncommon south of Cape Cod. These rocky shores are discussed below.
Level areas of sand or mud that are exposed only during low tide are called sandflats or mudflats. Although an amazing variety of animals, such as clams, snails, sandworms, sea urchins, and sand dollars, can thrive in this habitat and many animals, such as waterfowl, shorebirds, and wading birds, feed on them, very few flowering plants are able to survive. Atlantic mudwort (Limosella australis) may be found on brackish tidal flats; eelgrass (Zostera marina) and shoalgrass (Halodule wrightii) also sometimes occur on tidal flats.
Because of wave action and the salinity of seawater, beaches, like tidal flats, are very harsh environments for flowering plants; those that do grow on beaches occur near the highest high tide line. Common saltwort (Salsola kali), sea chickweed (Honckenya peploides), sea rocket (Cakile edentula), and dusty miller (Artemisia stelleriana) are among the plants that can be found growing on beaches from Virginia north; the rare beach amaranth (Amaranthus pumilus)-a federally classified threatened species-may also occasionally be found on beaches from South Carolina to Massachusetts. Very few plants grow on open beaches south of Cape Hatteras. Strong winds and high tides cause sand to shift constantly, and the plants most likely to be found there are common saltwort, sea rocket, sea purslane (Sesuvium spp.), and silver-leaf croton (Croton punctatus).
Since beaches are popular recreation sites, human activities have a strong influence on the survival of beach-dwelling plants and animals. Even moderate foot traffic can destroy the vegetation; off-road vehicles have an even greater impact.
Rocky shores are dominated by bedrock outcrops and boulders. They are conspicuous generally only as far south as Rhode Island (Beavertail State Park in Jamestown, Rhode Island, is an excellent place to observe a rocky shore), but smaller outcrops can be found in several places on the Connecticut and New York shores. The lower zones on the rocks are flooded and exposed daily by the tides, whereas the upper zones are flooded less frequently, during unusually high tides or in strong storms.
These shores are a favorite place for fishermen. In most cases, the rocks descend directly into the ocean, but sheltered sites may have tiny gravel beaches and tidal pools. In spite of being frequently washed by sea water, several salt-tolerant land plants have survived by being well rooted in crevices in the lower-lying rocks. They include sea chickweed, a plant that also grows on both cobble and sand beaches; the naturalized scarlet pimpernel (Anagallis arvensis); sea lavender (Limonium carolinianum) and seaside plantain (Plantago maritima), which are also found in salt marshes; and awl-aster (Aster pilosus), an inland plant that has a very shortened globular form in this harsh habitat.
Aquatic beds are wetland and deepwater habitats that are dominated by plants that grow on or below the water's surface. Along the rocky coasts of the Northeast, aquatic beds of kelp and rockweed may occur in water as deep as 98 feet (30 m) or in water shallow enough to expose the seaweed during low tide. Many species of algae are also found in estuarine and freshwater habitats. Algae are beyond the scope of this book, but readers who would like more information may find that Villalard-Bohnsack's Illustrated Key to the Seaweeds of New England (1995) and Schneider and Searles's Seaweeds of the Southeastern United States, Cape Hatteras to Cape Canaveral (1991) are excellent resources.
Several species of flowering plants, known collectively as seagrasses, form aquatic beds in shallow, saline coastal waters. Eelgrass grows from Greenland to Florida and is the dominant seagrass north of the Carolinas. From the Carolinas to the Caribbean, turtlegrass (Thalassia testudina) is the primary seagrass; shoalgrass, manatee-grass (Cymodocea filiformis), and Englemann's seagrass (Halophila engelmannii) are also found in this range. These seagrasses play a major role in stabilizing sediments in shallow coastal waters and are extremely important nursery grounds for many fish and shellfish. Eelgrass is also an important component of the diets of many waterfowl. Water pollution, especially from sewage and agricultural runoff, has had a detrimental effect on seagrass beds all along the East Coast.
