The study of soils has taken on increased importance because a rapidly expanding population is placing demands on the soil never before experi enced. This has led to an increase in land degradation. Land degradation is one of the most severe problems facing mankind. Volume 11 of Advances in Soil Science was devoted entirely to this critical area of soil science. The editors of that volume, R. Lal and B.A. Stewart, defined soil degradation as the decline in soil quality caused by its misuse by humans. They further stated that soil degradation is a major concern for at least two reasons. First, it undermines the productive capacity of an ecosystem. Second, it affects global climate through alterations in water and energy balances and disruptions in cycles of carbon, nitrogen, sulfur, and other elements. Through its impact on agricultural productivity and environment, soil deg radation leads to political and social instability, enhanced rate of deforesta tion, intensive use of marginal and fragile lands, accelerated runoff and soil erosion, pollution of natural waters, and emission of greenhouse gases into the atmosphere. In fact, soil degradation affects the very fabric of mankind."

The Conference on Tropical Rainforest Research: Current Issues was organised by the University of Brunei Darussalam and The Royal Geographical Society, London, and held in Bandar Seri Begawan, Brunei Darussalam, over 8 days in April 1993. Over 160 participants from 22 countries attended the Conference, which was opened on the 9th April by the Brunei Darussalam Minister for Home Affairs, Yang Berhormat Pehin Orang Kaya Laila Setia Bakti Diraja Dato Laila Utama Haji Awang Isa bin Datu Perdana Menteri Dato Laila Utama Haji Awang Ibrahim. The conference was initially intended to provide a forum to present the results of the expedition into the lowland mixed dipterocarp forest of the Temburong District of Brunei Darussalam, which had been jointly organised by the University of Brunei Darussalam and The Royal Geographical Society, London. The 15-month expedition, lasting from January 1991 to March 1992, was based at the then newly-completed Kuala Belalong Field Studies Centre, a research and education facility set up by the University with funds provided by the Brunei Government and Brunei-Shell Petroleum Sdn Bhd. The expedition, with over 70 scientists taking part, received financial support from a wide range of sponsors and Corporate Patrons, including Royal Brunei Airlines, the Baring Foundation, Daiwa-Dicam, Greencard Trust, the Hongkong Bank, Morgan Grenfell and Nomura-Nimco. The conference itself was supported by donations from Brunei-Shell Sdn Bhd, Royal Brunei Airlines and Standard Chartered Bank.

Energy and agriculture are both extremely broad subjects and their interactions - the subject of this book - cover almost the full spectrum of the agricultural sciences. Yet the subject is a relatively new one whose importance first received widespread recognition barely a decade ago, following the dramatic increase in oil prices during 1973. The impact of this increase was such as to promote a world-wide debate on the future direction that agriculture should take. This debate was, and is, of particular concern in countries where agriculture plays a leading role in economic and social development. During the last half century many national agricultural systems have been transformed from almost closed, self-sufficient systems with few locally produced inputs geared to satisfy local requirements, to intensive, open systems, utilizing large quantities of energy-rich inputs such as fossil fuel for manufactured agro-chemicals, water distribution and imported animal feedstuffs to produce a range of sophisticated products, often for export, which in tum require many energy-rich inputs for their marketing. This industrialization of agriculture has proved to be very successful in many respects and indeed was accepted as a general model for agricultural development allowing increased productivity and efficiency per unit land, labor and water, even in areas with limited natural resources.

Outside Russia very little is known about the terrestrial ecology, vegetation, biogeographical patterns, and biodiversity of the enormously extensive ecosystems of Yakutia, Siberia. These systems are very special in that they function on top of huge layers of permafrost and are exposed to very severe and extreme weather conditions, the range between winter and summer temperatures being more than 100 degrees C. The soils are generally poor, and human use of the vegetation is usually extensive. Main vegetation zones are taiga and tundra, but Yakutia also supports a special land and vegetation form, caused by permafrost, the alas: more or less extensive grasslands around roundish lakes in taiga. All these vegetation types will be described and their ecology and ecophysiological characteristics will be dealt with. Because of the size of Yakutia, covering several climatic zones, and its extreme position on ecological gradients, Yakutia contains very interesting biogeographical patterns, which also will be described. Our analyses are drawn from many years of research in Yakutia and from a vast body of ecological and other literature in Russian publications and in unpublished local reports. The anthropogenic influence on the ecosystems will be dealt with. This includes the main activities of human interference with nature: forestry, extensive reindeer herding, cattle and horse grazing, etc. Also fire and other prominent ecological factors are dealt with. A very important point is also the very high degree of naturalness that is still extant in Yakutia's main vegetation zones.

