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The increased pressure on timber supply due to a reduced forest land base urges the development of new approaches to fully capture the value of forest products. This paper investigates the effects of knowing the position of knots on lumber volume, value, and grade recoveries in curve sawing of 31 white spruce (Picea glauca (Moench) Voss) and 22 jack pine (Pinus banksiana Lamb.) trees. Internal knot position was evidenced by X-ray computed tomography (CT) imaging, followed by the application of a knot-detection algorithm allowing log reconstruction for use as input in the Optitek sawing simulation software. Comparisons of the three levels of sawing optimization (sweep up, shape optimized, and knot optimized) revealed that considering internal knots before log sawing (e.g., knot optimized) generated 23% more lumber value for jack pine and 15% more for white spruce compared with the traditional sweep-up sawing strategy. In terms of lumber quality, the knot-optimized strategy produced 38% more pieces of grade No. 2 and better in jack pine and 15% more such pieces in white spruce compared with the sweep-up strategy. These results indicate a great potential to increase manufacturing efficiency and profitability by implementing the CT scanning technology, which should aid in developing a strong bioeconomy based on an optimized use of wood. [ABSTRACT FROM AUTHOR]

X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored, they dry to some extent, and this drying affects the density variation in the log and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. This paper investigates the effect of improper heartwood-sapwood border detection, possibly due to partial drying, on knot detection in jack pine ( Pinus banksiana Lamb.) and white spruce ( Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual reference knot measurements, and the results showed that knot detection was affected by detected heartwood shape. It was also shown that logs can be sorted into two groups based on how well the heartwood-sapwood border is detected to separate logs with a high knot detection rate from those with a low detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. This can potentially aid both sawmills and researchers working with log models based on CT. [ABSTRACT FROM AUTHOR]

The qualitative evaluation of harvested raw logs and sawlogs is mainly based on the quantitative and qualitative evaluation of the visible macroscopic features of the wood. Modern methods allow for the analysis of whole logs by means of computed tomography. These devices can analyze the internal qualitative features of wood that are not visible on the external structures of the logs. The aim of this work was to evaluate the detection accuracy of a CT-scanning device intended for scanning logs on the internal qualitative features of wood using model trunks. Two logs of beech and oak with a length of 4 m were selected for the analysis, based on availability. Qualitative features were identified through computed tomography scanning, visually identified on cut sections, and then manually measured in accordance with applicable legislation. Relatively good agreement was demonstrated for the detected features in terms of identifying their location (dimension in millimeters from the end of the log). For this parameter, the average differences were 0.90% on the beech log and only 1.21% on the oak log. Relatively high accuracy was shown via CT detection of qualitative features in the beech section (with average differences in dimensions of only 3.5%). In the case of the oak log, the dimensions of the quality features were significantly overestimated. These results indicate that CT scanning technology may have a problem with some hardwood species. It was primarily developed for coniferous tree species, and software algorithms are, therefore, not yet fully adapted to the precise detection of the dimensions of individual quality features. Despite the detected differences, it was confirmed that the CT technology of scanning harvested wood can have a fundamental impact on optimization procedures in the recovery and processing of wood. Renting a scanning line for a certain capacity of wood volume appears to be a deployment option for forestry operations and smaller wood processing operations. Thus, this technology can become an important factor in improving the economic evaluation of the final production of wood. [ABSTRACT FROM AUTHOR]

Wood quality is an important indicator for modern sawmills. Internal wood characteristics can be derived from their correlations with external appearances. In this study, we developed linear regression models to predict knot size from surface features of Mongolian oak (Quercus mongolica) using data collected from 53 trees. For this, manual measurements and X-ray computed tomography scanning technology was respectively used to obtain internal and external features of 1,297 knots. Our results showed that Mongolian oak knots were generally concentrated in the middle part of oak stems, with fewer knots observed at the top and base. The parameters of knot and scar showed significant correlations (P <0:01), where length and diameter of the corresponding external scar increase with increasing the length and diameter of a knot. The corresponding external scar can be used as an effective indicator to predict the internal value of oak logs. The accuracy of our constructed model is more than 95% when assessed against independent test samples. These models thus can be applied to improve the practical production of oak timber and reduce commercial loss caused by knots. These additional data can improve the estimation of the influence of knots on wood quality and provide a theoretical foundation for investigating the characteristics of hardwood knots. [ABSTRACT FROM AUTHOR]

