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Biodiversity Guidebook Table of Contents]

Stand management to maintain biodiversity

This chapter describes how specific objectives for maintaining stand structure, tree and vegetation species composition, and coarse woody debris can be determined.

A fundamental premise for maintaining biological diversity is to implement strategies at both the landscape and stand scales. There is a linkage between how much retention of stand structure is required at the stand scale and how much should be retained at the landscape scale. When landscape units have been designated and landscape level biodiversity objectives have been established then the requirement for maintaining biodiversity in individual stands can be reduced and the appropriate retention levels determined from Table 20(a). As a result, the development of landscape unit objectives will allow for greater flexibility at the stand level. When no landscape unit biodiversity objectives have been established, then appropriate retention levels should be determined from Table 20(b).

The recommendations in this chapter should be applied in the preparation of:

Objectives for wildlife trees and coarse woody debris must be included in the contents of a Forest Development Plan (OPR 15 (7) (b)). A Forest Development Plan (OPR 15 (2)) and a silviculture prescription (OPR 39 (2) (w)) must contain a reasonable assessment of non-timber resource values known to be on or adjacent to the plan area and must describe the actions to be taken to accommodate those values.

Stand level practices in this chapter are the recommended minimum requirements needed to meet the structural characteristics of natural openings (OPR 21(3)(b)).

When wildlife tree patches (group reserves) are larger than 2 ha (a patch that is isolated within the cutblock boundary and not included within the net area to be restocked) and also meet the age and structural requirements of old seral forest (see “Establishing landscape unit biodiversity objectives”) then these larger, within-block patches can contribute to old-seral stage forest requirements within the landscape unit and be used in landscape level retention calculations (OPR 39 (3)(d)). A wildlife tree patch is synonymous with a group reserve in silvicultural terminology.

Given the high degree of ecological variability in our forests, managers need to consider biological diversity on a site-specific basis in order to most effectively apply the recommendations presented in this chapter. This variation may require exceeding the minimum retention requirements recommended in this guidebook.

The recommendations for maintaining biodiversity are an important component of ecosystem health and will have to be integrated with other objectives for forest health.

Maintaining stand structure

Stand level recommendations are designed to maintain or restore, in managed stands, important structural attributes such as wildlife trees (including standing dead and dying trees), coarse woody debris, tree species diversity, and understorey vegetation diversity. Appendix 5 discusses in more detail the importance of these structural attributes to the maintenance of biodiversity. The Stand Level Biodiversity Course for Forest Workers and Stand Level Biodiversity Course for Forest Managers offer a more in-depth approach to stand level biodiversity management. The Wildlife/Danger Tree Assessor’s Course Workbook contains single stem safety assessment procedures.

Safe work practices

Safe work practices, as established in conjunction with Workers’ Compensation Board, must be followed at all times when implementing the recommendations in this guidebook. Forest workers should have freedom to remove obstacles whenever necessary to maintain a safe working environment. Trees that are marked to leave or are outside the cutblock boundaries can be felled for safety reasons, but should be left on the ground as future coarse woody debris. This will retain the benefit these trees can have on site and remove any incentives for felling and harvesting.

Wildlife trees

A wildlife tree is any standing live or dead tree with special characteristics that provide valuable habitat for conservation or enhancement of wildlife. These trees have characteristics such as large size (diameter and height) for site, condition, age, and decay stage; evidence of use; valuable species types; and relative scarcity. They serve as critical habitat (for denning, shelter, roosting, and foraging) for a wide variety of organisms such as vertebrates, insects, mosses, and lichens.

Maintaining wildlife trees within harvest and silviculture units can be ecologically beneficial in a number of ways. While standing, they provide habitat for many species (birds, bats, and other small mammals) that perform roles in maintaining ecosystem functions. Standing green trees can provide for future wildlife tree recruits. Wildlife trees will, over time, become sources of coarse woody debris and finally, through decay and nutrient cycling, become incorporated into second-growth forests.

Wildlife tree management strategies can range from the retention of existing wildlife trees, as scattered individuals or in patches, to the creation of new wildlife trees. Many approaches can be applied within a single cutblock, though retention of patches is recommended as the priority approach in most cases. Wildlife tree requirements apply to the use of all silvicultural systems.

