Research Branch

See below to download Extension Note 72 PDF file.

The Opax Mountain Silvicultural Systems Project: Preliminary Results for Managing Complex, Dry Interior Douglas-fir Forests

Author(s) or contact(s): D.J. Huggard, A. Arsenault, A. Vyse, and W. Klenner
Source: Research Branch
Subject: Silvicultural Systems
Series: Extension Note
Other details:  Published 2005. Hardcopy is available.


The Opax Mountain Silvicultural Systems project explores management options for some of the issues facing managers of complex forests in the dry Interior Douglas-fir (IDF) biogeoclimatic zone. The project includes two study areas: one in the IDFxh2 variant and one in the IDFdk2. Each area has six operational-scale harvest treatments: uncut control; 20% removal of merchantable volume using individual tree selection (ITS); 50% ITS; 50% ITS with uncut reserves; 20% removal using a mixture of patch cuts of 0.1, 0.4, and 1.6 ha; and 50% removal with patch cuts of a similar nature as the 20% removal.

The project includes studies of:
- fire history and other natural disturbance agents;
- regeneration in openings and under partial canopy;
- edge effects on microclimate, snowmelt, and soils;
- effects of canopy density, gap sizes, site preparation, and edges on planted seedlings, natural regeneration, and vegetation (including cover layers, individual species, and groups such as forage plants, weeds, soil seedbanks, and ectomycorrhizal hosts); and
- harvest treatment effects and habitat relationships of wildlife groups, including terrestrial invertebrates, arboreal beetles, small mammals, songbirds, woodpeckers, and ungulates.

We summarize results for many of the individual studies at Opax Mountain, dealing with the important management issues of natural disturbance regimes, regeneration, management of vegetation resources, and conservation of biological diversity in managed dry IDF stands. Natural disturbances at the site cover a wide spectrum of sizes, frequencies, severities, and effects on stand structure. Responses of the many study variables show that no one management treatment will maintain all valued components in the IDF forest. Together, these results support the use of a range of management practices broader than the current uneven-aged management widely practiced throughout the dry IDF biogeoclimatic zone. In particular, patch-cut systems with openings >0.1 ha, or extended rotations to permit the development of large live trees, snags, and coarse woody debris would complement individual tree selection systems.

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Updated April 18, 2007