Salt damage may develop on newly planted or seeded areas due to con- 

 centration through evaporation in the zone between neap tide high water 

 and spring tide hlgK water during periods of low rainfall and warm tem- 

 peratures following spring tides. This also occurs in sounds and bays 

 subject to wind setup in which the wind pattern results in extended 

 periods of low water during hot weather; e.g., in Core Sound, North 

 Carolina. Under these conditions, soil water salinities of 50 to 75 

 parts per thousand may develop and persist until diluted by rainfall or 

 tidal inundation (Woodhouse, Seneca, and Broome, 1974). 



Irregularly flooded, high marshes are subject to occasional salt 

 buildup through evaporation and ion exclusion, regardless of soil texture 

 However, this is usually limited to poorly drained areas that are flood- 

 ed by storm tides. In humid climates precipitation plus freshwater 

 seepage from higher ground tends to keep salinities in most high marshes 

 well below sea strength. Under more arid conditions, salt concentrations 

 often exclude marsh species altogether. 



Recently deposited sediments such as dredged materials are subject 

 to the same processes as the soils of established marshes once they are 

 populated by plants. Consequently, salt contents of sandy materials in 

 the intertidal zone are not likely to impede establishment of locally 

 adapted marsh species. Salt buildup may delay or prevent plant estab- 

 lishment on irregularly flooded sites, particularly when sandy materials 

 are exposed to periods of low rainfall and high temperatures just before 

 and following planting. Domes of sandy material adjacent to and above 

 marsh plantings tend to reduce salt damage by accumulating precipitation 

 which seeps outward, lowering salt concentration in the planting zone. 



Salt retention by freshly deposited, fine-textured dredged materials 

 may become a deterrent to marsh establishment. This is suggested by a 

 greenhouse test using a tidal simulation system (Barko, et al., 1977; 

 Smart and Barko, 1978). The problems inherent to the extrapolation of 

 greenhouse results to field conditions might be expected to be magni- 

 fied here. However, these data could help in explaining salt damage 

 in new plantings. Areas of salt buildup were found in recently planted 

 intertidal salt marsh with dying of plants when salinity reached 45 

 parts per thousand (Woodhouse, Seneca, and Broome, 1974). These spots 

 appeared to be related to segregation and stratification of fine- 

 textured sediments contained in dredged spoil. 



3. Oxygen-Aeration . 



Marsh soils are, by nature, chronically or periodically flooded 

 and are, therefore, usually poorly to very poorly aerated. The sever- 

 ity and duration of this varies with such factors as topographic posi- 

 tion, soil texture, and water regime as well as the biological activity 

 in the soil. Oxygen is supplied to these soils by oxygen-bearing water 

 and plants growing on them. Parts of intertidal marsh soils may be 

 drained and aerated at each ebbtide if the internal drainage allows 

 appreciable emptying of pores during these brief intervals of exposure. 



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