杨树短轮伐期集约栽培的新进展

本文介绍了参加18届国际杨树会议的17个会员国的杨树栽培新进展、杨树育种和短轮伐期集约栽培的研究动态和成果,还报道了与会外国专家的观感。     

Density profile relation to hardness of viscoelastic thermal compressed (VTC) wood composite

Density profile relation to hardness of VTC wood composites was evaluated using X-ray densitometry and modified Brinell hardness method using different applied forces. Moreover, surface elasticity was evaluated. Prior to lamination, the low-density hybrid poplar (Populus deltoides × Populus trichocarpa L.) and Douglas-fir (Pseudotsuga menziesii L.) thin boards were compressed to 1.22 or 1.14 g/cm³, respectively. Two different kinds of laminations were made, either single layer of 1.5 mm thickness or two 1.5-mm layers bonded to unmodified wood. The results show that thicker laminate has a great positive influence on Brinell hardness. This study suggests that results from the existing method for Brinell hardness are not comparable, and if applied force is chosen without restraint, the effect on the hardness value is significant for inhomogeneous wood composites.     

Discoloured wood of aspen caused by increment boring

Decay resulting from increment borings varies with tree species. Trembling aspen (Populus tremuloidcs Michx.) in Newfoundland is seriously affected by this particular wound. Three years after 20 trees had been bored, none had healed probably because of a pronounced split of the bark. The wood discoloration extended horizontally to about 2 cm on each side and vertically half metre above and below the wound. Peniophora polygonia (Pers. ex Fr.) Bourd. et Galz. was the most common fungus isolated while Polyporus adustus Willd. ex Fr. and several imperfect fungi and bacteria were also present.     

Identification and characterization of fungi associated with internal wood lesions and decline disease of willow and poplar trees in Iran

During the study of fungal trunk pathogens associated with urban trees decline in Shiraz (Iran), a serious decline of willow and poplar trees was observed. Therefore, an investigation was conducted on these trees in some areas of this city during spring and summer 2012 and 2013, to determine the main fungal trunk pathogens associated with these ornamental plants. Plant materials were collected from trees exhibiting disease symptoms such as yellowing, shoot canker, shoot dieback, defoliation and internal wood necrosis and decayed wood. Fungal isolations were made from discoloured or decayed wood tissue onto 2% malt extract agar (MEA) amended with streptomycin sulphate. Nine species, Fomes fomentarius, Diplodia seriata, Lasiodiplodia theobromae, Dothiorella sarmentorum, Neoscytalidium hyalinum, Diatrype whitmanensis, Phaeoacremonium rubrigenum, P. aleophilum and P. parasiticum, were identified based on morphology and DNA sequence comparisons. Pathogenicity tests were performed on detached shoots of willow and poplar trees under greenhouse conditions. Lasiodiplodia theobromae caused the longest lesions on willow. On poplar shoots, the longest lesions were caused by P. parasiticum. Diplodia seriata produced the smallest lesions on both woody hosts. First reports from willow wood include P. parasiticum, P. rubrigenum, D. whitmanensis, L. theobromae, D. seriata and N. hyalinum, while new reports from poplar wood include P. parasiticum and Do. sarmentorum. Based on our knowledge, this is also the first report of D. whitmanensis in Iran.     

Improvement of penetrability of sugi wood by impregnation of bacteria using sap-flow method

The sap flow method of wood impregnation was conducted to aid the movement of bacteria through the living tree, thereby accelerating their distribution through wood within a short time. When log-pond water containing mixed species of bacteria were introduced in the living trees by butt-end dipping and then laid horizontally for 6 months, bacteria could be delivered by sap flow vertically through the sapwood tracheids up to the high portions from the butt-end of trees; they could be detected in the ray parenchymal cells. The sap-flow method was assumed to deliver the bacteria to sapwood and heartwood at high levels of standing sugi (Cryptomeria japonica D. Don) trees. Degradation of the pit membranes was observed even at more than 3 m upward from the butt-end after the treatment in sapwood, as well as around the butt-end of the trees. The uptake of the aqueous dye solutions in sapwood of the treated logs were about eight times more than those of control specimens after 8h.Part of this report was presented at the 40^th annual meeting of the Japan Wood Research Society, Tsukuba, April 1990; the 41^st annual meeting of Japan Wood Research Society, Matsue, April 1991; and the IUFRO 4^th international conference on wood drying, Rotorua, New Zealand, August 1994     

Development of two microsatellite multiplex PCR systems for high throughput genotyping in Populus euphratica

Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Torr. & Gray were screened for amplification in Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were selected to set up and optimize two multiplex polymerase chain reaction (PCR) assays. Three populations containing altogether 436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate for merging genotypes to be less than 0.045. Foundation project: This study was supported by the Deutsche Forschungsgemeinschaft DFG (grant number SCHN 1080/1-1)     

