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Wood from Norway spruce (Picea abies L. Karst.) is biologicallydegraded in exposed conditions. It also has anatomical featuresthat make it difficult to impregnate with preservatives by currentlyavailable industrial processes. In the study reported here,we used the new Linotech process to impregnate Norway sprucewood with hydrophobic linseed oil and then quantified its uptakeand dispersal in anatomically distinct wood tissues. We alsoinvestigated the effects of the wood moisture content on theresults of the impregnation. Samples (500 x 25 x 25 mm) weretaken from 15 trees in a coniferous forest in northern Sweden(64° 10' N, 160–320 m a.s.l.). The parameters forthe Linotech process were 2–3 h treatment time at 0.8–1.4MPa and 60–140°C. To determine the level of uptake,the linseed oil was extracted from the impregnated wood usingmethyl-tertiary-butyl-ether. The uptake was quantitatively analysedby comparing X-ray microdensitometry values obtained followingimpregnation both before and after oil removal. In earlywood,initial moisture content had an obvious effect on the impregnationresult. Six times more oil was taken up when the moisture contentwas greater than ~150 per cent than when it was less than 30per cent. Theoretical calculations, based on density levels,suggest that the water-filled porosity of the wood (water volumedivided by porosity volume) was positively correlated with thelinseed oil uptake, and more strongly correlated in earlywoodthan in latewood. There were also significant differences inuptake between different wood tissues; heartwood/mature woodand heartwood/juvenile wood showed 10–20 per cent weightincreases due to linseed oil uptake, compared with 30–50per cent in sapwood/mature wood. Examination by scanning electronmicroscopy confirmed these uptake patterns. The moisture contentafter impregnation was about 5 per cent, irrespective of theLinotech process parameters, tissue type and initial moisturecontent. In conclusion, the impregnation process used here resultsin high levels of well-dispersed linseed oil uptake and shouldfacilitate drying. 相似文献
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Kristina A. Ulvcrona Kjell Karlsson Thomas Ulvcrona 《Scandinavian Journal of Forest Research》2014,29(5):427-435
Data from seven Scots pine (Pinus sylvestris L.) stands in central Sweden that had undergone pre-commercial thinning (PCT) were used to investigate the biological effect of PCT on the diameter at breast height (DBH) growth of the remaining trees. Two treatments were considered: a PCT treatment and a control (C) with no PCT. The DBH of the trees in each stand was measured on up to four occasions over 15 years. We examined mean DBH and DBH growth of the largest 300, 600, 900 and 1200 trees ha?1. Two methods of selecting the trees used to calculate the mean DBH values for each measurement occasion were considered: the actual mean DBH (Dma), which is based on the DBH distribution of the trees on the measurement occasion in question, and the genuine mean DBH (Dmg), which is based on the DBH distribution of the trees on the final measurement occasion of the study and therefore focuses on the same set of trees for all measurement occasions. There was no clear difference between the Dma- and Dmg-based DBH increments, but the Dmg values tended to be somewhat larger both for the C and PCT treatments. Over a 15-year period, the relative mean yearly increments (Dma/Dmg) for different tree size classes ranged from 0.91 to 0.98, with lower values for the C treatment and larger DBH size classes. We found that PCT promotes DBH growth: over a 15-year period, the increased growth amounted to about 2.0 mm year?1 compared to the trees in unthinned plots. 相似文献
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Maria Fredriksson Lars Wadsö Peter Johansson Thomas Ulvcrona 《Wood material science & engineering》2016,11(4):189-200
In order to perform service life predictions of rain exposed wood structures, the moisture and temperature conditions in the structure need to be known as well as which degradation that occurs under those exposure conditions. The microclimate (the moisture conditions at the surface) is the boundary condition for moisture transport into the wood and depends on the detail design; joints between two pieces of wood can act as a water trap which give long durations of surface moisture after rain events and hinders drying. This study presents moisture content and microclimate measurements in three types of Norway spruce joints exposed to artificial rain in the laboratory. Both the microclimate (the duration of water on surfaces and in gaps) and the moisture content profiles were monitored. The microclimate was changed by changing the size of the gap between the two boards. The duration of water in the gap depended both on the gap size and on the permeability of the wood (sapwood/heartwood, end grain surface/side grain surface). In many cases, a larger gap width gave shorter durations of high moisture contents since a larger gap gave more favourable drying conditions, but the magnitude of this reduction varied between joint types. 相似文献
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Eight pieces of sapwood and heartwood from Scots pine, before and after linseed oil impregnation, were used to make 16 near-infrared hyperspectral images (90–200 pixels wide × 466–985 pixels long × 239 wavelengths: 982–2,480 nm). The wood pieces were selected according to a 2 × 2 experimental design using radial–tangential cut and heartwood–sapwood as factors with two replicates. A first mosaic of 16 images was cleaned and analyzed by image principal component analysis. Interpretation was realized by studying score images and score plots by brushing interaction. In the resulting T1–T2 score plot, the untreated pieces formed a dense cluster, while the impregnated ones showed larger variation. The good separation of treated and impregnated clusters was confirmed by PLSDA showing low false negatives and positives. Analysis of the eight impregnated wood pieces clearly showed regions of wrong impregnation in one wood piece. Loadings resembling linseed oil spectra indicated that this was due to badly polymerized linseed oil. After removing the outlier piece, a new model was made on the seven-piece mosaic showing in the T1–T2 score plot that heartwood and sapwood absorbed the linseed oil differently. This difference was not detected in the untreated wood, so it had to come from the impregnation process. Edges reacted differently from surfaces to the impregnation process as seen in the T1–T4 score plot. These findings show that a future online quality inspection of both raw wood and impregnated pieces would be feasible. 相似文献
