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All-cellulose composites (ACCs) are manufactured using only cellulose as a raw material. Biobased materials are more sustainable alternatives to the petroleum-based composites that are used in many technical and life-science applications. In this study, an aquatic NaOH-urea solvent system was used to produce sustainable ACCs from wood-based woven textiles with and without the addition of TEMPO-oxidized nanocellulose (at 1 wt.-%). This study investigated the effects of dissolution time, temperature during hot press, and the addition of TEMPO-oxidized nanocellulose on the mechanical and thermal properties of the composites. The results showed a significant change in the tensile properties of the layered textile composite at dissolution times of 30 s and 1 min, while ACC elongation was the highest after 2 and 5 min. Changes in hot press temperature from 70 °C to 150 °C had a significant effect: with an increase in hot press temperature, the tensile strength increased and the elongation at break decreased. Incorporating TEMPO-oxidized nanocellulose into the interface of textile layers before partial dissolution improved tensile strength and, even more markedly, the elongation at break. According to thermal analyses, textile-based ACCs have a higher storage modulus (0.6 GPa) and thermal stabilization than ACCs with nanocellulose additives. This study highlights the important roles of process conditions and raw material characteristics on the structure and properties of ACCs.

The physical, mechanical, and chemical properties of both stem wood and knot wood were investigated from two subfossil Scots pine (Pinus sylvestris L.) trunks retrieved from a lake in Finnish Lapland, dated to 404–486 CE and to 1318–1444 CE. Both the stem wood and the knot wood of the younger trunk had higher moisture content, lower density, and lower strength properties in comparison to the older trunk. The ash content of the stem wood of the younger trunk was lower, but the ash content of the knot wood was higher than that of the older trunk. Due to the degradation that occurred over time, all the values of physical and mechanical properties were lower compared to typical values of recently grown Scots pine wood. The chemical composition of both stem wood samples was close to the composition of the recently grown wood, and the only exception was the small decrease of the cellulose and hemicellulose in the subfossil samples. The bulk extractives were well-preserved, but terpenes and fatty acids underwent transformation, resulting in more stable compounds. The SWOT analysis (strengths, weaknesses, opportunities, and threats) showed pros and cons for the productization of subfossil wood, with the branding value of an ancient material being the potential enabler in developing commercial niche uses.

The demand for wood has increased in recent years due to new technical possibilities and environmental concerns. This paper provides an analysis of the factors that affect the use of wood in the construction sector, and an assessment of their importance in individual countries and for groups of stakeholders. The study covers the technical, societal, political, economic, and gender aspects of wood construction, with the aim of increasing global understanding regarding national differences, the current situation, and the potential for further development. The subject was investigated using a survey, and the most important opportunities for and barriers to growth in the use of wood in the construction sector were selected, following a statistical analysis. The results indicate strong regional and cultural differences regarding the acceptance of some of the opportunities and barriers related to the development of wood construction. The findings indicate that there is a need to promote wood construction based on its technical and economic benefits rather than its societal ones. On the other hand, the current societal barriers should be addressed as a priority, together with the establishment of common and harmonized policies. The results of this study, therefore, will contribute to the generation of regional-sensitive information that can be useful for policymakers when updating the building codes in their individual countries. This research was funded by the European Union’s HORIZON 2020 research and innovation program, under grant agreement No 862942.

Low density and poor mechanical performance often limit utilisation of sawn wood from fast-growing plantation forests. Thermo-hygro-mechanical modification (THM) of timber is one innovation for improving the properties of light-weight wood species. The objective of this study was to determine the effects of THM and subsequent thermal treatment on dry density, modulus of elasticity (MOE), compression strength, Brinell hardness, and swelling behaviour in immersion tests on two fast-growing Vietnamese species, acacia (Acacia mangium) and rubberwood (Hevea brasiliensis). Test boards were modified in an industrial kiln, in which a tangential thickness compression of 14% and 12% were aimed for acacia and rubberwood, respectively, either with or without subsequent thermal treatment at 210 °C. Dry density, MOE, Brinell hardness, compression strength, and dimensional changes in water immersion tests of specimens were measured from the modified and unmodified reference materials, the latter ones being kiln dried at 50 °C. The results showed that the responses of the mechanical properties were more evident for rubberwood than for acacia. In rubberwood, the MOE and compression strength of wood thermo-hygro-mechanically modified with or without thermal treatment were higher than those of kiln-dried reference specimens throughout the thickness profile. In case of acacia, similar differences between the modified and reference specimens were observed only in the surface layer. Density and Brinell hardness of thermo-hygro-mechanically modified rubberwood were higher than those of reference specimens, but after thermal treatment they did not differ from (acacia) or were lower (rubberwood) than those of THM specimens. Post-compression thermal treatment increased the hydrophobicity of THM specimens.

