Genotypic variation in wood density and growth traits of poplar hybrids at four clonal trials

Wood density is considered as one of the most important wood properties which affects the properties and value of both fibrous and solid wood products. The present study was intended for evaluating the possibilities of improving wood quality and growth of poplar hybrids. Wood density components of individual growth rings (minimum and maximum wood density, average ring density) and growth traits (tree height, dbh, stem volume) were measured in four 10- and 12-year-old clonal trials of four poplar hybrids, Populus deltoides × P. nigra, P. trichocarpa × P. deltoides, P. maximowiczii × P. balsamifera, and P. balsamifera × P. nigra, as well as P. deltoides. Wood density components of individual growth rings were obtained from microdensitometeric profiles measured with a direct reading X-ray densitometer. Site had a moderately significant effect on wood density and a highly significant effect on tree growth. The hybrid effect was highly significant (P < 0.001) for most traits. Minimum, maximum and weighted wood densities were found to be under strong genetic control, with clonal repeatabilities varying between 0.45 and 0.81. The coefficient of genotypic variation (CV_G) for wood density at individual sites ranged from 4.0 to 6.8%, whereas CV_G for dry fiber weight (mass) reached 32.8% with repeatabilities of up to 0.67. A small but significant (P = 0.028) hybrid × environment interaction was found for dry fiber weight. The highest ecological sensitivity was found for P. deltoides × P. nigra, with ecovalence reaching 32.3%. Clonal × environment interaction was significant for weighted, average, and minimum wood density. Significant negative genotypic correlations between stem volume and wood density ranged from −0.39 to −0.74. One possible strategy in tree breeding would be to maximize wood fiber production through selection for dry fiber weight.     

Acoustic evaluation of loblolly pine tree- and lumber-length logs allows for segregation of lumber modulus of elasticity,not for modulus of rupture

Key message

Loblolly pine ( Pinus taeda ) logs can be evaluated using acoustic velocity whereby threshold acoustic velocity values can be set to ensure lumber meets specified mechanical property design values for modulus of elasticity.

Context

There is a need to better sort logs according to lumber quality for improved decision making and wood utilization because merchantable logs are being harvested from different stand types including natural forests, conventional plantations, and intensively managed plantations, all with differences in rotation ages, growth rates, and wood quality traits.

Aims

This study aimed to link tree- and lumber-length log acoustic velocity with the resulting lumber properties as tested in static bending from five intensively managed loblolly pine stands in the Atlantic Coastal Plain of Georgia.

Methods

Acoustic velocity was measured using the resonance-based approach on 87 tree-length logs and 244 lumber-length logs. The logs were then processed into 797 pieces of 38 mm by 89 mm (2×4), 140 mm (2×6), 184 mm (2×8), and 235 mm (2×10) dimension lumber, dried, and tested in static bending.

Results

Mean MOE of the lumber had moderate relationships with acoustic velocity of the logs (R ² = 0.49) whereas MOR and acoustic velocity did not have a strong relationship (R ² = 0.20). Accounting for log position increased the performance of the mean lumber MOE model (R ² = 0.62) which was further increased by adding green density and small-end diameter (R ² = 0.67). Utilization of acoustics was effective for segregating logs based on lumber modulus of elasticity and did not depend on knowing tree or stand information such as age, site quality, and silviculture history.

Conclusion

Acoustic velocity evaluation of tree- and lumber-length logs could be employed to segregate logs within the supply chain to ensure that lumber would meet specified design values.

     

Influence of Initial Spacing on Growth and Branching Characteristics of Cordia africana Trees Established on Eritrean Highland

The study reports on the influence of initial spacing on growth and branching habit of Cordia africana trees established on Eritrean highland. The initial spacings used in this study were 1.0×1.0 m, 1.5×1.5 m, 2.0×2.0 m, 2.5×2.5 m, 3.0×3.0 m, and 3.5×3.5 m; these are equivalent to 1 m², 2.25 m², 4 m², 6.25 m², 9 m² and 12.25 m² in growing space per tree, respectively. No significant relationship between spacing and tree height was found, but increased spacing increased crown diameter and root-collar-diameter. On the other hand, an increase in spacing reduced wood quality because it increased branch diameter (knot size). Thus, from a wood quality perspective, adopting close spacing in plantations of C. africana could be advantageous.     

