Policy 2.24 - Stand Density Management

Effective Date: 15-Feb-99
Responsible Branch: Forest Practices Branch

Resource Management Volume Table of Contents | Amendment Log

Scope

This policy applies to crown land and applies to development and implementation of stand density management activities that are required by law.

Authority

The Silviculture Practices Regulation (SPR) section 13 (6), provides the Chief Forester with authority to establish, vary, or cancel policies and guidelines respecting stand density management, including matters relating to the maximum density of trees that may be present on an area under a Silviculture Prescription before a spacing treatment must be carried out.

For the purposes of SPR section 13, this document is the Chief Forester's policy for stand density management. For the purposes of SPR section 13, the Guidelines for Developing Stand Density Management Regimes (Guidelines) is the Chief Forester's guideline respecting the development of stand density management regimes. Unless otherwise developed following this policy and the Guidelines, the maximum density of coniferous trees is 10 000 stems per hectare (sph). SPR Section 13 allows a Regional Manager (RM) to establish a maximum density of coniferous trees for different parts of a forest region or district in accordance with this policy and the Guidelines.

Policy

The purpose of this policy is to ensure the careful evaluation, planning, and implementation of stand density management activities to achieve desired stand, landscape, and forest level objectives. This policy is intended to:

• provide direction to practitioners using the Guidelines for Developing Stand Density Management Regimes; and
• provide the basic provincial stewardship principles and assumptions needed to ensure public interests are considered in the development of stand density management regimes and maximum density numbers

Definitions

Density Management Regime - one or more silviculture interventions to achieve specific stand densities and/or conditions at specific time periods and locations to achieve desired stand, landscape, and/or forest management objectives.

Target stocking standard - is the target number of healthy, well-spaced trees of the preferred and acceptable species per hectare. This is the target number of well-spaced trees at the free growing stage that will produce the target future stand condition(s).

Minimum stocking standard - is the minimum number of healthy, well-spaced trees of preferred and acceptable species per hectare. This is the minimum number of well-spaced trees needed at the free growing stage to produce the minimum acceptable future stand condition(s).

Maximum density - the maximum number of coniferous trees allowed per hectare in a free growing stand. This number is specified in countable trees per hectare. Without density control, areas exceeding the specified maximum density number are not expected to produce the acceptable stand conditions within desired time periods. Only those portions (i.e., a forest cover or survey strata) of a standards unit area within a Silviculture Prescription (SP) that exceed this number must be spaced.

Maximum density is not to be equated with a repression density or stand densities that result in reduced site index.

Countable trees - are trees that meet specific height criteria or characteristics, and are tallied in a silviculture survey to determine stand density and maximum density obligations.

How to use the Guidelines for Developing Stand Density Management Regimes

The Guidelines provide information on biological, economic, and forest level considerations for stand density management. It also provides a general planning framework for developing and analyzing stand density management regimes and considerations for implementing spacing operations. The following information is intended to help guide the development of stand density management regimes and implementation of the Guidelines:

Who should be involved? - regional, district, licensee foresters, Ministry of Environment, Lands and Parks (MoELP), and other agencies or groups deemed appropriate by the RM. The RM may require density management regimes to be reviewed with other agencies or groups.

Who does the analysis? - may be done by region, district, or licensee staff, but must be consistent with this policy. The analysis must be done in consultation with district and regional staff.

How to do the analysis - The most desirable approach for the development of new density management regimes is to carry out full stand and forest level evaluation and analysis of different stand density management regimes. Where possible, the development of stand density management regimes should be integrated with other analyses currently underway (e.g., analyses for Innovative Forest Practices Agreements, Enhanced Forest Management Pilot Projects, Timber Supply Review 2, Forest Level Incremental Silviculture analyses, etc.).

In some cases staff time and funding may be limited and preclude a full scale analysis. Regions, districts, and licensees may develop new numbers (best estimates of density management regimes that are appropriate for different areas and conditions) by setting up a series of meetings with appropriate subject matter experts and operational staff.

