Print PageBiological invasions may alter diversity of communities and the subsequent successional processes of that community as well. Sand accreting dunes on the US West Coast provide a unique opportunity for studying the effects of plant invasions through time. Because dunes grow outward towards the ocean as they accumulate sand, a transect across the dune represents a chronosequence of succession. West Coast dunes have been dominated by the invasive European grass Ammophila arenaria since the 1800s, but a newer invasion of its Eastern US congener, A. breviligulata, has begun displacing the A. arenaria along the coast. Using transect data of plant communities and geomorphology from the 1980s and 2000s, we study how the secondary invasion of A. breviligulata has altered the patterns of succession across the chronosequence and along the coast by asking 1) how cover of Ammophila has altered native plant diversity through time; 2) how displacement of A. arenaria by A. breviligulata has contributed to community changes; and 3) how the two Ammophila species differ in their effects on endemic dune species’ colonization through time.
Results/Conclusions
We find that switching of Ammophila species and increased Ammophila cover, has had a significant effect on plant community composition. Species accumulation and diversity through dune succession has decreased over time. Finally, accumulation of endemic dune species has slowed with the increased presence of A. breviligulata. Our results illustrate how plant invasions may alter the trajectory of community succession. Moreover, we find that already invaded habitats are still susceptible to community alterations from new invaders, which may further complicate the successional processes.
