Module 3 — Stand level components
of biodiversity
British Columbia
Ministry of Forests
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Module 3, Part B — Wildlife trees — continued
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Individual
live tree retention


  Individual live tree retention has four subheadings:
  • Worker safety issue-wildlife tree retention
  • Common safety problems
  • Worker safety recommendations
  • Recommendations for individual live tree retention

Even though it is the preferred leave strategy, not all blocks can accommodate wildlife tree retention in patches.

Depending on site-specific factors (such as topography, wind exposure, stand age and structure, rotation length, silvicultural system and harvesting method) some locations may be better suited to individual tree retention as a wildlife tree management strategy. 

Individual live trees left as wildlife trees can contribute to the required WTP area retention (see Table 1-A and Table 1-B) on a basal area equivalency basis. However, simple stem basal area does not equate to patch area. (WTP — wildlife tree patches).

Basal area equivalency is only about the amount of basal area. The context here is basal area equivalency is the amount of basal area that is dispersed compared to the amount of basal area in an unharvested patch of trees. 

For example, 40 square metres of basal area could be left in the form of scattered stems distributed over 20 hectares, or as 40 square metres in a patch.

It does not mean the biodiversity or ecosystem functions are equivalent. In fact, the biodiversity value is almost certainly different. The value of residual basal area towards biological diversity relates to the desired objective. The diversity being provided by individual stems is different than that provided by a variety of vertical and horizontal structures, coarse woody debris, forest floor and special habitats found in a patch.

For example, a 1 ha patch containing trees, shrubs, rocky or wet sites, and other ground level diversity is not ecologically equivalent to "x" number of single green stems (such as seed trees) distributed around a harvest block, even if they contain the same basal area.

Individual live tree retention
Individual live tree retention

     
iconCan you think of other reasons for the retention of individual live trees?   Trees can be distributed singly or in small clumps depending on the silvicultural system, operational constraints (slope and topography, harvesting method), and proximity to other habitat features (riparian areas, hardwood patches, gullies, rock outcrops).

Broad-leafed deciduous trees tend to be a preferred tree for nesting and feeding by many cavity excavators, and are less susceptible to windthrow in late autumn and winter when severe windstorms are more common, as a result these trees should be left on site.

Advance regeneration can also be left on the block to provide some structural diversity

     
  next Next: Worker safety issue — wildlife tree retention
 
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