Bending strength and modulus of elasticity of Pinus sylvestris round timber from southern Norway

Abstract

To enable use of round Scots pine timber in structural frameworks it is necessary to estimate the mechanical properties of the material. This paper presents data on density, bending strength and modulus of elasticity (MOE) of 533 debarked Scots pine logs with diameter from 75 mm to 250 mm sampled from 10 sites in southern Norway. The results show that round timber can have high values of bending strength and MOE, depending on the sites from which the trees have been collected. Some of the variation in bending properties can be explained by visual characteristics, but since a significant proportion of the residual variance is related to sites, criteria for visual strength grading have to be conservative to be valid across all sites. The potential for machine grading based on measuring MOE is better since this model is more accurate and the random effect of site is smaller.     

Liquid water absorption in uncoated Norway spruce (Picea abies) claddings as affected by origin and wood properties

Abstract

Uncoated Norway spruce specimens from different spatial positions within stems from two origins with different growth conditions were exposed to liquid water over a prolonged time, and apparent diffusion coefficients and rates of void filling were calculated from sorption curves. Both apparent diffusion and rate of void filling were significantly affected by origin and by the difference between inner and outer boards. The differences between inner and outer boards were explained by heartwood proportion and density, but some effects of origin remained when these properties were accounted for. The apparent diffusion coefficient was reduced by increasing density, and increased by increasing heartwood proportion. Void filling rate was reduced by both increasing density and increasing heartwood proportion. Since the effect of heartwood proportion was more pronounced in the material from the highly productive area, it may have been confounded with properties of juvenile wood.     

Genotypic variation in natural infection frequency of Heterobasidion spp. in a Picea abies clone trial in southern Sweden

Abstract

Natural root and butt rot infection with Heterobasidion spp. was recorded on three occasions in trees from a 20-year-old Norway spruce [Picea abies (L.) Karst.] clone trial. In the first assessment, carried out when the trial had been running for 15 years, 29.5% of the trees felled were infected with Heterobasidion spp., but no statistically significant differences were found between the different clones. In the second assessment, also at 15 years, bore cores were taken from 595 trees. Of these cores, 16.5% were infected, but again no statistically significant differences were found between the different clones. Combining the two first assessments also revealed no significant differences. The discrepancy in rot incidence between the two assessments was explained by the inaccuracy of the bore core method. The third assessment was carried out after the trial had been running for 20 years. At that time, 424 trees of 50 clones were felled and sampled. Visible infection was recorded in 46.5% of the trees. The differences between clones were statistically significant and the broad-sense heritability estimate was 0.18. There were no significant genotypic correlations between tree size and rot infection; this is important for the Norway spruce breeding strategy. Calculations show that economic viability would increase by 0.28 SEK per plant for every 10% decrease in root rot frequency at final felling.     

细胞分裂素和硝酸铵对欧洲云杉不定芽伸长的影响

报道细胞分裂素和硝酸铵对欧洲云杉不定芽伸长过程的影响.采用5年生的欧洲云杉1个无性系不定芽丛来研究玉米素和硝酸铵对不定芽生长的影响.试验3种诱导类型(玉米素浓度分别为6.84、13.68、20.52 μmol·L-1,激动素浓度0.69 μmol·L-1,培养4周),玉米素最高浓度处理诱导的伸长芽数量最多,在4个无生长调节剂继代培养过程中,加入了1个硝酸铵浓度逐渐增加的继代培养过程.经不含生长调节剂的低浓度的硝酸铵(2.5 mmol·L-1)培养基的继代培养后转入含有细胞分裂素的诱导培养基,下一个继代培养基补充的硝酸铵浓度分别为2.5、7.5、12.5、17.5 mmol·L-1,8周(2个继代培养)后转入含有硝酸铵浓度为2.5 mmol·L-1的培养基培养.硝酸铵浓度为7.5 mmol·L-1的处理可形成数量最多的不定芽,这对于采用不同浓度的玉米素进行诱导的处理结果是一致的,但随着硝酸铵的浓度增至12.5 mmol·L-1和17.5 mmol·L-1时则不定芽的数量减少.欧洲云杉的胚轴外植体经1次或多次诱导后,细胞分裂素(BA、激动素、玉米素、2iP)促进了不定芽的分化和发育,其中BA由于可诱导产生大量的不定芽而成为最有效的细胞分裂素.玉米素虽然诱导不定芽相对弱一些,却在BA多次诱导后可促进芽的伸长.这对获得具有形成不定芽能力并可扩繁的芽丛非常重要.     

