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Dunes and Slacks

Dunes and Slacks

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Dunes and Slacks

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  1. Dunes and Slacks Dune:Mound of wind blown sand often influenced by vegetation Slack: Low depression formed during dune development or by blowouts in the dune field

  2. Barrier Island Dunes and Slacks Vegetation Zones: Strandline Foredune Dunefield Reardune Mesic slack Xeric slack

  3. Strand Line • seaward line of vegetation occurring between the spring tidal elevation and the foredunes

  4. Strand Line • transient zone- eroded by wave action or may develop into foredunes on accreting shorelines • seedbed for plants on foredunes • wrack material enhances germination and growth • salt aerosol levels are high • sea rocket, euphorbia, sea elder, croton, and sea oats

  5. Sea Rocket Strand Line Community • Plants: trap wind-blown sand and form embryonic dunes • Sea rocket is most common species along Atlantic coast • Other species: • Eelgrass (dead stems and leaves), smooth cordgrass (dead stems and leaves), Russian thistle, and seasside broomspurge

  6. Formation of Embryonic Dune

  7. Strand Line Community • Over time: • Nutrient source becomes limited • Environmental conditions change • Vegetation cover begins to change: • Strand Line species replaced by  Dune Pioneers • Russian Thistle Sea Elder • Evening Primrose Sea Oats • Sea Rocket Am. Beachgrass

  8. Dune Pioneer • Sea Oats- restricted to dunes: • extreme conditions of wind-blown salt • shifting sand- allows for burial and excludes competition

  9. Foredune • occur directly behind the strand line • often receive large quantities of blowing sand • sea oats, sea elder, bitter panicum and American beachgrass • salt aerosol levels are high

  10. Dunefield • may consist of many dune ridges that were once foredunes • sand accretion is low • reduced salt spray intensity • camphorweed, pennywort, evening primrose, and horseweed

  11. Reardune • often a transition zone to woody vegetation • salt spray effect diminished • catbrier, live oak, wax myrtle, and red bay • destruction of the dunefield/foredune zones will severely impact vegetation in the reardune

  12. Slacks • low depressions formed during dune ridge development or by blowouts in the dune field • salt spray intensity is low • greater diversity of species • increased plant cover density • may be destroyed by migrating sand dunes

  13. Mesic Slack • water table is at or near the surface during part of the year • pennywort, little blue stem, seaside goldenrod and wax myrtle

  14. Xeric Slack • water table close to surface compared to dunes allowing a greater number of species to develop • pennywort, saltmeadow cordgrass, and camphorweed

  15. Evening primrose Seaside goldenrod Coastal Plant Geography • Distribution influenced by climate: Tº and precipitation • Adapted for rapid dispersal and colonization • Most occur over broad geographical range

  16. Poaceae- Sea Oats Vascular Plant Families • Families most represented: Asteraceae- Salt Marsh Aster Cyperaceae- Saltmarsh Bulrush

  17. Coastal Plant Geography cont... • Small (1929) • Southern New Jersey and Delmarva Peninsula is meeting ground for N & S plants • Supported by: • Higgins et al. 1971- found bitter panic grass near its northern limit on Assateague Island, VA • Martin (1959)- Panic grass absent at Island Beach, NJ

  18. Southern limit: American beachgrass Northern limit: Sea oats Coastal Plant Geography cont... • Oosting (1954) and Godfrey (1977): • - Consider NC the dividing line for N &S strand communities • - Godfrey notes a Tº break at Cape Hatteras, NC and:

  19. Northern beach pea  southward Coastal Plant Geography cont... • Art (1976)- Opposed Small’s viewpoint • Atlantic coast plant species are gradually replaced along a latitudinal gradient Sea elder  southward

  20. Prickly pear cactus- found here but not to the north • Northern bayberry- absent but common to the north Coastal Plant Geography cont... • Lazell and Musick (1973) • Intra-Capes ecological zone- b/w Cape Lookout and Cape Hatteras, NC; transition zone for many species

  21. Rare and Endangered Plants • New Jersey: • Seaside broomspurge- rare in NJ, yet abundant in southeast • Seabeach sandwort- endangered in NJ, more common to the north

  22. Rare and Endangered Plants • Massachusetts: • Seaside knotwood- common species • North Carolina: • Seaside knotwood- candidate • for listing as either threatened • or endangered Knotweed, Polygonum glaucum

  23. Non-vascular Plants • More important in slacks • Microorganisms have an important role in soil formation • Aggregates found in dune and slack soils: Fungi, bacteria, actinomycetes, and algae • These plants bind soil particles and increase soil fertility • Little is known of these plants- future research warranted

