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热处理对于提高木材的尺寸稳定性和耐久性、抵抗生物破坏等性能来说是一种非常有效的方法。作者采用油浴法对思茅松木材进行热处理工艺的探讨,分别对热处理木材的失重率、吸湿率、线性胀缩率、以及微观构造等进行了分析,研究结果表明：（1）思茅松热处理材随着处理温度和处理时间的增加,失重率逐渐增加;（2）思茅松热处理材随着处理温度和处理时间的增加,吸湿率逐渐降低;（3）思茅松热处理材随着处理温度和处理时间的增加,线性胀缩率逐渐降低;（4）在微观构造观察方面,由于早材腔大壁薄,材质较松软,经过热处理后早材部分容易引起径向开裂,早材管胞形态的变形程度要比晚材要大,早材轴向管胞壁的弯曲变形较晚材的要严重。随着热处理温度升高,热处理时间的延长,炭化程度越来越严重,为不使木材物理力学以及微观构造方面遭到严重破坏,建议木材热处理温度为160℃、热处理时间为6～12h或木材热处理温度为180℃、热处理时间为6～8h为宜。 相似文献
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试验采用过热蒸汽作为传热介质和保护气体,对圆盘豆木材进行热处理,热处理温度为160℃、180℃、200℃、220℃,热处理时间为2h、4h、6h、8h,并采用紫外光谱和气-质联用对圆盘豆木粉抽提物进行分析。结果表明,热处理后圆盘豆木材颜色发生明显变化。随着热处理温度升高,木材明度L*下降,红绿色品指数a*变化不明显,黄蓝色品指数b*下降,色差△E*增大,木材表面颜色加深,其主要原因是木素及木材抽提物发生了氧化、还原反应。 相似文献
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以大果紫檀（Pterocarpus macrocarpus）、奥氏黄檀（Dalbergia oliveri）、光亮杂色豆（Baphia nitida）三种热带阔叶树材为研究对象,在160、180、200℃下对其进行热处理,探究热处理温度对其心材的颜色、尺寸稳定性的影响。结果表明：随着热处理温度的升高,三种木材的质量损失率均逐渐增大,颜色逐渐加深,热处理对光亮杂色豆和大果紫檀的颜色影响更大;三种木材在常温低湿（25℃、30%RH）和高温高湿（40℃、90%RH）条件下的吸湿平衡含水率和湿胀率均持续减小,阻湿率和体积抗胀率增大,尺寸稳定性明显提高。在200℃热处理后,三种木材均表现出明显增加的质量损失率和颜色变化,因此该三种木材较优的热处理工艺为180℃、3 h。 相似文献
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高温水热处理对马尾松木材物理力学性能的影响 总被引：1，自引：0，他引：1
《浙江林业科技》2017,(5)
以40年生马尾松Pinus massoniana木材为研究对象,采用不同水热处理温度(140,160,180,200℃)和不同时间(1,3,5 h)的热处理工艺,研究处理前后马尾松木材试件的主要物理力学性能变化。结果表明,试件的平衡含水率和失重率随水热处理温度升高和时间的延长呈逐渐降低的趋势;140℃处理的试件的气干密度、全干密度和基本密度随处理时间的增加变化不明显,但160,180,200℃处理下,随着处理温度升高和处理时间的延长,比处理前的试件均有所降低;马尾松木材的抗弯强度和抗弯弹性模量均随水热处理温度升高和时间的延长呈逐渐降低的趋势。实验显示,高温水热处理改性马尾松木材物理力学性能的较佳工艺为:处理温度160℃,处理时间3 h。 相似文献
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蒸汽介质热处理对毛白杨木材颜色的影响 总被引：2，自引：0，他引：2
以毛白杨木材为研究对象,采用蒸汽介质热处理方法在氧气含量低于2%的密闭容器中以温度170～230℃、时间1～5h的处理条件对其进行热处理。结果表明:随着处理温度的升高和处理时间的延长,色饱和度差ΔC*逐渐减小、色差ΔE*和色相差ΔH*逐渐增大,说明热处理后木材的颜色由原色逐步过渡到深褐色。方差分析和多重比较结果表明:热处理温度比热处理时间对毛白杨木材颜色变化的影响更为重要。此外,进一步得出了色差值与热处理温度、时间三者之间的回归模型。利用此特性,对一些浅色木材进行热处理,可赋予其凝重的颜色,同时还可增强其尺寸稳定性,从而提高其产品附加值,扩大应用领域。 相似文献
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热处理是提高木材尺寸稳定性的有效方法之一,目前热处理主要针对室外等较恶劣的用材环境,采用高温(200℃)处理。针对家具材装饰性要求高、使用环境变化较温和等特点,以家具常用材奥克榄木材为实验材料,研究真空(≤0.06 MPa)条件处理后奥克榄木材物理力学性能的变化,以确定适用于家具用材的真空低温热处理工艺。将奥克榄木材以0.06 MPa、不同温度(120,140,160,180,200℃)处理5 h,测定不同处理温度下木材的全干密度、湿胀率、干缩率、色差、抗弯弹性模量、抗弯强度、冲击韧性及硬度变化,并比较低温(120,140,160℃)和常规温度(180,200℃)处理及未处理奥克榄木材的物理力学性能。结果表明:物理性质方面,随温度升高,奥克榄材色加深,处理后奥克榄与未处理材相比,色差值ΔE为6.1～25.9;全干密度随处理温度呈波动状态变化,在200℃处理时达最低值,较未处理材下降30.9%;干缩率、湿胀率均明显下降,但在120℃升高至140℃、160℃升高至180℃时变化幅度较小。力学性能方面,随炭化温度升高,抗弯强度、抗弯弹性模量先增大后减小;冲击韧性降低,140℃之后变化幅度趋缓,200℃时降幅最大为52.42%;不同温度热处理后的端面硬度较未处理材均有所上升,径、弦变化不明显。与常规热处理和未处理处理材相比,真空低温热处理可改善木材的尺寸稳定性,降低炭化对于木材材色变化的影响,且不明显降低木材的力学性能。 相似文献
