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Soils > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

How does climate influence soil formation?

A

Precipitation and temperature determine the intensity/nature of weathering

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2
Q

What are the types of weathering?

A

Physical, chemical, biological

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3
Q

What is effective precipitation?

A

Precipitation that penetrates to lower levels of soil profile. Carries solutes down horizon

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4
Q

How does effective precipitation influence soil formation?

A

A lack of water can keep elements in place to carry out/limit weathering. Higher eff/prec means higher weathering

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5
Q

How does temperature impact soil formation?

A

Warm + wet conditions= increase weathering, leaching, plant growth => carbon sequestration

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6
Q

What do organisms influence in soil formation?

A

Influences organic matter accumulation, weathering, and profile mixing

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7
Q

How do animals impact soil formation?

A

Animals create pores, mix layers, consume OM, and influence nutrient levels of soils

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8
Q

How does aspect of a slope affect soil formation?

A

Affects weathering, S-facing slopes have less water and less OM

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9
Q

How does relief and topography affect soil formation?

A

Different vegetation types inhabit different locations on the slope (grasses, confiders, deciduous) and have different soil effects

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10
Q

Where do you find residual material?

A

Upper slopes

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11
Q

Where would you find the colluvium soil? How is it characterized?

A

Lower slopes. Chunky and not well sorted

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12
Q

What is a floodplain?

A

A part of a river valley that is inundated during floods

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13
Q

What are the 3 types of alluvian stream deposits?

A

Floodplains, alluvial fans, deltas

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14
Q

Soil factor =

A

Climate, orgaisms, relief/topography, parent material, time

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15
Q

5 types of physical weathering

A

Temperature, water, ice, wind, biota

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16
Q

Define exfoliation

A

Peeling of outer layers because of difference in temp inside vs outside the rock. Expansion + contraction => stress => exfoliation

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17
Q

What are the 6 taxonomic categories of soils?

A

Order, suborder, great group, subgroup, family, series

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18
Q

How are orders defined?

A

Based off morphology

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19
Q

How are suborders defined?

A

Based on genetic similarities

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20
Q

How are great groups defined?

A

Diagnostic horizons and levels of certain chemicals

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21
Q

How are subgroups defined?

A

By a typic member and other members that have characteristics not shared with the typic member

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22
Q

How are families defined?

A

By properties like pH, texture, minerals, soil temp/depth

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23
Q

How are series defined?

A

Slight differences in texture or surface later. Very closely related soils

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24
Q

Which taxonomic group has the most detail?