  24. Non-vascular Plants • Microbial aggregations • Increase in number and complexity as dunes mature • Bacteria binds sand particles to  water-holding capacity • 2 types: • Root microbial aggregates- Sand grains trap in root surface and hairs • Debris microbial aggregates- Sand grains adhere to decaying organic matter to form these

  25. Ulothrix sp. Oedogonium sp. Non-vascular Plants • Algae • Often aggregate with bacteria • Hold water within their cell walls • Interact with microbial aggregates and improve stability • Blue green algae enhance nitrogen content of soils

  26. Non-vascular Plants • Bryophytes- Moul (1969) and Gimingham (1948) • Little research has been done • Found in both dunes and slacks • Relatively intolerant to aerosol salt spray • Important colonizers of secondary dunes

  27. Non-vascular Plants • Fungi- Nicholson and Johnston (1979) • Little research has been done • Increase in incidence as dunes mature • Some play a role in nutrition of higher plants • Some plants are susceptible to fungal attacks

  28. Fungi Mycorrhizal fungi of root system Azospirillium induces proliferation at root hair

  29. Exotic Species • Plants: may establish breeding populations • Accidentally introduced by tourists • Few survive and thrive in dunes and slacks • Japanese sedge • French tamarisk

  30. Animals • Invertebrates • Amphibians • Reptiles • Birds • Mammals • Rare and endangered species • Exotics

  31. Invertebrates • Nematodes: • Suppress growth and cause root damage to plants • Cause die offs of American Beachgrass • Arthropods: • McLachlan et al. (1987) found 7 orders of insects in study along African coast • Insects most common in mature dunes • Mostly found in open sand habitat

  32. Nematodes and Arthropods Ground beetle Beachgrass root-knot nematode

  33. More invertebrates... Monarch Butterfly Ghost Crab

  34. Fowler’s toad- common in dunes and slacks near Shackleford Banks, NC Southern toad- southward of Cape Hatteras, NC Amphibians • Least represented vertebrate in dunes and slacks • Found primarily in slacks • Common species:

  35. Black racer snake Common garter snake Eastern ribbon snake Reptiles • Poorly represented on barrier beaches • Most common species from Cape Cod to Georgia: • Snakes:

  36. Diamondback terrapin Common box turtle Loggerhead sea turtle Reptiles • Turtles: Those seen are probably transients

  37. Birds • Many species use dune and slack resources • Few live entire lifespan in this area • Mostly use dunes and slacks for nesting or feeding sites Terns and gulls use strand line and sand flats Willit- nest in clumps of dune grasses Piping Plover- federally threatened forages along beach for small inverts

  38. Royal Tern Willit Piping Plover Birds

  39. Meadow vole White footed mouse Mammals • Species diversity is typically low • Most are inhabitants of marshes, forests, or old fields • As shrub cover  density and diversity of small mammals also 

  40. Rare and Endangered Animals • Not typical inhabitants of dunes and slacks • Loggerhead sea turtles- use resources to nest • Coastal development decreases number of suitable nesting beaches

  41. Piping Plover Least tern Rare and Endangered Animals • Piping plovers and least tern- • Recreation impacts nesting and foraging success • Storms and predators lower nesting success

  42. Exotic Species • Animals: Introduced domestics • Overgraze and alter substrates • Hogs persist on Back Bay area, VA and Cumberland Island, GA • Cattle, sheep, and goats were common until the 1950’s • Feral horses persist on islands from MD to GA

  43. References • Amos, W. H. and S. H. Amos. 1985. National Audobon Society Nature Guides:Atlantic and Gulf coasts. Random House: New York, NY: 670p. • Graetz, K. E., 1973. Seacoast Plants of the Carolinas. U. S. Department of Agriculture Soil Conservation Service, Raleigh, North Carolina, 206 pp. • Environmental Inventory of Kiawah Island, 1975. Environmental Research Center, Inc., Columbia, South Carolina. • Kraus, E. Jean Wilson, 1988. A Guide to Ocean Dune Plants Common to North Carolina. The University of North Carolina Press, Chapel Hill, North Carolina, 72 pp. • Packham, J. R., and A.J. Willis. 1997. Ecology of dunes, saltmarsh and shingle. Chapman and Hall: Cambridge: 335pp. • Shumway, Scott W., 2000. Facilitative effects of a sand dune shrub on species growing beneath the shrub canopy. Oecologia (2000) 124: 138- 148. • Will, M. E., D. M. Sylvia, 1990. Interaction of Rhizosphere Bacteria, Fertilizer, and Vesicular-Arbuscular Mycorrhizal Fungi with Sea Oats. Appl. Environ. Microbiol., July 1990, p. 2073-2079.

  44. References cont... http://www/