Oxalate found in wood cell wall during incipient brown rot degradation

Brown rot fungi are a marvel and an enigma of Nature. They are capable of depolymerizing holocellulose within wood cell walls without significantly ineralizing lignin. The exact details behind this feat remain unknown, but a staggered mechanism has been identified: 1) an initial step characterized by oxidative degradation of the wood cell wall biopolymers and hypothesized to involve transport of Fe3+ chelated by oxalate into the cell wall, and 2) a second degradation step dominated by hydrolytic enzymes, primarily endoglucanase activity. We subjected spruce wood (Picea abies) to Rhodonia placenta and isolated xylem tissue in the initial stage of degradation. Confocal Raman microscopy revealed oxalate accumulation in the secondary cell wall of a tracheid having fungal hyphae within the lumen. This observation is the first in situ verification of oxalate accumulation within the cell wall during the first step of brown rot degradation.publishedVersio

Perspectives on the environmental implications of sustainable hydro-power: comparing countries, problems and approaches

Perspectives on the Environmental Implications of Sustainable Hydropower gathers scientific papers from three of the worlds most important hydropower producers to discuss aspects of sustainable hydropower and the means by which it can be studied and achieved. The papers examine the application and use of new technologies and protocols for studying hydropower, adaptive management and the implications and use of long-term data sets for minimizing hydropower impacts on fish populations. The papers include a cross section of biological and hydrological experts. The implicit among country comparisons highlight a number of common hydropower themes, particularly the need to expand from single species studies to include broader consideration of the ecosystem, the importance of maintaining habitat, trait and species diversity and the need for consistently collected long-term data sets. Hydropower Sustainability Long-term studies Brazil Canada NorwaypublishedVersio

Natural durability of wood in Norway - results after eight years above ground exposure

Some of the most common Norwegian wood species were tested in a Double layer test in South East Norway. After eight years of exposure the highest decay rating (≥3) was found in Scots pine sapwood, Norway spruce, alder, birch and aspen. Two wood types had decay rate ≤1: Scots pine heartwood and cedar. Wood moisture was logged and compared with precipitation during a two month period the second year of exposure. Scots pine sapwood had higher wood moisture content than Norway spruce, and a good correlation was found between precipitation and wood moisture content. When comparing similar materials exposed at three different geographical locations in Southern Norway, the samples exposed in Bergen had higher decay rating than samples exposed at Ås and Oslo.publishedVersio

Changes in microstructure and stiffness of Scots pine (Pinus sylvestrisL) sapwood degraded by Gloeophyllum trabeum and Trametes versicolor – Part II: anisotropic stiffness properties

Fungal decay considerably affects the macroscopic mechanical properties of wood as a result of modifications and degradations in its microscopic structure. While effects on mechanical properties related to the stem direction are fairly well understood, effects on radial and tangential directions (transverse properties) are less well investigated. In the present study, changes of longitudinal elastic moduli and stiffness data in all anatomical directions of Scots pine (Pinus sylvestris) sapwood which was degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks have been investigated. Transverse properties were found to be much more deteriorated than the longitudinal ones. This is because of the degradation of the polymer matrix between the cellulose microfibrils, which has a strong effect on transverse stiffness. Longitudinal stiffness, on the other hand, is mainly governed by cellulose microfibrils, which are more stable agains fungal decay. G. trabeum (more active in earlywood) strongly weakens radial stiffness, whereas T. versicolor (more active in latewood) strongly reduces tangential stiffness. The data in terms of radial and tangential stiffnesses, as well as the corresponding anisotropy ratios, seem to be suitable as durability indicators of wood and even allow conclusions to be made on the degradation mechanisms of fungi

Natural durability of wood in Norway - results after eight years above ground exposure

Some of the most common Norwegian wood species were tested in a Double layer test in South East Norway. After eight years of exposure the highest decay rating (≥3) was found in Scots pine sapwood, Norway spruce, alder, birch and aspen. Two wood types had decay rate ≤1: Scots pine heartwood and cedar. Wood moisture was logged and compared with precipitation during a two month period the second year of exposure. Scots pine sapwood had higher wood moisture content than Norway spruce, and a good correlation was found between precipitation and wood moisture content. When comparing similar materials exposed at three different geographical locations in Southern Norway, the samples exposed in Bergen had higher decay rating than samples exposed at Ås and Oslo

Cell wall changes during brown rot degradation of furfurylated and acetylated wood

This study explores cell wall changes in Radiata pine (Pinus radiata) after modification with acetylation or furfurylation and subsequent prolonged subjection to the brown rot fungus R. placenta with the aim of better understanding the modus operandi of these two modifications. Both modifications have shown good durability in field tests, but in order to learn from their possible limitations, we used optimal environmental conditions for fungal growth, and extended the testing period compared to standard tests. Hyphae were found in acetylated wood after two weeks, and after 28 weeks of decay abundant amounts of encapsulated hyphae were present. In furfurylated wood, mass loss and a few hyphae were seen initially, but no further development was seen during weeks 18–42. The general degradation pattern was qualitatively the same for unmodified, acetylated and furfurylated wood: carbohydrates decreased relative to lignin. Acetyl groups were lost from acetylated wood during decay (earlier results), while the furan polymer did not seem to be altered by the fungus. Based on these findings it is hypothesized that modifications such as furfurylation that enhance moisture exclusion within the cell wall through impregnation polymerization offer better long term protection compared to modifications such as acetylation that depend on the replacement of hydroxyl groups with ether bound adducts that can be removed by fungi.acceptedVersio