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BACKGROUND The solubilisation of hardwood glucuronoxylan using hot, compressed water is an environmentally friendly technology for biorefineries. Upon processing, most cellulose and lignin remain in the solid phase and can be further separated, enabling the integral benefit of the feedstock. RESULTS The combined effects of time and temperature on the aqueous, non-isothermal processing of Betula alba wood have been assessed in selected experiments. Operating at temperatures within the range 190-230 °C, sugars and higher saccharides derived from glucuronoxylan were the major reaction products, whereas cellulose and lignin were scarcely affected. Refining treatments by membranes and ion-exchange resulted in mixtures of partially acetylated, acidic oligo- and polysaccharides made up of xylose. CONCLUSION The processing scheme proposed in this work enabled the production of separate streams containing substituted hemicellulosic saccharides with different average polymerisation degrees, which show potential as co-products for biorefineries. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Aims Analyse the controversial relationship existing between wood density, precipitation, temperature and aridity, and its importance in shaping forest communities facing drought. Location New Caledonia (SW Pacific). Methods We sampled wood density in 1580 trees belonging to 175 species across nine sites (eight 1-ha plots) located in dry, mesic and humid forests. We tested whether wood density varied across species, communities and habitats, and depended on mean annual precipitation (MAP), mean annual temperature (MAT) and an aridity index (AI). We also tested whether the variations observed in community mean wood density (WDmean) and in wood density standard deviation differed from those obtained by a randomized species distribution across communities. We constructed a phylogenetic supertree at genus level and tested for the non-random distribution of WDmean. Results We found that WDmean tended to increase with increasing aridity (i.e. decreasing MAP and increasing MAT) and was significantly higher than expected under randomized species distribution at the dry forest site only. However, some species with low wood density grew well at these dry sites. At genus level, wood density was not random within the phylogenetic supertree. Some lineages exhibiting higher wood density than expected by randomization were also the most represented at the dry sites. Conclusions Although we did not observe an environmental filter sensu stricto, aridity associated with a low MAP and a high MAT at the dry and mesic forest sites was likely to favour species with a high wood density. Our phylogenetic results suggested that species belonging to a few lineages exhibiting high wood density were likely to be adapted to drought, hence favoured by increasing drought. [ABSTRACT FROM AUTHOR]

Le traitement thermique superficiel du bois permet de rehausser ses propriétés hydrophobe, antifongique et anti-gonflement contribuant à le mettre à l'abri des aléas naturels. Nous avons étudié la pertinence d'un traitement solvothermique d'éprouvettes de bois d'épinette noire imprégnées de liquides ioniques hydrophile ([EMIM][OTf]) et hydrophobe ([HMIM][TF2N]) comparativement à un traitement thermique simple sous balayage à l'azote. Les éprouvettes ont été soumises à des tests d'adsorption d'humidité, d'absorption d'eau, de gonflement, et de propriétés mécaniques après des traitements réalisés dans les gammes de température et de temps suivantes: [180 °C-260 °C] et [30 min-4 h]. Les tests ont montré une diminution notable de la teneur ultime en humidité et de prise d'eau liquide lorsque les échantillons de bois sont préalablement imprégnés de liquide ionique hydrophobe et que la température de traitement reste inférieure à 200 °C. Cependant, les tests de propriétés mécaniques ont montré que les modules d'élasticité et de rupture des éprouvettes affichaient une tendance à la baisse avec l'augmentation de la température et du temps de traitement. L'imprégnation de liquide ionique ne changeait rien à ce comportement même si en général une fragilisation accrue des éprouvettes pouvait être notée à cause de la solubilisation partielle des principaux composants de bois. Surface heat treatment of wood improves its hydrophobic, antifungal, and anti-swelling properties, and strengthens its resistance to the vagaries of natural exposure. We investigated the relevance of a superficial solvothermal treatment of wood specimens impregnated with hydrophilic ([EMIM][OTf]) and hydrophobic ([EMIM][OTf]) ionic liquids which we compared to a conventional heat treatment under nitrogen atmosphere over the following treatment temperature and time ranges: [180 °C - 260 °C] and [30 min - 4 h]. The treated specimens were subjected to moisture adsorption, water absorption, swelling, and mechanical properties testing. The results revealed a notable decrease in ultimate moisture content and water uptake of the samples, provided they were impregnated with a hydrophobic ionic liquid before heat treatment at temperatures less than 200 °C. However, the mechanical properties testing showed that the elastic and rupture moduli of specimens decreased with increasing treatment temperature and time irrespective of using ionic liquids. However, the impregnated samples suffered in general increased breakability which was ascribed to partial solubilization of wood components in the ionic liquid. [ABSTRACT FROM AUTHOR]

ABSTRACT Many wooden objects from cultural heritage consist in wooden panels, painted on one face. Some of these panels show permanent cupping, micro-cracks of the painted layer, and cracks of the painted support itself. Different physical and mechanical phenomena are at the origin of these damages: wood is a hygroscopic material (its dimensions vary with humidity), it is highly anisotropic, the paint layer on one face has properties of permeability different from those of raw wood of the back face, and a rigid frame possibly restrained the deformation of the panel. Experimentations on our mock-up panels combined with numerical simulations of these panels in real situations of hygrothermal fluctuations will allow us to test specific situations and eventually to make suggestions to conservators and restorers and guide them in their interventions. Hygrothermal treatments are often used to improve wood durability thanks a reduction of its hygroscopicity. They have been considered as means to reproduce the physical properties of ancient wood. We intend to model the mechanisms involved in mechanical and chemical effects of wooden painted panels exposed to climatic variations. To develop such conservation tool, we need to work on mock-up, which replicate panel painting. So we will investigate the process of hygroscopic ageing and compression set generation of the back of painted panels to explain their permanent cupping and replicate their ageing state. For this purpose, digital image correlation is used to evaluate the strain field of the section of a wood piece submitted to variations of relative humidity. [ABSTRACT FROM AUTHOR]

Estimates of past climate and future forest biomass dynamics are constrained by uncertainties in the relationships between growth and climatic variability and uncertainties in the instrumental data themselves. Of particular interest in this regard is the boreal-forest zone, where radial growth has historically been closely connected with temperature variability, but various lines of evidence have indicated a decoupling since about the 1960s. We here address this growth-vs.-temperature divergence by analyzing tree-ring width and density data from across Siberia, and comparing 20th century proxy trends with those derived from instrumental stations. We test the influence of approaches considered in the recent literature on the divergence phenomenon (DP), including effects of tree-ring standardization and calibration period, and explore instrumental uncertainties by employing both adjusted and nonadjusted temperature data to assess growth-climate agreement. Results indicate that common methodological and data usage decisions alter 20th century growth and temperature trends in a way that can easily explain the post-1960 DP. We show that (i) Siberian station temperature adjustments were up to 1.3 °C for decadal means before 1940, (ii) tree-ring detrending effects in the order of 0.6–0.8 °C, and (iii) calibration uncertainties up to about 0.4 °C over the past 110 years. Despite these large uncertainties, instrumental and tree growth estimates for the entire 20th century warming interval match each other, to a degree previously not recognized, when care is taken to preserve long-term trends in the tree-ring data. We further show that careful examination of early temperature data and calibration of proxy timeseries over the full period of overlap with instrumental data are both necessary to properly estimate 20th century long-term changes and to avoid erroneous detection of post-1960 divergence. [ABSTRACT FROM AUTHOR]