ACKNOWLEDGEMENTS

First I would like to thank Professor Toive Aartolahti for his excellent guidance during this research and for the patience which he showed when the work was prolonged. I also wish to extend my warmest thanks to Professor Matti Seppälä, Department of Geography, University of Helsinki, and Professor Emerita Leena Hämet-Ahti, Department of Botany, University of Helsinki, who have read through the manuscript very throughly and made numerous valuable comments and proposals for alterations, and to Docent Matti Tikkanen for his constructive criticism at earlier stages of this work. I am also grateful to the staff at the Department of Geography, University of Helsinki, for their support in the course of the research.

Krister Karttunen, Lic. Phil., and people at the Botanical Museum of Helsinki University, especially Prof. Teuvo Ahti and Lic. Phil. Heino Vänskä, have provided invaluable help in identifying the moss and lichen samples. The monthly averages of tide gauge records were obtained from the Finnish Institute of Marine Research (Merentutkimuslaitos), for which thanks are due. Ms. Leena Heiskanen, Ms. Pirkko Numminen and Ms. Kirsti Lehto prepared the figures for publication and Mr. Malcolm Hicks revised the English of the manuscript. Financial support was received from the Sohlberg Delegation of Societas Scientiarum Fennica. To all these persons and institutions I express my sincere thanks.

I am also grateful to my husband Pekka and my children Petri, Paula and Pipsa, who have spent so much time on field trips to the coastal dunes.