Figure 20. A windthrown diamondleaf oak on a small blackwater creek floodplain (Creep- 

 ing Swamp, NC) illustrates the large diameter of the root crown of bottomland hard- 

 woods. The thickness ranged from 30 to 46 cm (12 to 18 inches). Such width is probably 

 an adaptation to the high water table, but it also increases contact with the surface 

 water during inundation. Root mats are so wide that few areas of floodplain surface 

 are unprotected from floodplain scour. 



The importance of flood duration 

 should be obvious. With the exception of 

 species of tupelo and cypress, stresses 

 associated with saturated soils and stand- 

 ing water cannot be handled by plants 

 after varying amounts of time that depend 

 on the range of tolerance mechanisms of 

 the individual species. Broadfoot and 

 Williston (1973) stated that the majority 

 'of the bottomland species will not survive 

 2 years of continuous flooding. 



Factors that increase the dissolved 

 oxygen concentrations in floodwaters are 

 rainfall (Broadfoot 1967), moving water 

 (Hook et al. 1970; Harms 1973), and lower 

 water temperatures (Broadfoot and Willis- 

 ton 1973). In contrast, oxygen concentra- 

 tions may be reduced through microorgan- 

 ismal respiration, especially in waters 

 with high concentrations of organic matter 

 or nutrients or both. 



36 



