Environmental Information Series
Forestry Best Management Practices

Soil and Forests

Did you know that it takes, on average, about 180 years to form 1 cubic centimeter of soil? That is 2.3 times the life expectancy for Americans – all to produce a small quantity of soil that fits in a thimble! This fact takes on extra meaning when considering that soil, which is a product of the physical and chemical breakdown of rock, is an important resource for most living organisms. For example, it is a vital part of a forested ecosystem, providing a base for plant and treeerosion over a logging trail roots and, over time, supplying the nutrients and minerals necessary for living things to grow and thrive. Recognizing the importance of its function in forested ecosystems increases our appreciation of the amount of time required for nature to produce soil. In so doing, we are also compelled to consider how it can be conserved, because the thimble of forest soil we lose today won’t be replaced until just before the 23rd century.

Forest Soil Erosion

Undisturbed forest soil usually erodes at very slow rates, somewhere around 300 pounds per acre per year. Forest soil erosion rates are kept to a minimum, in large part, by natural mechanisms found on the forest floor and in the forest soil. The root structures of trees and plants help hold the soil together, while tree trunks, forest floor vegetation, and downed woody and leafy debris prevent surface water from gaining enough speed to remove large amounts of surface soil. However, human activities, such as timber harvesting and heavy recreation, can expose soil and potentially undermine the forest’s natural capacities for controlling erosion. Specifications for a water barLeft unchecked, soil erosion rates can increase dramatically to about 2700 pounds per acre per year in drier, more stable conditions. In wetter, less stable conditions, this number can be much higher. This increase can be roughly visualized as a jump from about two wheelbarrows of soil to a dump truck’s worth or even more.

Erosion and Water Quality

In most cases, eroded forest soil, whether a wheelbarrow or a dump truck’s worth, is eventually deposited in the nearest stream or lake. When kept to a natural rate, this sedimentation typically has little impact on a stream or lake’s water quality. On the other hand, when erosion rates skyrocket, soil can overwhelm streams and lakes, clouding the water and choking out the fish and other organisms living there. However, researchers have found that by using a set of basic, on-the-ground techniques known as Best Management Practices, we can help reduce soil erosion and subsequently protect water quality by controlling the flow of surface water over exposed areas.

What are Forestry Best Management Practices?

Forestry Best Management Practices (BMP) are a set of preventative measures that help control soil erosion resulting from human disturbance. These simple and inexpensive practices have become widely used as a means to divert surface water into undisturbed areas before it gains sufficient speed for large soil removal. Once diverted, the natural control mechanisms of an undisturbed forest floor work to stop rapid surface water flow, absorb it, and recapture any removed soil. Techniques such as water bars and diversion ditches are BMPs that control surface water flow and help stabilize disturbed forest floors quickly by conserving exposed soil for future vegetative growth. BMPs also provide guidelines for planning and conducting forest activities in a manner such that water bodies, wet and saturated areas, and Surface water flow checked by a water bar; soil erosion minimized and vegetative growth maximizedsteep and unstable slopes are avoided to reduce instability and the potential for increased erosion. Most BMP manuals contain specific sections addressing these planning considerations. In addition, foresters are available in your region to provide advice and answer questions about using BMPs to conserve this critical natural resource.

Helpful links:

BMP information (New York State Department of Environmental Conservation)
Watershed information (U.S. Environmental Protection Agency)
Forest Information (forestinfo.org)

Text prepared by John F. Munsell, Research Project Assistant, Department of Forest and Natural Resource Management