Hybrid poplar (Populus spp.) adaptation to a semi-arid region: results from Northwest New Mexico (2002–2011)

A provenance test was initiated in spring 2002 at the New Mexico State University Agricultural Science Center at Farmington to examine the adaptability of various hybrid poplar (Populus spp.) crosses to the high elevation, semi-arid conditions of this region of the Southwestern United States. Ten crosses of P. deltoides, P. maximowiczii, P. nigra and P. trichocarpa obtained from nurseries in the Pacific Northwest were grown in replicates (3 plots × 16 trees) under drip irrigation programmed to match tree evapotranspiration (ET) rates. By the end of year 10, six crosses had maintained a 90 % or higher survival rate and had an average wood volume of 246 m³ ha^?1. The P. deltoides × P. nigra (P. × canadensis) clone OP-367 surpassed a ten-year commercial target of 25-cm diameter at breast height (DBH) after eight seasons, and by the end of 2011 attained a DBH of 28.0 cm, height of 19.9 m and wood volume of 473 m³ ha^?1. Results suggest that hybrid poplar production is possible in this type of semi-arid environment using appropriate germplasm and drip irrigation regimes scheduled according to tree ET demand.     

Density measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning

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.     

Phenological differences in tree water use and the timing of tropical forest inventories: conclusions from patterns of dry season diameter change

Interspecific variation in water-induced fluctuations in stem girth demonstrates the mechanisms promoting coexistence in seasonally dry tropical forest. In addition, these fluctuations are a potential, but unevaluated, source of bias in measurements of annual tree growth rates. To examine diurnal and seasonal patterns of stem diameter change, tree girth was measured over 2 years (1997–1999), using dendrometer bands, for three species (Celtis mildbraedii, C. zenkeri and Strombosia glaucescens) in semi-deciduous forest in Ghana. Soil matric potential was measured concurrently at 15 cm depth. In addition, measurements of all trees >20 cm dbh on three, 1 ha plots were made at the beginning and middle of the 1998/1999 dry season. During the severe 1997/1998 dry season, soil matric potential declined below −1.5 MPa and two species showed significant stem shrinkage. For the evergreen species, C. mildbraedii, there was a significant positive effect of tree diameter on stem shrinkage, and shrinkage was greater in the second, compared to the first, half of the dry season. For the deciduous species, C. zenkeri, shrinkage was reduced during the second half of the dry season, following leaf fall. During 1998/1999, soil matric potential, did not decline below −1.5 MPa, and rates of girth change remained positive for all species. There were no significant effects of size or phenology on the rate of girth change in the plot-based study. Deviations in annual increment calculated over successive monthly intervals indicate that a 10-fold difference in soil water availability between measurement occasions can lead to a 4% bias in estimates of annual growth. Measurements of forest plots should be made when inter-annual variation in soil water availability is low. In this forest, measurements should, therefore, be made during the wet season, contrary to published recommendations.     

Hygienic acceptance of wood in food industry

Food is physically manipulated by other materials during production processes, and therefore, food quality and safety are vital in processes where foods are in contact with various materials. Wooden frames were used for centuries for dried egg pasta trays; however, with the development of different materials, wood was slowly abandoned and replaced by plastic. Nevertheless, there are some hygienic considerations concerning plastic frames in the dried egg pasta making industry. In this study, plastic and wooden trays were analysed by swabbing (n?=?210) and evaluated in regard to total number of aerobic counts (TAC), Enterobacteriaceae, Escherichia coli, moulds, yeasts and Staphylococcus aureus using dry medium plates. The aims of the research were to (1) evaluate the total number of microorganisms on wood and plastic material used for pasta trays and (2) make a hygienic evaluation of analysed materials for application in the pasta industry. The research was aimed to answer the question, ‘Does the tray material and/or location of the swab sample influence the colony forming unit (CFU)/20?cm²?’ Results showed a statistical difference in CFU/20?cm² for all bacterial determinations, except for E. coli which was not detected in swabs taken from wooden or plastic trays. This hygiene evaluation study supported the conclusion that the use of wood is appropriate in the food industry from a hygienic and technological point of view.     

