Soil Formation of "Atlantic Rankers" from NW Spain—A High Resolution Aluminium and Iron Fractionation Study

Atlantic rankers belong to the group of ＂cryptopodzolic rankers＂, which are ubiquitous in the mountainous cool/temperate humid regions of Western Europe. The rankers of Galicia （NW Spain） formed by thousands of years of colluviation. The preponderance of Al-stabilised organic matter （OM） masks the horizonation and polycyclic character （i.e., stratification） of these soils. Cryptopodzolic rankers are generally thought to be the outcome of podzolisation. This soil type is part of the recent discussion on how to classify soils developed from nonvolcanic parent material having andic properties. To better understand the formation processes of these soils, the Al and Fe fractionation of four typical Atlantic rankers were studied by selective dissolution in acid NH4-oxalate, Na-pyrophosphate and the chlorides of K, La and Cu. A high-resolution sampling approach allowed us to investigate the soils in greater detail than simply sampling by horizon. The rankers studied display a distribution of Fe- and AI-OM complexes that is typical of cryptopodzolic soils. However, these organomineral associations were probably immobile due to the high Al saturation. We argue that the soils owe their characteristic chemical status to external factors rather than to translocation of organomineral associations： variations in AI-OM concentrations could be linked to changes in weathering/leaching intensity and colluviation rates caused by anthropogenic disturbances or changes in regional climate regime.

Atlantic rankers belong to the group of "cryptopodzolic rankers", which are ubiquitous in the mountainous cool/tempe-rate humid regions of Western Europe. The rankers of Galicia (NW Spain) formed by thousands of years of colluviation. The preponderance of Al-stabilised organic matter (OM) masks the horizonation and polycyclic character (i.e., stratifi-cation) of these soils. Cryptopodzolic rankers are generally thought to be the outcome of podzolisation. This soil type is part of the recent discussion on how to classify soils developed from nonvolcanic parent material having andic properties. To better understand the formation processes of these soils, the Al and Fe fractionation of four typical Atlantic rankers were studied by selective dissolution in acid NH4-oxalate, Na-pyrophosphate and the chlorides of K, La and Cu. A high-resolution sampling approach allowed us to investigate the soils in greater detail than simply sampling by horizon. The rankers studied display a distribution of Fe-and Al-OM complexes that is typical of cryptopodzolic soils. However, these organomineral associations were probably immobile due to the high Al saturation. We argue that the soils owe their characteristic chemical status to external factors rather than to translocation of organomineral associations: variations in Al-OM concentrations could be linked to changes in weathering/leaching intensity and colluviation rates caused by anthropogenic disturbances or changes in regional climate regime.