MULTIPLE PROCESSES IN THE FORMATION OF SUBARCTIC PODZOLS IN GREENLAND

Abstract

Three Podzols in subarctic southern Greenland have been studied with special emphasis on the chemical composition of cutans in B horizons. Energy dispersive X-ray techniques were used for chemical analysis of thin sections of B horizons. Cutan material of different kinds were found, whose distribution evidenced a general sequence of pedogenetic translocation processes in subarctic Podzols but also provided a better understanding of variations within the group of podzolized soils, especially as regards B horizon characteristics. Silicon, and in some soils phosphate materials also, dominate the cutan material in the central part of aggregates in B horizons, which indicates that early stages of translocation primarily involve these elements. At later stages, as indicated by the chemical composition of cutans in still more outer shells of aggregates, translocation processes also involve other chemical elements. Following the early stages, weathering processes in soils form inorganic Al-Fe silicate materials which, with increasing acidity in A horizons, are translocated into B horizons. The periodic, increasing activity of simple organic acids causes a shift from mostly inorganic translocation processes to a migration of metalorganic complexes. Upon reaching the B horizon, the translocated chemical compounds may change in composition due to degradation of organic complexant or may react with other reactive material already present in the horizon. This causes some remobilization of chemical elements in B horizons. The outermost shells of cutan material and structures of organic origin in B horizons are dominated by Al, Fe and organic matter. The amount of reactive organic matter, either translocated from A horizons, or formed in the B horizon by microbial activity, determines the character of late stages of Podzol B horizon formation.