Abstract• Wood density is a characteristic of major interest. Usually, it is used as an indicator of wood quality; however, in the context of global change, it is increasingly used for biomass and carbon storage estimations. X-ray computer tomography is a method which enables quick estimates of wood density after applying a calibration procedure.• A review of the literature is presented in this article. Most of the previous studies have been performed in the 80's or at the beginning of the 90's.• In this study, the relationship between wood density and Hounsfield numbers was investigated using a recent medical scanner. A linear relationship was fitted using a calibration data set which consisted in tropical wood samples representing a large range of densities ranging between 133 and 1319 kg m −3 , and then validated using an independent data set (mainly temperate tree species). The fitted relationships were very strong (R 2 > 0.999), whichever the tested scanner settings, with slight but significant effects of the current voltage and reconstruction filters. The RMSE values computed from the validation data set ranged between 5.4 and 7.7 kg m −3 for densities ranging between 364 and 821 kg m −3 .• In conclusion, this method of calibration enables the use of a medical scanner to obtain maps of wood density, in a fast and non destructive way, and with a very good accuracy. Very interesting perspectives are opened regarding biomass distribution within trees. Mots-clés :densité du bois / tomographie à rayons X / CT / nombres Hounsfield / calibration Résumé -Mesure de la densité du bois par tomographie à rayons X.• La densité du bois est une caractéristique d'intérêt majeur. Généralement, elle est utilisée comme un indicateur de la qualité du bois ; cependant, dans le contexte du changement global, elle est de plus en plus utilisée pour des estimations de biomasse et de stockage de carbone. La tomographie à rayons X est une méthode permettant des estimations rapides de la densité du bois moyennant une procédure de calibration.• Une revue de la littérature sur le sujet est présentée dans cet article. La plupart des études précé-dentes ont été réalisées dans les années 80 ou au début des années 90.• Dans cette étude, la relation entre la densité du bois et les nombres Hounsfield a été étudiée en utilisant un scanner médical récent. Une relation linéaire a été ajustée sur un jeu de données de calibration constitué d'échantillons de bois tropicaux représentant une large gamme de densités allant de 133 à 1319 kg m −3 , et validée sur un jeu de données indépendant (principalement des essences tempérées). Les relations ajustées étaient très fortes (R 2 > 0.999) quels que soient les réglages utilisés pour le scanner, avec des effets légers mais significatifs de la tension d'accélération et des filtres de reconstruction. Les valeurs des RMSE calculées à partir de l'échantillon de validation sont comprises entre 5.4 et 7.7 kg m −3 pour des densités allant de 364 à 821 kg m −3 .• En conclusion, la méthode de calibration proposée...

Branch knots and other traces of lateral axes, known as rameal traces, have generally been disregarded within architectural studies based on external observations and their analysis limited to tedious manual dissection methods. Based on non-destructive methods including X-ray CT scanning (XRCTS) and on the ontogenic knowledge progressively accumulated on Quercus petraea, this paper presents (1) the tracking methodology of all rameal traces with XRCTS and the "Gourmands" plugin, and software created downstream, notably the 3D visualisation software "Bil3D"; (2) preliminary results obtained on two Quercus petraea 50 cm-long logs; and (3) potential applications in the fields of biology and ecology. Of approximately 45 sequences of linked rameal traces (composing rameal sequences) per metre, half were directly connected to the pith as horizontal traces of primary epicormic buds, while the other half were connected to a branch by an oblique knot. Horizontal epicormic knots essentially emerged within the tree from the most intensive thinning treatment and led to additional knots in the clear wood. Secondary epicormic shoots may emerge from branch and epicormic knots, leading to a vertical spread of epicormic sites for the former and to more bud clusters for the latter. Engulfment of lateral axes can be quantified. Assumptions on the origin of between-tree variability are proposed. Our methodology opens the way to an exhaustive description of rameal traces. It is relevant for ontogenic and wood quality assessment at the trunk level. It may also be very useful for characterising the potentiality of reiteration and for repairing shoot damage and vegetative regeneration at the crown, collar and even root system level

No abstract

No abstract