The diameter of the knotty core should not increase from the first to the second lift, when pruning is done in multiple lifts. This ensures that the size of the knotty core is maintained through the second lift on the stem (Figure 2). Figure 3 shows the impact on clear wood timber production from late and on time pruning regimes.
The cost of pruning has currently restricted treatments funded by the B.C. Forest Service to a maximum of two lifts. To ensure a marketable product can be obtained at the end of two lifts, tree height has been used as the primary factor to determine when the second lift should occur.
Pruning should not be done in the spring when the bark is loose and the potential for stem damage is high.
When scheduling second lift pruning consider:
Figure 2. Time the second lift of pruning to maintain the same size of knotty core as the first lift. The second lift should occur no later than when the diameter immediately below the first whorl of branches at the start of the second lift equals the diameter at the start of the first lift.
Figure 3. Distribution of clear wood from late and on time pruning regimes.
Where required through consultation with the appropriate Ministry of Environment, Lands and Parks staff, a visual buffer should exist along main and secondary roads in areas with high populations, or hunting pressure, of big game species. A visual buffer, also known as a visual screen, may be provided by topography or vegetation (Figure 4) which blocks the viewing of the interior of the treatment area. In the absence of naturally occurring visual buffers, unspaced buffers should be left at the spacing stage. If such unspaced buffers have not been left, then spaced areas can be left as unpruned buffers. The buffer size depends on the specific site conditions. The width of the buffer should be sufficient that a person or animal walking along the interior edge of the buffer is at least 90% screened from view from the road.
The access management plan for the area should be considered when determining the need for visual buffers along roads. Visual buffers may not be needed if roads are deactivated after the pruning treatment.
A degree of visual buffering may also be achieved by leaving some unpruned trees throughout the stand. Such trees would include poor quality stems (wolf trees), unsuitable tree species (hardwoods), or residuals. Leaving small patches of unpruned trees may also be required to create a visual buffer within the stand or around important wildlife areas such as wildlife trees and riparian zones.
Restricted harvesting practices in riparian management zones will reduce the economic feasibility of pruning in these areas.
Figure 4. Vegetation or topography can create a visual buffer (from Nyberg and Janz 1990).
A visual buffer of unpruned trees along roadways may be necessary to reduce wildlife visibility from the road.
Pruning should be restricted in areas where lichen is identified as important wildlife forage.
Wildlife tree management includes both the retention of suitable wildlife trees at the time of harvest and silvicultural activities, and the recruitment of suitable replacement wildlife trees over the rotation period.
Generally, the safest and most operationally feasible method for managing wildlife trees is to leave a mixture of live and dead standing trees in a clumped distribution (reserves). The location and size of the reserves in a stand will depend on specific site conditions such as availability of high quality wildlife trees, and wind firmness. The amount of wildlife tree area required for any specific unit depends on the level and distribution of existing and planned harvesting on the surrounding landscape. Wildlife tree reserves may be located at the edge of the stand, in areas that are difficult to access or in less productive areas. This location can be done to minimize the impact of the mandatory no-work zone. Refer to the Biodiversity Guidebook for more information on wildlife trees.
Maintain wildlife trees in wildlife tree reserves.
The location of these reserves should be consistent with the Biodiversity Guidebook.
In addition to their location, the size of the trees (diameter breast height and pruning height) at the time of pruning must be known. At rotation age, the amount of clear wood available in each log cannot be visually assessed until the log is processed. The value at rotation cannot be forecast without initially documenting the size of the knotty core.
Pruned areas must be clearly marked on forest cover maps.
The dbh of trees at pruning and the pruning height should be documented.
The number of branches in a whorl must also be considered; the most desirable tree has few. Trees with many branches per whorl should be left if pruning may girdle the tree. Pruning costs may also become excessive with many branches to prune.
Do not prune a tree if it will result in girdling of the stem.
If a species making up a minor component of the stand has adventitious buds these may be left unpruned.
Prune all stems in a stand if a change of dominance may occur between pruned and unpruned trees.
Proper lift height must be defined for each stand considering the length of clear wood desired and the height of the trees. If a single lift is planned, the minimum length of clearwood should normally be 3 metres.
Use pruning shears or saws. Do not use an axe or machete to prune branches as these tools can damage trees. These tools may fracture the base of the branch inside the stem, leading to decay and reducing clear wood quality. Do not use chain saws unless they have been modified to successfully protect the stem from scarring. Shears cut close to the branch collar of the tree without the risk of scarring and form a clean cut surface. Cut surfaces that are jagged or have torn fibres take longer to occlude.
Do not use tools such as axes and machetes that remove branches using an impact force.
Long-handled or telescopic pole pruning saws, or lightweight ladders with pruning shears or saws can be used for the second or subsequent lifts.
Figure 5. Proper pruning of a branch is a cut as close as possible to the branch collar staying roughly parallel to the stem.
Properly pruned trees must have:
The minimum acceptable performance quality is 75% as measured by the Ministry of Forests procedure.
The submission dates are April 15, July 31, October 31, and January 15. Pruning done by the Small Business Forest Enterprise Program should be reported following ministry procedures.