the most important roosting area for shorebirds. Concentrations of more than 

 10,000 birds have been reported from sand beaches in region 6. Gulls and 

 terns roost in large numbers on sand and gravel beaches. Sanderlings feed 

 extensively on sand beaches and flats throughout the coastal zone. 

 Semipalmated plovers, black-bellied plovers, red knots, and semipalmated 

 sandpipers feed on sand and gravel flats. Sand and gravel flats that are 

 covered with seaweed are utilized extensively by ruddy turnstones, which 

 forage primarily by turning over algal fronds, stones, and pebbles. Many 

 large gulls feed extensively on sand and gravel flats, especially those that 

 are mussel-covered. They often can be observed dropping mussels from the air 

 onto stones in order to break the shells. 



BEACH DUNE PLANT COMMUNITIES 



Sand beach and sand dune communities are found on sand and gravel substrata 

 above the mean high tide line. A series of five plant communities has been 

 described for coastal Maine (Trudeau 1977; and Nelson and Fink 1978). They 

 include a foredune community, a dunegrass community, a dry dune slack 

 community, a shrub community, and a dune forest community. The dominant plant 

 associations in these communities have been described for the Phippsburg- 

 Georgetown area (region 2) by Trudeau (1977) and for all of the coast by 

 Nelson and Fink (1978). 



Predominant ecological factors influencing the distribution of the plant 

 species in the sand beach and sand dune communities include salt spray, soil 

 moisture, soil temperature, nutrient availability, soil salinity, and air 

 moisture. The five communities intergrade and represent a series of 

 successional communities starting with the pioneering annuals in the foredune 

 community and terminating with the dune forest community. 



The foredune community is composed of two major associations: seasonal berm 

 and perennial berm. The seasonal berm is flooded by spring high tides and 

 winter storms. The substratum is very unstable because it is subject to 

 frequent storm-related erosion. Rapidly growing, fecund annuals [i.e., sea 

 rocket ( Cakile edentula) and saltworth ( Salsola kali )] are the only plant 

 species able to repopulate this habitat. The perennial berm or eolian ramp is 

 a recently accreted area of wind-deposited sand above the spring and storm 

 tides. The community is dominated by American beachgrass ( Ammophila 

 breviligulata ) , beach pea ( Lathyrus japonicus ) , and dusty miller ( Artemisia 

 stelleriana ) . Strand wheat ( Elymus arenarius) replaces or coexists with 

 beachgrass on the more rocky and cobble beaches in regions 4 to 6. 



The dunegrass community is dominated by American beachgrass. It runs from the 

 frontal dune ridge inland to a shrub community. Its habitat contains no soil 

 and only a limited amount of nutrients. It receives excessive salt spray. 

 Species diversity is low in this community (Nelson and Fink 1978). Several 

 subassociations have been described by Trudeau (1977) and Nelson and Fink 

 (1978). Rapid growth after burial is an important adaptation for plants in 

 the perennial berm, the dunegrass, and the dry dune slack communities. 



The dry dune slack community is found on dry dunes inland from the dunegrass 

 community in region 2. Salt spray and sand burial rates are lower than in the 

 above communities. This community is dominated by beach heather ( Hudsonia 

 tomentosa ) , which reaches its northernmost distribution in the United States 



4-96 