The West African Sahel is the transition zone between the Saharadesert in the north of Africa and the more humid Sudanian zones in the south. Although diverse in many ways, the Sahelian countries have the common problem of a fragile agricultural sector. This predicament is mainly caused by low inherent soil fertility, limited and unpredictable rainfall, frequent droughts, and wind erosion that accelerates soil degradation and desertification, compounded by To assure food production in the future, means rapidly growing populations. of declining soil fertility and increasing must be found to offset the trends soil degradation through wind erosion. This is a challenge for agricultural research. Since 1985, the Special Research Program 308 'Adapted Farming in West Africa' at the UniversityofHohenheimin collaboration with the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Niger, has pursued the developmentof agricultural innovations for smallholder farmers in one of the most ecologically fragile regions of the world. The prevention of soil degradation, the restoration and maintenance of soil fertility, and the increase of land and labor productivity are key objectives of this multidisci plinary research program. From the beginning, a major focus of research has been wind erosion.

Nearly twenty years have passed since the publishing of a broadly-based texthook on hiolog ical control (Huffaker and Messinger 1976). In the interim, other works on biological control have been either briefer treatments (DeBach and Rosen 1991), or collections of essays on selected topics (Waage and Greathead 1986; Mackauer and Ehler 1990). Our text has been written to fill what we believe is a need for a well-integrated, broadly-based text of appropriate length and degree of technical detail for teaching a one semester upper level course in hiological control. We have attempted to focus on principles and concepts, rather than on biological control of particular taxa or hiological control by particular kinds of natural enemies. Therefore, for example, the reader will find the material on biological control of weeds integrated with biological control of insects and mites into chapters on principles, techniques, and applications rather than presented separately. Only biological control of plant pathogens is addressed independently, an appraoch made necessary by the many special features and concepts in plant pathogen biological control."

At the end of the 1970s, when signs of destabilization of forests became visible in Eu rope on a large scale, it soon became obvious that the syndrome called "forest de cline" was caused by a network of interrelated factors of abiotic and biotic origin. All attempts to explain the wide-spread syndrome by a single cause, and there were many of them, failed or can only be regarded as a single mosaic stone in the network of caus es behind the phenomenon. Forest ecosystems are highly complex natural or quasi natural systems, which exhibit different structures and functions and as a conse quence different resilience to internal or external stresses. Moreover, forest ecosys tems have a long history, which means that former impacts may act as predisposing factors for other stresses. The complexity and the different history of forest ecosys tems are two reasons that make it difficult to assess the actual state and future devel opment of forests. But there are two other reasons: one is the large time scale in which forests react, the other is the idiosyncrasy of the reactions on different sites. Due to the slow reaction and the regional complexity of the abiotic environment of forest ecosys tems, a profound analysis of each site and region is necessary to identify the underly ing causes and driving forces when attempting to overcome the destruction of forest ecosystems.

On the understanding that few people ever read the preface to any book and also on the understanding that even those few people who do read the preface realize that virtually nothing of any substance is ever said, I shall write at such length as will be proportional to my expected readership. The meetings of the International Society on Oxygen Transport to Tissue provide a forum for discussion amongst scientists who, although being from very diverse and specialized backgrounds, have tissue oxygenation as a unifying theme of interest. The wide variety of research material presented in this volume and the multiplicity of the experimental techniques described, should serve as an adequate gauge to the range of expertise and knowledge of the society's members. Such diversity should also stress the importance of the need for multidisciplinary approaches to complex biological problems. In attempting a fundamental characterization of a biological process such as tissue oxygenation, the application of very many separate research skills are necessary, such as mathematics, engi neering, biophysics, biochemistry, physiology, histology and clini cal medicine. The success of the ISOTT has - and we hope - will con tinue to be causing a combination of individuals to direct their specialized knowledge to the many facets of a single proces- tissue oxygenation."

