Several environmental factors vary with distance from the shoreline on coastal dunes. For instance, salinity, salt spray, and sand movement decrease but nutrient and water availability increase from the foredune to the stabilized dunes. Plants colonizing the upper beach and the foredune are thus exposed to more severe abiotic stresses than those on the stabilized dunes. Although community composition changes progressively from the upper beach to the stabilized dunes, some species persist through the sequence. For example, on the coastal dunes of subarctic Quebec, Leymus mollis (Trin.) Hara (Poaceae), a perennial grass that colonizes the upper beach and the foredune, persists onto older stabilized dunes. Under controlled conditions, the response of L. mollis ramets from different habitats along the dune sequence to various saline conditions was examined. It was expected that ramets from the upper beach and the foredune, where substrate salinity is typically higher, salt spray more important, and saltwater intrusion more frequent, to better support salinity stress. Ramets from the upper beach and the foredune had a higher relative growth rate (RGR) but were, in fact, less tolerant to salt stress than those from the stabilized dune. Because sand accumulation is higher on the upper beach and the foredune, a higher RGR may be favored there to the detriment of a higher sensitivity to salt stress. The salt tolerance of stabilized dune ramets may be the expression of a more generalized stress-tolerance strategy as suggested by low RGR and high leaf nutrient concentration.
