This book focuses on the recent decline of red spruce and the role of acid rain and associated air pollutants in this decline. The purpose of the book is to summarize a large body of recent research on this important environmental issue. The book is divided into 3 sections: Section I summarizes the features of spruce-fir forests in the Eastern U. S. and examines the ecology of the forests, their soils, and the atmospheric conditions experienced by these forests. Section II looks at experimental results from many air pollution studies and evaluates mechanisms of air pollution effects on red spruce trees. Section III synthesizes the current state of knowledge regarding the widespread red spruce decline in forests of the eastern United States.