The publication of this volume of The Viruses entitled The Togaviridae and Flaviviridae comes at an appropriate time. The structure and rep lication strategies of these viruses are now known to be sufficiently di verse to warrant the removal of flaviviruses from the Togaviridae family and establish them as an independent family. Flaviviridae have a special place in the history of virology. The prototype virus-yellow fever virus was the first virus to be identified as the cause of a human disease. Some of the history of this discovery is described in Chapter 1 of this volume; in Chapter 10 the complete sequence of the RNA genome of the virus is presented. This sequence not only defines the primary structure of the viral proteins, it also clarifies the mechanism of translation of the fla vivirus genome. Knowledge of the sequence of the structural proteins of these viruses represents an important step in the potential goal of using purified flavivirus glycoproteins as vaccines. Many of the chapters in this volume focus on the structure and replication of the Togaviridae. These viruses have provided valuable models for studies in cell biology, partic ularly with regard to the cotranslational and posttranslational steps re quired for the synthesis and localization of membrane glycoproteins. Fur thermore, Togaviridae have been pivotal in our growing understanding of how enveloped viruses enter and exit from cells. The broad outlines of the structure and gene expression of Togavir idae and Flaviviridae are known, but important questions remain."

Genetic Engineering, Volume 24 contains discussions of contemporary and relevant topics in genetics, including: -Gene silencing: principles and applications, -Integrins and the myocardium, -Plant virus gene vectors: biotechnology and applications in agriculture and medicine, -Novel approaches to controlling transcription, -Use of DNA polymorphisms in genetic mapping, -Application of FLP/FRT site-specific DNA recombination system in plants. This principles and methods approach to genetics and genetic engineering is essential reading for all academics, bench scientists, and industry professionals wishing to take advantage of the latest and greatest in this continuously emerging field.

Proceedings of the NATO Advanced Research Workshop on Phytotoxins and Plant Pathogenesis held at Capri, Italy, May 30 - June 3, 1988

Chromosomes. being well-defined structures that are easily vis ible under the optical microscope. readily lend themselves to in tense physical and biochemical study. The understanding of the structure and function of this most critical genetic material has progressed through a number of interesting stages. Often connected with the development of new techniques in staining and photography. using the standard microscope and the electron microscope. It is interesting to look back at the history of cytogenetics. I would like especially to emphasize the work of Karl Sax and many of his students. Work with Tradescantia became feasible after Edgar Anderson straightened out the ecology and Sax took advantage of the small number of chromosomes easily visible under the microscope. As a matter of fact. this development is seen as the foundation for the quantitative analysis of radiation effects on chromosomes. During the 50 years since then.- more refined studies have been initiated. The study of cytogenetic mechanisms has become an important tool for the recognition of the effects of environmental factors on all liv ing systems and has made SCE studies possible. One of the most important stages in chromosome research was the development, in radiation biology, of radiolabeling the chromosome with tritiated thymidine. This technique. published in 1957 by Dr.

The last decade has seen tremendous progress in our knowledge of the pollen development and gene expression on one hand and the characterization of pollen specific proteins on the other. In compiling the chapters for this volume, we have pragmatically categorized these basic developments in pollen molecular biology and biotechnology into two sections based on their applications in agricul ture and implications in medicine. Pollen developmental biology and gene expression: applications in agricul ture. Pollen development is an extremely complex process encompassing a series of biochemical, physiological and genetic events. At the basic level, sporophyt ically expressed genes may expound our knowledge of unique processes of cellular differentiation which ultimately give rise to a full-fledged organism. At the applied level, the studies on the pollen and male sporophyte-specific gene expression, and of promoters and transcription factors of relevant genes have the potential to manipulate the fertility in certain cash crops leading to agricultural biotechnology."

Towards the Balance and Management of the Carbon Budget of the Biosphere The current state of misunderstanding of the global C cycle and our failure to resolve an issue that has been debated for 100 years (Jones and Henderson-Sellers, 1990) speaks loudly about the limitations of modem science when faced with the complexity of the biosphere. Efforts to understand and balance the global C budget have gone through several phases. First was a holistic view of the C budget as part of efforts to understand the geochemistry of the Earth (e. g. , Clarke, 1908). Next, came a period of data collection and sythesis which focused on the diversity of sectors of the biosphere. This phase culminated in the early 1970's with the realization that humans were greatly impacting the global C cycle as measured at the Mauna Loa Observatory (Keeling et al. , 1973). New syntheses of the global C budget emerged at this time (Woodwell and Pacan, 1973; Bolin et al. , 1979). The next phase was one of controversy and intense focus on particular sectors of the biosphere. The controversy rested on discrepancies about the role of the terrestrial biota in the global C cycle and the failure to account for sufficient C sinks to absorb all the C emitted by land-use change in the tropics (Woodwell et al. , 1978, 1983; Houghton et al. , 1983).

