Salr marshes are important in contributing organic material to the bay and 

 in providing stability to the barrier by the formt»tioa of peat. Over many 

 years, salt marshes accumulate fine-grained sediment and organic material, 

 building cohesive peat. Peat prevents excessive scouring during overwash, 

 which could lead to inlet formation. Peat outcrops along the ocean beach also 

 slow shoreline erosion a i, as at the southern end of Nauset Spit-Eastham, 

 salt-marsh peat has apparently slowed the lateral, northward migration of 

 Nauset Inlet. 



Salt-marsh vegetation is generally not eroded by overwash surges. After 

 crossing the dune ?oae, surges slow due to flow divergence and essentially 

 stop where ponded bay waters are encountered. 



Salt-marsh plants on Nauset Spit-Eastham were buried by as much as 110 

 centimeters of sand. Only Spartina patens and Spartina altemiflora were able 

 to recover, in restricted areas, from more than 10 centimeters of overwash 

 deposition; Spartina patens recovered from up to 33 centimeters of burial. 

 Plants at prestorm high elevations recovered better than plants at lower 

 elevations. Data obtained from shallow wells indicated that the ground water 

 table is raised beneath washover deposits. Anaerobic conditions resulting 

 from waterlogging may limit the recovery of Spartina patens at low elevations 

 and in areas of deep burial. 



Spartina altemiflora recovered from as much as 22 centimeters of washover 

 sand in 1978. Unlike Spartina patens, burial recovery was best at lowest 

 elevations. Higher elevations are less frequently flooded and soil salinity 

 may increase beyond the tolerance levels of Spartvna altemiflora. 



Many of tb° Spartina patens and Spartina altemiflora plants that had 

 recovered from burial in 1978 were either dead or dying by 1980. The larvae 

 of a weevil had invaded the cortex of many Spartina altemiflora plants that 

 were yellow and dying; many Spartina patens plants that had recovered in 1978 

 were dead in 1980 and had rotted at a point 5 to 10 centimeters before the 

 surface. Sediment deposition may have raised the elevation-water table height 

 to a point that plant vigor was lost and waterlogging produced anaerobic con- 

 ditions, weakening and ultimately killing the plants. 



The aerial photography analysis indicated that salt marshes can form in 

 as little as 10 years on newly placed washovers, but nev; salt marshes do not 

 form on barren, intertidal washovers until overwash pressures are reduced. 

 Salt marshes are established either by rhizome outgrowth from recovering or 

 adjacent marsh plants, by plant fragments eroded from creek margins, or by 

 seed. Following overwash, both Spartinae are able to expand rapidly by 

 rhizome extension. Plants at the margins of washovers will colonize inter- 

 tidal washovers at a rate of approximately 1 meter per year. Blocks of salt- 

 marsh peat (mainly Spartina altemiflora) with living plants are frequently 

 eroded along creek margins and carried by tides to intertidal positions where 

 roots develop, anchoring the peat block. Many of these blocks are ice-rafted 

 to the upper range of Spartina altemiflora. Fragments of both Spartina 

 altemiflora and Spartina patens are also occasionally found among drift 

 material deposited following overwash at the outer margin of washovers 

 by spring tides. Spartina altemiflorVL seedlings in drift lines did not 

 survive the dry summers during the course of this study. Spartina patens 

 var. monogyna survived in drift lines and expanded energetically during the 

 following years. Seeds of both Spartina altemiflora and Spartina patens 



217 



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