Larch Heartwood Research Articles

Fate of organic solvent-soluble extractives and arabinogalactan during brown rot degradation of siberian larch heartwood

Fate of organic solvent-soluble extractives and arabinogalactan during brown rot degradation of siberian larch heartwood

STEPWISE EXTRACTION OF HEMICELLULOSES WITH WATER AND ALKALI FROM LARCH WOOD AND THEIR SUGAR COMPOSITIONS

The aim of the present study was to isolate hemicelluloses by stepwise extraction with water and alkali from larch (Larix principis-rupprechtiiMayr) sapwood and heartwood. Onewater-soluble arabinogalactan (AG) and three alkali-soluble hemicelluloses-arabinoglucuronoxylan (AGX), galactoglucomannan (GGM) and glucomannan (GM) were obtained. The yield of AG extracted with hot-water from larch heartwood was 7.57%, it was 17.96% in total of three alkali-extracted hemicelluloses. There was no significant difference in the yield of hemicelluloses from sapwood and heartwood. Monosaccharide compositions of thehemicelluloses were determined by high performance liquid chromatography after acid hydrolysis. The results showed that galactose and mannose were the main glycosyl units of hemicellulose, followed by xylose. Galactose mainly derived from AG, whereas mannose and xylose originated from alkali-extracted hemicelluloses.

Using microwave irradiation to increase permeability of Siberian larch wood

The paper presents the research results of the microwave radiation effect on the Siberian larch heartwood. The collected experimental data show that microwave treatment increases the larch wood permeability not only longitudinal but also transversely the fibres. The most significant increase of the transversely fibre wood permeability is found in the tangential direction.

Colorful and facile in situ nanosilver coating on sisal/cotton interwoven fabrics mediated from European larch heartwood

This study reports on a novel coloration approach for sisal/cotton interwoven fabric via in situ synthesis of European larch (Larix decidua) heartwood-anchored sustainable nanosilver. The heartwood extracts functioned as the reducing and stabilizing agent in reaction systems. The deposited silver nanoparticles (AgNPs) over the fabric surfaces displayed brilliant coloration effects with improved fastness ratings and color strengths (K/S). The successful depositions of nanosilvers were quantified and increasing trends in K/S values with the increase in silver precursor loading were discovered. The concentrations of AgNPs deposited on fabric surfaces were found to be 16 mg/L, 323 mg/L, and 697 mg/L, which were measured through an iCP OES (atomic absorption spectroscopy) test. The K/S values obtained for different loadings of silver precursors (0.5, 1.5, and 2.5 mM (w/v)) are 2.74, 6.76, and 8.96. Morphological studies of the control and AgNP-treated fabrics also displayed a uniform and homogeneous distribution of AgNPs over the fabric surfaces. FTIR (Fourier transform infrared spectroscopy) studies of the sustainably developed materials further confirms the successful bonding between the fabrics and AgNPs. Furthermore, stability against temperature was also noticed as per TGA (thermogravimetric analysis) and DTG (derivative TG) analysis although there was a slight decline from the control sisal/cotton interwoven fabrics observed. Statistically, regression analysis and ANOVA tests were conducted to understand the significance of increased nanosilver loading on sisal/cotton interwoven fabrics. In summary, the perceived results demonstrated successful coloration and functionalization of sisal/cotton interwoven fabrics through green AgNPs, which could indicate a new milestone for industrial production units.

Defensive strategies of Norway spruce and Kurile larch heartwood elucidated on the micron-level

