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Environmental processes and systems, LEC 103 > Formation & importance of soils, lecture 27 > Flashcards

Formation & importance of soils, lecture 27 Flashcards

1
Q

Soil

A

The outermost layer of the Earth

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2
Q

How is soil formed?

A

Weathering of rocks

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3
Q

Phrase to describe soil

A

‘living mantle of the Earth’

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4
Q

Is soil a renewable or non-renewable resource?

A

non-renewable resource

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5
Q

Rough soil formation time

A

thousands of years to form

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6
Q

Soils are at the interfere of

4

A
  • Lithosphere
  • Atmosphere
  • Hydrosphere
  • Biosphere
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7
Q

Soils at the interface of

the Lithosphere

A

Soils formed from rock constituents.

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8
Q

Soils formed from rock constituents.

the atmosphere

A

 Air overlies and intermingles with soil.

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9
Q

Soils are at the interface of

the hydrosphere

A

Water flows through soil.

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10
Q

Soils are at the interface of

the biosphere

A

Biota live in and on soil.

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11
Q

Soil science is…

A

interdisciplinary

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12
Q

Key functions of soil
6
(according to DEFRA)

A
  • Food and Fibre Production 
  • Environmental Interaction
  • Support of Ecological Habitat and Biodiversity
  • Protection of Cultural Heritage 
  • Providing a platform for construction 
  • Providing Raw Materials
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13
Q

There is unlocked potential in soil resources for…

A

biological and medical resources

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14
Q

Regulation of water by soil,
Soil misuse or over-exploitation can have significant consequences for…
example?

A

groundwater, rivers, estuaries and coastal waters

eg: overuse of fertilisers

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15
Q

Link of soil to history

A

Dominant nations had good soil,

facilitates productive agriculture

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16
Q

Soils quality reflects

3 aspects

A 
all
chemical
physical
biological
properties
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17
Q

Main threats to soil function and quality

5

A
  • Erosion
  • Compaction and sealing
  • Contamination
  • loss of SOM (Soil organic matter)
  • Salinisation
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18
Q

Threats to soil function and quality

Erosion

A

(landslides)
loss of productivity and biodiversity
used linked to overuse

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19
Q

Threats to soil function and quality

Compaction and sealing

A

intensive use of heavy equipment or grazing whilst the soil is saturated
(loss of biodiversity, flooding)

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20
Q

Threats to soil function and quality

contamination

A

Metals and organic contaminants could degrade soil quality and functions, implications for the wider environment

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21
Q

Threats to soil function and quality

loss of SOM

A

Loss of SOM, loss of fertility, increased risk of erosion, also reduces water retention capacity, linked to climate change

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22
Q

Threats to soil function and quality

Salinisation

A
  • Excess accumulation of soluble salts due to saline water use in farming or irrigation practices
  • generally in hotter countries, Middle East
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23
Q

Percentage of the World’s freshwater stored in soil for plant use

A

66%

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24
Q

How should soil be viewed?

A

as a finite resource

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25
Q

Weathering

A

Physical and chemical breakdown of rocks and other materials

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26
Q

Soils relate to what

A

the rock they originate from

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27
Q

Factors controlling soil formation

5

A
  1. parent material
  2. climate
  3. biota
  4. topography
  5. time
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28
Q

Factors affecting soil formation

parent material

A

unconsolidated material or rock in which soil development occurs

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29
Q

2 examples of parent material deposits

A

organic deposits - peat

glacial ice transport - glacial till

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30
Q

Example of parent material

organic deposits - peat

A

Organic material deposited when accumulation exceeds decomposition: stratified deposit of peat.

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31
Q

Example of parent material

glacial ice transport - glacial till

A

Glacial till, material deposited directly by ice, is a heterogeneous (unstratified) mixture of rounded boulders, stones, sand, silt, and clay.

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32
Q

Factors affecting soil formation

climate

A

Temperature and precipitation (rainfall, snowfall)

33
Q

Which is the most influential of the four factors acting on parent material?

A

climate

34
Q

Which two climatic factors have major effects on physical and chemical weathering and biological processes

A

precipitation and temp.

35
Q

What allows carbonates to accumulate at shallow depths?

A

low rainfall

36
Q

Why do acidic soils form in humid areas?

A

intense weathering and leaching of basic cations - Ca, K, Mg

37
Q

Effect of water induced soil erosion on sloping land?

A

constant removal of developing layers

38
Q

When developing soil layers eroded from slopes due to erosion by water, what is the effect on soil downslope?

A

Deposition of soil materials downslope covers developing soil layers

39
Q

Weathering, leaching and erosion in warm and humid regions

A

more intense and occur for a longer period of time

40
Q

Why does rapid weathering not occur in cold areas such as Alaska?

