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Natural regeneration can reduce costs compared with replanting. However, its use requires knowledge about how either active or passive management will affect the balance between quality and quantity in the timber supply. This study aimed to quantify the effects of respacing on volume recovery and wood properties. Two British forest experiments using Picea sitchensis with various respacing distances and an un-respaced control were assessed 21–22 years after the treatments were applied. Tree dimensions were measured and used to quantify slenderness, merchantable volume, and sawlog volume. Wood properties were assessed on a sub-sample using mechanical testing. Generalised linear mixed models were used to examine differences between treatments and sites. Respacing decreased slenderness and increased relative sawlog volume and branch size. Wider respacing reduced wood strength and the widest respacing reduced wood stiffness. Respacing did not affect wood density. However, at the relatively low productivity sites considered here, respacing to 2.1 m represented the best compromise for current markets. In summary, not respacing improved some wood properties but reduced tree stability and the proportion and volume of sawlogs, which will negatively affect forest value. [ABSTRACT FROM AUTHOR]

We present a new method to estimate individual knot volumes based on a knot geometry model coupled with observations on branch characteristics. X-ray computer tomography and image analysis were used to measure the volume and geometry of 424 knots of Sitka spruce (Picea sitchensis (Bong.) Carriere). Knot geometry can be described mathematically by deriving functions for relative vertical position, diameter, and slope dependent on radial position in the stem. These functions were parameterized using 'seemingly unrelated regression' and mixed-modelling techniques. This provided a base model for typical knots. To estimate individual knot volume, we used available data for branch diameter and insertion angle to obtain conditional predictions. We imputed the most likely knot trajectory, as relative vertical position cannot be measured on branches. The model explained up to 96% of the variability in knot volume by incorporating the branch measurements, in contrast to the 43% explained using the typical knot model. Knot volume assessment based only on conditional predictions of diameter and marginal predictions of vertical position also accounted for 96% of the variability. Therefore, measurements of branch diameter alone would be enough to obtain highly precise predictions of individual knot volume. This estimator is a first step towards a knot model to be used for the management of Sitka spruce in Great Britain. Key words: knot geometry, seemingly unrelated regression, Sitka spruce, mixed models, BLUPs. Nous presentons une nouvelle methode pour estimer le volume de chaque noeud sur la base d'un modele de geometrie des noeuds couple a des informations sur les caracteristiques des branches. La tomographie aux rayons x et l'analyse d'images ont ete utilisees pour mesurer le volume et la geometrie de 424 noeuds chez l'epinette de Sitka (Picea sitchensis (Bong.) Carriere). On peut decrire la geometrie d'un noeud de facon mathematique en derivant des equations pour la position verticale relative, le diametre et la pente qui dependent de la position radiale dans le tronc. Ces equations ont ete parametrees a l'aide de methodes de << seemingly unrelated regression >> et de modelisation a effets mixtes. Cela a fourni un modele de base pour les noeuds typiques. Pour estimer le volume d'un noeud, nous avons utilise les donnees disponibles pour le diametre et l'angle d'insertion des branches afin d'obtenir des predictions conditionnelles. Nous avons impute la trajectoire des noeuds la plus probable etant donne que la position verticale relative ne peut etre mesuree sur les branches. Le modele explique jusqu'a 96 % de la variation du volume des noeuds si on incorpore les mesures des branches contrairement a 43 % pour le modele de noeuds typiques. De plus, l'evaluation du volume des noeuds seulement sur la base de predictions conditionnelles du diametre et de predictions marginales de la position verticale explique aussi 96 % de la variation. La seule mesure du diametre des branches serait par consequent suffisante pour obtenir des predictions tres precises du volume de chaque noeud. Cet estimateur n'est que la premiere etape vers un modele de noeuds utile a des fins d'amenagement de l'epinette de Sitka en Grande-Bretagne. [Traduit par la Redaction] Mots-cles : geometrie des noeuds, regression sans relation apparente, epinette de Sitka, modele a effets mixtes, methode BLUP de Henderson., 1. Introduction The occurrence of knots in the wood of commercial species is a long-standing issue for the sawn-wood industries. Knot frequency and size, often jointly referred to as knot [...]

