Oxidant Air Pollution Impacts In The Montane Forests Of Southern California

This volume presents a body of research conducted over more than thirty years, including an intensive interdisciplinary five-year study begun in 1991. Chapters include studies of the relationships of biogeography and climate to the region's air pollution, the chemical and physiological mechanisms of ozone injury, as well as the impacts of nitrogen-containing pollutants and natural stresses on polluted forests.

This volume presents a body of research conducted over more than thirty years, including an intensive interdisciplinary five-year study begun in 1991. Chapters include studies of the relationships of biogeography and climate to the region's air pollution, the chemical and physiological mechanisms of ozone injury, as well as the impacts of nitrogen-containing pollutants and natural stresses on polluted forests.

The book contains information on geology, climate and vegetation of the Sierra Nevada with a special emphasis on air pollution effects on the mixed conifer forests. A history of the extent of air pollution effects on mixed conifer forests, especially ponderosa and Jeffrey pines is provided. The physiological basis for ozone-type injury development in ponderosa pine, a discussion of ozone uptake by plants at different levels of biological organization and the effects of air pollution and other stresses on mountain forests are discussed. A considerable portion of the book is dedicated to development of statistical models and maps of ambient ozone distribution in the Sierra Nevada based on the 1999 monitoring data with passive samplers. The implications of the methodological results, formulation and application of regional air quality models for integrated assessment of urban and wildland pollution and the need for functionally integrated models of ozone deposition to the Sierra Nevada forests are also discussed. Management and monitoring needs for improved long-term understanding air pollution effects on forest ecosystems, discussion of options for proper management of the air pollution affected forests, and comparison of monitoring and modelling of ozone and forest health status in the Sierra Nevada with similar efforts in mountains of North American and European mountain ranges are the focus of the later chapters of the book.

At present, roughly half of the world's population lives in urban centers. There are now more than 20 cities with a population of over 10 million inhabitants, compared to less than 5 about 50 years ago. This tendency toward urbanization is expected to continue, particularly in the developing world. A consequence of this growing trend is that millions of people are being exposed to harmful levels of urban air pollutants caused mainly by emissions from motor vehicles and from industrial and domestic activities involving the combustion of fossil fuels. The driving force for the design and implementation of emission control strate gies aimed at improving air quality has been the protection of the health of the population in urban centers. There are, however, other consequences of the pres ence of air pollutants besides the direct effect on human health. Reduced visibil ity, damage to monuments and buildings, and many other such consequences indirectly affect our quality of life. Another set of consequences involves damage to ecological systems. In fact, the nature of "photochemical smog" was first uncovered in the 1950s in connection with observations of its harmful effects on crops and plants in the vicinity of Los Angeles.

Insect and disease issues are often specific to the Mediterranean forest systems rather than shared with the temperate forests. In addition to the specific native insects and diseases, the forests are subject to the invasion of exotic species. The forests are also at risk from high degrees of human activity, including changing patterns of forest fires, land management activities, intensive plantation forestry using introduced timber species from other Mediterranean climate zones, and atmospheric deposition. Combined with elements of global climate change that may disproportionately affect Mediterranean climate systems, this creates a number of significant management issues that are unique to the Mediterranean forests. It is our goal that the information contained in this volume will contribute to understanding the unique aspects of Mediterranean forest systems and to protecting these critical resources.