Forest Science Program

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Ecosystem and tree attributes affecting the presence of functional wildlife tree types

Author(s) or contact(s): B.H. Heemskerk, B.J. Rogers, and S.C. DeLong
Source: Forest Science Program
Subject: Ecosystems, Wildlife Trees
Series: Technical Report
Other details:  Published 2009. Hardcopy is available.


Wildlife Trees play a significant role in maintaining species richness in forested ecosystems by providing critical habitat. This study was completed to develop a better understanding of the relationship between ecosystem and tree attributes and an established functional Wildlife Tree type classification. Data from four studies conducted in different ecosystems in central British Columbia are compared in this paper. The four study areas were: (1) boreal aspen forests, (2) mixed conifer forests in the boreal foothills, (3) mixed conifer forests in the moist interior plateau, and (4) mixed conifer forests in the interior wet belt.

In each study area, tree species were evaluated by diameter classes for the percentage of live versus dead stems and functional Wildlife Tree types based on an existing classification system, and results within and among study areas were then compared. The combined tree sample size totalled almost 19 300 stems, comprising 10 different tree species. To provide a link to provincial Wildlife Tree policy, each tree's value was ranked using guidelines established by the provincial Wildlife Tree Committee.

We found that both the number of trees displaying at least one functional Wildlife Tree type and the number of functional types per tree showed a positive trend with increasing diameter of dead stems. This trend varied amongst tree species. Our study results show that black cottonwood (Populus bal-samifera L. ssp. trichocarpa), trembling aspen (Populus tremuloides Michx.), western redcedar (Thuja plicata Donn ex D. Don), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) provide the greatest diversity of functional Wildlife Tree types.

Findings from the four study areas suggest that large-diameter trees of certain species must be maintained within forests in order to avoid the loss of distinct structural attributes, represented by functional Wildlife Tree types, which provide important habitat for many wildlife species. This information provides a basis for understanding the variability and similarities among different ecosystems of unique structural characteristics of Wildlife Trees, thereby providing resource managers with ecosystem-specific information and helping to avoid generalized prescriptions that may not reflect the managed sites in question.

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Updated March 20, 2009