The RM is the statutory decision maker responsible for the specification of any new maximum density numbers and should therefore approve which approach is taken and the assumptions to be used in the development of new numbers.

When to start - new stand density management regimes for use in Resource Management Plans and Stand Management Prescriptions, can be developed using the Guidelines and this policy beginning April 1, 1999. The RM should approve the commencement of any initiatives aimed at developing new maximum density numbers.

What should be produced - a series of density management regimes and maximum density numbers that are applied on a regional, district, geographic, or licensee-specific area. Maximum density numbers should preferably be based on a management unit basis (i.e., TSA/TFL). However, they may be developed on a management zone, ecosystem, or diversified portfolio basis.

Minimum Provincial Stewardship Requirements

The following forest management issues should be incorporated in the development of stand density management regimes:

forest production objectives - high value forest products is the objective unless otherwise specifically identified in existing Woodlot management plans, TFL management plans, or TSA objectives

consideration of existing stocking standards - new stand density regimes should be developed with consideration of the forest or product objectives that are embodied in existing minimum and target stocking standards

existing higher level plans - stand density regimes that are identified in higher level plans (i.e., Land and Resource Management Plans or Landscape Unit Plans) must be considered in any analysis

options and risks - stand density regimes should be developed that maintain options and minimize risks for future generations. Stand density regimes should ensure options are maintained for future harvest ages, species mixes, and forest values.

target stocking standard - unless the District Manager (DM) approves otherwise, the target stocking standard should be set at the density of trees at the free growing time period that will achieve the target stand conditions at the specified harvest age

minimum stocking standard - unless the DM approves otherwise, minimum stocking standards should be set at a density of trees that considers the entire silviculture regime, including any intermediate interventions, and does not result in significant merchantable volume reductions compared to a stand at the target stocking standard

maximum density or upper density limit - should be developed with consideration of the desired target and minimum stocking standards and consistent with analyses done using this policy and the Guidelines

How to deal with density management practices on special areas

There may be areas within a management unit that require analysis, evaluation, and selection of stand density management regimes that is different than the stand and forest level process outlined in the Guidelines.

Wildlife habitat - consider appropriate wildlife habitat guidance (e.g., guidelines for managing Goshawk, Woodpecker, Mule deer, Caribou, Elk, Grizzly Bear) to develop density management regimes. Any areas that are identified as wildlife habitat areas or Special Management Zones may need to be separately evaluated to select a stand density management regime that adequately maintains or produces desired wildlife habitat conditions.

Forage production areas - District Range and MoELP staff should determine any specific density management objectives relating to forage production for livestock and wildlife. Where there are specific goals for livestock Animal Unit Months (AUM) levels and natural wild ungulate levels, density management regimes should be designed to maintain those levels.

Understorey biodiversity values - for identified wildlife habitat areas, or areas with general wildlife measures, density management regimes may be designed to produce or maintain the desired biodiversity or habitat conditions

Special ecosystems (e.g., Cedar - Hemlock Salal) - there may be specific ecosystems that cannot be adequately evaluated or modelled due to limitations in existing growth and yield information. In these cases, density management regimes should be developed using best available information and discussion with subject matter experts.

Partial cutting - for partial cutting in mixed species and all-aged stands, density management regimes should be developed using best available information and discussion with subject matter experts

Forest Health - there may be specific forest health conditions that cannot be adequately evaluated using existing growth and yield decision aids. In these cases, density management regimes and practices should be developed using best available information and discussion with subject matter experts.

Landscape level forest succession - there may be opportunities to use stand density management to achieve old-growth stand structure objectives. Where there are succession imbalances or limitations in the management unit, density management regimes may be developed that contribute to landscape level objectives.