Canopy density in stands of Picea abies and Pinus sylvestris after different thinning methods

Altogether 82 plots (261 estimations) of Picea abies (L.) Karst, and 193 plots (360 estimations) of Pinus sylvestris (L.) stands were estimated by a vertical tube. The “crown free projection”, CFP, of stands thinned in three methods with different thinning grades was measured: unthinned, heavily and very heavily thinned, heavily thinned delayed first thinning, extra heavily thinned and thinned from the top. Basal area (m²ha^?1) density (stems ha^?1) and diameter sum (m ha^?1) were plotted against CFP. Basal area was the best practical measure of stand in this study. Generally Scots pine stands have higher CFP and the curves are steeper than in Norway spruce stands. Depending on the grade of thinning, heavily and very heavily thinned spruce stands, delayed first thinning included, have CFP values of 10–15% and stands thinned from the top, 20–40%, compared with 30–80% and 30–60% respectively in pine stands. Extra heavily thinned stands have the highest CFP, 20–80% in spruce and 50–90% in pine stands. The CFP levels after thinning are too high in pine stands for avoidance of sucker and sprout production of aspen and birch. In dense Norway spruce stands thinned from the top or heavily and very heavily thinned, the CFP values are low enough (≤30%) to diminish the production of suckers.     

Effects of initial spacing on the stem and branch properties and graded quality of Picea abies (L.) karst

The effects of spacing on the stem and branch properties of Norway spruce growing on a good soil in southwestern Sweden were evaluated. Butt logs from sample trees were test sawn, and the boards were machine‐stress graded and graded according to Swedish export rules. Branch diameter and bole diameter both responded positively to an increase in spacing. Quality, as reflected by stress and export grades, increased in response to a decrease in spacing.     

Light quality and growth of Norway spruce (Picea abies (L.))

Seedling of Norway spruce (Picea abies L.) were grown under three different light qualities in fluid-roof growth chambers. Blue light with a high red/far-red ratio decreased shoot length as well as total plant dry weight compared to natural light. Yellow light with a low blue/red ratio did not significantly affect the plants. The effects of light quality were generally the same at 18, 24 and 28 °C day temperature. Plant growth was reduced at temperatures above 24 °C.     

Development and variation of wood density, kraft pulp yield and fibre dimensions in young Norway spruce (Picea abies)

Important wood, pulp and fibre properties were investigated on small wood samples from two Rumanian, one German and one Norwegian provenance of Norway spruce (Picea abies) grown in Sørkedalen, Norway. Several samples were collected from inside each single tree, both in radial and transversal direction in the stem. Data were collected from a total of 59 trees, each 28 years of age. All investigated properties showed close relationship to ring number (RN) (cambium age). For basic density and fibre wall thickness (FWT), a fast decline was first observed when moving from pith to bark and a minimum value was found around RN 5–8. The declining trend was then followed by an increase. Kraft pulp yield, fibre length and fibre width (FW) also increased with RN, but the increase was most pronounced close to the pith. The pulp yield (PY) more or less stabilised outside of RN 5–6. FW showed a decrease outside of RN 10–12, but this was probably due to the remarkable simultaneous drop in ring width for the investigated trees. FW decreased, while basic density and fibre length increased with increasing height in the tree. PY and FWT were not affected by height in tree. Diameter at breast height (DBH) was the most important variable indicating differences between trees in the investigated material. Basic density, fibre length and FWT decreased, while FW increased with increasing DBH. Height to crown had a positive effect on basic density, but had no influence on any of the remaining properties. Differences between provenances were found for basic density, fibre length and FW. The analyses showed that it is possible to describe the variation inside and between trees satisfactorily for a range of important wood and fibre properties.     

