The vegetation of the sand dunes on Long Beach, Vancouver Island, was studied on 116 sample plots. The purpose of this study was to describe the floristic and edaphic characteristics of the plant associations, to determine the major environmental factors controlling the distribution of the plant communities and to study the successional trends of the vegetation. The vegetation was described using the analytical and synthetical methods of the Zurich-Montpellier school of phyto-sociology. This thesis describes seven plant associations and four variants. The vegetation units are as follow: A. Foreshore habitats 1. Cakiletum edentulae B. Blowout habitats 2. Poetum macranthae a. poosum macranthae , b. abroniosum latifoliae 3. Arctostaphyleto-Rhacomitrietum canescentis C. Habitats of the mobile dune ridge 4. Elymetum vancouverensis a. ammophilosum arenariae b. elymosum vancouverensis D. Habitats of the dune slack and stable dune ridge 5. Aireto-Ceratodontetum purpurei 6. Arctostaphyleto-Eurhynchietum oregani 7. Hetergenous communities i n moist dune slack habitats E. The dune forest habitat 8. Piceeto-Gaultherieto-Maianthemetum dilatati Important environmental factors which control the distribution of these associations are the level of winter and storm tides, wind, the amount of sand burial and blowout that occurs in the habitat and the amount of available soil water. The first stages of succession begins in the unstable habitats of the Elymetum vancouverensis and Poetum macranthae. With stabilization of the habitat, these associations are succeeded by the Aireto-Ceratodontetum purpurei and the Arctostaphyletum-Eurhynchietum oregani in exposed habitats and the Arctostaphyleto-Rhacomitrietum canescentis in habitats well protected from wind. All vegetation eventually reaches the climax Piceeto-Gaultherieto-Maianthemetum dilatati. / Science, Faculty of / Botany, Department of / Graduate