Simulation of the yield of knot-free components from Scots pine (Pinus sylvestris L.): A comparative study of star-sawing and square-sawing

Abstract

The production of knot-free wood is important since the market demands wood without knots for reasons of both appearance and material properties. This work describes a simulation of the removal of knots from star-sawn and square-sawn timber. The efficiency of the two methods is compared in terms of the length of the knot-free components obtained and the volume yield. The simulation was based on data for trees and logs taken from the Swedish Stem Bank. These data were then used to simulate the sawmill process in a computer program called the Virtual Sawmill. Data related to the boards obtained were used in a MATLAB model simulating the cross-cutting of knots. Simulated star-sawing of logs with a top diameter exceeding 230 mm gave a mean knot-free component length of 417±321 mm, while the mean length of knot-free components for simulated square-sawing of the same logs was 298±122 mm. The volume yield of knot-free components from the two sawing patterns was 91% for star-sawing and 87% for square-sawing. For timber with cross-section dimensions of 38×75 mm², the mean length and yield of knot-free components from simulated star-sawing were 451±349 mm and 90%, respectively. In simulated square-sawing, the corresponding values were 263±197 mm and 82%, respectively. This shows that star-sawing has potential for the production of knot-free timber.     

Antifungal activity of essential oils isolated from Egyptian plants against wood decay fungi

The essential oils of eighteen Egyptian plants were extracted by hydrodistillation and their chemical compositions were analyzed by GC-MS. The antifungal activity of the isolated oils was evaluated against two wood decay fungi Hexagonia apiaria and Ganoderma lucidum in vitro. The essential oil of Artemisia monosperma showed the highest inhibitory effect against H. apiaria (EC₅₀ = 31 mg L^?1) and G. lucidum (EC₅₀ = 53 mg L^?1). The results of in vitro tests indicated that the essential oils of Cupressus sempervirens, Citrus limon, Thuja occidentalis, Schinus molle, A. monosperma and Pelargonium graveolens were the most potent inhibitors against both fungi. These six oils caused significant reduction of wood mass loss of Scots pine sapwood after 6 weeks of fungal exposure. The oil of C. limon revealed the highest reduction of wood mass loss caused by H. apiaria, while A. monosperma oil displayed the highest reduction of wood loss caused by G. lucidum. These results support the potential use of essential oils for wood protection against decay fungi.     

Biomass conversion factors (density and carbon concentration) by decay classes for dead wood of Pinus sylvestris, Picea abies and Betula spp. in boreal forests of Sweden

For estimating the amount of carbon (C) in dead wood, conversion factors from raw volume per decay class to dry weight were developed using three different classification systems for the species Norway spruce (Picea abies L. Karst), Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth and B. pubescens Ehrh) in Sweden. Also the C concentration in dead wood (dry weight) was studied. About 2500 discs were collected from logs in managed forests located on 289 temporary National Forest Inventory (NFI) sample plots and in 11 strips located in preserved forests. The conversion factors were based on an extensive data compilation with a wide representation of different site-, stand-, species- and dead wood properties and were assumed to represent the population of fallen dead wood in Sweden. The density decreased significantly by decay class and the range in density for decay classes was widest for the NFI decay classification system, suggesting this to be the most suitable. The C concentration in dead wood biomass increased with increasing decay class and in average Norway spruce (P. abies) showed a lower C concentration than Scots pine (P. sylvestris). The average dead wood C store of Swedish forests was estimated to 0.85 Mg C/ha.     

Effect of tree spacing on growth and wood density of 38-year-old Cariniana legalis trees in Brazil

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.     

Stem modeling and simulation of conversion of cork oak stems for quality wood products

Recent research is underway to study cork oak (Quercus suber L.) wood potential for production of wood components. A total of 35 stems of young and mature cork oaks were sampled, live sawn into flitches, scanned using VTT’s WoodCIM^®, and the measured data computed by VTT’s PuuPilot software, allowing stem 3D reconstruction. Sawing simulations were run for 0.5 m and 1 m logs and the whole stem. Sawn products were (1) planks, (2) parquet, (3) lamparquet, and (4) external component of multilayer planks. Cork oak stems showed a moderate to small taper (mean 24 mm/m). Curviness varied between straight to significantly crooked stems (mean value 40 mm) Batch yields for the tested products ranged 25–43% and 37–50% for 0.5 m logs of young and mature trees, respectively; for 1 m logs, batch yields ranged 19–41% and 25–54%. When using the whole stem, batch yields were lower, ranging 11–38% and 15–50%. Higher yields were obtained for all log lengths and samples for production of lamparquet, parquet, and multilayer component.     

