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75 Cards in this Set

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  • Back
List the five main functions of soil in an ecosystem...(*plus two extras)
1. Medium for plant growth
2. Recycling of nutrients and organic matter
3. Controls the flow and purity of water
4. Habitat for soil organisms
5. Functions as a building material; Engineering medium

*6. Modifier of the atmosphere
*7. Information storage medium
What are the five master soil horizons?
O - pure organic matter; degree of decomp.
A - mineral soil; high organic matter

E - site of eluviation/leaching
B - site of illuviation/accumulation
C - substratum; least weathered parent material

*R - bedrock*
What are the four components of soil and their percent composition of each?
Water ~ 20-30 %
Air ~ 20-30 %
Minerals ~ 45 %
Organic Matter ~ 5 %
What are the sub-horizons under master horizon O?
i ~ identifiable; lightly decomposed
e ~ slightly identifiable; mod. decomposed
a ~ unidentifiable; highly decomposed
Define: Solum
Uppermost section of soil where there is biological activity.
Define: Regolith
Loose earth above solid rock
("can you stick a fork in it?")
Define: Parent material
Chemically weathered material from which soil forms
Define: Saprolite
Regolith that has weathered in place from underlying bedrock
What are the sub-horizons within master horizon A?
p ~ plowed surface (agricultural soil)
b ~ buried surface
What are the sub-horizons within master horizon B?
t ~ clays
g ~ gleying (iron depletion)
k ~ carbonates (very dry)
s ~ translocated sesquioxides
h ~ humus
w ~ weak B definition
o ~ residual oxides (tropical soils)
What are the sub-horizons within master horizon C?
r ~ saprolite (highly weathered bedrock)
k ~ carbonates
The type of mineral component in soil depends on what?
The underlying bedrock
While it makes up a small percentage of soil content, organic matter is....?
- Hugely influential on soil properties
- Synthesized by soil microbes
What are the four main functions of organic matter in soil?
1. Structure (soil glue!)
2. Water holding capacity
3. Nutrients for plants
4. Food/energy for soil organisms
The air in soil pores are high in ______ and low in ______.
Carbon dioxide; Oxygen
Soil is.......(3 things)
1. 4-dimensional complex habitat
2. self-organizing body
3. living thing
What are the five factors of soil formation?
[Active factors]
1. Climate/environment
2. Organisms
[Passive factors]
3. Relief/topography
4. Parent material
5. Time
What are the two processes that create soil?
1. Weathering of minerals (primary) to clay (secondary)

2. Accumulation of organic matter and decomposition to humus
What are the three major types of parent material?
1. Rock
2. Sediment
3. Organic matter
What are the three major rock types and their properties?
Igneous ~ cooled magma; faster cool = finer grain, slower cool = coarse grain

Sedimentary ~ decomposition of igneous rock, compaction of particles

Metamorphic ~ fusion of rock sediments, but not fully fused
Fast forming rocks lead to........?
Finer texture minerals and soils (i.e. clays and silts)
Darker minerals generally.........?
Fast weathering, yield more fertile soils
What are the different "transported sediments" within Parent Material?
[Mixed materials]
Glacial till/iceberg erratics ~ ice
Colluvium ~ gravity

[Sorted materials]
Alluvium ~ moving water
Lacustrine ~ lake water
Marine ~ ocean
Aeolian dust/loess ~ wind
What are the two parts of climate as a soil forming factor?
- Temperature
- Effective precipitation
What are the four kinds of organisms as a soil forming factor?
- Vegetation ~ roots, leaves
- Microbes ~ decomposition
- Soil animals ~ pathways for subterranean movement
- Humans ~ tillage, compaction, chemicals
What are the three factors of topography as a soil forming factor?
- Relief ~ steep/flat
- Aspect ~ direction of face (N,W,E,S)
- Elevation ~ linked to temp/organisms
Define: Krotovina
Tunnels created by various soil organisms that allow for movement of water
Define: Bioturbation
Organisms naturally moving and tilling the soil.
List the various parts of a landscape from summit down to floodplain....(5 total)
With a 10 degree temperature increase, there is.......?
a doubling in biological activity (as well as increased pedogenesis)
The main effect of time as a soil forming factor is.....?
Soil horizonation/ maturation
What are some factors that retard soil development? (7)
- Low rainfall/relative humidity
- Parent materials mostly quartz
- High clay content
- High water table
- Steep slopes
- Cold temperature
- Presence of toxins
What are the four processes that affect soil development (add examples)?
Additions: rain, organic matter, capillary movement

Losses: runoff, leaching

Translocations: organic matter, clay, iron

Transformations: organic matter to humus, primary minerals to clay
What are the six types of chemical weathering?
1. Hydration ~ addition of water
2. Hydrolysis ~ breakup of water, H+ acts as acid for weathering
3. Carbonation ~ formation of carbonic acid
4. Complexation ~ organic acids interact with metal ions; chelation

5. Oxidation-Reduction ~ exchanged of electrons

[All leading to....]
6. Dissolution
What is the main key to weathering (chemical and physical)?
Water (effective precipitation)
Describe the current USDA soil classification system...
- Each part of the name tells you something about the soil.

