JCJ" 



support salt-uiarsh vegetation. Dunes also reduce salt-spray intensity, 

 which allows the establishment of salt-intolerant species to the lee of this 

 barrier. Finally, dunes act as sediment reservoirs for both nourishment of 

 beaches during storms and for washover deposits. During storms some of the 

 sediment removed from the i-each by wave activity is replaced by dune-face 

 erosion. Surges that cross the berm crest carry beach and eroded dune sedi- 

 ment to landward positions. This sediment is reworked by the wind duri.ng 

 interstora periods. On Nauset Spit, prevailing winds transport much of the 

 washover sediment eastward. Remnant and newly established dunes trap some of 

 this sand, eventually recreating a continuous dune line. 



In 1978 the dune line at Nauset Spit-Eastham was high and almost contin- 

 uous. Most of the dunes along Nauset Spit-Easthaia affected by the February 

 1978 overwash were leveled and the vegetative surface was eroded. Some sec- 

 tions of the dune at site 3 were, however, buried by up to 67 centimeters of 

 overwash sand without disturbing the vegetative surface. The four major dune 

 species found on the Nauset Spit system, Armnopkila breviligulata, Artemisia 

 stellev'-aruz, Lathyvus japonicus, and Solidxxgo sempevvirens, were present in 

 quadrats sampled before and after overwash at this location. All four species 

 were able to recover from deep overwash burial. Washover deposition equaled 

 typical high, annual evels of wind-transported sand deposition in dunes. On 

 low-lying, well-vegetated dunes, overwash plays an important role in dune 

 building. 



Following overwash, wind deflation of extensive washover flats aids in 

 the redevelopment of the dune line. At Nauset Spit the prevailing sand- 

 transpcrting winds move sand offshore; remnant dunes trap much of the material 

 deflated from washovers. Along the outer edges of the washover, drift mate- 

 rial is deposited, by spring high tides. Sand reworked from the v;a3hover also 

 accumulates differentially in the vicinity of emerging drift-line plants, thus 

 building new dunes on the fan surface through time. 



Shrub communities are found in areas of North Beach protected from salt 

 spray. The frequency of shrubs decreases with distao.ce from the glacial head- 

 lands at Nauset Heights, reflecting a decrease in stability of the barrier and 

 a decrease in propagule availability. Shrubs have little importance in the 

 maintenance of the physical stability of the barrier since a cohesive sub- 

 strate has not been developed that could appreciably slow erosion and downward 

 cutting during major storms. 



Many of the shrubs on northeast barrier beaches appear to recover from 

 overwash burial. Rosa rugosa, Myrica pensylvanic-a, and Prunus maritima, major 

 shrub species on Nauset, survived burial of lower plant parts. Changes in 

 water-table height caused by increased elevation may lead to anaerobic con- 

 ditions in the shrub root zones; therefore, overwash deposition may eventually 

 kill these plants. Major shrub communities on Nauset do not appear to grow 

 through washover sediment and reestablish a shrub community. isolated plants 

 have recovered, however, and have survived burial for many years. 



An aerial photography analysis indicated that shrub communities became 

 established on new washover substrate in as little as 26 years. On Nauset, 

 shrub species generally invade bare, stable washover pediment that is 

 protected from high levels of salt spray. Ammophila breviligulata may have 

 grown briefly in the area, but undoubtedly does not alter the sandy surface 

 appreciably. 



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