1. Case Studies of Selected Soils
Higher Geography
Biosphere
Case Studies of Selected Soils

2. A Soil Profile

3. Introduction
For higher geography you have to know about 3 main soil types:
Podsols
Brown Earth Soils
Gley Soils

4. Podsols
Podsols usually have clearly defined horizons. This is due to a process known as podsolisation.
This involves the pronounced leaching of material (iron, aluminium and humus) from the surface layers to the lower layers.

5. Podsols location
Podsols are found in northern boreal coniferous forests with associated cold, wet climates in which precipitation exceeds evaporation.
Podsols are also found in upland moorland areas.

6. Podsols Profile (1)
The Ao horizon forms from decaying plant litter which can be:
The pine needles, cones and twigs from coniferous trees.
Dead heather shoots from upland moorland.
Thanks to the cold climate, the organic matter decays very slowly to form an acidic mor humus.
Rain and melting snow combine with these organic acids and wash out (eluviate) the minerals from the A horizon. This produces an ash-coloured, bleached A horizon.

7. Podsols Profile (2)
Lower down the profile, aluminium, iron, clay and humus are washed in (illuviated) and redeposited in the subsoil or B horizon.
If iron accumulates over a long enough period, a rust coloured iron pan can form, often up to several cm thick.
Iron pans can prevent the penetration of plant roots and the free drainage of the podsol resulting in waterlogging.

8. Podsols Profile (3)
The C horizon forms from a range of parent material (fluvioglacial sand or till) or may be derived from acidic parent rock.

11. Usage
Podsols are not naturally fertile soils and crop yields rapidly decline.
Lime needs to added to counteract the podsol’s acidity and animal manure can boost the poor quality of the humus.

12. Brown Earth Soils
Brown Earth Soil have developed beneath the temperate broadleaved deciduous forests of Europe, Russia and North America.

13. Brown Earth Soil Profile (1)
The Ao horizon is rich in nutrients.
Because of the warmer climate the litter decomposes rapidly resulting in mull humus.
Mull humus is less acidic than mor humus and becomes well mixed with the soil materials thanks to the activity of earthworms and soil bacteria.

14. Brown Earth Soil Profile (2)
The A horizon has a dark brown colour because humus replaces minerals as they are leached out.
Leaching is, however, less pronounced because of a closer balance between evaporation and precipitation.
The B horizon is less distinct (compared to podsol) but is usually lighter in colour as humus becomes less abundant.

15. Brown Earth Soil Profile (3)
The C horizon is derived from varied parent material which can range from limestone to schists.
Plant roots can penetrate the C horizon to extract minerals and ensure the efficient cycling of nutrients through the ecosystem.

18. Land Use
Originally tree covered, these usually mildly acidic, brown earth soils, have been extensively exploited for agriculture since pre-history.

19. Gley Soils
Gley soils are found in sites which are waterlogged, either permanently or temporarily.
When soil is waterlogged for a long time, its pore spaces lose oxygen (anaerobic).
Such conditions mean that the decay of bacteria is slowed down. In addition, iron compounds in the soil are reduced chemically from their normal red-brown colour to a blue –grey colour.

20. Gley Soil Profile
The Ao and A horizons are darker reflecting the presence of organic matter.
A large amount of organic material can accumulate because of a lack of bacterial activity necessary to create humus.
The B horizon is predominantly blue-grey, indicating virtually continuous water-logging. This has developed from a C horizon derived from an impermeable clay layer.

23. Land Use
Gleying is caused by the inability of soils to shed water quickly.
Often found at the foot of slopes and floodplains, gleys can support wetlands and on occasions permanent pasture

24. Your turn
Read page 165 – 167.
Answer Soil Types, Case Studies question 2d.