Soil Classification

AK & BR

3.44b

Why look at soil?

Because soil and its constituents are the base

material for growing trees.

There is a need for an objective site classification of United Kingdom soil / site types, upon which the growing and management of trees can be based.

History

Why a Forestry Commission soil classification?

FC soil classification – Soil Classes

Soils with well

aerated subsoil

Soils with

poorly aerated

subsoil

Flushed

peatlands

Unflushed

peatlands

Man-made

soils mining / quarry spoil, brownfield sites etc.

Rankers and

Skeletal soils bedrock present at < 30cm

Littoral soils adjacent to the coast, sands and gravels

main soil classes

minor soil classes

Typical soil constituents

30-20% WATER

COMPONENT

20-30% AIR

COMPONENT

45% MINERAL

COMPONENT

5% ORGANIC COMPONENT

What creates a soil?

• Parent material - (type of rock)

• Climate - (heat, water, wind)

• Organisms - (bugs, insects, fungi, bacteria)

• Topography - (landform)

• Time

Parent Material

The parent material is the material from which a

soil is formed, not necessarily the bedrock of

a site.

The geographic position of the parent material affects

the potential water holding capacity, fertility and

texture of a soil.

Soil particles - texture

SAND: coarse rough granular particles

SILT: smooth spherical particles

CLAY: flat, plate-like particles

Soil texture

triangle

Clay

Silt

Sand

Soils with well

aerated subsoil

Soils with

poorly aerated

subsoil

Flushed

peatlands

Unflushed

peatlands

3 Podzols

4 Ironpan soils

12 Calcareous soils

5 Ground-water gley soils

6 Peaty surface-water gley soils

7 Surface-water gley soils

1 Brown earths

8 Juncus (or basin) bogs

9 Molinia (or flushed blanket) bogs

10 Sphagnum (flat or raised) bogs

11 Calluna, Eriophorum, Trichophorum (or unflushed blanket) bogs

14 Eroded bogs

2 Man-made soils 13 Rankers and Skeletal soils 15 Littoral soils

FC soil classification – Soil Groups

A LAYER CAKE!

Soil Horizons

A - Top soil (mineral with incorporated organic material)

B – Mineral soil (altered parent material)

C – Parent material (unaltered)

O – Organic material (humus or peat layers)

L – Litter (fresh litter from previous growth season)

E – Elluvial (removed organic, clay and oxides)

Generic soil processes

Podzolisation (ironpan formation)

Gleying

Build-up of partially decomposed vegetation

(humus/peat)

Typical brown earth

Slight podzolisation

Slight gleying

Slight build up of partially

decomposed vegetation

(humus/peat)

Rooting is unrestricted

by anaerobic conditions

Brown earth

Soils with brownish or reddish colours,

free drainage and good aeration and

moderate or strong acidity, throughout

the profile. Humified organic matter is

incorporated into the mineral soil to give

a dark brown topsoil (A horizon). There

is no E horizon. The B horizon is

distinguished from the underlying C by a

richer brown colour due to weathering

and the residual accumulation of iron

oxides (Bw horizon).

Brown earth

A

B

C

O

Soil

Moisture and

Nutrient grid

Very Poor Poor Medium Rich Very Rich Carbonate

mor mor, modermoder,

oligomull

oligomull,

eumulleumull eumull

Very

Dry

Mod.

