Pedogenesis in the sorted patterned ground of Devon Plateau, Devon Island, Nunavut, Canada

摘要

In the High Arctic, the barren expanses of Devon Plateau, Devon Island, are affected by intense frost action that conditions geomorphic processes at the landscape level, soil formation at the profile level, and the establishment and distribution of vascular plants at microsites. In the High Arctic, in areas of patterned ground, frost action is responsible for both the accumulation of parent material through the segregation of fines in features here called "islands of fines" and for the development ofsoil profiles through cryoturbation in these features. At the landscape level, segregation of fines results in the development of patterned ground, specifically in the formation of sorted stripes, sorted circles and plugs that repeat themselves on the landscape. Plugs consist of cylindrical to conical soil masses protruding from the frost/permafrost table in the stony areas that may coalesce to form island of fines. Cryoturbation, the dominant soil forming process, is manifested by the appearance of convoluted horizons, injection of material, up-heaving of stones and soil mixing. But there are also non-cryoturbated soils with A-B-C vertical sequences. We have described, sampled and analyzed the soils simultaneously present in the islands of fines. Also, we have examined the plugs, the stony areas and the stony borders. Non-cryoturbated soils, Typic Haplorthels or Brunosolic Eutric Static Cryosols, occurred at the edges of the sorted circles, once the injection of heaved material has subsided. They showed an A horizon grayish brown, relatively rich in carbon and nitrogen, sandier than the underlying B horizon, which is characterized by the presence of illuvial silt caps. The C horizon is low in organic carbon and nitrogen and poorly rooted. Despite wet conditions and impeded drainage, because of the high pH, low organic matter content and low biological activity, oxidation/reduction processes are not well expressed. C-horizon material injected from the frost/permafrost table penetrated into the bodyof the island of fines, rupturing horizons and merging at the surface. These soils are Aquic Haploturbels or Gleysolic Turbic Cryosols. The major soil forming processes that are acting in the Haplorthels or Brunosolic Cryosols include: brunification, lessivage and decarbonation/carbonation. In the Aquic Haploturbels or Gleysolic Turbic Cryosols the processes are: cryoturbation, gleying and decarbonation/carbonation. Stony areas play the important role of trapping air-born dust that includes mineral andorganic components. Also autochthonous living organisms dwell in these block fields. The air-born mineral fines together with those left by the receding ice-cap and those produced by weathering aliment the formation of plugs, islands of fines and the sorted stripes.