Improvement of wood properties by urea-formaldehyde resin and nano-SiO2

In order to improve wood properties of triploid clones of Populus tomentosa, urea-formaldehyde (UF) resin was compounded with nano-SiO₂, coupling agents and flame retardants in different ways to prepare five kinds of modifiers. The poplar wood samples were impregnated with the modifiers and heated to prepare UF-SiO₂-wood composites. The antiswelling efficiency, resistance of water absorption, oxygen index and hardness of the composites were measured. Results show that all of the modifiers reduced water absorption of poplar wood and enhanced flame resistance and hardness. Nano-SiO₂ showed a marked effect in improving the hardness of wood. In addition, all of the modifiers, except UF-C-SiO₂-polymer, improved the dimensional stability of poplar wood. The UF resin and nano-SiO₂ compound improved general properties of poplar wood. __________ Translated from Journal of Beijing Forestry University, 2006, 28(2): 123–128 [译自: 北京林业大学学报]     

Field test of new poplar clone in Shangdong Province

Poplar is one of the dominant tree species for the establishment of fast growing plantations in Shandong Province.Eighteen poplar clones belonging to Populus aigeiros section were introduced from Italy, Turkey and domestic regions. Populus deltoides cv. ‘Lux‘ 1-69/55 (1-69), which was widely used in Shandong Province, China, was taken as control clone (1-69).Following a randomized complete block design, seedling test and controlled afforestation trials were carried out at Juxian County,Caoxian County and Laiyang City. The results showed that the poplar clone (Populus x euramericana cv. ‘102/74‘), namely 102/74, performed well both in terms of adaptability and growth rate. The mean height of 13.9 m (H), diameter at breast height of 18.0 cm (DBH) and volume growth of 0.1445 m3 (V) were 2.2 %, 21.6% and 52.9% higher than those of 1-69 (CK), respectively,at the age of 5 years at three experimental sites. Moreover, the clone can be propagated easily and showed high resistance to poplar disease, pest as well as salinity and had longer growing period. Furthermore, wood basic density and fiber length of new poplar clone (102/74) were as same as 1-69 (CK). It was concluded that the selected clone (102/74) was ideal for the estab-lishment of fast-growing poplar plantations, especially for the pulpwood plantations in Shandong Province.     

ITS-based comparison of endophytic mycota in twigs of native <Emphasis Type="Italic">Populus nigra</Emphasis> and cultivated <Emphasis Type="Italic">P. x euramericana</Emphasis> (cv. I-214) stands in Northern Spain

Context  

The European black poplar (Populus nigra) is considered one of the most seriously endangered indigenous tree species. However, the total area covered by monoclonal plantations of hybrid poplar is growing, because of the high profitability of these trees.     

Sporendocladia bactrospora associated with wounds on native broadleaved trees in Norway and Sweden

A survey to identify ophiostomatoid fungi that infect wounds on native Norwegian and Swedish broadleaved trees was undertaken during summer 2004. A fungus resembling a species of Sporendocladia was commonly isolated from the exposed cambium and inner bark of wounds. Morphological examination and comparisons of DNA sequence data for the ITS and 5.8S regions of the rRNA gene region led to its identification as Sporendocladia bactrospora. Pathogenicity trials on young Populus tremula and Betula pubescens trees showed that S. bactrospora is capable of causing lesions on these trees. There have been few previous reports of S. bactrospora, and in most cases, these have been as saprophytes on wood. In contrast, results of this study show that it is a common inhabitant of freshly made wounds on native broadleaved trees in Scandinavia, and it appears to contribute to staining of wood.     

Density profile and morphology of viscoelastic thermal compressed wood

The viscoelastic thermal compression (VTC) of low-density hybrid poplar (Populus deltoides × Populus trichocarpa) from fast growing trees was performed in order to produce specimens with three different degrees of densification (63, 98, and 132%). The morphology and density profile of the VTC specimens were studied. Three different methods for the preparation of specimens for microscopy were used in order to find a technique that makes it possible to examine the VTC wood microscopically in the completely deformed state. It was found that the abrasive surface preparation of oil-embedded blocks was the most promising technique. Microscopic observation revealed that the deformations in the VTC wood were mostly the result of the viscous buckling of cell walls without fracture. The volume of the void areas in the specimens decreased with the degree of densification. The results showed that the density profile of the VTC wood varied with the degree of densification as a consequence of different temperature and moisture gradients formed before and during wood compression. The density profile is also visible on the cross-section of the VTC specimens.     

