INVESTIGATIONS OF SOME SOILS DEVELOPED IN HUMMOCKS OF THE CANADIAN SUB-ARCTIC AND SOUTHERN-ARCTIC REGIONS 1. MORPHOLOGY AND MICROMORPHOLOGY

Abstract

Investigations of Sub-Arctic and Arctic soils developed in moderately well drained mineral hummocks within the Interior Plains of the Canadian Mainland show them to be weakly differentiated in terms of morphological criteria. Interpretation of microfabrics, however, suggests three major active processes: organic matter accumulation, faunal activity and physical processes due mainly to freezing and thawing. To classify these microfabrics according to their important distinguishing characteristics, new concepts have been devised and some additional nomenclature is proposed. Broadly, the four soils are similar morphologically and genetically. They are characterized by a surface accumulation of plant fragments and in situ decomposition aided by small organic-ingesting fauna, overlying a zone at a few centimeters' depth in which virtually all the soil material has been worked by soil-ingesting fauna with accumulation of plant fragments still important. With increasing depth, both organic accumulation and faunal activity decrease rapidly, giving way to fabrics that probably result from freezing and thawing. In one of the soils there is evidence of significant translocation and/or concentration of specific constituents of the plasma. There is some evidence in two of the profiles that a zone of organic accumulation immediately overlying the ground ice is a buried stratigraphic unit, but pedoturbation may be a further cause of incorporation of decomposed plant fragments in the material throughout some of the profiles.