Chapter 12. Chapter 12: Grasslands

Interactive Study Guide
false
true

Guiding Question 12.4

What is involved in the formation of soil and how does land use affect it?

Why You Should Care

Despite its crucial importance to our lives, soil is an often overlooked and underappreciated resource. It is formed of minerals (compounds made of elements like silicon, iron, carbon, and oxygen), organic matter (the decayed remains of organisms, mostly plants), water, and air. The mineral portion of soil is usually the largest and comes from rock as it weathers, or is broken into small particles. Weathering can happen as a result of glaciation, freezing and thawing cycles, pioneer organisms like lichens, chemical reactions with surface water or rain, and so on.

Land used for grazing or raising crops can damage soil or cause it to be lost if either is done too intensively. As previously mentioned, overgrazing can kill grass and lead to destabilization of soil. Overtilling soil for planting crops brings stabile soil to the surface, which allows it to dry out and possibly be carried away by wind or rain. If this degradation is severe enough, the land may be rendered unsuitable for growing crops or raising livestock for decades or longer.

1.

Thought Question: The organic matter content of the A horizon in grassland soils is usually much higher than in forest soils. Can you form an explanation for this? (Hint: Where does the organic matter come from?)
Forest organic matter comes from fallen leaves. They begin decomposing on the surface of the soil before they are incorporated into it, so less organic matter is added. Most of the organic matter in grassland soils comes from the grasses’ roots, which are constantly growing and being replaced. This adds organic matter directly to the A horizon.

Activity results are being submitted...