Influence of initial spacing and tree class on the basic density of Picea abies

The effects of initial spacing and tree class on the basic density of Norway spruce were evaluated in a stand on a fertile site in southwestern Sweden. The basic density at 0 and 4 m above ground level was significantly higher for trees planted with an initial spacing of 1.5 m than for trees planted with wider initial spacings. A decrease in initial square spacing from 2.5 m to 1.5 m had little effect, of small practical importance, on the basic density. The density at 0 and 4 m above ground was significantly higher for the suppressed trees than for the intermediate and dominant ones, and for the intermediate trees compared with the dominant trees. Differences in basic density appeared to be due mainly to differences in growth‐ring width. Basic density decreased outwards from the pith to the bark at 1.3 and 4 m above ground.     

Comparing predictability of board strength between computed tomography,discrete X-ray,and 3D scanning of Norway spruce logs

Strength graded boards of Norway spruce (Picea abies (L.) Karst.) are important products for many Scandinavian sawmills. If the bending strength of the produced boards can be predicted before sawing the logs, the raw material can be used more efficiently. In previous studies it is shown that the bending strength can be predicted to some extent using discrete X-ray scanning of logs. In this study, we have evaluated if it is possible to predict bending strength of Norway spruce boards with higher accuracy using computed tomography (CT) scanning of logs compared to a combination of discrete X-ray and 3D scanning. The method was to construct multivariate models of bending strength for three different board dimensions. Our results showed that CT scanning of logs produces better models of bending strength compared to a combination of discrete X-ray and 3D scanning. The main reason for this difference was the benefit of knowing the position of where the boards were cut from the logs and therefore detailed knot information could be used in the prediction models. Due to the small number of observations in this study, care should be taken when comparing the resulting prediction models to results from other studies.     

Effect of fungal exposure on the strength of thermally modified Norway spruce and Scots pine

Abstract

Thermal modification at elevated temperatures changes the chemical, biological and physical properties of wood. In this study, the effects of the level of thermal modification and the decay exposure (natural durability against soft-rot microfungi) on the modulus of elasticity (MOE) and modulus of rupture (MOR) of the sapwood and heartwood of Scots pine and Norway spruce were investigated with a static bending test using a central loading method in accordance with EN 408 (1995). The results were compared with four reference wood species: Siberian larch, bangkirai, merbau and western red cedar. In general, both the thermal modification and the decay exposure decreased the strength properties. On average, the higher the thermal modification temperature, the more MOE and MOR decreased with unexposed samples and increased with decayed samples, compared with the unmodified reference samples. The strength of bangkirai was least reduced in the group of the reference wood species. On average, untreated wood material will be stronger than thermally modified wood material until wood is exposed to decaying fungi. Thermal modification at high temperatures over 210°C very effectively prevents wood from decay; however, strength properties are then affected by thermal modification itself.     

Crown morphology of Norway spruce from usual tree measurements

Intr0ducti0nNorwayspruce(PiceaabiesKarst)is0l1eoflI1e111ostimportal1tc011iferinFra11ce.lnl99l,tI1etotaIareaofNorwaysprLICewasestimatedt0be723000I11112.ItsvoIUmewasl27Inilli0I1m3.Tl1eanl1uaIvoILl111eiI1crc-mentwas5.74millionm3.ltiswideIyacceptedII1atIargeri11itialspacingssI1ouldbeusednow.l111940's,thedensity0ftl1epIantatiol1rangedfr0m5000to10000stems/hm2.Nowtl1einitiaIdensityvariesbetweenI000to250Ostems/I1m2.TI1eIargestspacit1g111aybe650~800stems/hm2.S0ithasasignifica11cetostLldyt…     

