Implications of Chronic Air Pollution in the San Bernardino Mountains for Forest Management and Future Research

Abstract

The research brought together in this book documents a history of chronic air pollution in the San Bernardino Mountains (SBM). The decline of ponderosa pine trees first noted in the 1950s was the result of exposure to ozone, a toxic component of photochemical smog (Miller and McBride, introduction to this volume). Tree mortality reached a peak during the drought years of the 1970s. Although air pollution levels dropped during the 1980s and early 1990s, foliar injury symptoms are still in evidence, and some tree mortality continues. A similar history is unfolding in other parts of the world where photochemical smog moves from urban and industrial areas into adjacent forests (De Lourdes De Bauer and Krupa 1990). Some areas, such as the pine and sacred fir forests in the mountains southwest of Mexico City, have already shown high levels of mortality similar to those in the SBM in the 1970s (McBride and Miller 1987). The objectives of this chapter are to review the information brought together in this book and the implications of that information for forest management and future research in the SBM.