Andosols in Germany—pedogenesis and properties

Abstract

Soils conforming to Andosols in the World Reference Base (WRB) of Soil Resources have not yet been recognised in Germany. The aims of this study were to (i) show whether some German soils developed in volcanic parent materials are Andosols, (ii) investigate their pedogenetic development and (iii) determine their local distribution. We selected a soil on Quaternary basalt in the Eifel region (the “Windsborn” profile), and a soil from the summit of the Tertiary basaltic stratovolcano Vogelsberg (the “Köhlerwald” profile) northwest of Frankfurt am Main. The Windsborn soil is classified as a Silic Andosol. Allophane contents are near 10%, and allophane globules were identified by transmission electron microscopy (TEM). By progressively constraining field parameters in GIS-generated maps, we found that Andosols in the Mosenberg chain are confined to a few isolated occurrences. The Köhlerwald profile in the Tertiary Vogelsberg is an acid, base-poor and strongly weathered Aluandic Luvisol. Metal–humus complexes are the dominant colloidal phase. In the topsoil, both Fe p and Al p are in excess of Fe o and Al o values. Our data suggest the presence of phases like hydroxy-Al (e.g. from Al-interlayers or poorly ordered gibbsite) and opaline silica that are easily attacked by the alkaline (pH 9.5–10.5) pyrophosphate extractant, but may be resistant to the acid (pH 3) oxalate procedure. We conclude that there are limited occurrences of silandic Andosols in the Eifel area, Germany. The Windsborn soil is in an early pedogenetic development stage, but pedogenesis in the Köhlerwald soil has advanced beyond the Andosol phase to the stage of clay translocation. Therefore the existence of aluandic Andosols in Germany seems possible, but remains to be proven.