Nutrient fluxes in pure and mixed stands of spruce (Picea abies) and beech (Fagus sylvatica)

Studies on the combined effects of beech-spruce mixtures are very rare. Hence, forest nutrition (soil, foliage) and nutrient fluxes via litterfall, throughfall (+ stemflow) and soil solution were measured in adjacent stands of pure spruce, mixed spruce-beech and pure beech on a nutrient rich site at Kreisbach, as well as in adjacent spruce and mixed stands on a nutrient poor site at Frauschereck to evaluate the impact of tree species composition (spruce versus beech) on these parameters. The highest recorded throughfall (+ stemflow) fluxes were 22.4 kg N ha(-1) and 9.6 kg S ha(-1) yr(-1) and increased from beech over the mixed to the spruce stand at Kreisbach, but were similar for both stands at Frauschereck. At Frauschereck, atmospheric inputs were more or less reflected in element outputs, slightly modified by tree species composition. At Kreisbach, there was hardly any linkage between nutrient inputs and outputs. Our overall conclusion is that tree species composition affects forest nutrition, atmospheric input and consequently soil solution chemistry and input-output budgets of nutrients. However, these effects are site specific and dependent on the studied chemical element and process.