Dry

Sl. D

ryF

resh

Mois

tV

. M

ois

tW

et

Very

Wet

Soil Nutrient Regime

Humus form

Soil

Mois

ture

Regim

e

Rankers and shingle

Gravelly or

sandy podzols

and ironpan

soils

Gravelly or sandy

brown earths

Loamy podzols

and ironpan

soils

Podzolic gleys

and peaty

ironpan soils

Unflushed

peaty gleys

and deep peats

Loamy brown

earths

Brown gleys

Surface-water

gleys

Flushed peaty

gleys and deep

peats

Rendzinas

Loamy brown

earths of high

base status

Brown gleys of

high base

status

Surface-water

gleys of high

base status

Humic gleys of

high base status

and fen peats

Calcareous

brown

earths

Calcareous

brown

gleys

Calcareous

surface-

water gleys

Brown earth

Podzol soil

Acidic soil conditions

Oxide leaching

Humus movement

Humus and oxide deposition

Possible ironpan formation

Possible surface gley

formation

Possible subsequent peat

formation

Podzol

Podzols are free draining, well aerated,

strongly acid soils with a surface

accumulation of raw humus, an Ea

horizon from which iron oxides have been

removed, and B horizons in which

translocated humus or iron oxides have

been deposited. The A horizon, which

may not be well developed, consists of a

mixture of blackish humus particles and

bleached sand grains. The Ea horizon

consists largely of bleached sand grains

and is whitish in colour. Both A and E

horizons have a friable consistence.

Podzol

B

C

O

E

A

Podzol soil

Ironpan soil

The characteristic features of this group are an Eg

horizon underlain by a thin ironpan (Bf horizon).

The Eg horizon has a grey colour often with a

yellowish or greenish hue and ochreous or rusty

mottles or streaks. These gley like symptoms are

caused by reduction and segregation of iron,

during frequent periods of waterlogging and

anaerobism. There is a surface accumulation of

black greasy peat but this can be as little as a few

centimetres thick or as much as 45 cm, the

maximum allowed in the group. The subsoil,

beneath the ironpan, usually lacks gleying

symptoms and is not affected by waterlogging or

anaerobism. Ironpan soils are strongly acid

throughout the profile. The ironpan normally

passes through stones, depending on their

porosity, and also forms a conspicuous coating on

the stones.

Ironpan

B

C

O

E

A

Bf

Soil

Moisture and

Nutrient grid

Very Poor Poor Medium Rich Very Rich Carbonate

mor mor, modermoder,

oligomull

oligomull,

eumulleumull eumull

Very

Dry

Mod.

Dry

Sl. D

ryF

resh

Mois

tV

. M

ois

tW

et

Very

Wet

Soil Nutrient Regime

Humus form

Soil

Mois

ture

Regim

e

Rankers and shingle

Gravelly or

sandy podzols

and ironpan

soils

Gravelly or sandy

brown earths

Loamy podzols

and ironpan

soils

Podzolic gleys

and peaty

ironpan soils

Unflushed

peaty gleys

and deep peats

Loamy brown

earths

Brown gleys

Surface-water

gleys

Flushed peaty

gleys and deep

peats

Rendzinas

Loamy brown

earths of high

base status

Brown gleys of

high base

status

Surface-water

gleys of high

base status

Humic gleys of

high base status

and fen peats

Calcareous

brown

earths

Calcareous

brown

gleys

Calcareous

surface-

water gleys

Podzols and Ironpans

Typical surface-water gley

Waterlogged soil becomes

anaerobic (without oxygen).

Soil loses bright, ochreous

appearance and takes on a

grey / black or mottled grey

and yellow / blue / pink

appearance.

Rotten stones are found in

the gleyed layers.

Rooting is restricted by the

anaerobic conditions.

Surface-water gley

A distinct topsoil or Ag horizon, grey coloured

with rusty streaks, and some 15 - 25 cm thick,

overlies a mottled grey and yellow subsoil, the

Bg horizon. At a depth of about 100 cm the

mottling becomes less distinct, in the BCg

horizon, and within another 50 cm the colour

becomes almost uniform in the C horizon. The

profile may be attenuated by bedrock so that a

true C horizon may be absent. Textures in the

type are finer than sandy clay loam at least in the

Bg and BCg horizons although the Ag horizon is

usually loamy and the C horizon is usually less

clayey because it is less weathered.

Surface-water gley

B

C

O

A

Soil

Moisture and

Nutrient grid

Very Poor Poor Medium Rich Very Rich Carbonate

mor mor, modermoder,

oligomull

oligomull,

eumulleumull eumull

Very

Dry

Mod.

