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ex. of soil forming processes
- water flow (infiltration, percolation, etc.)
- chemical and physical weathering
- biogeochemical cycles
- erosion, deposition
- bioturbation
- freeze-thaw, shrink-swell
- solute transport
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when only one soil forming factor changes, a _____________ develops
sequence of related soils
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sequence: difference in PM
lithosequence
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sequence: difference in age
Chronosequence
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sequence: difference in slope
Toposequence
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sequence: difference in organisms
biosequence
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definition of soil
natural body consisting of layers (horizons) of mineral and/or organic constituents of variable thickness, which different from their parent materials in their morphological, physical, chemical, and minerological properties and biological characteristics
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horizons
- layers of soil parallel to land surface
- unique colour, structure, chemistry, etc
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soil profile
- vertical exposure of earth's crust
- contains all horizons
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soil solum
- an incomplete soil profile
- genetic horizons
- usually the surface and B horizons
- lower limit: C horizon
- depth variable to C horizon
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pedon
- smallest volume that can be called soil
- 3D
- lower limit is C horizon
- lateral dimensions depend on cyclic properties
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soil series
- grouping of v similar pedons
- conceptual entity
- essentially alike in all major profile properties
- defined in map legends, use place names
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polypedons
- contiguous pedons
- real soil body on the landscape
- correspond to soil series
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5 categories in the Canadian System of Soil Classification
Order - Great Group - Subgroup - Family - Series
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soil order
- 10 of them in the CSSC
- taxa for soils formed under similar soil forming factors
- use diagnostic horizons as indicator of major pedogenic process
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soil great group
- subdivisions of orders
- based on properties reflecting the strength of the dominant process or contribution of an additional process
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soil subgroup
- subdivisons of great groups
- based on kind/arrangement or horizons that indicate one of: the modal concept, intergrades, degree of development, special features
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soil family
- subdivisions of subgroups
- based on nature of PM, soil pH, soil climate
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soil series
- subdivisions based on detailed pedon features like horizon thickness, texture, structure
- series are conceptual and equate to the polypedon on the landscape scale
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where do we find chernozems?
- native and tame grasslands
- cultivated lands, almost all the major cities (v fertile land)
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diagnostic horizon of chernozems
- Ah horizon
- at least 10cm thick, if Ap at least 15cm
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colour of chernozems
- value: < 5.5 dry or 3.5 moist
- chroma: < 3.5 moist
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value of chernozems?
- at least one unit darker than the C horizon
- more OM in the A horizon than the C horizon
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organic carbon of a chernozem
- 1-17%, C:N < 17:1
- this C:N ratio favors decomposition, nutrient cycling
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% base saturation of chernozems
- >80%
- pH around neutral
- Ca2+ dominant
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mean annual soil temperatures of chernozems?
- > 0°C and < 5.5°C
- seasonality to creating a chernozem
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climates chernozems are found in?
sub-humid to semi-arid climates
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other horizons characteristic of a chernozem
- Bm (modified) usually present
- may have Bt (translocate [clay]) or Btj
- Cca (secondary calcium/carbonate) or Ck (priary carbonate) at variable depth
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distribution of chernozems in Canada
- well to imperfectly drained sites
- xerophytic (little/no water), mesophytic grasses/forbes of grassland
- grassland forest transition areas
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4 great groups of chernozems
- brown
- dark brown
- black
- dark gray
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distribution of the chernozem great groups influenced by ______
latitude, altitude, aspect
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brown chernozems
- lightest one
- veg: short grasses/forbs -> Xenophytic grasses
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dark brown chernozems
- bit darker than brown (lower colour value)
- veg: mid-grass/forbs -> getting more moisture than brown
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black chernozems
- has more OM deposited, faster process which allows more OM to be deposited into A horizon
- darkerest great group
- veg: tall grass/forbs, discontinuous aspen -> pasture, cereals, oilseeds
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dark gray chernozems
- transitional to gray luvisol
- darker than browns, lighter than black
- often degraded A (Ahe) -> generally have eluviation
- veg: mosaic of aspen groves and prairie patches
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chernozem subgroups
- rego
- calcareous
- orthic
- eluviated
- solonetzic
- vertic
- gleyed
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chernozem rego subgroup
- no B horizon or B<5cm
- young soil
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chernozem calcareous supgroup
- has Bmk horizon
- when there's lots of Ca2+ in the soil, not much is happening as Ca2+ takes up lots of the action sites
- lots of carbonates, ex. PM has lots of carbonates, is retained in the soil
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chernozem orthic subgroup
- has a Bm
- "generic" category
- "modified" horizon, modification of Ca2+ in PM
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chernozem eluviated subgroup
- has an Ae or Ahe
- eluviation
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chernozem solonetzic subgroup
- has a Bnj or Btnj
- n=sodium (think Na)
- t=translocate
- j=juvenile (not a true n because its not a true solonetzic)
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chernozem vertic subgroup
- has ss andn possibly Bvj
- Bss, Css=slick n slide
- v= vertic
- j= jr
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chernozem gleyed subgroup
- has a gj within top 50cm
- gj=juvenile expression of a gleyed soil
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main soil forming factors of chernozems: climate
- cold, subarid to subhumid, no net percolation
- P:E < 1
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main soil forming factors of chernozems: organism
mainly grasses (extensive root biomass contribute to OM accumulation)
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main soil forming factors of chernozems: relief
upper and mid slope so soil is well to imperfectly drained
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main soil forming factors of chernozems: parent material
usually calcareous glacial till
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main soil forming factors of chernozems: time
relatively young, formed after last glaciation (~11 000 BP)
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major processes formation chernozems
- Ah horizon: melanization: formation of humus/accumulation
- redistribution of bases
- Bm and Cca horizons: redistrubution of bases
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