pedogenesis

Pedogenesis or soil evolution (formation) is the process by which soil is created.^[1] It is the major topic of the science of pedology, whose other aspects include the soil morphology, classification (taxonomy) of soils, and their distribution in nature, present and past (soil geography and paleopedology).

Climate

Climate regulates soil formation. Soils are more developed in areas with higher rainfall and more warmth. The rate of chemical weathering increases by 2-3 times when the temperature increases by 10 degrees Celsius (18 °F). Climate also affects which organisms are present, affecting the soil chemically and physically (movement of roots).

Organisms

The organisms living in and on the soil form distinct soil types. Coniferous forests have acidic leaf litter and form what are known as inceptisols. Mixed or deciduous forests leave a larger layer of humus, changing the elements leached and accumulated in the soil, forming alfisols. Prairies have very high humus accumulation, creating a dark, thick A horizon characteristic of mollisols.

Parent Material

The rock from which soil is formed is called parent material. The main types are: aeolian, glacial till, glacial outwash, alluvium, lacustrine parent material and residual parent material, or bedrock.

Pedologists use the following generic functional relationship for understanding soil formation:^[2]

s = f (cl, o, r, p, t, ...)

where s - soil properties; cl - regional climate; o - potential biota, r - topography; p - parent material; t - time; ... - additional variables.

Examples

A variety of mechanisms contribute to soil formation, including siltation, erosion, overpressure and lakebed succession. A specific example of the evolution of soils in prehistoric lake beds is in the Makgadikgadi Pans of the Kalahari Desert, where change in an ancient river course led to millennia of salinity buildup and formation of calcretes and silcretes.^[3]

See also

• CLORPT
• Parent material
• Soil horizon
• Soil production function
• Topography

References

• Stanley W. Buol, F.D. Hole and R.W. McCracken. 1997. Soil Genesis and Classification, 4th ed. Iowa State Univ. Press, Ames ISBN 0-8138-2873-2
• C. Michael Hogan. 2008. Makgadikgadi, The Megalithic Portal, ed. A. Burnham [1]
• Francis D. Hole and J.B. Campbell. 1985. Soil landscape analysis. Totowa Rowman & Allanheld, 214 p. ISBN 0-86598-140-X
• Hans Jenny. 1994. Factors of Soil Formation. A System of Quantitative Pedology. New York: Dover Press. (Reprint, with Foreword by R. Amundson, of the 1941 McGraw-Hill publication). pdf file format.
• Ben van der Pluijm et al. 2005. Soils, Weathering, and Nutrients from the Global Change 1 Lectures. University of Michigan. Url last accessed on 2007-03-31

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