Relationships between geochemistry of basal till and chemistry of surface soil at forested sites in Finland

Concentrations of several elements extractable with BaCl2 and acid ammonium acetate (pH 4.65) were measured in the organic and 4 mineral soil layers o n the national forest inventory plots of the Finnish Forest Research Instit ute, The soil data also includes total concentrations of elements in the or ganic layer and site and soil physical characteristics. Data were compared with the aqua regia extractable element concentrations measured in the nati onwide regional till geochemical mapping carried out by the Geological Surv ey of Finland. Correlations between concentrations in surface soil and underlying basal ti ll were generally highest for K, Mg, Mn. P and Zn, in the organic layer and till they were highest for Cr and Cu. The strength of these correlations d id not increase regularly from surface to deeper soil layers. All soil base cations with the exception of Ca, which is of relatively low solubility, w ere well correlated. The elements Zn, K, P, Al and Mn in till were the most reliable indicators of surface soil chemistry, Fuzzy clustering showed that the correlation between element concentrations ill basal till and the two uppermost layers of mineral soil was better wit hin areas of distinct till geochemistry, such as the schist belts in southw estern Finland. the Lake Ladoga-Bothnian Bay zone and the Kuusamo schist be lt. Surface soil chemical variables were clearly better in discriminating ferti lity classes of forest sites than were element concentrations in basal till . The independent ability of till geochemistry to distinguish these product ivity classes and to explain surface soil fertility was nevertheless demons trated. (C) 2000 Elsevier Science Ltd. All rights reserved.