Branches are not only of vital importance to tree physiology and growth but are also one of the most influential features in wood quality. To improve the availability of data throughout the forest-to-industry production, information on internal quality (e.g. knots) of both felled and standing trees in the forest would be desirable. This study presents models for predicting the internal knot diameter of Douglas-fir logs based on characteristics measured in the field. The data were composed of 87 trees (aged from 32 to 78 years), collected from six trial sites in southwest Germany, and cut into 4–5 m logs on-site. The internal knot diameter was obtained by applying a knot detection algorithm to the CT images of the logs. Applying the Random Forest (RF) technique, two models were developed: (1) MBD: to predict the branch diameter (BD) at different radial positions within the stem, and (2) MBDmax: to predict the maximum internal branch diameter (BDmax). Both models presented a good performance, predicting BD with an RMSE of 4.26 mm (R2 = 0.84) and BDmax with an RMSE of 5.65 mm (R2 = 0.78). In this context, the innovative combination of CT technology and RF modelling technique showed promising potential to be used in future investigations, as it provided a good performance while being flexible in terms of input data structure and also allowing the inclusion of otherwise underexplored databases. This study showed a possibility to predict the internal diameter of branches from field measurements, introducing an advance towards connecting forest and sawmill. [ABSTRACT FROM AUTHOR]

Branches are as essential for tree growth as knots are detrimental from the wood quality point of view. To bridge the gap between tree growth and the quality toward end-use, this study aims to establish a relationship between internal and external diameters of Douglas-fir whorl branches. The data comprised 102 trees of a wide age range (30–80 years old) from nine study sites in Southwest Germany. External branch measurements were performed in the field following an established protocol. Logs were scanned on a MiCROTEC CT.LOG, and knots were detected by applying an automated algorithm. Obvious detection artefacts by the CT algorithm were excluded to reveal the relationship between inner-outer branch diameters as clear as possible. Results showed a significant mean difference of 13.8 (± 10.0) mm between the methods (external diameter being larger), with a model indicating an offset of 9.75 mm and angular shift of 0.53 (RMSE = 7.12 mm; R2 = 0.57) between the methods. Separate calculations of sound and dead datasets did not reveal a statistically significant difference. By linking the internal knot structure to external branch measurements, the findings of this study constitute a first step toward the incorporation of CT data into growth models, providing a meaningful prediction of the maximum internal knot diameter at an early stage in the wood supply chain. [ABSTRACT FROM AUTHOR]

Abstract: Tree growth, as measured via the width of annual rings, is used for environmental impact assessment and climate back-forecasting. This fascinating natural process has been studied at various scales in the stem (from cell and fiber within a growth ring, to ring and entire stem) in one, two, and three dimensions. A new approach is presented to study tree growth in 3D from stem sections, at a scale sufficiently small to allow the delineation of reliable limits for annual rings and large enough to capture directional variation in growth rates. The technology applied is computed tomography scanning, which provides – for one stem section – millions of data (indirect measures of wood density) that can be mapped, together with a companion measure of dispersion and growth ring limits in filigree. Graphical and quantitative analyses are reported for white spruce trees with circular vs non-circular growth. Implications for dendroclimatological research are discussed. [Copyright &y& Elsevier]

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Due to the great year-round demand for forest products, off-road forestry traffic occurs even when the ground is susceptible to soil compaction and rutting. We investigated the impacts of repeated passes with a laden forwarder (34 Mg) on the soil physical properties of two clear-cuts on stony till soils in northern Sweden. Core samples (n = 71) were collected from the top 5 cm of mineral soil in and beside wheel tracks, after six passes with the forwarder. Soil physical properties were quantified using classical soil physical analyses and X-ray tomography. The hydraulic conductivity was 70% lower in the wheel tracks than in the soil beside. The X-ray image analysis indicated that this was due to the smaller total volume and lower connectivity of structural pores (φ > 60 µm). Total porosity was 24% and 12% lower in the tracks at the two sites respectively, and mean bulk density was 1.39 g cm−3in the tracks, compared to 1.13 g cm−3beside them. To conclude, traffic changed the soil physical properties in a way that may lead to longer periods of high water content in the wheel tracks, increased risk of surface runoff and insufficient aeration for optimal seedling growth. [ABSTRACT FROM AUTHOR]

