The inclusion of forests as potential biological sinks in the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) in 1997 has attracted international attention and again has put scientific and political focus on the world's forests, regarding their state and development. The international discus­ sion induced by the Kyoto Protocol has clearly shown that not only the tropical rain forests are endangered by man's activities, but also that the forest ecosystems of boreal, temperate, mediterranean and subtropical regions have been drastically modified. Deforestation on a large scale, burning, over-exploitation, and the degra­ dation of the biological diversity are well-known symptoms in forests all over the world. This negative development happens in spite of the already existing knowledge of the benefits of forests on global energy and water regimes, the biogeochemical cycling of carbon and other elements as well as on the biological and cultural diversity. The reasons why man does not take care of forests properly are manifold and complex and there is no easy solution how to change the existing negative trends. One reason that makes it so difficult to assess the impacts of human activity on the future development of forests is the large time scale in which forests react, ranging from decades to centuries.

1 Introduction.- 2 Forest-Ecosystem Fundamentals.- 2.1 The Forest Ecosystem and Its Environment.- 2.2 Space and Time Seal es of Ecosystem Processes.- 2.3 Complexity and Order in Forest Ecosystems.- 2.3.1 Hierarchy Theory.- 2.3.2 Constraints by Higher Hierarchical Levels: Stability.- 2.3.3 Break of Hierarchy: Destabilisation.- 2.4 Process Patterns as Ecological Indicators.- 2.4.1 Buffering Properties of Soil.- 2.4.2 Element Content in Plant Organs and Litter.- 2.4.3 Humus Forms.- 2.4.4 Tree Architecture.- 2.4.5 Input/Output Budgets.- 2.4.6 Forest Structure.- 2.4.7 State Phases of Forest Ecosystems.- 2.5 Stabilising and Destabilising Effects.- 2.5.1 Site Requirements of Tree Species.- 2.5.2 Destabilising Effects.- 2.5.3 Stabilising Effects.- 3 Post-Glacial Development of Climate and Forest Ecosystems.- 3.1 Climate Development.- 3.1.1 Historical Climate Changes.- 3.1.2 Holocene Climate History.- 3.1.3 Twentieth-Century Climate Changes.- 3.2 Vegetation Development.- 3.2.1 General Limits of Forest Growth.- 3.2.2 Historical Patterns of Forest Growth.- 3.2.3 Late-Glacial Forest Emergence.- 3.2.4 Early-Holocene Forest Expansion.- 3.2.5 Middle/Late-Holocene Forest Development.- 3.2.6 The Human Influence.- 3.2.7 Properties and Migration Patterns of Central European Forest Taxa.- 3.3 Post-Glacial Changes in Nutrient Cycling and Soil Conditions.- 4 Sources and Sinks of Greenhouse Gases and Air Pollutants.- 4.1 Overview.- 4.1.1 Controls of Climate Development.- 4.1.2 The Greenhouse Effect.- 4.1.3 Other Atmospheric Perturbations.- 4.2 Carbon Compounds.- 4.2.1 Carbon Reserves and Carbon Cycling.- 4.2.2 Wood-Related Carbon Reserves.- 4.2.3 Carbon Reserves of the Forested Systems.- 4.2.4 Carbon Dioxide.- 4.2.5 Carbon Monoxide.- 4.2.6 Methane.- 4.2.7 Halocarbons.- 4.2.8 Volatile Organic Compounds.- 4.3 Nitrogen and Sulphur Compounds, and 03.- 4.3.1 Nitrogen Compounds - an Overview.- 4.3.2 Nitrous Oxide.- 4.3.3 Ozone.- 4.3.4 Acidity: Nitrogen Oxides, NH3, S02.- 4.4 Heavy Metals.- 5 Present State of Forest Ecosystems.- 5.1 Introduction.- 5.2 Forest Soil Condition.- 5.2.1 Acid-Base Condition.- 5.2.2 Soil Organic-Matter Condition.- 5.2.3 Influence of Vegetation, Forest Type and Tree Species on Soil Organic-Matter Storage.- 5.3 Forest Vegetation Condition.- 5.3.1 Forest Area, Growing Stock and Increment.- 5.3.2 Biotic and Abiotic Influences on Timber Stocks and Forest Increments.- 5.3.3 Historical and Current Trends of Forest Damage and Decline.- 5.4 Overall Forest Carbon Reserves.- 6 Implications of Changes in Ambient and Climatic Conditions on Ecosystem Processes.- 6.1 Implications of the Deposition of Acid and Nitrogen.