Effects of Partial Cutting and Scarification on Planted Picea abies at Mid-elevation Sites in South-east Norway

Mortality, injury and height growth of planted Picea abies (L.) Karst, were examined over a 6 yr period in eight stands at middle altitudes (430–620 m a.s.l.) in south-east Norway. There were four residual stand density treatments (shelterwoods of high, medium and low density, 25 × 25 m patch-cut) combined with three scarification treatments (unscarified, patch scarification, inverting) in a split-plot design. Mortality was very low during the experimental period, and did not differ significantly between the residual stand density treatments (mean = 11.1%). Both survival and plant height after 6 yrs were improved by inverting, while patch scarification was intermediate but not significantly different from the unscarified alternative. The patch-cutting resulted in the tallest plants, while only minor differences in height growth were found between the shelterwood treatments. The frequency of injured plants after 6 yrs was not significantly affected by the treatments (mean = 10.6%). The improved plant establishment at inverting is in agreement with previous studies on clear-cuts.     

Dynamic modulus of elasticity and bending properties of large beams of Taiwan-grown Japanese cedar from different plantation spacing sites

The effect of plantation spacings (types A-E) on the bending strength and dynamic modulus of elasticity of 41-year-old Taiwan-grown cedar (Cryptomeria japonica D. Don) was investigated. The results indicate that the highest values for the static bending modulus of elasticity (MOE), modulus of rupture (MOR), and dynamic modulus of elasticity (E_D, E _Dt) occurred in trees obtained from those most densely planted (type A); there was a significant difference between type A and the other four spacing types (B, C, D, and E), but there were no significant differences among those four types. Interrelations among MOE, MOR, E _D, and E _Dt could be represented by positive linear regression formulas, which revealed highly significant differences. The relations among the square value of stress-wave transmission velocity (V_t ² and V_t ²⁾ and MOE, MOR, E _Dl, and E _Dt, respectively, could be represented by positive linear regression formulas. The differences were highly significant.Part of this report was presented at the International Wood Engineering Conference '96, New Orleans, LA, USA, October 1996     

Genetic variation and ortet/ramet relationships in a clonal test with Picea abies

Eight trees were selected at age eight years from seed in each of 52 full‐sib families of Picea abies and were propagated by rooted cuttings. The parents were both of Norwegian and German origin. Results are presented for the variation in height growth in the progeny test and in the clonal test, for rooting percentages, and for plagiotropic growth. More than 40% of the total variance of rooting percentages is of genetic origin. In the set of crosses between Norwegian and German parents 18% of the clones were classified as plagiotropic, while the same number was 27% in the crosses between Norwegian parents. The plagiotropic growth reduces the correlations between ortets and ramets both at the individual and at the family level. Family information is important in the selection of ortets, and a culling of plagiotropic clones seems necessary to obtain a substantial gain from selection.     

Determination of mean diameter by basal area in stands of picea abies and pinus sylvestris in southeastern Norway by means of aerial photographs

Mean diameter by basal area (d_g) is an important stand variable for long‐term economic forecasts of forest holdings. In order to use stand‐by‐stand surveys based on aerial photo interpretation as the data basis for forecasts, d_g has to be determined. The objective was to develop and test a regression function for d_g in mature stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) applicable in southeastern Norway. A study of 700 plots was used to estimate a function for d_g . An additive model was found to be most suitable. The independent variables were potential yield capacity, Lorey's mean tree height, crown closure determined by ocular estimation by means of aerial photographs, and the product of potential yield capacity and crown closure. The R² value was 0.604 and the coefficient of variation was 10.8%. The regression fitted most parts of the calibration data quite well, but it may overestimate the mean diameter in pure spruce stands by 1–2%, and underestimate the diameter in pure pine stands by 3%. For mixed coniferous stands the regression seems satisfactory. Testing by means of an independent data set showed systematic errors of 3–23%. The systematic errors were due partly to calibration problems in connection with the ocular crown closure estimation.     

