The effect of sea-water submergence on rhizome bud viability of the introducedAmmophila arenaria and the nativeLeymus mollis in California

Ammophila arenaria, an invasive European beach grass, dominates most United States Pacific coast beaches north of San Francisco Bay, and it appears to severely reduce opportunities for regeneration of native plant species, including American beach grass,Leymus mollis. The knowledge of how longAmmophila rhizomes can survive in sea-water is important for long-tern management strategies, which must consider the probability of reinvasion of areas whereAmmophila has been eradicated. The bud viability of bothAmmophila arenaria andLeymus mollis remained high following submergence in sea-water for 7 days, andLeymus bud viability was still high after 13 days submergence. In fact,Leymus bud viability appears to be enhanced slightly by submergence for 7 days in sea-water. SinceAmmophila rhizomes retain a mean bud viability of >50% following submergence for 7 days, there is clearly the potential for long distance dispersal to other beaches. Even after 13 days of submergence,Ammophila rhizomes still had a mean bud viability of 8.5%. Assuming near-shore current speeds of 5–45 cm/sec, viableAmmophila rhizomes can be transported up to 505 km in 13 days.