Stress-wave velocity of trees and dynamic Young’s modulus of logs of 4-year-old Eucalyptus camaldulensis trees selected for pulpwood production in Thailand

Eucalyptus camaldulensis Dehnh. is extensively planted in Thailand to produce wood chips used as raw material for pulp and paper. To promote the utilization of the wood from plantation-grown E. camaldulensis for solid lumber, stress-wave velocity of trees and dynamic Young’s modulus of logs were investigated for 4-year-old trees of eight half-sib families selected for pulpwood production on the basis of the growth characteristics in the previous tree breeding program. For the eight families, the mean stem diameter at 1.3 m above ground level and mean tree height were 7.6 cm and 11.9 m, respectively. The mean stress-wave velocity of eight families was 3.45 km/s. Dynamic Young’s modulus of logs ranged from 7.88 to 17.64 GPa, and the mean value for the eight families was 11.72 GPa. Stress-wave velocity of trees was significantly correlated with dynamic Young’s modulus of logs, suggesting that dynamic Young’s modulus of wood can be evaluated nondestructively by stress-wave velocity of trees. Significant differences in stress-wave velocity and dynamic Young’s modulus of logs were obtained among families. Thus, to promote the utilization of E. camaldulensis wood for solid lumber production, selection of trees with high Young’s modulus should be applied to trees already selected for the growth characteristics in the previous tree breeding program.     

Influence of temperature and steam environment on set recovery of compressive deformation of wood

Low-density hybrid poplar wood (Populus deltoides?×?Populus trichocarpa) was densified by mechanical compression under saturated steam, superheated steam, and transient conditions at temperature levels of 150, 160, and 170°C. Furthermore, compression of wood under saturated steam conditions at 170°C, followed by post-heat-treatment at 200°C for 1, 2, and 3?min, was performed. To determine the influence of compression treatment on the set recovery, specimens were subjected to five cycles of water soaking and drying. Modulus of rupture (MOR) and modulus of elasticity (MOE) of specimens compressed under saturated steam conditions at 170°C and post-heat-treated at 200°C were determined in the dry condition and after five soak/dry cycles. Higher temperature of the compression treatment resulted in lower equilibrium moisture content, while the steam conditions during the treatment and the post-heat-treatment did not have significant effect. Furthermore, the highest degree of densification was obtained in specimens compressed under saturated steam conditions at 170°C and post-heat-treated at 200°C. The steam condition and temperature influenced the set recovery of compressive deformation. Reduced hygroscopicity does not necessarily imply reduced set recovery. The results established that considerable fixation of compressive deformation can be obtained by compressing the wood in a saturated steam environment and by post-heat-treatment at 200°C. The short heat-treatment had no influence on MOR or MOE, but soaking/drying treatments caused a decrease in the MOR and MOE.     

Recovery rate and quality of rotary peeled veneer from 30-year-old Pinus taeda L. logs

??Context

In the construction sector, wood is facing competition with other materials such as concrete, steel or plastics. Therefore, there is a need for more efficiency in the forest–wood chain by improving silvicutural management and wood processing technologies.

??Aims

The objective of the study is to analyse the influence of log diameter and quality to recovery rate, veneer quality and economic benefit.

??Methods

The trees used in the study came from a 30-year-old Pinus taeda L. thinning trial in Southern Brazil. In total, 57 logs (20.7 to 67.0 cm) were peeled following the standard industrial processing methods of the plywood mill.

??Results

Average recovery rate was 54 % ranging from 35 to 72.6 %, with a linear trend (R ²?=?0.48) of increasing recovery with an increment on the log small-end diameter. Results show that the gap between theoretically possible and real recovery was lower in the logs with bigger diameters, indicating their higher efficiency in industrial processing. Moreover, the economic analysis detected that the current prices for log assortments reflect only the industrial potential of low-quality pruned logs. An optimised pruning strategy would result in higher industrial efficiency, which would allow higher log prices.

??Conclusion

The results indicate that the recovery rate of bigger logs is higher in terms of volume of peeled veneer. The quality and therefore the value obtained from each log were negatively influenced by inadequate pruning strategies. Management of pines for higher value utilisation requires optimized thinning and pruning strategies in order to meet high growth rates and proportionally bigger dimensions of clear wood.     