Pathogenicity of Thekopsora areolata from seed orchards in Finland on Prunus spp. and Picea abies

Pathogenicity of cherry‐spruce rust, Thekopsora areolata, was investigated by inoculations with aeciospores from seven Norway spruce, Picea abies, seed orchards that had suffered from successive severe rust epidemics in the 2000s in Finland. Detached leaves of Prunus spp. were inoculated in the laboratory using aeciospores from cones of various ages. In the greenhouse, live Prunus padus plants were inoculated, and possible autoecism of the rust was tested by inoculations of Picea abies seedlings. Thirty‐five spore sources from the seed orchards formed uredinia on Prunus spp. in the laboratory 2 weeks after incubation, but no telia developed. In the greenhouse, uredinia developed on live P. padus, but no rust symptoms, cankers or sporulation were detected on Picea abies. Thus, no evidence of autoecism was observed among the T. areolata populations and therefore all populations, suggesting all those tested from the Finnish seed orchards were heteroecious.     

Moisture sorption and swelling of Norway spruce [Picea abies (L.) Karst.] impregnated with linseed oil

Abstract

The moisture sorption and swelling of spruce specimens impregnated with linseed oil and unimpregnated controls were studied in two sorption experiments: from 0 to 55% relative humidity (RH) and from 55% RH to water saturation. Sorption isotherms were also determined using a sorption balance. The impregnated specimens had lower rates of both moisture sorption and swelling than the unimpregnated controls; however, there was no significant difference in final moisture contents. In addition, the linseed oil impregnation did not improve the dimensional stability of the wood; in most cases the specimens impregnated with linseed oil swelled more than the unimpregnated controls. For the impregnated specimens, reductions in swelling rates were in most cases seen without corresponding reductions in final swelling. The moisture sorption rate was reduced for the impregnated specimens but there were generally no reductions in equilibrium moisture content.     

Basic density,longitudinal shrinkage and tracheid length of juvenile wood of Picea abies (L.) Karst

Variation in the growth ring width, basic density, longitudinal shrinkage and tracheid length was investigated in the juvenile wood of Norway spruce samples taken from different heights in the stem. Annual height increments were cut from the ten youngest shoots from trees of three different heights. By this method the properties of an individual growth ring could be analysed without taking samples from each ring. Sixteen tree tops of an average stem height of 8, 15 and 25 m were analysed. Basic density was low in the first shoot, highest in the second or third one and decreased gradually thereafter. Longitudinal shrinkage was highest close to the pith and decreased to about 0.2% in the outer rings. Tracheids were only ca. 1 mm long close to the pith and their length increased sharply towards the tenth shoot. The properties of juvenile wood varied with the height in the stem. Longitudinal shrinkage around the pith seemed to increase with increasing height and basic density was highest at 25 m stem height. The applicability of the method for the calculation of basic density and tracheid length in individual growth rings close to the pith is discussed.     

Controlling and predicting the spread of heterobasidion annosum from infected stumps and trees of picea abies

Two Norway spruce stands with heavy infections of Heterobasidion annosum were clear‐cut in 1957 and 1959 in Sweden. The stumps were extracted, the soil sifted to remove most of the roots, and young Norway spruce were planted. After 25 and 28 years, H. annosum had infected 1 % and 2% of trees on plots where stumps had been removed and 17 % and 12% of the trees on control plots, respectively. Several of the H. annosum clones fruiting on old‐growth stumps were also detected in decayed, standing trees. The same fungal clone was found to be infecting adjacent trees from several old‐growth stumps. In addition to old stumps, stumps from recent thinnings and diseased living trees were traced as infection sources. Their relative importance in spreading disease was estimated. Disease risk predictions based on the distance of a tree from various infection sources correlated well with observed frequencies of rot.