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 flooded by storm 

 surges. In humid climates precipitation, plus freshwater seepage frcj 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. 



In general, suitable plants which can be established in salinities up to 

 about sea strength may be found in all coastal areas. Vegetative stabili- 

 zation in bays and estuaries, where salinities seasonally exceed sea strength, 

 is not likely to succeed. If salinity is a suspected problem, the presence, 

 abundance, and vitality of native intertidal plants in sheltered areas near 

 the proposed project will be an indicator of probable success. 



(3) Oxygen-Aeration . From a practical marsh-building point of view, 

 the scarcity of oxygen in marsh soils appears to be unimportant. There is no 

 evidence that it prevents the establishment of marsh plants on sites that are 

 otherwise suitable. Marsh soils are, by nature, chronically or periodically 

 flooded and are, therefore, usually poorly to very poorly aerated. The 

 severity 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 water and the oxygen-bearing 

 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. Similarly, parts of high 

 marsh soils become aerated during periods of dry weather and low water tables. 



Most sediments, such as freshly deposited dredged materials, will be 

 highly anaerobic or low in oxygen. However, this does not prevent the estab- 

 lishment of adapted marsh species. These plants have various adaptations to 

 an anaerobic environment. For example, certain intertidal species have 

 anatomical features that enable their leaves to supply oxygen to their roots 

 (Teal and Kanwisher, 1966; Anderson, 1974; Kasapligil, 1976). Smooth cord- 

 grass and probably many other grasses utilize ammonia, which is the usual form 

 of nitrogen under anaerobic conditions, more efficiently than the nitrate form 

 usually preferred by upland species (Gosselink, 1970; Woodhouse, Seneca, and 

 Broome, 1976; Mendelssohn, 1979). 



Some intertidal species contribute to the aeration of soils by releasing 

 oxygen from their roots. This has been demonstrated for Pacific cordgrass 

 under controlled conditions and in the field (Pride and Ltngle, 1976; Wong, 

 1976), and has been frequently observed in the form of oxidized (yellowish or 

 brown) zones around the roots and rhizomes of smooth cordgrass. Oxygen 

 supplied in this way promotes the activity of other organisms and eventually 

 contributes to improved internal drainage and increased aeration. Anaerobic 

 conditions affect the growth of marsh plants by favoring the maintenance of 

 nitrogen in the ammonia form and promoting the availability of such elements 

 as iron and manganese by maintaining them in a reduced form. There probably 

 are detrimental effects but little is known about them. Iron toxicity may 

 occur because of the excessive availability of this element under highly 



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