A

soil is too cold

41
Q

Factors affecting soil formation

Biota

A

Living organisms, plants, organic residue, microbes, soil animals

42
Q

Soil in humid forest vegetation

A

soils are leached but have many layers of slowly decomposing organic matter

43
Q

Grassland soils

A

generally rich in well decomposed organic matter

44
Q

Arable soils

A

generally have low content of organic matter

45
Q

Soils that harbour many burrowing animals have…

A

fewer but deeper soil horizons.

46
Q

How do micro-organisms help soil formation?

A

by decomposing organic matter and forming weak acids

47
Q

Role of worms in soil

factors affecting soil formation - biota

A

important for mixing of soil

48
Q

Factors affecting soil formation

Topography

A

The Earth’s surface contour.

Slope, aspect, elevation and landscape position

49
Q

Horizons of soils on steep hillsides

A

thin

50
Q

Landlocked depressions

runoff, productivity, decomposition rates

A

receive more runoff, greater production of vegetation, but slower decomposition.

51
Q

Waterlogged, and high productivity of vegetation and low rate of decomposition results in…

A

organic (peat and muck) soils

52
Q

Slopes facing sun are…

A

warmer and drier than those not; water limitation may affect vegetation cover and warmer temperature can affect the breakdown of organic matter.

53
Q

Slopes tend to

- soil depth, drainage, erosion

A

decreased soil depth,
better drainage,
increased wind and water erosion

54
Q

What is relief vs topography?

A 
Relief = height difference between a high and low point (measured by contours on a map not elevation)
Topography = What the land looks like based on elevation
55
Q

Factors affecting soil formation

Time

A

Tine since parent materials were exposed

56
Q

What soil maturity based on?

A

development stage rather than age

57
Q

Is younger or older soil generally more fertile?

why?

A

younger soil is, as it had more minerals

58
Q

Which factors determine the length pf time for soil formation?
4

A
  • climate
  • the nature of the parent material
  • the organisms
  • topography
59
Q

What type of climate is soil formation faster in?

A

warm, humid climates

60
Q

Time periods of glacial till and sediments

A

short, <200 years

61
Q

Weathering of rock time period

A

varies, but can take thousands/millions of years

62
Q

Processes during soil formation (genesis)

5

A
  1. additions
  2. removals
  3. mixing
  4. translocation
  5. transformation
63
Q

Soil Horizons

A

Different layers of soil

64
Q

Soil profile

A

A section through soil horizons

65
Q

How many soil horizons are there?

A

six

66
Q

What are the six soil horizons?

in order

A 
O - horizon
A - horizon
E - horizon
B - horizon
C - horizon
R - horizon
67
Q

O - horizon of soil

A

A thin layer which is at the top of the soil and is composed of leaf litter and organic matter

68
Q

A - horizon of soil

A

The soil layer below the top layer (o-horizon) which is composed of the most humus so is the darkest generally.

69
Q

E - horizon of soil

A

The layer below A - horizon with a high clay content and insoluble minerals such as quartz, soluble materials will have leached from this layer.

70
Q

B - horizon

A

The layer below the E - horizon where there is little organic matter content, yet soluble minerals and iron oxides build up here.

71
Q

C - horizon

A

Bedrock which is mixed with clay and is broken, decayed and slightly altered.

72
Q

R - horizon

A

The bottom soil horizon which made up of unaltered bedrock.

73
Q

Processions during soil formation (genesis)
Additions
9

A

Water (from the surface, and by ground water discharge)

Suspended and dissolved materials carried by water

Solids transported by wind

Gases from the air

Energy from the sun

Organic carbon by plants in the form of roots and root-derived material

Organic carbon by photoautotrophic bacteria

Organic nitrogen by nitrogen-fixing bacteria

Plant and animal remains on and in the soil

74
Q

Processes during soil formation (genesis)
Removals
7

A

Material removed by wind erosion

Material removed by water erosion

Dissolved and suspended material leached out

Uptake of nutrients from the soil by plants

Carbon dioxide gas produced by plant root, microbial and faunal respiration

Other gases such as nitric oxide, nitrous oxide and nitrogen produced by denitrifying bacteria

Other gases such as methane which are produced under anaerobic conditions

75
Q

Processes during soil formation (genesis)
Mixing
4

A

Soil animals

Tree fall and gravity

Shrinking and swelling due to water content changes

Freezing and thawing

76
Q

Processes during soil fomation (genesis)
Translocation
3

A

Gradients in water potential and chemical concentrations withinthe soil pores

Soluble minerals, colloidal material, organic compounds, andiron may move up or down the profile, between horizons, with water movement.

Biological activity may cause gradients in the chemical composition of the water and air-filled pores of the soil.

77
Q

In the formation of soils, translocation means…

A

vertical movement of materials

78
Q

Processes during soil transformation (genesis)
Transformation
3

A

Soil components are transformed by chemical and biological reactions.

Organic compounds decay, some minerals dissolve, other minerals precipitate.

These transformations result in the development of soil structure, and in changes in colour, relative to the parent material.

Environmental processes and systems, LEC 103 (10 decks)

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