Comparison of transverse compression creep of Pseudotsuga menziesii and Populus sp. in high-temperature steam environments

Compression creep experiments of Douglas-fir wood (Pseudotsuga menziesii) were performed at high temperature (150°C, 160°C, and 170°C) and under various conditions of steam pressure. The results established that environment conditions had a significant effect on compressive deformation, with the largest deformation obtained under saturated steam conditions. While the temperature significantly affected the compressive deformation of specimens under transient conditions, the temperature within the range studied had little effect on the compressive deformation in saturated steam. Furthermore, in specimens compressed under superheated and transient steam conditions, primary creep behavior was exhibited; while in specimens compressed under saturated steam conditions, creep deformation appeared to enter directly into secondary creep. Moreover, in saturated steam specimens very little creep was observed due to high initial deformation and little potential for additional cell wall buckling. The compressive creep measurements of Douglas-fir were compared with compressive creep of hybrid poplar (Populus deltoides × Populus trichocarpa). Due to lower initial density, and perhaps smaller microfiber angle and lower lignin content of tension wood, the compressive creep modulus of hybrid poplar was lower than Douglas-fir. Therefore, compressive deformation of Douglas-fir, at nearly all examined steam conditions and temperatures, was smaller than compressive deformation of hybrid poplar.     

A feasibility study of using two-component polyurethane adhesive in constructing wooden structures

This investigation was conducted to determine the feasibility of using a two-component polyurethane （PUR） adhesive, with special waterproof properties, in constructing wooden structures. We designed and conducted tests to compare the shear strength and adhesion performance of PUR with polyvinyl acetate （PVAc） adhesive on block-shear specimens constructed of oriental beech （Fagus orientalis L.）, fir （Abies alba Mill.）, poplar （Populus deltoides Bartr.）, white oak （Quercus alba L.）, sycamore （Platanus orientalis L.） and white walnut （Juglans cinerea L.）. The values of the percentage of wood failure were also determined in specimens constructed with each adhesive. The highest shear strength values of both adhesives were obtained in specimens constructed of beech, while the lowest shear strength values were obtained in fir and poplar specimens. Average shear strength of the PUR adhesive was 16.5% higher than that of the PVAc adhesive. Specimens constructed of fir, poplar and sycamore were characterised by the highest percentages of wood failure, whereas the lowest average percentages of wood failure were obtained in beech and oak specimens. With the exception of oak specimens, there was no statistically significant difference between percentage of wood failure among the PUR and PVAc adhesives. Generally, the PUR adhesive showed an acceptable adhesion performance on wood materials used in our study.     

Influence of the thermo-hydro-mechanical treatments of wood on the performance against wood-degrading fungi

Hybrid poplar (Populus deltoides × Populus trichocarpa) and Douglas-fir (Pseudotsuga menziesii) wood specimens were densified with three variations of thermo-hydro-mechanical (THM) treatment. The THM treatments differed in the steam environment, including transient steam (TS), saturated steam (SS), and saturated steam with 1-min post–heat treatment at 200 °C (SS+PHT). The bending properties, FTIR spectra, and colour of the THM wood specimens were studied before and after exposure to two different wood decay fungi, brown rot Gloeophyllum trabeum, and white rot Trametes versicolor. The results showed that the performance of densified hybrid poplar wood was considerably poorer than the performance of Douglas-fir heartwood. The FTIR spectra measurements did not show changes in the densified hybrid poplar wood, while some changes were evident in densified Douglas-fir specimens. After fungal degradation, the most prominent changes were observed on the SS+PHT specimens. Colour is one of the most important parameter predominantly influenced by the wood species and the intensity of the densification process for both wood species, while after fungal exposure, the colour of all densified Douglas-fir specimens obtained more or less the same appearance, and densified hybrid poplar specimens resulted in lighter colour tones, indicating that the pattern of degradation of the densified and non-densified specimens are similar. The 3-point bending test results determined that the THM treatment significantly increased the modulus of rupture (MOR) and modulus of elasticity (MOE) of the densified wood specimens, while fungal exposure decreased the MOE and MOR in hybrid poplar and Douglas-fir specimens.     

Microbial population in rotten living body ofSalix matsudana

The microbial population in rotten living body ofSalix matsudana caused byTrametes suaveolens (L.) was researched. 11 bacteria species (1 species ofBacillus, 2 species ofClostridium and 8 species of non-brood-cell bacteria), 1 species ofActinomyces that belongs to Lavendulac, 8 species of fungi and 6 species ofTrichoderma were isolated from rotten trunk. The hyphae ofTrametes suaveolens mainly existed between rotten sections and discoloration sections. In over-rotten section and healthy section the fungi (Trametes suaveolens) were not isolated. The microbes that lived in the discoloration section were the most in kinds and number and they were the pioneer microbes of wood rotting. Only after they dwelled in wood and eliminated its rot-resistance, could wood-rotting fungi invade wood and caused wood-rotting. Responsible editor: Zhu Hong     

