Strength properties of black spruce wood under different treatment

Summary The effect of various forms of treatment — chemical, thermal and pressure — on the tensile properties of wood was investigated. Spruce was impregnated in water, sodium sulfite and/or sodium bicarbonate, and heated at temperatures ranging from 20 to 190 °C. At the end of cooking (190 °C), decompression was applied both slowly and suddenly.A rise in temperature, an increase in heating time, from 4 to 10 min. at 190 °C, as well as fast pressure release influenced the tensile strength. The chemical treatment resulted in lignin sulfonation while carboxylation produced fiber swelling and, consequently, tensile strength decreased.The authors wish to thank the FCAR (Québec), NSERC (Canada) and Stake Tech. Co. for their financial support     

Dissolution and dispersion of spruce wood components into hot water

Summary The dissolution and dispersion of components from Norway spruce (Picea abies) wood were examined in laboratory experiments to determine the factors influencing variations in dissolved and colloidal substances in mechanical pulp suspensions. Finely ground, fresh spruce wood was suspended in water at 90 °C and was agitated intensively for up to 12 h, after which the concentrations of dissolved and dispersed lipophilic extractives, lignans, carbohydrates and lignins were determined. Sapwood and heartwood were studied separately. Effects of pH and added electrolytes on the dissolution and dispersion of wood components were also investigated.Higher amounts of lipophilic extractives, and especially of triglycerides, were dispersed from sapwood than from heartwood. The release of lipophilic extractives continued for up to 3 h, after which the concentrations in the suspensions leveled off. At this stage the composition of the dissolved and dispersed lipophilic extractives equaled that of the wood. The amount of lipophilic extractives in the suspensions increased with increased pH, in the range of 4.5–6.7, but was lower in the presence of electrolytes. The dissolution of carbohydrates continued even beyond 3 h of agitation. The high water temperature induced hydrolytic reactions, thereby releasing especially arabinose. The release of arabinose through the hydrolytic cleavage from polysaccharides was more extensive at pH 4.5 than at pH 5.5 and 6.7. More polysaccharides containing galacturonic acid units (pectins) were dissolved at a higher pH. Much more polysaccharides containing glucose, most probably starch, were present in the sapwood suspensions. The dissolution of lignins also continued throughout the 12 h experiment. The measured UV-absorption, after extraction of lignans, was roughly the same for sapwood and heartwood suspensions. Slightly less lignins were released in the presence of electrolytes. Lignans were released only from heartwood.     

Evaluation of two surfacing methods on black spruce wood in relation to gluing performance

Surface quality and gluing performance of black spruce samples prepared by peripheral straight-edge knife planing and sanding were studied. Four wavelengths (1.5, 1.9, 3.1, and 6.5 mm) and four rake angles (15°, 20°, 25°, and 30°) were tested for peripheral planing. Three feed speeds (4, 10.5, and 17 m/min) and three grit size sandpapers (80, 100, and 120) were studied for sanding. The resulting surfaces were glued with an isocyanate adhesive and tested to evaluate their gluing performance (shear strength and percent wood failure). Results revealed that planing with a rake angle of 20° and wavelengths of up to 3.1 mm produced wood surfaces with adequate glueline shear strength. Sanding with 80-grit sandpaper produced the best glueline shear strength, regardless of feed speed. After accelerated aging, the loss of gluing performance was lower for the sanded samples compared with that of planed samples. In general, sanding process produced better wood surfaces for bonding with the adhesive studied.     

Variation in water relations of black spruce stock types planted in Ontario

Upland, intermediate and lowland sites in northeastern Ontario were planted between May 28 and June 8 with three types of black spruce (Picea mariana (Mill.) BSP) nursery stock: (1) spring-lifted, 1.5 + 1.5 bareroot plants (BR); (2) 24-week-old, winter-sown, container stock (CWS); and (3) spring-sown, overwintered, container stock (CO). At the beginning of the growing season, the BR stock had the lowest xylem pressure potentials (Psi(x)), stomatal conductances (g(wv)), and net photosynthetic (P(n)) rates. By the end of the growing season, the BR stock still had lower g(wv)s than the container stock types, but had higher shoot Psi(x) values. In August, the turgor loss points for the BR, CO and CWS stock types were -2.8, -1.93 and -1.6 MPa, respectively, while the minimum observed shoot Psi(x) values were -1.4, -1.7 and -1.9 MPa, respectively. The BR stock produced the greatest dry weight of new shoots and unsuberized roots. No new shoots were produced by the CWS stock, but they produced a greater dry weight of unsuberized roots than the CO stock. As a percent of the dry weight of suberized roots, the greatest production of unsuberized roots was by the CWS stock, the least by the BR trees.     

