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Mechanical Characterisation of Densified hardwood with Regard to Structural Applications

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Journal of Renewable Materials 2020年第9期8卷 1091-1109页

作者： Katharina Müller Walter Sonderegger Oliver Kläusler Michael Klippel Edwin Zea Escamilla Institute of Structural Engineering(IBK) Chair of Structural Engineering–Timber StructuresSwiss Federal Institute of Technology ZurichZurich8093Switzerland Swiss Wood Solutions AG 8600 DübendorfSwitzerlandPreviously at Institute for Building Materials(IfB)Chair of Wood Materials ScienceSwiss Federal Institute of Technology ZurichZurich8093Switzerland College of Civil Engineering Nanjing Forestry UniversityNanjing210037China Sustainable Building Center for Corporate Responsibility and SustainabilityUniversity of ZurichZurich8001Switzerland

The demand for high-performance,yet eco-friendly materials is increasing on all scales from small applications in the car industry,instrument or furniture manufacturing to greater dimensions like floorings,balcony furnishings and even *** offers a good choice on all of these scales and can be modified and improved in many different *** this study,two common European hardwood species,Beech(Fagus sylvatica L.)and Ash(Fraxinus excelsior L.)were densified in radial direction by thermo-mechanical treatment and the densified product was investigated in an extensive characterisation series to determine all relevant mechanical *** in the three main directions(longitudinal,tangential,radial)and tension perpendicular to the grain(tangential,radial)were tested and compared to reference specimens with native *** and modulus of elasticity were determined in all *** addition,a Life Cycle Assessment was carried out to evaluate the environmental impact associated to the densification *** experimental investigations showed that strength and stiffness of hardwood in the longitudinal and tangential directions improve significantly by radial densification,whereas some properties in the radial direction *** Life Cycle Assessment showed that artificial wood drying has higher impact than wood ***,the transport distance of the raw material highly influences the environmental impact of the final densified *** paper then also offers an overview of possible applications in structural timber *** hardwood is a viable option as local reinforcement,where high compressive or tensile strength is *** wood densification process offers an alternative to the use of carbon-intense steel components or hardwoods from tropical forests.

关键词： hardwood densification high-performance construction materials thermo-mechanical treatment mechanical characterisation life cycle assessment timber structures

Evidence of Dual Scale Porous Mechanisms During Fluid Migration in hardwood Species (Ⅱ) A Dual Scale Computational Model to Describe the Experimental Results

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Chinese Journal of Chemical Engineering 2004年第6期12卷 783-791页

作者： Patrick PERR LERMAB-UMR INRA/ENGREF/UHP 1093 ENGREF-INRA-14 rue Girardet 54042 Nancy Cedex France

The second part of this paper is devoted to the computational modelling of transient water migration in hardwood. During re-saturation, the moisture content, measured during the process by using X-ray attenuation (see part 1 of this paper), increases quickly very close to the cavity, but requires a very long time for the remaining part of the sample to absorb the moisture in wetting. For this configuration and this material, the macroscopic approach fails. Consequently, a dual-porosity approach is proposed. The computational domain uses a 2-D axisymmetric configuration for which the axial coordinate represents the macroscopic longitudinal direction of the sample whereas the radial coordinate allows the slow migration from each active vessel towards the fibre zone to be considered. The latter is a microscopic space variable. The moisture content field evolution depicts clearly the dual scale mechanisms:a very fast longitudinal migration in the vessel followed by a slow migration from the vessel towards the fibre *** macroscopic moisture content field resulting from this dual scale mechanism is in quite good agreement with the experimental data.

关键词： fluid migration dual-porosity computational model hardwood vessel fibre

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Predicting Stem Windthrow Probability in a Northern hardwood Forest Using a Wind Intensity Bio-Indicator Approach

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Open Journal of Forestry 2012年第2期2卷 77-87页

作者： Philippe Nolet Frédérik Doyon Daniel Bouffard Insitut des Sciences de la Forêt tempérée Ripon Canada

Unlike fire or insect outbreaks, for which a suppression program can be implemented, it is impossible to prevent a windstorm event or stop it while it is occurring. Reducing stand susceptibility to windstorms requires a good understanding of the factors affecting this susceptibility. Distinct species- and size-related differences in stem windthrow susceptibility are difficult to obtain because it is impossible to distinguish their relative effects from those of wind intensity. Using a damage assessment database (60 20-metre radius plots) acquired after an exceptional wind storm in Western Quebec in 2007, we developed an approach in which proportions of windthrown sugar maple poles were used as bio-indicators of wind intensities affecting the plots. We distinguished between single and interactive effects of wind intensity, species, stem size, and local basal area on stem windthrow susceptibility. The best logistic regression model predicting stem windthrow included the wind intensity bio-indicator, species, basal area, and the species by diameter at breast height (DBH, 1.3 m) interaction. Stem windthrow probability generally increased with DBH and decreased with basal area. Species wind-firmness was ordered as: yellow birch > sugar maple = eastern hemlock = American beech > ironwood > basswood = other hardwoods = other softwoods. Our method remained an indirect method of measuring wind intensity and its real test would require a comparison with anemometer measurements during a windstorm. Despite its indirect nature, the method is both simple and ecologically sound. Hence, it opens the door to conducting similar windthrow studies in other ecosystems.

