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1.
Abstract

Wood density is an important quality variable, closely related to the mechanical properties of the wood. Precise wood density measurements in the log sorting would enable density sorting of logs for products such as strength-graded wood and finger-jointed wood. Density sorting of logs would also give more homogeneous drying properties and thus improve the quality of the final products. By compensating the radiographs from an X-ray log scanner for the varying path lengths using outer shape data from a three-dimensional (3D) scanner, it is possible to make precise estimates of both green and dry density. Measurements on simulated industrial data were compared with densities measured in computed tomographic (CT) images for 560 Scots pine (Pinus sylvestris L.) logs. It was found that green sapwood density could be measured with predictability R 2=0.65 and root mean square error (RMSE) of 25 kg m?3. Green and dry heartwood densities were measured with similar precision: R 2=0.79 and RMSE=32 kg m?3 for green density and R 2=0.83 and RMSE=32 kg m?3 for dry density.  相似文献   

2.
ABSTRACT

The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2?>?0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT.  相似文献   

3.
A trial set-up with methods for sampling, treatment and analysis of small wood chips are presented in this paper, to determine important wood and fibre properties, like basic density, dry density, volume swelling of wood, Kraft pulp yield, fibre length, fibre coarseness, fibre width, lumen width and fibre wall thickness. The required time for one sample is about 1.5 man-hour, but this requires relatively larger series and trained personnel. Acceptable measurement accuracy is achieved when the volume of the wood sample is at least 1.5 ml, except that of wood volume swelling. To gain acceptable measurement accuracy for volume swelling, the wood volume should be increased to at least 3 ml, and preferably more than 5–6 ml per sample. The level of pulp yield and wood density do not show a significant effect on the measurement accuracy for fibre cross-section dimensions. Fibre coarseness, on the other hand, has a significant influence on these accuracies. A double measurement of fibre coarseness will improve the accuracy to an acceptable level. The method presented here may, together with information about trees and growth locations, form the basis for greater insight into the mechanisms involved in development of wood and fibre properties in trees, which in turn may provide better control and utilisation of wood for pulp and paper production.Abbreviations CWD cell wall density in dry wood=1500 kg/m3 - Ww dry weight of wood (kg) - Vmax green (wet) volume of wood (m3) - Vmin dry volume of wood (m3) - BD basic wood density (kg/m3) - DD dry wood density (kg/m3) - VS maximum volume swelling of wood (%) - Wp dry weight of pulp (kg) - PY pulp yield (%) - C fibre coarseness, the average weight of a unit length of fibre (g/m) - CL average chip length (mm) - CWT average cell wall thickness (m) - FW average fibre width (m) - l average native fibre length in solid wood - L chip length - lc average fibre length in wood chip (mm) - Lc length-weighted fibre length in wood chip (mm) - lw native average fibre length in wood (mm) - Lw native length-weighted fibre length in wood (mm) - LW average lumen width (m) - llw average native fibre length, length weighted, in wood - X average fibre length in chip - Xlw average fibre length, length weighted, in chip  相似文献   

4.
Abstract

Tree mortality, its causes, and the input of dead charred wood were studied in 11 managed 30–45-year-old Scots pine (Pinus sylvestris L.) stands 1 year after experimental low-intensity prescribed burnings in southern Finland. First, the relationship between fire-induced tree damage and several external variables, e.g. stand density, within-stand wind speed, open-air wind speed, the Finnish Forest Fire Index (FFI) and flame height, was studied. Secondly, the study examined which damage and morphological characteristics best predicted tree mortality. Tree mortality was very variable in the experimental plots, ranging from 0% to 48% on the basis of stem number and from 0% to 41% in terms of wood volume. The input of dead and charred wood decreased with stand age, being 19.4 m3 ha?1 in 30–35-year-old stands, but only 1.7 m3 ha?1 in 45-year-old stands. The input of dead wood was on average 10 m3 ha?1, representing less than 5% of the mean volume before the prescribed fire. The external variables that best explained fire-induced damage were within-stand wind speed, flame height and FFI. Tree mortality was best predicted by charred stem ratio with bark thickness, and by charred stem ratio with tree diameter. The results indicate that prescribed burning that is conducted downwind increases tree mortality and changes subsequent stand structure with increasing within-stand wind speed.  相似文献   

