|GUIDELINES for||. . .|
|Developing Stand Density Management Regimes|
Silviculturists place great importance on practicing "good" silviculture by carefully selecting and prescribing appropriate interventions based on stand-specific considerations. Frequently, however, the connection between stand-level silviculture and forest management objectives is not made. The absence of this critical linkage means that stand-level interventions are undertaken with little appreciation of their effects on forest resource supply requirements (i.e., timber quality, size, harvest flow, location and species).
Stand-by-stand silviculture often assumes that a series of individual stand treatments results in an additive impact on resource supply at the forest level. Baskerville (in Kelty et al. 1992) warns that the effects of stand-level actions are usually not additive at the forest level. He suggests that stand-by-stand silviculture ignores the complex interaction of factors influencing resource supply, and reduces the likelihood of successfully controlling forest dynamics to achieve management objectives. For example, harvest flow considerations may force the advance or delay of harvests from the planned harvest ages that would have maximized the gain from a particular treatment. Thus the expected yields from stand-level planning may not be realized at the forest level.
A forest management strategy should be the guiding reference for stand-level silviculture (Reed and Baskerville 1990). The relative "goodness" of a silvicultural intervention is difficult to judge unless viewed within a strategic context. In this context, even basic silviculture expenditures are difficult to evaluate objectively, except in terms of discharging legally binding reforestation obligations.
A comprehensive forest management strategy is therefore necessary before rational choices of stand-level interventions can be made. For example, without a strategic context, local stand density management interventions may result in:
The purpose of this section is to describe the forest-level context within which stand-level density management decisions are made. Specifically, this section examines the nature of forest-level objectives, their relationship to higher level plans, the strategies developed to meet those objectives, and how these strategies govern the selection of stand density management activities.
The next section describes a decision process for designing a forest management silviculture strategy. A thorough discussion of the theory and practice of forest management is beyond the scope of this document. Readers interested in the subject are encouraged to review the extensive literature available, a small sample of which is referenced here.
The following definitions may assist the reader in the ensuing discussion:
stand - A contiguous group of trees sufficiently uniform in species composition, arrangement of age classes, and condition to be a homogeneous and distinguishable unit.
forest estate - A collection of stands, of varying types, ages, etc., administered as an integrated unit and managed for some continuity or flow of harvest volume. For the purpose of this document, the forest estate is synonymous with the sustained-yield unit which includes timber supply areas, tree farm licences and woodlot licences.
forest-level objectives - Objectives established for the forest estate.
Higher level planning, as used in forest management in BC today, refers to the hierarchical system of planning established under the Forest Practices Code of British Columbia Act (the Code). Under the Code, the following hierarchy has been established, where the highest level of plan is objectives for resource management zones, followed by objectives for landscape units, objectives for sensitive areas, and objectives for interpretive forest sites, recreation sites and recreation trails.
In a hierarchical planning process, higher level plans guide plans lower in the hierarchy. For example, objectives established for a landscape unit are guided by the objectives established for a resource management zone. The Code also stipulates that operational plans, such as stand management prescriptions (which may include density management activities), must be consistent with higher level plans.
At the same time, actual operational conditions provide guidance to the levels higher in the hierarchy. For example, planning delays or limits in budgets or other resources may result in amendments to plans higher in the hierarchy.
Forest-level objectives, which will guide stand-level activities, are embodied within resource management zone objectives and landscape unit objectives for all Crown land, and within management plans for TFLs and woodlots. For more information on higher level planning, refer to Higher Level Plans: Policy and Procedures (B.C. Min. For. 1996b) as well as A Guide to Landscape Unit Planning7 and A Guide to Writing Resource Objectives and Strategies (B.C. Min. For. 1998).
Copyright 1999 Province of British Columbia