Saplings of Fagus sylvatica and Picea abies were grown in mono‐ and mixed cultures in a 2‐year phytotron study under all four combinations of ambient and elevated ozone (O 3 ) and carbon dioxide (CO 2 ) concentrations. The hypotheses tested were (1) that the competitiveness of beech rather than spruce is negatively affected by the exposure to enhanced O 3 concentrations, (2) spruce benefits from the increase of resource availa...