The observed response of trees to hydrologic stress and distribution of trees in relation to habitat indicate that flooding, ground-water level, soil moisture, soil factors, and drainage characteristics exert a strong influence on bottomland forest species distribution. The dominant hydrologic factor influencing the distribution of bottomland tree species is flooding. Individual tree species are distributed as a function of frequency and duration of flooding. In the lower White and Ouachita River basins, the flood plains consist of a series of terraces, progressively higher terraces having less frequent flooding and less duration of flooding, and a significantly different composition of forest tree species. The sites studied can be divided into four basic groups and several subgroups on the basis of flood characteristics. On Group I (water hickory-overcup oak) sites, flooded near annually 32 to 40 percent of the time, the dominant species are water hickory and overcup oak. On Group II (nuttall oak) sites, flooded near annually 10 to 21 percent of the time, a more varied flora exists including nuttall oak, willow oak, sweetgum, southern hackberry, and American elm. The third group (Group III or shagbark hickory-southern red oak) of sites is flooded at intervals from 2 to 12 years. This group includes southern red oak, shagbark hickory, and black gum. The presence of blackjack oak in addition to Group III species marks Group IV (not flooded in historic time). (Kosco-USGS)
