Exam 3 Flashcards
How does climate influence soil formation?
Precipitation and temperature determine the intensity/nature of weathering
What are the types of weathering?
Physical, chemical, biological
What is effective precipitation?
Precipitation that penetrates to lower levels of soil profile. Carries solutes down horizon
How does effective precipitation influence soil formation?
A lack of water can keep elements in place to carry out/limit weathering. Higher eff/prec means higher weathering
How does temperature impact soil formation?
Warm + wet conditions= increase weathering, leaching, plant growth => carbon sequestration
What do organisms influence in soil formation?
Influences organic matter accumulation, weathering, and profile mixing
How do animals impact soil formation?
Animals create pores, mix layers, consume OM, and influence nutrient levels of soils
How does aspect of a slop affect soil formation?
Affects weathering, S-facing slopes have less water and less OM
How does relief and topography affect soil formation?
Different vegetation types inhabit different locations on the slope (grasses, confiders, deciduous) and have different soil effects
Where do you find residual material?
Upper slopes
Where would you find the colluvium soil? How is it characterized?
Lower slopes. Chunky and not well sorted
What is a floodplain?
A part of a river valley that is inundated during floods
What are the 3 types of alluvian stream deposits?
Floodplains, alluvial fans, deltas
Soil factor =
Climate, orgaisms, relief/topography, parent material, time
5 types of physical weathering
Temperature, water, ice, wind, biota
Define exfoliation
Peeling of outer layers because of difference in temp inside vs outside the rock. Expansion + contraction => stress => exfoliation
What are the 6 taxonomic categories of soils?
Order, suborder, great group, subgroup, family, series
How are orders defined?
Based off morphology
How are suborders defined?
Based on genetic similarities
How are great groups defined?
Diagnostic horizons and levels of certain chemicals
How are subgroups defined?
By a typic member and other members that have characteristics not shared with the typic member
How are families defined?
By properties like pH, texture, minerals, soil temp/depth
How are series defined?
Slight differences in texture or surface later. Very closely related soils
Which taxonomic group has the most detail?
Series
Which taxonic group has the least detail
Order
Which taxonomic group covers the most area?
Order
Which taxonomic group covers the least area?
Series
What is soil texture?
Proportion of sand/silt/clay
Size/distribution of soil particles
Why is soil texture useful?
Helps infer plant growth and suitability
Does not change easily
How does particle size relate to water movement speed and retention?
Increased size = more surface area; high water speed less retention
Describe sand
Gritty, visible to naked eye, round or angular
How does sand correspond to plant growth?
Low nutrients available to plants
Large pore space, well drained
Loose soil
Infertile and drought prone
Describe permeability and infiltration rates for sand
Low permeability and high infiltration
Describe silt
Smaller than sand, similar shape/comp, silky texture, low plasticity
How does silt relate to plant growth?
Large surface area = nutrient availability
Better water retention
What is piping and where does it occur?
Water process that washes away silt and develops macropores in subsurface
Difference between adsorption and absorption
Ad: molecules adhere (sand)
Ab: molecules drawn into (clay
What are clay particles? What are their traits
Colloids; do not readily settle out of water, shaped like flakes
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
List textures in order of water availability
Silt loam is high H2O availability
Sand is low availability
Clay is low availability
Define biogeochemical weathering
When primary materials are converted into insoluble or soluble forms
What are the 6 types of biogeochemical weathering?
Hydration, hydrolysis, dissolution, acid rxns, redox, complexation
Define hydration
Intact water molecules bind to mineral
Define hydrolysis
Molecules split, hydrogen replaces cation from mineral
Define dissolution
Minerals dissolved by hydrating cations and anions until they are dissociated and surrounded by water
Difference between oxidation and reduction
Oxidation is loss of electron, reduction is gain
Define acid reactions
Weathering accelerated by acids, increading hydrogren activity in water
Define redox
Minerals containing iron, manganese, sulfur exposed to air and gain/lose electrons
Define complexation
Organix reactions between different acids produce acid complexes and speed chemical rxns
What are the 4 soil forming processes
Transformation, translocation, additions, losses
Define transformation
Rock weathering and decomposition destroy some soil component and create others
Define translocation
In/organic materials move out/up/down profile
What are the 6 soil horizons?
Organic, A(topsoil), Eluviation, B(subsoil), C(parent), R(bedrock)
Define the O horizon
Organic material above mineral soil
Define A horizon
Topsoil- mix of mineral and OM
Define E horizon
Eluviation- light colored, water facilitated loss of material that leaves behind materials
Define B horizon
Subsoil - deposited minerals/salts, alteration to parent
Define C horizon
Parent rock - conconsolidated mineral horizon with no other horizon traits, retain parental structure
Define R horizon
Bedrock - continuous, consolidated rock without weathering
How are forest O horizons differentiated?
Litter, fermented, and humic based on level of decomposition
What are the 3 O subordinate horizons?
Oi, Oe, Oa
What is the Oi horizon?
Fibric, slightly recognizable OM
What is the Oe horizon?
Hemic, fine fragments, slight decomp, partially recognizable material
What is the Oa horizon?
sapric, high decomp, not recognizable material
