Comparison of periodic mean annual increment of the mixed stands with neighbouring pure stands. Depicted is (a) the observed periodic mean annual volume increment PAIV_sp,be over the expected of stem volume of the mixed stand plots and (b) the relative periodic mean annual above ground dry mass increment over mixing proportion (m_be). On average the overyielding in stem volume growth of the mixed stands amount to +0.51 m³ ha⁻¹ y⁻¹; the relation amounts to 1.08 on average and indicates an overyielding of +8%.