To decarbonize the building sector, the use of durable wood materials must be increased. Inspiration for environmentally benign wood protection systems is sought in durable tree species depositing phenolic extractives in their heartwood. Based on the hypothesis that the micro-distribution of extractives influences durability, we compared the natural impregnation patterns of non-durable, but readily available Norway spruce to more durable Kurile larch by mapping the distribution of heartwood extractives with Confocal Raman Imaging and multivariate data decomposition. Phenolics of both species were associated with hydrophobic oleoresin, likely facilitating diffusion through the tissue. They accumulated preferentially in lignin-rich sub-compartments of the cell wall. Yet, the distribution of extractives was found not to be the same. The middle lamellae contained flavonoids in larch and aromatic waxes in spruce, which was also found in rays and epithelial cells. Spruce-lignans were tentatively identified in all cell types, while larch-flavonoids were not present in resin channels, hinting at a different origin of synthesis. Larch-oleoresin without flavonoids was only found in lumina, indicating that the presence of phenolics in the mixture influences the final destination. Together our findings suggest, that spruce heartwood-defense focuses on water regulation, while the more efficient larch strategy is based on antioxidants.

Influence of weathering on surface roughness of thermally modified wood

Wood is one of the most important building materials. Thermally modified wood is entering the market and replacing wood preservatives and tropical wood species in some applications. Thermally modified wood is exposed to weathering similarly as other wood-based building materials. It has been reported that if thermally modified wood is exposed to weathering, its moisture performance might decrease fairly fast. Moisture performance reflects the material’s ability to remain dry and dry out fast when wet. The aim of this study was to determine whether this phenomenon is associated with crack formation or roughness. Norway spruce, thermally modified spruce, wax-treated thermally modified spruce, and European larch heartwood samples were exposed to artificial accelerated weathering and natural weathering for 9, 18, and 27 months. Samples were subsequently isolated, and their roughness was determined with a confocal laser scanning microscope on axial and longitudinal surfaces at 10× and 50× magnification. After weathering, roughness increased on both axial and longitudinal surfaces. This was evident from the profile 2D measurements (Ra) and surface 3D measurements (Sa). The effect of natural weathering on roughness was higher than artificial accelerated weathering, presumably due to synergistic effects of abiotic and biotic factors. This may be associated with Wenzel’s theory on the influence of roughness on the contact angles of water on the surface; namely, increased roughness will decrease the contact angle on hydrophilic surfaces.

Effect of size and shape of specimens on the mass loss caused by Coniophora puteana in wood durability tests

The experimental basis for testing the biological durability of wood often includes incubation experiments with wood-destroying basidiomycetes. Numerous parameters can affect the mass loss by fungal decay (MLF) in laboratory durability tests and therefore being decisive for the resulting durability classification. Among others, the dimension of the wood specimen and the time of incubation impact on fungal decay. Hence, both parameters were examined within this study using 19 different specimen formats and four different incubation times. Specimens of larch heartwood (Larix decidua Mill.) were incubated with pure cultures of the brown rot fungus Coniophora puteana. Scots pine sapwood (Pinus sylvestris L.) was used as a reference. The wood specimens’ format turned out to significantly affect both mass loss by fungal decay (MLF) and resulting x-values when MLF of larch was compared with that of the reference Scots pine sapwood. Both measures were highest for specimen formats with moderate surface-volume ratios. MLF and x-values depended on specimen size and shape as well as on the time of incubation. Reducing the specimen volume generally led to higher MLF at a given incubation time, but prolonging incubation times led to higher x-values and thus to lower durability expressed as durability classes (DC). In summary, it appeared highly questionable that results of basidiomycete durability tests can be easily compared to each other when specimen format and/or incubation time deviate from the standard conditions.

Bending strength under green condition of Japanese larch heartwood decayed by Porodaedalea chrysoloma

Bending strength under green condition of Japanese larch heartwood decayed by <i>Porodaedalea chrysoloma</i>

DURABILITY OF THE SIBERIAN LARCH HEARTWOOD TIMBER OF DIFFERENT ORIGIN: THE RESULTS OF 11-YEAR GROUND CONTACT TEST IN FINLAND

The study describes a ground contact test on natural durability of the Siberian larch heartwood timber. The test has been conducted in Finland according to the European norm EN 252 since the year 2006. The material is timber imported from natural larch stands in Ust-Ilimsk, Russia, and cultivated larch stand in Punkaharju, Finland. The Finnish stand is growing outside the natural range of distribution of Siberian larch. Untreated Scots pine heartwood and impregnated Scots pine sapwood were used as reference materials. The results after 11 years showed that there was remarkable variation in the durability between the larch heartwood samples. Nevertheless, the most durable timber lots on average were the Siberian larch heartwoods harvested from the Russian native stands and the Finnish cultivated stand. It is predicted that it will take another 10 years or more until the failure of the most durable larch stakes.

