It has been known for a long time that the majority of plant viruses contain RNA and in the past decade and a half it has been realized that many have genomes consisting of three molecules of single-stranded RNA with positive polarity. Among these are viruses belonging to four groups recognized by the International Committee for Virus Taxonomy: the Bromovirus and Cucumovirus groups whose genomes are encapsi dated in small icosahedral particles or the Ilarvirus and alfalfa mosaic virus groups with spheroidal or bacilliform particles. In addition to their tripartite genomes, these viruses share a number of other properties and it has been proposed that they should perhaps be grouped in a single virus family for which the name Tricornaviridae has been suggested, the tri indicating the tripartite nature of the genome, the co emphasizing the cooperation of the three genome parts required to initiate infection, and the rna indicating that the genome is composed of RNA. Viruses of this "family" are less uniform in their biological proper ties. A number of them are widespread, causing very destructive plant diseases. Viruses such as those of cucumber mosaic and alfalfa mosaic have very extensive host ranges and are responsible for serious crop losses in many parts of the world. Others such as prunus necrotic ringspot or prune dwarf viruses are more restricted in their host ranges but never theless infect important perennial hosts such as stone fruits and reduce productivity considerably."

With its 250-year history, Sustainable Forest Management (SFM) is now viewed as a model for managing forests worldwide. Yet despite the frequent use of the term there remain many questions concerning its meanings, criteria as well as its practical application.

This book explores the current potential of SFM within the context of the rapid changes occurring in our natural and social environment, and examines the broad range issues climate change, finance, governance, policy, certification, reduced-impact logging, non-timber products and services and stakeholder participation in land-use decisions within the context of forest use, functions and conservation.

With contributions from high-level representatives from the World Bank, FAO, IUCN and UNEP, as well as from leading academics and including case studies from Europe and the tropics this timely synthesis will provide a valuable reference for advanced students and researchers interested in forest and natural resource management, participatory and extension research, forest ecology and ecosystem services, functions and values, as well as for those involved in forest policy at local, regional and international levels.

'Every so often, a discipline should take stock where we are and where we are going. This book is doing that in a very timely manner. As we gain an appreciation of the magnitude and implications of future changes, the authors present views and ideas on a wide range of topics related to sustainable forest management. They provide a much needed overview of challenges in the face of climate and other aspects of global change. The book incorporates recent advances in a variety of fields and provides suggestions for solutions to important management problems that range from theoretical approaches to practical applications.' Klaus J. Puettmann, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, USA."

This volume presents the papers given at the meeting "Estuarine Management and Quality Assessment" held at Trinity College, Dublin in September 1983. The meeting was organised by the Environmental Sci ences Unit, TCD and the Estuarine and Brackish-Water Sciences Associ ation and was attended by delegates from the United Kingdom, Ireland, France, Holland and Portugal. The theme for the meeting was deliberately chosen in an attempt to bring together the various disciplines and interests in the field of estuarine quality, and the extent to which this objective was met may be judged from the diversity of the contributions. The meeting was arranged under three sub-headings which could be roughly summar ised thu- a) Modelling - as representative of the engineering hydrodynamicist approach. b) Impact - as representative of the biologist-type approach. c) Management - attempting to reconcile the different approaches to, and demands on, the estuary. In fact, since most contributions overlapped into the other two categories, the order in this volume has been changed somewhat from the meeting, and we feel that this book may be fairly presented as one unit. Contributions for which it was not possible to give full transcripts have been included, for completeness, as abstracts. In each session, an invited speaker summarised the state of the art, and the other speakers followed up by describing some new approach to or refinement of the problem."

