In 1976, Valiela et a1. published 

 the results of the first measurei;ients 

 of the underground production of S. 

 alterniflora and S. patens roots and 

 rhizomes on a New England marsh. 

 Their remarkable finding at Great 

 Sippewissett, Massachusetts, was that 

 belowground production on the high 

 marsh was about four times greater 

 than the green aboveground pro- 

 duction. In addition to the 

 630 gdw/m /yr produced above ground, 

 they calculated a production of some 

 1,610 gdw/m2/yr of rhizoires and 

 9l0gdw/m2/yr of roots (Table 11). 

 Most of this production took place in 

 the first 5 cm (2 inches) below the 

 marsh surface (Figure 1&), began 

 earlier in the season, and proceeded 



faster than leaf growth (Figure 19). 

 The high ratio of belowground to 

 aboveground growth is surprising, but 

 it may reflect the fact that Spartina 

 is water stressed. As Valiela et al. 

 (1976) noted, the plants on the marsh 

 appear greener and show increased 

 growth following heavy rainfall. 



In addition to the production of 

 the higher plants, some carbon and 

 energy is fixed by the marsh algae 

 growing on the sediment surface. This 

 must be a very small amount under the 

 dense S^. patens mat, but in the lower 

 portions of the high marsh there is a 

 significant amount of production by 

 algae in the stunted S^. alterniflora 

 zone. The algal productivity is more 



Table 11. Effect of nitrogen (N) additions on the production 

 (g dry weight/m 2/yr) of high marsh and low marsh vegetation at 

 Great Sippewissett Marsh, Cape Cod (after Valiela et al. 1976), 



Marsh type 



and 

 biomass compartment 



No N addition 

 (control ) 



N appli ca tion rate s 



+0.8 g N/m^/wk +2.5 g N/m^/wk 



Low Marsh 



Aboveground 



Rhizomes 



Roots 



420 



3,290 



210 



960 



5,490 



150 



1,320 



2,940 



370 



Total 



3,S20 



6,600 



4,630 



High Marsh 



Aboveground 



Rhizomes 



Roots 



630 



1,610 



910 



1,380 



3,400 



210 



1,260 



3,380 



160 



Total 



3,150 



4,990 



4,800 



The sewage sludge fertilizer used also contained phosphorus and other 

 materials, but additional experiments demonstrated that nitrogen was 

 the effective ingredient. 



38 



