able 3. Comparison of above- and belowground productivity in Spartina al term' flora in 



Recalculated using method of Valiela et al . (1976). 



Odum (1969) suggested that this high 

 productivity was due to a tidal subsidy. 

 In other words, the tides contributed 

 something to the marsh that enhanced plant 

 production. Steever et al. (1976) found 

 they could associate about 90% of the 

 variation in Spartina productivity in Long 

 Island Sound with the tidal range, which 

 varied from 0.7 m to nearly 2.3 m. In one 

 site, a portion of the marsh was behind a 

 tide gate that restricted tidal movement 

 and reduced the plant production by 26% 

 relative to the rest of the marsh. 

 Furthermore, they showed that a strong 

 relation exists between production and 

 tidal range all along the Atlantic coast. 

 Clearly, water movement is associated with 

 salt marsh production; the mechanisms 

 involved include nutrient supply, waste 

 removal, and salinity control, or all of 

 these combined. 



with the salts in the water. All of the 

 minor nutrients needed by plants, as well 

 as the major nutrient potassium, are 

 present in seawater. The major 



nutrients-- nitrogen, 

 potassium (N, P, and 

 supply in the marsh 

 banks. (Potassium is 

 the marsh since it 

 seawater. ) Carbon 

 enters the 

 through its 



phosphorus, and 



K)--are also in good 



mud along the creek 



plentiful throughout 



is so abundant in 



dioxide not only 



plant from the atmosphere 



leaves, but also through its 



roots from C0 2 reserves in creek bank 

 soils. With these plentiful nutrients, 

 Spartina growing on New England creek 

 banks has a productivity comparable to 

 that of plants growing naturally anywhere. 

 The maximum total annual marsh production 

 in New England is less than that of more 

 southerly marshes only because the growing 

 season is shorter in the north. 



Expe 



Salt marsh productivity is high, Salt Mars 



especially that of the Spartina fertilize 



alternif lora growing along the creek Spartina 



banks, because of the almost ideal factors marsh exc 



for growth found there. There is a lack creek ban 



of competition along creek banks, which the addi 



gives the plants space and an abundance of produces 



sunlight. The water supply is plentiful can be 



and Spartina has mechanisms for dealing phosphoru 



riments at 

 h have shown 

 r increases 

 alternif lora 



Great Sippewissett 

 that the addition of 

 the productivity of 



in al 1 parts of the 



ept the already highly productive 

 ks (Valiela and Teal 1974). Once 

 tion of nitrogen to the marsh 

 its maximum effect, production 

 further increased by adding 

 s (Figure 17), though phosphorus 



28 



