INTRODUCTION

1. Geomorphic Response to Forest Practice in the Willamette Basin ES 473 ENVIRONMENTAL GEOLOGY Prepared by: Robert Mock Effects of Meager Logging Techniques and Construction of Roads on the Environment • Use of heavy equipment and high traffic creates soil compaction • Leads to a diminishing rate of re-growth • Kills off root systems • Secretion of ground water and nutrients creating a lower porosity of soils • Contributes to mass wasting • Clearcutting destroys the environments ability to regulate geomorphic processes • Leaching of valuable recourses like Nitrogen, Phosphorous, and Magnesium • Diminishes water absorption • Removes protection from stream banks • Reduces hill side cohesion of soils Relationships of Environmental Impacts In analysis of an area of the H.J. Andrews Experimental Forest on Land below 1000 meters with predominantly altered volcanclastic geology two areas were evaluated for environmental impacts of forest management practices. One area was forested land untouched by man, and the other was 25.6% clear cut with 5% of the land road rights-of-way. The result of the study show that the clear cut land had 30 times the amount of slide erosion than the forested area. INTRODUCTION Willamette Basin forests are suffering from a diminishing energy supply and a loss of ecosystem services. Forest practices are associated with increased soil erosion and landslides. With disturbed soils, watershed productivity has historically experienced declining trends. In order to maintain optimum levels of forest production, balanced by minimized geomorphic effects, alterations in forest practice is a necessity. This paper examines the relationship between timber harvesting methods and erosion processes in upland basins of the Western Cascades. The effects of road construction and clear-cutting are examined. Composition of Pacific Northwest Forests • Primarily composed of evergreen coniferous trees • Adapted to winter-wet and summer-dry environment • Small streams in forest watersheds comprise 86% of all river channels in the U.S. • Forests supply energy, minerals, shade and stability of soils, thus regulating the rate of stream production • Erosion from unstable soils affects the stability of substrates and the leaching of nutrients Erickson Air-Crane removing logs from an Oregon hillside Siskiyou, Oregon Clear-cut project Conclusions The most desirable logging techniques include: • Thinning with minimal road construction • Limit logging to periods when soils are predominantly dry • Use low impact equipment • Create culverts to maintain drainage from streams • Leave buffers around streams • Replant trees and shrubs • Rotation of regions that do get logged These techniques are growing in popularity as concerns for geomorphic processes are growing. Logging practices have changed dramatically throughout Oregon's history and continue to seek improvement. Alternative Logging Practices • Limit logging to dry grounds • Limit the amount of roads created • Use selective cutting/thinning techniques • Leave stream buffers to preserve integrity • Use low impact equipment • Lighter weight/wider wheel base • Alternative equipment • Air-cranes • Replant trees and shrubs • Fertilize • Slash burn when applicable • Rotate between different regions to prevent overexertion History of Oregon’s Logging Industry • Economic boom from WWII increased timber demand and continued through the 1940’s and 1950’s • Clearcutting was dominate practice • Trees were either yarded out or skidded with a Cat • Streams were redirected to increase flow and over powered by log transfers • Logging roads prevailed throughout the terrain • Minimal restrictions on logging References Cited K. Cromack, Jr., F.J. Swanson and C.C. Grier. A Comparison of Harvesting Methods and their Impact on Soils and Environment in the Pacific Northwest. 1979, U.S. Department of Agriculture F.J. Swanson, C.T. Dyrness. Impact of Clear-Cutting and Road Construction on Soil Erosion by Landslides in the Western Cascade Range, Oregon. 1975, The Geology Society of America.