Impact of Oxidant Air Pollutants on Forest Succession in the Mixed Conifer Forests of the San Bernardino Mountains

Abstract

Chronic air pollution is an anthropogenic disturbance that may be influencing plant succession in the San Bernardino Mountains. Westman (1979, 1981) suggested that air pollution induced successional changes that were occurring in the coastal sage scrub communities of southern California. Air pollution differentially affects the survival, growth, and reproduction of the species making up a plant community. These impacts influence the competitive relationships among the species. Our ability to predict successional changes and eventual steady-state communities under conditions of chronic oxidant air pollution has been limited by the relatively short period that ecologists have had to observe this phenomenon. We are also limited in our ability to predict how patterns of plant succession will change in the future once chronic air pollution has been eliminated. It is important that we grapple with these questions to understand the potential impacts of the current episode of air pollution on the forests of southern California. An understanding of these impacts can inform forest managers and conservation biologists of the need to develop management strategies for the protection of vulnerable species and vegetation types. The purpose of this chapter is to review the results of a study initiated in the 1970s to evaluate the long-term impact of chronic air pollution on succession in the mixed conifer forests of the San Bernardino Mountains.