HETEROGENEITY OF SOIL AND SOIL SOLUTION CHEMISTRY UNDER NORWAY SPRUCE (PICEA-ABIES KARST) AND EUROPEAN BEECH (FAGUS-SILVATICA L) AS INFLUENCED BY DISTANCE FROM THE STEM BASIS

The influence of the distance to the stem on the chemical properties of soil and soil solution were investigated in a mature European beech (Fagus silvatica L.) and a Norway spruce (Picea abies Karst.) stand by comparing areas close to stems with reference areas between stems. Under beech, significant changes of soil chemistry close to the stem were observed. Distance from the stem influenced the exchangeable K, Mg, Ca and Al, as well as soil pH. Ca/Al- and Mg/Al-ratios of the soil solution showed higher values at the base of the stem. A significant increase of K and NO3-N concentrations of the soil solution close to the stem was found. No significant differences of soil analyses from reference sites and the base of the stem were detectable in case of spruce. Only the soil solution chemistry of the spruce site showed distinct spatial patterns. A significant increase of Ca, K and NH4 concentrations was determined next to the stem, while the concentrations of NO3 were considerably decreased. These findings suggest that the spatial heterogeneity of soil and soil solution chemistry related to stem distance should be taken into account when establishing element budgets and when evaluating the nutrient resources and the risk of acid toxicity to tree roots.