Soil profiles,
characteristics and
profiles.
Podzol.
Brown Earth
Gley
Podzolization
 This
is an intense form of leaching.
 Occurs when rainfall is greater than precipitation.
 The main substances leached out of the soil
include iron, aluminium and humus compounds.
Describing Podzols
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LOCATION – found in Northern coniferous
forests OR upland moorland areas.
CLIMATE – cold wet climates where
precipitation exceeds evaporation.
DESCRIPTION – Thin top layer, Ao Horizon,
of needles and cones decomposing to form a raw
acidic humus (mor).
The A horizon has a ash coloured tint to it
composed of insoluble silicates.
The B horizon has a reddish tint to and an iron pan
may form here.
Explaining the formation of Podzol.
The soil forming process is very slow because of the cold
climate.
 Ao Horizon - Thin humus layer because of little
humification:Trees have needles not leaves.
Trees do not shed their needles every year.
Needles break down very slowly.
Few biota live in this cold climate.
 Leaching occurs due to heavy rainfall and melt water.
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Continued….
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A Horizon - Zone of Eluviation where humus, iron and clay are
leached through the A Horizon.
B Horizon - Zone of Illuviation where clay, humus and iron are
deposited and accumulated. Giving the red tint to the horizon.
Iron pan forms where iron is re-deposited between the A and B
horizons.
The soil is sometimes waterlogged because the iron pan prevents
further downward movement of water.
C Horizon – forms from a range of parent material
There is very little mixing of the horizons because of lack of
living organisims – BIOTA.
Describing Brown Earth Forest Soils.
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LOCATION – deciduous forests of
Europe, Russia and North America.
CLIMATE – mild winters and summers,
quite wet all year. Temperate maritime.
DESCRIPTION – Ao Horizon made up
of leaf debris, forms a mild acid humus.
The A horizon is a brown layer mergining
into the B horizon, brown colour becomes
lighter into the C horizon.
There are no clearly defined horizons.
Explaining the formation of Brown
Earth Forest Soil.
 Rich
humus layer made up from decaying grasses
and herbs and falling leaves every autumn.
Compared to Podzol the humification process is
quicker because of the warmer climate. Results in
a mull humus this is less acidic.
 Some leaching throughout the year because
precipitation exceeds evaporation.
Continued…..
A horizon has a dark brown colour as humus replaces
minerals as they are leached out. Leaching however is
less pronounced here.
 B horizon is less pronounced in colour because humus
becomes less abundant here.
 C Horizon is derived from varied parent material.
 Mixing of horizons due to presence of soil biota.
 Tree roots reach deep into the soil to allow any leached
chemicals to be brought back up into the leaves.
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Gleying
 Is
the inability of soils to shed water quickly. Often
found at the foot of hills.
Describing Gley
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LOCATION – Arctic.Found it sites that
are waterlogged.
CLIMATE – cold climate.
DESCRIPTION – Black Ao horizon,
thin layer of black acidic humus.
A horizon is poorly drained with a dark
grey colour to it.
B horizon is blue, grey with iron
compounds mixed through it.
Explaining the formation of gley.
 Weathering
is slow due to cold climate.
 Humification is slow because of:
 Little
vegetation.
 Cold and dry
 Few biota.
 Very
little leaching because:
 Soil
is frozen for most of year.
 Subsoil is impermeable permafrost, but some leaching
after snow melt.
continued
Lack of biota because waterlogged conditions – no
oxygen.
 Vertical mixing in the soil takes place as a result of the
annual freeze thaw cycle. This may result in poorly
defined horizons.
 The iron compounds in the A horizon have lost their
reddish colour to a blue grey colour.
 The B horizon is predominantly blue grey indicating
virtually continuous water logging, this had developed on
a C Horizon derived from an impermeable clay layer.
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Key Words
 Illuviation
 Eluviation
 Humification
 Leaching
 Capillary
Movement
 Podzolization,
 Gleying