organic material and seeds were not carried by overwash surges beyond the 

 area. Site 3 throat drift material contained Ammophila breviligulata, 

 Artemisia stelleriana, Lathyvus japonieus, Cakile edentula, and Salsola kali. 

 The effect of overwash in a dune area, which was partly sroded and partly 

 buried, is to reduce biomass. The extremely high similarity index (76.2) 

 supports ocher data that major species relationships are, however, not 

 dramatically altered by overwash. 



(c) Comparison 3 . The sampled quadrats at site 3 throat that 

 were not eroded in 1978 were compared with the same quadrats sampled in 1977 

 to determine the effect of overwash on a dune community that had been buried. 

 Vegetation data for this site in 1977 and 1973 appear in Tables 17 and 18. A 

 map of the location of the uneroded dune area is shown in Figure 36. The 

 south and west sides of the area were not eroded. Much of the dense Ammophila 

 breviligulata in the 1977 plot was buried. Artemisia stelleriana (I.V. = 

 130.3) and Anmophila breviligulata (l.V. = 108.8) were codominants in 1977, 

 with Lathy rue japonieus (I.V. = 27.6) and Holidago sempervirens (I.V. = 19.3) 

 subdominants. In 1977, 59 percent of the area was vegetated versus 17 percent 

 in 1973. Mean elevation was raised 28 centimeters from 1977 to 1978. Eleva- 

 tion standard deviation comparisons between 1977 (arO.30 meter) and 1978 (±0.12 

 meter) showed that even affected dunes that remained intact after a major 

 storm were effectively flattened by overwash. Mean sand burial depth in the 

 area was 0.31 meter (o - 0.14 mPter) with a range from 1 to 98 centimeters. 

 Species richness was reduced from 10 to 5 species. Species diversity was high 

 for both years (0.6750 for 1973 and 0.6346 for 1977) and more similar than the 

 comparisons for the entire site 3 throat. All four dominant species were 

 able to recover from substantial overwash burial. Kruskal-Wallls tests were 

 run for cover and density data for all four species. Cover and density for 

 Ammophila breviligulata and Artemisia stellen'.ana were significantly reduced 

 ( 1' < 0.01) between 1977 and 1978. Lathyvus japonieus data were also signifi- 

 cantly reduced (P < 0.05). Tnere were no significant differences between 1977 

 and 1978 data for Solidago sempervirens (P > 0.05). Most of the vegetation in 

 the eroded section of site 3 throat originated from plants recovering from 

 overwash burial. Three quadrats with Ammophila breviligulata and three quad- 

 rats with Cakile edentula were found in drift material among the recovering 

 vegetation. Comparisons of an uneroded dune before and after overwash burial 

 showed that biomass was reduced significantly but that dominant species 

 remained the same. Only minor elements of the original community were elimi- 

 nated by overwash pressure. A high similarity index (83.6) substantiates the 

 similarity of the buried dune community to the original community. 



(2) Drift Communities . 



Comparison 4 . During the 1977 sampling period, site 1 fan quad- 

 rats were divided into three parts: (a) the area unaffected by overwash, 

 referred to as the adjacent marsh area (site l-F-m-77); (b) the area affected 

 by overwash where no vegetation grew, referred to as tha wa3hover area (site 

 l-F-w-77); and (c) the area where vegetation either grew through the deposit, 

 or where plants from the adjacent marsh were able to colonize by rhizome 

 extension, referred to as the peripheral area (site l-F-p-77). A niap of the 

 subdivisions of site 1 fan in 1977 appears in Figure 29. Quadrats sampled 

 in site l-F-w-77 were compared with the same quadrats resampled after the 

 February storm in order to determine the effect of overwash on an area that 

 had previously overwashed. Vegetation data for the two sampling periods 

 appear in Tabies 7 and 19. Test pits, dug in the fan where vegetation had 

 been present in 1977, demonstrated that all plants on the original washover 

 surface had been eroded by the storm. 



79 



.'■ ■- ■..'■ -,"■ *"„> %" *,/* «„" -V"'"\Y^.." -" J ." :i . i v*, '"^'l ^ ?-""Y*>""W* 



' V 



~37. 



■fa 



