First attempts to isolate plant genes were for those genes that are abun dantly expressed in a particular plant organ at a specific stage of devel opment. However, many important gene products are produced in a very minute quantity and in specialized cell types. Such genes can now be isolated using a variety of approaches, some of which are described in this volume. The rapid progress during the last decade in regeneration of a number of crop plants and the availability of molecular tools to introduce foreign genes in plants is allowing the engineering of specific traits of agri cultural importance. These genes must, however, be regulated in a spatial and temporal manner in order to have desired effects on plant devel opment and productivity. The habitat of plants necessitate adaptive responses with respect to the environmental changes. Starting from germination of the seed, the plant begins to sense environmental cues such as moisture, light, temperature and the presence of pathogens, and begins to respond to them. Little is known about various signal transduction pathways that lead to biochemical and morphogenetic responses, in particular, transition from vegetative to reproductive phase. With the availability of tools to generate specific mutations via transposon tagging, identification and isolation of genes affecting these processes may be facilitated. Transfer of these genes into heterologous environments will allow understanding of the complex processes that control plant development."

Research on decomposer communities of terrestrial ecosystems for a long time has focussed on microbial biomass and gross turnover parameters. Recently, more and more attempts are made to look beyond the biomass, and more specifically determine functions and populations on a smaller scale-in time and space. A multitude of techniques is being improved and developed. Garland and Mills (1991) triggered a series of publications on substrate utilization tests in the field of microbial ecology. Despite several promising results for different applications in different laboratories, many problems concerning the assay and the interpretation of results became evident. After individual discussions on the approach with colleagues from various laboratories we started to plan a workshop on the matter. The response on our first circular was extraordinary, and instead of a small workshop it became a meeting with almost 150 participants. The meeting was named 'Substrate use for characterization of microbial communities in terrestrial ecosystems' (SUBMECO) and was held in Innsbruck, Austria, from Oct. 16-18, 1996. The very focussed scope attracted enthusiastic advocates of the approach, and also serious critics. Some of the topics concerned improvements of current inoculation and incubation techniques, ranging from sample pre-treatment, inoculum density and incubation temperature to statistical data handling. New methods for calculating microbial diversity were proposed, as well as bootstrap methods that allow statistics with many variables on a relatively low number of replicates.

In recent years many of the conventional methods of insect control by broad spectrum synthetic chemicals have come under scrutiny because of their unde sirable effects on human health and the environment. In addition, some classes of pesticide chemistry, which generated resistance problems and severely affected the environment, are no longer used. It is against this background that the authors of this book present up-to-date findings-relating to biochemical sites that can serve as targets for developing insecticides with selective prop erties, and as the basis for the elucidation of resistance mechanisms and countermeasures. The book consists of eight chapters relating to biochemical targets for insec ticide action and seven chapters relating to biochemical modes of resistance and countermeasures. The authors of the chapters are world leaders in pesti cide chemistry, biochemical modes of action and mechanisms of resistance. Biochemical sites such as chitin formation, juvenile hormone and ecdysone receptors, acetylcholine and GABA receptors, ion channels, and neuropeptides are potential targets for insecticide action. The progress made in recent years in molecular biology (presented in depth in this volume) has led to the iden tification of genes that confer mechanisms of resistance, such as increased detoxification, decreased penetration and insensitive target sites. A combina tion of factors can lead to potentiation of the resistance level. Classifications of these mechanisms are termed gene amplification, changes in structural genes, and modification of gene expression.