Information on tree height-growth dynamics is essential for optimizing forest management and wood procurement. Although methods to derive information on height-growth information from multi-temporal laser scanning data already exist, there is no method to derive such information from data acquired at a single point in time. Drone laser scanning data (unmanned aerial vehicles, UAV-LS) allows for the efficient collection of very dense point clouds, creating new opportunities to measure tree and branch architecture. In this study, we examine if it is possible to measure the vertical positions of branch whorls, which correspond to nodes, and thus can in turn be used to trace the height growth of individual trees. We propose a method to measure the vertical positions of whorls based on a single-acquisition of UAV-LS data coupled with deep-learning techniques. First, single-tree point clouds were converted into 2D image projections, and a YOLOv5 (you-only-look-once) convolutional neural network was trained to detect whorls based on a sample of manually annotated images. Second, the trained whorl detector was applied to a set of 39 trees that were destructively sampled after the UAV-LS data acquisition. The detected whorls were then used to estimate tree-, plot- and stand-level height-growth trajectories. The results indicated that 70 per cent (i.e. precision) of the measured whorls were correctly detected and that 63 per cent (i.e. recall) of the detected whorls were true whorls. These results translated into an overall root-mean-squared error and Bias of 8 and −5 cm for the estimated mean annual height increment. The method's performance was consistent throughout the height of the trees and independent of tree size. As a use case, we demonstrate the possibility of developing a height-age curve, such as those that could be used for forecasting site productivity. Overall, this study provides proof of concept for new methods to analyse dense aerial point clouds based on image-based deep-learning techniques and demonstrates the potential for deriving useful analytics for forest management purposes at operationally-relevant spatial-scales. [ABSTRACT FROM AUTHOR]

Compression wood has undesirable properties for structural timber and for paper production. Traditional methods of detecting it are often time consuming and subjective. This study aimed to rapidly and impartially detect compression wood through the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and diffuse reflectance near infrared (NIR) spectroscopy. Compression wood and non-compression wood samples were obtained from young Pinus radiata D. Don trees grown in New Zealand. Longitudinal dimensional changes were measured during drying or water saturation of the samples; lignin and galactose contents were determined using conventional analytical techniques. Chemical composition was here a more reliable discriminator between wood types than longitudinal dimensional changes. It was shown that partial least-squares regression (PLS-R) or discriminatory analysis (PLS-DA) could be used to build models on the training samples that could discriminate between wood types of the independently grown validation samples. Ultimately, both types of spectroscopies could be used to discriminate between compression wood and non-compression wood either through prediction or discriminatory analysis with equal success. Investigation into spectral differences between wood types, including sequential mixtures of wood types, showed that for the mid-IR region absorbance at a well-resolved lignin band could be used to discriminate compression wood from non-compression wood. For NIR, a similar investigation showed that absorbance values at four separate wavenumbers or the 6000-5600 [cm.sup.-1] region of the first derivative spectra were required for that discrimination. It is proposed that if there is a gradual change in the chemical composition of compression wood with its severity, then IR spectroscopy could feasibly be used to rapidly determine compression wood severity. Key words: compression wood, NIR, ATR-FTIR, Pinus radiata, lignin. Certaines proprietes du bois de compression le rendent indesirable pour le bois de charpente et la production de papier. En general, les methodes traditionnelles de detection prennent du temps et sont subjectives. Cette etude vise a detecter rapidement et objectivement le bois de compression au moyen de la spectroscopie infrarouge a transformee de Fourier par reflectance totale attenuee (IRTF-RTA) et de la spectroscopie dans le proche infrarouge (PIR) par reflectance diffuse. Des echantillons de bois de compression et de bois normal ont ete obtenus a partir de tiges de Pinus radiata D. Don croissant en Nouvelle-Zelande. Les variations dimensionnelles dans le sens longitudinal ont ete mesurees durant le sechage ou la saturation en humidite des echantillons; les teneurs en lignine et en galactose ont ete determinees en ayant recours aux techniques analytiques conventionnelles. La composition chimique permettait ici de distinguer de facon plus fiable les types de bois que les variations dimensionnelles dans le sens longitudinal. Il a ete demontre que la regression ou l'analyse discriminante par les moindres carres partiels pouvaient etre utilisees pour construire des modeles en utilisant les echantillons d'entrainement et que ces modeles pouvaient distinguer les differents types de bois des echantillons de validation cultives de facon independante. Ultimement, les deux types de spectroscopie pourraient etre utilises avec autant de succes pour distinguer le bois de compression du bois normal via l'analyse previsionnelle ou discriminante. L'etude des differences spectrales entre les differents types de bois, incluant des melanges sequentiels de types de bois, a montre que l'absorbance dans l'IR moyen d'une bande bien definie correspondant a la lignine pouvait etre utilisee pour distinguer le bois de compression du bois normal. Dans le cas du PIR, une etude similaire a montre que les valeurs d'absorbance a quatre longueurs d'onde differentes, ou la region comprise entre 6000 et 5600 [cm.sup.-1] des spectres en derivee premiere, etaient necessaires pour faire cette distinction. Si la composition chimique du bois de compression evolue graduellement avec la severite, il serait alors possible d'utiliser la spectroscopie IR pour determiner rapidement la severite du bois de compression. [Traduit par la Redaction] Mots-cles : bois de compression, PIR, IRTF-RTA, Pinus radiata, lignine., Introduction Compression wood is formed by gymnosperm (softwood) trees as a reaction to an external environmental stress (or stresses) (e.g., wind, snow, or weight overhang) that forces the stem or [...]