Dry

Sl. D

ryF

resh

Mois

tV

. M

ois

tW

et

Very

Wet

Soil Nutrient Regime

Humus form

Soil

Mois

ture

Regim

e

Rankers and shingle

Gravelly or

sandy podzols

and ironpan

soils

Gravelly or sandy

brown earths

Loamy podzols

and ironpan

soils

Podzolic gleys

and peaty

ironpan soils

Unflushed

peaty gleys

and deep peats

Loamy brown

earths

Brown gleys

Surface-water

gleys

Flushed peaty

gleys and deep

peats

Rendzinas

Loamy brown

earths of high

base status

Brown gleys of

high base

status

Surface-water

gleys of high

base status

Humic gleys of

high base status

and fen peats

Calcareous

brown

earths

Calcareous

brown

gleys

Calcareous

surface-

water gleys

Surface-water gley

Peaty gley

Waterlogged soil

becomes anaerobic

Litter breakdown is

slowed by anaerobic

conditions

Build up of partially

decomposed vegetation

less than 45cm deep

Rooting is restricted by

the anaerobic conditions

Peaty gley

This is a soil with impeded drainage and surface peat

accumulations between 5 - 25cm thickness. The peat is

black or dark brown and amorphous or almost so. When

partially dried the peat shows a granular or fine blocky

structure. Beneath the peat the Ahg horizon is black or

dark grey and usually less than 10 cm thick. The Eg

horizon may be well developed, with pale grey colour

dominant and ochreous mottling associated with root

channels and soft weathered stones. The Bg horizon has

a roughly 50:50 mixture of grey and yellow or ochreous

mottling. Towards the bottom of the Bg horizon, which

may be termed the BCg horizon, the mottling becomes

less prominent, usually because the ochreous colour

becomes less yellow and more khaki or olive and because

the grey colour becomes darker. In the C horizon the

colours become less distinct and eventually merge, i.e. the

original colour of the parent material is retained. Textures

in the type are finer than sandy clay loam in the Bg

horizon.

Peaty gley

B

C

O

A E

Soil

Moisture and

Nutrient grid

Very Poor Poor Medium Rich Very Rich Carbonate

mor mor, modermoder,

oligomull

oligomull,

eumulleumull eumull

Very

Dry

Mod.

Dry

Sl. D

ryF

resh

Mois

tV

. M

ois

tW

et

Very

Wet

Soil Nutrient Regime

Humus form

Soil

Mois

ture

Regim

e

Rankers and shingle

Gravelly or

sandy podzols

and ironpan

soils

Gravelly or sandy

brown earths

Loamy podzols

and ironpan

soils

Podzolic gleys

and peaty

ironpan soils

Unflushed

peaty gleys

and deep peats

Loamy brown

earths

Brown gleys

Surface-water

gleys

Flushed peaty

gleys and deep

peats

Rendzinas

Loamy brown

earths of high

base status

Brown gleys of

high base

status

Surface-water

gleys of high

base status

Humic gleys of

high base status

and fen peats

Calcareous

brown

earths

Calcareous

brown

gleys

Calcareous

surface-

water gleys

Peaty gley

A soil type defines a soil within a group of soils

with similar characteristics.

Upland brown earths have a slightly gleyed layer at the top (1u).

Many soils are fully classified at the type level.

FC soil classification – Soil Types

Soils with well

aerated subsoil

3 Podzols

4 Ironpan soils

12 Calcareous soils

1 Brown earths

1 Typical brown earth

1d Basic brown earth

1u Upland brown earth

1z Podzolic brown earth

3 Typical podzol

3m Hardpan podzol

4 Typical ironpan soil

4z Podzolic ironpan soil

4b Intergrade ironpan soil

12a Rendzina

12b Calcareous brown earth

12t Argillic brown earth

FC soil classification – Soil Types

Soil

Moisture and

Nutrient grid

Very Poor Poor Medium Rich Very Rich Carbonate

mor mor, modermoder,

oligomull

oligomull,

eumulleumull eumull

Very

Dry

Mod.