5.
Abstract

The potential of near infrared spectroscopy (NIRS) to estimate wood moisture content (MC), surface energy characteristics and adhesive bond strength were evaluated on aspen (Populus tremuloides Michx.) veneer subjected to different drying times. For samples dried progressively at 103°C, the best MC prediction model was for the total MC range (0–100%) with an R2 value of 0.68. However, exposure at 180°C produced surface colour changes, and the CIE L*a*b* colour parameters measuring colour changes were better estimated using the 400–900 nm spectral data than the 1100–2400 nm spectral data. Increased exposure time at 180°C resulted in lower wettability and, hence, larger contact angles, especially when ethylene glycol was used as probe solvent. Lap shear strength tests on veneers showed that adhesion by phenol formaldehyde resins was impaired by the high temperature exposure; however, the lap shear strength test had high variability so there was not always a clear relationship between contact angle and lap shear strength test.  相似文献   

6.
《Southern Forests》2013,75(4):311-318
Average wood density of 38-year-old Cariniana legalis (Mart.) Kuntze, a Brazilian native forest species, was found to increase with faster growth and lower stocking, while decreasing from pith to bark. A complete randomised block design was planted with five blocks. Ten trees were harvested in each of three spacing treatments. We hypothesised that the stand stemwood production would not significantly differ depending on tree spacing. However, tree growth would be higher in the wider spacing and wood density would be higher in the narrower spacing. The diameter growth of trees was higher at 3 m × 2.5 m than at 3 m × 2 m and 3 m × 1.5 m. Nevertheless, this higher individual tree growth at 3 m × 2.5 m did not compensate for the greater tree stock density at 3 m × 1.5 m with stand stemwood production at 38 years of 530 m3 ha?1 and 649 m3 ha?1, respectively. These results suggest that C. legalis, which can produce up to 17 m3 ha?1 y?1 of medium-to high-density timber – about 800 kg m?3 – is a promising native species for forest plantations in Brazil.  相似文献   

7.
《Southern Forests》2013,75(2):85-92
A performance comparison of seven-year-old individuals of 13 Casuarina species/provenances in terms of survival, growth (diameter, height and volume), wood basic density and wood biomass was undertaken at Kongowe, Kibaha, Tanzania. The trial was laid out using a randomised complete block design with four replications. The results showed significant differences (P < 0.0001) in all parameters. Casuarina equisetifolia from Montazah National Park, Egypt, had the lowest untransformed survival (48.8%), whereas C. equisetifolia from Wagait Tower (North Timor), Indonesia, had the highest survival (87.5%). Casuarina equisetifolia from Montazah National Park, Egypt, had the lowest mean diameter (8.6 cm) while the C. junghuhniana provenance from Timor, Indonesia (seedlot no. 19489) had the highest diameter (14.8 cm). Casuarina equisetifolia from Montazah National Park, Egypt, had the lowest mean height (16.2 m), volume (22.1 m3 ha?1) and biomass production (23.5 t ha?1), whereas C. equisetifolia from Hadsamira Songkhla, Thailand, had the highest mean height (24.3 m), volume (66.4 m3 ha?1) and biomass production (72.9 t ha?1). In terms of wood basic density, the C. junghuhniana provenance from Timor, Indonesia (seedlot no. 19489) had the lowest (617 kg m?3), whereas C. equisetifolia from Wagait Tower (North Timor), Indonesia, had the highest (731 kg m?3). Ordinal ranking for the best-performing species/provenances revealed that the best two provenances were C. equisetifolia from Hadsamira Sonkhla, Thailand, and C. junghuhniana from Timor, Indonesia (seedlot no. 19491). The two poorest-performing provenances were C. equisetifolia from Montazah National Park, Egypt, and C. equisetifolia from Cotonou, Benin. The outstanding species/provenances are recommended for pilot planting at Kibaha and similar sites.  相似文献   

8.
Abstract

The present work reports on the main physical and mechanical properties of Pinus leucodermis mature wood, one of the least studied coniferous species in south-east Europe. Pinus leucodermis heartwood specimens were found to have average density values of 0.73 g cm?3 at equilibrium moisture content of 11.5% and average density of 0.64 g cm?3 under oven-dry conditions. The overall tangential shrinkage was 3.4% and the radial shrinkage was 1.9%. The modulus of rupture was on average 77 N mm?2, while the static modulus of elasticity averaged 7087 N mm?2. The hardness of P. leucodermis heartwood using the modified Janka test was 33.4 N mm?2 in the transverse direction and 48.0 N mm?2 in the longitudinal direction, while its compression strength parallel to grain was approximately 41.6 N mm?2.  相似文献   

