Forest land management interpretations, guidelines, and prescriptions are currently divided into three levels (Boyer 1970; Mitchell 1984). Basic interpretations are those developed using vegetation, environmental, and soil properties to ascertain the inherent nature of the treatment unit, particularly about the risk or ''hazard'' associated with potentially degrading processes. Secondary interpretations incorporate site or ecosystem properties and a number of basic interpretations to describe the sensitivity of sites to specific types of operations. Finally, management interpretations are developed using the above levels of interpretations, along with overall regional resource management objectives and economic constraints.
The basic and secondary interpretations incorporate information from biogeoclimatic and site classification and mapping, terrain and soil mapping, and environmental monitoring. Through their use in the planning phases of forest resource development, particularly in conjunction with the Pre-Harvest Silvicultural Prescription (PHSP), proper management interpretations can help raise the overall level of forest land management.
The recently proposed Interim Timber Harvesting Guidelines (May 1989) for the interior forest regions adopt the preceding approach. With information collected during the pre-harvest survey, basic interpretations of the sensitivity of the site to potentially degrading processes are made. The processes that are incorporated in this procedure are soil compaction, soil displacement, surface soil erosion, and mass wasting. The hazard keys for the interpretation are presented in the fieldguide insert Developing Timber Harvesting Prescriptions to Minimize Site Degradation: Interior Sites (Lewis et al. 1990). Once the individual hazards are assessed, an overall site sensitivity to soil degradation is derived. It is this overall degradation sensitivity that determines, within the current guidelines, the maximum allowable percentage of potentially degrading ground disturbance that can result from timber harvesting operations.
The purpose of this report is to provide background information on the development of the surface soil erosion and soil compaction hazard keys used in Lewis et al. (1989). These keys have evolved from models previously used in British Columbia. The models have been modified to reflect recent research and improved data presentation. Background information on the development of the other hazard keys, soil displacement and mass wasting, is available in Land Management Report No. 62 (Lewis et al. 1991).
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Updated November 27, 2008