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1.
? Quinones are primarily responsible for the natural durability of teak. ? The previous paper in this series reported on the natural termite resistance of teak trees of different ages (8-, 30- and 51-year-old trees). In this study, the radial distribution of quinones (tectoquinone, lapachol, desoxylapachol and its isomer) and other components in the ethanol-benzene (1:2) extract were measured by means of gas chromatography. ? Significant differences in desoxylapachol or its isomer content were found among the outer heartwood of 8-, 30- and 51-year old trees, as well as between the inner and outer parts of the heartwood. ? All toxic quinone contents were positively correlated with the total extractive content. The highest correlation degree was measured in the isodesoxylapachol content. ? Although linearly related, only modest correlations were observed between the natural termite resistance parameters and the content of tectoquinone and isodesoxylapachol. 相似文献
2.
? Decay resistance of larch (Larix sp.) to fungi was evaluated on heartwood samples belonging to 3 species (L. decidua, L. kaempferi and their hybrid), 3 races of European larch (polonica, sudetica and alpine), 13 wood lots (populations) and 313 trees. ? Larch wood appeared, on average, as moderately durable although a high variability was observed. At the sample level as well as at the mean individual tree level, durability ranged from class 1 to 5 according to EN 350-1 standard. At the population level, larch wood varied from ‘durable’ to ‘slightly durable’. Genetics played a major role in decay resistance at the species, provenance and tree levels. Environmental factors such as the position of heartwood samples and the age of trees were also identified as a source of variability. ? The most durable wood was not necessarily from old native alpine stands of European larch: some young larches from faster growing lowland origins also produced durable wood. ? Genetic improvement of larch wood durability appeared therefore likely by the selection of the best populations for decay resistance as well as from the selection of individuals. 相似文献
3.
? The effect of brown-rot (Coniophora puteana) decay on the water adsorption capacity and concentration of extractives of Scots pine (Pinus sylvestris L.) heartwood were studied by comparing corresponding properties of decayed and undecayed wood samples. ? The samples derived from 39 felled trees having a large between-tree variation in the extractive concentrations, and subsequently in the mass loss in the decay test. The water adsorption capacity, expressed as equilibrium moisture content (EMC), was measured at a high relative humidity (RH ～100%, 21 °C). ? In contrast to the widely held belief, the water adsorption capacity of brow-rotted heartwood appeared to be significantly higher than that of undecayed heartwood. ? The chemical composition of heartwood was changed radically by the fungus: the concentration of stilbenes, resin acids and free fatty acids decreased, while the concentration of soluble sugars increased as a result of decay. In addition, fungal sugars were found in the decayed samples. The concentration of total phenolics increased, which obviously reflected chemical changes in cell wall constituents other than extractives. ? As a conclusion, the information concerning the hygroscopicity of brown-rotted wood might be valuable e.g. when carrying out repairs on buildings damaged by advanced decay. 相似文献
4.
? Allometry of sapwood/heartwood is essential for understanding tree growth, water transport and carbon allocation, timber production and use, but such an allometry is lacking for Chinese temperate tree species. ? We studied the allometry and development of heartwood and sapwood for seven Chinese temperate tree species: Korean pine (Pinus koraiensis Sieb. et Zucc), Dahurian larch (Larix gmelinii Rupr.), Japanese elm (Ulmus davidiana Planch var. japonica (Rehd.) Nakai), Manchurian ash (Fraxinus mandshurica Rupr.), Manchurian walnut (Juglans mandshurica Maxim.), Amur cork-tree (Phellodendron amurense Rupr.), and Mongolian oak (Quercus mongolica Fisch.). ? All heartwood parameters investigated, including heartwood radius (HR), heartwood formation rate (HFR), heartwood ring number (HRN), heartwood initiation age (HIA), and heartwood volume ratio (HVR), were positively correlated with tree cambial age (CA). The HR, sapwood width (SW), sapwood area (SA), heartwood and sapwood volumes were significantly related to stem diameter at breast height (DBH) or xylem diameter. There was a polynomial relationship between the sapwood ring longevity (SRL) and sapwood ring number (SRN). However, most of the allometric relationships were species-dependent. The hardwood formation patterns were different between coniferous and broadleaved tree species. A power function was suitable to scale SA from DBH, but the exponent varied from 1.32 for the larch to 2.19 for the cork-tree. ? Our allometry provided a practical means to assess wood development and related physiology for the temperate tree species. 相似文献
5.
