Disturbance and Ecosystems: Components of Response (Ecological Studies)

The earth's landscapes are being increasingly impacted by the activities of man. Unfortunately, we do not have a full understanding of the consequences of these disturbances on the earth's productive capacity. This problem was addressed by a group of French and U.S. ecologists who are specialists at levels of integration extending from genetics to the biosphere at a meeting at Stanford, California, sponsored by the National Science Foundation and the Centre National de la Recherche Scientifique. With a few important exceptions it was found at this meeting that most man-induced disturbances of ecosystems can be viewed as large­ scale patterns of disturbances that have occurred, generally on a small scale, in ecosystems through evolutionary time. Man has induced dramatic large-scale changes in the environment which must be viewed at the biosphere level. Acid deposition and CO increase are two 2 examples of the consequences of man's increased utilization of fossil fuels. It is a matter of considerable concern that we cannot yet fully predict the ecological consequences of these environmental changes. Such problems must be addressed at the international level, yet substantive mechanisms to do this are not available.

Section 1 Biosphere.- 1.1 The Blue Planet: of Wholes and Parts and Man.- 1.1.1 Introduction.- 1.1.2 The CO2 Problem.- 1.1.3 Toxification.- 1.1.4 The Effects: Biotic Impoverishment.- 1.1.5 Conclusions.- Résumé.- References.- Section 2 Landscape.- 2.1 Landscape Modification and Changing Ecological Characteristics.- 2.1.1 Ecosystems and Landscapes.- 2.1.2 Some Ecological Attributes for Comparing Landscapes.- 2.1.2.1 Horizontal Structure.- 2.1.2.2 Stability.- 2.1.2.3 Thermodynamic Characterization.- 2.1.2.4 Chorology.- 2.1.2.5 Minimal Area (or Grain).- 2.1.2.6 Nutrient Cycling.- 2.1.2.7 Net Production.- 2.1.2.8 Tactics.- 2.1.2.9 Phylogeny.- 2.1.2.10 Type of Resistance.- 2.1.2.11 Conclusion.- 2.1.3 Disturbance Regimes.- 2.1.4 Effect on Landscape Patch Structure.- 2.1.4.1 Patch Origins.- 2.1.4.2 Patch Size.- 2.1.4.3 Patch Shape.- 2.1.4.4 Patch Numbers and Configuration.- 2.1.4.5 Summary for Patch Trends.- 2.1.5 Effect of Linkage Characteristics of the Landscape.- 2.1.5.1 Line Corridors.- 2.1.5.2 Strip Corridors.- 2.1.5.3 Stream Corridors.- 2.1.5.4 Networks.- 2.1.5.5 Habitations.- 2.1.5.6 Matrix.- 2.1.5.7 Summary of Trends for Linkage Characteristics.- 2.1.6 Conclusions.- Résumé.- References.- 2.2 Ecological Modeling of Landscape Dynamics.- 2.2.1 Introduction.- 2.2.2 Approaches to Modeling Landscape Dynamics.- 2.2.3 A Differential Equation Model of Landscape Change.- 2.2.4 Complex Digital Computer Model of Forest Dynamics.- 2.2.5 Evaluating the Impact of Regional Scale Problems on Localized Stands.- 2.2.6 Evaluating Impact of Regional Scale Problems Across Landscapes.- 2.2.7 Future Directions in Simulation Analysis of Landscapes.- 2.2.8 Conclusions.- Résumé.- References.- Section 3 Ecosystem Functions.- 3.1 Research on the Characteristics of Energy Flows within Natural and Man-Altered Ecosystems.- 3.1.1 Introduction.- 3.1.2 Examples of Energy Flows in Selected Ecosystems.- 3.1.3 Primary Production.- 3.1.3.1 Effect of Rejuvenating Forest Stands.- 3.1.3.2 Effect of Cutting on the Production of Grasslands.- 3.1.3.3 Effect of Grazing.- 3.1.3.4 Effects of Fire on Grasslands.