in this marsh. Detailed information on the composition and structure of 

 four of these vegetation types, Spartina patens , mixed, Juncus roemerianus , 

 and marginal types, are presented. These vegetation types are distin- 

 guishable in species composition or varying importance of certain species 

 and in certain habitat factors. Several habitat factors of the marsh 

 were studied. Information is presented on depth and salinity of standing 

 water, depth of peat layers, particle size distribution of the sand 

 substrate, elevations, and tidal fluctuation. 



The primary purpose of this investigation was to obtain estimates of 

 the net primary production of the major vascular plant species in an 

 irregularly flooded salt marsh. A harvest method was used to obtain standing 

 crop estimates of the major species for a two-year period. These standing 

 crop values were used to calculate net production. Net production was 

 calculated using two methods. The first method involved the use of only 

 the living standing crop estimates. Since this method produced under- 

 estimates of net production, a second method was used that took into 

 account changes in both the living and dead standing crops. Both of these 

 methods were applied to observed mean standing crops and to predicted 

 standing crop values obtained by fitting the observed data to a fourth 

 degree polynomial in time. The observed standing crop values were fitted 

 to the polynomial in an attempt to obtain a better description of the 

 growth of the major species over time. The fit of the data to the poly- 

 nomial was reasonably good for most species. 



The net primary production estimates obtained indicate that the 

 irregularly flooded marsh studied is not so productive, when considered 

 on a whole-marsh basis, as regularly flooded salt marshes. However, the 

 data collected in this study, which are comparable to that collected for 

 regularly flooded marshes, indicate that certain vegetation types in the 

 irregularly flooded marsh ( Spartina patens , mixed and Juncus roemerianus 

 types) are considerably more productive than short Spartina alterniflora 

 in regularly flooded marshes. None of the vegetation types in the irregu- 

 larly flooded marsh were as productive as the levee-streamside (medium and 

 tall) Spartina alterniflora of regularly flooded marshes. (A. A.) 



Keywords: primary productivity, salt marsh, Spartina , Juncus , 

 North Carolina 



II-B-19 



Williams, R.B., and M.B. Murdoch. 1969. The potential importance of 



Spartina alterniflora in conveying zinc, manganese and iron into estuarine 

 food chaiTiT! Pages 431-439 j£ D.J. Nelson, ed.. Proceedings of the Second 

 National Symposium on Radioecology. U.S. Atomic Energy Commission, 

 Washington, D.C. 



The potential importance of cord grass in conveying radioisotopes of 

 zinc, manganese, and iron into estuarine food chains was evaluated 

 on the basis of its annual production, its content of these elements, 



46 