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采用不同热处理温度和时间对新西兰辐射松蓝变材和未蓝变材进行高温热处理,分析热处理温度、时间对试材颜色的影响,结果表明:随着处理温度的升高和处理时间的增长,试材的明度(L~*)逐渐降低,红绿色品指数(a~*)逐渐增大,黄蓝色品指数(b~*)逐渐减小(蓝变材b~*逐渐增大),总体综合色差(△E)增大。蓝变材和未蓝变材的颜色差异逐渐变小,为使蓝变色斑达到肉眼不容易识别的程度,最低的热处理条件为190℃,3h。多元回归分析和方差分析表明,在α=0.05水平上,热处理温度(x_1)和时间(x_2)两因素及其共同作用对L~*、a~*、b~*、△E的变化影响极为显著,其中温度对各颜色指标的影响比时间的影响更显著一些。 相似文献
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《林业机械与木工设备》2012,(4)
以过热蒸汽为传热介质和保护性气体,在热处理温度为160℃、180℃、200℃、220℃,热处理时间为2h、4h、6h、8h的条件下对圆盘豆木材进行高温热处理,研究圆盘豆木材在不同热处理条件下的力学性能变化规律。结果表明,随着热处理温度升高和热处理时间延长,圆盘豆热处理材抗弯强度降低;弹性模量在160℃时最高,然后降低;硬度的变化趋势不明显。红外光谱分析表明,热处理使木材中的半纤维素、纤维素、木素发生降解反应,导致木材力学强度降低。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
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Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and
also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the
amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter
bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K
was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed
significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week−1 for leaves and from 0.0225 to 0.0633 week−1 for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed
during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly
between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species
provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient
enrichment capacity and slower decomposition rates which would minimize leaching losses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(2):118-130
The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions. 相似文献
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Astra Zaluma Lauma Bruna Darta Klavina Natalija Burnevica Kristine Kenigsvalde Andis Lazdins Talis Gaitnieks 《Forest Pathology》2019,49(6)
Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
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Steven Maranz Amadou Niang Antoine Kalinganire Djeneba Konaté Bocary Kaya 《Agroforestry Systems》2008,72(3):231-239
Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional
data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral
contents and B1 and B2 vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising
germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B1 88 mg 100 g−1, B2 187 mg 100 g−1, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal
diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties
to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations. 相似文献
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《Wood material science & engineering》2013,8(2):76-84
Abstract Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists. 相似文献
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本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献