Factors contributing to forest decline in northwestern Switzerland.

Possible causes of decline of 37 beech (Fagus sylvatica L.) forests in northwestern Switzerland were investigated. The trees were assessed for symptoms of damage or disease including loss of leaves, chlorosis and dead shoots. In addition, nutrients and pollutants were analyzed in soil, leaves, stemflow and rainwater. Air pollutants were monitored at several sites. The results indicate that a variety of factors may have contributed to forest decline.