Comparative Growth Responses And Population Ecology Of European And American Beachgrasses (ammophila Spp) In Relation To Sand Accretion And Salinity

Marram (European beachgrass; Ammophila arenaria (L.) Link) and American beachgrass (A. breviligulata Fern.) are coastal dune-colonizing grasses which were formerly treated as a single species. They were distinguished taxonomically on the basis of traits with no obvious ecological importance. Ammophila species have been regarded as ecologically equivalent, and the species distinction itself has been questioned. In this thesis, critical aspects of growth and colonizing ability in relation to sand accretion and salinity were compared in these putative ecological equivalents .;Populations from Wales U.K. and Maine U.S.A. were grown in artificial dune plots constructed near London, Ontario. Sand accretion up to 50 cm yr{dollar}\sp{lcub}-1{rcub}{dollar} caused increased shoot vigor and clonal growth rate in both Ammophila species, but species differed in the pattern and magnitude of response. In A. breviligulata, accretion stimulated leaf blade width, area, shoot size, and tillering. In A. arenaria, size of leaves and shoots were relatively stable in response to accretion, but 50 cm accretion stimulated tillering in this species more than in A. breviligulata. Rates of leaf production and extension were strongly stimulated by sand accretion in both species. A. breviligulata generally developed very large, extensive rhizome systems. In contrast, A. arenaria developed dense, compact tussocks and few, short rhizomes with less potential for clonal spread. These results correspond with field data. In A. breviligulata, there was a strong negative correlation between flowering and rhizome growth, and the response of flowering to sand accretion was non-linear. A. arenaria flowered little or not at all in the experiment.;Both Ammophila species possess moderate salinity resistance in terms of survivorship and growth response to substrate salinity, and may be classified as salt-resistant glycophytes. In these respects, A. breviligulata is more salt-resistant than A. arenaria. In both species, however, 104 hr immersion in cold seawater failed to reduce viability of dormant vegetative propagules, and repeated short-term inundation of plants by seawater did not kill established seedlings. Clonal integration allowed A. breviligulata ramets to grow vigorously at high salinity levels which were either lethal or highly inhibitory to isolated ramets.;The results from the experiments on these populations and from the literature imply that there are important ecological differences between Ammophila spp. in traits relating to colonization, growth, and clonal spread in beach and dune environments