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Ecology - Soil Science > Factors of Soil Formation > Flashcards

Factors of Soil Formation Flashcards

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1
Q

What are PM weathering rates determined by?

A

Mineralogy, hardness, porosity, surface area(faster) or finer grains(water retention)

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2
Q

Solum

A

These are the surface and subsoil layers that have undergone same soil-forming conditions

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3
Q

Example of soil created by PM…

A

Quartz sand doesn’t create clay soils due to no Al

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4
Q

PM soil formation with igneous rocks…

A

Form abundant clay minerals with high fertility due to cations and building block

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5
Q

Example of materials determining weathering rates…

A

Granite contains mostly quartz and K feldspars, less quartz and more Na and Ca feldspars are mafic

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6
Q

What do sedimentary rocks depend on?

A

Formation fpressure, composiion of original deposit, sandstone orignates from sand-size sediment

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7
Q

Why are transported soils more productive?

A

Higher porosity

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8
Q

How does wind sort particles?

A

Drops largest particles newar source, carrying smaller larger distances

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9
Q

Loess

A

Terrestrial clastic sediment composed predominantly of silt-size particles formed by accumulation of wind-blown dust

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10
Q

Ice/Water particle distribution…

A

Glacial till and glaciations

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11
Q

Colluvium

A

This is soil and debris that accumulate at the base of a slope by mass wasting or sheet erosion

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12
Q

Climate variability in soil formation….

A

Precipitation/temperature most important, varying depending on elevation/latitude, yearly also

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13
Q

Cool humid climate soil characteristicis…

A

High OM accumulation, weathering products removal and dominant acidification

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14
Q

Arid-semiarid climate soil characteristics…

A

Evapotranspiration exceeds precipitation, OM accumulates more slowly, with rapid soluble salt and carbonate accumulation

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15
Q

What is regional climate characterised by?

A

Mean annual temperature and precipitation

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16
Q

Results of poor drainage or high water table?

A

Dominant redox reactions and gleying

17
Q

Temperature influence on sois…

A

Increases clay formation, clay type then influenced by climate: smectite found in drier climates than kaolinite

18
Q

Example of topgoraphy improtance?

A

Slope length and angle determine effective precipitation

19
Q

How slope influences soil?

A

Soil development(pedon thickness and horizon differentation) decreases with slope with increasing erosion

20
Q

How do slopes differ per hemisphere?

A

NH north faceing slopes colder due to less incident solar radiation

21
Q

How do plants add OM?

A

Root exudates, ell death with root growth and death/degradation

22
Q

How does OM influence soil formation?

A

Produce compounds that chelate cations and humus production

23
Q

How does canopy interception influence soils?

A

Rainfall assimialtes dissolved ions in crown drip, reacting with soil solid phase differently than pure water

24
Q

Hans Jenny equation?

A

S = f(Pm, C, R, B, T)

25
Q

Example of climate and time syngerism…

A

Calcaerous rock with moderate rainfall may have increased OM early, approaching equilibrium in few decades, whilst calcite and lcay take longer for steady levels for vegeatation

26
Q

Hydrolysis

A

H+ in H2O replacement, like clay mineral feldspar releasing K and adding H, accelearting weathering

27
Q

What can released K ion replaced by H+ do?

A

Form new complexes, cationic exhcnage, plant use, soil leeching

28
Q

What does hyrdolysis increase with?

A

OM decomposition, nutrient uptake, nitrification and S oxidation, as pH lowers with increasing H+

29
Q

How does hydration differ from hyrdolysis?

A

Water does not dissociate, expanding minerals and increasing weathering susceptibility

30
Q

Where are redox reactions most important?

A

Fe2 oxidation to Fe3 which strains crystals and accelerates weathering rate

31
Q

How do redox reactions influence solubility?

A

Some cations more mobile when reduced than when oxidised

32
Q

What are the two horizon groups?

A

Master Horizons - AOEBCR
Transitional Horizons

33
Q

A Horizon

A

Surface layer with high bio-activity thus high humus accumulation, mineral weathering, soluble product leaching and eluviation

34
Q

Eluviation

A

This is the sideways or downards movement of dissolved or suspended material within soil caused by rainfall

35
Q

O Horizon

A

Predominanntly organic matter

36
Q

E Horizons

A

Eluviation influenced by organic acid from A/O horizons combination with leaching waters that weather/translocate silicate clays, fe and al, leaving residual material

37
Q
A

Ecology - Soil Science (12 decks)

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