STUDY OF CURRENT SOIL-FORMING PROCESSES USING BAGS OF VERMICULITE AND RESINS PLACED WITHIN SOIL HORIZONS

We have tested an in situ experimental method in which a cationic exchange resin, a chelating resin and a test-mineral (vermiculite) were placed in permeable bags and inserted into various soil horizons. Later, the bags were removed and the contents analysed to characterize the currently active geochemical processes in forest acid soils (Humods, Orthods, Ultisols, Oxisols, Dystrochrepts). Two main geochemical and soil-forming processes were distinguished: simple acidolysis and acidocomplexolysis (podzolization) involving complexing organic acids. Simple acidolysis was revealed by the transformation of the test-mineral into an intergrade hydroxy-Al vermiculite, whereas adsorption of Al or Fe on the chelating resin was indicative of the presence of Al-or Fe-organic complexes, which is typical of podzolization. The processes observed in the in situ experiment varied from being completely consistent with the observed soil morphology to showing major inconsistencies with it. The active phase of acidocomplexolysis characteristic of podzolization was found to be active although the morphological results of that process was only slightly developed in the soil morphology. Conversely, although a strongly expressed spodic morphology was found, it was not accompanied by a currently active acidocomplexolysis process. Thus the spodic horizon appeared to be a relict feature. Seasonal interruptions of podzolization were also revealed.