In the last few decades there has been an ever-increasing component in most BSc Zoology degree courses of cell biology, physiology and genetics, for spectacular developments have taken place in these fields. Some aspects of biotechnology are now also being included. In order to accommodate the new material, the old zoology courses were altered and the traditional two-year basis of systematics of the animal kingdom, comparative anatomy (and physiology) and evolution, was either severely trimmed or reduced and presented in an abridged form under another title. Soon after these course alterations came the swing to modular teaching in the form of a series of shorter, separate courses, some of which were optional. The entire BSc degree course took on a different appearance and several different basic themes became possible. One major result was that in the great majority of cases taxonomy and systematics were no longer taught and biology students graduated without this basic training. We field biologists did appreciate the rising interest in ecology and environ mental studies, but at the same time lamented the shortage of taxonomic skills, so that often field work was based on incorrect identifications. For years many of us with taxonomic inclinations have been bedevilled by the problem of teaching systematics to undergraduates. At a guess, maybe only 5% of students find systematics interesting. It is, however, the very basis of all studies in biology - the correct identification of the organism concerned and its relationships to others in the community."

Drawing from a decade-long collaboration between Japan and Russia, this important volume presents the first major synthesis of current knowledge on the ecophysiology of the coniferous forests growing on permafrost at high latitudes. It presents ecological data for a region long inaccessible to most scientists, and raises important questions about the global carbon balance as these systems are affected by the changing climate.

Making up around 20% of the entire boreal forests of the northern hemisphere, these permafrost forest ecosystems are subject to particular constraints in terms of temperature, nutrient availability, and root space, creating exceptional ecosystem characteristics not known elsewhere. This authoritative text explores their diversity, structure, dynamics and physiology. It provides a comparison of these forests in relation to boreal forests elsewhere, and concludes with an assessment of the potential responses of this unique biome to climate change.

The book will be invaluable to advanced students and researchers interested in boreal vegetation, forest ecology, silviculture and forest soils, as well as to researchers into climate change and the global carbon balance. "

Like many genetic engineers, I have recently been receiving the atten tion of various venture capital companies, international drug houses and Members of Parliament. I will not discuss which of these approaches are most welcome, but it did cause me to consider the speed of advance in genetic engineering, and the implications of this rapid growth. There were few who anticipated it - only five years ago, most scientists thought applications would come at the end of the century, yet we see products such as insulin and interferon already available for clinical testing. In Europe in general and Britain in particular, this explosive growth in our own field has coincided with a general industrial depression and a marked reduction in funding for biomedical research. The brain drain from Britain is a serious matter, for we are losing the best of our younger scientists, on whom we would rely to train the next generation of molecular biologists. These volumes have come from British labs (mostly because I happen to be based in London, and my contacts and friends are here), and I feel that the quality of the con tributions also shows that our current research is of a high standard.

Genetics and Genomics of Populus provides an indepth description of the genetic and genomic tools and approaches for Populus, examines the biology that has been elucidated using genomics, and looks to the future of this unique model plant. This volume is designed to serve both experienced Populus researchers and newcomers to the field. Contributors to the volume are a blend of researchers, some who have spent most of their research career on Populus and others that have moved to Populus from other model systems. Research on Populus forms a useful complement to research on Arabidopsis. In fact, many plant species found in nature are - in terms of the life history and genetics - more similar to Populus than to Arabidopsis. Thus, the genetic and genomic strategies and tools developed by the Populus community, and showcased in this volume, will hopefully provide inspiration for researchers working in other, less well developed, systems.

The original aim of this book was to cover different aspects of the tradi tionally "filamentous" potex-, carla-, poty-, clostero-, and capilloviruses. The title The Filamentous Plant Viruses seemed the only suitable one, but it has led us to discuss also the quite different filamentous viruses of the rice stripe group-recently officially named the tenuivirus group which otherwise, indeed, might not have been conveniently covered in any volume of this series. The question must be asked: What is there new that justifies the presentation of a book of this kind? An outline of the answer may be Among the traditional filamentous viruses, much pro given as follows. gress has been made in elucidating the physical structure of potexvirus particles, and this work serves as an excellent model for discussion of and future experiments on the poty-, carla-, clostero-, and capilloviruses, which have comparable structures, although they are more difficult to manipulate. Work on the structure and strategy of the genomes of poty viruses is, however, relatively advanced and at a very interesting stage. The helper component that assists the aphid transmission of potyviruses has also recently received considerable attention, although the more we know about that, the less seems clear about the aphid transmission of the carlaviruses and closteroviruses, which apparently neither possess nor require a helper component."