Water distribution in wood after short term wetting

Water has a major influence on wood properties, especially dynamic moisture cycles, which affect the wood in outdoor applications. It is thus important to understand the penetration and distribution of water in wood. In this study, rainfall events were simulated to correspond to water immersion periods of 1 h. Specimens were imaged by magnetic resonance imaging (MRI) after 1 h of immersion. These measurements were used to determine the water distribution in the wood and to elucidate changes during the drying of specimens of five wood species: sweet chestnut heartwood (Castanea sativa), European larch heartwood (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris) and Norway spruce (Picea abies). Both gravimetric and MRI analysis showed that after 1 h of immersion, pine sapwood took up the highest amount of water, followed by spruce wood. Considerably lower moisture contents were determined in pine heartwood, chestnut and larch, which correlated with a lower signal intensity. The outer parts of the specimens exhibited similar patterns with all of the specimens. The most variable results were the moisture content time profiles in the middle part of the specimens. Comparison of the MRI measurements and gravimetrically determined moisture contents during drying validated the MRI measurements and confirmed the method to be suitable for giving comprehensive information about the water drying kinetic.

Distribution and penetration of tung oil in wood studied by magnetic resonance microscopy

Water repellents, as environmentally-friendly treatments, are gaining popularity as non-biocidal solutions for wood protection. Drying oils, in addition to waxes and organosilicon compounds, are one of the most important water repellents for wood. Tung oil has so far been proven to be one of the best performing oils for wood protection. However, tung oil, similarly as other oils, does not penetrate deeply into wood, due to its high viscosity. In order to improve the penetration of oil into wood, a vacuum-pressure procedure has to be applied. The species used in this study are important in Central Europe: sweet chestnut heartwood (Castanea sativa), European larch heartwood (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris) and Norway spruce (Picea abies). Oil uptake depends on the applied impregnation method and on the wood species used. Retention of tung oil was higher after an impregnation process than with the immersion procedure. Magnetic resonance imaging (MRI) was applied to elucidate the influence of wood species on oil penetration and distribution in wood after treatment. High spatial resolution MR imaging is highly sensitive to changes of liquids in wood and is therefore also very appropriate for monitoring oil penetration. Furthermore, with a good signal to noise ratio of MR images, the method can also discern among specimens with different patterns of oil distribution, as well as between areas of early-wood and late-wood.

Sensitivity of waterborne coating materials to high acidity and high content of arabinogalactan in larch heartwood

Abstract Larch wood is known to be a challenging substrate for waterborne coatings on windows or claddings in exterior applications. In earlier studies the surface properties of larch heartwood were characterised with low pH-values and high content of arabinogalactan. A systematic variation of formulations with different combinations of binders and thickening additives was investigated regarding the sensitivity of the coating materials to high acidity and arabinogalactan. Panels of spruce wood were treated with low-pH buffer solutions and arabinogalactan solutions and after drying the coating materials were applied by spraying. Acetic acid and arabinogalactan solutions were added stepwise to wet samples of coating materials while pH-values and viscosity were measured. Different buffer capacities, changes in viscosity and qualities of film formation were observed depending on coating formulation. The selection of binder and thickening additives enables the formulation of coating materials with lower sensitivity to specific surface properties of larch wood and thus higher quality.

