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This project links two long-term, shelterwood silvicultural systems trials in the Southern Interior Forest Region of BC. Although the trials were initiated for different reasons, visual constraints and root disease in the ICH in the former Nelson Region, and species conversion in the SBS in the former Cariboo Region, they have similar goals and treatments. Both trials examine uniform shelterwood silvicultural systems (level of basal area retention 25 to 65%), harvesting methods, and regeneration development which will contribute to refinement of stocking standards and free growing guidelines. Data from the trials can address wildlife and biodiversity issues. Uniform shelterwoods also have the potential to meet other land use planning objectives regarding visual quality, partial cutting in riparian management zones, and recreation. The SBS trial, initiated in 1990, was designed to attain natural Douglas-fir regeneration through the use of uniform shelterwood silvicultural systems. Prior to that time, prime Douglas-fir growing sites were being converted to lodgepole pine, due to poor condition and survival of Douglas-fir caused by frost in clearcuts (Steen et al. 1990). Studies in Douglas-fir forests in the U.S.A. (Tesch and Mann 1991; Joy and Hutton 1990; Shearer and Schmidt 1990; Dunlap and Helms 1983) pointed out that partial canopies enhance regeneration success by reducing frost and moisture stress. The trial blocks were initially cut in 1990 to two residual basal areas then cut again in 2001 to create four residual basal area treatments and a no-harvest treatment. Regeneration response to levels of cutting is documented in Burton et al. (2000) and Waterhouse and Newsome (2006). The ICH shelterwood trial was initiated in 1993 (Delong et al. 2005) because a significant percentage of the land base was being harvested with partial retention systems to meet guidelines for visual, ungulate habitat and other values (Vyse and DeLong 1994; Hawe 1996; Coates et al. 1997; Listar et al. 1998). There continues to be serious management questions about the productivity (tree growth and yield), 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. These diseases affect both forest harvesting and regenerating management practices (Morrison et al. 1991). Partial harvesting is thought to accelerate the spread by leaving dead stumps, which provides a food source for the fungus (Cruikshank et al. 1997; Morrison et al. 1988: Morrison et al. 1991). The study was set up with two levels of retention and no retention, and two types of harvesting: conventional and whole tree push-over logging. Pushover logging was selected to reduce the fungi level in the soil (Morrison et al. 1991; Hood 1989). Data on the response of residual trees, regeneration and vegetation development is being collected and the fifth year regeneration results are published (Delong et al. 2005). Additionally data is being collected to document effects of residual basal area on light levels and light capture as estimated by the Leaf Area Index (LAI). LAI is another potentially useful measure of growing space occupancy and is strongly related to stand volume increment (Waring 1983). There is also opportunity to use these shelterwood silvicultural systems trials to evaluate management options for stands affected by Mountain Pine Beetle. In a recent review, Burton (2006) points out that it is not known how complex stands will respond to selective removal of pine trees. Pine (lodgepole, white, ponderosa) is a common component of mixed stands in many biogeoclimatic subzones throughout the Southern Interior. The death and / or removal (through salvage) of pine will affect stand development and consequently long-term timber supply. Results from these trials (in place now 10 ? 15 years) will provide guidance as to level of harvest, and predict regeneration and resid ...
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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