Title: Detrimental soil disturbance associated with timber harvest systems on national forests in the Northern Region
Description: Maintaining site productivity on forested lands within the National Forest System is a Federal mandate. To meet this mandate, soil conditions on timber harvest units within the Northern Region of the USDA Forest Service cannot exceed a threshold of 15% areal extent of detrimental soil disturbance (DSD; defined as a combination of compaction, puddling, rutting, burning, erosion, and displacement). The objectives of this study were to collate post-harvest soil monitoring data and to statistically document the areal extent of DSD resulting from timber harvest systems in the Northern Region. Current and legacy post-harvest soil monitoring data on National Forests throughout the Northern Region were collected to determine whether timber harvest systems (ground-based, skyline, or helicopter) used in the Northern Region result in DSD levels in excess of the mandated 15% areal extent. Statistical models developed in this study showed significant differences in the areal extent of DSD following timber harvest operations among ground-based, skyline, and helicopter harvest systems; among harvest seasons; and among National Forests. The frequency of DSD harvest operations followed the general trend of ground-based helicopter. Winter ground-based harvest resulted in a significantly lower areal extent of DSD than summer ground-based harvest. Differences among Forests may have been caused by unique physiographic and ecological characteristics and distinct survey methods. However, despite significant differences in the amount of DSD resulting from similar timber harvest systems, none of the harvest systems that we evaluated on the National Forests consistently resulted in mean disturbance levels in excess of the 15% areal extent threshold.
Subjects: Soil degradation, Logging, Forest soils
Places: United States, Pacific Northwest