First, have a go at reading the bitesize revision info and try a ‘test bite’ afterwards. This covers both soils and sund dunes.
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SOILS – PODSOL (picture/description/explanation)
Ao Horizon – the organic layer is a thin litter of pine needles or heather shoots due to podsols forming in areas of coniferous forest or heather moorland. There is not a high level of fermentation due to the cold climate. This means the humus layer is thin. The humus layer is an acidic MOR humus. There are also limited organisms in a Podsol e.g. earthworms. This makes the soil horizons clearly defined as the soil isn’t being mixed by worms etc.
The A horizon is a bleached ash-grey colour as you can see from the picture. This is because of the high rainfall (precipitation exceeds evaporation in these areas). This causes a process called Podsoliation where minerals are leached (eluviated) from the A horizon and illuviated into the B horizon. This is why the B horizon in the picture is a red/brown colour.
If you look closely at the picture you can see a very thin ‘iron-pan’ between the grey A horizon and brown B horizon. The iron pan is common in Podsol soil. It is a hard layer in the B horizon which has been made by prolonged leaching of minerals (mostly iron). The minerals build up over time to form a hard iron-pan which can cause waterlogging in the upper layers and prevent tree roots from getting through the soil.