The behaviour of industrially modified wood has not been systematically evaluated in controlled exposure conditions. The objective of this study was to assess the equilibrium moisture content (EMC), dimensions, and Brinell hardness of thermally modified wood in different conditions of temperature and relative humidity (RH). Tested materials consisted of European ash (Fraxinus excelsior L.), Norway spruce (Picea abies (L.) Karst.), and Scots pine (Pinus sylvestris L.) that were thermally modified according to ThermoWood industrial processes into the classes Thermo-S and Thermo-D. The properties were measured at the following conditions: 20 °C and 65% RH, 10 °C and 90% RH, and 30 °C and 30% RH. The results show that the reduction of EMC and the improvement in dimensional stability are dependent on the degree of thermal modification. Thermal modification was more resistant to moisture absorption at 20 °C and 65% RH than at 10 °C and 90% RH and 30 °C and 30% RH, and the more severe modification decreased the difference among different exposure conditions. The tangential–radial ratio of swelling and shrinkage was higher for thermally modified wood than for nonmodified wood. Brinell hardness of modified Scots pine and Norway spruce did not differ significantly from that of nonmodified wood in normal and dry conditions, but the more humid conditions increased the difference by 12%–17%.

Ways to long-term storage of carbon molecules captured as CO2 from atmosphere are looked for. Timber structures act as carbon storages and timber construction is sometimes claimed as a solution to ...

Highlights • Wood-based substitution benefits are likely to decrease over time • Carbon residence has more importance in the future as an indicator • Energy use of wood should be reduced to increase climate benefits • Global agreement is needed to fund clean technologies and reduce fossil ones To obtain net climate benefits from intensified forest utilization in the short-term, the substitution impact of wood harvesting and increased carbon stocks of wood-based products should be higher than the forest carbon stock loss. However, the product specific substitution impacts change dynamically over time along with technological development, and long-term climate change mitigation strategies need to consider this, as well as the market forces. We identified future pathways enabling globally market viable environments for wood utilization scenarios in Finland resulting in net climate benefits in 2050. We I) indicated substitution impacts in 2050 applying future-oriented parameter modification based on LCA, and developed quantitative target scenarios by altering wood-based product portfolios to achieve required substitution, and II) identified pathways enabling scenarios by applying participatory backcasting. In the scenarios, a major shift from primary energy use to high added-value products including textiles, chemicals, composites and advanced biofuels, or long-lifetime construction products was needed and more lifecycles for wood products by recycling were required. The actions enabling market viable environment focused on the global level policies and consumer perceptions, while actions locally were limited and current production technology development oriented. We recommend multi-target backcasting together with LCA to analyse more synergies and trade-offs.

Thermally modified wood (TMW) is widely used in outdoor applications due to its advanced properties towards weathering stresses. Although the structure changes of TMW from weather factors have been reported, investigation of the quantitative analysis of water states and cell wall structure of TMW after weathering is limited. In this work, the amount of bound water, fiber saturation point (FSP), cell wall pores, and free water distribution of thermally modified Scots pine, Norway spruce, and European ash were measured before and after a 2-year natural weathering via NMR relaxometry, cryoporometry, and magnetic resonance imaging. The results show that weathering increased T2 relaxation time of lumens, indicating the degradation of tracheids and vessels, especially in TMW compared to unmodified wood. The amounts of bound water, FSP value, and cell wall pores were increased after weathering; however, an increase in thermal modification intensity resulted in lower FSP and limited the increase in number of pores. In summary, TMW showed better performance than unmodified wood after weathering.

