Slope processes and alpine soils

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FRAGILE ALPINE ENVIRONMENTS

Time

In alpine regions, soils develop very slowly. Well developed soils like Podzols on silicatic rocks or Cambisols and Histosols on carbonate rocks often need thousands of years to reach their climax under a dense vegetation cover and only if there are no disturbances. But due to abundant geomorphologic processes in steep alpine areas, this long-lasting stability is seldom achieved. Therefore, all phases of “intermediate” soil types can be found adjacent to each other, depending on the age of the parent material. In high mountain systems, the influence of time can be studied along so-called chronosequences, e.g. along moraines, solifluction lobes, fluvial terraces, slope debris or alluvial cones of different ages.

Look at the influence of time on soil development. The indication of soil types and the time scale is adapted to the characteristics of the European Alps, and to silicatic rocks.

Case 1:
Constant conditions

Case 2:
Geomorphologic disturbance

Case 3:
Climate change

	Imagine you are standing on the dry Chilean Altiplano at 5000 m. You are facing a landscape that was full of glaciers in more humid times. Today, only moraines at different elevations give evidence of this dramatic change in climate. As a soil scientist you investigate the soils on top of the moraines, and find out that moraine A is composed of a well developed Luvisol, as is moraine C , moraines B and E a Cambisol and moraine D a Regosol.
1.	Can you order the moraines according to age, from the youngest to the oldest?
2.	According to the soil types, moraine B and E have a very similar age. But this conclusion is not right in all cases. Can you explain how these two moraines might have a very different age?
Solutions

29 August 2011 © ALPECOLe 2002-2007