Time dependence of Poisson’s effect in wood I: the lateral strain behavior

To understand the viscoelasticity of wood three dimensionally, a longitudinal tensile creep test for 12 species was conducted to examine the changes with time in the lateral strain and the viscoelastic, i.e., apparent Poisson’s ratio. The changes in the lateral strain (ɛ _T and ɛ _R) were similar to those in the longitudinal strain (ɛ _L). That is, during creep, the absolute value of lateral strain continued to increase with the gradual reduction in the increase rate; immediately after the removal of the load, it recovered abruptly; then, it recovered slowly and finally reached a certain value. The rate of increase in the longitudinal strain during creep was smaller than that in the absolute value of lateral strains. The apparent Poisson’s ratio became large during creep because the lateral strain increased more than the longitudinal strain. The analysis of lateral strain by decomposition into three components, that is, instantaneous strain, delayed elastic strain, and permanent strain, has revealed that the lateral permanent strain in the transverse direction contributes most to the increase in the apparent Poisson’s ratio during creep.     

Effect of fatigue and annual rings’ orientation on mechanical properties of wood under cross-grain uniaxial compression

The mechanics of fresh wood with and without a fatigue pre-treatment that mimics a mechanical pulping process was experimentally studied. The mechanical properties of Norway spruce samples under compression are considered with the macroscopic stress–strain data and from local strain properties via digital image correlation technique. The results highlight the effects of the orientation of the wood annual rings compared to the loading direction and of the pre-fatigue. The wood presents a low yield point when the annual rings are tilted compared to the load axis, but the Young’s modulus and yield stress are higher when the annual rings are either parallel or perpendicular to the load direction. In the last case, buckling of softest layers occurs. The fatigue treatment makes the wood less stiff as deduced from the decreases of Young’s modulus and yield stress, whatever the orientation of annual rings. Secondly, it creates a thin and localized softened layer.     

Relationship between stomatal behavior and characteristics of photosynthesis and transpiration of Adenophora lobophylla and A. potaninii at different altitudes

IntroductionAdenOPhoraIObOPhytheandAdOnoPhorapot8niniiareperennialherbunderthejurisdictionofAd8no-phoraofCampanuIaceae.A.IObOPhyIfapopulationdistributesinthenorthwestareaofJinchuanCounty,innorthwestSichuanProvince,ataItitudesfrom2ooomto34oom,andthedistributionareaises-timatedIess5ookm2.A.pot8niniipopuIationisanextensivespecieswhichdistributesnotonIyinthenorthwestareaofSichuanProvincebutalsoinQinghai,Gansu,Shanxi,NingxiaandShanxi.Inre-centyears,thestudiesonendangeredmechanismforA.…     

Behavior of piezoelectric, dielectric, and elastic constants of wood during about 40 repeated measurements between 100°C and 220°C

This study investigated the behavior of piezoelectric, dielectric, and elastic constants and the crystallinity in wood cellulose by repeated measurements (n = 42) between 100°C and 220°C. There was an insignificant change in the piezoelectric constant during repeated measurements in this temperature range. On the other hand, thermal decomposition of the amorphous region contributed to the decreasing trend of dielectric and elastic constants, although only a small increase in the elastic constant was found at the time of the initial measurements. The increase in the repeated measurements in this temperature range resulted in an increase in the piezoelectric loss modulus constantd ₂₅, which is closely related to energy loss. Thed ₂₅ peak shifted to a higher temperature with increasing measurements, which might be due not to the increase in rigidity of the wood specimen but to the increase in total peak area, which was observed during the later measurements. At the same time, variations of piezoelectric loss modulusd ₂₅ ande ₂₅ at advanced stages of the measurements suggested damage and structural changes in the wood.     

Relationship between the stoichiometric characteristics and leaf functional traits of Castanopsis hystrix in different ages

Both the stoichiometric characteristics and leaf functional traits can reflect the adaptability of plants to changes in the external living environment. In particular, for varying aged forest plants, the study of stoichiometric characteristics and leaf functional traits can reflect the plant’s life history strategy and its resource investment and allocation methods. In this paper, the 1.5-year-old, 5-year-old, 15-year-old and 20-year-old Casta -nopsis hystrix were selected as the research objects to investigate the trends of stoichiometry and leaf functional traits, and their synergistic changes were verified. The results showed that with the increase of age, the stability of C. hystrix stoichiometry gradually increased, and the functional traits also tended to invest in security. However, there was no synergistic change between the two, which might be attributed to the different sensitivity of the C. hystrix leaf to the environment at the life history level of 1.5-year-old to 20-year-old.     

Biological performance,water absorption,and swelling of wood treated with nano-particles combined with the application of Paraloid B72~

We evaluated fungal decay and mold resistance,leaching, and water absorption of nano-compounds and Paraloid B72~(PB72) in treated wood specimens to develop new methods of consolidation by combining nanoparticles and consolidants. Scots pine wood specimens were treated with dispersions of nano-Cu O, nano-Zn O,nano-B_2O_3, nano-Ti O_2, and nano-Ce O_2. PB72 treatments of nano-particle-treated wood specimens were then carried out by either vacuum or immersion for 24 h. Previously,decayed wood specimens were also consolidated with the nano-compounds and PB72. PB72 treatments reduced element release from treated wood specimens. Nearly all nano-compounds ? PB72 treatments increased the biological performance of treated wood specimens against decay fungi tested. PB72-only treated wood specimens had the highest weight losses in decay tests. No improvements were obtained in mold resistance tests when the nanocompounds and PB72 were combined. In nano-compoundonly treatments, unleached specimens showed slightly lower water absorption values compared to untreated control specimens. Incorporation of PB72 into nano-compound-treated wood specimens resulted in considerably lower water absorption and volumetric swell. In previously decayed specimens treated with the nano-compounds and PB72 solution, water absorption after 2-h immersion declined compared to control specimens.     

