Tolerance of Red Oak and American and European Beech Seedlings to Aluminum

The effect of aluminum (Al) on the growth of red oak ( Quercus rubra L.), American beech ( Fagus grandifolia Ehrh.), and European beech ( Fagus sylvatica L.) seedlings was studied in solution culture containing from 0 to 3000 µM Al at pH 4.0. Aluminum had no detrimental effect on biomass of shoots of red oak and American beech. Shoot biomass of European beech was significantly reduced by Al, with greater reductions measured for seedlings grown in lower ionic‐strength media. Root biomass of species did not decline with increasing Al, and actually increased in some Al treatments. Generally, Ca, Mg, and P tissue concentrations of leaves and roots decreased with increasing solution Al for all three species. Even at the lowest solution Al concentration, 500 µM , significant reductions relative to the controls were measured. Of the elements measured, P appeared to be the most strongly correlated with shoot biomass response, having r values of 0.87 and 0.98 for American beech and European beech, respectively. Results from these studies indicate that the risk of direct effects of toxic soil solution Al concentrations on growth of red oak and American beech seedlings is low. However, soil solution concentrations of 500 µM have been reported in Europe and these correspond to the Al level found to significantly reduce shoot biomass of European beech in this study.