Comparison of the periodic mean annual increment of the mixed stands compared with the neighbouring pure stands. (a) Stem volume increment of Norway spruce in the mixed stand PAIV_sp,(be) over the respective growth in the pure stand PAIV_sp. (b) Relative periodic mean annual above ground dry mass increment MERW_sp,(be) of Norway spruce in mixed versus pure stand over mixing proportion (m_be). On average we find an underyielding of the mixed stands of –0.94 m³ ha⁻¹ y⁻¹; the relation amounts to 1.01 on average and indicates an overyielding of +1%. (c) Stem volume increment of European beech in the mixed stand PAIV_(sp),be over the respective growth in the pure stand PAIV_be. (d) Relative periodic mean annual above ground dry mass increment MERW_(sp),be of European beech in mixed versus pure stand over mixing proportion (m_sp). On average we find an overyielding of the mixed stands of +2.65 m³ ha⁻¹ y⁻¹; the relation amounts to 1.41 on average and indicates an overyielding of +41%.