Widgeon-grass (Ruppia maritima) may also be found in seagrass beds and in permanent pools and tidal creeks within salt marshes, but throughout the range of this book, it occurs more frequently in brackish waters, along with horned pondweed (Zannichellia palustris), water-nymph (Najas spp.), several species of pondweed (Potamogeton spp.), and other aquatic plants. Widgeon-grass, pondweeds, and water-nymph are important sources of food for waterfowl and provide shelter and nursery habitat for fish and shellfish.
Many interesting species of plants grow at the top of coastal cliffs, some salt tolerant, others not. Plants that grow above the ocean, out of reach of the waves and regular salt spray, are likely to be less salt tolerant, whereas those on the beach at the bottom of a cliff or in rock crevices that are sometimes washed by salt spray must be tolerant of salt in order to survive. Plants rarely grow near the base of cliffs that rise directly from the ocean because the high wave energy prevents them from becoming established. Plants that grow at the top of coastal cliffs include northern bayberry, both golden heather (Hudsonia ericoides) and beach heather (Hudsonia tomentosa), and several species of goldenrod (Solidago spp.) and asters (Aster spp.). Block Island, Rhode Island, is home to spectacular coastal cliffs.
Dunes are hills of sand that develop above beaches where winds and tides are favorable and an abundant supply of sand is available. Most of the dunes along the Atlantic coast are stabilized by salt-tolerant plants. Some dunes are not stable, such as many dunes along the Outer Banks of North Carolina and some notable dunes on Cape Cod. Even the most stable dunes can be destroyed by a single violent storm.
American beachgrass (Ammophila breviligulata) is the primary dune stabilizer along northern coasts (from southern Virginia north), and sea oats (Uniola paniculata) and seaside panicum (Panicum amarum) stabilize the dunes from North Carolina south. Other plants common to the upper areas of northern beaches and the ocean-facing areas of dunes include purple sand grass (Triplasis purpurea), dusty miller, seabeach orach (Atriplex pentandra), common saltwort, sea rocket, beach pea (Lathyrus japonicus), seaside spurge (Chamaesyce polygonifolia), seaside goldenrod (Solidago sempervirens), and common cocklebur (Xanthium strumarium). On southern dunes, common species include purple sand grass, dune sandbur (Cenchrus tribuloides), common saltwort, sea purslane, sea rocket, seaside spurge, silver-leaf croton, beach pennywort (Hydrocotyle bonariensis), beach elder (Iva imbricata), and common cocklebur.
The backdune and interdune areas feature a fascinating transition from plants that tolerate high levels of salinity and wind action to those with little tolerance. Plants more common to northern (from Virginia north) interdune and backdune areas include pitch pine (Pinus rigida), eastern red cedar (Juniperus virginiana), hairgrass (Deschampsia spp.), both dune sandbur and common sandbur (Cenchrus longispinus), switchgrass (Panicum virgatum), quaking aspen (Populus tremuloides), northern bayberry, black oak (Quercus velutina), sand jointweed (Polygonella articulata), sassafras (Sassafras albidum), shadbush (Amelanchier canadensis), beach plum (Prunus maritima), wild black cherry (Prunus serotina), the introduced salt-spray rose (Rosa rugosa), poison ivy (Toxicodendron radicans), American holly (Ilex opaca), Virginia creeper (Parthenocissus quinquefolia), beach pinweed (Lechea maritima), beach heather, prickly-pear cactus (Opuntia spp.), and bearberry (Arctostaphylos uva-ursi). Dune swales-low, moist areas between dunes-may also contain rushes (Juncus spp.), winterberry (Ilex verticillata), red maple (Acer rubrum), black gum (Nyssa sylvatica), and a variety of ferns.
Excerpted from Coastal Plants from Cape Cod to Cape Canaveral by Irene H. Stuckey Lisa Lofland Gould Copyright © 2001 by University of North Carolina Press. Excerpted by permission.
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