The main objectives of this study were to identify a small of edaphic factors that could be related to vegetation distribution in a coastal dune salt marsh system in the Southeast of Spain and to establish a simple conceptual model to describe the relationships between these soil factors and the main plant communities. Soil and vegetation data were obtained from 87 sampling plots. The plant communities studied were dominated by Crucianella maritima, Teucrium dunense, Ammophila arenaria, Lygeum spartum, Schoenus nigricans, Juncus maritimus, Limonium cossonianum, Sarcocornia fruticosa, Arthrocnemum macrostachyum, and co-dominance of Sarcocornia fruticosa and Arthrocnemum macrostachyum. The first four communities occupied summit positions and the rest of communities interdune depressions. In addition, we sampled plots in bare soil at interdune depressions. The soil parameters studied were soil salinity, soil moisture, the ground-water level, the depth to gleyed matrix, and the distance to the shoreline. Soils at interdune depressions were consistently more saline, wetter, and with a shallower water table and gleyed matrix than soils at summit positions. Soil moisture, salinity, and the distance to the shoreline were parameters related to plant distribution at summit positions. However, at interdune depressions species distribution was mainly related to salinity, moisture, the depth of the ground water, and the depth to gleyed matrix. In the conceptual model proposed, bare soils are characterized by their extreme salinity in the growing season (spring) and a shallower ground-water level, which leads to a shallower gleyed matrix.