Surface podzolization in Cambisols under deciduous forest in the Belgian loess belt

Surface podzolization involves the migration of metal-humus complexes to a depth of a few centimetres. In acid soils derived from loess, this process has been diagnosed mainly by morphological observation. We investigated thi s process in a toposequence of Luvisols and Cambisols on loess using select ive extraction and mineralogical data as well as characteristics of the lea f litter. The humus type (O and OAh horizons) is a moder in the three Luvis ols and one of the Cambisols, whereas it is a fibrimor in the two other Cam bisols. The contents in total alkaline and alkaline-earth cations range fro m 35 to 60 cmol(c) kg(-1) in the fibrimor and from 40 to 90 cmol(c) kg(-1) in the moder humus. In the two Cambisols with fibrimor smectite occurs in t he clay fraction of the Ah horizon; Fe-humus complexes seem to have moved, but no more than 9 cm, from the Ah to the AB horizon beneath. Relative to t he Ah horizon, the upper part of the AB has larger tetraborate-extractable Fe/Al ratio and optical density of the oxalate extract. Such features conve rge to diagnose surface podzolization in the Cambisols with fibrimor. Howev er, they were not detected in the Cambisol and Luvisols with moder. In the two Cambisols with fibrimor, surface podzolization is consistent with (i) t heir smaller iron content, (ii) their more advanced weathering stage and (i ii) their lower acid neutralizing capacity.