关键词： Windthrow Prediction Species Wind-Firmness Tolerant hardwood Forests Silviculture Guidelines

Effects of Whole-Tree Harvesting on Species Composition of Tree and Understory Communities in a Northern hardwood Forest

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Open Journal of Forestry 2015年第2期5卷 235-253页

作者： Gabriel E. Roxby Theodore E. Howard Thomas D. Lee Society for the Protection of New Hampshire Forests Concord NH USA Formerly Graduate Research Assistant University of New Hampshire Durham NH USA Department of Natural Resources and the Environment University of New Hampshire James Hall Durham NH USA

In the northeastern United States, whole-tree harvesting is widely used to supply fuel to biomass energy facilities, but questions remain regarding its long-term sustainability. We have previously reported findings indicating no short-term decrease in forest productivity in whole-tree harvested sites when compared with similar conventionally (stem-only) harvested sites. Here we present additional results of the same study, but focus on the effect harvest treatment has on the species composition of the regenerating forest. Within northern hardwood forests in central New Hampshire and western Maine, regeneration surveys were conducted on four (4) small clearcuts in 2010 and twenty-nine (29) small clearcuts in 2011. The species and diameter of trees > 2 m in height were recorded within 1 m or 2 m-radius plots and used to calculate the biomass fraction of each species. The 2010 study additionally measured the density of trees 2 m in height and the diversity of understory non-tree species. Non-metric multidimensional scaling and multi-response permutation procedures were used to determine the effect of harvest treatment had on community-wide tree species composition. Potential differences were also examined on a species-by-species basis. Both analytic methods indicated no significant differences in species composition of tree species or understory communities. Within the limits of our data, we conclude that no significant effects of residue removal on species composition are observed within our sample of northern hardwood sites at this early stage of stand development.

关键词： Whole-Tree Harvesting Regeneration Species Composition Residue Removal Northern hardwood Forest Non-Metric Multidimensional Scaling Multi-Response Permutation Procedures

Study on hardwood Cutting Propagation Technology of Fraxinus

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Agricultural Science & Technology 2017年第3期18卷 526-530页

作者：姚俊修李善文刘元铅李自成李庆华吴德军山东省林业科学研究院山东济南250014 山东省林木遗传改良重点实验室山东济南250014

[Objective] Hard-branch cutting propagation technology of Fraxinus was studied under different environmental conditions. [Method] An orthogonal test was designed based on 1-year-old clones of F. pennsylvanica Marsh Lula 5. Under dif- ferent growth hormones, hormone concentrations and processing time, F. velutina Lula 2 and F. pennsy/vanica Marsh Yuanla 2 were treated by vacuum pump for 10 min, [Result] The decreasing order of cutting survival rates of Lula 5 under different etnvironments was small plastic flowerpot （94.4%）, nutrition cup （92.8%）, sand tray （56.1%）, and cuffings treated with 100 mg/L ABT, for 2 h, 200 mg/L ABT, for 4 h and 100 mg/L IBA for 6 h under large nutrition cup environment grew the best, showing a survival rate of 100%. Lula 2 and Yuanla 2 were subjected to vacuum pump treatment, the survival rate of cuttings under the sand tray environment was averagely 29%; and under the large plastic flowerpot environment, the survival rate of cuttings was averagaly 64.4%, and cuttings of Lula 2 treated with vacuum pump for 10 min in 200 mg/L ABTI showed a survival rate up to 95%, which was the highest among all treatments. It could be seen that whether cuttings were treated with vacuum pump, the survival rate of cuttings in sand tray was lower than those under other environments, while there was no big difference in survival rate of cut- tings between the nutrition cup and plastic flowerpot environments. [Conclusion] This study is of great significance to improvement of cutting propagation coefficient.

关键词： Fraxinus hardwood Hormone Cutting propagation

Selection of Media for hardwood Cuttings Container Seedling-raising of Triploid Clones of Populus tomentosa

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Agricultural Science & Technology 2008年第6期9卷 104-107页

作者：张平冬王红静宋金利康向阳朱之悌北京林业大学生物科学与技术学院北京100083 山东太阳纸业股份有限公司山东兖州272100

[Objective] The experiment was aimed to select effective and economical media for container seedling of triploid clones of Populus tomentosa that was carried out. [Method] The sandy loam, peat, perlite, vermiculite, riversand, sludge were taken as media of hardwood cutting and survival rate, seedling height were taken as indexes to select media for container seedling of triploid clones of Populus tomentosa. [Result] Different mixedmedia had great influence on survival rates of container seedlings. Taking peat and vermiculite with the proportion of 5∶2 (M10) or peat ,vermiculite with the proportion of 7∶2 (M11) or sandy loam (M1) as media would generate higher cutting survival rate that was higher than 90.0%. There were significant differece in height increments of container seedlings. Taking sandy loam, peat and vermiculite with the proportion of 6∶2∶2(M5)or sandy loam (M1), seedling height of 60-days the seedling was over 37.0 cm. [Conclusion] According to cost analysis of nursery medium, the optimum medium for hardwood cuttings container seedling-raising of triploid clones of Populus tomentosa was sandy loam.

