This article explores the question under which conditions trees are managed in even- or uneven-aged stands or age class forests, respectively. The problem of uneven-aged management within stands and forests can be reduced to the analysis of simultaneous optimal times of harvest and regeneration of interdependently growing trees. Restricting attention to a market environment, a forest investment model is developed which accounts for the opportunity to manage trees or stands individually. As a consequence, age class forests evolve as the optimal compromise between two opposing effects. They allow for a combination of the advantages of uneven-aged management by utilizing differences in tree growth on a larger scale and of even-aged management by exploiting locally effective positive inter-tree dependencies on a smaller scale. Accordingly, the emergence of the forest structure is determined by the dynamics in the balance of value growth and impact rate differences.