Air Pollution and Forests: Interactions Between Air Contaminants and Forest Ecosystems

1. Introduction.- A. Air Pollution.- B. Forest Ecosystems.- C. Interactions between Air Pollutants and Forest Ecosystems.- References.- Section I. Forests Function as Sources and Sinks for Air Contaminants-Class I Interactions.- 2. Role of Forests in Major Element Cycles: Carbon, Sulfur, and Nitrogen.- A. Carbon Pollutants.- B. Sulfur Pollutants.- C. Nitrogen Pollutants.- D. Summary.- References.- 3. Forests as Sources of Hydrocarbons, Particulates, and Other Contaminants.- A. Volatile Hydrocarbons.- B. Particulates.- C. Forest Fires.- D. Summary.- References.- 4. Forests as Sinks for Air Contaminants: Soil Compartment.- A. Forest Soils as Particulate Sinks.- B. Forest Soils as Sinks for Atmospheric Gases.- C. Summary.- References.- 5. Forests as Sinks for Air Contaminants: Vegetative Compartment.- A. Forest Vegetation as a Sink for Particulate Contaminants.- B. Forest Vegetation as a Sink for Gaseous Contaminants.- C. Summary.- References.- 6. Class I Summary: Relative Importance of Forest Source and Sink Strength and Some Potential Consequences of These Functions.- A. Forests as Sources of Air Pollutants.- B. Forests as Sinks for Air Pollutants.- References.- Section II. Forests are Influenced by Air Contaminants in a Subtle Manner - Class II Interactions.- 7. Forest Tree Reproduction: Influence of Air Pollutants.- A. Pollen Production and Function.- B. Flower, Cone and Seed Production.- C. Seedling Development.- D. Summary.- References.- 8. Forest Nutrient Cycling: Influence of Trace Metal Pollutants.- A. Organisms Involved in the Decomposition Process.- B. Measurement of Organic Matter Decomposition Rate and Microbial Biomass.- C. Trace Metal Influence on Litter Decomposition.- D. Trace Metal Impact on Soil Processes.- E. Trace Metal Influence on Soil Enzymes.- F. Summary.- References.- 9. Forest Nutrient Cycling: Influence of Acid Precipitation.- A. Acid Precipitation and Vegetative Leaching.- B. Acid Precipitation and Soil Leaching.- C. Acid Precipitation and Soil Weathering.- D. Summary.- References.- 10. Forest Nutrient Cycling: Influence of Air Pollutants on Symbiotic Microorganisms.- A. Fungal Symbionts.- B. Bacterial Symbionts.- C. Other Nitrogen-Fixing Organisms.- D. Summary.- References.- 11. Forest Metabolism: Influence of Air Contaminants on Photosynthesis and Respiration.- A. Constraints on Photosynthesis.- B. Photosynthetic Suppression: Nonwoody Species.- C. Photosynthetic Suppression: Forest Tree Seedlings.- D. Photosynthetic Suppression: Forest Tree Saplings.- E. Photosynthetic Suppression: Large Forest Trees.- F. Photosynthetic Response to Air Contaminants: Mechanisms of Suppression.- G. Summary.- References.- 12. Forest Stress: Influence of Air Pollutants on Phytophagous Forest Insects.- A. Sulfur Dioxide.- B. Ozone.- C. Fluoride.- D. Trace Metals.- E. Other Air Pollutants.- F. Summary.- References.- 13. Forest Stress: Influence of Air Pollutants on Disease Caused by Microbial Pathogens.- A. Sulfur Dioxide.- B. Ozone.- C. Fluoride.- D. Particulates.- E. Other Air Contaminants.- F. Summary.- References.- 14. Forest Stress: Symptomatic Foliar Damage Caused by Air Contaminants.- A. Limitations on Generalizations Concerning Direct Air Pollutant Influence on Trees.- B. Sulfur Dioxide.- C. Nitrogen Oxides.- D. Ozone.- E. Peroxyacetylnitrate.- F. Fluoride.- G. Trace Metals.- H. Other Air Contaminants.- I. Summary.- References.- 15. Class II Summary: Forest Responds by Exhibiting Alterations in Growth, Biomass, Species Composition, Disease, and Insect Outbreaks.- A. Forest Growth Reduction Caused by Air Pollution.- B. Altered Succession and Species Composition.- C. Altered Forest Pest Influence.- D. Case Study: Response of a Forest Ecosystem to Air Pollution.- E. Summary.- References.- Section III Forest Ecosystems are Influenced by Air Contaminants in a Dramatic Manner-Class III Interactions.- 16. Forest Ecosystem Destruction: A Localized Response to Excessive Air Pollution.- A. Sulfur Dioxide.- B. Fluorides.