How does climate affect soil formation if precipitation is greater than evaporation
Leaching and illuviation occurs
How does climate affect soil formation if precipitation is less than evaporation
There is a higher concentration of salts
What does water availability affect in terms of soil formation? (2)
- intensity and depth of weathering
- plant types and cover
How does climate in terms of temperature affect soil formation?
It determines the rate of chemical and biochemical reactions
There are consequences for weathering, nutrient availability, decomposition and C cycles
How does more vegetation cover affect soil formations?
More vegetation provides more organic input
Roots create channels for water infiltration and bind soil to reduce erodibility
Canopy alters microclimate
How do types of vegetation influence soil processes?
- chemistry and amount of organic input- decomposition rates and soil fauna and microbial community, nutrient cycling
- water availability, water storage, likelihood of overland flow generation
What organisms are involved in processes of bioturbation
Insects, mammals, gastropods, earthworms
What does bioturbation do? (2)
- It creates channels for air and water
- helps form horizons and mix regolith with organic matter
What do heterotrophic bacteria and fungal do?
Decompose organic compounds
And releases plant availability (inorganic forms of nutrients and CO2)
What is the direct effect of relief (topography) on soil formation?
Gradient affects runoff, infiltration, erosion, mass movements and soil thickness
What is the indirect effect of relief (topography) on soil formation?
Altitude affects climate
Aspect is important for microclimate and vegetation
What does Geoffrey Milne believe about slope scale variations?
There is a regular repetition of sequence in soil profiles in down slopes across East Africa.
He thinks a distinct word is needed in referring to this phenomenon
What is the name of the idea that there are regular repetition of sequences in soil profiles
The Catena
What is meant by parent material
Bedrock, glacial depositions or alluvial material
What affect does parent material have on soil? (5)
- colour
- texture
- structure
- mineral composition
- permeability
What is meant by soil texture?
The relative amount of sand, silt and clay sized particles
Why is soil texture so important?
It affects the reactivity and nutrient retention
What is the cation exchange?
Interchange between cations in solution and changed surface of soil particle
What is the cation exchange capacity?
The sum of exchangeable cations that a soil can absorb
Why is soil texture important in terms of water movement?
-water moves rapidly and is poorly retained in coarse-textured sandy soils
- water moves slowly and is strongly retained in fine-textured clayey soils
What happens to soils over time?
- soils develop slowly
- gradually changing due to additions, transformation, translocation and losses
- most British soils are young but in central Africa and Australia they are old
As soils age they deepen and form horizons
Is the soil in Britain young or old?
Young
Is the soil is central Africa young or old?
Old
Is the soil in Australia young or old?
Old