Moose ( L.) browsing causes severe damage in Scots pine ( L.) seedling stands. The effects of this damage on the quality of sawlogs were studied in a long-term controlled experiment. This article reports the stem size and external quality characteristics of Scots pine stems 34 years after artificial moose browsing damage. Damaging the trees by clipping the main stem at the seedling stage reduced the diameter, height, and tree volume of the trees at the end of the experiment. The tree growth reduction was dependent on the severity of clipping. The differences between the damaged and the control trees were more obvious in diameter than in height at the time of final felling. Stem form defects and vertical branches were the most typical externally detectable defects caused by clipping. Defects in the butt logs were detected in 71–89% of the damaged trees, depending on the clipping treatment severity. The stronger the clipping treatment, the more likely the stem form was defected and the more commonly were vertical branches and crooks detected in the stems. The results indicate that both tree dimensions and stem quality suffer from moose browsing. The findings of this controlled experiment more likely underestimate than overestimate the damage in comparison to real moose browsing. Further analyses are required to assess the effects of browsing damage on the internal quality of sawlogs and subsequent economic outcomes.Alces alcesPinus sylvestris

The process of thermal modification can increase the dimensional stability and fungal resistance of wood, thus improving its performance in outdoor applications. This paper investigates the chemical and structural changes in thermally modified and unmodified Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) wood caused by long-term soaking, with a focus on the dynamics of the timber surface properties. Fourier transform infrared spectroscopy, pH measurements and microscopy analysis were conducted in 2-week intervals for 14–20 weeks. The main chemical degradation of the wood, which was attributed to the changes in hemicelluloses and cellulose, was identified by the decreased carboxyl signal and the increased intensity of C–O stretching after soaking. The crystallinity and hygroscopicity of the wood were also affected by soaking. The pH level of the modified wood did not change markedly during soaking. However, the initially low pH values of the thermally modified wood, combined with the effect of water, probably facilitated the wood degradation processes, thus leading to an increased number of cracks and holes, especially in the outer parts of the cell walls.

In Siberian larch, shear strength (SS) is lower in sapwood (sW) than in mature heartwood (hW) despite the similarity of their cell structures. In sW, SS was not correlated with other properties, not even with density. The aim of the present study was to find the parameters affecting the SS in sW. The diameters of earlywood (EW) and latewood (LW) tracheid lumens [radial diameter (RD)], as well as their double wall thicknesses (2CWTs), were measured from different wood types. The 2CWT beside the resin canals was measured and rays were counted. The wall:lumen ratio of tracheids was calculated. None of the measured and calculated characteristics significantly correlated with SS in hW, while a high 2CWT and wall:lumen ratio of EW increased the SS and a large RD decreased the SS in sW. Tracheids of sW were larger and their walls were thicker than those of mature hW. The EW of sW sheared through tracheids, but practically never through rays, while in the EW of mature hW, both rays and tracheids could be sheared. It is suggested that change in viscoelastic properties, occurring in cell walls during the transformation from sW to hW, improves wood shear properties.

Air-coupled ultrasound and electrical impedance spectroscopy are non-destructive measurement methods, which can be used, for example for quality assessment of sawn timber. Both methods may be used in through-transmission and one-sided reflection mode to measure internal properties and detect defects in wood materials. The ultrasound method is based on mechanical waves and is mainly affected by the mechanical properties of wood. Density affects both methods, and the electrical impedance method is especially affected by moisture content and the chemical properties of wood. In this study, the relations between the methods and the bending properties of air dried and modified aspen (Populus tremula L.) specimens were examined. The modification method was a combination of compression and thermal modification. According to the study, electrical impedance spectroscopy combined with air-coupled ultrasound measured across the grain is a potential non-destructive technique for the strength estimation of aspen wood.

This paper investigates and models the effects of pruning season and tool on wound occlusion with varying tree and branch characteristics of silver birch (Betula pendula Roth) stems at the pruning height of 0−4 metres. Dates of eight secateurs prunings, three saw prunings and two sticks prunings as well as unpruned control were tested in permanent plots on four sites. Knot occlusion and discolouration in stemwood were measured from about 1600 studied knots of 112 sample trees felled five to six years after pruning in 2010. Knot occlusion rate was modelled according to pruning tool, date, tree growth, and branch characteristics. The occlusion was the fastest in trees pruned in spring or early summer, and the slowest in trees pruned in autumn. Stubs of living branches occluded faster than the dead ones with the same diameter. Saw pruning resulted in clearly better occlusion rates than secateurs pruning, caused by the shorter knot stubs after saw pruning. Hitting dead branches away with a stick resulted in the worst occlusion status. The colour defects spread more often upward from the knot than downward. Discolouration in stemwood was detected more frequently near to the pruned branches than the unpruned ones, and more widely near to the stubs of dead branches than the living ones. Most saw and secateurs pruned branches were completely occluded during the experiment, so these prunings were suitable for all branches under 20 mm in diameter, and for living branches even up to 30 mm in fast-growing trees.

