La technologie de séchage par haute fréquence en continu développée par FPInnovations et Hydro-Québec a récemment été démontrée à l’échelle semi-industrielle (précommerciale) (Lavoie et al. 2015). Les essais de séchage ont porté principalement sur des applications de produits à valeur ajoutée. La technologie est viable techniquement et peut répondre à des besoins de séchage de précision pour des applications spécifiques. La technologie a également le potentiel de resécher des pièces demeurées humides (volontairement ou involontairement) lors de la production de bois d’œuvre.
The objectives of the research project is to examine the short term (5 years) response of commercial thinning on tree growth, wood characteristics and product quality and value in a white spruce plantation located in Northeastern Ontario. While mechanized commercial thinning just recently became a more prevalent silvicultural prescription in the softwood forests and plantations of Eastern Canada, little information is available on the effects of intensive silviculture on tree growth and concurrent changes in wood properties.
In 1969, the study site was planted with bareroot white spruce seedlings at a spacing of feet. In 2003, when the plantation was 34 years old, a mechanical commercial thinning was conducted in a portion of the stand, and permanent sampling plots were established in both the control area and the thinned area. The thinning trails were 18 m apart and 5-6 m wide, representing approximately 30% of tree removal. At the time of thinning, the stand density was 2700 trees per hectare, of which approximately 60% were white spruce and the rest aspen, balsam fir and black spruce.
Five years later in 2008, sample trees were collected from each tree DBH class in the thinned area besides the permanent plots. Trees representing the control area (no thinning) were sampled from the buffer area of the thinning to maintain the integrity of the control area. The buffer area was a 15-20-m-wide strip, and trees were sampled in the middle of the strip and sampling was avoided in places where the strip was narrow (<18 m). The middle of the buffer area should represent the growth condition of the control area. A total of 56 trees covering 10 – 22 cm DBH classes was sampled and bucked into 2.5-m (8-foot) long logs. Lumber conversion was carried out with a portable sawmill. After kiln drying and planing, each piece of lumber was visually graded and tested in static bending to determine its lumber stiffness (MOE) and strength (MOR). Based on the sample trees, the impact of commercial thinning was evaluated at both the DBH class and stand levels.
White spruce responded moderately to commercial thinning 5 years after the treatment, in terms of individual tree growth. The average tree diameter increased from 13.1 cm in the control to 14.1 cm in the thinning, which represent about a 7% difference following the thinning. Merchantable stem volume per tree increased from 106.1 dm3 in the control to 125.1 dm3 in the thinned area, which is about 18% gain. No differences were observed in lumber volume, value and dimension recoveries between the control and thinned areas 5 years after commercial thinning.
For the sample trees, the Select Structural lumber grade recovery was slightly higher for the thinned area (29.1%) than for the control area (25.4%). Similar trend was observed for the No.2 & Better grade recovery. At the stand level, the Select Structural grade recovery and the No.2 & Better grade recovery were comparable between the two treatments. No differences were found in lumber stiffness and strength between the control and thinned area. The lumber modulus of elasticity (MOE) was 7.38 GPa and 6.92 GPa and the modulus of rupture (MOR) 35.8 MPa and 34.9 MPa in the control and thinned area, respectively.
In conclusion, based on this study, commercial thinning showed moderately positive effect on individual tree growth, however, no considerable difference in wood properties, lumber recovery and lumber quality was found between the control and thinning treatment 5 years after the commercial thinning. The effects of commercial thinning on tree and wood characteristics, lumber recovery, lumber quality, and economic return should be examined over a longer period of time.
This study examined the long-term effects of initial spacing on tree growth, wood characteristics and product quality and value in white spruce. The study is based on the oldest initial spacing trial established by the Ontario Ministry of Natural Resources in Thunder Bay. Three plantation spacings were examined: 1.8 m, 2.7 m and 3.6 m. 58 trees were sampled across the DBH classes present, bucked to maximize the production of 16 ft-long logs, and converted into lumber. Each piece of lumber was visually graded and tested in static bending to determine its lumber stiffness (modulus of elasticity, MOE) and strength (modulus of rupture, MOR), and MSR grade.
Sixty years after establishment, individual tree growth was greatly favoured by larger spacings. Tree diameter increased by 39% and 66% in the 2.7 m and 3.6 m spacings, respectively, compared to the narrowest 1.8 m spacing. This resulted in a remarkable volume increase of 129% and 159%. Stem taper increased from 0.93 cm/m in the 1.8 m spacing to 1.40 cm/m in the largest spacing. Lumber volume proportions of No.2 & Better grades were 85.7%, 86.8% and 80.4% in the 1.8, 2.7 and 3.6 m spacings, respectively. Expectedly, increased initial spacing favoured the production of large piece size. The volume proportion of 2x8 was 25.5% and 10.2% in the 3.6 m and 2.7 m spacings, but only 0.4% in the 1.8 m spacing. The 2.7 m spacing yielded the best total product value (lumber, chip, sawdust) per hectare ($50,817/ha), followed by the 1.8 m spacing ($44,043/ha). However, the 3.6 m spacing yielded the lowest plantation value ($37,231/ha) because of its low initial stocking.
Lumber stiffness decreased markedly with increasing spacing, from a maximum of 9427 MPa in the 1.8 m plantation, to 8031 MPa and 7476 MPa in the 2.7 and 3.6 m spacings. Similarly, through the same range of spacings, lumber strength decreased steadily from 37.2 MPa, to 30.1 MPa, and 27.1 MPa. The 2.7 and 3.6 m spacings had a major negative impact on lumber MOE (–15% and –21%), lumber strength (–19% and –27%), and a minor impact on wood density (–2% and –4%). MSR yields of No.2 & Better lumber grades decreased markedly with increased spacings. In the 1.8 m stand, 69.2 % of the lumber volume was graded MSR 1650f-1.5E, in comparison to 46.2% and 15% in the 2.7 m and 3.6 m stands, respectively.
In conclusion, this study indicates that initial spacing in white spruce should not exceed 1.8 m from a wood quality perspective, as wider spacings significantly decreased lumber stiffness and strength (MOE and MOR). However, if the silvicultural objective were to maximize economic value regardless of lumber mechanical properties, the 2.7 m spacing would give the highest plantation value.
Le mandat du projet consiste en la réalisation d’essais avec un équipement d’acquisition générique NIR (Near Infrared) dans le but de développer des modèles mathématiques pouvant être utilisés pour déterminer le taux d’humidité des planches de bois franc pour quatre essences : le chêne rouge, l’érable à sucre, le merisier et l’érable argenté.
Une fois les modèles développés les objectifs plus spécifiques sont d’évaluer le niveau de précision de mesure de la teneur en humidité sur du bois parfaitement équilibré ainsi que déterminer les impacts sur les lectures provenant des facteurs suivants : l’essence, la densité, la qualité de surface, la température du bois, le gradient de teneur en humidité ainsi que la vitesse de passage des planches. Finalement, des essais doivent être réalisés sur du bois provenant directement de l’industrie et n’ayant subi aucun traitement d’équilibrage en laboratoire pour connaître le niveau de précision de lecture dans ces conditions.
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.