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Stocking requirements

General objective

  • To provide measurable standards to ensure that the desired stand conditions are met.

The silviculture prescription must specify the stocking requirements, including all applicable elements listed below, for each standards unit. Unless otherwise stated in a higher level plan, an ecologically suitable mix of species must be selected if a mix of species was present on the pre-harvest stand. The regional Establishment to Free Growing Guidebooks provide guidance on species selection and stocking standards.

Stocking requirements for clearcutting, patch cutting, group selection, group shelterwood, group seed tree, retention, and clearcutting with group reserves

These systems create openings in which regeneration must be established and a free growing stand produced. Stocking requirements that must be included in the silviculture prescription are discussed below.

Preferred and acceptable species

Preferred and acceptable tree species for the area must be specified. Preferred species are ecologically suited to the site, and management activities are aimed primarily at establishing these species. Acceptable species are also ecologically suited to the site, but management activities are aimed secondarily towards establishing them.

Minimum allowable horizontal distance

Specify the minimum allowable horizontal distance between trees (minimum inter-tree distance or MITD) of preferred and acceptable species for those trees to be considered well-spaced.

Target stocking standard (TSS)

Specify the number of healthy, well-spaced trees of preferred and acceptable species per hectare desired on the area.

Healthy trees are those considered to be in an acceptable condition in relation to applicable damage standards and growth characteristics. These standards and characteristics are found in the regional Establishment to Free Growing Guidebooks. In some cases, additional criteria are found in regional standard operating procedures.

Minimum stocking standard of preferred and acceptable species (MSSpa)

Specify the minimum number of healthy, well-spaced trees per hectare of preferred and acceptable species that must be on the area in order to consider it satisfactorily stocked.

Minimum stocking standard of preferred species (MSSp)

Specify the minimum number of healthy, well-spaced trees per hectare of preferred species that must be on the area in order to consider it satisfactorily stocked.

Regeneration date

Specify the maximum number of years allowed, from the commencement of harvesting (or from the approval of the prescription if it is for damaged or destroyed timber or trespass), to establish at least the minimum stocking. This is commonly referred to as the "regeneration delay."

Note that for backlog silviculture prescriptions, this period is measured from the commencement of treatments rather than from the approval date of the prescription. Whenever this assessment date is to be measured from a time other than the commencement of harvesting, the prescription should clearly state when the time frame commences.

Free growing assessment period

Note that for backlog silviculture prescriptions, these periods are measured from the commencement of treatments rather than from the approval date of the prescription. Whenever these assessment dates are to be measured from a time other than the commencement of harvesting, the prescription should clearly state when the time frames commence.

Maximum density

Include the maximum number of coniferous trees allowed per hectare in a free growing stand. Use the number specified in the Silviculture Prescription Regulation or as specified by the regional manager. This figure includes only "countable" stems unless otherwise specified by the regional manager. Countable stems are those equal to or greater than a specified minimum height, which is 20% of the median height of preferred and acceptable well-spaced trees in a survey plot, or as determined by the chief forester. For single tree selection, a countable stem is at least 1.3 m in height and less than 7.5 cm in diameter, measured at a height of 1.3 m (the sapling layer).

Post-spacing density range

Specify the maximum and minimum number of healthy, coniferous trees per hectare to be retained after spacing to meet maximum density requirements.

Minimum height

Specify the minimum height, by species, that crop trees must attain in order to be classified as free growing.

Crop tree to brush ratio

Specify the height that a free growing crop tree must attain relative to competing vegetation within a 1 m radius of the tree's trunk.

Minimum pruning height

A minimum pruning height must be stated if:

The minimum pruning height must specify the height to be pruned, measured from the ground up, prior to the free growing assessment period. This height must also allow for at least 30% of the live crown to be retained.

Other survey criteria

Any additional, specific acceptability criteria or standards should be described under this section.

Where advanced regeneration or trees that vary from free growing survey criteria (as presented in the Establishment to Free Growing Guidebook) are expected to contribute toward stocking at the free growing assessment, the criteria for acceptability should be stated with the stocking standards.

Stocking requirements for other even-aged partial cutting systems

For uniform seed tree, uniform shelterwood, retention with dispersed leave trees, or other even-aged partial cutting silvicultural systems not covered by the section above, the silviculture prescription must include:

Stocking requirements for single tree selection

When prescribing single tree selection systems, stocking standards are required by layer, as defined in the Operational Planning Regulation. The four requisite layers are described as follows:

  1. "mature layer" means the layer of trees with a stem diameter of 12.5 cm or greater, measured at a height of 1.3 m
  2. "pole layer" means a layer of trees with a stem diameter greater than or equal to 7.5 cm, but less than 12.5 cm, measured at a height of 1.3 m
  3. "sapling layer" means the layer of trees with a stem diameter less than 7.5 cm, measured at a height of 1.3 m
  4. "regeneration layer" means the layer of trees shorter than 1.3 m

Note that it is possible for one or more layers to be absent, in either the existing or future stand.

The stocking requirements for single tree selection are as follows:

Stocking requirements for intermediate cuts

This section applies to commercial thinning, harvesting of poles, sanitation treatments, and other intermediate cuttings that do not have regeneration objectives. For these types of harvesting, the following information must be provided:

Stocking requirements for retention systems

Retention can be either group retention, dispersed single tree retention, or a mixture of both. A group retention system has the stocking requirements as described in the Operational Planning Regulation section 39(1)(a), similar to the stocking requirements for clearcutting, patch cutting, and group selection. A dispersed retention system has the stocking requirements described in 39(1)(c), similar to those for seed tree.

Stocking requirements for shelterwood systems

A shelterwood silvicultural system requires stocking standards for the regeneration layer and the shelter trees. The shelter trees will typically be mature trees or may include some from the pole layer, depending on the structure of the original stand. A modified table for single tree selection stocking standards can be used to determine these stocking requirements.

Stocking requirements for advanced regeneration

Where advanced regeneration will contribute to stocking, the single tree selection table (Table H.3) may be more convenient to use than Table H.2 (stocking requirements for silvicultural systems other than single tree selection). For example, there may be 50 pole-sized trees and 100 saplings being retained per hectare. Alternatively, advanced regeneration may be described in the description of leave trees species and function.

Stocking requirements for riparian management areas

The management zone of a riparian management area may have different stocking requirements than the rest of a cutblock. In this case, the management zone will be a separate standards unit. The stocking information required will depend on the silvicultural system used, as described above.

Stocking standards for complex site units

Complex sites are those that contain distinctly different site series, but are unmappable as a single stratum (refer to the section on stratification for more details). Stocking requirements can be stated separately for each component of the complex, if appropriate. For example, it may be appropriate to have separate standards when the complex occurs on hummocky terrain with dry ridges and wet draws, provided that the boundaries of each can be identified on the ground.

Figure 28. Example of stocking standards for clearcuts or patch cuts.

Figure 29. Example of stocking requirements for single tree selection silvicultural systems.

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