- 3.1.3.5 Destruction and Transformation of Wooded Areas.- 3.1.4 Diversity of Energy Flows in Animal Populations.- 3.1.4.1 A/I Assimilation Efficiency.- 3.1.4.2 P/A Tissue Growth Efficiency.- 3.1.4.3 P/I Ecological Efficiency.- 3.1.4.4 Possibility of Changing the Energy-use Efficiency at the Individual Level.- 3.1.4.5 Possibility of Changing the Energy-use Efficiency of Populations.- 3.1.5 Conclusions.- Résumé.- References.- 3.2 “Natural” Mixed Forests and “Artificial” Monospecific Forests.- 3.2.1 Introduction.- 3.2.2 Advantages of Mixed Forests.- 3.2.3 The Yield of Mixtures.- 3.2.4 Economic Considerations.- 3.2.5 Conclusions ― Research on Mixed Forests.- Résumé.- References.- 3.3 Disturbance and Basic Properties of Ecosystem Energetics.- 3.3.1 Introduction.- 3.3.2 Biomass and Energy Flow in Infrequently Disturbed Ecosystems.- 3.3.2.1 Net Primary Production and Energy Flow Pathways.- 3.3.2.2 Biomass and Detritus Accumulation.- 3.3.2.3 Net Ecosystem Production.- 3.3.2.4 Variation in Infrequent Disturbance Events.- 3.3.3 Biomass and Energy Flow in Multiple Disturbance Ecosystems.- 3.3.3.1 Constant Species Composition and Site Quality.- 3.3.3.2 Changing Ecosystem Structure with Disturbance Frequency.- 3.3.4 Conclusions: Integration.- Résumé.- References.- 3.4 Ecosystem Water Balance.- 3.4.1 Basic Concepts.- 3.4.1.1 Water Budgeting.- 3.4.1.2 Energy Budgeting.- 3.4.1.3 Practical Limitations.- 3.4.2 Ecosystem Influences.- 3.4.2.1 Gross Precipitations.- 3.4.2.2 Evaporation Losses.- 3.4.2.3 Discharge Losses.- 3.4.3 Human Influences.- 3.4.3.1 Major Disturbances.- 3.4.3.2 Flow Regimes.- 3.4.3.3 Miscellaneous Influences.- 3.4.4 Conclusions.- Résumé.- References.- 3.5 Some Problems of Disturbance on the Nutrient Cycling in Ecosystems.- 3.5.1 Introduction.- 3.5.2 Fire.- 3.5.3 Reforestation by Conifers.- 3.5.4 Forest Fertilization.- 3.5.5 Removal of Forest Products.- 3.5.6 The Mineral Budget and Plant Succession.- 3.5.7 Conclusions.- Résumé.- References.- 3.6 Mechanisms of Ion Leaching in Natural and Managed Ecosystems.- 3 6.1 Introduction.- 3.6.2 Leaching of Anions and Cations.- 3.6.2.1 Measurement of Leaching Losses.- 3.6.2.2 Leaching Mechanisms ― Anion Mobility.- 3.6.2.3 The Major Anions.- 3.6.2.4 Effects of Management Practices on Nitrate Fluxes.- 3.6.2.5 Leaching Losses in Other Biomes.- 3.6.3 Conclusions.- Résumé.- References.- Section 4 Species Physiological Characteristics.- 4.1 The Determinants of Plant Productivity ― Natural Versus Man-Modified Communities.- 4.1.1 Introduction.- 4.1.2 Comparisons of Productivity.- 4.1.3 The Components of Plant Productivity.- 4.1.3.1 The Biotic Component.- 4.1.3.2 Environmental Influences on the Biological Components of Productivity.- 4.1.3.3 Interactions of Productivity Components and Resource Level in Natural Communities.- 4.1.4 Succession and Plant Productivity.- 4.1.5 Succession Anomalies.- 4.1.6 Convergence in Productivity.- 4.1.7 Agricultural Versus Natural Community Productivity.- 4.1.8 Conclusions.- Résumé.- References.- 4.2 Plant Growth and Its Limitations in Crops and Natural Communities.- 4.2.1 Introduction.- 4.2.2 Plant Growth Parameters.- 4.2.2.1 Photosynthesis.- 4.2.2.2 Respiration.- 4.2.2.3 Other Growth Processes.- 4.2.3 Comparison of Cultivated and Wild Species.- 4.2.3.1 The Case of Wheat.- 4.2.3.2 Adaptation of Natural Species to a Given Level of Resources.- 4.2.4 Crops Versus Natural Communities.- 4.2.5 Towards an Estimate in the Level of Available Resources.