Chemistry of wet soils (Pearsall and Mortimer 1939; Patrick and 

 Mikkelsen 1971; Ponnamperuma 1972; Patrick and Delaune 1976; and 

 Faulkner et al . 1991), and the various physiological effects on vegeta- 

 tion under reducing conditions are well documented (Cannon and Free 

 1920; Conway 1940; Dubinina 1961; Hosner and Boyce 1962; Hook and Brown 

 1973; Hook and Scholtens 1978; Vester 1972; and Hook and Crawford 1980). 



Zonation of Bottomland Forests 



The hydrologic gradient in bottomland forests ranges from zones of 

 nearly continuous inundation/saturation in deep swamps to infrequent 

 inundation/saturation events for brief periods on upland sites. Because 

 different species respond to different timing and duration of inunda- 

 tion, a strong correlation exists between the distribution of a species 

 and its associated hydrologic and soil-moisture conditions (Hosner and 

 Boyce 1962; Dickson, Hosner, and Hosley 1965; Bedinger 1971, 1978; 

 Larson et al . 1981; Best, Segal, and Wolfe 1990; and Faulkner et al . 

 1991) . The National Wetlands Technical Council (NWTC) proposed the 

 zonal classification of floodplain forests (Clark and Benforado 1981) . 

 The classification system defined six hydrologic zones based on fre- 

 quency and duration of inundation and soil saturation (Figure 1) and 

 provides the basis for testing in this study. 



Larson et al . (1981) summarized the works of others on the occur- 

 rence of plant species in the Gulf Coastal Plain from 238 belt transects 

 in Texas, Louisiana, Arkansas, Mississippi, Alabama, and Florida accord- 

 ing to their maximum tolerance to soil -moisture or hydrologic regimes. 

 Larson and his cohorts developed a list of 79 tree and shrub species 

 associated with one or more of the NWTC hydrologic zones. However, the 



