Erosion and Decomposition

Erosion is a natural process that occurs in the soil ecosystem. Erosion occurs when water washes away soil. To keep soil from disappearing completely, though, some other process must balance erosion. Soil needs a way to make more soil. That way is decomposition.

Decomposition happens when soil organisms such as bacteria and fungi break down organic matter. By feeding on leaf litter, decaying wood and other organic matter, soil bacteria and fungi "grind up" dead organic matter into small pieces, letting out the nutrients into the soil. These nutrients help to make humus, the dark, nutrient-rich part of the soil. Thus, decomposition not only provides food for these organisms, it also helps to create more soil.

Humus is usually found in the topsoil, which is the top-most layer of the soil: the soil you see every day. Humus is often referred to as "new soil," since it is newly created from decomposition.

This new soil is extremely important. It provides nutrients for the plants, shrubs and trees that grow on its surface. The new soil also helps support many of the animals that live underground, such as worms and ants, by providing these organisms with a place to live and a nutrient-rich food supply.

By making more soil through decomposition, soil helps to regenerate a living space for all the animals it supports. Decomposition also helps to prevent water shortages, ecosystem damage, and soil loss.

Application 1

Soil Damage

As you have learned, the many different aspects of soil are all interconnected. For this reason, damage to the soil will have a tremendous impact on the soil ecosystem and the organisms that live in it.

Many different elements in the environment may damage soil such as erosion, pollution and various forms of soil degradation. When too much water erosion occurs in a specific area, for example, the water washes away many of the nutrients in the soil. The few nutrients remaining in the soil are no longer enough to support the microscopic organisms in the soil, causing many of them to die.

Since these organisms are the ones that create more soil, there are no longer enough micro-organisms to decompose the organic materials in the soil. Thus, decomposition cannot take place, leading to no regeneration of soil. Therefore, once soil is damaged it cannot be replaced, thereby classifying soil as a non-renewable resource.

When soil becomes damaged, there are implications for other characteristics of the soil. First, the lack of regeneration of the soil does not provide a renewable home for the organisms that live within the soil. Secondly, the soil does not provide nutrients for these organisms and the plants, shrubs and trees that grow on its surface. Third, too much erosion can cause problems such as water shortages, ecosystem damage, and soil loss.