In evolutionary time scales natural disturbances have affected the vegetation on Earth. During the Quaternary the forest biomes of the tropics were subjected to manifold disturbances. Climate changes and climate oscillations were associated with changing precipitation and drought regimes, flooding, siltation, landslides, etc. The prehistorical forest was also influenced by the effects of large wildlife populations. Large-scale catastrophies in the forest biomes were mainly caused by abiotic environmental alterations, the small-scale disturbances were and still are related to both biotic and abiotic processes. Both the large-and the small-scale disturbances have played a significant role in shaping distribution, dynamics, structure and composition of the paleoforest. After the expansion of hominids and early humans, and later, by modern humans, the anthropogenic influences on the tropical forest began to overlap natural disturbances. Today's anthropogenic impacts on the tropical forests differ qualitatively and quanitatively from the natural disturbances. The speed of tropical deforestation and savannization is dramatically increasing. The physical and chemical impacts of forest conversion and biomass burning add to other anthropogenic influences on the atmosphere and climate. The expected anthropogenic climate change will also have considerable impacts on the tropical flora and fauna. The book on "Tropical Forests in Transition" synthesizes information on changing environmental conditions and human impacts on the tropical forest by looking back to the paleoecology, analyzing the impact of modern human populations and modeling the future of the tropical forest in a changing environment. The aim of the book is to strengthen multidisciplinary thinking in disturbance ecology.

It is appropriate at this time to reflect on two decades of research in biological control of weeds with fungal plant pathogens. Some remarkable events have occurred in the last 20 years that represent a flurry of activity far beyond what could reasonably have been predicted. In 1969 a special topics review article by C. L. Wilson was published in Annual Reviews of Phytopathology that examined the literature and the potential for biological control of weeds with plant pathogens. In that same year, experiments were conducted in Arkansas that determined whether a fungal plant pathogen could reduce the infestation of a single weed species in rice fields. In Florida a project was under way to determine the potential use of a soil-borne plant pathogen as a means for controlling a single weed species in citrus groves. Work in Australia was published that described experiments that sought to determine whether a pathogen could safely and deliberately be imported and released into a country to control a weed of agricultural importance. All three projects were successful in the sense that Puccinia chondrillina was released into Australia to control rush skeleton weed and was released later into the United States as well, and that Colletotrichum gloeosporioides f.sp. aeschynomene and Phytophthora palmivora were later both marketed for the specific purpose of controlling specific weed species.

It would have been very easy to expand on all the sections of the first edition but I decided to try to retain the relatively short, introductory nature of the book. Some new material has been added, particularly where it has been possible to update data, and there has been some change of emphasis in places, in order to reflect changing world conditions. The book retains its original purpose, however, of introducing systems thinking as applied to agriculture. I am grateful to Angela Hoxey for help in preparing this edition, especially in relation to the preparation of tables and figures. C. R. W. SPEDDING v Preface to the First Edition The agricultural systems of the world represent a very large subject. Their study involves a great deal of fairly detailed knowledge, as well as a grasp of the structures and functions of the systems themselves. This book has been written as an introduction to such a study and it concentrates on an overall view, rather than on the detail, partly because of the need to relate the latter to some larger picture in order to appreciate the relevance and significance of the detail. This problem-of seeing the relevance of component studies and the significance of physical, biological and economic detail, and indeed principles-is encountered by many agricultural students right at the beginning of their university careers.

Respiration is a large and important component of the carbon economy of crops. There are already several good books dealing with the biochemistry and physiol ogy of plant respiration, but there are none I know of that are devoted to the rela tionship between respiration and crop productivity, although this relationship is more and more frequently being studied with both experiment and simulation. Crop physiology books do cover respiration, of course, but the treatment is limited. The purpose of the present book is to fill this void in the literature. The approach taken here is to use the popular two-component functional model whereby respiration is divided between growth and maintenance components. Mter thoroughly reviewing the literature, I came to the conclusion that at present this is the most useful means of considering respiration as a quantitative compo nent of a crop's carbon economy. This functional distinction is used as the frame work for describing respiration and assessing its role in crop productivity. Discussions and critiques of the biochemistry and physiology of respiration serve primarily as a means of more fully understanding and describing the functional approach to studying crop respiration. It is assumed that the reader of this book is familiar with the fundamentals of plant physiology and biochemistry. The research worker in crop physiology should find this an up-to-date summary of crop respiration and the functional model of respiration. This book is not, however, a simple review of existing data."

