Southeastern floodplain forests are species-rich ecosystems that respond to dynamic interactions between disturbance and hydrologic regimes. Large-scale natural disturbances such as hurricanes influence forest composition and structure not only by damaging and killing overstory trees, but also by altering environmental conditions on the forest floor. In this dissertation, I examined how the composition and structure of floodplain forest ecosystems are regulated by these disturbances, with a particular emphasis on understanding how large woody vines interact with natural disturbances in floodplain forest ecosystems. Lianas are a long-neglected aspect of floodplain forests that influence tree mortality, recruitment, and growth rates and may be responding to environmental changes. Long-term studies of forest dynamics in the Congaree National Park and the Savannah River floodplains in South Carolina, U.S.A., provide ideal settings to study the interactions of hydrologic and disturbance regimes in species-rich forests with a significant large woody vine component.