9.
Abstract

Plantation wood from tropical climate has been introduced rapidly in the national market; however, there is lack of knowledge about the process. The main objective of this study was to investigate the kiln drying behavior of 10 plantation-grown wood species from natural forest in Costa Rica using the recommended drying schedule. Initial moisture content (MCi), final moisture content (MCf), drying rate, drying time, and drying defects were evaluated. The drying schedule applied produced the following results: (1) high MCi (over 110%) in four species and lower values in two species. (2) The largest drying time was found in species with high MCi, and the shortest drying time in species with lower MCi. (3) Significant variations of target MCf were found in some species, despite equalization and conditioning. (4) Exponential relationship MC=a*??t*b was used to establish a moisture content (MC) decrease model, which is not a good indicator of drying time for fives species. (5) High incidence of drying defects was found in Alnus acuminata and Vochysia guatemalensis. According to the above results, it is necessary to test other drying schedule oriented to improve lumber quality and to decrease variability of MC in wood from plantation trees.  相似文献   

10.
ABSTRACT

Information regarding carbon concentration and wood density are lacking in Chilimo dry Afromontane forest.

The aim of this study was to estimate carbon concentration and wood density for Allophyllus abyssinicus, Olea europaea, Olinia rochetiana, Rhus glutinosa, and Scolopia theifolia. A total of 105, 30–50 mm thick wood discs were collected and oven dried at 102°C and 67°C to constant weight, chopped and finally grinded into 0.2 mm with a grinding mill. Carbon concentration was analyzed using the ash method, while wood density was estimated using the water displacement method. The highest carbon concentration (57.12%) was found for O. rochetiana, however, the lowest carbon concentration (56.43%) was found for A. abyssinicus. Stem parts had higher carbon concentration (56.98%) than branch (56.74%) and leave (54.53%) parts. O. europaea exhibited the highest wood density (0.67 g cm?3) value than other species. However, the lowest wood density (0.42 g cm?3) was exhibited for A. abyssinicus. Wood density was also showed a decreasing trend along with increases in stem height and maximum wood density (0.62 g cm?3) was found under stump position, while, the minimum wood density (0.4 g cm?3) was found under tree commercial height.  相似文献   

11.
为合理利用异叶南洋杉人工林木材,通过排水法、质量法和数值法对异叶南洋杉人工林的生材性质展开研究,结果表明,异叶南洋杉人工林木材树皮体积百分率、质量百分率、生材密度、基本密度和生材含水率的平均值分别为11.39%、13.78%、0.842 g/cm3、0.394 g/cm3和121.43%。随异叶南洋杉树高的增加,树皮体积百分率和质量百分率总体呈增大趋势;生材密度和基本密度总体呈下降趋势;生材含水率总体呈先升高后降低的趋势。以期为异叶南洋杉人工林木材的合理利用提供数据支持和理论支撑。  相似文献   

12.
Abstract

Interpretation and tree height measurements in aerial photographs using photogrammetric workstations are frequently performed in standwise forest inventory. Images acquired by digital aerial cameras are now replacing the traditional film-based aerial photographs. In this study, digital images from the airborne Z/I DMC system for standwise estimation of stem volume, tree height and tree species composition were investigated at a 1200 ha forest area located in southern Sweden (58°30′N, 13°40′E). The 56 selected stands were dominated by Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) with stem volume in the range of 30–630 m3 ha?1 (average 300 m3 ha?1) and tree height in the range of 6–28 m (average 20 m). The large-format pansharpened colour infrared images were captured at a flight altitude of 4800 m above ground level corresponding to a pixel size of 0.48 m. The photo-interpretation was conducted by four professional interpreters, independently. In particular, two different base-to-height ratios (i.e. the ratio between the ground distance between image centres at the time of exposure and the flight altitude above ground level) of 0.26 and 0.39 were evaluated, but no significant difference in the estimation accuracy for stem volume and tree height was found. The accuracy for stem volume estimation in terms of relative root mean square error, corrected for systematic errors, was on average 24% (in the range of 17–39%). The corresponding accuracy for tree height estimation was on average 1.4 m (in the range of 0.9–1.6 m). The tree species composition accuracy assessment using a fuzzy set evaluation procedure showed that 95% of the stands were correctly classified. The estimation accuracies are in agreement with previous results using conventional film-based aerial panchromatic photographs.  相似文献   

