occurred while dune species ware dormant. Deposition did not exceed typical 

 rates of aeolian accretion on dunes. Saltwater accompanying the overwash 

 surges percolated through the highly porous dune sand and was leached by heavy 

 rains accompanying the storm. The species that recovered from overwash burial 

 were the same species commonly found on accreting foredunes. 



The season that overwash occurs must play an important role in the dune 

 community response to burial. In May 1977 and again in June 1977, north- 

 easters resulted in overwash at Nauset Spit-Eastham. Overwash surges pene- 

 trated the dune line at site 3, creating the small breach and washover that 

 were present in summer 1977. Ammophita bveviligulata and Lathy vus japoniaus 

 in site 3 and Armophila in areas south of site 3 were killed wherever flooded 

 by saltwater. The overwash event in September 1976 (that created site 2), 

 however, did not kill flooded Ammophita. Young dune plants or dune plants 

 that have recently broken dormancy have tissue that is susceptible to daaage 

 from saltwater exposure. Older plants are better able to withstand contact 

 with saltwater. Therefore, overwash burial on a dune comsunity in the early 

 part of the growing season may kill most of the plants. Overwash at other 

 times during the year, however, may not hinder growth and, in fact, may aid in j 

 the dune-building process by adding large volumes of sand to existing dunes. | 



i 



Salt-marsh vegetation on Nauset Spit-Eastham did not grow through washover 

 deposits greater than 33 centimeters deep. In areas where deposition was 

 less than 33 centimeters only Spartina patens and Spartina alterniflora, the 

 two major plant species in the high and low marsh communities, were able to 

 recover. Spartina patens cover and density were significantly reduced by ; 

 overwash deposition of sand. Cover and density of Spartina altevni flora were, 

 however, not reduced in areas receiving shallow burial. Spartina altermiflora 

 is the principal plant species in the lower salt marsh, where substantial nat- 

 ural siltation takes place. Annual deposition of silt, as much as 20 centi- f 

 meters, has been recorded tor sosse British sites (Chapasn, 1976). Spartina t 



altermiflora is adapted to high siltation rates and may, therefore, be well ' t 

 adapted to recovery from occasional burial from overwash. In all cases, 

 species number in recovering salt-marsh communities ia reduced by shallow i 

 overwash burial. Species aot recovering froa overwash burial may, by oaans of 

 r hi zona; extension from the surrounding orfrsh areas or by seedling establish- 

 ment, recolonize fringe areas of washover features within 5 years of an over- » 

 wash. The topographic relief in marshes is increased following overwash due £ 

 to the presence of storm drift piles. r 



I 



Salt-sarsh vegetation that Is buried by more than 34 centiaeters of wash- 

 over sand d-jes not recover. Holes dug in the substrate reveal that, in most 

 cases, regrowth is never initiated by plants that do not recover froa over- 

 wash burial. Species composition in all documented cases coapletely changed » 

 from preoverwash to postoverwash. Topographic relief was increased in asrsh 

 areas subject to deep burial. On washovers that are continuously subject to } 

 oveiwash, salt-marsh species do not recover fcom burial although they (say 

 periodically be exposed by such activity. •' 



The three caajor sites chosen for study on Nauset Spit-EasthEiu presented a ', 



variety of comparisons that could be sade between preoverwash end postoverwash '" 



consnsunities. Because the areas ware located principally in the dunes and in r 



near-dune marshes, certain plant communities were present that would not have g 

 been considered if a random selection of sites had been used. Host of the 



- \ * ■ • - ' ''••',-. • • -' 