Intercropping hybrid poplar with soybean increases soil microbial biomass,mineral N supply and tree growth

We hypothesized that tree-based intercropping in southwestern Québec, Canada, would stimulate soil microbial activity and increase soil nutrient supply, thereby benefiting the growth of trees. Our experimental design comprised alternating rows of hybrid poplar (Populus nigra L. × P. maximowiczii A. Henry) and high-value hardwood species spaced 8 m apart, between which two alley treatments were applied 5–6 years after planting the trees. The first alley treatment consisted of a fertilized soybean (Glycine max (L.) Merr.) intercrop grown over two consecutive years, while the second consisted of repeatedly harrowing to minimize vegetation in the alley. Tree rows were mulched with a 1.5 m wide polythene mulch. Microbial respiration and biomass, and mineral N concentrations and mineralization rates were measured on five or six dates at 0, 2 and 5 m from hybrid poplar rows. On some of the sampling dates, we found significantly higher soil microbial biomass, mineral N concentrations and nitrification rates, and a significantly lower microbial metabolic quotient (qCO₂), in the soybean intercropping than in the harrowing treatment. Over the 2 year period, hybrid poplar biomass increment and N response efficiency (NRE) were significantly higher (51 and 47%, respectively) in the intercropping than in the harrowing treatment. Microbial biomass and mineral N supply were significantly lower beneath the polyethylene mulch than in the alleys, and we posit that this may stimulate the growth of tree roots into the alley. We conclude that soybean intercropping improves nutrient turnover and supply for hybrid poplar trees, thereby increasing the land equivalent ratio (LER).     

Relationships between growth stress and wood properties in poplar I-69 (Populus deltoides Bartr. cv. “Lux” ex I-69/55)

Six inclined poplar I-69 (Populus deltoids cv. I-69/55) trees were collected for studying the influence of growth stress level on wood properties. Growth stress indicator (GSI) was measured at eight positions around the periphery of each trunk at breast height and corresponding wood samples were obtained. Wood anatomical, physico-mechanical and chemical characteristics were measured, including cell diameter, fibre length, double wall thickness excluding the gelatinous layer, lumen diameter after gelatinous layer removal, proportion of wood tissues, basic density, FSP, MOE, compressive strength, shrinkage and chemical composition. Each property was regarded and discussed in relation to the growth stress level.     

An improved technique for non-destructive measurement of the stem volume of standing wood

An improved technique, cheaper and less time-consuming, to measure standing wood volume by using an electronic theodolite was tested, by which greater information from the forest could be acquired accurately and non-destructively. This was achieved by recording the diameter at breast height and ground-level diameter of a tree as well as the included angle between the electronic theodolite and the left and right tangents of the stem at any point. The standing wood volume then was computed precisely by section. In addition, the factors that influence the precision of the method (observable distance and number of segments) were also analysed. In the study, 175 Larix gmelinii (Rupr.) Kuzen. trees and 190 Populus tomentosa Carrière trees chosen randomly for sampling were measured with the electronic theodolite, and then were cut down for measurement of the average cross-section volume. Based on the data acquired from 100 sample trees, a standard volume table was compiled, and then the data for the remaining random 10 sample trees in each group were selected for a comparison test. The results indicated that the optimal distance for indirect observation should be as high as the sample tree, and the optimal visual distinguished section was about 2?m. The correlation coefficient between the value measured non-destructively and the value of the felled trees of L. gmelinii was 0.97, with an average relative error of 1.62%. With regard to P. tomentosa, the correlation coefficient between the two values obtained by the two methods was 0.905 with an average relative error of 8.40%. It was concluded that the standard volume model based on the non-destructive measurement technique meets the requirements for precision in forest surveys. The precision of the standard volume model for L. gmelinii (a coniferous tree) was superior to that of the model for P. tomentosa (a broad-leaved tree). The electronic theodolite method provides an alternative technique for measuring trees without destructive sampling and is widely applicable for forest surveys.     

Wood Microstructure Effects on Chinese White Poplar Dyeing

In order to study the influence of wood microstructure on wood dyeing, eleven parameters of wood microstructure and 5 parameters of wood dyeing effects for 34 pieces of wood boards from 5 trees of Chinese white poplar (Populus tomentosa) were determined and the multiple regression analysis between the factors of wood microstructures and the parameters of wood dyeing effects were made. The regression results show that each variable of wood dyeing effects has higher relationship with wood microstructures, and multiple correlation coefficients between each variable of wood dyeing effects and wood microstructures are 0.483 6~0.799 8. The main factors of wood microstructures influencing wood dyeing of Chinese white poplar are proportion of wood ray, proportion of vessel and proportion of wood fiber according to comparing the standardized regression coefficients of multiple regression equation.