Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092145

    Shelterwood silvicultural systems to address integrated resource management issues
Project lead: Waterhouse, Michaela (Ministry of Forests and Range)
Contributing Authors: Waterhouse, Michaela J.; Newsome, Teresa A.; Arsenault, Andre; Chapman, Bill K.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
As a result of the focused workshop (October 2007) the final harvest for the SBS trial could be moved to January 2009 (2 years earlier than planned). This is still under discussion between the partners, and we have to work with the Central Cariboo Forest District to see if it is logistically possible. The fifth year regeneration and vegetation data was written up as a draft report in March 2007. The intent was to publish this as a MOFR technical report in March 2008. Given the change in logging plans, it is preferable to add the 7 & 8 year data to the draft technical report this year and publish the final pre-harvest data March 2009. We have planned funds for writing a series of file reports in 2009. The extension products essentially switched between years but funds and outcomes of the project are not changed.

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 residual overstory response. Also new surveys for assessing stocking levels in partially harvested stands have been developed (Martin et al. 2005) and the trials present an opportunity to test the survey methods and contrast the results with the measured regeneration response and light assessments.

It is important to retain a range of tree species and timber quality to meet current mill requirements and provide for a diversity of future products. However, conversion of mixed stands to lodgepole pine is common due to its resilience and fast early growth. Shelterwoods can create conditions that facilitate the growth and performance of a number of species. They also promote production of a variety of timber products as a result of the different entry periods. Initial entries remove seral species such as pine and broadleaves before they deteriorate. Leave trees will produce larger more valuable timber. In the long-term, a range of tree species across the landscape can mitigate (economically and biologically) natural disasters such as the current mountain pine beetle epidemic.

The projects support higher level strategic decisions and planning processes. For example, information from the SBS trial can be used to meet species composition goals for biodiversity under the Cariboo-Chilcotin Land-Use Plan (CCLUP) (Province of B.C. 1995) and the Horsefly and Williams Lake Sub-Regional Land Use Plans. Mule deer are identified as a key management species under the Cariboo-Chilcotin Land Use Plan. About one third of Douglas-fir forests in the SBS are mapped as mule deer winter range. In the SBS, snow depth is a key factor to be managed to maintain quality winter range. Information from snow interception and vegetation studies on the SBS trial can be used to refine the silvicultural systems prescriptions described by Dawson et al. (2006).

Both trials have a Ministry of Forests and Range peer-reviewed Working Plans that contain detailed methodologies: SBS #EP 1104.01 (Waterhouse 2001), ICH #EP1186 (Pollack 1997) that include measurements of regeneration, residual overstory, light and vegetation. In the SBSdw project, windfall, snow interception, seedfall and microclimate studies are ongoing. EP1186 also has a detailed root the disease component (Allen 1999). Subsequent peer reviewed publications summarizing the methods and results of many of the studies include Burton et al. (2000) and Waterhouse and Newsome (2006) for the SBS trial, and Delong et al. (2005) for the ICH trial.

Note: Mike Curran and Mario DiLucca are team members (1% time) but out of team member space.
Related projects:  FSP_Y081145FSP_Y103145

Executive summary (0.1Mb)

Updated August 16, 2010 

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