Lateral podzolization in a sandstone catchment

A sandstone catchment of the cool, perhumid Black Forest, Germany, was stud ied with respect to podzolization processes on a landscape scale. Soil mapp ing along a steep slope (25%) revealed Spodosols with thick E-horizons comb ined with thin spodic horizons in the upper catchment area. Lowermost parts of the landscape showed thinnest E- and thickest Bhs-horizons. This catena ry trend was quantified by a non-linear increase of the "illuviation-eluvia tion ratio of podzolization" (IERpodzol). Soil texture, pedogenic oxides (F e-o, Fe-d, Al-o, Mn-d), pH (CaCl2), C-org, and mineralogical composition of the lay and medium sand fraction were determined in six representative ped ons. Chemical analysis matched morphology in that very low contents and mas s densities of Fe-o, Fe-d, Al-o, and Mn-d were found in upslope soils. The distal pedons were 2-5-fold higher in these elements. The catenary trends c orresponded to a downslope increase in pH as well as organic carbon in mine ral soils. Mineralogical analysis showed a decrease in feldspar weathering and an increase in hydroxy-interlayered vermiculites towards the downslope soils. The morphological, chemical, and mineralogical results led to the co nclusion of a process sequence of (i) an upslope mobilization and depletion of iron, manganese and aluminum ("E-Spodosols"), (ii) a lateral translocat ion (approximate to 30% of catchment discharge occurred as interflow), and (iii) a downslope immobilization resulting in a (relative or absolute) accu mulation of the translocated soil compounds ("Bs-Spodosols"). The immobiliz ation probably was controlled by an admixture of Fe- and base-richer rocks into the parent material downslope. The concept of lateral podzolization de veloped in a granite landscape was confirmed in the sandstone area studied. (C) 2001 Elsevier Science BN. Ail rights reserved.