This volume is the last contribution of a series of With the present book, a further gap concern studies concerned with the plant material of one ing leaf morphology and leaf venation, as well and the same area of Venezuelan Guiana. The as some structural peculiarities of physiological importance, is closed so that an exhaustive survey studies originated through a collaboration with the forest engineer Dr. B. Rollet, the FAO expert in of bark and leaf morphology and anatomy as well forest inventory who collected the material of tree as of fruit and seed structure of the plants of a barks, leaves, fruits and seeds in Venezuelan certain well-known area is herewith given. Not Guiana around the "Rio Grande," "EI Paraiso," only were hundreds of species studied, but and "EI Dorado" camps. In the first place, tree structural characteristics were related to "forest barks of about 280 species of dicotyledons stratification," i. e. to the different micro climatic belonging to 48 families were studied (family by conditions in the forest, as the height of the trees family) by Roth in separate publications which and shrubs studied was known. It is of common mainly appeared in Acta Botanica Venezuelica knowledge that in the lower forest layers, light is a and in Acta Biol6gica Venezuelica (see the bibli limiting factor, while humidity is sufficiently avail ography in Roth 1981)."

In this volume experts present the latest status of mathematical and statistical methods in use for the analysis and modeling of plant disease epidemics. Topics treated are - methods in multivariate analyses, ordination and classification, - modeling of temporal and spatial aspects of air- and soilborne diseases, - methods to analyse and describe competition among subpopulations, e.g. pathogen races and - their interaction with resistance genes of host plants - assemblage and use of models - mathematical simulation of epidemics. New chapters on the modeling of the spreading of diseases in air and in soil are included in this second edition.

This book is a collection of papers presented at a NATO Advanced Research Workshop on "Biology and Molecular Biology of Plant-Pathogen Interactions" which was held at Dillington College, Ilminster, UK, 1-6 September 1985. It had been preceded by Advanced Study Institutes at Porte Conte, Sardinia in 1975 and at Cape Sounion, Greece in 1981. In recent years, methods for the manipulation and transfer of genes have revolutionized our understanding of gene structure and function. It was thus opportune to bring together scientists from distinct disciplines, e. g. plant pathology, cytology, biochemistry and molecular biology to discuss our present understanding of cellular interactions between plants. We also explored how the potential offered by the newer molecular technologies could best be realized. It soon became evident at the Workshop, and is a repeated theme of this publication, that future research will need concentrated multi disciplinary programmes. Many of the new approaches will be valuable. For example, immunocytochemistry does, for the first time, allow molecules to be located precisely within infected tissues. Equally, the methods of DNA isolation and gene transformation will facilitate the isolation and characterization of genes associated with pathogenesis and specificity. The description at the Workshop of immunocytochemical protocols and of transformation systems for pathogenic fungi have already stimulated an upsurge in research on plant-pathogen relationships. The papers discuss many interactions between plants and fungal and bacterial pathogens, but also provide a comparison with mycorrhizal and symbiotic relationships, and those involving mycoparasites."

Methane plays many important roles in the earth's environment. It is a potent "greenhouse gas" that warms the earth; controls the oxidizing capacity of the atmosphere (OH) indirectly affecting the cycles and abundances of many atmospheric trace gases; provides water vapor to the stratosphere; scavenges chlorine atoms from the stratosphere, terminating the catalytic ozone destruction by chlorine atoms, including the chlorine released from the man-made chlorofluorocarbons; produces ozone, CO, and CO2 in the troposphere; and it is an index of life on earth and so is present in greater quantities during warm interglacial epochs and dwindles to low levels during the cold of ice ages. By all measures, methane is the second only to CO2 in causing future global warming. The book presents a comprehensive account of the current understanding of atmospheric methane, and it is an end point for summarizing more than a decade of intensive research on the global sources, sinks, concentrations, and environmental role of methane.

The XXX Congress of the International Union of Physiological Sciences took place in Vancouver, Canada, in July 1986; and this Volume contains a selection of the Review Lectures which formed part of the Congress programme. They cover most of the areas of contemporary physiology and were presented by distinguished scientists from many parts of the world. An innovation at this Congress was the inclusion in the programme of a number of lectures devoted to historical subjects. These lectures attracted large audiences at the meetings, and three of them also appear in this book. Finally, the Plenary Lectures which formed part of the opening and closing ceremonies and which deal with some aspects of Canadian physiological history, find a place here as well. The Editors are grateful to all of the authors who provided the manuscripts which go to make up this book, and to John Donald for his invaluable assistance in the preparation of the final text; as well of course to all of the contributors whose participation made the Congress the success which it was. It is hoped that this Volume will provide a useful memento of the event.