13.
Abstract

Quantitatively and qualitatively good Scots pine (Pinus sylvestris L.) seed years are rare in northern areas because of the short growing seasons. The seed crop size was studied in four natural pine forests in northern Finland during 1960–2004. Data on seed crop quality were collected during 1986–2004 and quality was determined by X-ray radiography. The long-term average annual seed crop of pine was 77 seeds m?2, varying from 5 to 225 seeds m?2. The expected average annual germination percentage of the seed crop was 61%, varying from 7 to 81%. General linear models were used to analyse the size and quality of the seed crop. Independent variables explained 52% of the variation in annual seed crop quality, and no proper model was found for determining the size of the seed crop; the coefficient of determination was only 5%. A combination of more than 100 seeds m?2 and an expected germination percentage of over 50% was observed once during the years 1986–2004. In most years, natural regeneration in northern Finland is difficult and often limited by the seed crop's quality as well as quantity. These results confirm the importance of seed tree cutting in abundant seed crop years to enable the natural regeneration of pine.  相似文献   

14.
Abstract

This study investigated the relationship between tool wear and some chemical and physical properties for four different Mozambican lesser known tropical species,: Pseudolachnostylis maprounaefolia (ntholo), Sterculia appendiculata (metil), Acacia nigrescens (namuno) and Pericopsis angolensis (muanga). Tool wear is an important aspect for sawmilling and for the woodworking industry. For Mozambique, the utilization of available lesser known wood species will help to increase domestic industry and the economic usage viability of sustainable forest management. A set of experiments was performed on a shaper with a mechanical feed mechanism. Tools of a cemented carbide grade for woodworking were used, and the cutting parameters were fixed. Edge recession and tool wear radius were measured for monitoring tool wear. The wear mechanism was investigated using a scanning electron microscope. The experimental results showed that the chemical properties of the wood species have a great effect on tool wear. Wood silica content was the most important factor affecting tool wear. Wood density and extractives had a low influence on tool wear. The highest tool wear was observed in ntholo, which also had the highest ash and silica contents. A single parameter for evaluation of tool wear was not sufficient to describe the amount of total tool wear.  相似文献   

15.
The exoticSonneratia apetala in Leizhou Peninsula, has shown outstanding fast-growing ability in restored mangrove forests, at the middle and high tide intertidal zone, with year-round fresh water input from drainage. By setting plot and selecting standard tree, investigation and measurement on height growth, diameter growth, biomass, productivity, and so on, were made in aS. apetala plantation at age of six at Lanbel, Fucheng, Leizhou Peninsula in May 2001. The investigating results showed that the mean annual height growth of plantation was 2.03 m and mean annual growth of diameter at breast height (DBH) was 2.35 cm. There exists a significant correlation between the diameter at ground surface (DGS) and DBH. The average biomass of a single standard tree in dry weight was 95.647 kg/m2. A ratio of above-ground biomass to under-ground biomass was 1.60. The stand biomass of unit area was 22.955 kg/m2, singletree wood volume was 88.23 dm3, and the annual wood volume productivity (P A) of the same year was 0.407. The forest energy accumulation was 424.851 MJ/m2, with annual solar energy fixing rate of 40.68×10−7%. It is concluded thatS. apetala species had characteristics of outstanding high biomass accumulation and could be used as coastal planting tree species in southern China. Foundetion item: The paper was supported by the project of integrated mangrove management and coastal protection (IMMCP) in Leizhou Peninsula, Guangdong Province. Biography: Han Wei-dong (1963-), male, associate professor, in Zhanjiang Ocean University, Zhanjiang 524088, Guangdong; and presently as postdoctoral researcher in Life Science College, Xiamen University, Xiamen 361005, Fujian, P.R. China Responsible editor: Zhu Hong.  相似文献   

