This study examines the long term effects of precommercial thinning (PCT) on tree growth, wood characteristics and product quality and value in natural balsam fir stands. In Eastern Canada, little information is available on the long term effects of intensive silviculture on tree growth and concurrent changes in wood quality and value.
The Green River PCT trials, located about 80 km north of Edmundston in New Brunswick, were established between 1959 and 1961 to evaluate the long-term responses of balsam fir and spruce to PCT. Three nominal spacings, 4 ft (1.2 m), 6 ft (1.8 m), and 8 ft (2.4 m), were applied for comparison with an unthinned control in a randomized complete block design with 5 replicates. For the purpose of the present study, only 3 of the 5 replicates were assessed for wood quality. In 2008, or forty years after PCT treatment, sample trees were collected from each tree DBH class for wood quality evaluation. A total of 160 trees were measured, bucked into random-length (8-16-foot) logs, and converted into lumber in a modern sawmill. For each PCT spacing, wood chips were collected for evaluating the quality of medium density fibreboard (MDF) panels. Each piece of lumber was visually graded and tested in static bending to determine its lumber stiffness (MOE) and strength (MOR). Based on these sample trees, the impact of PCT spacing on product quality and value was evaluated at the DBH class level and at the stand level.
PCT had a positive effect on tree growth 48 years after treatment. The average tree diameter increased from 19.8 cm in unthinned control plots, to 23.5 cm (19%) in the 8’ spaced plots. Merchantable stem volume per tree increased from 277.1 dm3 to 381.1 dm3 (38%). Stand volumes from the control to the largest (8’) spacing were 281 m3/ha, 297 m3/ha, 310 m3/ha and 338 m3/ha, respectively. PCT had also a positive impact on Premium lumber grade recovery ranging from 18% in the unthinned control to 22% in the 8’ spacing. Through the same range of spacings, No. 2 & Better grade yields were 83.7%, 89.3%, 85.6% and 78.9 %, suggesting a slight decrease at the largest spacing. Total product value per tree was $29.09 in the unthinned control, and $31.07, $36.31 and $40.23 in the 4’, 6’ and 8’ spacings, respectively, representing a maximum value increase of 38%. PCT at 6' & 8' also increased the production of 2x6 & 2x8 by about 9 % compared to the control. Forty-eight years after treatment, all the spacings increased stand product value compared to the unthinned control: $25,222/ha (control), $29,942/ha (4’), $27,368/ha (6’) and $30,151/ha (8’). The Summit Road replicate, which was about 8 yrs older (70 years) than the two other replicates at Upper Belone (62 years), had markedly lower total product value recovery, indicating stand degradation. If the Summit Road plots are excluded, the stand product values for the control, 4’, 6’, and 8’ spacings become $27,402/ha, $35,200/ha, $32,948/ha and $31,911/ha, respectively.
Modulus of elasticity (MOE), or lumber stiffness, decreased slightly with increasing PCT spacing, from a maximum of 8233 MPa in the control, to 8175 MPa, 7937 MPa and 7961 MPa in the 4’, 6’ and 8’ spacings, respectively. Similarly, the modulus of rupture (MOR), or lumber strength, decreased steadily from 31 MPa in the control, to 30 MPa, 29 MPa and 28 MPa through the same range of spacings. Thus, compared to the control, the 8’ spacing had a minor negative impact on lumber MOE (–3.4 %) but a more appreciable negative impact on lumber strength (–8.9 %). Compared to the control, the 8’ spacing slightly decreased wood density by 3.7 % (340 kg/m3 vs. 328 kg/m3). Overall, the PCT spacings studied had a moderate negative impact on lumber mechanical properties. The sawmill wood chips from the control and the thinned stands (4’, 6’ & 8’) are all suitable for the production of good quality MDF panels. All MDF panels produced had very good strength (MOR) and stiffness (MOE), with little difference between product from thinned and unthinned stands.
In conclusion, this study shows that PCT in highly productive balsam fir stands is a viable silvicultural treatment that increases stand volume and solid-wood product value per hectare at the end of the rotation. On a total stand product value per ha basis, the 4’ spacing ranks as the best option, followed by the 6’ spacing. From a wood quality perspective, considering that the 8’ spacing decreased lumber MOE/MOR the most, it is recommended to thin young balsam fir stands to a maximum of 6’ (1.2 m) in order to limit the decrease in lumber mechanical properties. In this study, the 6’ spacing appears as the best compromise between stand volume production and solid-wood product quality and value. Thinning to a maximum of 6’ offers the advantage of minimizing the risk of loosing too many crop trees over time, in case natural perturbations occur, and potentially the opportunity to perform a commercial thinning if so desired.
