| 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. Understanding how forests respond to natural disturbance will help scientists and resource managers develop and design restoration and management strategies and techniques that emulate the outcomes of natural disturbances.; During the twelve years following Hurricane Hugo in 1989 devastated portions of the old-growth floodplain forest of the Congaree National Park, liana communities have responded to the changes in forest structure. Liana community densities were determined across hydrologic and disturbance gradients in eight 1-ha plots that were established during the winter and spring 1989-90, and re-sampled in 1994, 1998, and 2002. In heavily damaged bottomland hardwood forests, liana densities initially decreased when the host trees were severely damaged but exceeded pre-hurricane densities after twelve years. Stem densities of Toxicodendron radicans, the most common liana, initially decreased by 55% in the most heavily damaged bottomland hardwood forests. In both low- and high-damaged hardwood forests, vine communities experienced increasing recruitment rates and decreasing mortality rates after twelve years. When compared with trees and shrubs, lianas have higher stem mortality rates (5-6% yr-1 over 12 yr) regardless of size in the Congaree floodplain forest. Liana diameter growth rates continue to reflect size- and species-specific differences, as well as colonization patterns and post-hurricane host damage. (Abstract shortened by UMI.)... |