Perspectives for genetic improvement in heartwood size and extractive content in relation to natural durability and aesthetics in interspecific hybrid larch (Larix × eurolepis)

Larch heartwood is the only valuable part of timber when natural durability and aesthetics are requested for end-use products. Therefore, improvement in both quantitative and qualitative properties of heartwood will benefit industry. Genetic variation of heartwood size, extractive content in relation to decay resistance and of colour was studied in 40 full-sib progenies of hybrid larch (Larix × eurolepis) at age 21. Expected genetic gains from various selection scenarios were then investigated. Among all traits studied, extractive contents (total phenols, taxifolin and DHK) showed the highest variability both at the individual (e.g. for taxifolin 3–42 mg g−1 DW) and mean family (e.g. for taxifolin 10–21 mg g−1 DW) levels with heritabilities over 0.66. In contrast, CIELAB colour parameters together with ring density were the least variable, but their heritabilities were close to those of the extractives. Heartwood diameter showed a FS-family mean heritability close to that of radial growth (0.68). European larch (female parent) seemed to play a major role in the genetic control of extractives content, colour and density in the hybrid, while Japanese larch (male) contributed most to the variability for radial growth and heartwood size. Direct selection for heartwood extractive content and heartwood size looked promising with expected gains over 24 and 14 %, respectively (i = 2.043), but it was much less efficient for colour parameters (6 % at most) whatever the selection methods tested. Our study showed that it is still possible to jointly improve radial growth, heartwood size and its extractive content with some success (gains around 10 %) without costly chemical analysis.

Comparison of the antibacterial effects of sapwood and heartwood of the larch tree focusing on the use in hygiene sensitive areas

The aim of this study was to investigate the antibacterial effect of larch wood using microbiological methods. The bacterial strains used for conducting the experiments were Klebsiella pneumoniae (K. pneumoniae) and methicillin-resistant Staphylococcus aureus (MRSA). Wooden cubes as well as wood shavings from larch heartwood and larch sapwood were used as test materials for the analysis. The results indicate that the bacterial number of both test strains decreases significantly after the incubation periods. However, different reduction rates in bacterial count on the sample groups could be observed.

Natural durability of selected larch and Scots pine heartwoods in laboratory and field tests

The aim of this study was to compare natural durability of Siberian larch heartwood grown in Siberia and Sweden as well as European larch and Scots pine heartwood grown in Sweden. The study was based on standard in- and above ground tests lasting 12 years but laboratory decay tests with white and brown rot fungi was also included. Field test results showed that Siberian larch heartwood from Siberia was the most durable among the studied heartwoods with a decay index of 60 after 12 years in Simlångsdalen (Sweden), while European larch heartwood grown in Sweden, was decayed to failure before the end of the test. Scots pine heartwood was found to perform similarly to Siberian larch from Siberia. No relationship could be established between natural durability of examined heartwoods and their water absorption behavior; however, strong correlation to the total amount of extractives was observed. Scots pine and Siberian larch heartwood from Siberia had 12.7 and 19.6% total extractives content respectively but the extractives composition differs. The study revealed also that lignin and monosaccharide content could not explain the variations in decay resistance of the studied heartwoods. No similarities in the natural durability revealed by laboratory and field tests were observed.

The Echo (Jeka) Pavilion in Forest-Park Maksimir Zagreb - Restoration and Health Monitoring

The wooden pavilion Jeka (Echo) was built in 1843 according to the plans of the Austrian Empire garden architect Franz Schücht. Echo pavilion is the only remaining one of ten similar pavilions that were placed in the Forest-park Maksimir during the 19th century. Since 1964 the Echo pavilion has been protected by law and declared as cultural monument of garden architecture together with the whole park Maksimir, in which it is situated. Although the pavilion was restored several times (last time in 1986) it was in very bad condition. The reconstruction and preservation of the complete pavilions wooden construction were done after a careful analysis of its recent state in 2000. Restoration of the “Echo” Pavilion was started because its construction was in poor condition and because the whole pavilion was unsafe. There was a severe decay of the lower parts of the poles, particularly those faced to the North. New poles or only the new parts of the poles were made of glued spruce core surrounded by larch heartwood. Organic solvent Tebuconazole and WOODCAP products were used in wood preservation. The restoration of the Pavilion can be seen as an attempt to extend the life time of a severely damaged cultural monument, or at least in those parts of the monument where the amendments were possible. During reconstruction a monitoring system for wood moisture content at three different positions inside the roof construction was installed. Twice a year the pavilion is being carefully visually inspected and data from data logger downloaded and correctness of the equipment verified.This example of the “Echo” Pavilion is showing that moisture monitoring systems can considerably contribute to prevent cultural heritage from decay. The installed inexpensive and simple monitoring system of early warning proved to be feasible and saved costs in the conservation of wooden cultural heritage. In times of tight budgets and increasing rates of decay moisture monitoring systems will become increasingly important.

