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Umeå, Sweden

Geladi P.,Swedish University of Agricultural Sciences | Eriksson D.,Stanford University | Ulvcrona T.,SCA Skog AB
Wood Science and Technology | Year: 2014

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. © 2014 Springer-Verlag Berlin Heidelberg.

Johansson S.,Lund University | Carlqvist K.,Lund University | Kataria R.,Swedish University of Agricultural Sciences | Ulvcrona T.,Swedish University of Agricultural Sciences | And 5 more authors.
Wood Science and Technology | Year: 2015

Use of wood feedstocks for sugar-based biorefineries requires suitable treatments of the various tree fractions to optimize yields. In the current study, stem wood fractions (sapwood, heartwood and knotwood) were sampled at different heights from well-documented Scots pine trees taken from two contrasting stands. The fractions were assessed in terms of chemical composition, response to SO2-catalysed steam pretreatment and enzymatic digestibility. There were significant differences in total extractive contents between the fractions, where the heartwood fractions had an extractive content 1–3 wt% higher than sapwood (corresponding to a relative increase of 20–60 %) for samples at the same height. In contrast, the differences in macromolecular carbohydrate contents between the fractions were smaller and mainly insignificant. One exception was the xylan content, which was higher in heartwood than in sapwood at the same tree height (a relative difference of 10–15 %). Steam pretreatment resulted in a clearly higher degree of hydrolysis for sapwood than for heartwood at the same conditions. However, at optimal pretreatment temperatures a higher total sugar yield was in fact obtained for heartwood, showing the importance of tuning the process conditions for the respective wood fractions. © 2015, Springer-Verlag Berlin Heidelberg.

Fries A.,Swedish University of Agricultural Sciences | Ulvcrona T.,SCA Skog AB | Wu H.X.,Swedish University of Agricultural Sciences | Kroon J.,Skogforsk
Scandinavian Journal of Forest Research | Year: 2014

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. © 2014, © 2014 Taylor & Francis.

Ulvcrona K.A.,Swedish University of Agricultural Sciences | Karlsson K.,Swedish University of Agricultural Sciences | Ulvcrona T.,SCA Skog AB
Scandinavian Journal of Forest Research | Year: 2014

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. © 2014 © 2014 Taylor & Francis.

Hallsby G.,Swedish University of Agricultural Sciences | Ulvcrona K.A.,Swedish University of Agricultural Sciences | Karlsson A.,Swedish University of Agricultural Sciences | Elfving B.,Swedish University of Agricultural Sciences | And 3 more authors.
Forestry | Year: 2015

The general belief that intense regeneration measures are financially viable and essential for high sustained yields of commercial forest products has been inadequately tested. This field experiment evaluates effects of three different regeneration intensities 24-27 years after clear-cutting of 14 sites across Sweden. The treatments, designated high (HI), normal (NI) and low (LI), respectively, consisted of: mechanical site preparation and planting of large seedlings at 2×2 m spacing, with supplemental planting and pre-commercial thinning (PCT) when deemed necessary; standard local practices; and natural regeneration with no site preparation, artificial regeneration or PCT. Average crop seedling densities were highest and lowest (3359 and 1662 ha-1) under the HI and LI treatments, respectively, 4-8 growing seasons after planting. After 24-27 years, HI also resulted in higher mean stem volume (90 m3 ha-1) than LI (36 m3 ha-1) but was not significantly different from NI (65 m3 ha-1) and increasing the regeneration intensitywas not consistently positive. In some cases, high planted seedling mortality and generally abundant natural regeneration resulted in minor (or no) differences between the treatments. The results illustrate that current Swedish regeneration standards may need revision in order to reflect contemporary societal and commercial demands. © Institute of Chartered Foresters, 2015. All rights reserved.

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