A multivariate approach to plant community distribution in the coastal dune zonation of NW Denmark

A near-natural coastal dune system in NW Jutland, Denmark was investigated. The area contains a gradient in natural soil mobility with the highest values in dynamic white dunes dominated by Ammophila arenaria, and low mobility in fixed decalcified dune heath with Empetrum nigrum and Calluna vulgaris. A total of 267 plots was investigated and presence of mosses and rooted vascular plants recorded. Cluster analysis identified five communities: white dune, grey dune, outer dune heath, inner dune heath and humid dune heath. These communities were ordered along two main axes in a Detrended Correspondence Analysis (DCA). The relationship between DCA axes and several environmental variables, including soil characteristics and Ellenberg indicator values, were investigated by correlation. Two major complex gradients underlying compositional variation were identified; one short coenocline with an underlying steep gradient in habitat maturity, soil stability and nutrient-limited productivity, and one longer gradient in water-limited productivity and peat accumulation only applying to the older successional stages. Distance from the coast was an important correlate of several of the measured variables. Microclimatic indices, i.e. heat index and wind index, had limited value as descriptors of community patterns as they were not correlated with the DCA axes or with other environmental variables. However, within communities the microclimatic indices correlated with several explanatory variables