Ren R 441 up to end of chernozems

  1. 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
  2. when only one soil forming factor changes, a _____________ develops
    sequence of related soils
  3. sequence: difference in PM
    lithosequence
  4. sequence: difference in age
    Chronosequence
  5. sequence: difference in slope
    Toposequence
  6. sequence: difference in organisms
    biosequence
  7. 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
  8. horizons
    • layers of soil parallel to land surface
    • unique colour, structure, chemistry, etc
  9. soil profile
    • vertical exposure of earth's crust
    • contains all horizons
  10. soil solum
    • an incomplete soil profile
    • genetic horizons
    • usually the surface and B horizons
    • lower limit: C horizon
    • depth variable to C horizon
  11. pedon
    • smallest volume that can be called soil
    • 3D
    • lower limit is C horizon
    • lateral dimensions depend on cyclic properties
  12. soil series
    • grouping of v similar pedons
    • conceptual entity
    • essentially alike in all major profile properties
    • defined in map legends, use place names
  13. polypedons
    • contiguous pedons
    • real soil body on the landscape
    • correspond to soil series
  14. 5 categories in the Canadian System of Soil Classification
    Order - Great Group - Subgroup - Family - Series
  15. 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
  16. soil great group
    • subdivisions of orders
    • based on properties reflecting the strength of the dominant process or contribution of an additional process
  17. 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
  18. soil family
    • subdivisions of subgroups 
    • based on nature of PM, soil pH, soil climate
  19. 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
  20. where do we find chernozems?
    • native and tame grasslands
    • cultivated lands, almost all the major cities (v fertile land)
  21. diagnostic horizon of chernozems
    • Ah horizon
    • at least 10cm thick, if Ap at least 15cm
  22. colour of chernozems
    • value: < 5.5 dry or 3.5 moist
    • chroma: < 3.5 moist
  23. value of chernozems?
    • at least one unit darker than the C horizon
    • more OM in the A horizon than the C horizon
  24. organic carbon of a chernozem
    • 1-17%, C:N < 17:1
    • this C:N ratio favors decomposition, nutrient cycling
  25. % base saturation of chernozems
    • >80%
    • pH around neutral
    • Ca2+ dominant
  26. mean annual soil temperatures of chernozems?
    • > 0°C and < 5.5°C
    • seasonality to creating a chernozem
  27. climates chernozems are found in?
    sub-humid to semi-arid climates
  28. 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
  29. distribution of chernozems in Canada
    • well to imperfectly drained sites 
    • xerophytic (little/no water), mesophytic grasses/forbes of grassland 
    • grassland forest transition areas
  30. 4 great groups of chernozems
    • brown 
    • dark brown
    • black
    • dark gray
  31. distribution of the chernozem great groups influenced by ______
    latitude, altitude, aspect
  32. brown chernozems
    • lightest one
    • veg: short grasses/forbs -> Xenophytic grasses
  33. dark brown chernozems
    • bit darker than brown (lower colour value)
    • veg: mid-grass/forbs -> getting more moisture than brown
  34. 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
  35. 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
  36. chernozem subgroups
    • rego
    • calcareous
    • orthic
    • eluviated
    • solonetzic
    • vertic
    • gleyed
  37. chernozem rego subgroup
    • no B horizon or B<5cm
    • young soil
  38. 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
  39. chernozem orthic subgroup
    • has a Bm 
    • "generic" category
    • "modified" horizon, modification of Ca2+ in PM
  40. chernozem eluviated subgroup
    • has an Ae or Ahe
    • eluviation
  41. 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)
  42. chernozem vertic subgroup
    • has ss andn possibly Bvj
    • Bss, Css=slick n slide
    • v= vertic
    • j= jr
  43. chernozem gleyed subgroup
    • has a gj within top 50cm
    • gj=juvenile expression of a gleyed soil
  44. main soil forming factors of chernozems: climate
    • cold, subarid to subhumid, no net percolation
    • P:E < 1
  45. main soil forming factors of chernozems: organism
    mainly grasses (extensive root biomass contribute to OM accumulation)
  46. main soil forming factors of chernozems: relief
    upper and mid slope so soil is well to imperfectly drained
  47. main soil forming factors of chernozems: parent material
    usually calcareous glacial till
  48. main soil forming factors of chernozems: time
    relatively young, formed after last glaciation (~11 000 BP)
  49. major processes formation chernozems
    • Ah horizon: melanization: formation of humus/accumulation
    • redistribution of bases
    • Bm and Cca horizons: redistrubution of bases
Author
hcunning
ID
323323
Card Set
Ren R 441 up to end of chernozems
Description
lectures 1-3, chernozems
Updated