Influence of Norway Spruce and European Larch Heartwood Ring-Width on Extractive Content and Durability

Norway spruce and European larch wood are among the most important species for construction applications in central Europe. In order to assess the infl uence of the ring-widths and presence of the extractives on the performance of these wood species against wood decays fungi, Soxlet extracted and non-extracted spruce and larch wood specimens with different ring-widths were exposed to three brown rot fungi according to the EN 113 procedure. In parallel spruce and larch wood specimens were exposed in fi eld test sites in use class 3 conditions according to the double layer procedure. The results showed that ring-widths do not infl uence the performance of the spruce and larch heartwood against brown rot fungi in laboratory conditions, but on the other hand have infl uence on the performance of spruce wood in fi eld test setup. Additionally, extraction does not have an infl uence on the durability of spruce wood, but has an infl uence on the durability of larch wood.

Distribution of heartwood extractives in hybrid larches and in their related European and Japanese larch parents: relationship with wood colour parameters

Heartwood is the most valuable part of larch timber when either natural durability or aesthetic aspects of the wood are required. Both properties are directly linked to chemical extractives and particularly to phenols. Based on a broad sample of trees (583) from European and Japanese larch and their interspecific hybrid, we investigated the variability in phenolic content, and particularly of two major compounds, Taxifolin (Tax) and Dihydrokaempferol (DHK), and their link with wood colour. At the individual wood sample level, phenolic contents ranged from 6.0 to 55.9 mg eq. Tax/g DW. Taxifolin was the most abundant constituent (range: 1.3–41.7 mg/g DW) compared with DHK (0.5–13.7 mg eq. Tax/g DW). A high variability among taxa, genotypes and individual trees within taxa and within trees was observed. Japanese larch had the highest amount of total phenols and of Taxifolin and European larch the lowest. For DHK, Japanese larch was the poorest compared with European larch. Hybrid larch had both a high content of Taxifolin and of DHK. Variability for colour parameters was on average weaker than for phenolic content but still large enough to show significant differences between taxa. Correlations between colour parameters and extractives were moderate to weak. At the mean genotype level, a good link (r > 0.51, p 0.54). The broad variability observed in this study at different levels for phenolics offers opportunities for breeders to genetically improve the quality of larch heartwood, in particular in relation to decay resistance.

