Russ Hatz

It doesn't matter how you make your living. It doesn't matter if you ski, golf, hike or watch TV for recreation. You depend upon and use wood fiber produced by trees. And every tree in every forest in every country grows in soil.

Soil surveys published by the Natural Resources Conservation Service (NRCS) can help you increase the productivity of your forest. They can help you identify areas that are in need of fertilization, areas that are susceptible to landslides and erosion after road building, or areas that may require special efforts to harvest or reforest. Soil survey information can also help you manage your forest for wildlife habitat and recreation activities.

As a family forest owner, you want the greatest return for your long-term investment. Because your forest's ability to produce wood fiber is closely related to its soil properties, detailed knowledge of its soil can help you manage your tree farm more efficiently. For example, some soils, formed from deposits of volcanic ash, can hold high amounts of water. This is a critical trait, especially in the Pacific Northwest where summer precipitation is often limited. Other soils, derived from wind-blown deposits, have a high content of weathered minerals and are high in nutrient reserves. Rock fragment content, rooting depth and the amount of clay all have some influence on the productivity potential of soil.

Woodland owners today are concerned about natural resource conservation. You probably want to protect your land as you manage the trees. Each NRCS soil survey contains a forest management section that describes some of the common management problems found in each survey area. You will also find a forest management table that gives each soil a rating of "slight, moderate or severe" for a number of factors to consider in forest management. Ratings of moderate and severe are addressed in a map unit description that briefly discusses the problem and how it may be overcome. The ratings do not mean that the described problem will restrict the soil for forestry use, but that as the severity of the ratings increase, costs to protect and manage the soil resource increase.

Some of the more common forest management factors for which ratings have been made are listed below.

Cut-fill slope erosion relates to the likelihood that resource damage may occur as a result of cuts and fills made during road or landing construction. A moderate or severe rating indicates the need for some form of erosion control such as seeding, mulching or sediment traps.

Equipment operability ratings reflect possible limits on the use of wheeled or tracked ground-based equipment as a result of soil or topographic characteristics. A moderate or severe rating indicates the need to consider choosing between wheeled, tracked or cable harvesting equipment, or the need to time operations to avoid seasonal limitations.

Compaction ratings refer to the probability that damage will occur to the soil structure as a result of repeated equipment use during wet or moist conditions. While the use of designated skid trails and protection of the duff layer are always advised, a moderate or severe compaction rating indicates the need to carefully choose the right equipment and the proper season of operation.

Soil displacement refers to soil being gouged, scraped or pushed from its natural position by mechanical means. It relates to the need to closely monitor soil-disturbing activities such as mechanical slash disposal and site preparation, or to seek alternative methods.

Seedling mortality ratings provide an indication of the hazards faced by tree seedlings resulting from unfavorable soil or topographic conditions. Soil features such as water-holding capacity and slope aspect contribute to the survival of tree seedlings and are considered in making these ratings. To offset this hazard it may be necessary to use larger than normal planting stock, special site preparation, surface drainage or follow-up planting.

Windthrow ratings of moderate or severe warn forest managers of the possible need to carefully choose a harvesting system. Seed tree systems or regeneration with isolated single trees or groups of trees may not be practical for areas with moderate or severe windthrow hazard ratings. Areas with severe windthrow ratings may require periodic salvage of windblown trees and justify the need to maintain an adequate road and trail system to allow for salvage operations.

Plant competition ratings indicate the need for careful and thorough site preparation and the potential need for mechanical or chemical treatment to retard growth of competing vegetation. Moderate and severe ratings alert the forest manager of the need to establish the new forest for tree crop production without undue delay.

Damage to soil by fire rates the risk that a moderately hot fire will have a negative impact on the soil resource. Fire can reduce soil organic matter and increase water repellency. High soil temperatures produced during fire reduce populations of some beneficial soil organisms. To offset this hazard it may be necessary to consider winter burning, alternate lighting techniques, monitoring of fuel moisture content, yarding of unmerchantable material, elimination of prescribed burning or erosion control measures following burning.

To determine if a soil survey is available for your area call your local office of the Natural Resources Conservation Service (formerly Soil Conservation Service). The address can be found in the Blue Pages of your phone book under U.S. Department of Agriculture. Or check the NRCS web site www.or.nrcs.usda.gov. Soil surveys are free and your local district conservationist will welcome the opportunity to discuss the management of your soils and other forest resources with you.

Russ Hatz, a former state staff forester for the Natural Resources Conservation Service in Portland, Ore., is now a cultural resources specialist for the agency. He can be reached via email at russ.hatz@or.usda.gov.

A profile of the Jory soil, one of the most productive in Oregon, and recently nominted to be the Oregon State Soil. (Photo courtesy of NRCS)

This article appeared in the Northwest Woodlands Magazine, Summer 2001- Published quarterly by the World Forestry Center as a benefit of membership in the Oregon Small Woodlands Association, Washington Farm Forestry Association, Idaho Forest Owners Association and Montana Forest Owners Association.