Soil forms when weathered parent material interacts with environment. Soil Formation Soil forms when weathered parent material interacts with environment.
Soil environment includes: Climate and weather Animals Microbes Human use Hazards ( natural and unnatural ) Topographical relief
Show video of soil carbonic acid extracting minerals from soil
rates of soil formation Slow--------------------------------------Fast ~ 1 cm/1000 yr ~ 30cm/50yr
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)
1. CLIMATE 2. ORGANISMS 3. RELIEF 4. PARENT MATERIAL 5. TIME
1. CLIMATE …determines speed, character of soil development: type and rate of weathering living organisms and plants found in an area
components of 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
(Fig. 2.15)
Effective precipitation -a) seasonal distribution -b) temperature, evaporation -c) topography -d)permeability
a) Seasonal distribution of precipitation: Location B 600 mm/yr Location A 600 mm/yr 100mm 50mm 6 rainy months only Every month
b) Temperature and evaporation: Location A hot Location B cool High evapotranspiration Low evapotranspiration 600 mm 600 mm Lower effective ppt Higher effective ppt
Topography: concave or bottom of slope (receiving) level slope
Permeability:
2. Organisms plant and animal (Living plants and animals on and in soil) -sources of organic matter -nutrient recycling -vegetation prevents erosion -type of vegetation influences soil type -base pumping -
Type of vegetation influences soil type
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
Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water
crotovinas
night crawlers and water
Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water Microanimals (nematodes, protozoa)
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
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
3. Relief/Topography important for rate of runoff, erosion, drainage
Flat valley floors and flat ridge tops: soil accumulates; (deepening>removal) Slopes: (removal> deepening)
Vertical Zonation soils, climate, vegetation change with elevation
4. Parent Material Determines texture, types of weathering, mineral make-up
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
Physical: Chemical (biogeochemical):
Chemical (biogeochemical): Physical: 1. Freeze/thaw Chemical (biogeochemical):
Freeze / Thaw
Chemical (biogeochemical): Physical: 1. Freeze/thaw 2. Exfoliation Chemical (biogeochemical):
2. Exfoliation
Chemical (biogeochemical): Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion Chemical (biogeochemical):
3. Abrasion (wind, water, ice)
water
ice
Chemical (biogeochemical): Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging Chemical (biogeochemical):
4. Salt Wedging
Chemical (biogeochemical): 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
5. Time Amount of time soil has been exposed to weathering and soil forming processes influences soil properties. Jenny’s staircase Ohio/Ky.
4 soil forming processes: (pedogenic) Transformation
4 soil forming processes: Transformation Translocation
4 soil forming processes: Transformation Translocation Addition
4 soil forming processes: Transformation Translocation Addition Loss