c. An alysis of Data . 



(1) Dune Communities . 



(a) Comparison 1 . All 1,020 quadrats sampled at site 1 throat 

 In 1977 ( l-T-77) were compared with the same quadrats sampled in 1978 (l-T-78) 

 to determine the effect of overwash on a dune community that was removed by 

 erosion. Site 1 throat consisted of the washover throat with adjacent dunes 

 (Fig. 31). Cover data in 1977 show that the area was 86 percent bare sand 

 (Table 9). The edges of tlif throat were principally populated wj.th Ammophila 

 bveviligulata (I.V. = 131. 6) through the dunes and Spavtina patene var. 

 monogyna (I.V. = 110. 0) toward the sand road. The I.V. of Spavtina patene 

 was high because individual tillers grow more densely than any other plant on 

 Nauset Spit-Easthara. 



Only three quadrats sampled at site 1 throat were not eroded during the 

 February storm. The mean elevation of site 1 throat wa^ raised only 4 centi- 

 meters, but the elevation range was lowered from 2.98 centimeters to 1.65 cen- 

 timeters. Dunes were flattened (maximua elevation = 4.14 meters above mean 

 sea level (MSL) for '977, versus 3.32 meters above MSL for 197^), and low 

 areas were filled (lowest elevation = 1.16 meters above MSL for 1977, versus 

 1.67 meters above MSL for 1978). Mean net depth of sand burial was 0.11 meter 

 (±0.32 meter) for the entire site. Only 13 quadrats were vegetater. in 19/8 

 versus 324 quadrats in 1977 (Tables 9 and 15). Species richness was reduced 

 from 10 species in 1977 to 3 species in 1978. Species diversity was dramatic- 

 ally reduced from 0.6754 in 1977 to 0.0582 in 1978. 



Table 15. Summary of data collected from 969 quadrat samples at site 1 

 throat, August 1978. 



Species' 



Frequency 



Cover 



Density 



I.V. 



Pet Relative Pet Relative Total Relative 



Ammophila bveviligulata 1.2 80.0 0.1 97.2 54 85.7 262.9 

 Solidago eempevvivens 0.1 6.7 0.1 2.8 1 1.6 11.1 

 Svavtina patens 0.2 13.3 8 12.7 26.0 



Bare sand 



100. 



99.8 



'Diversity - 0.0582; Richness - 3. 

 I.V.'s arc importance values calculated from cover, frequency, and density 

 of the plants. 



Ammophila bveviligulata and Spavtina patens were codorainant9 in 1977; 

 but only Ammophila bveviligulata was dominant in 1978. Spavtina patens and 

 Solidago sempevvivens were found in quadrats that recovered from overwash 

 burial in 1978. Since the velocity of overwashing surges was greater at site 

 1 throat than in other areas not bordered by high dunes, only large driEt 

 material was deposited in the washover throat. Ammophila bveviligulata 

 rhizomes and tillers regenerated in these drift piles. Cakile edentula was 

 the only other species found in the area. In all cases there was a statisti- 

 cally significant decrease in both cover and density for each species in 1978 

 compared with 1977. In the site 1 throat comparison, an established dune 

 community was replaced by scattered plants found in drift piles on the wash- 

 over surface. The high similarity index (55.9) shows the high I.V. of 

 Ammophila bveviligulata in all supratidal areas on Nauset Spit-Eastham. 



77 



AVi. ^>\vw\Kf\*s?wsK3£saasias. i s naas •& krsm Maxima s» 



•". SsiTJ-KT; c.*«r.--»»-«isr- 



