Year 



Peak biomass 

 gdw/ni2 



Net aboveground production 

 gdw/m2/yr 



1971 



1972 



1973 



3-year mean 



440 ± 60 

 350 ± 10 

 540 ± 120 

 440 ± 50 



620 ± 110 

 540 ± 170 

 730 ± 250 

 630 ± 50 



Although the authors concluded 

 that the differences among the years 

 were not statistically significant, a 

 simple estimate of the maximum 

 standing crop of grasses may appear 

 to vary by over 40% of the overall 

 mean during just 3 years of sampling. 

 In comparing the end-of-the season 

 biomass of creek-bank S^. alterniflora 

 during one year on 12 marshes in Rhode 

 Island (a very small area), we found 

 a range in that one year from 430 to 

 1,380 gdw/m2 (Nixon and Oviatt 1973b). 



NUTRIENTS AND PRIMARY PRODUCTION 



Of all the environmental 

 parameters that may influence primary 

 production on the New England high 

 marsh (see Chapter 3; Valiela and 

 Teal 1974; Niering and Warren 1980), 

 the most convincing evidence concerns 

 the importance of nitrogen as a 

 limiting factor. In replicated field 

 fertilization experiments carried out 

 over a number of years at Great 

 Sippewissett Marsh, Teal, Valiela, and 

 their coworkers have developed data 

 which show that nitrogen additions at 

 least as low as 0.8 g N/m^/week during 

 the growing season more than double 

 the aboveground production of S. 

 patens and Distichlis on the high 

 marsh. A similar effect was observed 

 with the low marsh S^. alterniflora 

 (Valiela and Teal 1974; Valiela et al. 

 1975, 1976). Phosphorus additions had 

 no effect on the production of any of 

 the species. In terms of belowground 

 production, the addition of nitrogen 

 reduced the development of roots by 



about 75%, but more than 

 production of rhizomes 

 Overall, the production 

 high marsh appeared 

 similar. 



doubled the 



(Table 11). 



of low and 



remarkably 



Since the fertilizer input was 

 maintained for about 6 months out of 

 e\/ery year, the total nitrogen supple- 

 ment in the Sippewissett Marsh experi- 

 ments amounted to about 20 g N/m^/yr 

 and 60 g N/m^/yr for low and high 

 treatment experimental plots, respec- 

 tively, on both regularly flooded and 

 high marsh. These inputs are large 

 compared with other nitrogen sources 

 and sinks on the marsh. Bacterial 

 nitrogen fixation on the high marsh at 

 Sippewissett is less than 5 g H/m^/yr 

 (Teal et al. 1979), but there is a net 

 loss of nitrogen to the atmosphere of 

 about 4 g N/m?/yr from denitrification 

 (Kaplan et al. 1979). 



FATE OF THE PRIMARY PRODUCTION 



Discovering the fate of the 

 organic carbon and associated 

 nitrogen, phosphorus, and other 

 materials that are fixed on the 

 high marsh each year is not simple, 

 appear to be few grazers 

 the grass, little is 

 directly into secondary 

 of terrestrial animal 

 Usually, the primary 

 either accumulates in 

 sediments as peat, decomposes in 

 marsh, or is exported by the 



Since there 



feeding on 



transferred 



production 



tissue. 



production 



the 



the 



tides to more 



coastal waters. 



open estuarine and 



41 



