A wide variety of invertebrates, fish, amphibians, reptiles, birds, and mammals occur in the southern floodplain forest. Groundwater levels and flooding determine the type and productivity of vegetation in the southern floodplain forest. Hydroperiod ultimately limits species composition. Flooding during the growing season has a greater effect on species survival than during the nongrowing season. Climatic climax communities rarely occur in southern floodplain forests because of the dynamic nature of the ecosystem.
Successional trends are complex, and it is difficult to define distinct seral community stages.
However, newly-formed sandbars along stream and river margins are generally colonized by black willow, black cottonwood, sugar maple, and river birch. Cypress and tupelo stands grow best on sites inundated for long periods and persist indefinitely on these sites. On poorly drained sites overcup oak and water hickory stands can be interspersed with cypress and tupelo. Willow sprouts with frequent fire.