Cryogenic disturbance and pedogenic lag effects as determined by the profile developmental index: The styggedalsbreen glacier chronosequence, Norway

A chronosequence with a terminal moraine dating to the mid-eighteenth century is found at the Norwegian glacier Styggedalsbreen. Patches of sorted, polygonal ground (nets) with varying degrees of activity occur along the chronosequence, with activity decreasing with distance from the ice margin. Soil development was studied along the chronosequence in three differently aged terrain units: (1) recently deglaciated (i.e., 20-30 yr); (2) deglaciated ca A.D. 1930; and (3) deglaciated between A.D. 1836 and 1867. Within each similarly aged terrain unit, pedogenesis was investigated in regards to three different categories of decreasing disturbance regimes: (1) polygon centers; (2) polygon borders; and (3) relatively stable nonpolygonal ground. Physical soil properties along with the use of a soil development index (i.e., PDI) show significant differences in pedogenic development between the three different categories of disturbance within similarly aged terrain units. The relatively stable, nonpolygonal soils have thicker horizons and so higher PDI values as compared to the soils of sorted polygons, suggesting that soil properties show the intensity of disturbance. Significant variations of PDI values were also observed with distance from the ice margin within decades of deglaciation and subsequent pedogenic development. Surficial A horizons obtained the highest index values over that of Bw and C horizons, suggesting developmental history is most represented in surficial horizons on very recently developed soils. These findings suggest that soil indices are useful geochronological tools on young landscapes and can be used to explore the pedogenic heterogeneity found across the landscape resulting from disturbance processes.