MICROSCALE VARIATION OF SOLID-PHASE PROPERTIES AND SOIL SOLUTION CHEMISTRY IN A FOREST PODZOL AND ITS RELATION TO SOIL HORIZONS

In order to evaluate micro-scale heterogeneities 55 micro suction cups were placed in an array at 15 mm intervals in a profile face of a cam bic podzol. The chemistry of soil solution (mineral anions, pH. UV abs orption as a measure for DOC) was compared with solid-phase properties from soil samples (2 cm3 volume), which had surrounded the suction cu ps. Sequential extraction techniques (water, HN4Cl, hydroxylamin-hydro chloride, citrate-bicarbonate, oxalate, dithionite-citrate-bicarbonate ) and base titrations were applied to characterize the solid phase. Al though the average soil solution concentrations between horizons often differed significantly, the spatial distributions of pH and SO42- did not correlate with soil horizon borders. Even if concentration isolin es and soil horizon borders were parallel, marked concentration gradie nts could be observed within individual soil horizons. The less intens e the interaction between solute ion and soil matrix, the greater was the variation in solution concentration within a soil horizon. For the soil solid phase only a weak correlation of slow buffer reactions to soil horizons was found. The distribution of extractable Fe and Al was typical for a podzol profile, however, with very steep gradients with in single soil horizons. Except for pH, which was related mainly to ci trate-bicarbonate extractable aluminium, no solid-phase characteristic showed a clear correlation with soil solution chemistry.