? Wood colour of Tectona grandis produced from fast-growth plantations is highly variable and the causes of this variation are relatively unknown. ? With the purpose of understanding the colour variation, different fast-growth plantations were sampled with different growth rates, tree ages, and sites. ? Wood colour was measured with a CIELab system, where three variables are estimated: coordinate L* for lightness, coordinate a* defines redness and coordinate b* defines yellowness. ? Results showed only a negative correlation between L* and a*. L* and a* were negatively and positively respectively correlated with pith distance in heartwood, but not for b*. No correlations were found between L* and b* in sapwood and plantation characteristics, while a* was positively correlated with age and height of tree and growth rate. In heartwood, tree age and diameter at breast height were correlated with all colour parameters, but tree height and plantation density were correlated with a* and b*. Cluster site had correlation with L*. Multiple correlation analysis showed that the heartwood is increasing darker (L*) and redder (a*) when the trees are older and bigger. Correlation coefficient shown that sapwood and heartwood with lighter colour (L*) is less resistance to fungal attack, but redness colour (a*) increasing decay resistance. 相似文献
6.
? The objective of this study was to explore the distribution of major nutrients (N, P, K, Ca and Mg) in the aboveground compartments of an intensively managed tree species (Pinus pinaster Ait.). A total of 53 trees were cut down in even-aged stands respectively 8, 16, 26, 32 and 40 years old. The nutrient concentrations of the aboveground compartments were analysed. ? Nutrient concentrations of foliage did not vary with any of the variables used, except needle age. Nutrient concentrations of living branches, stem bark, stem sapwood, stem heartwood, stemwood and stem decreased with increasing branch diameter, bark thickness, sapwood thickness and heartwood thickness, respectively. Beyond a certain value of the predictive variable (stem diameter ≈ 15 cm; branch diameter ≈ 2.5 cm), the concentration of all the nutrients stabilised. ? A 50 year-old pine stand was used to obtain a validation dataset for nitrogen concentration. For this nutrient, the regression relationships gave satisfactory estimates for most compartments (mean error = 12–25%) and particularly for the stem. ? A procedure is proposed to estimate the nutrient exports associated with harvests of Pinus pinaster biomass. 相似文献
7.
? Studies of allometric relationships between leaf area and the cross-sectional area (CSA) of sapwood in the stem have shed light on the structural and functional relationships between water-conducting and photosynthetic tissues. ? The purpose of this study was to test whether sapwood-leaf area relationships could be extended from stems to roots in coast Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco). Twelve trees were felled, their stumps were excavated, and the CSA of sapwood and heartwood were estimated for individual roots, entire root systems, and stem section. ? Root sapwood CSA was greater than sapwood CSA throughout the stem, and the ratio of leaf area to sapwood CSA (A l :A s ) was accordingly lower for root sapwood. The relationship between sapwood CSA and leaf area was more variable in roots and at groundline compared to crown base. Root A l :A s decreased with relative tree height (tree height/mean stand height). ? The strong allometric relationship between leaf area and the CSA of sapwood in the stem generally holds when extended to roots. The greater CSA of sapwood in roots versus stems may reflect differences in their roles in supporting the tree. 相似文献
8.
? Eperua grandiflora, which is widely distributed in the French Guiana forest region, shows high variability in decay resistance. Further information concerning this wood quality parameter is necessary, but standard testing methods are complex and time-consuming. We assessed the use of colorimetry to determine durability in heartwood samples from a range of trees. ? Eperua grandiflora colour parameters were measured using a CIELAB system, revealing that the tree effect was greater than the radial position and height effects. ? The wood samples were exposed to Coriolus versicolor and Antrodia sp. according to two European standards (En 350-1 and XP CEN TS 15083-1). Eperua grandiflora is more susceptible to brown rot. These two standards did not give the same durability classes. The high variation in natural durability was due to the tree effect. ? These two properties were found to be correlated and the assessment also distinguished the extreme durability classes but they are not sufficient to classify the class of durability of this species. 相似文献
9.
