Conceptual Model for Predicting Forest Productivity Losses from Soil Compaction

A simple, conceptual model for predicting forest productivity losses from soil compaction is presented. Information regarding each component of the model is summarized. Once compacted, most forest soils in the Pacific Northwest are expected to remain compacted and forest growth affected for several decades. Elements within the model which managers are able to manipulate to influence the amount of soil. compaction caused by tractive machines are identified. Reductions in forest productivity following harvesting with tractive machines have been reported for several sites and species in the Pacific Northwest (Froehlich 1979; Wert and Thomas 1981). Estimates of stand growth loss range from 5 to 13 percent. Reports that reduced stand growth persists for at least three decades and that soils remain compacted even longer (Froehlich et al. 1983) have -motivated forest managers to protect the soil resource from soil compaction. Information is not always available for identifying the most efficient methods for protecting the soil resource from compaction, although current research continues to evaluate the problem. Research will not confirm the applicability of existing knowledge to all soil and site conditions, or to provide answers for future problems. Therefore, we are presenting a conceptual model of how forest productivity is reduced by harvesting with tractive machines, The purpose of the model is to assist land managers in making decisions regarding soil compaction. Forest managers should be able to use the model and associated information to determine how they can best minimize the loss of forest productivity from soil compaction on their lands. l-/Address: Forestry Intensified Research, 1301 Maple Grove Drive, Medford, OR 97501. . and H. A. Froehlich and Professor of Forest Engr., Oregon State University, Corvallis