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Soils > Basics for Final > Flashcards

Basics for Final Flashcards

0
Q

What does soil texture refer to?

A

The relative amount of sand silt and clay as a % of the total volume of the mineral fraction of the soil

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1
Q

Describe the two portions that compose mineral matter.

A

CFC
- Material > 2mm

Textural Fraction (Sand/Silt/Clay)

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2
Q

Name some soil physical characteristics

A 
color 
density
porosity
structure and consistancy
drainage
horizon configurations 
plant rooting patterns
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3
Q

How does sand effect the soil?

what is sand composed of? elaborate.

A

Sand increases the drainage and trafficability of soils by increasimng pore space and aeration.

It is composed of Si02 and is inert due to a full valence shell. Si02 is a product of the chemical weathering of silicate RFM’s but is unique in that it does not provide any nutrients to the soil.

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4
Q

What can be done to minimize erosion on a road?

A
  • Crown surface
  • dig deep ditches that will act as a buffer zone
  • construct culverts and cross ditches, especially in flashier areas
  • construct culverts in a row to minimize catastrophic road failures
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5
Q

What does ped development imply about a soil?

A

Sign of soil maturity

  • higher surface area (for nutrient exchange)
  • better drainage (due to increased porosity)
  • usually high in stored nutrients
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6
Q

What does high clay and silt content imply about bulk density?

What if it is well structured?

A

High Clay/Silt = Low bulk density

can have high Pore space if well structured.

Structure relates to pore space/complexity

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7
Q

What is an A horizon called when the colloidal fraction gets washed down into the B horizon?

What is the scientific name of the process of soil being taken from one horizon into another?

A

The A horizon would become Ae which stands for elluviated.

The process is called translocation and elluviation is downward translocation.

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8
Q

What is an A horizon called when it becomes enriched with organic material from the O horizon?

A

Ah

which stands for humus enrichment

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9
Q

Describe soil management.

A

Manipulation of soil in such a way that it will generate specific objectives and values.

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10
Q

Whats the difference between mineral and organic soil?

A

Mineral soil has less than 17%organic carbon

Organic soil has more than 17%organic carbon

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11
Q

What is a ped?

A

A ped is a secondary soil structure (composed of primary soil particles)

  • sand/silt/clay
  • plus binding agents that “glue” them all together like
  • OM
  • Salts
  • Oxides
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12
Q

Define infiltration and percolation

A

Infiltration: Entry of water into soil

Percolation: Internal drainage (Movement of water through soil)

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13
Q

Define solum

How does it differ from soil

A

Solum is the upper portion of the soil profile (A and B horizons)
-the part that has undergone physical and chemical weathering

Soil is all the material that sits on top of the bedrock including parent material (C horizon)

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14
Q

Describe the layers of a podzol

What conditions do they develop under

A

Ae-elluvated (lost colloidal fraction)
Bhf/Bfh- enriched with iron/aluminum and organic colloids from the weathering of Ae
C-ablation till (parent material - usually coarse in podzols)

Podzols develop under cool/cold, moist/wet environments. Normally from coarse textured material.

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15
Q

What are all soils composed of?

A 
MOOHP
Mineral matter
Organic matter
Organisms
H20
Pore space (air)
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16
Q

Describe downward development of soil

A

As forest floor decomposes, humus is translocated into upper mineral soil to create the A horizon. At this point the soil is a regasol (Ah/C) As A horizon thickens, B horizon develops from C horizon via chemical processes and respiration of organisms in soil. The nature of the parent material combined with the climate will eventually determine what type of soil develops from a Regasol.

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17
Q

The material from which solum develops is called?

What are some properties?

A

Parent material

Tends to be free of OM
As exposed parent material is weathered it will develop into solum. The type of soil is largely dependant on parent material and climate.

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18
Q

Describe soil compaction. What are its results?

A

Soil compaction is when logging or industrial activity leads to the reduction of pore space. This is common when wet, fine textured soils are driven on by heavy equipment.

Results in

  • increased Bd
  • reduction of water infiltration and percolation
  • reduction of air movement (gas exchange)
  • reduction of root penetration
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19
Q

Briefly describe what parent material is…

A

Unconsolidated material from which solum develops

Often associated with C horizon

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20
Q

What is mottling?

A

Orange blotches where standing water has caused oxidation reactions with present minerals.

Due to most soils being a function of broken down silicate RFM’s containing iron and aluminum.

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21
Q

Describe the layers of a luvisol.

What conditions do luvisols develop under

A

Ae- elluviated mineral horizon

Bt- C or Bm horizons enriched with clay from Ae

C-Ablation till

Luvisols develop under cool/cold, moist/wet environments. Usually develop from fine textured parent material.

