Soils: Profiles and Processes

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Soils: Profiles and Processes (20:00)
Item# 801

This program looks at the way soils can vary even within a small area of a forest. A well-developed podzol is examined in detail, with samples taken from the center of each horizon and then analyzed for organic content, soil acidity, mineral content, and particle size distribution. The measurements and analyses demonstrate why three soil profiles can be so very different in closely contiguous areas, with the same underlying sand, the same climate, and similar if not identical vegetation. The differences are due not to soil types, but to different processes at work. (20 minutes)

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Segments in this Video - (6)

1. Soil Analysis: Field Work (01:43)
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A soil profile in a forest displays several distinct horizons, from leaf litter and humus at the top to sand at the base. Samples taken from each layer are identified for analysis in the laboratory.

2. Soil Analysis: Organic Content (02:42)

To establish its organic content, a weighed sample of soil is heated to a temperature at which the organic material ignites, producing weight loss that is proportional to the organic content of the sample.

3. Soil Analysis: pH and Total Acidity (04:16)

Acidity controls reactions that take place in soil; it is a reflection of the amount of hydrogen available to enter into reactions. Acidity can be measured by calculating the concentration of hydrogen.

4. Soil Analysis: Minerals (02:52)

Analysis of minerals and their distribution throughout the layers of a podzol indicates that leaching is the dominant process at work in the area from which the soil samples were taken.

5. Soil Analysis: Particle Size Distribution (02:06)

Analysis of particle sizes in layers of a podzol shows fine material has been washed out of the horizon below the humus layer and redeposited, indicating that leaching is the dominant process.

6. Soil Analysis: Changes in Soil Profiles (04:57)

In areas where vegetation of a forest changes dramatically, so too does the soil. Even where vegetation and climate are identical, soil profiles may differ because different processes are at work.

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