Soils over ultramafic rocks are usually described as rich in Fe and with high base content and saturation (especially Mg), with a pH value close to neutrality; these features retard the translocation of metallo-humic compounds, which is the key process of podzolization. 6 pedons, located in the ophiolitic area of Mont Avic Nat. Park (Ao, Italy), were sampled and analyzed in order to relate their spodic morphology to parent material lithology and vegetation cover (subalpine Pinus uncinata and Larix decidua forest); these soils were chosen between 56 previously observed profiles. The presence of a deeply bleached eluvial horizon overlying a brownish B horizon, the important increase in pyrophosphate and dithionite extractable Fe and, on mafic rocks, Al, shows the activity of the eluviation of organo-metallic compounds, which is the key process of podzolization; total Fe, Ni, Cr always have the highest content in the Bs horizons, evidencing a strong illuviation of these metals. The B horizons of P3, P4, P5, P6 (with a serpentinic parent material) have low acid oxalate extractable Al (Alo) and moderately high Fe (Feo) contents; thus, the spodic index required in the WRB (1998) and Soil Taxonomy (2003) is not reached, probably because of the low Al content in the silicate crystals of serpentine. Pyrophosphate and citrate dithionite extractable Fe and Al show a high content and a strong increase in the B horizons, compared to the overlying E. Thus, the spodic index required in the Canadian Soil Taxonomy (1985) and in the old USA Soil Taxonomy are reached. We can conclude that the podzolization process is active in soils developed on serpentine and mafic rocks, probably due to acidifying vegetation (Rhodoreto-Vaccinietum) and low temperatures; Podzols (WRB) and Spodosols (USDA) are found only where the ultramafic till is enriched in Al and Si coming from mafic rocks.

Podzolization on ophiolitic materials in Mont Avic Natural Park (Aosta, Italy) / M. D'Amico, F. Julitta, D. Cantelli. ((Intervento presentato al convegno Fifth International Conference on Serpentine Ecology : 9th - 13th May tenutosi a Siena nel 2006.

Podzolization on ophiolitic materials in Mont Avic Natural Park (Aosta, Italy)

M. D'Amico;
2006

Abstract

Soils over ultramafic rocks are usually described as rich in Fe and with high base content and saturation (especially Mg), with a pH value close to neutrality; these features retard the translocation of metallo-humic compounds, which is the key process of podzolization. 6 pedons, located in the ophiolitic area of Mont Avic Nat. Park (Ao, Italy), were sampled and analyzed in order to relate their spodic morphology to parent material lithology and vegetation cover (subalpine Pinus uncinata and Larix decidua forest); these soils were chosen between 56 previously observed profiles. The presence of a deeply bleached eluvial horizon overlying a brownish B horizon, the important increase in pyrophosphate and dithionite extractable Fe and, on mafic rocks, Al, shows the activity of the eluviation of organo-metallic compounds, which is the key process of podzolization; total Fe, Ni, Cr always have the highest content in the Bs horizons, evidencing a strong illuviation of these metals. The B horizons of P3, P4, P5, P6 (with a serpentinic parent material) have low acid oxalate extractable Al (Alo) and moderately high Fe (Feo) contents; thus, the spodic index required in the WRB (1998) and Soil Taxonomy (2003) is not reached, probably because of the low Al content in the silicate crystals of serpentine. Pyrophosphate and citrate dithionite extractable Fe and Al show a high content and a strong increase in the B horizons, compared to the overlying E. Thus, the spodic index required in the Canadian Soil Taxonomy (1985) and in the old USA Soil Taxonomy are reached. We can conclude that the podzolization process is active in soils developed on serpentine and mafic rocks, probably due to acidifying vegetation (Rhodoreto-Vaccinietum) and low temperatures; Podzols (WRB) and Spodosols (USDA) are found only where the ultramafic till is enriched in Al and Si coming from mafic rocks.
Settore AGR/14 - Pedologia
Podzolization on ophiolitic materials in Mont Avic Natural Park (Aosta, Italy) / M. D'Amico, F. Julitta, D. Cantelli. ((Intervento presentato al convegno Fifth International Conference on Serpentine Ecology : 9th - 13th May tenutosi a Siena nel 2006.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/874720
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