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Biogeochem - Ernest > L1: Pedogenesis > Flashcards

L1: Pedogenesis Flashcards

1
Q

what is pedogenesis

A

formation of soils

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2
Q

how many laters in the soil profile?

A

5

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3
Q

what are the layers in the soil profile?

A

Organic horizon (O)

Leached horizon (A)

Accumulation Horizon (B)

Partially weathered horizon (O)

Parent Material (R)

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4
Q

What is soil leaching

A

the downward movement of dissolved mobile plant nutrients in the soil profile following percolating water such as rain or irrigation water

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5
Q

What form of iron is present in oxic conditions?

A

Fe(III) iron oxide

FERRIC IRON

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6
Q

What form of iron is present in anoxic conditions?

A

Fe(II)

FERROUS IRON

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7
Q

How does soil form?

A

The process of gradual weathering and removal of certain elements creating soil

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8
Q

What are the characteristics of the leached horizon?

A

Coarse mineral horizon from which iron, aluminium and clay minerals have been removed

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9
Q

what accumulates in the accumulation horizon?

A

fine organic material, clay minerals and iron oxides

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10
Q

What maintains the ecosystem balance in soils?

A

The combination of living biomass providing nutrients to different plant species which maintains soil fertility, health, biodiversity and biogeochemical cycles

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11
Q

What animals (in soil) are ecosystem engineers?

A

Ants
Termites
Earthworms

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12
Q

What is edaphology

A

The influence of soil properties on life

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13
Q

What is the connection between geoecology and pedology?

A

Plant species can indicate the soil/rock type

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14
Q

What type of soils do limestone soils create?

A

Basic (alkaline) soils

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15
Q

What type of soils does gneiss create?

A

Acidic soils

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16
Q

What do differing rock types determine?

A
  • physical structure of the soil and the environment
  • soil particulate composition
  • nutrient retention
  • drainage
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17
Q

What are the basic ingredients of soil?

A

Rock fragments such as
- grit
- silt
- clay
AND organic humus

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18
Q

Which soil is ideal for agricultural purposes

A

Loam

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19
Q

What is a soil aggregate/ped

A

individual soil particles that are stuck together to form larger soil structures

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20
Q

What examples of biological structures help to form soil aggregates?

A

roots and fungal hyphae

however, roots can also break up clay or loam aggregates

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21
Q

What causes clay minerals and organic matter to bind?

A

ionic and van-der-Waals interaction

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22
Q

What is van der Waals interaction?

A

attraction and repulsions between atoms, molecules, as well as other intermolecular forces

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23
Q

How does climate impact soil formation

A

Freezing and thawing can break up rocks, speeding up the soil formation process

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24
Q

What are the 3 main phases of soil formation

A

1) weathering and the build up of organic matter (leaching is an exception)

2) characterised by rapid property changes such as the formation of clays

3) Known as the steady state although leaching input and loses, and organic matter degradation and input are in balance

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25
Q

What forms of sedimentary rocks can you have?

A

Clastic (eg sandstone and shale)

chemical (lime stone)

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26
Q

What form of metamorphic rocks can you have

A

foliated (slate)

nonfoliated (marble and quartzite)

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27
Q

What forms of ingenous rocks can you have?

A

intrusive (gabbro and granite)

extrusive (basalt)

28
Q

what does felsic and mafic/ultramafic desribe?

A

the colour of rock

felsic is lighter rock

mafic/ultramafic is darker coloured rock

29
Q

What is the composition of granite and its pH

A

formed from sandy soils with a clay input from non-local runoff

30
Q

What is the composition of Basalt and its pH

A

Basic

formed from silt and clay soils

31
Q

What is the composition of Sandstone and its pH

A

Acidic

Sandy soils but is dependent on the cementing agent

32
Q

What is the composition of shales and its pH

A

Basic

silts and clays

33
Q

What is the composition of limestone and its pH

A

Basic

Commonly silts but also have a thin clay and sand layer

34
Q

What does autochthonous mean?

