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Diversity within and among living organisms is both a biological impera­ tive and a biological conundrum. Phenotypic and genotypic diversity is the critical currency ofecological interactions and the evolution of life. Thus, it is not unexpected to find vast phytochemical diversity among plants. However, among the most compelling questions which arise among those interested in ecological phytochemistry is the extent, nature, and reasons for the diversity of chemieals in plants. The idea that natural products (secondary metabolites) are accidents of metabolism and have no biological function is an old one which has resurfaced recently under a new term'redundancy.'Redundancy in the broader sense can be viewed as duplication of effort. The co-occurrence of several classes of phytochemieals in a given plant may be redundancy. Is there unnecessary duplication of chemical defense systems and ifso, why? What selective forces have produced this result? On the other hand, why does the same compound often have multiple functions? At a symposium of the Phytochemical Society of North America held in August 1995, in Sault Ste. Marie, Ontario, Canada, the topic'Phytochernical Redundancy in Ecological Interactions'was discussed. The chapters in this volume are based on that symposium. They both stimulate thought and provide some working hypotheses for future research. It is being increasingly recognized that functional diversity and multiplicity of function of natural products is the norm rather than the exception.

The present volume includes papers presented in the International Symposium on Adaptations to Terrestrial Environment, held in Halkidiki, Greece from September 26th to October 2nd, 1982, as well as some invited ones from well known scientists working in the same field. It seemed rather optimistic to deal just in the same volume with such a variety of organisms (micro­ organisms to higher plants) on the basis of the1r adaptive strategies for survival on land. It would appear as the entire ecology ought to be included. It was a challenge for us. We undertook this challenge hoping that the output would not be unsuccessful. The Editors allowed the authors of the accepted papers great leeway in terms of thoroughness of their contributions. The quality of the papers included is high while some of them had to be rewritten in order to include valuable comments developed during the Symposium discussions. We have tried to include many papers from Eastern Europe since generally, because of the language problem, they do not get widely known. The Editors wish to express their thankfulness to UNESCO for sponsoring the Symposium in the frame of Man and Biosphere Program; to all scientists who have contributed papers in this volume; and to Mrs. A. Karamanli-Vlahopoulou for her patient and skillful typing of part of the manuscript.

This book is the result of a symposium dedicated to the 25th anniversary of the Delta Institute for Hydrobiological Research in Yerseke, the Netherlands. The primary idea did not come from one of the scientists working in this Institute, but from the second editor. Long before the Institute celebrated itsjubilee on 20-23 October 1982, he expressed his feelings to the other editors, that the time had come for a second European symposium on the ecology of coastal vegetation. The first symposium on this theme was held in Norwich, 12-16 September 1977, being the first meeting of the European Ecological Symposium. He only So the working group Salt waited for a suitable opportunity. Well, the 25th anniversary was a good one. Marsh Ecosystems of the Delta Institute, in close collaboration with him, adopted Dr. Rozema's initiative and set about realizing his idea. An organising committee composed of the editors of this volume, planned the scope of the meeting.

July 8 -13, 1985, an international group of scientists met in Uppsala for a symposium on the subject'Theory and models in Vegetation science'. A volume of over 70 extended abstracts had already been published in time for the symposium (Leemans et at., 1985). That volume included contributions from nearly all of those who gave talks or presented posters at the symposium. The present volume represents the fully-refereed proceedings of the symposium and features articles by a majority of speakers, plus a handful by poster authors, and two that were sent independently to Vegetatio and seemed timely and relevant to the symposi­ um's theme. As organizers, we tried to bring together for the symposium people whose interests covered several key aspects of modern vegetation science: vegetation dynamics, on shorter or longer time scales; the analysis of community data, and of vegetation-environment relationships in both time and space; and the functional basis of vegetation in terms of the individual plants and plant populations that it comprises. We encouraged contributors to focus on theory and models - not necessarily mathematical models, but also conceptual models that might contribute to the development of theory and mathematical models.

Plants and Climate Change focuses on how climate affects or affected the biosphere and vice versa both in the present and past. The chapters describe how ecosystems from the Antarctic and Arctic and from other latitudes respond to global climate change. The papers highlight plant responses to atmospheric CO2 increase, to global warming and to increased ultraviolet-B radiation as a result of stratospheric ozone depletion. Depending on how and how well plant responses to increased temperature, atmospheric CO2 and ultraviolet-B have been preserved in the (sub)-fossil record, past climates and past atmospheric chemistry may be reconstructed. Pollen and tree-ring data reflect plant species composition and variation of temperature and precipitation over long or shorter time intervals. In addition to well preserved morphological and chemical plant properties, new analytical techniques such as stable isotopes are becoming increasingly important in this respect. The development and validation of such biotic climate and environment proxies build a bridge between biological and geological research. This highlights that plant-climate change research is becoming a multi- and transdisciplinary field of relevant research.