Interest in managing broadleaf and mixedwood stands has grown due to increased demand for hardwood products and a shift towards more biological/ecosystem-based management. The current default operational practice is the elimination of the non-conifer component of the stand. Presently, there are no silviculture guidelines for managing mixed species stands in the sub-boreal spruce (SBS) biogeoclimatic zone. When managed, they tend to be managed poorly due to a limited understanding of their dynamic processes and a lack of predictive models. Our current quantitative findings as well as model projections suggest spruce growth is promoted when growing at birch densities up to 2000 2500 sph. A similar observation was made for lodgepole pine with aspen but the aspen threshold is considerably lower, about 500 sph. White pine weevil (WPW) attack on spruce was also significantly reduced with a deciduous overstory. The birch density threshold in this case appears to about 2000 sph. Land expectation values based on our model projections indicate mixedwood management is a much better investment than our current operational default. If the deciduous density thresholds are similar for both spruce growth and WPW attack, the economic analysis is underestimating the return from mixedwood management. Logs from the mixedwood stand will have fewer WPW induced defects and smaller branches, i.e. greater value. Managing complex stands in the SBS will improve site utilization through enhanced productivity and increased species and structural diversity.
J. Lange, K. Menounos, C. Hawkins, Thomas Steele.
Hawkins, Chris D.B., Steele, Thomas W.; Lange, J.; Menounos, Kimberly. 2004. Sustainable mixedwood management, growth and yield and wood quality in SBS mixedwood stands. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report