Unit 5 - Forest Protection

Lesson 9: Soil Conservation

Healthy soil, an absolutely critical component of the forest ecosystem, is made up of inorganic material, water, air, and billions of organisms. Trees rely on the soil to provide stability, nutrients, and water.

A deep layer of soil stabilizes the tree by providing a firm foundation. Roots will often penetrate the soil to a depth of 4 meters, although sometimes they may extend down into the soil even further.  In addition, lateral roots can often extend 11 meters or more in each direction.

Soil also provides the tree with nutrients. Insects, fungi, and bacteria that live in the soil are responsible for breaking down dead plants and animals. This process of decomposition releases nutrients back into the soil, which can then be absorbed by the roots of trees and other forest vegetation.

Forest soil provides trees with water by acting like a sponge. It absorbs precipitation and holds it until it is needed by trees and other forest vegetation. Without a healthy layer of soil, available water simply runs off quickly into streams.


Courtesy of How a Tree Grows,
FS-32, 1970, USDA Forest Service, by Elliott Menashe (www.greenbeltconsulting.com) 2004
We have just discussed the many ways in which trees depend on soil, but the soil also needs the trees. Without tree roots to hold the soil in place, it is very subject to erosion by water. Because of this, protection of soil is an important component of sustainable forest management. During forestry operations, it is critical to conserve the soil layer as much as possible