European forests have changed due to human management, leading to shifts in tree species and age composition. This has increased wood production but also caused a loss of biodiversity and increased risks. Forest management affects site productivity by changing nutrient cycling and competition for resources. To ensure sustainable forest use, we need to deepen our understanding of how management impacts forest ecosystems and their environmental services. Forest ecosystems operate on different scales, with responses to disturbances ranging from short-term to centuries. The state of forest ecosystems today is influenced by past processes. Studying long-term dynamics and key processes can help improve our understanding and predictive modeling of forest ecosystems.