A

Series

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25
Which taxonic group has the least detail
Order
26
Which taxonomic group covers the most area?
Order
27
Which taxonomic group covers the least area?
Series
28
What is soil texture?
Proportion of sand/silt/clay Size/distribution of soil particles
29
Why is soil texture useful?
Helps infer plant growth and suitability Does not change easily
30
How does particle size relate to water movement speed and retention?
Increased size = more surface area; high water speed less retention
31
Describe sand
Gritty, visible to naked eye, round or angular
32
How does sand correspond to plant growth?
Low nutrients available to plants Large pore space, well drained Loose soil Infertile and drought prone
33
Describe permeability and infiltration rates for sand
Low permeability and high infiltration
34
Describe silt
Smaller than sand, similar shape/comp, silky texture, low plasticity
35
How does silt relate to plant growth?
Large surface area = nutrient availability Better water retention
36
What is piping and where does it occur?
Water process that washes away silt and develops macropores in subsurface
37
Difference between adsorption and absorption
Ad: molecules adhere (sand) Ab: molecules drawn into (clay
38
What are clay particles? What are their traits
Colloids; do not readily settle out of water, shaped like flakes
39
Define gravity water, available water, hydroscopic water
Gravity water: moves fast through soil, cannot be used by plants => high in sand Available water: available for plants Hydroscopic water: tightly adhered water, unavailble to plants => high in clay
40
List textures in order of water availability
Silt loam is high H2O availability Sand is low availability Clay is low availability
41
Define biogeochemical weathering
When primary materials are converted into insoluble or soluble forms
42
What are the 6 types of biogeochemical weathering?
Hydration, hydrolysis, dissolution, acid rxns, redox, complexation
43
Define hydration
Intact water molecules bind to mineral
44
Define hydrolysis
Molecules split, hydrogen replaces cation from mineral
45
Define dissolution
Minerals dissolved by hydrating cations and anions until they are dissociated and surrounded by water
46
Difference between oxidation and reduction
Oxidation is loss of electron, reduction is gain
47
Define acid reactions
Weathering accelerated by acids, increading hydrogren activity in water
48
Define redox
Minerals containing iron, manganese, sulfur exposed to air and gain/lose electrons
49
Define complexation
Chemicals group together => acid complex. Speed weathering
50
What are the 4 soil forming processes
Transformation, translocation, additions, losses
51
Define transformation
Rock weathering and decomposition destroy some soil component and create others
52
Define translocation
In/organic materials move out/up/down profile
53
What are the 6 soil horizons?
Organic, A(topsoil), Eluviation, B(subsoil), C(parent), R(bedrock)
54
Define the O horizon
Organic material above mineral soil
55
Define A horizon
Topsoil- mix of mineral and OM
56
Define E horizon
Eluviation- light colored, water facilitated loss of material that leaves behind materials
57
Define B horizon
Subsoil - deposited minerals/salts, alteration to parent
58
Define C horizon
Parent rock - conconsolidated mineral horizon with no other horizon traits, retain parental structure
59
Define R horizon
Bedrock - unweathered parent rock
60
How are forest O horizons differentiated?
Litter, fermented, and humic based on level of decomposition
61
What are the 3 O subordinate horizons?
Oi, Oe, Oa
62
What is the Oi horizon?
Fibric, slightly recognizable OM
63
What is the Oe horizon?
Hemic, fine fragments, slight decomp, partially recognizable material
64
What is the Oa horizon?
sapric, high decomp, not recognizable material
65
What are the two types of clay
1:1 not expansive. 1 tetra per octa 2:1 is expansive. 2 tetra per octa
66
As particle size decreases and surface area increases...
Increase water holding Increase nutrient retention Increase nutrient release Increase aggregates Increase microorganisms
67
What is loam?
Mix of sand, silt, clay. Properties exhibited evenly, but the ratios can differ
68
How do we find soil texture?
Soil sieves or soil slurry
69
What are the classes for coarse fragments?
Gravel, cobble/channers, stones/boulders
70
What are peds or aggregates?
Clumps of soil, structural units of soil
71
What are abiotic influences on soil structure?
Freeze-thaw, wet-dry, shrink-swell, flocculation
72
What is flocculation?
Attraction of clay and organic molecules due to charge
73
What are biotic influences on soil structure?
Roots, animals. Humans, decomposition
74
75
Define particle density
Mass of soil solids, does not consider air or water. Generally same across board
76
Define bulk density
Particle density + pore space. Accounts for water and air
77
What influences bulk density?
Soil texture: fine texture is low BD Aggregates: loose packing is low BD
78
How does high bulk density affect plants?
Poor root growth, reduced aeration, and inneficient hydrology
79
Define porosity
Percentage of soil volume not occupied by particles
80
Relationship between bulk density and porosity
High BD is low prosity => inverse
81
Define macropore
Larg pore space, air and water movement, animal use
82
Define micropores
Water without air, some root hair/microorganisms but mostly hydroscopic water
83
How does compaction affect soil?
Macropores are reduced => high BD => reduces root growth, water cannot infiltrate, less air movement
84
What spheres make up pedosphere?
Lithosphere (minerals) atmosphere (gas exhcnage), hydrosphere, biosphere (living in soil)
85
What is the critical zone and why does it matter?
Where biological activity happens, outmost layer on earth where spheres interact
86
What does color tell us about a soil?
Dark = high OM White = carbonate Gray/green = oxidation Can help with classification
87
What soil texture has highest available water?
Loams
88
What textures have highest gravity water?
Sand
89
Recently deposited parent with low profile development. Used in rangeland but water conservation is critical. Found in rockies, sand dunes, floodplains
Entisols (ent:new)
90
Young soils with rapid profile development. Found in eastern us and the pnw
Inceptisols
91
Formed drom volcanic ash, highly fertile and used in agriculture
Antisols (ando: black)
92
Permafrost layer, young soil. Limited use because of temperatue and is being impacted by climate change. Found at the poles and high elevations of southern hemisphere
Gelisols
93
Develop in saturated conditions with 20% organic matter. Used for agriculture. Found in wetlands and marshes
Histosols (hist: tissue)
94
Dry year round with minimal leaching. Light gray when dry. Used for grazing and irrigation. Found in dry climates, western US and deserts
Aridisols (arid: dry)
95
Swelling with deep cracks under dry conditions. Well mixed. Not used for construction or agriculture.
Vertisols (vert: turn)
96
Thick organic matter with rich diversity. Important for agriculture and is the most productive soil. Found in prairies
Mollisols (moli: soft)
97
Gray/brown moist mineral soils. Good for agriculture and is found under cool decisuous forests
Alfisols (aluminum+iron)
98
Moist, acidic soils used for crop production. High leeching. Found in tropical areas, forests, and southeastern US
Ultisols (ultimus:last)
99
Acidic soils. OM accumulation in different horizons. Pine tree litter creates this soil. Mostly used for fruit and veg. Found in cold, moist, wet climates like PNW or along lakes
Spodosols (spodos: wood ash)
100
Very weathered, deep oxic subsurface, intense weathering and leeching. High clay content. Least used order because it needs heavy fertilization. Found in tropics
Oxisols (ox: oxide)
101
Describe soils under conifer trees
Soil is more acidic in upper parts under conifers because of tree litter. Litter discourages earthworms and creates a thick OM layer
102
Describe how parent material impacts soil factor
Alluvial deposits are favorable for ag. Sedimentary parent is more resistent to changes (yellow soil)
103
What is a polypedon
Multiple pedons
104
What is a pedon
3D body of soil used to determine internal arrangement of horizons
105
What are the steps to make soil?
Parent material gets eroded Plants grow in finer material Plant roots further break down rocks Horizons develop
106
What is SOM
Soil Organic Matter: living and dead matter
107
How much of the soil is minerals
45%
108
How much of the soil is water?
20-30%, reflective of climate
109
How much of the soil is pore space?
1/2
110
Where is CO2 highest, soil or atmosphere?
Soil
111
Define soil
Layers of mineral and OM affected by physical, chemical, or biological processes. Holds liquid, gas, and biota

Soils (3 decks)

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