Soil Formation Along the N.America Bioclimate Subzone Transect.

The arctic region is characterized by cold ambient temperature, a short growing season and the presence of permafrost. The climate factor limits the biomass production and the decomposition rate in addition to other biogeochemical processes in the soil. The Arctic North American is divided into 5 bioclimate zones based on vegetation cover and ambient temperature. There is increased cover by vesicular plants and mosses from around 5% in subzone A to nearly 100% in subzone E. The mean July temperature ranges from 0-5C in subzone A to 9-12C in subzone E. Frost heave due to thermal expansion and contraction causes churning of the soil  that results in cryoturbated soils and redistribution of soil organic carbon (SOC) and other nutrients in the soil. There is increased dominance of nonsorted circles from subzone A to E due to the combined effects of vegetation cover and temperature.  SOC stores increase from Subzone A to E, as the result of biomass production reflecting the effects of biological control following the climate gradient. The permafrost table perches water during the growing season thus creates a saturated zone above the permafrost and results in reduced condition. However, such saturated and reducing conditions are regulated by the topographic positions; landform controls hydrology that intern affects the rate of organic matter accumulation. In the Arctic the changes in pH values does not normally follow the climate gradient, indicating the strong influence of parent material on soil chemistry due to weak weathering. Cation exchange capacity is strongly correlated with %OC but not with % clay indicating that soil organic matter controls the exchange sites and the clays have low exchange capacity mostly due to their low-degree of weathering in the cold climate.  In summary, climate, especially temperature, plays an overall controlling role in soil formation in the Arctic.