关键词： Triploid clones of Populus tomentosa hardwood cutting Container seedling-raising Medium

Behavior of wood basic density according to environmental variables

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Journal of Forestry Research 2022年第2期33卷 497-505页

作者： Gabriel Marcos Vieira Oliveira JoséMárcio de Mello Carlos Rogério de Mello JoséRoberto Soares Scolforo Eder Pereira Miguel Thiago Campos Monteiro Brazil Institute of Agricultural and Forestry Defense of Espírito Santo(IDAF) Av.Lourival Lugon Moulinnº300CentroJerônimo MonteiroES CEP:29.550-000Brazil Department of Forestry Sciences Universidade Federal de Lavras-UFLACaixa Postal 3037LavrasMG CEP:37.200-000Brazil Engineering Department Universidade Federal de Lavras-UFLACaixa Postal 3037LavrasMG CEP:37.200-000Brazil Forestry Engineering Department Faculdade de TecnologiaUniversity of Brasilia-UnBCampus Universitário Darcy RibeiroCaixa Postal 4357Asa Norte-BrasíliaDF CEP:70910-900Brazil Department of Forestry Engineering and Technology Universidade Federal do Paraná-UFPRAv.Pref.Lothário Meissner632Jardim BotânicoCuritibaPR CEP:80.210-170Brazil

The relationships between climate conditions and wood density in tropical forests are still poorly *** quantify spatial dependence of wood density in the state of Minas Gerais(MG,Brazil),map spatial distribution of density,and correlate density with climate variables,we extracted data from the Forest Inventory of Minas Gerais for 1988 trees scaled throughout the territory and measured wood density of discs removed from the *** variables were extracted from the database of the Ecological-Economic Zoning of Minas *** spatial analysis,tree densities were measured at 44 georeferenced sampling *** data were subjected to exploratory analysis,variography,cross-validation,model selection,and ordinary *** relationships between wood density and environmental variables were calculated using dispersion matrices,linear correlation,and *** density proved to be highly spatially dependent,reaching a correlation of 96%,and was highly continuous over a distance of 228 *** distribution of wood density followed a continuous gradient of 514-659 kg m^(−3),enabling corre-lation with environment *** was correlated with mean annual precipitation(−0.57),temperature(0.63),and evapotranspiration(0.83).Geostatistical methods proved useful in predicting wood density in native tropical forests with different climate *** results confirmed the sensitivity of wood density to climate change,which could affect future carbon stock in forests.

关键词： Biomass Climate variables Geostatistics hardwood Forest inventory Minas Gerais

Herbaceous-Layer Community Dynamics along a Harvest-Intensity Gradient after 50 Years of Consistent Management

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Open Journal of Forestry 2012年第3期2卷 97-109页

作者： Marcella A. Campione Linda M. Nagel Christopher R. Webster School of Forest Resources and Environmental Science Ecosystem Science Center Michigan Technological University Houghton USA

In 1958, a demonstrational cutting trial totaling 22.2 ha was established in a northern hardwood forest in Alberta, MI. Eight different treatments were installed, including four diameter-limit treatments (56 cm, 41 cm, 30 cm, and 13 cm), three single-tree selection treatments with residual basal areas of 21 m2·ha–1, 16 m2·ha–1, and 11 m2·ha–1, and an uncut control. Within each treatment, a 0.4-ha permanent plot was established and subdivided into 0.04-ha square subplots. Harvests have been implemented every ten years with the most recent harvest occurring during the winter of 2008 - 2009. We quantified ground layer vegetation response before and after the most recent harvest. Nonmetric multidimensional scaling (NMS) ordination showed a very distinct separation between the most intensive management treatment (13-cm diameter-limit treatment) and the uncut control. Compositionally, the diameter-limit treatments moved with greater directionality and magnitude towards the 13-cm diameter-limit treatment following harvest, while compositional change in the residual basal area treatments was less pronounced and lacked strong directionality. Herbaceous species percent cover generally decreased with increasing residual overstory basal area across treatments. Weedy and early successional species were most abundant under lower residual basal area and diameter-limit treatments. Results based on 50 years of continuous management suggest that diameter-limit harvests likely have a greater impact on the herbaceous community than single-tree selection or no management.

关键词： Northern hardwood Forests Uneven-Aged Management NMS Ordination Understory Diversity Diameter-Limit Single-Tree Selection