Understanding the state of market for modified wood as well as the forces that affect its future development will be essential for those seeking to enter the Russian market. Information on modified wood from websites of companies, research and development organisations, woodworking-oriented magazines and forums, and official Russian statistics were explored, and finally verified by personal contacts with experts. A number of modification methods have been either researched, developed or pre-commercialised during the past 15 years, but only few of them have been adopted by users. Mostly, the modification methods have been copied, further developed and commercialised from variations of thermal modification originally introduced in Western Europe. Modified wood products are still considered premium goods among Russian consumers. Political initiatives aim at increasing the share of wood in construction and renovation but also at import minimisation, which reduces the penetration of foreign producers i...

In order to survive, the wood degrading microbes need a moisture content of wood exceeding the fibre saturation point, i.e. , 26%–32%, depending on the species. Maintaining wood moisture content below this level effectively prevents biodegradation. This can be achieved either by preventing wood's exposure to liquid water or increasing the hydrophobicity of wood by some impregnation or modification treatment. The objective of the study was to define the dimensional stability in changing environmental conditions, as well as the water absorption and desorption behaviour of untreated, copper-chromium impregnated and pine oil treated glulam. Scots pine was used for pressure impregnated and pine oil impregnated beams while the reference beams were made of Norway spruce, which is the most commonly used species for glulam production nowadays. The 6 inner lamellae of the glulam beams originated from small-sized logs, whereas the surface lamellae were made of larger logs. Beams with 44 × 200 mm cross cut dimensions were glued using melamine-urea-formaldehyde resin, and divided into three treatment groups. Treatment 1 was not impregnated (Norway spruce), treatment 2 (Scots pine) was impregnated with copper-chromium based preservative in commercial pressure impregnation process, and treatment 3 (Scots pine) was impregnated with pine oil using the process of Ekopine Ltd. After the treatments, 20 glulam specimens with dimensions of 44 × 200 × 170 mm (thickness–width–length) were produced from each treatment group. The cross-cut surfaces of the specimens were sealed using waterproof varnish to ensure that the water movement took place only through the side surfaces of the specimens. The air-dry specimens (MC 7.7–12.6%) were immersed into water for 6 weeks, during which period they were weighed repeatedly. After the immersion treatment, they were brought to a standard climate (65% RH, 20 °C temperature). Again, their mass was recorded until it did not change anymore. Then the same specimens were taken into a weather chamber where they were subjected to four 2-week-long test cycles with varying temperature and relative humidity, totalling 8 weeks of artificial weather exposure. Pine oil impregnated specimens resisted the water absorption significantly better than the untreated and pressure impregnated specimens. Due to the low initial MC after the absorption period, pine oil impregnated specimens also dried rapidly below 20% MC, while the drying of untreated and pressure impregnated glulam to the same level took 3–4 weeks in standard climate. The pine oil impregnated specimens had clearly better dimensional stability in the weather chamber, compared with the untreated and pressure impregnated specimens. Also the mass variation of pine oil impregnated specimens was significantly reduced in comparison to the other two treatment groups, indicating lower hygroscopicity for the pine oil treated specimens. To conclude, the pine oil impregnation of wood can be considered as an effective preservation method against moisture exposure. It appears to be a promising method to prevent biodegradation by maintaining the moisture content of wood below the level that enables mould and fungal growth.

Present in high concentrations in the heartwood of Larix species, water-soluble arabinogalactans affect the density, moisture content and processing properties of larch wood. The aim of this study was to chart arabinogalactan concentration (AC) and to define the relations between arabinogalactans, and density and shear strength at different axial and radial locations in Larix sibirica Ledeb. trunks. In addition, growth rate (ring width, fibre dimensions) was compared with AC to determine the link between them. Although quite low AC levels were observed, values differed significantly between sapwood and heartwood, with a slight increasing trend from pith to mature heartwood. Variation in growth rate affected AC levels in juvenile wood only. In conclusion, AC levels were clearly lower in the studied cultivated, fast-grown Siberian larches than those measured earlier in trees of natural origin. AC had a weak correlation with growth rate and shear strength.