Wildlife trees patches (group reserves) and individual live tree retention

Wildlife tree patches (WTP) provide several advantages over other retention strategies. Snags or other potentially dangerous trees are more easily retained in patches than as individual trees and operational inconvenience is minimized. There is also evidence that clumps of trees provide better habitat for birds than do scattered individual trees, as well as an area of relatively undisturbed forest floor within cutblocks. However where scattered individual wildlife trees already exist they should be retained.

Wildlife tree patches should be well distributed across the landscape. The maximum distance between WTPs (500 m) has been based on territory size and dispersal requirements of wildlife.

Recommendations:

Area and distribution of patches or individual trees:

Patch and live tree retention characteristics:

Management principles for wildlife trees

Table 20(a). Percentage of a cutblock area required as wildlife tree patches when landscape units have been designated and landscape level biodiversity objectives have been established

Table 20(b). Percentage of a cutblock area required as wildlife tree patches when landscape units have not been designated

Application of table 20(a) and (b)

This is a one-time calculation for each biogeoclimatic subzone within the landscape unit (or interim landscape unit or portion of a forest development plan forming a contiguous geographic unit) unless the landscape unit objectives change, a new landscape unit is designated, or operability limits change (changing the area available for harvest). A separate prescription is made for each subzone within the landscape.

X-axis numbers (columns) are the proportion of the subzone within the landscape unit (or interim landscape unit or portion of a forest development plan forming a contiguous geographic unit) that is identified as available for harvest (that is, not inoperable or in some sort of reserve status, such as riparian or protected area). Y-axis numbers (rows) are the proportion of the available landscape (above) that has already been harvested without application of this guidebook’s recommendations or similar prescriptions.

Example:

For each biogeoclimatic subzone in the landscape unit (Table 20(a)), calculate the area available for harvest (the X-axis). For example, if 30% of the SBSmc area is available for harvest, then, using the 30% column, the recommended minimum proportion of each cutblock to be managed for wildlife trees is between 1 and 9%. If 50% of the available area has already been harvested without application of these or similar guidelines (Y-axis), then 5% of each new cutblock would need to be left for wildlife tree patches. This can be distributed adjacent to cutblocks in riparian or other long-term leave areas when feasible. Where landscape units have not been designated, the same calculation can be done using Table 20(b).

Examples of how to apply this process to a proposed cutblock are shown in Figures 8 to 10.

Creating wildlife trees

One method of creating wildlife trees is to high-cut stumps during the use of feller bunchers. This creates standing dead trees called “stubs” (see Figure 11). These provide structure within second-growth forests and create future coarse woody debris. They cannot, however, replace all attributes associated with full height wildlife trees and thus can not be used as a complete substitute.

Recommendations:

Figure 8. Applying wildlife tree management recommendations to a proposed cutblock.

Figure 9. Reserves for wildlife trees incorporated into four silvicultural systems.

Figure 10. Harvesting areas with wildlife trees maintained in a riparian management area and a gully complex.

Figure 11. Artificially created wildlife trees (stubs).

Other stand structure recommendations

Any action that encourages structural diversity within managed stands can have value to biodiversity.

Recommendations:

Maintaining tree and vegetation species composition

The maintenance of the diversity of naturally occurring plant species is key to the maintenance of biological diversity within landscape units. Within cutblocks, several actions can help maintain that diversity.

Recommendations:

Maintaining coarse woody debris

Maintaining coarse woody debris after harvesting is a critical element of managing for biodiversity. However, it is recognized that this requirement conflicts with existing utilization standards. Work is under way to resolve this policy conflict. Until this issue is resolved, utilization standards will take precedence over requirements for coarse woody debris.

Despite this policy conflict, some existing practices can be modified to help address the requirements for coarse woody debris. For example, preliminary indications are that post-logging residue and waste can meet the volume requirements for coarse woody debris if it is well distributed across the entire stand. This will not be the case in situations of whole-tree harvesting, clean site preparation practices, or excessive salvage of material not considered merchantable under current utilization standards.

Recommendations:


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