The Distribution of Salt Pans on Tidal Salt Marshes

The widely accepted view that salt pans are formed during the initial colonization of the marsh surface is examined using a large sample of salt pans from the North Norfolk coast salt marshes. A multiple regression model suggests that pan density is positively related to marsh height and negatively to distance from the marsh/sea edge. Since marsh height increases with time this model does not agree with the initial hypothesis. Further investigation of the regression model, however, indicates the dangers inherent in assigning causal mechanisms, for the independent variables are shown to be merely limiting conditions of pan density. Examination of these factors allows an alternative hypothesis for pan formation to be postulated: pans may be formed by the erosion of bare patches in the existing marsh vegetation, caused by rafts of vegetation debris brought in by high tides and deposited on the marsh surface.