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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Wildlife tree patch composition



 

Wildlife tree patches (WTPs) provide several advantages over other leave strategies: 

  • Potentially dangerous trees can be retained within a no-work zone (the patch). 

  • In some cases, it is operationally easier to retain trees in patches versus individual stems. 

  • Patches provide: an area of undisturbed forest floor within cutblocks, stand structural heterogeneity, and vegetation species diversity. 

  • Patches often provide better habitat for wildlife than scattered individual trees. 

In many cases, WTPs can be located in or adjacent to gullies, rock outcrops, riparian areas, inoperable areas, and other special habitats or locations that are likely to pose harvesting or regeneration problems, or already require special management practices (e.g., riparian management areas). However, to be appropriate wildlife tree patches, these areas must have wildlife tree attributes.

     
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How does this information change or modify what you already knew? 
  A range of tree diameters should be included within WTPs, favouring larger stems when possible (a recommended range is >30 cm dbh (larger on coast/interior wet belt) and >15 m in height). Care should be taken to include the upper 10% of the diameter distribution of the pre-harvest stand as these are the most valuable wildlife trees.

Patches should include both live and dead trees (subject to safety requirements) representing a range of decay classes. In general, class 2 – 6 wildlife trees are most valuable to wildlife over longer periods. 

See Figure 8. British Columbia's wildlife tree classification system

snag

A variety of tree species, including deciduous, should be represented. 

When possible include trees showing wildlife use (e.g., nest holes, feeding excavations) or characteristics of large size, well-branched structure, and presence of heart rot.

     

iconAre there other wildlife tree characteristics?
List them.

 

For example, a valuable wildlife tree might exhibit the following characteristics:

  • Greater than 15 m in height 

  • At least 30 cm diameter (greater on coast/interior wetbelt) at breast height for larger species such as woodpeckers, owls or marten 

  • Broken top or other external defect 

  • Some intact bark and branches 

  • Windfirmness 

  • Minimal lean 

  • Located near a riparian area, if possible 

  • Distributed in a clump or patch with a mix of live and dead trees and vegetation species (hardwoods, conifers, shrubs) 

Wildlife tree patches can be a range of sizes.

They can be a small clumping of several trees or large treed areas covering many hectares. 

The size of a wildlife tree patch is generally determined by the features to be maintained within the patch and safety considerations (the size of the no work zone).  However, larger patches are generally better from a habitat and operational perspective.

It is suggested that the interpatch distance requirement be met by wildlife tree patches 0.25 hectares or larger. 

However, individual wildlife trees play an important habitat role, especially when combined with wildlife tree patches. 

Where individual wildlife trees are reserved, an appropriate basal area equivalency can be calculated for their contribution to patch retention requirements (to be considered wildlife trees, these trees should be retained for an entire rotation).

     

Wildlife tree patch distribution —
Inter-patch distance

iconIn your experience, have enough patches been left in BC forests? If not, how can this be changed?


 

The importance of wildlife tree patches within cutblocks increases with size of the cutblock.

  • The overall objective for distribution of wildlife trees is to retain WTPs across the landscape. 

  • At the stand level, patches should generally be centred around the most suitable trees and be distributed throughout the cutblock — based on available suitable habitat features on the block.

Where operationally feasible, more patches should be left within cutblocks to achieve biodiversity, visual, water quality, or other objectives.

     
  next Next: Recommendations and applications
 
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