Soil is formed from the physical and chemical weathering of rocks-processes described historically because they involve eons of time-by glaciation, and by wind and water transport of soil materials, later deposited in deltas and loessial planes. Soil undergoes further transformations over time and provides a habitat for biological life and a base for the development of civilizations. Soil is dynamic - always changing as a result of the forces of nature and particularly by the influences of man. Soils have been studied as long as history has been documented. W. H. Gardner told of writings on clay tablets, dating about 1700 Be, in his review, "Early Soil Physics into the Mid-20th Century;' published in Volume 4 of this series. Those writings gave specific instructions on cultivating the soil and seeding crops. Numerous references to soil are found in historical writings, such as Aristotle (384-322 Be), Theophrastus (372-286 Be), Cato the Elder (234-149 Be), and Varro (116-27 Be). Some of the earliest historical refer ences to soil 3000 or more years ago have to do with erosional forces of wind and water. The study of soils today has taken on increased importance because a rapidly expanding population is placing demands on soil that has never before been experienced. Soil scientists have professionally divided themselves into separate disciplines-physics, chemistry, microbiology, mineralogy, genesis, and the like. Studies range from very basic to very applied, and to literally every corner of the earth, and ofthe moon as well."

In the past 10 years, there has been a resurgence in interest in soil management and conservation of the soil resource. With the knowledge we have accumulated in the past 100 years, there is the possibility of developing new and innovative ways of effectively managing the soil. The emphasis on sustainable agriculture requires that we understand how to utilize the soil as a viable living resource. To meet the world demand for food within the next 50 years requires a healthy and strong soil resource which can sustain production. With the dedication of the National Soil Tilth Laboratory in 1989, it was decided that one contribution the laboratory could make to agri cultural science would be to foster an exchange of information on soil management. The focus of that interchange centers on long-term soil management. If we are to fulfill the goals of sustainable agriculture, environmental quality, and feeding the world, there will have to be an increased understanding of how to effectively manage the soil. Long-term soil management requires integrated and interdisciplinary research to bring all of the information together in terms which would be applicable to all soils. To accomplish this goal a workshop is held each year, with the exchange of information focusing on a single topic within the framework of developing effective strategies for long-term soil management. With the forum to focus on an individual theme each year, the theme for the initial workshop was "Limitations to Plant Root Growth."

The world needs for food and fiber continue to increase. Population growth in the developing countries peaked at 2. 4 percent a year in 1965 and has fallen to about 2. I percent. However, in many developing countries almost half the people are under 15 years of age, poised to enter their productive and reproductive years. The challenges to produce enough food for this growing population will remain great. Even more challenging is growing the food in the areas of greatest need. Presently the world has great surpluses of food and fiber in some areas while there are devastating deficiencies in other areas. Economic conditions and the lack of suitable infrastructure for distribution all too often limit the alleviation of hunger even when there are adequate supplies, sometimes even within the country itself. World hunger can only be solved in the long run by increasing crop production in the areas where the population is growing most rapidly. This will require increased efforts of both the developed and developing countries. Much of the technology that is so successful for crop production in the developed countries cannot be utilized directly in the developing countries. Many of the principles, however, can and must be adapted to the conditions, both physical and economic, of the developing countries. This series, Advances in Soil Science.

"Reviews of Environmental Contamination and " "Toxicology"contains timely review articles concerned with all aspects of chemical contaminants (including pesticides) in the total environment, including toxicological considerations and consequences. It attempts to provide concise, critical reviews of advances, philosophy, and significant areas of accomplished or needed endeavor in the total field of residues of these and other foreign chemicals in any segment of the environment, as well as toxicological implications.

A knowledge of forest site and forest productivity variables is fundamental to sound forest practice everywhere. The ability to identify sites and site problems correctly and manipulate productivity variables for maintenance or improvement of productivity is the basis of modern forest management. Although the basic facts regarding forest site and productivity apply throughout the world, the application of information and the response to manipulation vary greatly and depend on local forest conditions. The September 1981 World Congress of the International Union of Forest Research Organizations (IUFRO) in Kyoto, Japan was the occasion for the special meeting on Forest Site and Productivity sponsored by the IUFRO Site Group Sl.02. This meeting brought together forest site and productivity researchers from across the world to review current thought and the state of site research. Information not ordinarily available in one place was presented at this meeting. As organizer of the session, I decided to attempt to publish the papers in one volume. Arrangements were made with a publisher, Martinus Nijhoff, and also with the authors. The process of publication has taken longer than desirable, but the volume does appear at an opportune time coincident with the 1986 IUFRO World Congress in Yugoslavia. Material contained in this publication will set the stage for Site Group discussions at the 1986 meeting. This volume assembles the thought of forest research workers from many different countries and therefore many different kinds of forests.