Stream networks shown on public maps are often incomplete and their accuracy fails to meet the full needs of forest managers. Stream Network Extraction (SNE) from a LiDAR Digital Elevation Model (DEM) has the potential to add to the already mapped streams and provide more hydrographical information. This report describes the potential of two different SNE programs with a LiDAR-derived DEM.
Engineered wood flooring (EWF) is gaining in popularity since it appeared in Europe in the 70’s. 40% of the wood flooring installed in the USA is EWF and 75% are EWF in Europe. In layered wood composites such as engineered wood flooring, dimensional stability is of primary importance. The non-homogeneous adsorption or desorption of moisture by the composite may induce cupping, thus decreasing product value. These products were developed by the industry with the result that knowledge on the product and its behaviour is very limited. The objective of this study is to develop a finite element model of the hygromechanical cupping induced by moisture desorption in layered wood composites. The model is based on two sets of equations, 1) the three-dimensional equation of unsteady state moisture diffusion, and 2) the three-dimensional equations of elasticity including an orthotropic Hooke’s law, which takes into account the shrinkage, and swelling of each layer. The model was used to assess 34 different constructions. Results may be used as guideline in the design of new engineered wood flooring construction.
This report presents a survey of the performance of wood-frame construction in a number of recent earthquakes. After a review of the dominant factors that affect the seismic behaviour of buildings, the following earthquakes are examined: Alaska, 1964; San Fernando, California 1971; Edgecombe, New Zealand, 1987; Saguenay, Quebec, 1988; Loma Prieta, California 1989; Northridge, California, 1994; and Kobe, Japan 1995. Wherever possible, the behaviour of buildings is related to the measured peak horizontal ground accelerations. The survey shows that despite some specific shortcomings and resultant failures, a majority of wood-frame buildings of various ages, when subjected to peak ground accelerations of 0.6 g and greater, survived the shaking without serious structural damage or collapse and with very few resulting injuries and deaths. Thus, the life-safety criterion that is implicit in building codes is largely satisfied. In addition, many modern wood-frame buildings survived such shaking without any visible damage. The few observed failures and collapses could be traced primarily to specific instances of lack of lateral bracing, weak first storey, inadequate connection to foundations and the fact that the observed ground motions far exceeded the then-existing design requirements. The observed shortcomings have been and are being addressed by researchers and practitioners in order to eliminate these adverse effects in future earthquakes. The research program at Forintek Canada Corp. is highlighted, aimed at improved seismic behaviour of wood-frame construction and the subsequent implementation into design guides and codes and standards. Studies on joints, shear walls, mathematical modelling and development of codes and standards are discussed. Finally, for existing buildings that do not meet current seismic standards, guidelines available in the USA and Canada for screening, evaluation and upgrading are presented. It is concluded that wood-frame construction can withstand the shaking from large earthquakes without serious distress and often without damage provided that appropriate anti-seismic procedures are followed by designers, builders and owners.
This paper describes and evaluates new and existing models for exterior log geometry. Compatibility with 1,2,3, and 4-axis shadow scanners determined which models were selected for evaluation. Models were considered for potential use in sawmilling process simulation and optimization. The accuracy evaluation compared models based upon lost and added fiber percentages. All models tended to overestimate log cross section area. Popular circular and elliptical models provided the poorest accuracy. Elliptical models used with 2-axis or 3-axis scanners generated up to 8% lost fiber and up to 15% added fiber. The 3-axis dyadic and Chaikin models provided the best overall performance : lost fiber under 3.5% and added fiber under 13%. Results from the evaluation recommend a 3-axis scanner system for automatic positioning and breakdown optimization. The small benefit obtained from 4-axis models does not justify their use. Other technologies are recommended where better accuracy is needed.
Ce projet constitue le programme d'etude de maitrise d'une etudiante (Annick Tremblay) du departement d'informatique de l'Universite Laval. Les objectifs etaient de developper un algorigthme d'optimisation des operations de delignage et d'eboutage ainsi que de proposer un algorithme effectuant le positionnement optimal des pieces a debiter. L'algorithme choisi pour le delignage et l'eboutage est fonde sur une technique d'optimisation appellee programmation dynamique. Pour sa part, l'algorithme de positionnement fait appel a une technique de subdivision d'intervalles. L'algorithme de positionnement ameliore de 76% le temps de traitement par rapport a l'algorithme de recherche exhaustive (force brute) generalement utilise.
Ce projet consiste a diriger en collaboration avec un professeur de l'Universite Laval une etudiante inscrite a la maitrise au departement d'informatique de la Faculte des sciences. Le sujet de la recherche concerne l'optimisation des operations de delignage et d'eboutage. Ce rapport fait etat de l'avancement des travaux.