Interest in trees, whether in our streets, parks or forests, has in- creasedconsiderablyin thelast 20 years or so.One reason for this has been the decline and dying of forests, which caused great concern about our environment during the 1980s. Because ofthe prominenceofthis event,which is nowblamedon abiotic factors, it is all too easyto forget that the life oftrees is also affected by a multitude of biotic factors: viruses, bacteria, fungi and animals. These may have very different relationships with trees, but are usually deleterious. The fungi playa particularlyimportant part, and during the course of their evolution they have developed various abilities and strategies in order to obtain nutrients and energy by decomposing wood. On the other hand, the tree has 'learned' to react to external and internal infections. The various interactions between fungi and trees form the main themeofthis book. In reviewing this new book I was involuntarily reminded of a work by Robert Hartig over a century ago, entitled Die Zerset- zungserscheinungen des Holzes der Nadelbiiume und der Eiche in forstlicher, botanischer und chemischer Richtung, which laid the foundation of mycological and pathological research on wood.

This book was developed from the proceedings of the American Chemical Society, Division of Agricultural & Food Chemistry, subdivision of Natural Products Symposium "Biosynthesis and Metabolism of Secondary Natural Products" held in Atlanta, Georgia, April 1991. The objective of the conference was to bring together people from apparently diverse fields, ranging from biotechnology, metabolism, mechanistic organic chemistry, enzymology, fermentation, and biosynthesis, but who share a common interest in either the biosynthesis or the metabolism of natural products. It is our intention to help bridge the gap between the fields of mechanistic bio-organic chemistry and biotechnology. Our thanks go to Dr. Henry Yokoyama, co-organizer of the symposium, the authors who so kindly contributed chapters, the conference participants, and to those who assisted in the peer review process. We also thank the financial supporters of the symposium: ACS/AGFD, NIH General Medical Sciences, and the agricultural, pharmaceutical, biotechnology, and chromatography companies. A full list of the supporting corporations and institutions is given on the following page. Pharma-Tech and P.C., Inc. are manufacturers of instrumentation for high-speed countercurrent chromatography. We thank the Agricultural Research Service and the U. S. Department of Agriculture for granting me permission to co-organize the conference and for us to complete the book. Richard J. Petroski Susan P. McCormick USDA, ARS, National Center for Agricultural Utilization Research Peoria, IL 61604 June 10, 1992 vii CONTENTS ANTIBIOTICS Polyketide Synthetases: Enzyme Complexes and Multifunctional Proteins Directing the Biosynthesis of Bacterial Metabolites from Fatty Acids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . . . . . . . . . . .

This is an extended version of lectures that were held at the summer workshop Atmosphiirische Umweltforschung im Spannungsfeld zwischen Technik und Natur (At mospheric Environmental Research between Technology and Nature) at the Techni 16, 1996. We were very happy to have Paul J. Crutzen, cal University in Cottbus on July winner of the Nobel Prize for chemistry in 1995, presenting the key lecture on glo bally changing chemistry in the atmosphere. Over the last decades, atmospheric chem istry has been established step by step, not just as an applied discipline of chemistry, but also as a key discipline for our understanding of air pollution, biogeochemical cycling, and climactic processes as well. In fact, the new definition of meteorology as the science of physics and chemistry of the atmosphere expresses this development very well. The chemistry of the atmosphere is strongly influenced by anthropogenic emissions, even on a global scale. As a result of emissions and chemical reactions, the chemical composition of the atmosphere influences the ecosystems directly via depo sition of trace substances, and indirectly by changing the physical climate. Therefore, in this book we combined state-of-the-art lectures describing the physical and chemi cal status of the atmosphere and selected issues representing the interface between atmosphere, technology and nature. Oxidising capacity, heterogeneous processes and acidity still remain as key issues in atmospheric chemistry, even in regions where efficient air control measures have been adopted resulting in reduction of primary atmospheric pollutants."

Genetic material is in flux: this is one of the most exciting recent concepts in molecular biology. This volume of "Plant Gene Research" describes changes that occur in the genetic material of plants. It is worthwhile re membering that the first examples of unstable genomes were described for maize before DNA was known to be the genetic material. Now trans posable elements like the ones found in maize have been described in almost all organisms and have become incorporated into our thinking about genome structure. Flux in the plant genome is not restricted to transposable elements or to nuclear genes. Exchanges of genetic material have been demonstrated within organelle DNA, between organelle DNAs or between organelle and nuclear DNAs. Such exchanges may only occur over evolutionary times or may be a continuing process. Also the environment alters the plant genome. Stress, either viral, nutri tional or tissue-culture induced causes heritable changes in the genome. Infection with the crown gall bacterium Agrobacterium tumefaciens results in the transfer of bacterial DNA into the plant genome."