The comparative study of mediterranean type ecosystems has gained considerable momentum during the past two decades. Modem studies on these systems date from the work of Ray Specht, who studied the dynamics of the heath vegetation of south ern Australia. The results of these studies first appeared in 1957 (Specht and Rayson, 1957) and were summarized in 1973 (Specht, 1973). Specht followed this detailed work, which pointed to the central role of nutrients in limiting the productivity of the Australian heath, with a general comparison of the structural features of woody plant communities in mediterranean type ecosystems of Australia, southern France, and southern California (Specht, 1969a, b). The comparative studies emphasized remark able convergent features of these ecosystems, particularly in relation to structural features affecting primary production. Naveh (l967) also did comparative studies focusing on grassland types that occur in the mediterranean climatic zones of Califor nia and IsraeL About this same time, independent studies by Mooney and Dunn (1970 a, b) and Mooney et al. (1970) made preliminary structural and functional comparisons of the vegetations of mediterranean type ecosystems in California and Chile in an at tempt to derive an evolutionary model explaining the basis of their convergent natures. Much of the knowledge of these ecosystems up to 1973 was summarized in volume 7 of Ecological Studies, Medite"anean Type Ecosystems: Origin and Structure (di Castri and Mooney, 1973). This volume builds on its series predecessor in many ways."

Providing a link between theoretical and applied aspects of plant nutrition and agriculture, this book introduces new concepts in plant nutrition. It shows how these can be applied in order to assess the nitrogen status in crops and to improve nitrogen nutrition through optimized N fertilization management. In this way economic benefits can be obtained, while at the same time preventing detrimental effects on the environment. The main agricultural crops - grasses, wheat, barley, Durum wheat, maize, sorghum, grain legumes and potatoes - are covered. The book will be an invaluable source for agronomists.

"Reviews of Environmental Contamination and Toxicology" contains timely review articles concerned with all aspects of chemical contaminants (including pesticides) in the total environment, including toxicological considerations and consequences. It attempts to provide concise, critical reviews of advances, philosophy, and significant areas of accomplished or needed endeavor in the total field of residues of these and other foreign chemicals in any segment of the environment, as well as toxicological implications.

Policy issues relating to forestry have been the subject of much debate in recent years, and many countries and international agencies have recently, or are currently in the process, of revising their policies for forestry. Much of this debate has implied that previous policies have failed or been much less successful than had been hoped. There is a tendency to think of policy as a matter for governments, but it is now more widely appreciated that all shareholders in the forestry sector have a legitimate interest in both the policy objectives and the means that will be used to implement it.

This book is mainly concerned with the process of developing policy and the subsequent implementation, than in specific content, though many of the important issues which policies must address are discussed. It is based on a review of many case studies with which the author has been personally involved over the past 40 years.

Production of food to meet the demands of an ever-increasing human population in the world is the major task and challenge to agriculture today. The conventional methods of plant breeding alone can no longer cope with the situation. The success of any crop improvement program depends on the extent of genetic variability in the base population, but due to denuding of forests and agricultural land, the naturally occurring pool of germplasm is being depleted. An urgent need is therefore ap parent to create new variability and increase the genetic base of agricul tural crops. Agricultural biotechnology has progressed to a stage in the produc tion of plants where specific characteristics to improve their yield, ap pearance, disease-resistance, nutritional quality and adaptation to ad verse soil conditions can be built into the seed. This concept of built-in quality implies a continuous scientific endeavour to improve plant char acters using a wide range of possibilities, and it also implies a scrutiny of the materials and methods available in the world today."