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22
Q

Explain Isostatic rebound

A

Expansion of the soil after glacial Ice retreats. Causes ground to rise.

23
Q

What constituates a mineral?

A

Inorganic
Crystaline structure
Specific chem. structure eg. SiO2

24
Q

What percent of minerals are silicates?

A

90% of roughly 2000 known minerals

25
Q

Why is relative surface area important?

A

More surface area = more nutrient exchange

Faster weathering

26
Q

What is the relative surface areas of the three primary soil particles?

A

Sand + Silt, relatively low SA

Clay: High SA

27
Q

Explain a secondary mineral

A

After full decomposition silicates form a secondary mineral from broken down components of their original structures.

ex. SiO4 + AlO6 = clay

28
Q

Define Nutrient

A

anything an organism requires to survive, grow and reproduce

29
Q

Explain plant nutrient uptake and sources of nutrients.

A

Most minerals are absorbed by the roots as Ions dissolved in water

Sources:

  • Primary (air and rocks) weathering of RFMs
  • Secondary (OM)
  • Tertiary (internal cycling)
30
Q

How many essential nutrients are required by trees?

A

16-18 for growth, development and reproduction

31
Q

What composes the O horizon

A

LFH
Litter
Fermentation
Humus

32
Q

What are some examples of site degradation?

A

Inappropriate harvesting resulting in :

  • Soil puddling
  • Soil erosion
  • Soil compaction
  • Forest floor displacement
  • Reforestation of wrong species
  • Alteration of microclimate by aggressive harvest
33
Q

What is a colloidal
what important role does it serve
What are two examples of colloids

A

All particles smaller than one micron

Source of most nutrients

Clay and Humus are both colloidal in particle size

34
Q

What is the end product when an RFM is completely weathered?

A
  • Silicon tetrahedron or aluminum octahedron. SiO4 or AlO6.
  • The molecules join together to form a lattice with a net (-) charge to which other nutrients and molecules adhere to.
35
Q

Describe the layers of a chernozem

What conditions form chernozems?

A

Ah- humus enriched soil (thin in chernozem)
Bm- C horizons that have been moderately weathered to form a brown layer
C- ablation till

Chernozems develop under dry warm climates (grasslands)

36
Q

Name 3 advantages of having a high CFC

A

long term nutrient source

soils with high CFC can withstand physical abuse

Soils with high CFC drain more easily

37
Q

How does silt affect soil?

A

Spherical shape of particle leads to blockage of pore spaces resulting in poor drainage

cause frost heaving, which breaks up soil leading to site degradation

38
Q

How is silt produced?

What size are its particles?

A

Mechanically weathered sand as a function of glacial grinding.

Silt size from 0.05mm-0.002mm

39
Q

How is clay formed?

A

Chemical weathering of silicate RFM’s

feldspar, hornblendes, mica etc

40
Q

What does yellow soil imply about drainage?

A

Poor Drainage

41
Q

What does red soil imply about soil?

A

Drains well (except for mottles!)

42
Q

Where are luvisols common?

Interior forests with fine textured parent material

A

Interior forests with fine textured parent material

cool, moist climates

43
Q

Where are podzols common?

A

Higher elevations that are cool and wet

coarse textured material

44
Q

Describe the layers of a brunisol

where are they normally found?

A

Ah- humus enriched mineral soil horizon
Bm- C horizons that have been moderately weathered to form a brown layer
C-ablation till

Develop under relatively dry, warm climates. Common in CWHxm

45
Q

Describe the layers of a Regasol

A

Ah
C

Immature soil

46
Q

What makes an essential nutrient essential?

A

Cannot be synthesized by the organism that needs them. Must be obtained from the soil

47
Q

Define soil

A

Unconsolidated material that sits on top of bedrock serving as a medium for plant life.

48
Q

Give several examples of mineral sources of nutrients

A 
Feldspars
Hornblendes 
Sulphides 
Sulphates
Oxides
Mica 
Quartz

There are many more

49
Q

What is the rock group that gives rise to mineral sources of nutrients?

A

Silicate rock forming minerals

RFM

50
Q

Describe what happens in soil puddling

A

Combination of compaction and re orientation of clay fraction to a horizontal plane

common in wet soils with high clay content

IRREVERSIBLE

51
Q

what is a pedon?

A

The smallest 3D unit of soil that can be used to describe a soil

52
Q

how many groups of brunisols are there?

what do they depend on?

A

4

depend on thickness of Ah and Ph of soil

53
Q

what is fluvial material

A

sediment from streams and rivers. generally coarse and sandy.

54
Q

What is Lacustrine material?

A

Silty fine textured material deposited in flood plains

contains allot of silt and clay

55
Q

where is texture most important?

A

in the B horizon where the breakdown of parent material takes place

Soils (2 decks)

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