As shown by the ordination (Figs. 3, 4, and 5), some plant 

 communities are strongly delimited while others are similar. The 

 distinct communities include the foredune community, which has been 

 established on the artificially stabilized foredune and enriched by a 

 series of plantings. This community, though quantitatively unique, 

 has its component species represented in almost half of the other 

 communities (49 percent). Hence, the species growing on the foredune 

 are not restricted there, but represent those species able to resist 

 the harsh environmental conditions of this habitat. The selecting 

 factors appear to be strong winds, the accompanying salt spray, sand 

 abrasion, and evaporative stress, as well as low nutrient levels and 

 extreme temperatures. 



The wetlands community on the soiind side of the study area was the 

 most unique community. There were 21 species in this community, of 

 which 16 were found nowhere else, and 3 others in only one additional 

 community. The aquatic nature of these sites has produced the 

 environmental factors so extremely different from those generally 

 found at Duck, which easily explains its uniqueness as well as its 

 species abundance. 



Two shrub-dominated communities, the oceanside shrub and sound 

 side shrub communities, occur at Duck. In the X-Y aspect of the 

 ordination (Fig. 3), these two communities occur close to one another 

 and widely separated from all other communities. A similar impression 

 is given in the Y-Z aspect (Fig. 5), although they are further apart, 

 while the X-Z aspect (Fig. 4) shows them at opposite ends of the Z 

 axis. These communities are unique, but six of the seven species 

 comprising the oceanside shrub community also occur in the sound-side 

 shrub community. The seventh,, though not sampled was observed growing 

 in the sound-side shrub. The major difference between these communities 

 is the richness of the sound-side shrub community (28 species) and the 

 dominance of M. pensylvaniaa in the oceanside shrub community. 



It appears that the oceanside shrub community exists where it does 

 due to the sheltering effect of the foredune. Conditions here are 

 still severe enough to exclude all but the hardiest members of the 

 sound-side shrub community. The oceanside shrub, which appears to be 

 an early successional stage of what could become like the sound-side 

 shrub community, is likely to remain in an arrested condition 

 until it is destroyed by prevailing shoreline dynamics. 



The sound-side shrub community is a middle successional stage of 

 what could become a maritime forest (Wells, 1938), The only significant 

 species not included in the samples was Queraus vtrgin-tana (live oak) 

 which was represented in the community with a small number of scattered 

 saplings. 



The sound-side disturbed community's samples included 24 species, 

 of which 14 were also found in the sound-side shrub community. Six of 



74 



