govern this production are: (1) tidal submergence, (2) marsh physiog- 

 raphy, (3) climatic conditions, (4) salinity, and (5) soil nutrient 

 concentrations. (A. A. -modified) 



Keywords: primary productivity, salinity, soil composition, salt 

 marsh, Virginia 



II-B-25 



Wise, E.A. 1970. A study of energy fixation and net production of 



plant communities in salt marshes of Back River, Virginia. Ph.D. 



Thesis, University of Illinois at Urbana-Champaign. 



This study concerned salt marsh community types along Back River, 

 Virginia, an estuary off lower Chesapeake Bay. Intertidal communities 

 were flooded twice daily, while high marsh communities were intermittently 

 flooded. Mean salinity of tidal waters was about 60 percent that of sea 

 water. Salinity conditions at all sites studied fell within the range of 

 adaptation of all species in the marsh. 



High marsh community types were distributed in a mosaic pattern, 

 with length of inundation being the major controlling factor. Spartina 

 alterni flora , tall, was found only in the intertidal zone and occurred 

 in pure stands. Community types found on the most frequently inundated 

 sites in the high marsh were Spartina alterni flora , dwarf form, Juncus 

 roemerianus , and Distichlis spicata . Iva frutescens and Spartina patens 

 community types occupied the best-drained sites. Salicornia europaea and 

 Spartina patens-Distichlis spicata community types were frequently 

 inundated. 



In certain high marsh communities, there were changes in percentage 

 composition by species during the study, with submergence-tolerant 

 species being replaced by those less tolerant of submergence. This appeared 

 to indicate accumulation and aggradation. Mean organic matter content of 

 the substrate was lowest under Spartina alterni flora , tall, and highest 

 under Spartina patens . 



Net primary production per unit area by community types in 1966 was, 

 from high to low: Juncus roemerianus , Distichlis spicata , Spartina 

 patens , Spartina patens-Distichlis spicata , Spartina alterniflora , tal 1 , 

 mixed, Spartina alterniflora , dwarf form, Salicornia europaea , and Atriplex 

 patula . For 1967 the order was Juncus roemerianus , Iva frutescens (added 

 in 1967), Distichlis spicata , Spartina alterniflora , tall, Spartina patens- 

 Distichlis spicata , Spartina patens , Spartina alterniflora , dwarf form, 

 mixed, Atriplex patula-Iva frutescen s, and Salicornia europaea . Part of 

 the Spartina alterniflora , tall, and the mixed community types was 

 removed by wave and tidal action before maturity. 



52 