Dry

Sl. D

ryF

resh

Mois

tV

. M

ois

tW

et

Very

Wet

Soil Nutrient Regime

Humus form

Soil

Mois

ture

Regim

e

Rankers and shingle

Gravelly or

sandy podzols

and ironpan

soils

Gravelly or sandy

brown earths

Loamy podzols

and ironpan

soils

Podzolic gleys

and peaty

ironpan soils

Unflushed

peaty gleys

and deep peats

Loamy brown

earths

Brown gleys

Surface-water

gleys

Flushed peaty

gleys and deep

peats

Rendzinas

Loamy brown

earths of high

base status

Brown gleys of

high base

status

Surface-water

gleys of high

base status

Humic gleys of

high base status

and fen peats

Calcareous

brown

earths

Calcareous

brown

gleys

Calcareous

surface-

water gleys

Deep peat

Man-made

soils

Rankers and

Skeletal soils

13 Rankers and Skeletal soils

2 Man-made soils

2s Mining spoil, stony or coarse textured

2m Mining spoil, shaly or fine textured

13b Brown ranker

13g Gley ranker

13p Peaty ranker

13z Podzolic ranker

13r Rock

13s Scree

FC soil classification – Soil Types

13c Ranker complex

Littoral soils 15 Littoral soils

15s Shingle

15d Dunes

15e Sand with deep water-table

15i Sand with moderately deep water-table

15g Sand with shallow water-table

15w Sand with very shallow water-table

FC soil classification – Soil Types

A soil phase further describes a specific soil

type’s potential silvicultural characteristics.

Soil phases are only applied to the main mineral and shallow peaty soil types (peat < 45cm deep).

Multiple phases maybe combined to describe a soil type.

They are a flexible, yet precise description.

FC soil classification – Soil Phases

Soil Phase suffixes used with Soil Types 1-7z, 12b & 12t

Suffix Name Description

a shallow predominantly 30-45cm soil to bedrock (0-45cm for man-

made soils)

c cultivated considerable alteration to physical or chemical properties or

to vegetation by former agricultural use

e ericaceous vegetation contains sufficient Calluna (dominant to frequent)

to become a weed problem after planting

f flushed considerable enrichment with nutrients from flushing water,

as indicated by the presence and vigour of tall Juncus sp.,

Deschampsia caespitosa or Molinia

g slightly

gleyed

subsoil slightly mottled or with grey patches

h humose topsoil contains between 8 and 30% organic matter

i imperfectly

aerated

grey colouration is less prominent than usual, but doesn’t

quite qualify as type 7b

k calcareous pH > 7 in A, E or B horizons

Soil Phase suffixes used with Soil Types 1-7z, 12b & 12t

Suffix Name Description

l loamy texture throughout is not finer than sandy clay loam

p peaty presence of an O horizon (containing > 25% organic matter)

exceeding varying thickness (depending on soil type):

3 / 5 5 – 45cm

6 / 6z 25 – 45cm

4 / 4z 15 – 45cm

s extremely

stony

stones occupy more than 35% of soil volume

v alluvial soil developed in recent alluvium (river sediment) of sandy or

coarse loamy texture

x indurated has strongly indurated material within 45cm of the soil

surface; where the induration is moderately developed or at

45 – 60cm use (x)

z podzolic presence of bleached Ea horizon or humus rich Bh horizon

If more than one suffix is used they are placed in the order: v l p h z x g i s a f k c e

Intergrades and phases

Podzolic peaty gley i.e. very poor and wet

Podzol i.e. very poor and slightly dry

Podzol with peaty and gleyed phase

i.e. very poor and moist

Critical depths in soil profiles

Peat depth:

< 5cm mineral soil, no phase

5 – 25cm 7 become 6

5 – 45cm 3 and 5 become 3p and 5p

15 – 45cm 4, 4z and 4b become 4p, 4zp and 4bp

25 – 45cm 6 and 6z become 6p and 6zp

> 30cm 13p becomes deep peat

> 45cm deep peat

Depth to bedrock:

< 30cm ranker or rendzina

30 – 45cm shallow phase (a)

Depth to induration:

< 45cm indurated phase x, or (x) if moderate induration

45 – 60cm indurated phase (x)

Forest Grid reference

GPS waypoint no.

Soil type & phase Surveyor

Texture Date

Horizon details

and depth (cm)

(from the

surface)

O Stoniness (% volume)

A Humus type

E Root depth

B ESC Soil Moisture

Regime

C ESC Soil Nutrient

Regime

FC soil classification recording form