Minimum Forest and Stand Modelling Assumptions and Requirements

The following are minimum forest and stand modelling assumptions and requirements that should be included in the development of stand density management regimes:

• utilization standards - unless otherwise approved by the RM, use assumptions consistent with the current or last approved Timber Supply Review (TSR)
• ensure that the key Forest Practice Code requirements (i.e., green-up, riparian management zone requirements, landscape unit objectives) are considered
• use appropriate stand and forest level models
• ensure key assumptions included in the analysis consider the current or recently approved TSR
• where there is a need to make significant variances from the current or last approved TSR, new assumptions need to be reviewed with and approved by the RM
• consider the need for any intermediate interventions (i.e., commercial thinning) in the design of stand density management regimes
• yield curves used to represent an analysis unit in a forest level analysis (unique combination of species, site class, and density management regime) must be realistic and adequately represent site conditions and the intended management objectives and practices and basic silviculture obligation levels
• The evaluation and determination of a stand density regime will result in the identification of stand densities that are desired at various time periods during the development of a stand. Consideration must be given to the types of operable stand conditions (such as piece size distribution, merchantable volume) that are needed to ensure a stand can be economically harvested. The evaluation should result in the identification of appropriate density management standards that ensure stand, landscape, and/or forest objectives can be achieved.

Using the New Stand Density Management Regimes

Once new stand density regimes have been developed, they should be the basis for the maximum density numbers that are included in new SPs.

Key points in the specification of a maximum density number:

1. The default maximum density number to be included in Silviculture Prescriptions is 10,000 sph unless new numbers have been developed following the Silviculture Practices Regulation Section 13, the Guidelines, and this policy.
2. Any new maximum density numbers should be developed with consideration of stand, landscape, and forest issues and objectives. They should be aimed at improving or maintaining an economically viable timber supply.
3. Specific stand densities may be required to achieve wildlife objectives identified in a higher level plan, a TFL management plan, or the Managing Identified Wildlife: Procedures and Measures Guidebook. In select areas, maximum density numbers may be specified for Ungulate Winter Range, Special Management Zones, and/or Wildlife Habitat Areas.
4. When specifying any maximum density numbers that are to be applied to SP's approved on or before December 30, 1997, the RM should consider the potential financial implications. The RM should not normally specify a retrospective number that would result in a more onerous financial obligation than the maximum density numbers contained in SPs approved on or before December 30, 1997.
5. The RM may specify a maximum density number other than 10 000 if satisfied that a number other than 10 000 is necessary to ensure that the forest resources are adequately managed and conserved in an area. In determining adequate management and conservation of the forest resources, the RM should consider points 1-4.

Height criteria for Countable Trees

Free growing surveys tally the number of trees contributing towards the maximum density limit.

For clearcut, shelterwood, seed tree, and group selection silvicultural systems, the Silviculture Practices Regulation specifies that the minimum countable height standard is 20% of the median height of the crop trees.

For areas prescribed for single tree selection, the minimum countable trees are greater than or equal to 1.3 metres in height and have less than 7.5 cm dbh.

The RM may request that Chief Forester consider establishing different characteristics of trees to be counted for the purpose of determining if the maximum stand density has been exceeded. The RM may request the Chief Forester to consider specifying different standards for different silvicultural systems, species combinations, stand types, stand structures, or ingrowth patterns. In submitting a request, the RM should provide accompanying information illustrating the impact of any changes on licensee obligations, total stand density, and the achievement of desired stand, landscape and/or forest level objectives.

Note: Changing countable heights can have a similar affect to maximum density obligations as changes to the maximum density number. Different countable height standards should be carefully evaluated in conjunction with any proposed changes to maximum density numbers.

Note: Growth and yield (GY) decision aids normally use estimates of total trees/ha and not countable trees/ha. When using growth and yield models to evaluate different stand densities, consider the difference between running a GY simulation that includes a tally of all trees versus a tally that includes only the countable stems per hectare.

Implementing Stand Density Management Activities

Stand density management activities should only be done after careful consideration of the biological, economic, and forest level implications of the treatments and should not compromise the health or long-term value(s) of existing stands.

For silviculture prescriptions, only those areas within a standards unit that exceed the specified maximum density must be spaced. These areas must be spaced to within the specified range of maximum and minimum number of trees to be retained.

