Forest Investment Account (FIA) - Forest Science Program
FIA Project Y073305

    Managing northern mixedwood stands to sustainably maximize productivity and minimize costs
Project lead: Hawkins, Chris
Author: Hawkins, Chris D.B.
Imprint: Prince George, B.C. : University of Northern British Columbia, 2007
Subject: Forest Investment Account (FIA), Forest Management, British Columbia, Picea Glauca, Growth
Series: Forest Investment Account (FIA) - Forest Science Program
This LoI-C best fits topic 3.1 - complex stands: developing and improving long range growth and yield models, improving timber production and value in boreal mixedwood stands, and further development of decision tools for long term stand management. The aim of this project is to determine the density of broadleaf stems that maximizes complex stand productivity, minimizes costs associated with achieving free-growing objectives, and models growth and development of these complex stands. This will provide the basis for a more strategic approach to brushing programs including allocating activities where necessary and avoiding treating areas where a mixedwood stand is an appropriate and desirable condition on the landscape. Results should reduce the amount of administrative brushing done in the Northern Interior Forest Region. A recent Timber Supply Review of the Dawson Creek Timber Supply Area (1) identified the need to manage mixedwood stands to maintain their attributes on the landscape – to stop 'unmixing the mixedwood' forest. The first phase (2004-05) involved the collection of data to determine the threshold density of broadleaf trees in unmanaged stands that maximizes stand productivity without hindering conifer growth. The second phase of the project involves the development of a response surface to evaluate the data collected in the first year, and to remeasure some plots in order to monitor growth rates which will be incorporated into models. These models will serve as decision support tools for evaluating brushing needs, impacts of management activities, and short- to long-term timber supply and quality. It is suggested that the productivity of mixedwood stands in boreal regions is higher over the long term than single species or conifer regenerated stands (2). Further, it has been suggested that species mixtures (aspen-spruce, birch-spruce) result in greater wood volumes than single species stands and that some of the benefits of natural stand dynamics may be realized by managing for complex mixtures. However the current operational 'default’ of eliminating most or all non-coniferous tree species is costly and reduces species and structural diversity (3). The cost of carrying out brushing treatments to meet free-growing guidelines in much of the province may be unjustified. As part of the Adams Lake Interfor Innovative Forest Practices Agreement (4), studies showed that the cost of brushing birch from blocks planted to lodgepole pine may be higher than anticipated increases in value (enhanced wood quality and volume increases). Current free-growing guidelines (5) require the removal of deciduous competition species despite evidence suggesting that it is not cost-effective, and does not typically result in higher timber volumes or better wood quality. In fact, wood quality may be compromised. Complex or intimate mixtures are seldom managed for, and they tend to be managed poorly. The 2002 Dawson Creek Timber Supply Review identified a gap in management in northern complex stands, and the Chief Forester stated that if these stands were not managed, they would be removed from the area’s allowable annual cut (1). The lack of management is due to a limited understanding of the dynamic processes in complex stands and a lack of predictive growth and yield and successional models. There is limited quantitative information available on how these stand types develop during early seral stages and what the short- to long-term growth and yield implications might be. A better definition of how biological and economic values interact will lead to reduced brushing costs from unnecessary manual or chemical treatments, and an increase in stand-level and landscape-level diversity. However, the impacts on growth and yield or future timber and fibre supply are poorly understood. In the first year (2004-05), this project examined growth responses of young (up to 15 years old) spruce and pine stands to varying densities of residual birch or aspen with the establishment of temporary sample plots (TSPs) and destructive sampling of saplings (for conifer and deciduous height over age curves) in Fort Nelson and Mackenzie TSAs. These data will provide species-density thresholds found in unmanaged stands for modeling (including growth and yield) of early stand development, linking early stand development to desired future forest conditions and longer term yield predictions. In year two (2005-06), a quantitative response surface (a visual representation of species-density thresholds) will be created to explore conifer growth relative to manipulated, broadleaf stem densities. This step is necessary to understand the evolution of the deciduous densities from early, unmanaged stand development encountered in TSP establishment in year one to manipulated deciduous densities that would occur in vegetation management treatments. An experimental manipulation of broadleaf density is needed to enhance first year findings for incorporation into growth and successional models. In year three (2006-07), we will remeasure some plots from years one and two to monitor crop tree growth with respect to density. Each new established site will contribute to a network of documented research sites: future data from these can be used to validate model projections. Part two of this study uses another trial (EP1192.01) established in the Fort Nelson area by Harper and Biring (6) to look at spot vegetation control in comparison to complete and no vegetation control. These data will allow recommendations to be made about the most effective way of obtaining the desired deciduous densities outlined in part one. The overall objectives of this project are to: 1. Determine the threshold level of deciduous (birch, aspen) vegetation that is deleterious to white spruce or lodgepole pine growth; 2. Project treatment growth over a rotation for both coniferous and deciduous species; 3. Evaluate the effectiveness, impacts, costs and benefits of spot control of deciduous species around white spruce compared to broadcast or no treatment; 4. Determine the cost-benefit of all vegetation control methods currently used in Mackenzie and Fort Nelson TSAs;
Related projects:  FSP_Y051305FSP_Y062305
Contact: Hawkins, Chris, (250) 960-5614,


Executive Summary (47Kb)

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Updated August 16, 2010 

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