- 6.1.1 Effects of Acid Deposition on Leaves, Soil, Roots and Tree Nutrition.- 6.1.2 Effects on Decomposition.- 6.1.3 Effects on Crown Condition and Increment.- 6.1.4 Effects on Nutrient and Ion Cycles.- 6.1.5 Effects on Stand Development and Ecosystem Renewal.- 6.1.6 Effects on Genetics in Tree Populations.- 6.2 Implications of an Increase in the Atmospheric Carbon Dioxide Content.- 6.2.1 Atmospheric C02 Concentrations in Earth's History and Plant Developmental Responses.- 6.2.2 Plant Responses to C02 Enrichment.- 6.2.3 Interactions of Elevated C02 Levels with Other Growth Factors.- 6.2.4 Effects of Elevated C02 on Soils and Herbivores.- 6.2.5 Ecosystem Responses to Elevated C02.- 6.3 Additional Effects of an Increase in Temperature.- 6.3.1 Immediate Responses to Temperature Changes.- 6.3.2 Response of Seasonal Ecosystem Processes to Temperature and Its Change.- 6.3.3 Responses of Annual Processes and Element Cycling to Temperature Changes.- 6.3.4 Temperature Response of Processes at Higher Scales.- 6.4 Implications of Climatic Changes on the Water Balance.- 6.4.1 Introduction.- 6.4.2 Water Regulation in Plants and Soil.- 6.4.3 Water Relationships at the Ecosystem Level.- 6.4.4 Effects on the Regional Water Balance.- 6.5 Implications of Catastrophic Weather Incidents.- 6.5.1 Introduction.- 6.5.2 Storms.- 6.5.3 Forest Fires.- 6.5.4 Floods.- 6.6 Implications of Increased UV-B Radiation.- 6.6.1 Introduction.- 6.6.2 General Aspects of UV Radiation.- 6.6.3 UV-B Effects on the Plant-Ecophysiological Level.- 6.6.4 UV-B Effects on Herbivores, Pests and Diseases.- 6.6.5 UV-B Effects on Plant Growth.- 6.6.6 UV-B Effects on Ecosystem Development.- 7 Scenarios of Future Changes.- 7.1 Expected Climate Changes.- 7.1.1 Methods of Climate-Evolution Research.- 7.1.2 Temperature.- 7.1.3 Precipitation.- 7.1.4 Other Climatic Parameters.- 7.1.5 Extreme Weather Events.- 7.1.6 Chemical Climate: Critical Levels and Critical Loads of Air Pollutants.- 7.1.7 Climate Feedback from Forests.- 7.2 Expected Soil Changes.- 7.2.1 Soil Moisture.- 7.2.2 Nutrient Status.- 7.3 Modelling Vegetation and Its Development Under Changing Conditions.- 7.3.1 Essentials and Approaches of Environmental Impact Modelling.- 7.3.2 Principal Outcomes of Bioclimatic Model Simulations.- 7.4 Expected Development of Forest Area and Wood Resources.- 7.4.1 Forest Area.- 7.4.2 Forest Growing Stocks.- 7.4.3 Forest-Product Consumption and Needs.- 7.5 Forestry Options for C02 Mitigation.- 7.5.1 General Influences of Forestry on Terrestrial Carbon Reserves.- 7.5.2 Management for Biosystem Carbon Conservation.- 7.5.3 Forestation.- 7.5.4 Management for Fossil-Carbon Substitution.- 7.5.5 Forest-Soil Features.- 7.5.6 Forest-Biomass Features.- 7.6 Trends of Change in Common Forest Ecosystem Types of Central Europe.- 7.6.1 European-Beech Forests.- 7.6.2 Norway Spruce Forests.- 7.6.3 Scots-Pine Forests.- 7.6.4 Mountain-Forest Ecosystems.- 7.6.5 Aspects of Biological Diversity and Adaptation in the Forest Ecosystems.- 8 Forest Management.- 8.1 Introduction.- 8.2 Development of Forest Management in Central Europe.- 8.3 Forest-Management Practices.- 8.3.1 Stand Establishment.- 8.3.2 Tending of Stands.- 8.4 Forest Practice and Management in a European Comparison.- 8.4.1 Stand Establishment.- 8.4.2 Tending of Stands.- 8.4.3 Forest-Protection Problems and Future Perspectives.- 8.4.4 Conclusions.- 8.5 Management Strategies to Cope with Forest Decline.- 8.5.1 Tree-Species Selection.- 8.5.2 Forest Breeding.- 8.5.3 Stand Establishment.- 8.5.4 Natural Regeneration.- 8.5.5 Supporting Treatments to Stabilise Site Conditions.- 8.5.6 Silvicultural Methods to Stabilise Forest Stands.- 8.5.7 Tending and Utilisation of Forest Stands.- 8.6 Forest-Management Reactions on Climate Warming.- 8.6.1 Afforestation Opportunities to Influence the Global Carbon Balance.- 8.6.2 Reactions to the Possible Increase in Extreme Climatic Events 4518.7 Arguments for a New Orientation of F…