The purpose of this study was to determine the effective refractive index of thermally modified Scots pine (Pinus sylvestris L.) wood specimens as a quantitative measure regarding the change of wood density which is due to the thermal modification. The refractive index of thermally modified Scots pine wood was obtained by introducing pine wood powder into an immersion liquid and measuring light backscattering with a homebuilt multifunction spectrophotometer. The present method provides useful information that in principle can be applied, for example, in the optimization of the thermal modification process and inspection of the quality of thermally modified wood.

Mechanical properties are very important in structural uses of wood. In the case of larch wood, shear strength (SS) may be a limiting property, because the wood is brittle and it splinters easily. In this study, SS of Siberian larch (Larix sibirica) wood was studied in relation to its axial and radial location and to some other wood properties in the part of the trunk that produces logs of good carpentry quality. SS increased by 21–23% from the pith to the outer heartwood at each studied height (butt, 4.5 and 9 m), and it was at its most approximately 7% higher at the butt than at the other studied heights. The main reason for the radial increase in SS was the increase in density caused by wood maturation, but other factors also affected SS, depending on the grouping mode (combined material, radial/axial location). An exception was sapwood, for which no factors affecting SS could be identified. Thus, sapwood may behave differently from heartwood regarding use, even unexpectedly. The results sugge...

The decay resistance of European (Populus tremula L.) and hybrid (P. tremula x tremuloides) aspen wood against brown-rot fungi was investigated after three different treatments, i.e. conventional drying, press drying and heat treatment. For both aspen species, the mass loss after exposure to Gloeophyllum trabeum was higher than after exposure to Coniophora puteana, regardless of the wood treatment. Conventionally and press dried aspen wood had similar mass losses. However, heat treatment appears to be an effective method to improve the decay resistance of aspen wood, reducing the mass loss by about 30% compared with conventional and press drying. As a function of mass loss, wood exposed to G. trabeum had lower moisture content than wood exposed to C. puteana. This is thought to be due to differences in the degradation pattern between the two brown-rot fungi. On the other hand, European aspen appears to be slightly more resistant to decay than hybrid aspen.

Growing markets for chopped firewood have created alternative uses for the by-products of sawmills. Based on empirical data and simulated results, the potential of birch (Betula pendula Roth, Betula pubescens Ehrh.) from commercial thinnings for combined industrial production of sawn timber and firewood billets was investigated. In the simulations, different sawing patterns were used for logs intended to combine production of sawn timber and billets for chopped firewood (‘sawlogs’), and for logs intended only to firewood production (‘firewood logs’). Finally, economical feasibility analysis was done concerning the differences between the sawmills’ traditional business concept and the novel concept combining sawn wood and firewood production. The bucking results for the volume yield of different timber assortments varied only slightly between the different bucking options, i.e. the combinations of timber assortments. The main differences in the volumes of timber assortments were due to the stand t...

The Brinell hardness and equilibrium moisture content (EMC) were measured from thinning-aged silver birch wood. Wood material both from the trees harvested in the first commercial thinning and from trees remaining on site after the thinning was included. The average Brinell hardness was 19.40 MPa. It correlated significantly with the basic density of wood. With respect to the distance from the pith, the Brinell hardness of air-dried wood was higher than that of artificially dried wood. The average EMC of the conditioned (20°C, 65% relative humidity) wood was 12.0%. The EMC of the wood also varied, with the EMC being higher for air-dried wood than for kiln-dried wood. EMC was the highest at a distance of 30–40 mm from the pith, decreasing towards both pith and log surface. Seasonal variation in both the Brinell hardness and the EMC of the wood was found. It was presumed to be a consequence of season-dependent physiological changes in trees.

In the future, the building industries will need predictable, homogeneous and cost-competitive wood products with structural safety in increasing quantity and quality. This can be provided by, e.g., breaking solid wood and reconstructing the structure in a way that the degrading influence of knots, cracks, decay and other natural irregularities in wood will be eliminated. Beams, panels or boards made by this principle are called the engineered wood products (EWP). The purpose of this study was to investigate the possibilities to utilize small-diameter Scots pine and birch timber for production of EWPs that are reconstituted of strands. The wood technological characteristics of the tree species used in these products worldwide were studied based on the literature, and the findings were compared to the characteristics of domestic woods. In addition, test specimens were manufactured from domestic raw materials of Scots pine and birch species, and tested in order to examine the differences between wo...