The effects of chemical components and particle size on the mechanical properties of binderless boards made from oak (<Emphasis Type="Italic">Quercus</Emphasis> spp.) logs degraded by shiitake fungi <Emphasis Type="Italic">(Lentinula edodes</Emphasis>)

Binderless boards are composite boards that rely on self-bonding mechanisms for inter-fibre bonding. Quercus acutissima and Quercus serrata logs degraded by Lentinula edodes (shiitake fungi) were used in this study to investigate whether physical and chemical changes induced by shiitake fungi can enhance board mechanical properties. Binderless boards were manufactured with 0.8 g/cm³ target density, 220 °C pressing temperature, 5 MPa pressure, and pressing duration of 10 min. Boards made from logs degraded for ≥?26 months were stronger than control boards and met modulus of rupture (MOR) and internal bonding (IB) requirements for fibreboards. Chemical composition and particle size distribution of the wood powder used to make the boards were determined to elucidate the drivers of board mechanical properties. The proportion of small particles (<?150 µm) showed a strong positive correlation with MOR for both species and hot water extractives showed a strong positive correlation with IB for Q. acutissima boards. Introduction of shiitake fungi pre-treatment to the production process may enhance the mechanical strength of binderless boards.     

Modulus of elasticity in scarf-jointed wooden beams: a case study with polyvinyl acetate and isocyanate adhesives

In the present study, elastic properties of scarf-jointed oak (Quercus castaneifolia) timbers with the application of two different types of adhesives (polyvinyl acetate and isocyanate) were evaluated using free flexural vibration of free–free beam method in different flexural directions of vibration, i.e., tangential and redial directions. Samples were taken from trees of Hyrcanian forests in Iran with nominal dimensions of 20 × 20 × 360 mm³. Comparing the results of elastic properties of clear oak wood beams with scarf-jointed samples wood showed that scarf joints with the bonding angles of 70° and 75°, covered by polyvinyl acetate adhesive, did not demonstrate any significant effect on modules of elasticity. Scarf-jointed beams with smaller joint angles (60° and 65°) were considerably weaker or totally unreliable in their moduli of elasticity. It is also shown that the magnitude of effect gets worst by using isocyanate rather than polyvinyl acetate adhesive.     

Timber Demand and Supply in Northwest Vietnam: The Roles of Natural Forests and Planted Trees

Households and wood processing businesses in the provinces of Son La, Dien Bien and Lai Chau in the Northwest of Vietnam were surveyed to determine patterns of local wood demand and supply, changes in species utilized over time, and whether timber from planted trees might substitute for species previously harvested from local natural forests. In each province, 5–6 sawmills and 4–6 villages representing 3 main ethnic groups were selected for investigation. Managers of selected sawmills and 3–4 randomly selected households in each village were interviewed using semi-structured questionnaires. There was high and uniform household demand for fuelwood in the surveyed villages, making fuelwood the dominant use, in terms of wood volume. Use of sawn timber for furniture, home repair and construction consumed less wood but required logs of acceptable species. Sawmills surveyed were small, with input capacity ranging from <15 to 500 m³ of logs per year, suggesting a total log requirement of about 30,000 m³/year for the 192 known wood processing businesses in the three provinces. Most sawmills still used wood from natural forests, sourced locally or imported from Laos. A trend of switching from prized timber species from natural forests, now effectively unavailable, to alternatives from natural and planted forests was reported by both sawmills and households. Some planted species grown on short-medium rotations appear able to substitute for local sawn timber requirements.     

Variation in carbon concentration and wood density for five most commonly grown native tree species in central highlands of Ethiopia: The case of Chilimo dry Afromontane forest

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.     

Variation in wood density and carbon content of tropical plantation tree species from Ghana

Most research on carbon content of trees has focused on temperate species, with less information existing for tropical trees and very little for tropical plantations. This study investigated factors affecting the carbon content of nineteen tropical plantation tree species of ages seven to twelve and compared carbon content of Khaya species from two ecozones in Ghana. For all sample trees, volume of the main stem, wood density, wood carbon (C) concentration and C content were determined. Estimated stem volume for the 12-year-old trees varied widely among species, from 0.01 to 1.04 m³, with main stem C content ranging from 3 to 205 kg. Wood density among species varied from 0.27 to 0.76 g cm^?3, with faster growing species exhibiting lower density. Significant differences in wood density also occurred with position along the main stem. Carbon concentration also differed among tree species, ranging from 458 to 498 g kg^?1. Differences among species in main stem C content largely reflected differences among species in estimated main stem volume, with values modified somewhat by wood density and C concentration. The use of species-specific wood density values was more important for ensuring accurate conversion of estimated stem volumes to C content than was the use of species-specific C concentrations. Significant differences in wood density did exist between Khaya species from the wet and moist semi-deciduous ecozones, suggesting climatic and site factors may also need to be considered. Wood densities for these plantation grown trees were lower than literature values reported for the same species in natural forests, suggesting that the application of data derived from natural forests could result in overestimation of the biomass and C content of trees of the same species grown in plantations.