Channel Migration and Vegetation Patterns in the Southeastern Coastal Plain

Abstract

Channel migration is a major determinant of vegetation patterns in the tower bottomlands of the southeastern‐coastal plain of the United States. Lateral channel movement creates new surfaces by point‐bar deposition and the filling in of abandoned channels. The new surfaces are rapidly colonized by flood‐tolerant, opportunistic species. Sediment deposited during subsequent years’ flooding raises young surfaces, making them less susceptible to inundation and more suitable for the establishment of less flood‐tolerant species that eventually replace the early arrivals. The continued presence of the young forest communities depends primarily on the formation of new surfaces by channel migration and the development of shallow swamps. Shallow swamps are formed when channel obstructions force water into the adjacent bottomlands, destroying forest stands and allowing the establishment of early successional species. Many of the streams in the southeastern coastal plain have been channelized. Stabilized channels limit the development of shallow swamps and preclude the formation of point bars and oxbow lakes. Therefore, the largest‐scale natural disturbance mechanism and the most important factor controlling spatial heterogeneity in the lower bottomland sites has been eliminated. Channelization will likely result in a shift towards a homogeneous floodplain forest composed of later successional mesic species that occupied the outer floodplain before channelization.