Distribution and Effects of Ammophila breviligulata Fern. (American beachgrass) on the Foredunes of the Washington Coast
Keywords:Ammophila arenaria, dune morphology, introduced species, coastal plant communities
Since the turn of the century, the foredunes on the west coast of North America have become dominated by Ammophila breviligulata due to extensive sand stabilization plantings. Ammophila breviligulata was planted less extensively than A. arenaria. However, A. breviligulata has come to singularly dominate the foredunes of Washington in the southern half of the state and its range extends north along the entire coast. By comparing the distribution of current A. breviligulata and A. arenaria communities with historic shorelines, it was found that this invasion occurred in the last 50 years and the locus of the invasion was determined. A comparison of foredunes dominated by A. breviligulata with existing A. arenaria foredunes shows that this colonization has had minimal impact on the species diversity of the dunes but it has resulted in a lowering of the mean height of the foredune crests.