? Our aim is to present why the hypothesis, that Ophiostomatoid fungi play an important role in the establishment of most bark beetle species on living conifers, is valuable. ? After summarizing knowledge about the relationships of bark beetles with conifers and fungi, we conclude that controversy results from misinterpretations when using fungal pathogenicity to demonstrate the role of Ophiostomatoid fungi in beetle establishment on host trees. ? We demonstrate that fungal pathogenicity is not the right parameter to appreciate the role of fungus in beetle establishment on host trees. We argue that artificial low density inoculations that allow the appreciation of fungus ability to stimulate tree defenses and thus to help beetles in overcoming tree resistance must be used in complement to mass inoculations. In both cases, results must be expressed in terms of tree defense stimulation rather than in terms of tree killing. - Fungal species stimulating tree defenses are generally not those that grow the best in the sapwood.
- We argue that beetle development in the phloem, fungal invasion of the sapwood and phloem, and tree death, occur after tree defenses are exhausted, and that any fungus present in the beetle gallery could thus potentially invade the sapwood after defense exhaustion.
? We conclude that stimulation of the tree defense reactions in both the phloem and the superficial sapwood is a real benefit brought by fungi to the beetles during the first phase of establishment (overcoming tree resistance). ? Considering the origin of the bark beetle fungus associations attacking living trees and their general functioning based on stimulation of tree defenses, we develop three hypotheses: - any beetle species would be helped in its establishment in a given tree species by developing an association, even loosely, with a fungus species belonging to the Ophiostomatoid flora of that tree species;
- the necessity of a considerably low level of tree resistance for fungus extension into the tree is the selection pressure that has led fungi to develop their intrinsic ability to stimulate tree defenses, through their ability to grow into the phloem. This association can be completed by antagonistic fungal species controlling extension of the previous fungal species in the tree tissues;
- Beetle species using the strategy of overcoming tree resistance are associated with a fungal complex, of which species could assume three roles regarding relationships between beetles and trees: 1- to stimulate tree defenses in the phloem and superficial sapwood, 2- to grow into the sapwood after tree resistance is overcome, and 3- to control phloem extension of the first other two categories. Bringing nutrients to the beetle progeny can be a fourth role.
? We propose that bark beetle — Ophiostomatoid associations can be categorized, based on associations’ frequency and complexity while taking into account beetle aggressiveness. We show that a close correspondence exists between beetles’ aggressiveness and the ability of their main associated fungal species to stimulate the defenses of their host tree. ? We conclude with suggesting that most sapwood invading fungi might be “cheaters” which have taken advantage of the efficiency of the relationship between beetles and fungi that stimulate tree defenses. 相似文献
10.
? Awareness of the shortage of fossil resources leads to an increasing demand for woody biomass. We investigated the feasibility of using fast-growing Gmelina arborea wood for material production. Gmelina arborea wood samples were collected from trees of varying cambium ages in Indonesia, from 3.5-, 7- and 12-year-old plantations. ? The lateral growth rate and the cambium age did not significantly affect the longitudinal released strain of the growth stress, xylem density, or microfibril angle at the outermost surface of the secondary xylem at any sampling site. However, fiber length in the 3.5-year-old plantation tended to be shorter in smaller diameter trees, whereas in larger diameter trees it was almost the same as that in trees from the 7- and 12-year-old plantations. This suggests that smaller diameter trees in the 3.5-year-old plantation had not yet produced mature wood. ? Xylem qualities had already reached values appropriate for harvesting, except in the smaller diameter trees from the 3.5-year-old plantation. This indicates that the larger diameter trees had already matured, regardless of their cambium age. These results suggest that the next step is to develop silvicultural treatments to increase the lateral growth rate during the early growing stage, in order to produce as much mature wood as possible, as quickly as possible. 相似文献
11.
? Identification of extractives present in Cupressus lusitanica heartwood has been conducted using GC-MS analyses. The chromatogram of toluene/ethanol extracts indicated the presence of large amounts of benzaldehyde and numerous terpenic compounds such as cedrol, agathadiol, epimanool, bornyl acetate, α-cedrene and β-cedrene. ? The effect of these extractives on the natural durability of cypress wood was investigated on heart wood blocks exposed to pure culture of Poria placenta before or after solvent extraction. Weight losses revealed severe fungal degradations on the extracted blocks compared to unextracted ones. ? Efficiency of heartwood extractives as inhibitors of the growth of Poria placenta on malt/agar test confirms their contribution to cypress natural durability. ? Cypress blocks were treated at 240 °C for different times to reach different levels of thermodegradation to evaluate effect of heat treatment on fungal durability. Results indicate that evaporation of volatile extractives during the first few minutes of heat treatment contribute to decreased wood durability, while longer treatment times lead to the expected improvement of durability. ? This study suggests that the content of extractives, which may be modified during wood drying or weathering processes, could be the origin of the conflicting data described in the literature concerning cypress natural durability. 相似文献
12.
