Soil Formation

1. Soil Formation Soil forms when weathered parent material interacts with environment.

2. rate of formation Slow--------------------------------------Fast ~ 1 cm/1000 yr ~ 30cm/50yr

3. Hans Jenny • 1941: soil is open system, properties are functionally related; system changes when property(ies) change(s). • Jenny’s CLORPT equation s = ƒ (cl, o, r, p, t)

4. 1. Climate... …determines speed, character of soil development: a. type and rate of weathering b. living organisms and plants found in an area

5. 1. Climate • 1. Temperature • -for every 10°C , biochemical rxn rates 2X • 2. Effective precipitation • (water that moves through entire soil column, including regolith) • -depth of water = depth of weathering • -water moves soluble & suspended materials

6. (Fig. 2.15)

7. Effective precipitationp. 42 -seasonal distribution -temperature, evaporation -topography -permeability

8. Seasonal distribution of precipitation: Location B 600 mm/yr Location A 600 mm/yr 100mm 50mm 6 rainy months only Every month

10. Temperature and evaporation: Location A hot Location B cool High evapotranspiration Low evapotranspiration 600 mm 600 mm Lower effective ppt Higher effective ppt

11. Topography: concave or bottom of slope (receiving) level slope

12. Permeability:

13. 2. Organisms (Living plants and animals on and in soil) -type of vegetation influences soil type -base pumping -sources of organic matter -nutrient recycling -vegetation prevents erosion

14. Type of vegetation influences soil type

15. Base pumping Deciduous trees are more effective base pumpers than conifers . -needles are hard to break down -basic cations leach away: soil is acidic -deciduous litter is easy to break down -cations (bases) are released so surface soils are not acidic

16. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water

17. crotovinas

18. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa)

19. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa) • Macroplants (the green plants) • provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion

20. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa) • Macroplants (the green plants) • provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion • Micro “plants” (fungi, bacteria, actinomycetes, algae) • decomposers

21. 3. Relief/Topography • important for rate of runoff, erosion, drainage

23. Flat valley floors and flat ridge tops: soil accumulates; (deepening>removal) Slopes: (removal> deepening)

24. Vertical Zonation • soils, climate, vegetation change with elevation

25. 4. Parent Material • Determines texture, types of weathering, mineral make-up

26. weathering • Physical (Mechanical): disintegration of parent material; increases surface area: • surface area increases by same factor as particle size decreases • Chemical (Biogeochemical) : primary minerals are broken down and secondary minerals are formed

29. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging Chemical (biogeochemical): 1. Hydrolysis: minerals react with H2O H+ replace soluble parts; OH- combine with mineral cations 2. Hydration: mineral combines with H2O 3. Oxidation: mineral combines with O2 (lose electron) Reduction: loss of O2 (gain electron) 4. Carbonation: oxides combine with acids to make carbonates 5. Complexation: organic acids form organic complexes with metal cations

31. Freeze / Thaw

34. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging Chemical (biogeochemical): 1. Hydrolysis: minerals react with H2O H+ replace soluble parts; OH- combine with mineral cations 2. Hydration: mineral combines with H2O 3. Oxidation: mineral combines with O2 (lose electron) Reduction: loss of O2 (gain electron) 4. Carbonation: oxides combine with acids to make carbonates 5. Complexation: organic acids form organic complexes with metal cations

35. 2. Exfoliation

38. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging Chemical (biogeochemical): 1. Hydrolysis: minerals react with H2O H+ replace soluble parts; OH- combine with mineral cations 2. Hydration: mineral combines with H2O 3. Oxidation: mineral combines with O2 (lose electron) Reduction: loss of O2 (gain electron) 4. Carbonation: oxides combine with acids to make carbonates 5. Complexation: organic acids form organic complexes with metal cations

39. 3. Abrasion (wind, water, ice) wind

41. water

42. ice

43. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging Chemical (biogeochemical): 1. Hydrolysis: minerals react with H2O H+ replace soluble parts; OH- combine with mineral cations 2. Hydration: mineral combines with H2O 3. Oxidation: mineral combines with O2 (lose electron) Reduction: loss of O2 (gain electron) 4. Carbonation: oxides combine with acids to make carbonates 5. Complexation: organic acids form organic complexes with metal cations

44. 4. Salt Wedging

45. hydrolysis In lab: Apatite Ca5(PO4)F Ca5(PO4)F + H2OCa(OH)2+HPO4 basic BLUE PINK

46. carbonation In lab: H2O + CO2 H2CO3 REDYELLOW

47. 5. Time • Amount of time soil has been exposed to weathering and soil forming processes influences soil properties. • Jenny’s staircase • Ohio/Ky.

49. 4 soil forming processes:(pedogenic) Transformation