This project continues to fit with the strategic goals of the FSP program in providing relevant and timely information and extension products to support both sustainable forest management and timber growth and value. The best fit for this project is: Program: Timber Growth and Value Program Theme: 2.0 Design and analysis of silvicultural systems Topic: 2.1 Complex stands This project links two long-term, shelterwood silvicultural systems trials in BC. Both projects focus on the relationship between residual stand structure and understory development. They also have objectives related to non-timber issues. Although the trials were initiated for different reasons, visual constraints and root disease in the ICH, and species conversion in the SBS, there are similar goals and treatments in the trials. Both trials examine shelterwood harvesting systems (basal area retention, type of removal) in Douglas-fir leading (but mixed) forest types. Their regeneration success will influence stocking and free growing policy standards. Data from the trials can address wildlife and biodiversity issues. The SBS trial, initiated in 1990, was designed to attain natural Douglas-fir regeneration through the use of uniform shelterwood silvicultural systems. Douglas-fir stock was performing poorly in clearcuts due to frost damage. The ICH trial was initiated in 1993 because a significant percentage of the landbase was being harvested with partial retention systems to meet guidelines for visual, ungulate habitat and other values. Results from this trial can also be used to address issues surrounding stocking levels after salvage harvest of trees attacked by pine bark beetle. There are serious management questions about the productivity, regeneration, and future health of these forests, especially as a large portion of the area is infected with root disease such as Armillaria ostoyae and Inonotus tomentosus. Common objectives for the two trials are: ? Evaluate the impact of various levels of basal area retention, and harvesting systems (equipment, season, removal intervals) on the survival and growth of natural and planted regeneration, ? Investigate the effects of microenvironment (light, frost), understory vegetation, and soil properties on the survival and growth of natural and planted regeneration, ? Evaluate the growth and yield implications based on residuals and new regeneration, ? Provide resource managers with research results and potential options for stand management. Trial specific objectives are: ? In the SBSdw trial, to measure snow and forage response levels of residual basal area then develop silvicultural systems appropriate for mule deer winter range. ? In the ICH trial, to compare the success of conventional harvesting with pushover harvesting in ameliorating the effects of Tomentosus and Armillaria root diseases, on seedling survival and growth.