소나무와 낙엽송 스킨팀버의 ACQ, CUAZ, CuHDO 가압처리를 위한 처리용 목재의 적정 함수율 및 처리목재의 정착 특성 평가

본 연구에서는 소나무와 낙엽송 스킨팀버의 ACQ-2, CUAZ-2, CuHDO-1 가압처리 특성을 평가하기 위해 소나무 변재부와 낙엽송 심재부 시험편을 대상으로 처리용 목재의 함수율이 방부제 처리도에 미치는 영향과 방부제 유효성분인 구리의 처리목재 내 정착 특성을 조사하였다. 본 연구 결과에 의하면 소나무 변재부는 방부제 종류에 관계없이 함수율 30%부터 사용환경 범주 H3용 처리목재의 침윤도와 흡수량 기준을 모두 만족하였다. 완벽한 방부제 침투가 가능한 소나무 변재부에서 깊이에 따른 방부제 흡수량 경사를 조사한 결과, 방부제 종류에 따른 차이가 관찰되었다. CuHDO-1 처리 시험편에서 발생한 경사가 ACQ-2와 CUAZ-2 처리 시험편에서의 경사보다 심했는데, 특히 고함수율(25, 30%) 시험편에서 경사가 저함수율(15, 20%) 시험편에서보다 심함을 알 수 있었다. 그러나 난주입성인 낙엽송 심재부는 처리용 목재의 함수율 조건 및 방부제 종류에 관계없이 처리도 가 매우 불량하였다. 낙엽송 심재부의 처리도 개선을 위해 증기 전처리(<TEX>$121^{\circ}C$</TEX>의 포화수증기 조건에서 12시간 처리)를 실시한 결과, 낙엽송 심재부의 침윤도와 흡수량 모두 사용환경 범주 H3용 처리목재 기준에 부합하게 처리도가 개선됨을 확인할 수 있었다. 소나무 변재부와 낙엽송 심재부 시험편에서 공히 방부제 유효성분인 구리의 정착이 비건조 양생에 비하여 건조 양생에서 빨리 진행되었다. 소나무 변재부는 양생 초기 3~6일, 낙엽송 심재부는 양생 1일 이내에 3주간 정착된 구리 양의 95% 이상이 정착되었다. 양생 3주 후 처리목재 내에 미정착 상태로 남아있는 구리의 양은 ACQ-2, CuHDO-1, CUAZ-2 순으로 많았는데, 이는 처리용 작업액에 존재하는 구리의 양과 비례하였다. This study was conducted to evaluate the pressure treatment characteristics of Japanese red pine and Japanese larch skin timber with ACQ-2, CUAZ-2 and CuHDO-1. The effect of moisture content (MC) on preservative treatability was investigated for Japanese red pine sapwood and Japanese larch heartwood, and fixation characteristics of CCA alternatives was also evaluated. Japanese red pine sapwood, which was dried below 30 percent MC, was fully penetrated with preservatives, and minimum requirement of preservative retention for the hazard class H3 was achieved. Through measuring preservative retention gradient in Japanese red pine sapwood, it was confirmed that the retention gradient of CuHDO-1 was steeper than that of both ACQ-2 and CUAZ-2. In particular, it was intensified at a higher MCs of wood samples (25∼30%). Japanese larch heartwood did not meet the minimum requirement of penetration and retention for the hazard class H3 over the range of pretreatment MCs tested. With presteaming under <TEX>$121^{\circ}C$</TEX> for 12 hours, the treatability of Japanese larch heartwood was enhanced to meet the minimum requirement for the hazard class H3. The fixation rate of copper was much more faster under drying condition compared with nondrying condition; more than 95% of copper were fixed in 3~6 days and 1 day under drying conditions in Japanese red pine sapwood and Japanese larch heartwood, respectively. After 3-week fixation period at ambient temperature, the amount of mobile copper in treated wood sample that remains available for leaching from treated wood was the highest in the wood samples treated with ACQ-2, followed by CuHDO-1 and CUAZ-2. It was proportional to the amount of copper in treating solution.

Surface mould growth on five modified wood substrates coated with three different coating systems when exposed outdoors

Modified wood has potential for above ground use, but surface treatment might be a request in such applications. Three coating systems were applied on furfurylated Scots pine, acetylated Scots pine, heat treated Scots pine, oil heat treated Scots pine, heat treated Norway spruce, and eight reference wood substrates and exposed outdoors to evaluate their ability to resist surface mould. Samples of the surface were taken for fungal identification to examine any relationship between treatment and fungal species. Both water-borne and solvent-borne coatings with various fungicides were included and the test was carried out according to EN 927-3. The degree of mould growth mainly varied with time and type of paint. Of the modified wood substrates furfurylated Scots pine had the lowest degree of mould growth and acetylated pine had the highest after 3.5 years. A brown semi-transparent acrylic paint had the lowest degree of mould growth after year 1, year 2.5 and year 3.5. Larch heartwood, copper-organic preserved pine and pine heartwood performed best as wood substrates. No differential patterns in susceptibility to various fungal species were detected on the surface of the coated wood substrates – Aureobasidium pullulans was the dominating species on all the wood substrates.