Biosphere

Question 1

The A horizon contains…

Answer 1

A mix of humus and and other mineral particles

Question 2

The B horizon contains…

Answer 2

Coarser material - this is the subsoil layer.

Question 3

The C horizon contains…

Answer 3

Weathered rock fragments

Question 4

The D horizon is the…

Answer 4

Bottom layer - this is the parent rock layer

Question 5

Define Leaching

Answer 5

Leaching occurs when there is excessive rainfall, water moving downwards through the soil transports minerals downwards.

Question 6

Capillary Action is…

Answer 6

The process by which soil moisture moves through the fine pores of the soil. This produces more alkaline soils.

Question 7

Leached soils such as…

Tend to be…

Answer 7

Podsols

Acidic

Question 8

The rate of weathering of the parent rock greatly depends on…

Answer 8

The climate - the quickest rate of breakdown occurs in hot, humid climates

Question 9

What are the first two stages in the formation of soils?

Answer 9

1. The weathering of parent rock over a considerable period of time
2. The result of adding water, gases, living organisms and decayed organic matter.

Question 10

The type of vegetation in an area is related to the amount of precipitation. The vegetation provides humus. Humus is found more in… than in…

Answer 10

Tropical Forests

Tundra Areas

Question 11

Define Eluviation

Answer 11

The washing out of material, that is the removal of minerals such as Calcium and aluminium, and organic material from the A horizon.

Question 12

Define Illuviation

Answer 12

The deposition of washed material in the subsoil. Heavy minerals are deposited much deeper, effecting soil fertility.

Question 13

Organisms within the soil….

Answer 13

Affect the breakdown and decay of vegetation and therefore impact on the depth of the humus layer.

Question 14

Living creatures affect the development of the soil through…

Answer 14

Exposing the soil to air by aerating it and can add to the chemical balance of the soil through their excreta

Question 15

Podsolisation is common in areas where…

Answer 15

Precipitation greatly exceeds evapotranspiration - Common in areas with cool climates and mainly coniferous forest

Question 16

Podsolisation is when…

Answer 16

Percolating rainwater becomes acidic as it passes through an acidic humus formed from falling pine cones and needles.
The water dissolves and removes iron and aluminium oxides from the topsoil -leaving a high level of silica in the A horizon.

Question 17

Greying occurs when…

Answer 17

Waterlogged conditions exist in the soil due to the loss of water from the soil being restricted.
In poorly drained areas where the land is more gently sloping.

Question 18

Describe the formation of a podsol

Answer 18

Falling pine needles and cones create an acidic humus called mor.
Very little mixing or movement of the horizons due to earthworm absence.
Cementing affect takes places between the A and B horizons to form a hardpan which effects drainage - upper layers become waterlogged.
Decomposition of Ao horizon is very slow due to the cold climatic conditions.
High silica residue left behind due to leaching in A horizon caused by meltwater during spring.

Question 19

Describe the colours in a Podsols horizons

Answer 19

Ao - Black ; Layer of cones and needles
Mor
Mineral and organic layer

A - ash-grey layer with iron pan due to mineral removal

B - Reddish- brown layer due to iron oxides

C - Parent material - grey with black weathering

Question 20

Describe the formation of a brown earth soil

Answer 20

Humus layer is thick/fertile due to the variety of vegetation that is decayed.
Warmer - Leaf litter decomposes quick due to organisms in the soil - less acidic humus referred to as mull.
Precipitation exceeds evaporation - causing leaching. Not enough to cause Podsolisation.
Horizons merge more than in Podsols due to the activity of biota.
Re deposition of iron and aluminium due to Illuviation causes reddish brown colour.
No hardpan unlike Podsols and soils tend to be free draining.
High clay content throughout profile - increasing soil fertility.

Question 21

Brown earth soil colours

Answer 21

Ao - Leaf debris
Black - with mild acid humus containing plant foods

A - Dark brown layer

B - Brown layer

C - Deep roots take up the bases

Weathered parent material at bottom

Question 22

Describe the formation of a tundra grey soil

Answer 22

Subsoil remains frozen throughout the year. Brief summer allows for ground surface to thaw but meltwater cannot melt freely.
Results in soil becoming waterlogged or gleyed
Bacterial action restricted due to cold temps.
Waterlogged soil lacks oxygen and tundra vegetation is also limited.
Alternate periods of freezing and thawing cause disturbance and mixing of soil.
Restricted use and less defined horizons.

Question 23

Colours in a Gley/Tundra soil

Answer 23

Small shrubs on top
A horizon - Black acidic humus

B - Waterlogged
Blue grey
Clayey mud

C - Angular rock fragments

D - Stone coloured

Permafrost

Bedrock

Question 24

Capillary Action

Answer 24

The upward movement of water in a soil

Question 25

Gleying

Answer 25

When soils becoming waterlogged with stagnant water that won’t drain away, oxygen entry is restricted turning red iron oxides blue-grey

Question 26

The layer closest to the surface is known as…

And it contains…

Answer 26

The Ao layer

He organic material derived from dead plants and other organisms - known as humus.

Question 27

Translocation is when…

Answer 27

Water moves downward into the soil it causes material to be removed through the processes of leaching and Illuviation

Question 28

Podzol Characteristics

Answer 28

Slow litter breakdown
Formation of an acid mor humus
Coniferous vegetation is waxy and acidic - hindering composition
Clearly defined horizons
Grey with a red/dark brown iron pan
Higher rates of leaching in podzols caused by melt water which creates excessive Spring leaching

Question 29

Brown Earth Soil characteristics

Answer 29

Brown earth soils have a faster breakdown, creating a mildly acidic mull humus
This is due to the higher temps
Mixed horizons - indistinct caused by high level of organic matter
Brown in colour
Deep root penetration causes water to pass more freely through brown earths and into the parent material

Question 30

Gley Soil

Answer 30

Gleys found in cool regions such as the tundra
Limited vegetation
Acidic humus caused by slow vegetation breakdown in cold climate
Poor drainage as Gleys characterised by waterlogging due to the peat
This denies the oxygen that supports the presence of soil organisms
Flat landscapes, limited run off
Parent material found in B horizon of the soil due to frost shattering of the parent material