A

Soil derived from local parent rocks (or nearby parent rocks)

35
Q

What does allochthonous mean?

A

Soils formed with material from elsewhere

36
Q

list examples of allochthonous soil origins and the ‘mode of transport’

A

material moved by air
- loess, sands and ash fall

material moved by water
- exposed lake, river, saltmarsh and mangrove sediments

material moved by ice
- glacial depositys

37
Q

Types of weathering

A

Mechanical / Physical
Chemical

38
Q

Mechanical / Physical weathering definition

A

the break down of material due to mechanical / physical processes

eg wind, freeze thawing, glaciers

39
Q

chemical weathering definition

A

the composition of the rock altering due to chemical influences
- eg rainwater

40
Q

Are sand and silt chemically resistant? What does that mean?

A

Yes they are which means they are nutrient poor

41
Q

list examples of chemically altered fragments

A

silicate claus
iron oxide
aluminium oxide
chemical salts

42
Q

what is lay composed of?

A

Aluminium and Silica

43
Q

What colour are organic matter rich soils?

A

dark brown - black

44
Q

Hydrated iron oxides (ferric hydroxides) give what colour soil

A

yellowish

45
Q

Dehydrated iron oxides (ferric oxyhydroxides) give what colour soil

A

greyish soils

46
Q

What do white soils indicate?

A

carbonate deposits

47
Q

What are azonal soils?

A

mountain soils

48
Q

what is a catena?

A

the continuous variation of soil and vegetation types down a hillslope

49
Q

what are the features of a catena

A

Summit area
Upper convex slope
Main-slope
Lower main-slope
Concave slope
Foot-slope

50
Q

difference between the eluvial and illuvial zone

A

Eluvial zone is where the downward percolation of water through soil horizons which transports soil content from upper layers to lower levels occurs

illuvial zone is where the deposition of this material (illuvial deposit) in lower levels

51
Q

what influences leaching

A

The quantity of water influences what is leached

52
Q

Which section of the catena has well-drained soils

A

Colluivial zone

53
Q

what causes soils to vary along slopes

A
  • Drainage conditions
  • Transport of eroded materials (eg. mass movements, erosion)
  • Transport of dissolved material
54
Q

Where do you find acidic soils on a slope

A

At the summit/shoulder of the slope

in the eluvial zone

55
Q

Where do you find slightly acidic to neutral soils?

A

on the main slope

in the colluvial zone

56
Q

where do you find neutral to to alkaline (wet) soils

A

at the foot and toe slope

in the illuvial zone

57
Q

What happens if nitrate is leached from the top of the slope

(impact on soils)

A

Hydrogen ions accumulate at the top of the slope making the summit soils more acidic

58
Q

What are the stages of soil developments

A

Initial weathering and humus input

pedogenesis

mature soil type under environmental pressures

soil catena development

59
Q

what are the stages of vegetation development?

A

species origin or new site

seral development and colonisation

climax vegetation under environmental pressures

ecotyles / clines

60
Q

what is chelation

A

Chelation is a type of bonding of ions and the molecules to metal ions

61
Q

List 2 examples of chelating agents and which organisms use them?

A

Siderophores = Bacteria and Fungi

Phytosiderophores = plants

62
Q

Why are oceans iron deficient?

A

If oxygen is present, iron II is transformed to iron III which is not bioavailable for organisms to ude

63
Q

How is iron III used to treat waste water that is phosphorus rich?

A

Iron III is added as phosphorus sticks to it and its ‘cleans’ up the water

64
Q

In which zone is clay lost and in which zone is clay accumulated?

A

Eluvial zone = clay is lost

Illuvial zone = clay is accumulated

65
Q

What do ericoid and arbuscular mycorrhiza do?

A

They have a symbiotic relationship with the plant which provides it with immunity

66
Q

Thats the difference between ericoid and arbuscular

A

Biogeochem - Ernest (9 decks)

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