The Factors of Swamp Spatial Patterns

A state factor model of bottomland hardwood swamp formation is applied to a lower coastal plain river in North Carolina, U.S., to explain variations in wetland hydrological, ecological, geomorphological, and soil characteristics. Swamps and wetlands are a function of the interacting influences of the state factors of climate, topography, hydrology, vegetation, fauna, soils, geomorphic setting, and time. Five classifications of swamp and related environments were applied to the study area, with the categories present determined based on fieldwork. For each classification, the implicit, embedded state factors were identified from the classification scheme itself. Relevant environmental gradients for the study area were identified, and a spatial adjacency graph for the study area was developed for each classification. The ability of the environmental gradients to explain the spatial complexity of the pattern was assessed using spatial adjacency graph (SAG) analysis. All the classification criteria are associated with the proposed state factors. SAG analysis shows overdetermination, indicating that known gradients of causal factors are sufficient to explain the overall pattern of spatial contiguity and that single-factor models of change are not sufficient at the local scale. Results confirm studies showing that responses to sea-level and other changes are spatially patchy.