This book is dedicated to international cooperation, understanding and peace. It is the end result of several years of cooperative work between scientists of three countries: the United States, Germany, and Portugal. The work presented, however, draws from a much broader base, hopefully achieving the objective of NATO Advanced Research Workshops, which have been established to allow and stimulate the exchange of new ideas and the synthesis of information by scientists of NATO countries. The tasks of the workshop were several; to review established methodologies that have provided insight into ecosystem function and adaptations of plants in mediterranean climate zones; to examine new methodologies that have recently been applied in ecological studies and have provided new types of information; to summarize recent studies in mediterranean regions of plant water relations, photosynthesis and production, mineral nutrition, plant growth and development, and response to fire; to stimulate in particular an exchange of information among scientists of European Mediterranean countries; and to discuss means by which all of these objectives might be even more effectively achieved in the future through cooperative international research efforts. This variety of themes is clearly evident in the layout of the book. Held in Sesimbra, Portugal in October of 1985, the workshop took place in a ..

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."

During the last decade, forest decline has become increasingly apparent. The decline in forest health was often reported to be associated with air pollution. The present study on Norway spruce stands in the Fichtelgebirge analyses various processes interacting within forest ecosystems. It covers transport and deposition of air pollutants, the direct effects of pollutants on above-ground plant parts, the responses of soil to acid rain, and the changing nutrient availability, and the accompanying effects on plant metabolism and growth. The role of fungi, microorganisms and soil animals in the decline of these stands is also assessed. The volume is concluded with a synthesis evaluation of the influence of different factors, and their interactions on forest decline.

In arid lands, where vegetation is sparse or absent, the open ground is not bare but generally covered by a community of small, highly specialized organisms. Cyanobacteria, algae, microfungi, lichens, and bryophytes aggregate soil particles to form a coherent skin - the biological soil crust. It stabilizes and protects the soil surface from erosion by wind and water, influences water runoff and infiltration, and contributes nitrogen and carbon to desert soils. Soil surface disturbance, such as heavy livestock grazing, human trampling or off-road vehicles, breaks up the fragile soil crust, thus compromising its stability, structure, and productivity. This book is the first synthesis of the biology of soil crusts and their importance as an ecosystem component. Composition and functioning of different soil-crust types are discussed, and case studies are used to show the impact of crusts on landscape hydrology, soil stability, nutrient cycles, and land management.