The first international congress for ecology took place in 1974 in The Hague, its central theme being "Unifying Concepts in Ecology". In the forefront of discussion at that time were questions of constancy, stability and resilience. Such questions have gone slightly out of fashion and the exceptionally precise and well thought-out concepts of that era are seldom applied nowadays. The present book introduces another unifying concept, the concept of the ecological cycle, or, more precisely, the mosaic-cycle concept of ecology. The following chapters have their origin in lectures which were held and discussed at a symposium of the Werner Reimers Stiftung in Bad Homburg. The purpose of the symposium was the preparation of this book. Our warmest thanks go to the Reimers Stiftung for their assistance and hospitality. We should also like to express our gratitude to all participants, to those who contributed to the discussion, and above all to those colleagues whose lectures provided, from a variety of aspects, a critical approach to the mosaic-cycle concept. Marburg, Winter 1990/91 HERMANN REMMERT Contents H. REMMERT The Mosaic-Cycle Concept of Ecosystems - An Overview ......... .

H. REMMERT Small populations are very often discussed, but there seems to be no general overview touching all the self-evident but norma,lly simply neglected problems connected with small populations. First, there are many very different types of organisms, and as every biologist should know, the problems of small populations are very different in different types of organisms. 1. In vascular plants the problems are different from the situation in birds and mammals; in marine benthic animals or in parasites such as tapeworms the problems are different again, and in seasonal planktonic animals or insects they are different from those in biotopes under constant conditions. In tapeworms or in vascular plants, an adult organism seems to be comparable to a population of mammals or birds because its offspring can be so diverse and plentiful. 2. There are small populations which explode and break down to a small population again, and then explode and break down again.

Michael Evenari's biography unfolds his exciting, manifold life: his love for botany, the confrontation with political events as a youngster and his thrilling experience of helping in the development of Israel. Evenari takes us on his exciting expeditions in the company of his beloved wife. He tells us of his meetings with many personalities and about his farm in the Negev. The discovery of long forgotten floodwater irrigated farm systems from the times of King Salomon and their reconstruction became a successful experiment which lead him to teach this approach of runoff agriculture in many parts of the world, initializing progress in the development of various arid areas. As a tribute to his successful scientific life, Evenari was awarded the Balzan Prize in 1988. In April 1989, Michael Evenari died at the age of 84.

A large number of comprehensive publications has been devoted to the Antarctic, to its plant and animal life. It is therefore relatively easy to familiarize oneself with the current state of Antarctic research. Nothing comparable is available for the Arctic. The heterogeneity and richness of the northern polar regions seem to have discouraged any attempt at a synthethic approach. This book has evolved from an attempt to summarize the results of 15 years of ecological and physiological research work in the Arctic - mostly on Spitsbergen. The necessity of comparing our results and the ecological conditions of Spitsbergen with other arctic regions grew into a full-sized book on arctic animal ecology. It is not meant as an exhaustive survey ofthe relevant literature. Instead I have tried to show how closely the various fields of research are interwoven, how many questions can be solved if only notice is taken of fellow scientists and their results, and how much arctic animals have in common. This book would not have been possible without the helpfulness of many colleagues. Above all I should like to mention Professor Ronning and Professor Solem of Trondheim University (Norway), Professor Arnthor Gardasson of Reykjavik University (Iceland), Dr. NettIeship, Dr. Oliver and Dr. Ryder of Canada and Professor West of Fairbanks University (Alaska, USA).

The wealth of the natural sciences no longer consists in the abundance of facts, but in the way they are linked together. ALEXANDER VON HUMBOLDT There is no dearth of books on ecology. Why write yet another? Each person is different, and each views the problems in a different way. Each emphasizes different aspects and describes them in a different style. When I was a student I often found certain books more helpful than others, and I still think it is useful to have a variety of presentations from which to choose. This variety also allows the student to appreciate the diversity within the field of ecology. I have devoted considerable effort to making this book readable. Throughout I have refrained from using specialized terminology - thus also avoiding the problem that many terms are used differently in the various areas of ecology. Straightforward English is quite sufficient to describe complicated situations. Furthermore, precisely defined terms are usually associated with detailed quantitative descriptions, whereas we are concerned with a general understanding of the dynamics of ecology. For similar reasons I have tried to rely as little as possible on mathematical discussions. All too often, in recent years, people have overlooked the fact that mathematics - like language - can give only a description, albeit an especially precise one.

In diesem Band der Speziellen A-kologie stellt Hermann Remmert seine A1/4ber Jahrzehnte auf Reisen durch alle Kontinente zusammengetragenen und A1/4berprA1/4ften Ideen und Hypothesen zu terrestrischen A-kosystemen vor. Im Vordergrund stehen dabei die Wechselbeziehungen zwischen Pflanzen und Tieren unter dem EinfluA von Klima und Geologie in verschiedenen A-kosystemen wie Regenwald, Nadel- und LaubwAldern, Steppen, Tundren, Auen und Kulturlandschaften. Anhand vieler Beispiele rekonstruiert Remmert, wie diese LebensrAume vor unserer Zivilisation strukturiert waren. Mit dieser anschaulichen Darstellung der terrestrischen A-kologie ist dem bekannten Marburger A-kologen sein letztes, groAartiges Werk gelungen.

Professor Hermann Remmert, fuhrender Okologie-Experte und Autor zahlreicher wissenschaftlicher Publikationen, gibt hier eine gut lesbare und auch fur den Laien verstandliche Einfuhrung in die viel-diskutierte Thematik: Naturschutz. Die Gliederung des Buches folgt den Fragestellungen: - Was ist Naturschutz? - Warum brauchen wir ihn, fur wen und fur was? - Wer hat zu schutzen, und was? - Wie hat das zu geschehen (Artenschutz, Biotopschutz, Schutz der okologischen Prozesse)? - Wo muss der Naturschutz einsetzen? - Wie gross mussen Naturschutzgebiete sein? - Was "kosten" Naturschutzgebiete? - Wie werden die Konzepte des Naturschutzes in der Lehre behandelt, weitergegeben und letztlich realisiert? Diese Thematik wird erganzt durch die Erorterung des rechtlichen Rahmens, innerhalb dessen Naturschutz verankert werden kann und sollte. In einer lebendigen Sprache und anhand von plastischen Beispielen stellt H. Remmert die heutige Situation des Naturschutzes speziell fur diejenigen dar, die zunachst dem Naturschutz beruflich und gedanklich fernstehen, aber im Zuge unserer Umweltkrise nun direkt - und sei es nur im Urlaub - mit (mangelndem) Naturschutz konfrontiert werden.