From 1997 to 2001 the Forestry Section at the BOKU University of Natural Resources and Applied Life Sciences in Vienna, Austria studied forest ecosystem restoration processes in an interdisciplinary research program. The need of forest restoration was noticed during the early 1980s. when researches emphasized that symptoms of forest decline can be considered as a mixed effect of both air pollution and historical changes in land use. We concentrated on secondary Norway spruce (Picea abies L. Karst.) stands on sites naturally dominated by broadleaves. Eleven discipline oriented working groups, ranging from eco-physiology, soil science, wild life ecology, and growth and yield, to socio-economics were linked. Some highlights of the results are presented to show the value of the integrated approach: The chain of blue stain fungi infection, decreased sap wood flow, release of volatiles of different mono-terpenes and bark beetle attraction was revealed. The dependence of shoot blight symptoms of Norway spruce, infected by Sirococcus conigenus on tree nutrition was clarified. The relationships between soil water conditions, transpiration behavior, rooting depth and growth of Norway spruce and beech in pure and mixed stands were explained. Through restoration processes the changes in forest regeneration, stand density and forage cover were modeled in order to describe their effect on roe deer habitat quality. Finally the way how these findings might find their way into forestry practices was studied and found to be most successful by personal communication.