The British forestry sector lacks reliable dynamic growth models for stands of improved Sitka spruce, the most important commercial forest type in Great Britain. The aim of this study is to fill this gap by trialling a new modelling framework and to lay the foundations of a future dynamic growth simulator for that forest type. First, we present single tree diameter and height increment models that are climate sensitive and include explicit competition effects. The predictions from the increment models are pooled to project diameter and height at a given age. These projections are then used as inputs to an integrated taper model from which stochastic tree volume predictions are obtained. Retrospective data from over 1400 trees collected in two extensive genetic trials in Scotland and Wales were used for the purposes of this study. Diameter increment and height increment predictions were highly accurate and diameter and height projections proved consistent. The predicted volume at the time of harvesting also exhibited a high degree of accuracy, which shows the robustness of our approach. Further data will be needed in the future to recalibrate the present models and extend their range of validity to the whole of Great Britain. [ABSTRACT FROM AUTHOR]

In this paper, we present new dynamic top height models for 10 major species in Great Britain. These models for pure, even-aged stands replace the current, static top height-age curves published in the 1980s, which are no longer reliable in the light of the new data that have been added over the past decades. We followed the generalized algebraic difference approach (GADA) to build the new models and specifically focused on models derived from the Hessfeld IV and Chapman–Richards height-age base equations. We selected a multi-asymptote and polymorphic GADA version of the Chapman–Richards equation for all the species, with the anamorphic functional form as a special case derived from the non-significance of one of the global parameters. The new models are dynamic, accurate and robust, which will permit unbiased yield predictions from current top height-dependent yield simulators in Great Britain. [ABSTRACT FROM AUTHOR]

There is little information about the impacts of past Sitka spruce (Picea sitchensis [Bong.] Carr.) tree breeding on wood properties because the emphasis has traditionally been on improving stem form and growth rates. This study used both SilviScan and mechanical testing to investigate the radial variations in wood stiffness, bending strength, density and microfibril angle in defect-free samples taken from the first United Kingdom progeny trial to reach merchantable size. We tested for differences in these radial patterns of variation in half-sibling progeny of three plus trees originally selected for superior growth rate and stem form against a non-selected control. Large differences in all of the propertieswere observed with radial position, with properties generally being less desirable in the corewood. Significant undesirable differences between the improved families and the control were found for stiffness, strength and microfibril angle. There was no significant relationship between wood density and stiffness in samples taken from the inner part of the tree, where stiffness was more closely associated with microfibril angle. Overall, previous selections for growth rate and/or stem form have compromised timber properties. It is recommended that current breeding programmes focus on corewood stiffness to prevent further degradation in the wood properties of the future timber supply. [ABSTRACT FROM AUTHOR]

The potential of pyrolysis followed by gas-chromatography and mass-spectrometry (Py-GC/MS) was investigated for identifying compression wood (CW) in saplings of radiata pine ( Pinus radiata) by examining samples of CW and opposite wood (OW). Phenolic compounds and anhydrosugars were identified among the pyrolysis products that provided information about the cell-wall polymers. Sample preparation, such as coarse-milling, fine-milling, and fine-milling followed by calcium-chloride treatment was also investigated. Fine-milling typically decreased the total yield of phenolic compounds compared with coarse-milling. Fine-milling followed by calcium-chloride washing significantly increased the proportions of pyrolysis products from polysaccharides, specifically from (1→4)-β-D-galactans that were of interest in distinguishing CW from OW. Six pyrolysis products were identified that were unique to the CW samples examined, including derivatives of (1→4)-β-D-galactans and H-units of lignin. Other pyrolysis products were identified that had significantly different proportions between the two wood types, and sometimes among samples of the same wood type. [ABSTRACT FROM AUTHOR]