Refer to appropriate guidelines when implementing density management activities to manage forage and habitat for wildlife and livestock. E.g. Guidelines for Maintaining Biodiversity During Juvenile Spacing, Guidelines for Integrating Coastal Grizzly Bear Habitat and Silviculture in Coastal British Columbia.

Monitoring

Effectiveness audits are used to determine if Code provisions including Regulations, Policy, and Guidelines are effective, and provide the necessary information to manage stand densities. The Forest Practices Branch will work with forest regions, districts, and the MoELP to carry out effectiveness audits of stand density management procedures and requirements.

Compliance and enforcement inspections are used to determine if on-the-ground operations have achieved the objectives and standards contained in approved SPs. A review of the effectiveness of stand density management standards should be incorporated in the on-going monitoring and inspection of forest practices.

Training

Training of Ministry and industry personnel is an ongoing necessity to ensure consistent application of code provisions, analyses, design, and implementation of stand density management regimes. Persons designing stand density management regimes should attend related training courses.

Responsibilities

Chief Forester:

• provide provincial guidance as to desired future forest conditions that management units should be aimed at producing
• provide the stewardship assumptions and considerations that should be used in the development of stand density management regimes and maximum density numbers
• provide general guidance for the development of maximum density numbers for management units (i.e., TSAs, TFLs, woodlot licences)

Director, Forest Practices Branch:

• maintain stand density management guidelines, procedures, and legislation
• provide training and support for this policy and the Guidelines
• provide support and guidance to regions and districts
• monitor the implementation of legislation and guidelines related to stand density management
• provide training in the use of stand density management decision support tools for silviculture prescriptions

Director, Research Branch:

• develop decision support tools and information
• develop decision support tools that link forest, landscape, and stand level forest practices and consider other uses and values
• develop research information on stand density management for all major geographic areas, treatment types, and regimes
• provide user support for growth and yield decision aids

Director, Timber Supply Branch:

• provide and update forest level models that adequately reflect the effects of silviculture density regimes on the achievement of desired landscape and forest objectives
• provide training in the use of forest level decision aids

Regional Managers:

• provide guidance, training, and support to regional and district staff on stand density management procedures
• monitor the implementation of this policy and the Guidelines
• provide input into the development and update of provincial stand density management guidelines and policies
• consider this policy and the Guidelines prior to establishing new maximum density numbers
• consider existing and future Timber Supply Review documents, management plans, and managed stand yield curves when specifying maximum density numbers
• consider the objectives and direction provided in Land and Resource Management Plans and Landscape Unit Plans respecting timber and non-timber values and uses
• consider information and input from District staff, forest industry, and other appropriate agencies (i.e., MoELP, local livestock associations, BCCA, and range agreement holders) when specifying maximum density numbers
• give written notice of the specification of new maximum density numbers

District Managers:

• only approve new SPs with maximum density numbers that are consistent with the Silviculture Practices Regulation and/or numbers specified by the RM
• ensure that new SPs specify maximum and minimum numbers of trees to be retained after a spacing treatment
• ensure that the post spacing range limited by the maximum and minimum numbers will result in the stand achieving the target future condition(s)
• ensure that stand density management activities are implemented consistent with forest, landscape, and stand level plans and prescriptions
• ensure that any new Timber Supply Reviews only include density management regimes in the analyses that are consistent with current stand density management practices
• ensure that stand density conditions in a management unit are included in the Ministry's corporate data bases

References

• Guidelines for Developing Stand Density Management Regimes
• Forest Practices Code of British Columbia Act, s. 70 (4)(e) and (f); (5); (6);
• Forest Practices Code of British Columbia Act, s. 174(1)
• Operational Planning Regulation, s. 39 (1) (a) (vi) (vii) and 39 (1)(d)(vi)
• Silviculture Practices Regulation, s. 12 & 13
• Ministry of Forests Act, s. 4
• Range Act, s. 3
• Wildlife Management Act, s. 7