wet-tolerant, occasionally found as a co- 

 dominant with swamp tupelo (type 10), and 

 rarely can be found mixed with a few 

 cypress. 



Floodplain flats dominance types (1- 

 10) . The diamondleaf oak dominates the 

 Zone IV flats of all the major river 

 types. Even so, these forests are more 

 diverse than the wetter overcup oak-water 

 hickory types in Zone III. Frequent 

 associates in this zone are green ash 

 ( Fraxinus pennsyl vanica ), American elm 

 ( Ulnus americana ), sweetgum ( Liquidamber 

 styraciflua ) (TTgure 33) and, less com- 

 monly, sugarberry ( Celtis laevigata ). The 

 swamp palm ( Sabal minor ) (Figure 34) is a 

 good general indicator species for this 

 zone, as is possum haw ( Ilex decidua ), 

 Walter's viburnum ( Viburnum obovatum ) and 

 various hawthorns ( Crataegus spp. ). Occa- 

 sionally, the spruce pine ( Pinus glab ra) 

 occurs although it is considered to be 

 associated with lowest elevations of Zone 

 V. It has a wide moisture tolerance and 

 may occur with diamond! eaf oak on both 

 alluvial (type 9) and blackwater (type 10) 

 floodplains. 



Dominance types on other sites (11- 

 17) . Zone IV oaks (diamondleaf , willow) 

 occur in a variety of other situations: 

 scour channels (type 13), ridges of ridge 

 and swale topography (type 14), and the 

 lower elevations of relict dune ridges 

 (types 15, 16) where they occasionally mix 

 with wet variants of live oak. Narrow 

 sandy ridges (type 15) may bear shrubs 

 that are not usually considered wetland 

 species: wild olive (Osmanthus), yaupon 

 ( Ilex yomitoria ) and saw palmetto ( Serenoa 

 repensT 



The reader should be cautioned that 

 delineating Zones IV and V on some black- 

 water and Piedmont rivers can be confus- 

 ing. Due to the sandy soils of some 

 blackwater floodplains, microedaphic and 

 microtopographic mosaics become even more 

 divided. On some floodplains (Zone IV, 

 type 10) an apparent mix of Zone IV and V 

 species may occur (Figure 35). On Piedmont 

 floodplains, owing to the numerous scour 

 channels and fast-draining clay soils, 

 there also may be this apparent mix of 

 Zones IV and V to the casual observer. 



Dominance Types of Zone V 



Zone V comprises the highest eleva- 

 tion floodplain associations occurring on 

 old natural levees, flats, higher ter- 

 races, and Pleistocene ridges and dunes. 

 Inundation averages once yearly (Congaree, 

 SC). See Figure 11 for graphic example. 

 Duration of flooding ranges from 2% (5.3 

 days) to 12.5% (33 days) of a 265-day 

 growing season. Soils are usually sandier 

 and less fertile than those of lower 

 zones. 



Zone V dominance types observed in 

 the study area are listed in Table 14. 

 Zone V associations appear to dominate 

 many Piedmont floodplains; however, in the 

 Coastal Plain these associations may be 

 restricted to 5% to 10* of the floodplain 

 surface. As in Zone IV, the plant asso- 

 ciations grow on both Pleistocene and 

 Holocene floodplain surfaces. Understory 

 species are more conspicuous in this zone. 

 In fact, two understory species, the paw 

 paw ( Asimina triloba ), a subcanopy tree, 

 and river cane ( Arundinaria gigantea ) are 

 generally good indicator species. River 

 cane is most luxurious in this zone al- 

 though dwarfed stands grow in Zone IV. 

 The diversity of both herbs and shrubs is 

 maximal in this zone. 



Zone V flats and old levee ridge dom- 

 inance types (1-11) (Figures 36 and 37). 

 Two hardwood species are characteristic 

 and widely distributed: swamp chestnut or 

 cow oak ( Quercus michauxii ) and cherrybark 

 oak (Q. pagoda ). Water oak (^. nigra ) 

 occasionally occurs as a co-dominant spe- 

 cies in these associations. Two pines are 

 present: spruce pine at the wetter end of 

 the spectrum and loblolly ( Pinus taeda ) at 

 the drier end. In the Congaree, record 

 loblolly pines grow on old levee ridges 

 slightly elevated above Zone IV surfaces 

 (Figure 36). Spruce pine seems to require 

 a more continuous water supply and even 

 occurs on upland slopes under seepage 

 conditions. Some species that are wide- 

 spread on the uplands apparently can adapt 

 to the floodplain conditions of Zone V. 

 Some hickories are common in Zone V over 

 clay-rich subsoil sites (types 6-8) and, 

 rarely, form hickory flats (type 6). 



60 