The International Society ofSoil Science was organized in 1924 and the 1st International Congress ofthe Society was held in Washington, D. C. , United States ofAmerica, in 1927. The 14th Congress was held August 12-18, 1990 in Kyoto, Japan. Dr. Akira Tanaka, Society President, stated "It is a serious concernofpeopleintheworldtosustainhighfarming productivityfor feeding the ever growing population,and also to protect the environment for human habitation. For this purpose, it is necessary to maximize crop yield per unit field areathroughintensivemanagementofthesoilandcropsonlands which are best suited for crop production, and to leave lands which are suboptimal for crops under natural conditions insofar as possible. Soil science is respon- siblefor planningtheoptimumland-usesystem,for managing soilsand crops with maximum efficiency, and for fighting intelligently against soil deteriora- tion. " Dr. Tanaka clearly stated the challenges facing soil scientists, and they are indeed challenges. Even though the rate ofworld population growth has decreased somewhat in recent years, the consensus is that total population willdouble-to some ten billion-beforeit stabilizes. The increased produc- tion of food, fiber, and fuelwood necessary for the people will require a continued supply ofnew technologies and management practices. The consensus of many scientists is that the greatest challenge is not increasing production, but preventing serious deterioration of the soil and waterresource base so theproductionlevel can be sustained. Therearemany historical examples where civilizations were successful for extended periods onlytoseesoildegradationleadtotheircollapse.

The emergence of landscape ecology during the 1980s represents an impor tant maturation of ecological theory. Once enamored with the conceptual beauty of well-balanced, homogeneous ecosystems, ecologists now assert that much of the essence of ecological systems lies in their lumpiness. Patches with differing properties and behaviors lie strewn across the land scape, products of the complex interactions of climate, disturbance, and biotic processes. It is the collective behavior of this patchwork of eco systems that drives pattern and process of the landscape. is not an end point This realization of the importance of patch dynamics in itself, however. Rather, it is a passage to a new conceptual framework, the internal workings of which remain obscure. The next tier of questions includes: What are the fundamental pieces that compose a landscape? How are these pieces bounded? To what extent do these boundaries influence communication and interaction among patches of the landscape? Will con sideration of the interactions among landscape elements help us to under stand the workings of landscapes? At the core of these questions lies the notion of the ecotone, a term with a lineage that even predates ecosystem. Late in the nineteenth century, F. E. Clements realized that the transition zones between plant communi ties had properties distinct from either of the adjacent communities. Not until the emergence of patch dynamics theory, however, has central signif icance of the ecotone concept become apparent."

This series is dedicated to serving the growing community of scholars and practitioners concerned with the principles and applications of environmental management. Each volume will be a thorough treatment of a specific topic of importance for proper management practices. A fundamental objective of these books is to help the reader discern and implement human's stewardship of our environment and the world's renewable resources. For we must strive to understand the relationship between humankind and nature, act to bring harmony to it, and nurture an environment that is both stable and productive. These objectives have often eluded us because the pursuit of other individual and societal goals has diverted us from a course of living in balance with the environment. At times, therefore, the environmental manager may have to exert restrictive control, which is usually best applied to humans, not nature. Attempts to alter or harness nature have often failed or backfired, as exemplified by the results of imprudent use of herbicides, fertilizers, water, and other agents. Each book in this series will shed light on the fundamental and applied aspects of environmental management. It is hoped that each will help solve a practical and serious environmental problem.

At present, no single book adequately covers a basic understanding of wood book satisfies the need for such a work. It describes drying in practice. This the fundamental basis of kiln-drying technology, to enable forest companies to imFrove their drying operations as high-quality timbers become scarcer and of yesteryear can no longer be tolerated. Adaptive the wasteful practices is no longer good enough. Innovations change based on past experience of the material being dried and the processes require a sound understanding of drying. Newer techniques, such as the use of ultrahigh temperature sea soning and superheated steam under vacuum, require an even greater depth of physical understanding for these methods to be used effectively and economically. book provides a description of modern ideas about wood structure, This moisture movement and stress development, from which models of the drying process are developed to give the kiln operator important information about the course of drying under specified conditions, and thus a means is compared with practice wherever for rational process improvement. Theory possible."

