Natural Resources and Ecology
Natural Resources and Ecology
The Formation of Soils
Unit 2 – Lesson 2.1 Soils and Land
Soil Forming Factors
Five factors acting together influence the
formation of soil:
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Parent Material
Climate
Organisms
Topography
Time
Parent Material
• Original mineral from which soil develops
• Influences soil fertility and texture
• Sources of parent material
– Minerals and rocks
– Deposits – glacial, wind, water, and organic
Climate
Climate and location affect the rate of
weathering.
• Temperature
• Rainfall
Weathering breaks down rock into smaller
fragments and eventually down to small
particles.
Organisms
• Macro-organisms (living and dead)
– Source of organic matter
– Large plants and animals
• Microorganisms
– Microscopic plants and organisms
– Primary decomposers of organic material
Topography
• Affects distribution of soil particles and
water
• Slope causes water runoff and potential
erosion
• Water moves smaller soil particles down
the slope
Time
• Highly variable rate of formation
• Different types of parent material weather
at different rates
• Climate and topography also influence
rate of soil formation
Erosion
• The opposite of soil formation is erosion,
which has a detrimental effect on soil.
• Erosion is a natural process.
• Erosion comes in two forms:
• Water
• Wind
Erosion Happens
In what circumstances is soil erosion more
likely to happen?
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Steep ground
Excessive water movement
Little or no vegetation
Wind blowing across bare soil
Soil Development
There are four main ways that the
process of soil formation occurs:
Addition – accumulation or deposition
Reduction – leaching and erosion
Translocation – movement within soil profile
Transformation – soil changes in place by
weathering or microorganism conversion
References
Burton, L. D. (2009). Environmental science:
Fundamentals and applications. Clifton Park,
NY: Delmar Cengage Learning.
Huddleston, J. H., & Kling, G. F. (1996). Manual for
judging Oregon soils. Corvallis, OR: Oregon
State University.
Parker, R. (2010). Plant and soil science:
Fundamentals and applications. Clifton Park,
NY: Delmar.