The oil crisis during the 1970s turned interest towards the utilization of renewable resources and towards lignocellulosics in particular. The 1970s were also the cradle period of biotechnology, and the years when biotechnical utilization of lignocellulosic waste from agriculture and forestry gained priori ty. This was a logical conclusion since one of nature's most important biologi cal reactions is the conversion of wood and other lignocellulosic materials to carbon dioxide, water and humic substances. However, while biotechnology in other areas like medicine and pharmacology concerned production of expen sive products on a small scale, biotechnical utilization and conversion of ligno cellulosics meant production of inexpensive products on a large scale. Biotechnical utilization of lignocellulosic materials is therefore a very difficult task, and the commercial utilization of this technology has not progressed as rapidly as one would have desired. One reason for this was the lack of basic knowledge of enzyme mechanisms involved in the degradation and conversion of wood, other lignocellulosics and their individual components. There are also risks associated with initiating a technical development before a stable platform of knowledge is available. Several of the projects started with en thusiasm have therefore suffered some loss of interest. Also contributing to this failing interest is the fact that the oil crisis at the time was not a real one. At present, nobody predicts a rapid exhaustion of the oil resources and fuel production from lignocellulosics is no longer a high priority."

The electric field of the heart was described diagrammatically for the first time by A. Waller in 1888. However, it was not until a little more than ten years ago that with the development of micro electronic techniques, it became accessible to biophysical modeling, to exact physiological measurements, and to application in advanced clinical diagnosis. These possibilities opened the way to the treatment of questions which are called the direct and the inverse solution of the cardioelectric problem. Several groups of investigators are now working to achieve a complete biophysical and physiological description of the generation of the cardiac electric field. This work could well form the basis for a new method of diagnostic measurements, with applications even in clinical cardiology, delivering important information by a non invasive investigation of the patient. Several conferences have stimulated international exchange of the results of research on the cardiac electric field. Among others, the satellite symposium of the XXV International Congress of Physio logical Sciences on the electric field of the heart, in Brussels, August 2-3, 1971, and the Conference on Measuring and Modeling of the cardiac electric field, in Smolenice near Bratislava, June 14- 17, 1976, may be considered predecessors of the Dresden symposium the proceedings of which are presented in this volume."

Temperate forests cover large areas of Europe and perform a number of important functions such as the regulation of energy and matter, production of wood and other resources, and conservation of biodiversity and habitats; they also have special signi?cance in social and cultural contexts. Initiated in 1960s, the ?rst International Biological Program (IBP) focused on ''the biological basis of productivity and human welfare. '' As the German contribution to the IBP, ecosystem research has been carried out since 1966 in the Solling area (Ellenberg H., Ecological Studies 2, 1971), an upland region in Northwest Germany. This study provided clear evidence that the stability of forest ecosystems was threatened by the high inputs of at- spheric pollutants. This promoted many interdisciplinary research programs which were coordinated by Prof. Dr. Bernhard Ulrich and the Forest Ecosystems Research Center of the University of Go]ttingen. This involved, in addition to the Solling site, the establishment of two other sites for long-term monitoring of ecosystem pro- ] cesses. The two contrasting sites were established in 1980 at Gottinger Wald on base-rich calcareous soil and in 1989 at Zierenberg on volcanic soil. These projects were funded initially by the Federal Ministry of Research and Technology (BMBF) as interdisciplinary projects under the titles: ''Conditions of Stability of Forest Ecosystems'' (1989-1993), and ''Dynamics of Forest Ecos- tems'' (1993-1998). The primary goal of these studies was to quantify the ecolo- cal condition of forests in a changing environment and element ?uxes."