The purpose of this study was to determine the modulus of elasticity (MOE) and the modulus of rupture (MOR) in the radial bending test for small, clear specimens of Finnish birch (Betula pendula Roth and B. pubescens Ehrh) wood originating from mature trees. The dependency of MOE and MOR on the specific gravity of birch wood was studied, and the relationship between MOE and MOR was modelled at the different heights and at the different distances from the pith of the tree. For B. pendula, the mean values for MOE and MOR were 14.5 GPa and 114 MPa, whereas B. pubescens had means of 13.2 GPa and 104 MPa, respectively. At the corresponding specific gravity, the bending stiffness and strength values did not differ between the two species. The results indicated a linear relationship between the MOE and MOR, irrespective of the birch species or the within-stem location. Both MOE and MOR increased clearly from the pith towards the surface of the tree and decreased slightly from the base to the top of the tree. It seems that if products with as high stiffness and bending strength as possible are wanted, sorting of raw materials into different grades according to their within-tree origin can be of value.

The objective of this study was to examine the timber quality of silver birch (Betula pendula Roth) and European white birch (Betula pubescens Ehrh.) trees in the first and second thinnings in southern parts of Finland, from the viewpoint of sawing of small-diameter, short logs, in particular. The average stem volume of birch was 0.140 m in the first thinning stands and 0.206 m in the second thinning stands. In planted stands, the trees were larger in the first thinnings but slightly smaller in the second thinnings, compared with naturally regenerated pure birch stands or mixed stands of Norway spruce and birch species. Almost 60% of the harvested and 35% of the remaining stems that could provide saw logs were graded as pulpwood for timber quality due to the occurrence of stem defects. The most common stem defects were multiple crooks and middle crooks. Only minor between-stratum differences were detected in the numbers of defects. Depending on the bucking option, the total percentage of saw and plywood logs from the total birch recovery in the thinning of the sample stands varied between 11.7 and 18.2. The recovery of saw logs was clearly higher in the second thinnings, 12–19%, than in the first thinnings, 8–14%. Of the stand types, saw log recovery was the highest in planted birch stands, 12–19%, but lower in naturally regenerated pure birch stands and mixed stands of Norway spruce and birch. The highest share of saw logs was in the second thinning of planted stands, 17–25%. This study shows that the harvesting recoveries of end-use based timber assortments can be estimated in different kinds of thinning birch stands. Based on tree and log dimensions and stem squality, silver birch firstly from plantations and secondly from mixed stands should be the most interesting source of raw material for the saw milling, furniture and interior product sectors.33

This article reports the impacts of three different drying treatments on selected physical and mechanical properties of European (Populus tremula L.) and hybrid (P. tremula × tremuloides) aspen wood. The material originates from 5 European aspen stands and 7 hybrid aspen stands in southern and central Finland. After processing the logs at a saw mill, sawn timber samples were dried using 1) conventional warm air drying, 2) press drying, or 3) heat treatment into Thermo-S grade by the Finnish Thermowood® method. Finally, small clearwood specimens were manufactured from different within-stem positions for the measurements of physical and mechanical properties. Both press dried and heat treated specimens absorbed water at significantly slower pace than the conventionally dried specimens. In normal climate, the conventionally dried, press dried and heat treated specimens conditioned at equilibrium moisture contents of 12.2, 8.7, and 8.9 per cent, respectively. It appears that the butt logs between 2–6 metres contain the lightest and, thus, weakest wood in aspen stems. Radial compression strength was at its highest in heat treated specimens, whereas conventionally and press dried specimens did not differ from each other. Press dried specimens had the highest longitudinal compression strength, also heat treated specimens showed higher values than the conventionally dried ones. Radial Brinell hardness of press dried specimens was higher than that of conventionally dried or heat treated specimens. Both modulus of elasticity and modulus of rupture were at their highest in press dried specimens. Irrespective of the drying treatment, the tangential shear strength of European aspen specimens was approximately 5% higher than that of hybrid aspen. Heat treated specimens indicated significantly lower tangential shear strength values than the conventionally dried ones. In case of both aspen species, the longitudinal tensile strengths of heat treated specimens were significantly lower than those of conventionally and press dried specimens. Heat treated specimens had the highest variability among the results. The inherent flaws in aspen wood material, e.g., wetwood and density fluctuations, increase especially the property variability of heat treated wood.