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Anders Fries Thomas Ulvcrona Harry X. Wu Johan Kroon 《Scandinavian Journal of Forest Research》2014,29(8):764-776
Eight clones from a 16-year-old field trial of clonal cuttings of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were analyzed for growth, growth pattern, and stem damage in the field. In addition, wood and fiber traits (acoustic velocity [AcVel] and spiral grain) were analyzed and wood density, microfibril angle, modulus of elasticity, and radial fiber diameter (FibDR) determined from SilviScan analyzes. Two clones with considerably more bent, broken, and leaning stems differed from the other clones in terms of microfibril angle and modulus of elasticity (MOE) in the outermost annual rings. FibDR and, to some extent, MOE in the outermost annual rings were negatively correlated with the frequency of bent, leaning, or broken stems, while microfibril angle (MFA) was positively correlated. AcVel was negatively correlated with both MFA and the frequency of bent, broken, and leaning stems. We conclude that AcVel could be used as an effective tool to predict severe stem damage and determine stem strength in the field instead of using costly lab-based SilviScan measurements of microfibril angle. If developed further, this approach could be used for large-scale screening of progeny tests when selecting for stem strength. 相似文献
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Kristina Ahnlund Ulvcrona Thomas Ulvcrona Urban Nilsson Tomas Lundmark 《Scandinavian Journal of Forest Research》2014,29(3):197-209
The increasing demand for forest biomass for energy generation could be partially met by growing denser stands and use of fertilizer. Before this is done at large scale, more knowledge of the effects of stand density and fertilization on aboveground allocation patterns and stem form is needed. Therefore, effects of pre-commercial thinning (PCT) to 3000 stems ha?1, an unthinned dense control (C), and PCT combined with two levels of fertilization (100 kg ha?1 of nitrogen applied either during the establishment of the field experiment (F1) or annually (F2)) were examined in 23- to 26-year-old Scots pine (Pinus sylvestris L.) stands six years after the establishment of the field experiment. In total, 114 sample trees were harvested using destructive biomass sampling. The growth allocation and stem form of trees with diameter at breast height (DBH; 1.3 m height) >5.0 cm were not affected by either the PCT or fertilization. Small trees (DBH < 5 cm) in denser, unthinned control plots had more slender stems (lower DBH/height ratios) and allocated less growth to branches and foliage than trees in PCT plots. Fertilization had little effect on the stem form and growth allocation of the smallest trees. Therefore, effects of stem density and fertilization on stem form and growth allocation to foliage were only found for small suppressed trees, and the treatments had very little influence on dominant and codominant trees. 相似文献
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Ulvcrona Kristina Ahnlund; Claesson Svante; Sahlen Kenneth; Lundmark Tomas 《Forestry》2007,80(3):323-335
The effects of pre-commercial thinning on tree and branch characteristicswere analysed at two experimental sites in northern Sweden,where pre-thinning of Scots pine stands to 600, 1000 and 1800stems per hectares at heights of 1.5, 3, 5 and 7 m had beencombined in a factorial design. A total of 90 trees were cutand branches were measured in whorls sampled at 1-m intervals,starting with the whorl closest to 0.5 m above ground. Effectsof the treatments on tree and branch characteristics were analysedby a fixed-effect analysis of variance model, which was appliedseparately for each experimental site and whorl height. Diameterat breast height (d.b.h.) and living crown to height ratio decreased,while the height/d.b.h. ratio (stem form) increased with increasingstand density, and generally with increased height at thinning.No treatment effect was found on the number of branches perwhorl or branch angle, but branch diameter (BD) was significantlyinfluenced by both stand density after thinning and height atthinning. BD decreased with increases in stand density and decreasedwith increases in height at pre-commercial thinning. Relativebranch size (RBS), defined as the ratio between the sum of thediameters of branches in a whorl and stem perimeter under barkat the location of that whorl, was significantly influencedonly by stand height at the time of treatment. RBS decreasedby 4–6 per cent in whorls located below the current baseof the living crown with each step increase in stand heightat pre-commercial thinning. The results indicate that the numberof stems after pre-commercial thinning has a greater impacton tree size and shape than timing of pre-commercial thinning.Stand density after thinning also has a greater impact on branchsize, in the sense that it will affect branch size further upthe tree than the timing of pre-commercial thinning. However,by delaying the time for pre-commercial thinning it is possibleto reduce the RBS in the lower part of the stem. This mightbe an important measure to improve timber quality later in therotation period, which cannot be done solely by regulating standdensity. 相似文献
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