CHAPTER 1. DEFINITION AND DISTRIBUTION 



1.1 DEFINITION 



The regularly flooded tidal salt 

 marshes of eastern North America are 

 almost exclusively Spartina a! term' flora 

 marshes. These marshes are flooded by all 

 tides under normal conditions in areas 

 with semidiurnal tides. They are flooded 

 by seawater or water that is sufficiently 

 salty to inhibit growth of plants such as 

 cattail, Phragmites or reed, or Scirpus 

 species. In New England flooded marshes 

 make up the "low marsh"; in contrast, the 

 "high marsh" comprises infrequently 

 flooded Spartina patens salt hay marshes 

 (Nixon 19~82T Fn Georgia the "high marsh" 

 is covered by a stunted form of S. 

 alternif lora rather than S. patens . 



This profile is restricted to the low 

 marshes in New England. I will 

 subsequently refer to these regularly 

 flooded tidal saline marshes dominated by 

 Spartina alternif lora as "salt marshes." 

 Under the Fish and Wildlife Service's 

 Wetland Classification system (Cowardin et 

 al. 1979), these marshes would be classed 

 as in the estuarine system, the intertidal 

 subsystem, and the emergent class. 



1.2 GENERAL DESCRIPTION 



Regularly flooded tidal salt marshes 

 are readily recognizable all along the 

 east coast even from a distance or from 

 the air. They are flat, grassy areas with 

 meandering tidal creeks running through 

 them (Figure 1). They lie behind some 

 sort of barrier that protects them from 

 the full force of the ocean's waves. 

 Numerous small ponds or pannes occur 

 between the tidal creeks. The occurrence 

 and nature of these ponds have been 

 greatly modified as a result of the 

 numerous, straight ditches dug to control 

 salt marsh mosquitoes. Although many or 



most of the ditches lie in the high or 

 infrequently flooded parts of the salt 

 marsh (Nixon 1982), they are also found in 

 the low marsh. 



On closer examination, other features 

 of the tidal marsh are readily apparent. 

 The marsh sediments are typically, but not 

 always, muddy and soft, saturated with 

 water, and generally highly reduced 

 (lacking in oxygen or other oxidizing 

 compounds and black in color). They smell 

 of sulfides and other volatile sulfur 

 compounds when disturbed. Although there 

 are undecomposed roots and rhizomes within 

 the mud, low marsh sediments are mostly 

 nonorganic and cannot be classified as 

 peat. 



Spartina alternif lora is frequently 

 divided into two forms, tall and short. 

 The tall form occurs along the banks of 

 the tidal creeks and on accreting areas 

 within the marsh. In New England, the 

 tall form generally reaches 1.25 to 2 m in 

 height (Shea et al . 1975). The stems are 

 thick and widely spaced. The short form 

 grows on the remaining marsh. These 

 plants may be as short as 10 cm, have 

 thinner stems, and grow more densely 

 packed. In areas of poorest growth, the 

 plants may be very thin, short, and widely 

 spaced. Although there is a continuous 

 gradation between the tall and short 

 forms, the transition between them is 

 often dramatic in that it takes place 

 within a very short distance. Though this 

 type of salt marsh is almost a natural 

 monoculture of Spartina alterniflora , a 

 few other higher plants such as Salicornia 

 (glassworts) also occur. Algae grow on 

 the sediment surface between the grass 

 stems, often in sufficient abundance to 

 color the surface. 



There is an abundance of wildlife 

 common to these marshes. Though 