?The study aimed at clarifying basic life traits (fecundity, mortality and development) of Monochamus galloprovincialis, the vector of Bursaphelenchus xylophilus, the causative agent of the Pine Wilt Disease, in Portugal. ? Mating and oviposition experiments were conducted on P. sylvestris logs under laboratory conditions during two years. Larval development was followed outdoors. ? Fecundity was high, with 138.2 eggs per female. ? For the first time, the number of larval instars (4) in M. galloprovincialis was recognized and instars were described. ? Informations are provided on the shape and size of the larval galleries. Boring of galleries in sapwood and heartwood started at the third instar. All instars could overwinter but adults emerged simultaneously resulting in a univoltine life cycle for the majority of the individuals. ? An obligatory diapause in the forth instar was assumed. However, 8.1% of the insects had a two year development. ? Important differences in mortality were noted between the two experimental years, which could be explained by differences on the size of the breeding logs. ? There is a high biological proximity between M. galloprovincialis populations in France and those in Portugal and Northern Europe. However, a higher fecundity and longevity was observed in France, as well as a higher percentage of insects with a two year development, compared with portuguese populations. 相似文献
13.
? The physical properties of wood and the associated variations within and between trees were evaluated by analysing 770 small specimens of clear wood from 11 Pinus sylvestris L. trees thinned from 3 plantations. ? Within-tree variations in basic density or volumetric shrinkage increased with cambial age and decreased with increasing ring width. The effect of the height in the stem on wood properties was considered indirect and height was not included as an explanatory variable in the mixed models proposed to estimate basic density and volumetric shrinkage. ? The models had random components for the intercept parameter and explained 52.5% of the total variance in basic density and 56% of the total variance in volumetric shrinkage. Linear shrinkage in the direction of the grain was extremely variable. ? Between-tree variation and between-plot variation in the physical properties of wood were high, considering that all trees sampled were growing in similar sites and stands. It would then be desirable to predict physical properties of wood on living trees in order to use the quality of wood as a criterion for timber tree selection in thinnings. 相似文献
14.
? The aim of this work was to examine the anatomy and functioning of secondary xylem in stems in relation to the decline of European ash (Fraxinus excelsior L.). ? We tested the hypothesis that declining trees show changes in the structure of wood, which result in impaired water transport. ? Anatomical analyses were carried out on wood samples (comprising all annual rings formed during the 30 years life of the analysed trees) collected at breast height from the main stem of healthy, weakened and dead ash trees. The width of annual wood increments, the diameter and density of earlywood vessels were measured and the theoretical hydraulic conductivity index through the secondary xylem calculated by application of Hagen-Poisseuille’s formula. ? Anatomical characteristics changed both with the age of trees and in response to unfavorable factors. The largest vessels were observed in healthy trees, which implied that they had the highest hydraulic conductivity index, whereas trees considered to be in decline produce smaller vessels and hence had reduced conductivity. 相似文献
15.
? Direct assessment of modulus of elasticity (MOE) on standing trees is attractive for breeders to evaluate genotypes prior to selection: this can be done using the Rigidimeter, a bending-based measurement device. ? In this study, we tested its reliability to properly rank genotypes by relating trunk MOE with MOEs estimated with a vibrating analysis system (Bing) on different types of conditioned wood specimens from the same trees (boards and standardised 2×2×30 cm-clear-wood specimens). One hundred and ten trees from different genotypes of hybrid larch (Larix × eurolepis) were tested. ? Mean trunk MOE was 7 300 MPa with a similar value obtained for sawn boards. Clear-wood specimens MOE increased from pith to bark from less than 6 000 MPa to nearly 9 000 MPa. Moderate correlations (r = 0.48–0.61) were found at the individual tree level between trunk MOE and MOE of wood samples. ? Single specimen MOE was shown to be strongly related to a linear combination of trunk MOE and sample position. ? At the genotype mean level, trunk MOE was highly correlated with wood samples MOE (r = 0.80–0.91). Ranking of genotypes based on trunk MOE was mostly consistent with that based on standardised specimens. ? It was concluded that besides other operational advantages which are discussed, the Rigidimeter is a valuable tool for breeders to routinely evaluate and rank genotypes for stiffness prior to further selection. 相似文献
16.
