Controversies on the genesis and classification of permafrost-affected soils

The concept of permafrost-affected soils, described as Cryosols or Gelisols, has initiated a lively debate in the scientific literature that pertains to key issues in pedology, including the concept of soils, soil-forming factors and processes, and regional and global soil taxonomic systems. In this review paper, we offer explanations to justify the introduction of the Cryosol and Gelisol orders, particularly in view of the importance of permafrost in global-change scenarios. Our view is that Cryosols contain a cryic horizon or gelic materials resulting from cryogenic processes that include cryoturbation, ice segregation, or cryodesiccation in the presence of permafrost. These processes are pedogenic (i.e., cryopedogenic) and characteristic of permafrost-affected soils. Cryosols also are influenced by physical weathering, geochemical and biochemical weathering that occur at varying degrees. Cryosols are linked to the landscape by the presence of permafrost and the accompanying cryopedogenic processes, which attain dominance over other soil properties and processes in incorporating these soils into global taxonomic systems. We encourage further debate on the issue.