Band 8 ist den Neuentwicklungen auf dem Gebiet der Herbizide gewidmet. Die Bedeutung der Herbizide ist von 1976 bis 1980 erneut gestiegen, und weltweit betragt der Herbizid-Verkauf wertmassig soviel, wie der Verkaufswert der Insekti- zide und Fungizide zusammen! Langsam bedienen sich auch, bei intensiverem Anbau von Nahrungsmitteln und Nutzkulturen, "unterentwickelte" Lander aller Arten von Pestiziden und Herbiziden, und so ist mit einer weiteren Steigerung der Herbizid-Anwendung zu rechnen. Von 1976 bis 1980 wurden viele neue Versuchsprodukte, aber vergleichsweise wenig neuartige Handelsprodukte bekannt, denn der Herbizid-Standard ist schon sehr hoch, sodass es immer schwieriger wird, Herbizide mit wesentlichen Vorteilen zu finden, zu entwickeln und zum Verkauf zu bringen. Die mengenmassig hohe Produktion wichtiger Herbizide macht es zudem schwierig, preiswertere neue Produkte herzustellen und einzufuhren. Die stark angestiegenen Forschungs-und Entwicklungskosten fur ein neues Pflanzenschutzmittel - etwa 100 Mill. D- erschweren den Fortschritt ausserordentlich. Wenngleich die meisten neuen Ver- suchs- und Handelsprodukte Substanzgruppen entstammen, deren Bedeutung schon Ende 1976 erkannt worden war, und deren erste Versuchsprodukte bereits eine Weiterentwicklung anzeigten, so wurden doch auch spektakulare Ent- deckungen gemacht, von denen es wiederum erste Versuchsprodukte gibt. Herbi- zide mit Aufwandmengen von etwa 20 g/ha, also mit extrem guter Wirksam- keit zeigen, dass der Weg in unerwartetes Neuland noch lange kein Ende hat. Schon 1976 bekannte Verbindungsklassen, wie die der Diarylether-oxyalkan- carbonsauren, nicht nur von der Entdeckerfirma Hoechst AG intensiv bearbeitet, ergaben eine Fulle neuer Herbizide mit meist selektiver Graserwirkung.

Chemicals inhibiting the biosynthesis of branched-chain amino acids form a new and promising class of herbicides. This volume discusses in an authoritative way recent developments in this field and covers important aspects of these potent herbicides (synthesis, structure-activity, mode of action, selectivity, weed resistance, metabolism).

The compartmentation of genetic information is a fundamental feature of the eukaryotic cell. The metabolic capacity of a eukaryotic (plant) cell and the steps leading to it are overwhelmingly an endeavour of a joint genetic cooperation between nucleus/cytosol, plastids, and mitochondria. Alter ation of the genetic material in anyone of these compartments or exchange of organelles between species can seriously affect harmoniously balanced growth of an organism. Although the biological significance of this genetic design has been vividly evident since the discovery of non-Mendelian inheritance by Baur and Correns at the beginning of this century, and became indisputable in principle after Renner's work on interspecific nuclear/plastid hybrids (summarized in his classical article in 1934), studies on the genetics of organelles have long suffered from the lack of respectabil ity. Non-Mendelian inheritance was considered a research sideline ifnot a freak by most geneticists, which becomes evident when one consults common textbooks. For instance, these have usually impeccable accounts of photosynthetic and respiratory energy conversion in chloroplasts and mitochondria, of metabolism and global circulation of the biological key elements C, N, and S, as well as of the organization, maintenance, and function of nuclear genetic information. In contrast, the heredity and molecular biology of organelles are generally treated as an adjunct, and neither goes as far as to describe the impact of the integrated genetic system."

Air pollutants provide environmental conditions that drastically differ in many respects from those to which forest trees are naturally adapted. Leading experts in the field here consider these questions of immediate relevance arising from the changing environment: (1) Do air pollutants introduce effects of selection that differ from those known for populations that are not subject to such stress conditions? (2) If air pollutants introduce quantitatively or even qualitatively novel selective effects, which consequences might arise from the adaptation of forest tree populations to the present conditions as well as for the preservation of adaptability to future conditions? In addition to these questions, concepts for preservation of genetic resources are discussed.

Interdependence between species is a law of nature. The degree of this interdependence is vividly evident in the plant-microbial world. Indeed, there is no axenic plant in nature and one finds various forms of interac tions between these two kingdoms ranging from completely innocuous to obligate parasitic. Most of these interactions are poorly understood at the molecular and physiological levels. Only those few cases for which a molecular picture is emerging are discussed in this volume. With the advent of recombinant DNA technology and the realization that some of these interactions are very beneficial to the host plant, a spate of activity to understand and manipulate these processes is occurring. Microbes interact with plants for nutrition. In spite of the large number of plant-microbe interactions, those microbes that cause harm to the plants (i. e., cause disease) are very few. It is thus obvious that plants have evolved various defense mechanisms to deal with the microbial world. The mecha nisms for protection are highly diverse and poorly understood. Some pathogens have developed very sophisticated mechanisms to parasitize plants, an excellent example for this being crown gall caused by a soil bac terium, Agrobacterium tumefaciens. A remarkable ingenuity is exhibited by this bacterium to manipulate its host to provide nitrogenous compounds which only this bacterium can catabolize. This is carried out by a direct gene transfer mechanism from bacteria to plants."