- 4.2.5.1 Light.- 4.2.5.2 Water.- 4.2.5.3 Nutrients.- 4.2.6 Conclusions.- Résumé.- References.- 4.3 Patterns of Nutrient Absorption and Use by Plants from Natural and Man-Modified Environments.- 4.3.1 Introduction.- 4.3.2 General Patterns and Nutrient Use.- 4.3.3 Successional Changes in Nutrient Use.- 4.3.4 Nutritional Patterns Related to Disturbance.- 4.3.4.1 Abandoned Fields.- 4.3.4.2 Post-Fire Succession.- 4.3.4.3 Tundra Disturbance.- 4.3.4.4 Disturbances Causing Reduced Nutrient Availability.- 4.3.5 Conclusions.- Résumé.- References.- 4.4 Comparisons of Water Balance Characteristics of Plant Species in “Natural” Versus Modified Ecosystems.- 4.4.1 Introduction.- 4.4.2 Theoretical Background.- 4.4.2.1 Heat and Water Exchange Processes.- 4.4.2.2 Water Availability and Plant Characteristics.- 4.4.3 Survey of Plant Characteristics.- 4.4.3.1 General Relations.- 4.4.3.2 Factors and Processes Affecting Water Loss.- 4.4.3.3 Factors and Processes Affecting Water Uptake.- 4.4.3.4 State of Water in the Plant.- 4.4.3.5 Growth and Death in Relation to Plant Water Content.- 4.4.4 Theoretical Considerations Relating Plant Characteristics and Successional State.- 4.4.4.1 Water Availability and Vegetative Recivery in the Semiarid Mediterranean Regions of Southern California.- 4.4.5 Conclusions.- Résumé.- References.- Section 5 Population Characteristics.- 5.1 Reproductive Strategies and Disturbance by Man.- 5.1.1 Introduction.- 5.1.2 Chemical and Sexual Polymorphism in Thyme.- 5.1.2.1 Sexual Polymorphism.- 5.1.2.2 Chemical Polymorphism.- 5.1.2.3 Environment and Population Genetic Structure.- 5.1.3 Enzymatic Polymorphism in Orchard Grass.- 5.1.4 Conclusions.- Résumé.- References.- 5.2 Demographic Strategies and Originating Environment.- 5.2.1 Introduction.- 5.2.2 Description of the Originating Environments.- 5.2.3 Between and Within-Population Variations of Strategies in Arrhenatherum elatius.- 5.2.4 Between and Within-Population Variations of Strategies in D. glomerata.- 5.2.5 Conclusions.- References.- 5.3 Genetic Characteristic of Populations.- 5.3.1 Introduction.- 5.3.2 Population Studies in Avena spp.- 5.3.3 Rose Clover, a Case History of Recent Colonization.- 5.3.4 Population Dynamics of Species in a Coastal Grassland Ecosystem.- 5.3.5 Variation and Colonization Success of Crop-Weed Hybrids.- 5.3.6 Alternative Strategies of Colonizing Success.- 5.3.7 Evolutionary Genetics of Adaptive Responses.- 5.3.8 Recombination Properties of Genetic Systems.- 5.3.9 Interspecific Interactions in Community Dynamics.- 5.3.10 Conclusions.- Résumé.- References.- 5.4 Characteristics of Populations in Relation to Disturbance in Natural and Man-Modified Ecosystems.- 5.4.1 Introduction.- 5.4.2 The Nature of Disturbance.- 5.4.3 Disturbance Characteristic with Relevance to Population Response.- 5.4.3.1 Size.- 5.4.3.2 Frequency of Occurrence.- 5.4.3.3 Intensity.- 5.4.3.4 Time of Disturbance.- 5.4.3.5 Level of Environmental Heterogeneity.- 5.4.3.6 Nature of the Biologic Neighborhood.- 5.4.4 Population Characteristics Responsive to Disturbance.- 5.4.4.1 Density, Dispersion and Age Structure.- 5.4.4.2 Genotypic Variability in Populations.- 5.4.4.3 Interactions Between Species.- 5.4.5 Life History Characteristics and Disturbance.- 5.4.5.1 Life Span.- 5.4.5.2 Reproductive Strategies.- 5.4.5.3 Germination, Growth and Response Breadth.- 5.4.6 Conclusions.- Résumé.- References.