swamp to become relatively wetter on the north side and drier on the south. 

 Water entering the swamp from the Acorn Hill drainage is now diverted into 

 the canal on the north side of the highway, where it flows easterly across 

 the swamp . 



A second important aspect of the hydrology of Dismal Swamp may be the 

 supply of water from aquifers below the surface with origins somewhere 

 above the Suffolk Scarp (Gammon & Garrett , pers. comm.)- Clearing of much 

 of the watershed for agriculture on the high lands above the swamp means 

 that rainfall may now run off rapidly through drainage ditches rather than 

 percolating slowly through forest litter into the ground to recharge these 

 aquifers. 



A third hydrologic factor for consideration is the general lowering of 

 the water table in the Dismal which was begun with ditch construction by 

 George Washington in the 18th century and has continued to the present day. 

 The combined effects of these changes have undoubtedly caused the fern site 

 to be considerably drier than in the original, undisturbed swamp. 



These water table changes may not necessarily have seriously affected 

 the rare Dryopteris populations however. The ferns occupy a topographic 

 position that is better drained than the wetter lands to the east. It is 

 quite possible that they existed in the virgin forest of the area on the 

 toe of the scarp and simply adjusted to their moisture needs by migrating 

 slowly downslope over the 200 years that the water table has been 

 declining in response to drainage. 



The complexity of the fern community and the general northern 

 affinities of most of the genus suggest that they are relicts from cooler 

 times at the end of the Wisconsin, protected here by the cool, moist 

 conditions at the foot of the Suffolk Scarp, 



IIB. Prose Description of Site Significance. 



This site contains a remarkable assemblage of ferns of the genus 

 Dryopteris . This grouping has already been the subject of several 

 scientific investigations. Of these, three species, plus an orchid, 

 Listera australis are listed as threatened in North Carolina. The 

 other 5 taxa of ferns are a group of disjunct and hybrid species, the 

 nature of which is still not understood. 



The swamp forest on this site is one of the more unusual in the 

 Dismal, being a mature stand, of a type on more mesic sites than the 

 generally hydric swamp forest which dominates the area. The difference 

 is due to its presence on the lowest portion of the toe of the 

 Suffolk Scarp, giving it a slightly better drainage situation. 



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