CHAPTER 4 



COKhUNITY METABOLISM 



Marshes have attracted the 

 attention of systems ecologists who 

 are interested in the transfers of 

 energy and matter in natural systems. 

 The salt rparshes of Georgia were among 

 the first ecological systems to be 

 studied as systerrs; Teal (1962) 

 synthesized information from studies 

 conducted at Sapelo Island under the 

 overall guidance of E.P. Odum. The 

 work of the Georgia group and others 

 studying the mid-Atlantic, southeast 

 and Gulf of Mexico coasts of the 

 United States has dominated our 

 thinking about wetlands, and only 

 recently have results of ecosystem- 

 level studies become available from 

 the New England marshes (Nixon and 

 Oviatt 1973a; Woodwell et al. 1977; 

 Valiela and Teal IS79; Welsh 1980; 

 Howarth and Teal 1980). No one yet 

 has compared systematically the 

 different types of marshes. Probably 

 the differences in tidal signature 

 (Figure 8), tidal range (Figure 9), 

 freshwater inflow (Nixon 1981) and 

 sediment type (Hill and Shearin 1970; 

 Cotnoir 1974) along the coast will 

 influence the metabolism as well as 

 the species composition of marshes. 

 Reviews of the amount of new 

 aboveground production by Spartina 

 alterniflora have already described 

 north-south gradients correlated with 

 solar energy input (Turner 1976) and 

 tidal range (Steever et al. 1976). 

 Most of the work on ecological 

 energetics and nutrient cycling has 

 emphasized the regularly flooded 

 S. al terniflor a zone (low marsh), 

 but some information is available on 

 the New England high marsh. 



36 



PRIMARY PRODUCTION 



The marsh in summer is a great 

 sward of green; productivity of the 

 grass is high. Ever since R.M. Harper 

 (1918) made what appears to be the 

 first measurements of Spartina growth 

 on the marshes of Long Island, 

 countless quadrats of vegetation have 

 been clipped and weighed all along the 

 U.S. coast (see reviews by Keefe 1972; 

 Turner 1976; and a bibliography 

 compiled by the U.S. Fish and Wildlife I 

 Service 1977). While researchers in 

 New England have not been as busy with 

 productivity measurements as their 

 colleagues to the south, even on the 

 high marsh (which has been less inten- 

 sively studied than the creek-bank 

 areas) enough measurements have been 

 made to establish that an impressive 

 amount of carbon is fixed each year 

 during the relatively short New 

 England growing season (Table 10). 



But production, measured by 

 harvesting the grass, is an 

 underestimate of the total energy or 

 carbon fixed by the plants. Some 

 growth will have been eaten; some will 

 have been lost as leaf fall, seed 

 dispersal, and organic exudates. All 

 will be missed in an end-of-the-season 

 harvest. There are various ways to 

 try to account for such losses (see 

 Turner 1976), and some of them have 

 been used by those working in New 

 England. Unfortunately, it appears 

 from a comparative study of commonly 

 used techniques that the choice of a 

 miethod for estimating production will 

 have a large influence on the results 



