■ , . ^ „^, ct, . .... , « ; .. ;.^; ■» . . ym.. ,~.;vx i K | ».^«. I -.. " < ■.' I Jfn ,-^^^, 



Rapidly accreting dunes are dominated by Ammopkila bveviligulata, with 

 Labhy'vuB japonicus and Soliaago se.mpevvivens as s ubd oral nan ts. /Jvtemisia 

 stelleviana was the dominant species (I.V. ■ 130.3) in site 3 before over- 

 wash. This area had been stable, receiving little wind-transported sand. 

 Ammophila bveviligulata is frequently reported to grow poorly in stable dune 

 areas such as site 3 in 1977 (Ranwell, 1964). Overwash in 1978 increased 

 Ammophila bveviligulata cover and density in relation to other species and 

 revived dune building. Avtemisia stelleviana is likely to decline in 

 importance as dunes continue to develop. 



The data available for analysis in the dune community on Nauset Soit- 

 Eastham are representative of the range of possible dune areas affected by 

 overwash activity. Dune communities on a barrier beach are restricted to 

 areas above certain minimum elevations. On the ocean and bay side of che 

 barrier beach, dune vegetation is limited to those areas n <t inundated by 

 tides during the growing season. In the interior of the dune riel!, Ammophila 

 bveviligulata, the principal dune species, is restricted to are.i that are not 

 water-logged due to watet-table conditions. There is not a maximum elevation 

 at which Ammophila bveviligulata will grow; it is found on sand dunes t£ more 

 than 50 meters. Other dune species are limited by their ability tt grow 

 through continuous sand burial, or less frequently, through large amounts of 

 sand burial from overwash activity. Biomass levels in dune areas are not 

 correlated with elevation. \mmophila bveviligulata., which grows poorly on 

 dunes that are partially inundated by tides or at low elevations, does not 

 necessarily grew better on the highest dunes. Ammophila bveviligulata grows 

 best on seaward dune slopes (van der Valk, 1974) and in areas that uceivp 

 continuous sand burial (Ranwell, 1975). Ammophila bveviligulata rapidly loses 

 vigor on high dunes that are not accreting. 



Although only a limited number of supratidal quadrats (137) in site 3 

 throat were not eroded by the February 1978 northeaster, this area does 

 represent typical dunes affected by overwash processes. The four major 

 dune species on Nauset Spit-Eostham were present in sufficient numbers for 

 analysis. 



(2) Salt-Marsh Species . Site 1 was the only sampled area that had 

 low-level overwash burial and plant recovery in the salt marsh. Sand depo- 

 sition ranged from 6 to 118 centimeters. Spavtina patens and Spavtina 

 altevniflova in 134 quadrats recovered from 6 to 33 centimeters of burial. 

 Data from site 2 and site 3 yielded little information concerning the vege- 

 tative response to overwash activity; it was shown, however, that salt-marah 

 plants do not recover from 33 centimeters or more of overwesh burial (.site 3) 

 or from continuous overwash during the growing season (site 2). 



Salt-marsh species distribution is highly correlated to elevation. Salt- 

 marsh plants do not grow below MSL and do not grow above spring high water 

 (Redfield, 1972), with the exception of Spavtina patens (var. monogyna) which 

 grows on low-lying dunes. Unlike dune species, biomass levels for individual 

 salt-marsh species are highly correlated to elevation. Spavtina altevniflova 

 grows best at the lowest elevations within its range. A band r>f Spavtina 

 patens occurs at the high elevations in the salt marsh, but Spavtina patens 

 grows best at the lower elevations within its range, when not coexisting with 

 Spavtina altevniflova. Density data for both epecies are highly correlated 

 with elevation. 



104 