Variability of selected wood characteristics in 40 half-sib families of black spruce (Picea mariana)

Summary Based on 15-year-old black spruce (Picea mariana) trees from 40 half-sib families sampled from 9 blocks of a family test in New Brunswick, this study examined intertree and intratree variation in various wood density and ring width characteristics. Of various variance components of the intertree variation, a remarkable variance component due to family was found in wood density characteristics (viz. average wood density, average earlywood density and latewood density of the tree), and these characteristics are thus under strong genetic control (h _i ² ranging from 0.60 to 0.86, and h _f ² from 0.56 to 0.68). It, to a lesser extent, applies to ring width characteristics at the tree level (viz. average ring width, and average earlywood width, latewood width and latewood percent of the tree) that show a lower heritability (h? from 0.18 to 0.28, and h _f ² from 0.22 to 0.36). Both block and block × family interaction contribute little to the total intertree variation encountered in 40 families from 9 blocks, while tree-to-tree variation within the family accounts for most (over 3/4) of the total intertree variation.Compared to the intertree variation (tree-to-tree variation within the family), the intratree variation in various wood characteristics studied is considerably larger in this species. It appears that most intraring wood density characteristics show a relatively smaller intertree variation but a relatively larger intratree variation as compared to ring width characteristics (except latewood width and latewood percent). Latewood width and latewood percent show the smallest intertree variation and the largest intratree variation. Between the two sources of the radial intratree variation, cambial age explains much more variation in most intraring wood density characteristics, while ring width accounts for more variation in earlywood width, latewood width and intraring density variation. This indicates that wood density of growth rings in this species is dependent more on cambial age than ring width (growth rate). Among various wood density and ring width characteristics studies, maximum (latewood) density shows the strongest response to calendar year. This characteristics is thus a useful dendroclimatic parameter in this species.I would like to thank Dr. E.K. Morgenstern and Mr. D. Simpson for their involvement in the planning of this study. Thanks are also due to G. Chauret, T. Keenam, R. Ploure, V. Steel and C. Reitlingshoefer for their technical assistance     

Oxidative activation of wood surfaces by flame treatment

Summary The effects of an oxidative activation of some different wood surfaces by flame treatment has been studied. Flame treatment markedly increased the wettability and decreased the microbiological activity. No improvement in glue adhesion was discerned for a water-borne PVAc-glue. ESCA measurements showed a considerable increase in oxidation level as a result of the flame treatment. The duration of the activation varied between different wood species.Appreciation is expressed to Prof. E. Back for valuable discussions and to Mr. G. Carlsson, Institute for Surface Chemistry, Stockholm, for ESCA measurements. Financial support from the Swedish Council for Building Research is kindly acknowledged     

Effect of severe thermal treatment on spruce and beech wood lignins

? The structure, proportion and mode of assembly of lignin, celluloses and hemicelluloses have marked effects on the reaction mechanisms during thermal treatment and therefore have a strong influence on the quality of the final product. The effect of treatment conditions, including severe conditions (up to 553 K) and treatment duration (up to 8 h) on the structure of native spruce and beech lignins was studied.

? Lignin content was determined by the Klason method and lignin structure was evaluated by thioacidolysis.

? The results highlighted the strong reactivity of the native spruce and beech lignins towards severe heat treatments. The distinct susceptibility of syringyl (S) and guaiacyl (G) units towards thermal treatment is confirmed by comparing the data for beech and spruce samples. The most severe treatment of spruce wood (280 °C) induced a dramatic enrichment in lignin content together with the almost complete disappearance of G lignin units, whereas a more moderate treatment substantially changed lignin structure by degradation reactions that affect the p-hydroxyphenyl (H) and G lignin units similarly.

? Thioacidolysis revealed that the thermal treatment induces the appearance of vinyl ether structures in spruce lignins. The decreased yield of the G and S thioacidolysis monomers reflects the progressive disappearance of G and S lignin units only involved in β-O-4 bonds and the formation of condensed linkages in proportions related to treatment severity. In severe conditions, β-O-4 linked S units are more degraded than their G homologues.

     

Identification of selected internal wood characteristics in computed tomography images of black spruce: a comparison study

The feasibility of identifying internal wood characteristics in computed tomography (CT) images of black spruce was investigated using two promising classifiers: the maximum likelihood classifier (MLC) and the back propagation (BP) artificial neural network (ANN) classifier. Nine image features including one spectral feature (gray level values), a distance feature, and seven textural features were employed to develop the classifiers. The selected internal wood characteristics to be identified included heartwood, sapwood, bark, and knots. Twenty cross-sectional CT images of a black spruce log were randomly selected to develop the two classifiers. The results suggest that both classifiers produced high classification accuracy. Compared with the MLC classifier (80.9% overall accuracy), the BP ANN classifier had better classification performance (97.6% overall accuracy). Moreover, statistical analysis reveals that the heartwood of the black spruce log used in this study is the easiest to identify by either classifier compared with the other three log features. The results also suggest that the separability of one wood characteristic from the other wood characteristics in black spruce CT images is mainly related to moisture content.     

