Chapter 8

Supplemental Information

Humus

• Plants drop leaves, twigs, and other material to the ground

• Over time, this leaf litter decomposes into dark, nutrient-rich organic matter (called humus) that is found in topsoil

Loam

• Loam is a mixture of soil particles, which makes it the ideal plant-growing medium

• It has relatively equal parts of clay, silt, and sand

• Loam has the benefits of each soil particle with few of the disadvantages

R Horizon

• The R Horizon is the bedrock that forms the parent material

• It is not soil and is located under the C horizon

Soil Profiles of the World

Tropical Rain Forest Soil

• Many essential elements are leached out by the heavy rainfall in tropical biomes, which reduces soil nutrient levels

• There are few nutrients more than 2 inches below the surface of the soil in tropical rainforests

• Organic matter from plants and animals that falls on the forest floor is rapidly decomposed by fungi and bacteria, and the resulting chemical compounds are quickly reabsorbed by the living plants

Acid Mine Drainage• At metal and coal mines, the target ore and

surrounding rocks are often rich in sulfide minerals

• When the mining process exposes the sulfides to water and air, they form sulfuric acid

• This acid can dissolve other harmful metals and metalloids (like arsenic) in the surrounding rock

• Acid mine drainage can have severe impacts on animals and plants

• Many impacted streams have a pH of 4 or lower, similar to battery acid