Low ridges with certain edaphic con- 

 ditions sometimes support a few white oak 

 ( Quercus alba) in Zone V associations. 

 Although tulip poplar ( Liriodendro n tul ip- 

 i fera ) is extremely rare in the study 

 area, it can occur in Zone V associations. 



Dominance types of other sites (12- 

 16) . Beech ( Fagus grandifolia ) or beech- 

 magnolia hammock is frequently the first 

 association encountered at the ecotone of 

 floodplain and upland. A beech "fringe" 

 is characteristic of many Piedmont allu- 

 vial floodplains. Since beech-southern 

 magnolia hammock also exists under seepage 

 conditions on the uplands (usually adja- 

 cent to the floodplains. Zone VI), the 

 high water tables of Zone V often enable 



these species (primarily beech) to grow on 

 "islands" (types 12, 13) and old natural 

 levee ridges (types 10,11).. Southern mag- 

 nolia ( Magnolia grandif lora ), however, is 

 rare on floodplains in the study arpi. 



In areas of ridge and swale topog- 

 raphy (type 14) (Figure 38), Zone V asso- 

 ciations occupy the higher elevations, 

 succeeding the associations of lower ele- 

 vations. Scour channels, because they 

 allow rapid drainage, frequently contain 

 Zone V species mixed with those of Zones 

 III and IV (type 16). This is similar to 

 the occurrence of live oak (and saw pal- 

 metto) at the "lip" or edge of banks and 

 scour channels. 



Figure 38. Narrow, long ridges between swales on the lower Roanoke floodplain (NC) of 

 probable late Pleistocene age have an almost diagrammatic zonation of Zone V hardwoods 

 beginning with diamondleaf oak at the edge of Zone II and progressing up through swamp 

 chestnut oak to cherrybark oak. 



67 