16.
ABSTRACT

The present study was carried out in a remote area of the Indian Himalayas to assess the biomass use patterns of dhabas (temporary hotels) along an altitudinal gradient in a pilgrimage and tourism affected protected area. The dhaba owners extensively collect fuelwood for various purposes such as cooking, boiling water, and space heating. The study examined factors affecting and resulting from fuelwood usage and collection—including preferred species, gathering patterns, emissions of green house gases due to combustion, and ecological parameters such as density and total basal cover. Open- and close-ended questionnaires were used for interviews with the study subjects. Firewood was reported as the only available energy source in the area. The average fuelwood consumption at three altitudinal sites was 19 kg dhaba?1 day?1 at Site I (1,500–2,000 m asl), 26.62 kg dhaba?1 day?1 at Site II (2,000–2,500 m asl), and 16.74 kg dhaba?1 day?1 at Site III (2,500–3,600 m asl). The five most preferred species for firewood reported by the respondents were: Alnus nepalensis, Lyonia ovalifolia, Quercus floribunda, Pinus roxburghii, and Rhododendron arboreum. The present findings could be used as a baseline for developing various conservation and sustainability measures for protected areas influenced by human populations.  相似文献   

17.
In this work, a set-up with a device measuring the mass of wood packages is examined as an aid to estimate the average moisture content (MC) of wood packages. As the basic density needs to be presumed in the set-up, an estimator of the basic density as a function of log diameter is determined for Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris). In total, 1920 specimens were collected at two different sawmills and analysed for this purpose. Specimens collected at the butt-end of pine had the greatest variation in basic density and it is recommended that they should be omitted when sawmills create their own functions for basic density estimation. Furthermore, the variation in basic density was shown to have the greatest impact on the estimated MC. A maximum error estimator of the MC became 14% at a MC of 70% and 9% at a MC of 10%. It was therefore concluded that the described method should not be used to estimate the MC of packages after drying but can serve as a valuable indicator of average green MC of a drying batch.  相似文献   

18.

A computer-based model for the evaluation of energy use in mechanized wood harvesting systems (EnergyCalc) was developed with aid of life cycle analysis methodologies. The system boundaries were determined "from stump to roadside" with wood volume over bark (m3) as the functional unit. The computer model (based on a database system) used a Visual Basic program, and the energy audit was based on fuel and oil consumption, and the energy consumed in the manufacture of the machines and replacement parts. The general scenario from the literature, results from Sweden and a preliminary study from Ireland are presented. In the overall energy audit of mechanized wood harvesting systems in Ireland, fuel consumption was the most significant item (82%), followed by oils (7%) and machine repairs and replacement (11%). The mean energy use from the data for Ireland was found to be 16% higher than the equivalent in Sweden (120 vs 103 MJ m?3). An energy reduction strategy that has the potential to reduce overall energy consumption for Irish systems by up to 13% was suggested.  相似文献   

19.
Abstract

In this study, two different methods were used to produce thermally modified wood. One was carried out in a typical kiln drying chamber using superheated steam (SS) and the other used pressurized steam in an autoclave cylinder (PS). Overall, both processes followed the same principles and the wood was not treated with any chemicals. Two wood species were studied, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Treatments in the autoclave were carried out under pressure using temperatures of 160°C, 170°C and 180°C. Temperatures of 190°C and 212°C were used in treatments in the chamber at normal air pressure. The colour was measured using L*C*H colour space. Results for both species showed that similar L* (lightness) can be reached at lower (20–30°C) temperatures using PS compared with SS treatment. The hue angle of PS-treated wood was smaller than that of SS-treated wood. No significant difference in C* (chroma) was detected. The difference in E value between PS- and SS-treated wood was smaller for Norway spruce than for Scots pine. The residual moisture content was about 10% higher in wood treated by the PS process compared with the SS process.  相似文献   

20.
Summary A comparison between identically sampled CAT-scan images of five wooden test pieces (Pinus sylvestris) showed that the CT-number in each pixel varied with a standard deviation of ±3.9–11.1 CT numbers. This inaccuracy in CT-numbers is called noise. As long as the direction of rotation can be controlled the noise in CAT-scan images of wood can be assumed to be approx. ±4 CT-numbers in each pixel. A calculation showed the average CT-number must differ ±1 unit to distinguish average CT-numbers in 2 × 2 × 1.5 mm volumes within solid wood. It has previously been shown that a change of ±1 CT-number corresponds approx. to a change in density of ±1 kg/m3. On the other hand, there is a difference in X-ray absorption coefficients between wood and water. Thereby dry wood densities in corresponding volumes must differ approx. ±2 kg/m3 to significantly be distinguished. The corresponding figure is approx. ±6 kg/m3 for wet wood densities with moisture content levels ranging from 6–100%.  相似文献   

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