Importing deciduous wood chips from North America to northern Europe – the risk of introducing bark- and wood-boring insects

Increasing inter-continental trade with wood chips represents a challenge for phytosanitary authorities as such trade may lead to pest introductions and invasions with huge impacts on forest ecosystems and economy. Predicting species invasions and their impacts in advance may be difficult, but improved information about potential invasive species ahead of any interceptions is an important precautionary step to reduce the probability of invasions. Here we identify bark- and wood-boring insects that have a potential to become invasive in northern Europe and that may be introduced by import of deciduous wood chips from North America. The potentially most damaging species belong to the beetle genus Agrilus (Buprestidae), which includes the highly damaging emerald ash borer A. planipennis. We give a brief presentation of this and seven other Agrilus species or subspecies and review factors of importance for the risk of establishment and potential economic and ecological impacts of these species. We also discuss one Scolytinae, Hylurgopinus rufipes. There are strong indications in the literature that some north European trees are highly susceptible to attack from the selected beetle species. We therefore conclude that because north European trees have not coevolved with these herbivores and thus may lack adequate defenses, most of the identified beetle species are likely to spread in “defense- and enemy-free space” if they are introduced to northern Europe, with considerable economic and ecological consequences.     

Time course of δ1¹³C in poplar wood: genotype ranking remains stable over the life cycle in plantations despite some differences between cellulose and bulk wood

Genetic differences in δ13C (isotopic composition of dry matter carbon) have been evidenced among poplar genotypes at juvenile stages. To check whether such differences were maintained with age in trees growing in plantations, we investigated the time course of δ13C as recorded in annual tree rings from different genotypes growing at three sites in southwestern France and felled at ～15-17 years. Wood cores were cut from tree discs to record the time course of annual basal area increment (BAI). The isotopic ratio δ13C was recorded in bulk wood and in extracted cellulose from the annual rings corresponding to the period 1996-2005. Discrimination against 13C between atmosphere and tissues (Δ13C) was computed by taking into account the inter-annual time course of δ13C in the atmosphere. Annual BAI increased steadily and stabilized at about 8 years. An offset in δ13C of ～1‰ was recorded between extracted cellulose and bulk wood. It was relatively stable among genotypes within sites but varied among sites and increased slightly with age. Site effects as well as genotype differences were detected in Δ13C recorded from the cellulose fraction. Absolute values as well as the genotype ranking of Δ13C remained stable with age in the three sites. Genotype means of Δ13C were not correlated to annual BAI. We conclude that genotypic differences of Δ13C occur in older poplar trees in plantations, and that the differences as well as the genotype ranking remain stable while trees age until harvest.     

Biological performance,water absorption,and swelling of wood treated with nano-particles combined with the application of Paraloid B72<Superscript>®</Superscript>

We evaluated fungal decay and mold resistance, leaching, and water absorption of nano-compounds and Paraloid B72^® (PB72) in treated wood specimens to develop new methods of consolidation by combining nano-particles and consolidants. Scots pine wood specimens were treated with dispersions of nano-CuO, nano-ZnO, nano-B₂O₃, nano-TiO₂, and nano-CeO₂. PB72 treatments of nano-particle-treated wood specimens were then carried out by either vacuum or immersion for 24 h. Previously, decayed wood specimens were also consolidated with the nano-compounds and PB72. PB72 treatments reduced element release from treated wood specimens. Nearly all nano-compounds + PB72 treatments increased the biological performance of treated wood specimens against decay fungi tested. PB72-only treated wood specimens had the highest weight losses in decay tests. No improvements were obtained in mold resistance tests when the nano-compounds and PB72 were combined. In nano-compound-only treatments, unleached specimens showed slightly lower water absorption values compared to untreated control specimens. Incorporation of PB72 into nano-compound-treated wood specimens resulted in considerably lower water absorption and volumetric swell. In previously decayed specimens treated with the nano-compounds and PB72 solution, water absorption after 2-h immersion declined compared to control specimens.     

Relationship between species diversity and tree size in natural forests around the Tropic of CancerOA

Although numerous hypotheses have been proposed to explain the patterns of species diversity of forests at local and landscape levels,it is still difficult to predict the alpha diversity of species,especially in tropical and subtropical natural forests where trees of different sizes and shapes are highly mixed.Size might characterize species diversity,and the possible correlation between these variables may contribute to the development of easy-to-use growth indicators to predict diversity and t...     

Relationship between multi-scale climate factors and performance of ecological engineering on the Loess Plateau,ChinaOA

The long-term "Grain-to-Green Program"(GGP)on China’s Loess Plateau is a major global ecological engineering project which has significantly boosted vegetation renewal.Some studies have found that the rate of restoration is quite rapid during the implementation of ecological engineering,however,the influence of multi-scale climatic conditions on the performance of ecological engineering is unclear.In this study,multiple sources of remote sensing data were used to estimate the dynamics of vegetat...