Root distribution of Norway spruce in monospecific and mixed stands on different soils

Vertical root distribution was studied in pure Norway spruce (Picea abies (L.) Karst.) stands and in adjacent mixed stands of spruce and European beech (Fagus sylvatica L.) with comparable site conditions. The investigation was carried out in two regions of Austria with different bedrock material. One site was located on nutrient rich, poor-aerated stagnic cambisol, the other on nutrient poor, well-aerated podsolic cambisol. A modified trench profile wall technique was used to study the coarse root distribution on altogether 160 m(2) of profile walls. The fine root biomass was estimated using soil core cylinders. Coarse roots were more abundant on nutrient poor than on nutrient rich site. showing the greatest cross-section (CS-)area in the humus and upper mineral soil layer in all of the four investigated stands. No significant difference in total root CS-area was found between pure and mixed stand in both regions. Coarse roots of Norway spruce were markedly stronger limited to the upper soil layers in mixture with beech than in pure spruce stands. This limitation to the upper soil was especially pronounced for the mixed stand on stagnic cambisol. The fine root biomass was greater in spruce stand on nutrient poor, well-aerated soil than on stagnic soil, whereas the mixed stands did not differ. The fine root system of spruce was markedly shallower in stagnic than in podsolic cambisol in pure stands and, compared to the basal area, spruce fine roots were under-represented in the mixed stands on both soil types. Like the coarse roots, fine roots of spruce showed a clear shift towards the upper soil layers in mixture with beech. This shift towards a more superficially distributed root system of spruce in mixture with beech together with the under-represented fine root biomass of spruce in these stands indicates a higher belowground competitive ability of beech compared to spruce on both nutrient rich and nutrient poor sites. (C) 2002 Elsevier Science B.V. All rights reserved.