Biologists ask how the growth, development and behaviour of organisms happen, how these processes are co-ordinated and how they are regulated by the environment. Today the questions are phrased in terms of the genes involved, their structure and the control of their expression. Mutations (recognised by a change in phenotype) label genes and can be used to study gene structure, gene function and the organisation of the genome. This is "Genetics." Study of phenotypes down to the level of the enzymes and structural proteins coded for by genes is "Biochemistry." It is self evident that only by studying phenotype ("Biochemistry") can we do "Ge netics" and that "Genetics" (perturbation of the phenotype) is the key to understanding the "Biochemistry." There can surely be no better argu ments for a more holistic approach to biology than the massive output of knowledge from microbial "Biochemical Genetics" and the more recent revelations from "Molecular Genetic" studies of development in Droso phila."

DEVELOPMENT AND DISTURBANCE IN AMAZON FORESTS Contrasting Impressions 6 2 The rain forests of the Amazon Basin cover approximately 5.8 x 10 km (Salati and Vose 1984). Flying over even just part of this basin, one gazes hour after hour upon this seemingly infinite blanket of green. The impression of immen sity is similar when viewed from the Amazon River itself, or from its tributar ies. From a hammock on the shaded deck of a riverboat, the immensity of the forest presents an incredible monotony as one view of the shoreline blends unnoticeably into another. From both perspectives, the overwhelming reaction to the sea of trees that stretches from horizon to horizon is a sense of the vastness of the rain forest. In September 1985, I got a different impression of the rain forest. Several students and I journeyed in a self-propelled car along the single-track railroad that stretches almost 1000 km from the Carajas iron ore mine in the rain forest of Para State, Brazil, all the way to Sao Luis on the coast (Fig. 1.1)."

It is currently impossible to grow lichens under controlled conditions in the laboratory in sufficient quantity for physiological experiments. Lichen growth is slow and conditions which might accelerate the process tend to favour either the algal or fungal partner, resulting in the breakdown of balance symbiosis. Lichen physiologists are therefore forced to use field-grown material with all the problems associated with the unknown influences of unpredictable and unreproducible climatic conditions. Study of major biochemical topics, such as the nature of the carbohydrate and nitrogenous compounds passing between the symbionts, is less influenced by climatic conditions than the intrinsic nature of the symbionts and many advances have been made in these areas. Recently, the challenge of using field-grown plant material, the physiological status of which is intimately linked to environmental conditions, has proved to be a stimulus rather than a hindrance to a number of research groups. The occurrence of lichens in extreme habitats has prompted a number of field and laboratory studies with material from such diverse localities as the cold deserts of Antarctica and the temperate rain forests of the New Zealand bush. A comparative approach, using contrasted species or habitats from a particular geographical region has yielded much information and an appreciation of the variety of physiological adaptations which may exist. The close linkage between morphology and physiology is now being directly demonstrated, as is the relevance of ultrastructural information.

This book addresses basic questions concerning the ecological relationships and current conditions of the major river systems in Florida . . There have been relatively few comprehensive studies made of the rivers of Florida. There is, to be sure, voluminous information that addresses various aspects of riverine ecology. However, little such information has been collected in a way that allows even a preliminary understanding of the driving forces that determine how the diverse freshwater and associated brackish systems function. This lack of useful data is the product of a fundamental ignorance concerning the scale of endeavor, both spatially and temporally, that is needed if we are to understand and, parenthetically, manage the major drainage systems of this area of the country (Livingston, 1987). Research used to address management problems should entail a continuous series of interrelated studies, descriptive and experimental, that answer the immediate (and often less important) questions that are asked on a day-to-day basis. The research should also be designed to answer questions that have not yet been asked. In other words, ecosystem research should be organized on an appropriate scale so that system-wide processes are understood and pr

