A 1977 washover that was buried by additional washover sand in 1978 was 

 analyzed (Fig. 35, comparison 4). Small dunes had developed on this washover, 

 which were sampled in 1977 and subsequently eroded in February 1978. Quadrats 

 sampled in 1977 were compared to the same quadrats in 1978. 



Six comparisons were made for salt-marsh communities (Fig. 35). Two of 

 these comparisons involved mixed high or low marsh areas that were subject to 

 shallow burial which allowed regrowth from below the fan surface during the 

 first year (comparisons 5 and 6). In comparison 5, quadrats sampled in 1978 

 in areas of site 1 fan that were buried by less than 34 centimeters were 

 compared with the same quadrats before overwash. Quadrats on a 5-year-old 

 washover were compared with quadrats from an adjacent, unaffected area in 

 comparison 6. Three comparisons were made between preoverwash and postover- 

 wash surveys of marshes that had been buried oy more than 34 centimeters of 

 washover sand. In two of these analyses, 1977 data were compared with 1978 

 data; the third comparison used 1977 data on an area initially -overwashed in 

 1972. The final analysis compared a mixed high and low salt marsh to the same 

 area after overwash in February 1978. This area continued to overwash during 

 spring tides until July (comparison 10). Quadrat3 sampled in 1977 were 

 compared with the same quadrats resampled in 1978. 



For each comparison, vegetation data tables were compiled per site, indi- 

 cating relative frequency, cover, density, and I.V. for each species. The 

 species diversity was calculated using tne Simpson indt=x (Simpson, 1949), 

 which is weighted for more common species. A similarity index was calculated 

 comparing the two sites, using a modification of the Gleason similarity index 

 (Gleason, 1920). 



2W 

 Gleason index 



a + b 



where W is the sum of the least relative covers of species held in common 

 between the two plots. W is multiplied by 2 because this cover calculation 

 occurs in both plots; a and b are the sum of the total cover values for 

 each plot. Importance values were used ra< her than relative cover in order 

 to take advantage of the more detailed data collected. Using the elevation 

 points surveyed in 1977 and 1978 for each site, means, standard deviation, and 

 ranges were calculated for elevation and sand deposition. Whenever appropri- 

 ate, individual species were compared between sites using the Kruskal-Wallis 

 test, a modified t-test for nonparametric data (Kruskal and Wallis, 1952; 

 Dixon, 1977). The Kruskal-Wailis test ranks data for each treatment and 

 compares each level of the ranking. 



A two-dimensional ordination of all vegetation data collected on Nauset 

 Spit-Eastham during 1977 and 1978 was constructed using a method developed by 

 Beals (1960). Vegetation data were divided into 13 plot groupings in 1978 so 

 all sampled quadrats were included only once. Descriptions of the 13 sites 

 used for the ordination appear in Table 13. A matrix of similarity indexes 

 for all sites was constructed using the modified Gleason index used in the 

 site comparisons (Table 14). 



75 





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