Exploitation d'images tomographiques RX pour l'analyse de la structure interne des gourmands de chêne. Procédure d'utilisation du plugin "Gourmands" avec ImageJ

Cette note explique le fonctionnement du plugin Gourmand, créé par Frédéric Mothe. Utilisé avec le logiciel ImageJ, il permet d'exploiter des images tomographiques RX de billons de Chênes, pour connaitre la structure interne des gourmands. Il permet ainsi de positionner ces gourmands, mais aussi les branches, bourgeons ou picots du billon de chêne dans le but d'en obtenir une image 3D grâce à un second logiciel, Bil3D

Density mapping of decaying wood using X-ray computed tomography.

Wood biodegradation is a central process at the crossroads of several disciplines. It is not only important for carbon storage in forests, but it is also important for wood conservation, wood protection and wood transformation products. Many methods already exist for studying wood biodegradation; however, they present several drawbacks, being time-consuming or destructive. Moreover, they provide little information regarding the complexity of the degradation process and the heterogeneity of the wood substrate. Based on a kinetic study of the biodegradation of Fagus sylvatica by the white-rot fungus Phanerochaete chrysosporium, we developed an X-ray computed tomography method coupled with an in-house plugin for fast, non-destructive and accurate measurement of the density variations of decaying wood. This method allowed us to examine the spatial heterogeneity of woody decayed material at the millimeter scale, providing information about the fungal pattern of degradation. Thus, X-ray computed tomography is an efficient tool that can be used for measuring the degradation of a variety of wood substrates ranging from small normalized wood blocks to fallen logs in the forest

Vers une compréhension de l'évolution structurale des ex-voto en bois de la Source des Roches de Chamalières

International audienc

Measuring wood density by means of X-ray computer tomography

• 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 (R2 > 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

Tracking rameal traces in sessile oak trunks with X-ray computer tomography: biological bases, preliminary results and perspectives

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