Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092143

    St. Mary’s Residual Basal Area Study in a Mixed Conifer Stand
 
Project lead: Waterhouse, Michaela (Ministry of Forests and Range)
Contributing Authors: Waterhouse, Michaela J.; Newsome, Teresa A.; Arsenault, Andre; Armleder, Harold M.; Comeau, Phillip G.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Description:
The Saint Mary’s project is a single tree selection silvicultural systems trial located near Cranbrook, B.C. in the IDFdm biogeoclimatic subzone. The stand is a mixture of Douglas-fir, lodgepole pine, ponderosa pine and larch with a variety of age classes due to fire and selective logging history. The purpose of the trial is to develop uneven-aged stand structure (J-shaped curves) and continuous establishment and growth of natural regeneration to produce a range of timber products. To achieve this goal, three residual basal area prescriptions with species selection criteria were harvested in 1994. The resulting treatments included: 8 m2, 16 m2 and 24 m˛ residual basal area, and a no-harvest treatment (basal area =38m˛).

The trial was set up as a completely randomized design. The four basal area treatments were randomly assigned to 4 – 1 ha treatment units for a total of 16 units. Preferred leave trees (Douglas-fir then larch) were marked before harvesting then pine, followed by other species, were preferentially removed. Sixteen plots were established within each treatment unit to follow ingress and growth of advanced tree regeneration, and the growth response of the overstory residuals. An assessment was completed post-harvest in 1995 but was not re-measured due to lack of staffing. In 2006, the research team from the Southern Interior Region determined the integrity of the trial was still intact and that with some trial maintenance, 14 year (regeneration) and 15 year (growth and yield data) could be obtained.

This data is especially in demand given the recent mountain pine beetle (MPB) outbreak. Due to the preferential removal of pine (and a smaller component of other species) the resultant stand structures are similar to stands left after salvage logging of mountain pine beetle infested stands in the Southern Rocky Mountain trench. Burton (2006) identified the response of complex stands to selective removal or gradual loss of pine trees as a knowledge gap in a recent discussion paper on MPB attacked stands. This trial will provide valuable insight into how stands develop and provide estimates on timber growth in these treatments. It will provide a site where the growing environment within these partially harvested stands can be quantified and survey methodology can be tested. Data on the post logging stand structure compared to the present stand conditions will assist in making decisions regarding partially harvested stands and will provide data for modelling programs such as TASS and PrognosisBC.

It is important to ensure these sites after partial harvesting are fully occupied and contributing to future timber supplies. However, it is often difficult to determine the level of site utilization in selectively logged mixed species stands. The study will also explore measures of site utilization such as Reinecke’s Stand Density Index (SDI) and Leaf Area Index (LAI). These estimates of stand occupancy can be used to make operational decisions for management of single tree selection harvesting silvicultural systems. The SDI is closely related to the -3/2 power law (Long 1985) and to light capture (Vales and Bunnell 1988). It can be applied in mixed-species and multi-storied stands Long (1996). Waring (1983) found LAI is strongly related to stand volume increment. O’Hara and Gersonde (2004) demonstrate the use of LAI as a measure of growing stock and space utilization in pure and mixed conifer stands. A knowledge of LAI and its distribution among stand components (i.e. species and size classes), the influence of stocking and light environments on growth efficiency, and the relationships between SDI (or other density measurements), LAI, and productivity are potentially useful in understanding factors which influence understory development under different levels of overstory retention.

The trial site is located on ungulate (elk, mule deer) winter range. The types of prescriptions tested could be used to create desired conditions for management of winter habitat (Ungulate Winter Range Technical Advisory Committee 2005). Single-tree prescriptions in dry Douglas-fir forest types are used extensively in the Cariboo-Chilcotin region for management of mule deer winter habitat to provide continuous cover (snow interception, visual, thermal) and forage (Douglas-fir foliage from large trees, arboreal lichens and shrubs) (Dawson et al. 2006). This trial provides the opportunity to measure the snow interception capacity and understory shrub production, which could aid development of appropriate silvicultural systems for winter range located in low-elevation Douglas-fir forests in the Rocky Mountain Trench.

During a field trip in spring 2006 operational staff expressed a strong interest in the trial and indicated the need for growth and yield data, regeneration data collected by layers, vegetation response under partially harvested stands (useful for forest interface issues as well as regeneration), forest health issues such as Armillaria, mistletoe, and pine beetle. They also felt the trial could be used to assist in verification of survey methods used in partially harvested stands for stocking and free-growing. These issues will all be addressed during the various scheduled assessments.

The work schedule includes trial and plot re-construction in 2007; regeneration, vegetation and understory light assessment in 2008, and 15 year growth and yield data collection in 2009. Standard growth and yield protocol will be used. Strategies for assessing the stand will be discussed on site with MOFR growth and yield experts.

Results from this trial can be compared to other retention trials across the southern interior region located in the Cariboo (EP1104.01) and West Kootenay’s (EP1186). Both of these trials are submitted for continued funding under the FIA – FSP program. Regeneration performance and residual stand growth is also being monitored on these sites.
Related projects:  FSP_Y081143FSP_Y103143

    Deliverables:
Executive summary (0.1Mb)

Updated August 16, 2010 

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