This unique addition to reference literature provides an introduction to the major concepts and contemporary issues that are essential for students of environmental science and environmental studies to know. With over 200 entries authored by world-class names like Anthony Brazel, John Day and Edward Keller, this text is divided into six sections: Environmental Science, Environments, Paradigms & Concepts, Processes & Dynamics, Scales & Techniques, and Environmental Issues.  

Soil Profiles

Soil profiles

Soil formation begins with the breakdown of rock into regolith. Continued weathering and soil horizon development process leads to the development of the vertical display of soil horizons, which is called the soil profile (Fig. 27).

Figure 27 An idealized soil profile

(from I.G. Simmons)

O Horizon: At the top of the profile is the O horizon, which is mostly organic matter: in a forest this would be mostly leaf litter, on rangeland it would be dead grass and animal faeces. It becomes decomposed and is called humus. The humus transfers nutrients such as nitrogen and potassium, to the soil, aids soil structure and keeps up the levels of soil moisture.

A1 Horizon: Beneath the O horizon is the A1 horizon. In this horizon organic material ...

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