This book is the first comprehensive description of development of the Acipenserid fish published in the English language. It con tains the results of more than 40 years of studies by the authors and their colleagues. My own life in science has been intimately related both with the authors and the fish, which are the subject of this book. Therefore, it gives me a great pleasure to present to the English reader an expanded version of the book. Those interested in the history of biology must be well aware of the fact that genetics in the USSR was practically demolished by Lysenko at the session of the Lenin All-Union Academy of Agricultural Sciences in 1948. However, it is much less well known that other fundamental branches of biology were also persecuted at that time, experimental embryology (developmental mechanics) among them. As a result, many embryologists, in cluding the authors of this book, were forced to turn to more ap plied problems, this being the only way to continue research. They had to abandon amphibians and concentrate their efforts on sturgeon."

Agricultural, natural resource, and environmental problems are becom ing increasingly interdependent. For example, soil erosion is largely determined by agricultural land use. Both water use and water con tamination depend on land use and technology choice in agriculture. In many areas, the fertilizers and pesticides used in agriculture are ma jor pollutants of ground and surface water, having adverse effects on drinking water and fisheries. Agricultural pollutants such as pesticides also produce adverse health effects for agricultural workers and the consuming public. On the other hand, the availability of water resources and the value of competing land uses influence agricultural production. Additionally, regional air quality problems may affect crops and global environmental trends may have long-term implica tions for farming. Agriculture, natural resources and environmental quality are all heavily regulated in the U. S., but they are done so by a vast array of competing or unrelated agencies within the U. S. Departments of Agriculture, Interior, and Commerce, the Environmental Protection Agency; and numerous state agencies. Considering the large number of bureaucratically remote public agencies involved and the pervasive in terdependencies between agriculture, natural resources and the environ ment, policies develop which are at best uncoordinated and at worst conflicting and counterproductive. These policies have become sources of controversy as different interest groups struggle to affect their im plementation, as different agencies have fought for administrative con trol and as legislative bodies have attempted to enact piecemeal changes."

Major and exciting changes have taken place recently in various aspects of bio technology and its applications to forestry. Even more exciting is the prospect of major innovations that the entire field of biotechnology holds for plant growth in general. The importance of these developments for the forestry sector is considerable, particu larly since forestry science has not received the kinds of technical and R&D inputs that, say, agriculture has received in the past few decades. Y ct the problems of defor estation as well as stagnation in yields and productivity of existing forests throughout the world are becoming increasingly apparent, with consequences and ecological ef fects that cause growing worldwide concern. Policies for application of existing knowl edge in biotechnology to the field of forestry and priorities for future research and development are, therefore, of considerable value, because it is only through the adop tion of the right priorities and enlightened policies that scientific developments will move along the right direction, leading to improvements in forestry practices through out the world. It was against this backdrop that the Tata Energy Research Institute (TERI) or ganised a major international workshop on the "Applications of Biotechnology in For estry and Horticulture" at New Delhi in January 1988. The present volume covers the proceedings of this international workshop."

The aim of this Handbook is to cover all fields that are necessary for the management of tropical forest resources. It provides proven and/or promis ing concepts, methods and available comparative data. The exten sive references cited are a valuable source for further in-depth research on specific subjects. The handbook is addressed to forestry professionals, natural re source managers and all those interested in the understanding and hand ling of day-to-day problems of tropical forest resources. It is an attempt to present, in a concentrated form, the vast ex perience gathered in tropical forestry. The available knowledge although far from complete, does not permit us to stand idly by when confronted with the dwindling tropical forests. Excuses not to tackle this problem are not acceptable. The experience of the last decades gives us sufficient background to apply techniques and concepts successfully, to encom pass the complexity of the human and the natural tropical environment. The authors responsible for the respective sections have been recom mended by institutions or individuals specialized in the subject. Our thanks go to aH those unnamed individuals whose dedication and responsible work made this handbook a reality. Our gratitude also to all the colleagues who supported the handbook in its early stages by their firm commitment."