Reduction in turgid water volume in jack pine,white spruce and black spruce in response to drought and paclobutrazol

Significant reductions in needle water content were observed in white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill) B.S.P.), and jack pine (Pinus banksiana Lamb.) seedlings in response to a 10-day drought, although turgor was apparently maintained. When the seedlings were re-watered after the drought, jack pine needles regained their original saturated volume, whereas white spruce and black spruce needles did not. Significant drought-induced reductions in turgor-loss volume (i.e., tissue volume at the point of turgor loss) were observed in shoots of all three species, especially jack pine. Repeated exposure to 7 days of drought or treatment with the cytochrome P(450) inhibitor, paclobutrazol ((2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol), reduced seedling height relative to that of untreated controls in all three species. The reductions in saturated and turgor-loss needle volumes in the paclobutrazol-treated seedlings were comparable with those of seedlings subjected to a 10-day drought. The treatment-induced reductions in shoot and needle water contents enabled seedlings to maintain turgor with tissue volumes close to, or below, the turgor-loss volume of untreated seedlings. Paclobutrazol-treated seedlings subsequently survived drought treatments that were lethal to untreated seedlings.     

Improved bondability of wax-treated wood following plasma treatment

In this study, the impact of a plasma treatment using dielectric barrier discharge at atmospheric pressure on wax-treated beech was investigated by surface energy determination and adhesion tests. Measurements of the surface energy revealed a strong increase in surface polarity along with increased surface energy as a result of the plasma treatment, pointing to increased adhesion properties. To evaluate the adhesion properties of a polyvinyl acetate (PVAc) adhesive on beech treated with montan ester wax and synthetic Fischer–Tropsch wax, a special peel test was applied. This peel test provided evidence of increased adhesion of the PVAc after plasma treatment of both materials investigated.     

Proton magnetic resonance techniques for characterization of water in wood: application to white spruce

Summary Two new proton magnetic resonance techniques, relaxation spectra and relaxation selective imaging, have been used to investigate the distribution of water in samples of normal white spruce sapwood, heartwood, and juvenile wood as well as two rehydrated heartwood samples containing incipient decay and compression wood respectively. It is demonstrated that the spin-spin (T₂) relaxation behavior in wood is best presented as a continuous spectrum of relaxation times. Spectra of T₂ for white spruce show separate peaks corresponding to the different water environments. Bound water gives a peak with an T₂ time of about 1 ms and lumen water gives a distribution of T₂ times in the range of 10 to 100 ms. The lumen water T₂ time is a function of the wood cell radius. Consequently, the different cell lumen radii distributions for spruce sapwood, juvenile wood, and compression wood are readily distinguishable by the shape of their T₂ spectra. Water environments which are separable on a T₂ spectrum may be imaged separately. Imaging has been carried out in one dimension for bound water and lumen water of a spruce sapwood sample at four different moisture contents ranging from 100% to 17%. For the first time, we demonstrate that above the fibre saturation point the moisture density profile of the bound water is largely independent of moisture content. The feasibility and utility of using these techniques for internal scanning of logs and lumber is discussed. These techniques should provide new insights into the wood drying process.We would like to thank Michael Weiss of the Biological Science Electron Microscopy Facility at the University of British Columbia for his assistance with the microscopy and image analysis. This research was supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Canadian Forestry Service     

Change in fracturing and colouring of solid spruce and ash wood after thermal modification

Effects of different thermal treatments (maximum treatment temperatures of 200, 210 and 220°C for 2.5 hours) on solid spruce (Picea abies L. Karst.) and ash (Fraxinus excelsior L.) were investigated in this study. The fracture behaviour in radial/longitudinal as well as in tangential/longitudinal and the change of the wood colour (CIEL*a*b* colour space) on all principal anatomical surfaces (cross sectional, radial and tangential) were analysed. The specific fracture energy and the maximum breaking load decreased almost significantly after all thermally treated samples in comparison to the untreated (standard dried) sample. The wood colour changed also significantly, in particular the lightness decreased with increasing intensity of thermal treatment on all investigated surfaces. A comparison of the percentage loss of the different fracture and colour values has shown a strong correlation between the maximum breaking load and the lightness after several thermal treatments, in both investigated crack propagation systems, on all measured surfaces and for both analysed species.     

