22 J. Brown et al. 



ments as a result of the thaw lake cycle or in some cases by frost heaving 

 (Tedrow 1977). The surface horizon and mottling within the mineral hor- 

 izons are the product of the current soil-forming processes of organic 

 matter accumulation and gleization. 



Two soil orders are represented within the Biome research area: 

 Inceptisols, mineral soils with poorly differentiated horizons, and 

 Histosols, soils composed primarily of organic materials (Soil Survey 

 Staff 1975). Because of the high moisture, the Inceptisols are classified as 

 aquepts. Histosols are differentiated taxonomically into suborders re- 

 flecting the state of decomposition of their organic materials. Because all 

 the soils have a cold temperature regime the prefix Cry is added to each 

 subgroup name. The term Pergelic preceding the subgroup name indi- 

 cates the presence of permafrost. The term Histic indicates the peaty 

 character of the surface 25 cm. The areal distribution of the soils or soil 

 combinations is related to landscape units of the Biome research area 

 (Figure 1-11). Weakly leached soils (Pergelic Cryochrepts), represented 

 by the Arctic Brown Soil (Tedrow and Cantlon 1958), are present only on 

 coarser-textured deposits on primary land surfaces such as beach ridges 

 (Figure 1-3) and are not represented within the Biome research area. 



The soils, much like the vegetation, are arranged along a topo- 

 graphic gradient ranging from the relatively freely drained and weakly 

 leached Pergelic Cryochrepts (Arctic Brown Soils) to soils developed 

 under conditions of extreme wetness, such as some Pergelic and Histic 

 Pergelic Cryaquepts (Half Bog Soils). Intermediate and somewhat 

 better-drained elements of the topographic-moisture gradient also have 

 Histic Pergelic Cryaquepts and Pergelic Cryaquepts (Meadow Tundra 

 Soils) developed in association with weakly expressed low-centered poly- 

 gons and low relief high-centered polygons. 



Where the low-centered polygonal pattern is strongly developed, an 

 association of soils occurs that is closely related to the elements of that 

 pattern (Figure 1-9). Within the depressed polygon centers (basins), mod- 

 erately decomposed organic materials constitute Pergelic Cryohemists 

 (organic soils with more than 40 cm of organic materials — Histosols). On 

 the rims of low-centered polygons the soils may be Pergelic Cryosaprists 

 made up of highly decomposed organic materials, extensions of the basin 

 Cryohemists, elevated and oxidized as the polygon rim expanded in re- 

 sponse to ice wedge growth, or Pergelic Cryaquepts, little differentiated, 

 mottled mineral soil with widely ranging amounts of organic materials. 

 The latter are more common toward the troughs and show the effects of 

 ice wedge expansion by the disruption of their horizons and enmixing of 

 mineral and organic materials. 



Within the polygon troughs the soils may be Pergelic Cryaquepts, 

 composed of coarse, fibrous organic material overlying gray or mottled 

 materials. Where the fibrous organic material reaches a thickness of 25 