Two wood plastic composite (WPC) boards, one experimental and one commercial, were exposed to exterior conditions and evaluated non-destructively using a clinical magnetic resonance imaging (MRI) unit for moisture content (MC) and distribution. The experimental board was exposed in Vancouver, British Columbia, for more than 8 years, and the commercial board was exposed near Hilo, Hawaii, for 2 years. Both boards were characterized in terms of wood content, density, water uptake properties and voids content. The experimental board was additionally destructively analysed for water absorption of the WPC and MC calculated based on the wood content for verification of MRI results. MRI detected the presence of free water and its distribution in both of the WPC boards. Fibre saturation in the experimental board was found to be about 22–24%, in comparison to 25–30% present in most wood species. There was good correlation between the detection of free water by MRI and by destructive testing. Magnetic resonance images showed various major points of water entry in the WPC boards such as the support area, the cut ends, the dripping edge and the sides of the boards. For the experimental board, significant water entry also occurred at the upper exposed surface. [ABSTRACT FROM PUBLISHER]

Research Highlights: Stand density was connected with wood quality and lumber production to develop a predictive model to better estimate tree value. Background and Objectives: The available standing wood volume in British Columbia (BC), Canada has consistently decreased since 1990. Better understanding the link between stand growth conditions, knot characteristics, the sawmilling process and product quality is essential in making informed forest management decisions and efficiently utilizing wood. The overall objective was to investigate and predict the impact of tree growth as affected by stand density on knot characteristics, lumber volume and value recoveries for two conifer species, two types of sawmills and three economic scenarios. Materials and Methods: Seventy-two amabilis fir and western hemlock trees were harvested from three stands located on Vancouver Island, BC. Sawlogs were scanned using an X-ray computed tomography (CT) scanner and images were processed to extract knot characteristics and reconstruct three-dimensional (3D) log models. The effects of three diameter at breast height (DBH) classes (30, 40 and 50 cm) and three stand densities on knot characteristics, including knot volume, number of knots, average knot area and knot/tree volume ratio, as well as the simulated lumber volume and value recoveries from two types of sawmills (i.e., Coastal and Interior) under three economic scenarios (i.e., baseline, optimistic, and pessimistic) were investigated. Results: As expected, the knot characteristics of both species increased with the DBH. The difference of knot distribution between amabilis fir and western hemlock suggests that the latter is more sensitive to growth site conditions. The sawmilling simulations revealed that the Coastal mill produced a lower lumber volume due to the type of products manufactured and the primary breakdown patterns being used. Conclusions: The developed linear mixed effects models based on the knot characteristics and tree features could predict the value of a standing tree and can be used for estimating preharvest stand value of similar Coastal Hem-Fir forests. [ABSTRACT FROM AUTHOR]

Key message: A fully automated algorithm allowed knot detection and positioning on computed tomography (CT) images of Douglas-fir logs. The detection of knot diameter and status could benefit from further improvements, i.e., testing other configurations and implementing texture measures. Manual measurement on CT images allows for tridimensional assessment and greater attainable sampling, while manual measurement on discs provides additional color and texture information. Context: Computed tomography (CT) is a very successful tool to non-destructively acquire the internal knot structure of a log. To enable large-scale applications, an algorithm that automatically detects knots is required. The accuracy of such algorithms depends heavily on the species and image resolution. Aim: This study validates a knot detection algorithm (Johansson et al. in Comput Electron Agric 96:238–45, 2013) on fresh Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) logs. Methods: In this study, 282 knots were sampled from 15 logs, selected from six 78-year-old trees in southwest Germany. The validation of the algorithm's knot detection was performed via comparison against two manual methods: on physical samples and on CT images. Results: The saturated sapwood negatively influences the overall knot detection, which causes underestimation of knot diameter in this area or incomplete detection. The algorithm tended to overestimate knot diameter, longitudinal position, and knot length. Conclusion: The algorithm provides the knot position with satisfactory accuracy. Other settings on contrast and considered volume around a knot can be tested within the algorithm, as well as new development and implementation of texture measures in the image analysis to improve the accuracy results for Douglas-fir in future investigations. [ABSTRACT FROM AUTHOR]