? Leaching of biocide treated wood leads to reduced effectiveness and potential threat to the environment. ? Therefore the effectiveness of organosilicons as protective systems of biocides was evaluated. Scots pine sapwood specimens were impregnated with solely organosilicons and biocides as well as with combinations of both. ? The biocides 3-iodo-2-propynylbutylcarbamate, propiconazole and 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride confirmed their effectiveness regardless the addition of an organosilicon. Low leachate toxicities to the crustacean Daphnia magna were found for the organosilicons, whereas significant leachate toxicities were measured for the biocides. Combining both did not considerably diminish the leachate toxicities. ? It must therefore be concluded that under the circumstances as described in this article, organosilicons do not interfere with the efficacy of the biocides, but they do not contribute to a reduced leaching of the biocides either. 相似文献
17.
? Eight-year old trees from two Eucalyptus globulus Labill. clones planted across three different sites in Tasmania, Australia, were sampled for wood and kraft pulp/handsheet properties. ? Site had a significant effect on all measured properties. Compared with the poor site (Parkham) the wood from the good site (West Ridgley) had on average 11 % lower wood density. The poor site had also greater microfibril angles, shorter fibres at lower pulp yields. ? The handsheets produced with pulp from the poor site resulted in comparatively higher bulkiness, lower burst, lower tear and tensile indices, lower zero span tensile strength, but higher opacity, higher light scattering and higher surface roughness. Significant height effects were found with all wood properties, and also with tear index, zero span tensile strength and opacity. ? Discriminant analysis showed that for 76 out of 100 handsheets the raw material source, i.e. growth site, could be predicted correctly using a set of handsheet properties with tear index and bulk index being most prominent. ? This is unique evidence that site conditions are strongly reflected in handsheet properties produced from Eucalyptus pulp. 相似文献
18.
? At present, the production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as phenol-formaldehyde (PF) resins and urea-formaldehyde (UF) resins, which are non-renewable and therefore ultimately limited in supply. ? This paper concerns the decay resistance of wood products bonded with a new, environment-friendly adhesive derived from abundant and renewable cornstarch and tannin. To improve the total resistance of the composite against both Coriolus versicolor and Coniophora puteana rot fungi, borax (di-sodium tetraborate) was added in proportions of 0.5%, 1% and 2% (w/w) to the cornstarch-tannin adhesives. ? The results show that increasing the concentration of borax in the adhesive decreased the mechanical properties of the composite. The best way to avoid this problem was to use wood impregnated with borax. ? Biodegradation studies were conducted on new composites, first without any treatment, followed by borax at 0.5% aqueous solution treatment. The results show that wood impregnated with borax, in the presence of tannin and sodium hydroxide in the adhesive improves the total resistance of the wood composite against both Coriolus versicolor and Coniophora puteana rot fungi. 相似文献
19.
? Environmental determinants of wood properties variation were examined in Eucalyptus globulus, a globally important hardwood plantation species, in southern Tasmania, Australia. ? Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees. ? Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees. ? Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated. 相似文献
20.
? Variation in wood basic density and its correlation with tree growth were investigated at 13 years in a provenance/progeny test of Prosopis africana in Niger. The test included progeny from 256 trees sampled from 24 provenances in the Sahelian ecozone of Burkina Faso and Niger. ? Variation in wood density was significant due to provenances and families within provenances. Individual tree heritability was higher for wood density than for growth traits. Provenance means for wood density increased from the more humid to the drier parts of the sample region. Phenotypic correlations indicated that larger trees tended to have denser wood. ? Clines suggest that natural populations of P. africana from the drier parts of the sample region have the genetic capacity to produce denser wood, compared with populations from the more humid parts of the region. Correlations and heritability estimates suggest that selection of faster-growing trees may produce a small gain in wood volume but little (if any) gain in density in the subsequent generation. Multi-location provenance/tests are needed to confirm this tentative conclusion. 相似文献
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