The knowledge of the relationship between plant communities and soil types presents a valuable interpretation base for damage assessment. As expected, trees growing on unfavourable sites (e.g. on soils with impeded water) react more sensitively to secondary stress factors such as air pollutants than trees on suitable sites. With a declining nutrient supply in the series Elymo-Fagetum, Asperulo-Fagetum, Violo-Quercetum we recognize a corresponding increase of the damage level in the tree layer of these forest communities. However, ecological site parameters are not always sufficient for an explanation of the high damage level of some communities. It is supposed that a specific structure of these communities is responsible for a considerable proportion of severely damaged trees. Particular crown integration in the tree layer of forests and damage levels are closely connected. The influence of forest structure therefore masks the damage components affected by soil conditions. © 1990 Kluwer Academic Publishers.