- Used since 1965

- Based on soil properties than can be measured/observed: color, moisture, structure, etc.
Define: Pedon
The fundamental unit of soil classification (1-10 sq. meter area to a depth of 3-4 meters)
Define: Polypedon
Contiguous group of similar pedons
Define: Soil series
Group of polypedons with similar charactistics
What are the six categories of general soil classification?
Great group
Level of description:
One word, formative element, ending in -sol
Order (i.e. Andisol)
Level of description:
2 parts, tells something about properties, contains the order
Suborder (i.e. Cryand)
Level of description:
3 parts, adds more info, contains order and suborder
Great group (i.e. Duricryand)
Level of description:
2 words, adds more info, contains great group, suborder, and order
Subgroup (i.e. Aquic Duricryand)
Level of description:
5-6 words, more info about soil, longest chain
Family (i.e. Medical-skeletal amorphic Aquic Duricryand)
Level of description:
Single name with no real scientific information
Series (i.e. "Grousehilll")
Explain "genetic" vs. "diagnostic" labels...
Genetic: based on observational data; initial guess as how it should be identified

Diagnostic: based on specific lab data (texture/chemical)
**Diagnostic labels help classify the soil taxonomically**
What six soil orders are considered the less developed or "young" soils?
What six soil orders are considered the more developed or "mature" soils?
Which two soil orders are a pair that develop in tropic conditions and under extreme weathering?
Which two soil orders are paired as being the youngest soils?
Which two soil orders are paired as being the most fertile and productive?
Which two soil orders are known for having Albic horizons (E horizons; zone of depletion/elluviation)?
Explain: Entisols
- Newly developed soil
- Very little horizonation
- Exist in areas where their parent material hasn't reacted to soil-forming factors (i.e. high heat, high moisture, etc.)
Explain: Inceptisols
- Young soil
- Weak horizon development
- Presence of Bw horizon (i.e. Cambic)
- Found in most climatic and physiographic conditions, like Entisols
Explain: Andisols
- Formed on volcanic ash and cinder deposits
- Found near volcano source or downwind from the volcano
- Aluminum-Humus complexes
- Light, fluffy soil; easily tilled, yet high water capacity and resistant to water erosion
- High fertility
Explain: Gelisols
- Permafrost and cryoturbation (frost churning)
- Broken/convoluted horizons
- Infertile
Explain: Histosols
- Organic soils
- Peat; comprised of partially decomposed, fibrous remains of plant tissues
- Wet, boggy, marsh climates
Explain: Aridisols
- Dry soils
- Water deficiency; no available water
- Light in color; low fertility
Explain: Vertisols
- High clay content; shrink-swell
- Subhumid to semiarid environments
- Slickensides develop as the clay swells around once open cracks (Bss)
Explain: Mollisols
- Dark, soft, fertile soils
- Found in grasslands
- Has Mollic epipedon
Explain: Alfisol
- Moderately leached (E horizon)
- Cool-hot humid climates
- Deciduous forests
- Argillic (Bt) horizon
- Albic (E) horizon
Explain: Ultisols
- Highly leached
- Tropical climates
- Highly weathered, High oxides
- Less weathered than Oxisol
Explain: Spodosols
- Sandy, forest soils
- Acid parent materials
- Albic (E) horizon
- Moist, wet (subtropic) conditions
Explain: Oxisols
- Most highly weathered
- Tropic conditions ~ hot and wet
- Highly leached
List the 6 moisture regimes from WET to DRY...
Aquic - saturated for extended period
Udic - not dry more than 90 days
Ustic - dry 90 to 180 days
Aridic - wet less than 90 days
Xeric - dry summer, wet winter
Torric - dry and hot
List the 7 temperature regimes from COLD to HOT...
Iso- (frigid, mesic, thermic, hyperthermic)
List 5 key features as suborders...
Fluv- fluvial; from river
Psamm- sandy
Alb- albic horizon; leached
Arg- argillic horizon (Bt); clayed
Orth- "true definition"; "Orthod" = spodosol
List the 5 naturally-occuring diagnostic surface horizons, as well as the 2 human-caused horizons...
Mollic - high base sat. (Mollisol); grassland
Umbric - low base sat. (Alfisol); less fert. than Mol.
Ochric - low base sat.; light/infertile; less organic matter
Melanic - volcanic materials (Andisols); light/fluffy
Histic - peat bog; all vegetative (>20% OM)

Anthropic - mollic-like; added P+; human-modified for agriculture (therefore Ap)
Plaggen - manure and pottery shards added over years
List the 6 diagnostic subsurface horizons and their qualities...
Albic: light color; elluviation (E); low in clay/oxides
Cambic: weakly developed (Bw)
Spodic: illuviated with accumulations of O.M. and oxides
Agrillic: subsurface accumulation of silicate clays (Bt)
Oxic: weathered, high Fe/Al oxides
Calcic: carbonates, often chalk like (Bk)
What are the distinctions for each (used as suborder, great group, or subgroup)?
- Agri - Psamm
- Calc - Cry
- Dur - Fluv
- Hapl - Torr
- Hum
Agri: clay (Bt)
Calc: carbonates (Bk)
Dur: hard
Hapl: "meets minimum requirements"
Hum: humic materials
Psamm: sand
Cry: frozen
Fluv: fluvial materials
Torr: dry
What are the three general types of subgroup distinctions?
Central concept
How are Families differentiated?
Particle size, mineralogy, fertility, temperature class
Oregon has every soil order except what two?
Oxisols and Gelisols
What is the size differentiation for:
Sand, Silt, and Clay?
Sand is >0.05mm
Silt is 0.05mm to 0.002mm
Clay is <0.002mm