Sphagnum community change after partial harvest in black spruce boreal forests

In eastern Canada, boreal forests develop structural diversity in association with time since stand replacing fire. In some regions, this is associated with significant changes in the bryophyte community (Sphagnum moss invasion) and paludification (thick waterlogged forest floor development). The bryophyte community responds to opening of the canopy, and increasing moisture by replacement of slow growing species by faster growing Sphagnum spp. (e.g. magellanicum, fallax) that are dependent on constant hydration. Within a forest management context, partial harvest systems have been proposed as a strategy to maintain structural diversity, which is currently not accomplished with low retention systems. However, it is unknown whether these interventions will effectively accelerate community succession. The questions addressed in this study were: (1) is the composition of Sphagnum colonies in partially cut stands more similar to old-growth communities than in control, and low retention cut stands, (2) what aspects of harvest disturbance drive these changes, and (3) is the growth rate of Sphagnum capillifolium (an early successional shade tolerant species) different in partial versus low retention harvest systems? After harvest, Sphagnum patch size was reduced by 19.8% and 11.7% after low retention and partial harvest, respectively. While trends were not constant across three separate partial cut trials, the proportion of Sphagnum magellanicum, Sphagnum fallax and Sphagnum fuscum increased compared to controls and low retention 1–2 years after harvest. Models of percent Sphagnum cover indicated machinery track cover, percent cover of vascular plants, and patch depth were positive factors, while the influence of open canopy varied among species. Despite the inclusion of individual disturbance variables, the summary variable ‘treatment’ was significant in all models. Growth of S. capillifolium in partial cuts was intermediate to growth rates in control and low-retention cuts. Growth was positively influenced by slash cover and, contrary to the patch level, negatively influenced by track cover. These results indicate that partial harvest does represent an intermediate level of disturbance, as direct and indirect harvest effects were reduced, as was Sphagnum death. Change in composition 1 and 2 years after harvest indicates that partial harvests may effectively shift the bryophyte community towards an older community type and may thus be used to create landscape diversity. Long term trends and entire community compositions need to be assessed before this can be stated definitively. However, as paludified stands are less productive, the capacity of these partially harvested sites to produce merchantable timber is questioned.     

Effect of age on the variation, correlations and inheritance of selected wood characteristics in black spruce (Picea mariana)

Summary The variation, correlations and inheritance of various intraring wood characteristics in 15-year-old black spruce (Picea mariana) trees from 40 half-sib families grown in New Brunswick were examined. The emphasis was placed on the effect of age on these genetic parameters. With increasing (cambial) age, ring width and ring density tend to exhibit a constant tree-to-tree variation whereas most other characteristics exhibit a smaller tree-to-tree variation. The heritability for latewood characteristics does not seem to change appreciably. Other characteristics (except RDmi), however, tend to be less heritable when the tree grows older. Correlations between ring density and most intraring characteristics tend to be weaker with increasing age. This implies that fast-growth in this species will have less negative effect on wood density when the tree grows older.The author wishes to thank Dr. E.K. Morgenstern of the Genetic Resource Consultants, Permbroke, Ontario and Mr. D. Simpson of the Canadian Forest Service in Fredericton, New Brunswick for their involvement in the initial planning of this project. Thanks are also due to G. Chauret, T. Keenam, R. Ploure, V. Steel and C. Reitlingshoefer for their technical assistance.     

Influence of climate change,fire and harvest on the carbon dynamics of black spruce in Central Canada

The results of EFIMOD simulations for black spruce (Picea mariana [Miller]) forests in Central Canada show that climate warming, fire, harvesting and insects significantly influence net primary productivity (NPP), soil respiration (Rs), net ecosystem production (NEP) and pools of tree biomass and soil organic matter (SOM). The effects of six climate change scenarios demonstrated similar increasing trends of NPP and stand productivity. The disturbances led to a strong decrease in NPP, stand productivity, soil organic matter (SOM) and nitrogen (N) pools with an increase in CO₂ emission to the atmosphere. However the accumulated NEP for 150 years under harvest and fire fluctuated around zero. It becames negative only at a more frequent disturbance regime with four forest fires during the period of simulation. The results from this study show that changes in climate and disturbance regimes might substantially change the NPP as well as the C and N balance, resulting in major changes in the C pools of the vegetation and soil under black spruce forests.     

Effects of seed water content and storage temperature on the germination parameters of white spruce, black spruce and lodgepole pine seed

The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.     

Reflectance of Alaskan black spruce and white spruce foliage in relation to elevation and latitude

Leaf reflectance at visible and near-infrared wavelengths (400-1000 nm) is related primarily to pigmentation, leaf structure and water content, and is an important tool for studying stress physiology and relationships between plants and their growth environment. We studied reflectance of two co-occurring Alaskan conifers, black spruce (Picea mariana (Mill.) BSP) and white spruce (Picea glauca (Moench) Voss), at elevations from 60 to 930 m a.s.l. along a latitudinal gradient from 61 degrees to 68 degrees N. Black spruce samples were collected from 24 sites and white spruce from 30 sites. Overall, reflectance spectra of the two species were similar, but from 400 to 700 nm, needle reflectance was consistently higher in black spruce than in white spruce (all P 相似文献