Woodland Soil Basics

A site's soil characteristics have a major impact on the type and quality of trees produced. In general, soil type is classified by its texture, or size of soil particles, porosity and fertility. Further classification of a soil’s quality is determined by measuring its chemical and biological indicators. A soil’s infiltration rate and aggregate structure and stability help determine the soil’s water-holding capacity, while its organic matter will indicate the soil’s overall fertility level. Generally, fine-textured (clay) and medium-textured soils have a greater nutrient content than course or sandy soils. The soil’s porosity, or measure of the spaces between particles, and aggregate structure will determine how quickly water drains from the site. Clay soils can hold more water, but absorb the water more slowly because of its low saturation point. Soils with a high percentage of silt have the most favorable texture for moisture absorption and drainage. For more information on soil types and to get your soil tested, contact your county UW-Extension office. Soil maps are available from your local U.S. Natural Resources Conservation Service office.

Soil compaction, caused by heavy machinery or traffic in the woods, can cut off water and oxygen supplies to tree roots , essentially suffocating the roots . A sign of soil compaction is dying leaves on mature trees and dying branches on younger trees, but sometime the only indication is reduced growth not caused by other factors. Soil compaction can be more severe with wet clay or silt soils. Avoid using heavy machinery on the site unless the ground is frozen. Tampering with soil levels around the base of the tree will also affect growth levels or even contribute to tree death caused by weakened or exposed roots. For more information on soils, refer to "Forest soils of Wisconsin", Wisconsin Woodlands G3452.

Using Best Management Practices to Conserve Soil
The primary concern in protecting soil is to make sure areas where soil is exposed are covered as soon as possible. Timber harvests may require either temporary or permanent road construction, which exposes areas to soil erosion.

Here are some common soil stabilization practices:

-- Use mulch and/or seed where necessary. Mulch can be straw, woodchips or bark and is applied after an area is seeded. Netting may be necessary to hold mulch on sloped lands.

-- Install sediment control structures to control runoff and to trap sediment until vegetation is established. Sediment control structures include straw bale fencing, silt fencing and sediment traps.

For a complete discussion of soil stabilization techniques during road construction, refer to the Wisconsin Construction Site Erosion Control Handbook, available from DNR Service Centers or by calling DNR Document Sales, 608-266-3358 or from the Wisconsin Department of Transportation, 608-267-3766.

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