Introduction to Barrier Island Ecology

1. Introduction to Barrier IslandEcology Biology 366 Ecology 16 April 2002

2. Barrier Island Transect • Beach and Dunes • Shrub Thicket and Maritime Forest • Freshwater Wetlands • Tidal Marsh • Estuarine Waters/Sand and Mud Flats

3. Dune Formation Sand, moved by the process of saltation, accumulates around objects including vegetation and flotsam

4. Dune Formation • Elements required for dune formation Sand Wind Object

5. American Beachgrass (Ammophila breviligulata)

6. Sea Oats(Uniola paniculata)

7. Panic Grass (Panicum amarum)

8. Saltmeadow Cordgrass (Spartina patens)

9. Line of debris at spring tide Debris is called “wrack” Most dunes form here Strand Line or Wrack Line

10. Large quantities of sand moved across strand Common on prograding (growing) beaches Rare on eroding beaches Strand Line or Wrack Line

11. Youngest strand lines lie most seaward Multiple dune ridges form as strand lines are colonized Dune Environments Oldest - - - - - - > Youngest

12. Dunes and colonizing plants grow in concert Dune Environments Year 3 Year 2 Year1

13. Dune Environmental Conditions • Low soil nutrients (N and P) • Desiccating winds • Blowing sand

14. Dune Environmental Conditions • Air and soil temperatures are highly variable

15. Unvegetated dunes “migrate” or move from <1 m to >15 m annually Migrating dunes engulf surroundings Dune Processes Natural revegetation a long term process

16. Occur when vegetation mantle is destroyed Difficult to stop, once started Creates environment called “slack” Blowouts blowout

17. Oceanic overwash “erosion” Off-road vehicle (ORV) traffic Sand fencing: wooden, brush, trees Natural and Man-induced Impacts on Dunes Washovers

18. Salt aerosol effects on plants Salt aerosol source this side Salt Aerosol Impacts

19. Source of Salt Aerosols Salt Aerosols

20. Salt Aerosol Impact on Plants Source of salt aerosol (ocean side)

21. Salt Aerosol Impact on Plants • Generally decreases from strand line, landward • Highest on foredunes • Lowest in slacks and lee of dunes

22. Coastal Communities and Processes • Beach and Dunes • Shrub Thicket and Maritime Forest • Freshwater Wetlands • Tidal Marsh • Estuarine Waters/Sand and Mud Flats

23. Shrub Thicket Environments • Early colonizers (survive low nutrients) • Best examples are in dune slacks • Reduced salt aerosol environment allows arborescent vegetation to flourish

24. Wax Myrtle (Myrica pennsylvanica) • Northern Bayberry is common in thickets from Cape Hatteras northward into New England • Bayberry candles are made from the waxy coating on the berries

25. Yaupon (Ilex vomitoria)

26. Maritime Forest Environments • Develop under the influence of salt aerosols • Restricted distribution • Shear edge created by salt aerosols

27. Maritime Forest Environments • Species adapted to: • Low salt aerosols • low soil nutrients • sandy soils • Salt aerosols control location and structure of the maritime forest

28. Maritime Forest Environments • Vines are common • Tree leaves small, thick, evergreen Live Oak (Quercus virginiana)

29. Bear oak (Quercus illicifolia) common along New England maritime-influence forests

30. Southern Red Oak (Quercus falcata) Common in Mid-Atlantic maritime forests

31. Red Cedar (Juniperus virginiana) ocean Salt aerosol damage

32. American Holly (Ilex opaca)

33. Loblolly Pine (Pinus taeda) Loblolly pine is the most common pine in the maritime forest. It typically is successional and is replaced by live or laurel oak in the southeastern US.

34. Woodbine (Parthenocissus quinquefolia) Dogwood (Cornus florida) Poison Ivy (Rhus toxicodendron)

35. Development of Maritime Forests • Develop on coastal dune systems • Sterile sandy soils • Hummocky topography • Begin as scattered shrubs

36. Natural Impacts on Maritime Forests Impact of hurricanes on maritime forest vegetation. Pines are typically snapped off; cabbage palms survive. Live oak and magnolia have branches and leaves ripped off. Large migrating dunes are capable of overwhelming shrub and forest vegetation

37. Significant Human Impacts • Fragmentation occurs when development occurs within a continuous forest Forest opened to salt aerosol impacts when development occurs

38. Freshwater Wetland Environments • Ponds, swamps, marshes • Form where water table intersects ground surface

39. Freshwater Wetland Environments • Receive groundwater input from adjacent dunes • Influenced by groundwater and rainfall Water flows from adjacent dunes into slough between dunes

40. Freshwater Wetlands • Cattails (Typha spp.) • Bulrush (Scirpus spp.)

41. Tidal Marsh Environments • Develop in areas protected from wave attack • Topographically flat, incised with drainage creeks

42. Tidal Marsh Environments • Alternately exposed and covered by tides daily • “Pulse-stable” environments

43. Tidal Marsh Environment • Saltmeadow Cordgrass (Spartina patens) • Smooth Cordgrass (Spartina alterniflora)

44. Zonation • Cordgrass dominant above and below mean tide level • Many other species dominant above average high tides

45. Black Needlerush (Juncus roemerianus) Black Needlerush Black Needlerush is common at the upper edge of the tidal marsh where the tide floods only occasionally

46. Sea Ox-eye (Borrichia frutescens) Sea Lavender (Limonium carolinianum)

47. Glassworts (Salicornia spp.) These succulent plants grow in the most saline environments in the tidal marsh area

48. Formation of Tidal Marsh • Sand and mudflats colonized by smooth cordgrass • must reach critical elevation • seed falls on flats • spread by rhizomes Typical environments colonized by smooth cordgrass primarily by seeds

49. Formation of Tidal Marsh Sand flats are colonized by clumps of smooth cordgrass. Alternatively, the sand flats can be colonized by germinating seeds of smooth cordgrass. Colonization by Spartina alterniflora

50. Formation of Tidal Marsh • Sand flats may become uniformly vegetated in 2-5 years • Creeks become incised as community matures