'frees contribute a major part of fuel, fodder and fruit, and are an im of bioenergy. They are now needed in large numbers more portant source than ever before for afforestation and social forestry, so that fast-grow ing and multipurpose trees assume great importance. After extensive in discriminate deforestation and rapid depletion of genetic stocks, efforts are now being made to evolve methods for clonal mass propagation of improved and elite trees. Production of short-duration trees with a rapid turnover of biomass, and induction of genetic variability through in vitro manipulation for the production of novel fruit and forest trees, which are high-yielding and resistant to pests and diseases, and trees which display increased photosynthetic efficiency are in demand. These objectives are well within the realm of horticultural and forest biotech nology. Some of the recent advances, such as the regeneration of com plete trees from isolated protoplasts, somatic hybridization, and the Agrobacterium-mediated transformation in various tree species have opened new vistas for the genetic engineering of fruit and forest trees. This book is a continuation of the earlier volume Trees I, and presents 31 chapters on fruit, forest, nut and ornamental trees, such as avocado, pineapple, crabapple, quince, pistachio, walnut, hazelnut, date palm, oil palm, cacao, rubber, maple, sweet-gum, poplars, birches, Chinese tallow, willows, oaks, paper mulberry, rhododendrons, Scots pine, Calabrian pine, Douglas-fir, redwood, ginkgo, cycads and some flowering trees."

The key to sustaining the soil resource base is to maintain, or enhance, soil quality. Soil quality cannot be seen or measured directly from the soil alone but is inferred from soil characteristics and soil behavior under defined conditions. In essence, the quality of soils is analogous to the health of humans, and just as there is no single characteristic that can be measured to quantify a person's health, there is no single measurement that can quantify soil quality. However, there are certain characteristics, particularly when considered together, that are good indicators. Soil quality, just as human health, can be maintained or enhanced by good management practices; and seriously degraded-sometimes irrevers ibly-with poor practices. Soil quality is also important because it has direct and indirect effects on air quality and water quality. While the enhancement of soil quality does not always assure parallel improvements in the quality of air and, particularly, water resources, this is often the case. However, soil deg radation is invariably accompanied by degraded qualities of both air and water resources. The consensus among many scientists is that the greatest challenge is not increasing production, but preventing serious deterioration of the soil and water resource base so that the production level can be sustained."

PH. BOURDEAU Directorate-General Science. Research and Development. Commission of the European Communities. Brussels. Belgium We are living on a unique planet, the only one in the solar system where life exists. The very existence of life has modified the physical and chemical environment of the earth, its atmosphere and oceans, in a way that makes life sustainable. This system with its complex cybernetic mechanisms has been named GAIA by Lovelock. Man has always interfered with it on a more or less limited scale. This interference is now reaching global proportions such as climate modifications resulting from CO and trace gas 2 accumulation in the atmosphere or the destruction of stratospheric ozone, not to speak of global radioactive contamination. GAIA will probably prevail as a living system but it probably does not give much importance to man's survival as such, and it is man that has to take care of his own survival. In the ecosystem of Planet Earth, soils are the thin interface between lithosphere and atmosphere which constitutes the essential substrate for the terrestrial biosphere, the productivity of which far exceeds that of the oceans, even though the latter cover a much larger area than the continents. Soils themselves are complex systems. They develop through weathering of minerals, are colonised by living organisms which in turn modify their substrate making it suitable for other organisms. This induces a primary ecological succession which eventually reaches a climax, in equilibrium between climate, soil and the biological communities.

The study of soils today has taken on increased importance because a rapidly expanding population is placing demands on the soil never before experienced. 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. From the beginning of agriculture until about 1950, increased food production came almost entirely from expanding the cropland base. Since 1950, however, the yield per unit of land area for major crops has increased dramatically. Much of the increase in yields was because of increased inputs of energy. Between 1950 and 1985, the farm tractor fleet quadrupled, world irrigated area tripled, and use of fertilizer increased ninefold. Between 1950 and 1985, the total energy used in world agriculture increased 6. 9 times. Until recently, sustainability was seldom, if ever, mentioned in agricultural literature. Now, it is one of the most widely used terms. The high costs ofirriga tion development, escalating energy costs during the 1970s, public concern over potential negative impacts of fertilizer and pesticides on water supplies, soil ero sion, soil compaction and salinity problems, and other concerns have caused many people to question whether many of the present agriculture systems can be sustained. As a result, soil science is beginning to focus more on sustaining the resource base."