Element 4 : Hardwood initiative - Development of new processes and technologies in the hardwood industry (Project 17) - Impact of partial harvesting on tree grade: projections for northern hardwoods of the Acadian Forest Region
The objective of commercial thinning and partial harvesting has traditionally been to improve and increase the amount of higher quality stems for sawlog and veneer products, reduce losses from mortality, and reduce the harvest rotations for even-aged silvicultural systems. Literature on the impact of partial harvesting on stand dynamics, tree grade changes, fibre attributes, and potential forest products to promote uneven-aged and structures and management is scare for the northern hardwood forests of the Acadian Forest Region. A long-term selection harvest study established in west-central New Brunswick provides the opportunity to obtain such information under the FPInnovations and Natural Resources Canada, Canadian Wood Fibre Centre Eastern Hardwood Research Initiative. Results from the study suggest that the treated stands did benefit in the terms of growth and improved quality, but stand restoration is a slow process in the second growth uneven-aged stands on a 20-year harvest cycles. Stand growth responses and tree grade changes for both the control and treated plots are within the values reported for northern hardwood stands and are influenced by a number of treatment and biological factors.
The results of fifteen years of observation are discussed in the context of the major publications existing in the literature for stand dynamics, tree grade changes, and the occurrence of ingrowth. In summary, greater is the basal area removal, the greater the diameter response of individual residual trees in the thinned plots. The thinned stands have not recovered the basal area values that existed at the initiation of this study Annual volume increment growth rates suggest that hardwood stands subjected to partial removals produced better growth response than was predicted at the start of the original study. Stand restoration and stem quality improvement are slow processes that may not be achieved with a first harvest entry in second-growth northern hardwood stands that have had the higher quality trees removed repeatedly in the past. Changes in tree grades were observed to be very dynamic in these second-growth northern hardwood stands because of a number of factors such as initial stem quality, stem growth, mortality rates, harvest rates (both regulated and unregulated), species, and site quality. As expected, ingrowth occurred more frequently in the thinned stands than the control stands. Except for one study site with more “mixedwood” characteristics ingrowth does not exist as a diverse mixture of desired tree species but a secondary canopy of dense American beech and sugar maple.
Hardwood Initiative - Part 5: Development of new processes and technologies in the hardwood industry (Project 16) ; Testing the impacts of tree and stand attributes on the variability of acoustic velocity in standing trees (ST300) and logs (HM200)
Transformative Technologies Program ; Project No. TT5.15
Hardwood Initiative Project is based on two paradigms. First, the end-use potential and value of a wood product basket can be determined by the properties of its wood and should be quantified as much as possible before trees are harvested. Second, as the correlations between site conditions and wood fibre attributes can be changed by silvicultural treatments, it would be possible to optimize the wood production in terms of quantity and quality through a better understanding of silvicultural impacts on changes in wood fibre properties. This document presents the preliminary results of a research component of the project related to acoustic velocity. It focuses on testing the impacts of tree and stand attributes on the variability of non-destructive velocity (ST300 non-destructive measurement in standing tree) and of destructive velocity (HM200 destructive measurement in log). The acoustic measurements were conducted in 30 plots of sugar maple mixed with yellow birch in New Brunswick. Among the trees measured, 64 trees have been subjected to both non-destructive and destructive velocity measurement. Regression analysis by mixed model showed no significant impact of stand attributes (stand basal area and stand height) on the variation of both velocities. In addition, the defects represented by stem deformation, hole, split, wound, and stump swelling, had no significant impact on both velocities. By cons, the test showed a significant correlation between both velocities and dbh and light crown area of the tree. Non-destructive velocity was better explained by dbh and light crown than the destructive velocity. These results open the potential to produce an equation to predict the non-destructive acoustic velocity of the tree using simple tree attributes (e.g., dbh and light crown) as predictors, and to prescribe the thinning intensity for a desired level of velocity and then a desired level of wood density or stiffness.
Full title: Hardwood Initiative - Part 5: Development of new processes and technologies in the hardwood industry (Project 16) : Testing the impacts of tree and stand attributes on the variability of acoustic velocity in standing trees (ST300) and logs (HM200)