Przyrost miąższości drzewostanów mieszanych i litych: wyniki z wybranych stałych powierzchni badawczych w Europie Środkowej

This paper addresses the question of whether or not and to which extent two common tree species mixtures (Norway spruce – European beech; sessile and pedunculate oak – European beech) vary in volume growth from their monocultures. To this end, the results from selected long−term experimental plots located in Germany, Poland and Switzerland, with many of them under survey since the 1890's, were employed. We found than on average both type of mixtures exceeded volume growth in pure stands by almost 30%. The analysis at the species level showed than only a Norway spruce response to mixture was neutral on average, while other tree species were benefitted by mixture. An empirical derived model for mixed stand of oak and European beech disclosed that the interaction can range from facilitation and overyielding on poor sites, through the neutral response under mesotrophic conditions, up to underyielding on fertile sites triggered by competition.