Seloste artikkelista: Influence of saw and secateur pruning on stem discolouration, wound cicatrisation and diameter growth of Betula pendula. Silva Fennica 42 (2008) : 2, s. 295-305.

The aim of this case study was to compare the impacts of saw and secateur pruning on silver birch (Betula pendula Roth). Data were collected from two saw pruned stands in 2005, and one secateur pruned stand in 2003. All the stands were located in southern Finland. The sample stems were felled, and their butt logs were sawn into flitches, whose knot features and colour defects were measured. In addition, discs were sawn from each stem in order to study the annual ring widths. In this material, pruning with secateurs appeared to cause less colour defects than pruning with a saw. Irrespective of the pruning method used, the colour defects in the stem wood were at their largest in cases where the basal knob or the stem bark appeared to be damaged by pruning. Colour defects spread mainly towards the pith, only in a few cases towards the stem surface. The cicatrisation time of the knots as well as the length of the bark stick remaining inside the stem did not show significant differences between the two pruning methods. Pruning of the lowest living branches appears to have no effect on the diameter growth of silver birch trees.

The purpose of this study was to investigate the variation in selected technical properties of mature (age > 60 years) birch stems in southern and central Finland. Technical properties were defined as the natural external characteristics that cause differences in the usability of a certain section of stem in the mechanical wood industry, saw milling in particular. On mineral soils, birch stems in mixed stands were slightly larger than those in pure birch stands. On peatlands, however, birch stems in pure stands were larger than those in mixed stands. The average stem form of silver birch was straighter than that of white birch. Small-sized log sections of white birch, as well as those of codominant silver birch, typically contain many dead knots. On mineral soils, coniferous admixture had a positive effect on self-pruning of white birch. Self-pruning of silver birch was as good in pure birch stands as in mixed stands of spruce and birch. Occurrence of decay did not differ significantly between the two birch species. Not only silver birch, due to the growth and yield of the stand, but also vigorous and good-quality white birch, because of the possibility to provide high-quality logs, can be maintained profitably as an admixture in coniferous forests until final cutting.

Tutkimuksen tavoitteena oli määrittää ohileikkaavilla oksasaksilla tehtävän rauduskoivun pystykarsinnan aiheuttamien väri- ja lahovikojen määrää ja analysoida esimerkkilaskelmin pystykarsintatyön kannattavuutta metsänomistajan ja koivutukkia käyttävän teollisuuden kannalta. Tutkimuksen aineistona käytettiin kolmea pystykarsittua metsikköä sekä kolmea näitä ominaisuuksiltaan vastaavaa pystykarsimatonta vertailumetsikköä Vammalasta, Jämsänkoskelta ja Keiteleeltä. Kannattavuutta tutkittiin empiirisen aineiston perusteella saatujen tulosten laskennallisena sovelluksena. Kannattavuuden tunnuslukuina olivat investoinnin nettonykyarvo ja sisäinen korkokanta. Mittaukset osoittivat aineistossa olleen vähemmän väri- ja lahovikoja kuin aiemmissa tutkimuksissa, joissa karsintavälineenä on käytetty oksasahaa. Alle 20 mm:n läpimittaisten oksien karsinnan aiheuttama värivikaantumisriski oli vähäinen. Rauduskoivun kasvu ei taannu elävienkään oksien karsinnan seurauksena, jos elävää latvusta säilytetään suositellut 50 % puun pituudesta. Pystykarsinta parantaa tyvitukkien laatua ja lisää esimerkkilaskelmien perusteella päätehakkuun kantorahatuloja. Ulkopuolisellakin työvoimalla tehdylle pystykarsintasijoitukselle voi saada 5–6 %:n sisäisen koron. Myös vaneri- ja viiluteollisuuden kannattaa maksaa keskimääräistä korkeampaa hintaa pystykarsituista koivikoista. Pystykarsinta lisää tyvitukeista saatavan viilun arvoa n. 20–30 prosentilla.