Die 5. "Verhandlungen der Gesellschaft fur Okologie" enthalten die Vortrage der vom 22. bis 24. September 197 5 in Wien durchgefuhrten J ahrestagung. Schwer punktsmassig behandeln die Referate alpine und arktische Okosysteme, die okologi schen und genetischen Voraussetzungen fur das Leben in Trockengebieten sowie limnische Okosysteme. Durch die Berucksichtigung der diese Systeme tangierenden IBP- und MAB-Forschungsprogramme liefern sie zugleich auch aktuelle Informa tionen uber laufende Forschungsprojekte unserer Osterreichischen und schweizer Kollegen. Struktudle und energetische Untersuchungen uber einzelne Okosysteme, Biozo nosen und Populationen stehen dabei im Vordergrund. Die vorgelegten Arbeiten verdeutlichen, dass jedes lebendige System uber die Kenntnis seiner Struktur, Funk tion und Geschichte Informationen zu einem tieferen Verstandnis des von ihm belebten Raumes liefert. Sie zeigen, dass letztlich jeder Suche nach "Belastungsindi katoren" und "okologischen Kriterien" die Frage nach dem Informationsgehalt von Organismen und lebenden Systemen sowie deren Reaktionen auf endo- und exogene Faktoren zugrunde liegt. Sowohl aus Veranderungen der Areal- und Okosysteme, als auch aus Wandlungen von Biozonosen und deren Reaktionen wurden Ruckschlusse auf die diese Veranderungen auslosenden Faktoren gezogen. Populationen und Bio zonosen reagieren naturgemass nach eigenen Regeln, konnen jedoch nur existieren, wenn sie bestandig auch Informationen uber andere Komponenten aus ihrem Ver breitungsgebiet speichern und verarbeiten. Diese adaptiven Fahigkeiten der unter suchten Arten und Systeme sind jedoch noch weitgehend unbearbeitet. Hier klafft eine echte Lucke, die den Transfer okologischer Daten z. B. in di. c Landesplanung erschwert. Die Qualitat jeder Planung hangt weitgehend von den eingesetzten okologischen, sozialen und wirtschaftlichen Erhebungsdaten ab."

As in the terrestrial environment, most data collection from freshwater habitats to date falls into the survey, surveillance or research categories. The critical difference between these exercises and a monitoring project is that a monitoring project will clearly identify when we need to make a management response. A Model for Conservation Management and Monitoring Monitoring (as defined by Hellawell) is essentially a tool of practical conservation management, and Fig. 1.1 shows a simple, but effective, model for nature conser- tion management and monitoring. The need for clear decision-making is implicit in this model. First we must decide what would represent a favourable state for the key habitat or species, and then we must decide when to intervene if the state is (or becomes) unfavourable. A third, often overlooked, but equally important, decision concerns when we would consider the habitat or species to have recovered; this is unlikely to be the same point that we became concerned about it. This decision not only has resource imp- cations, it can also have major implications for other habitats and species (prey species are an obvious example). All of these decisions are essential to the devel- ment of an efficient and effective monitoring project.

O. L. LANGE, P. S. NOBEL, C. B. OSMOND, and H. ZIEGLER In the original series of the Encyclopedia of Plant Physiology, plant water relations and photosynthesis were treated separately, and the connection between phenomena was only considered in special chapters. O. STOCKER edited Vol ume III, Pjlanze und Wasser/Water Relations of Plants in 1956, and 4 years later, Volume V, Parts I and 2, Die COrAssimilation/The Assimilation of Carbon Dioxide appeared, edited by A. PIRSON. Until recently, there has also been a tendency to cover these aspects of plant physiology separately in most text books. Without doubt, this separation is justifiable. If one is specifically inter ested, for example in photosynthetic electron transport, in details of photophos phorylation, or in carbon metabolism in the Calvin cycle, it is not necessary to ask how these processes relate to the water relations of the plant. Accordingly, this separate coverage has been maintained in the New Series of the Encyclopedia of Plant Physiology. The two volumes devoted exclusively to photosynthesis are Volume 5, Photosynthesis I, edited by A. TREBST and M. AVRON, and Volume 6, Photosynthesis II, edited by M. GIBBS and E. LATZKO. When consider ing carbon assimilation and plant water relations from an ecological point of view, however, we have to recognize that this separation is arbitrary.

Ecosystems change on a multitude of spatial and temporal scales. While analyses of ecosystem dynamics in short timespans have received much attention, the impacts of changes in the long term have, to a great extent, been neglected, provoking a lack of information and methodological know-how in this area. This book fills this gap by focusing on studies dealing with the investigation of complex, long-term ecological processes with regard to global change, the development of early warning systems, and the acquisition of a scientific basis for strategic conservation management and the sustainable use of ecosystems. Within this book, theoretical ecological questions of long-term processes, as well as an international dimension of long-term monitoring, observations and research are brought together. The outcome is an overview on different aspects of long-term ecological research. Aquatic, as well as terrestrial ecosystems are represented.