Soil Forming Factors

Figure 1. Summary diagram showing climate, parent material, organisms and topography interacting through time to form soil (from E.A. FitzPatrick, 2006. Factors of soil formation: time. In: Certini G., Scalenghe R. (eds.) Soils. Basic Concepts and Future Challenges. Cambridge University Press, Cambridge, UK)

Despite often a state factor affects one or more of the others (e.g. topography  climate, climate and parent material  biota, et cetera), in many locations factors may vary independently of each other. As a result, in nature, through judicious site selection, the influence of a single factor can be observed and quantified. These observational studies are called sequences: lithosequence, climosequence, toposequence, biosequence, and chronosequence.

In an increasingly populated planet, humans must be necessarily included among the state factors of pedogenesis because they take on increasing significance as an ecosystem variable. Jenny originally considered humans under the biotic factor because, like other biota, humans contain a genetic component or genotype. However, unlike the other organisms that are not endowed with the ability to reason, humans possess a cultural component that varies from society to society and which operates independently of genotype, arguably making them worthy of a separate factorial treatment. Nowadays, humans influence ecological processes on a global scale, sometimes on par with the role of climate, geological forces and astronomical variations. The anthropogenic factor (h) can affect soil formation by a plethora of different interventions, such as deforestation and forestation, grazing, agriculture, urbanization, construction of turnpikes and landfills, induced fires and floods, mining, pollution, bombing, burial of pipelines or cables. Global climate change is under suspicion to be caused by overexploitation of fossil fuels and mismanagement of forest resources.
Additional natural factors that could contribute to a different degree to pedogenesis are spontaneous fires, earthquakes, tsunami, volcanism, and impacts of meteorites.