Natural Community Systems -- Photo Guide

Coastal sand dune system

coastal sand dune system remnant at Seabrook Beach (photo by Ben Kimball for the NH Natural Heritage Bureau)
coastal sand dune system remnant at Seabrook Beach (photo by Ben Kimball)


DescriptionCoastal sand dune systems occur in areas with actively shifting sand that is associated with the immediate coastal environment.  Within the system, several natural community types correspond to three broad zones: the foredune, the interdune, and the backdune.  The two primary physical processes that produce these different zones (and their corresponding communities) are (1) the degree of exposure to or protection from on-shore winds and therefore degree of sand stabilization, and (2) soil moisture.  The foredune is most exposed to onshore winds and salt spray and is typically dominated by Ammophila breviligulata (beach grass) with few other species.  The interdune is usually dominated by a combination of beach grass along with a broader diversity of other species.  More protected portions of the dune (backdune) are characterized by maritime (“sunken”) forests, shrub thickets, and interdunal swales.  There is one partially intact dune system left in New Hampshire, at The Dunes in Seabrook, and there are several dune remnants scattered elsewhere along the state's coastline.

Beach grass grasslands are typically found on the foredune and other dune areas with shifting sand.  In NH’s only remaining example, most of the foredune has been destroyed by development.  This community may also occur as a narrow strand of vegetation along the shore away from intact dune areas.  Ammophila breviligulata (beach grass) is the dominant species.  It creates extensive colonies by spreading underground rhizomes.  Seaside goldenrod and beach heather can also be abundant. Bayberry - beach plum maritime shrublands are short- to moderate-height shrub thickets found in the backdune area and in small, protected hollows in the interdune.  Sandy soils are a bit more stable than those found in the foredune and exposed areas of the interdune.  Coastal interdunal marsh/swale is a freshwater wetland community found in sandy depressions between sand dunes.  Dominant plants vary from swale to swale but include Vaccinium macrocarpon (large cranberry) and Juncus arcticus (shore rush).  Coastal shoreline strand/swale is a sparsely vegetated upper intertidal community that can be found on sandy depressions within backdunes and in channels bordering salt marshes.  This community is flooded less than daily and is often characterized by plant stems and other detritus washed in on the higher tides and covering much of the substrate surface.  These upper intertidal areas form either large patches or narrow strands along protected low-energy shorelines and are important habitat for various arthropods, shore birds, and other animals and are sparsely vegetated by halophytic herbs. 

Diagnostic natural communities:

      • Beach grass grassland (S1)

      • Bayberry - beach plum maritime shrubland (S1)

       Hudsonia maritime shrubland (S1)

      • Coastal interdunal marsh/swale (S1)

      • Maritime wooded dune (S1)

Peripheral or occasional natural communities:

      • Coastal shoreline strand/swale (S2)

Landscape settings: coastal strands between ocean and estuarine or upland systems

Soils: shifting sands

Spatial pattern: small patch (120 acres); typically linear zones parallel to the shoreline with foredune and backdune zones

Physiognomy: grassland, herbaceous, dwarf shrubland, shrubland, shrub thicket, forest/woodland

Distribution: limited to Seabrook

Characteristic species:

Beach grass grassland:
Ammophila breviligulata (beach grass)
   Solidago sempervirens (seaside goldenrod)
   Hudsonia tomentosa var. tomentosa (hairy hudsonia)
   Danthonia spicata (poverty oat-grass)
   Schizachyrium scoparium (little bluestem)
   Lathyrus japonicus (beach pea)
   Lechea maritima (seabeach pinweed)
   Polygonella articulata (jointweed)
   Cyperus lupulinus (perennial umbrella-sedge)
   Aristida tuberculosa (sea-beach needlegrass)
   Cyperus grayi (Gray’s umbrella-sedge)

Bayberry - beach plum maritime shrubland:
   Myrica pensylvanica (northern bayberry)
   Prunus maritima (beach plum)
   Toxicodendron radicans (poison ivy)
   Rosa virginiana (Virginia rose)

   Oenothera perennis (small sundrops)
   Achillea millefolium (yarrow)
   Polygonum scandens (large climbing false buckwheat)
   Artemisia campestris ssp. caudata (tall wormwood)

Coastal interdunal marsh/swale:
   Vaccinium macrocarpon (large cranberry)
   Aronia prunifolia (purple chokeberry)
   Ilex verticillata (winterberry)
   Toxicodendron radicans (poison ivy)

   Juncus arcticus (shore rush)
   Triadenum virginicum (marsh St. John’s-wort)

Associated natural community systems:  Coastal sand dune systems are typically sandwiched between open, wave-wracked beaches on the immediate ocean shoreline (the foredune side) and salt marsh systems on the inland (backdune) side.

coastal sand dune natural communities

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