Effects of growing roots of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) on rhizosphere soil solution chemistry

The chemical conditions of the rhizosphere can be very different from that of bulk soil. Up to now, little attention has been given to the problem of spatial heterogeneity and temporal dynamics of rhizosphere soil solution an d little is known about the influence of different tree species on rhizosph ere chemistry. In the present study, we used micro suction cups to collect soil solution from the rhizosphere of Norway spruce (Picea abies [L.] Karst .) and European beech (Fagus sylvatica L.) seedlings in high spatial resolu tion and capillary electrophoresis for the determination of major cations a nd anions. The results indicate, that in a soil with a base saturation of a bout 20-25% and a pH of 6.5, growing roots of beech and spruce lower the co ncentrations of nutrient cations and nitrate in the rhizosphere soil soluti on and decrease significantly the pH. The H+ release leads to an enhanced m ineral weathering as indicated by an increase of CEC and base saturation an d to a mobilization of soluble Al, however, on a very low concentration lev el. In our experiment rhizosphere effects of spruce have been more pronounc ed than those of beech, indicating, that with respect to below ground activ ity young spruce trees have a better competitive power than beech.